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Environmental Science: Water Research & Technology

Innovation for sustainable water

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Environmental Science: Water Research & Technology  is a Transformative Journal, and Plan S compliant

Impact factor: 5.0*

Time to first decision (all decisions): 14.0 days**

Time to first decision (peer reviewed only): 52.0 days***

Editor-in-Chief: Graham Gagnon

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Meet the team

Read our latest themed issues Urban stormwater management Data-intensive water systems management and operation Polymers in liquid formulations Drinking water oxidation and disinfection processes

Journal scope

Environmental Science: Water Research & Technology  seeks to showcase high quality research about fundamental science, innovative technologies, and management practices that promote sustainable water.

The journal aims to provide a comprehensive and relevant forum that unites the diverse communities and disciplines conducting water research relevant to engineered systems and the built environment. This includes fundamental science geared toward understanding physical, chemical, and biological phenomena in these systems as well as applied research focused on the development and optimisation of engineered treatment, management, and supply strategies.

Papers must report a significant advance in the theory, fundamental understanding, practice or application of water research, management, engineering or technology, within the following areas:

• Treatment and fate of chemical and microbial contaminants, including emerging contaminants
• Water distribution and wastewater collection
• Green infrastructure
• Stormwater management and treatment
• Potable reuse
• Residue management
• Sustainability analysis and design, including life cycle assessment studies
• Municipal and industrial wastewater treatment and resource recovery
• Drinking water treatment
• Water policy and regulation
• Applications of new water technologies* 
• Water, sanitation and hygiene (WASH)
• Water-energy nexus
• Simulation and data science applications to engineered water systems
• Environmental remediation of soil, sediment, and groundwater
• Impacts of climate change on engineered water systems

The journal places special focus on issues associated with water sustainability, as well as research that may lead to more secure, resilient and reliable water supplies. And it welcomes inter- and multidisciplinary work contributing to any of the above developments that are likely to be of interest to the broad community that the Journal addresses.

Manuscripts should be written to be accessible to scientists and engineers in all disciplines associated with the Journal.

All manuscripts must highlight their novel features and explain the significance of the work relative to related studies in their field as well as the likely impact on relevant water communities in the industry, government or academia.

*Please see the below expandable section for specific guidance regarding this area of our scope.

Measurement advances and analysis: these papers are encouraged and must clearly focus on the relevance of the work to engineered water systems and clearly explain the implications of the analysis or observations for sustainable water management. Papers dealing only with analysis, analytical method development or that simply report measured concentrations of target analytes (for example, occurrence and effluent concentrations of novel pollutant classes) will not be considered for publication.

Modeling: papers that lack appropriate validation through either experimental data or available and reliable datasets will not be considered for publication.

New materials or technologies for water treatment: emphasis must be placed on one of the following:

• Developing a fundamental understanding of the underlying mechanisms integral to technology performance
• Demonstrating how the practical application of the technology advances the field and improves upon existing treatment options

Papers in this area are strongly discouraged from focusing solely on technology demonstrations in model systems with model pollutant targets. Rather, they are encouraged to consider performance in complex (that is, environmentally relevant) systems and performance metrics (for example, efficacy across multiple pollutant targets, longevity, regeneration during application, and sustainability assessment) most relevant to real world application. 

Technology papers: we will not consider papers that focus solely on any of the following:

• Heavily focused on material synthesis and characterisation (such as nanomaterial catalysts)
• Consider only the removal of highly idealised targets (such as dyes)
• Work exclusively in clean laboratory systems
• Do not demonstrate innovation that advances the treatment field, or develops a technology without a clear and viable pathway to full scale implementation

Sustainability assessments: papers that cover, for example, life cycle assessment or life cycle cost analysis, of water-related technologies and systems must emphasize the fundamental insight into the factors governing technology or system performance. Papers are strongly discouraged from solely reporting absolute or comparative assessments of technologies/systems without uncovering novel insight or identifying critical barriers to sustainability.

These guidelines will be used by our Associate editors and reviewers to assess the significance of each submitted manuscript.

See who's on the team

Meet Environmental Science: Water Research & Technology  Editor-in-Chief and board members.

Editor-in-chief

Graham Gagnon , Dalhousie University, Canada

Associate editors

Sebastià Puig Broch , Universitat de Girona, Spain

Wenhai Chu , Tongji University, China

Ning Dai , University at Buffalo, USA

Lauren Stadler , Rice University, USA

Liu Ye , The University of Queensland, Australia

Editorial board members

Takahiro Fujioka , Nagasaki University, Japan

Karin Jönsson , Lund University, Sweden

Branko Kerkez , University of Michigan, USA

Jeonghwan Kim , Inha University, South Korea

Linda Lawton , Robert Gordon University, UK

Luca Vezzaro , Technical University of Denmark, Denmark

Eveline Volcke , Ghent University, Belgium

Federico Aulenta , National Research Council, Italy

Nicholas Ashbolt , University of Alberta, Canada

Tom Bond , University of Surrey, UK

Joby Boxall , The University of Sheffield, UK

Kartik Chandran , Columbia University in the City of New York, USA

Amy Childress , University of Southern California, USA

David Cwiertny , University of Iowa  

Joel Ducoste , North Carolina State University, USA

Marc Edwards , Virginia Tech, USA

Jingyun Fang , Sun Yat-sen University, China

Maria Jose Farre , Catalan Institute for Water Research, Spain

Yujie Feng , Harbin Institute of Technology, China

Kathrin Fenner , Swiss Federal Institute of Aquatic Science and Technology, Eawag, Switzerland 

Ramesh Goel , University of Utah, USA

Ola Gomaa , National Center for Radiation Research and Technology, Egypt

Chris Gordon , University of Ghana, Ghana

April Gu , Cornell University, USA

Jochen Hack , TU Darmstadt, Germany

Zhen "Jason" He , Washington University in St. Louis, USA

Xia Huang , Tsinghua University, China

Cynthia Joll , Curtin University, Australia

Tamar Kohn , École Polytechnique Fédérale de Lausanne, EPFL, Switzerland

Peng Liang , Tsinghua University, China

Irene Lo , Hong Kong University of Science and Technology, Hong Kong

Julie Minton , WateReuse Foundation, USA

Vincenzo Naddeo , University of Salerno, Italy

Indumathi M Nambi , Indian Institute of Technology Madras, India

Long Ngheim , University of Technology Sydney, Australia

Paige Novak , University of Minnesota, USA

Yong Sik Ok , Korea University, South Korea

Ligy Philip , Indian Institute of Technology Madras, India

Thalappil Pradeep , Indian Institute of Technology Madras, India

Zhiyong "Jason" Ren , Princeton University, USA

Peter Robertson , Queen's University Belfast, UK

Michael Templeton , Imperial College London, UK

Kai Udert , Swiss Federal Institute of Aquatic Science and Technology, Switzerland

Subramanyan Vasudevan , CSIR-Central Electrochemical Research Institute, India

Xin Wang , Nankai University, China

David Weissbrodt , TU Delft, The Netherlands

Krista Wigginton , University of Michigan, USA

Di Wu , Ghent University, South Korea

Defeng Xing , Harbin Institute of Technology, China

Jeyong Yoon , Seoul National University, South Korea

Neil Scriven , Executive Editor

Grace Thoburn , Deputy Editor

Nour Tanbouza , Development Editor

Claire Darby , Editorial Production Manager, ORCID 0000-0003-3059-6020

Emma Carlisle,  Publishing Editor

Hannah Hamilton , Publishing Editor

Ephraim Otumudia , Publishing Editor

Irene Sanchez Molina Santos , Publishing Editor

Michael Spencelayh , Publishing Editor

Callum Woof , Publishing Editor

Lauren Yarrow-Wright , Publishing Editor

Kate Bandoo , Editorial Assistant

Linda Warncke , Publishing Assistant

Sam Keltie , Publisher, Journals, ORCID 0000-0002-9369-8414

Article types

Environmental Science: Water Research & Technology publishes:

Communications

Full papers, perspectives, critical reviews, frontier reviews, tutorial reviews, comments and replies.

Reviews & Perspectives are normally invited, however suggestions for timely Reviews are very welcome. Interested authors should contact the Editorial Office at [email protected] with an abstract or brief synopsis of their intended Review.

These must report preliminary research findings that are novel and original, of immediate interest and are likely to have a high impact on the Environmental Science: Water Research & Technology community. Authors must provide a short paragraph explaining why their work justifies rapid publication as a communication.

Original research papers on any of the subjects outlined in the scope section and related areas are encouraged and welcomed. All papers should give due attention to overcoming limitations and to underlying principles. All contributions will be judged on the following four criteria. 1. Novelty and insight 2. Quality of scientific work and content 3. Clarity of objectives and aims of the work 4. Appropriateness of length to content of new science

These may be articles providing a personal view of part of one discipline associated with Environmental Science: Water Research & Technology or a philosophical look at a topic of relevance. Alternatively, Perspectives may be historical articles covering a particular subject area or the development of particular legislation, technologies, methodologies or other subjects within the scope of the journal.

Critical reviews must be a critical evaluation of the existing state of knowledge on a particular facet of water research or water technologies as they affect environmental science. They should be timely and provide insights based on existing literature. They should be of general interest to the journal's wide readership.

All Critical reviews undergo a rigorous and full peer review procedure, in the same way as regular research papers. Authors are encouraged to identify areas in the field where further developments are imminent or of urgent need, and any areas that may be of significance to the community in general. Critical reviews should not contain any unpublished original research.

These are shorter, more focused versions of Critical reviews on a well-defined, specific topic area covering approximately the last two-three years. Articles should cover only the most interesting/significant developments in that specific subject area.

The article should be highly critical and selective in referencing published work. One or two paragraphs of speculation about possible future developments may also be appropriate in the conclusion section.

Frontier reviews may also cover techniques/technologies that are too new for a Critical review or may address a subset of technologies available for a given area of research within the journal scope.

Frontier reviews should not contain unpublished original research.

Tutorial reviews should provide an introduction and overview of an important topic of relevance to the journal readership. The topic should be of relevance to both researchers who are new to the field as well as experts and provide a good introduction to the development of a subject, its current state and indications of future directions the field is expected to take. Tutorial reviews should not contain unpublished original research.

Comments and Replies are a medium for the discussion and exchange of scientific opinions between authors and readers concerning material published in Environmental Science: Water Research & Technology.

For publication, a Comment should present an alternative analysis of and/or new insight into the previously published material. Any Reply should further the discussion presented in the original article and the Comment. Comments and Replies that contain any form of personal attack are not suitable for publication. 

Comments that are acceptable for publication will be forwarded to the authors of the work being discussed, and these authors will be given the opportunity to submit a Reply. The Comment and Reply will both be subject to rigorous peer review in consultation with the journal’s Editorial Board where appropriate. The Comment and Reply will be published together.

Journal specific guidelines

See a summary of ESWRT’s journal-specific guidelines . More details are also provided below.

Use of RSC template

There are no submission specifics regarding formatting; use of Royal Society of Chemistry template is not required. Bibliographies should be formatted according to the following Endnote and Zotero style files to include the cited article’s title.

Authors are encouraged to include line numbering in submitted manuscripts. Although there is no page limit for Full papers, appropriateness of length to content of new science will be taken into consideration by reviewers.

Water Impact Statement

All submitted manuscripts must include a 'Water Impact Statement' (60 words maximum; approximately three sentences) that clearly states in plain language the broad-scale implications and real-world relevance of the work. True potential for immediate real-world impact may be subject to further study, but the pathways towards achieving that impact in future should at least be envisioned and explained.

Read Professor Michael Templeton’s Editorial Perspective “ Achieving real-world impact ” for further discussion on expectations for the journal.

Authors should use this statement to show that they have given serious consideration as to how their work addresses current challenges related to water sustainability in a realistic sense. This statement will be carefully considered by the editors and the reviewers and will help ascertain the relevance of the article for a broad audience. Absence of potential for real-world impact is reason for rejection. If the manuscript is accepted this statement will be included in the published article. Please note that manuscripts without this statement will not be peer-reviewed.

Double-anonymised peer review option

Environmental Science: Water Research & Technology is now offering authors the option of double-anonymised peer review. Both single- and double-anonymised peer review are now available to authors.

• Single-anonymised peer review - where reviewers are anonymous but author names and affiliations are known to reviewers. (This is the traditional peer review model used on Environmental Science: Water Research & Technology)
• Double-anonymised peer review - where authors and reviewers' identities are concealed from each other.

Guidelines for authors and reviewers can be found  here

Organisation of material

An article should have a short, straightforward title directed at the general reader. Lengthy systematic names and complicated and numerous chemical formulae should therefore be avoided where possible. The use of non-standard abbreviations and symbols in a title is not encouraged. Please bear in mind that readers increasingly use search engines to find literature; recognisable, key words should be included in the title where possible, to maximise the impact and discoverability of your work. Brevity in a title, though desirable, should be balanced against its accuracy and usefulness.

The use of series titles and part numbers in titles of papers is discouraged. Instead these can be included as a footnote to the first page together with a reference (reference 1) to the preceding part. When the preceding part has been submitted to a Royal Society of Chemistry journal but is not yet published, the paper reference number should be given.

Author names

Full names for all the authors of an article should be given. To give due acknowledgement to all workers contributing to the work, those who have contributed significantly to the research should be listed as co-authors. Authors who contributed equally can be noted with a Footnote and referenced with a symbol.

On submission of the manuscript, the corresponding author attests to the fact that those named as co-authors have agreed to its submission for publication and accepts the responsibility for having properly included all (and only) co- authors. If there are more than 10 co-authors on the manuscript, the corresponding author should provide a statement to specify the contribution of each co-author. The corresponding author signs a copyright licence on behalf of all the authors.

Table of contents entry

This entry should include a colour image (no larger than 8 cm wide x 4 cm high), and 20-30 words of text that highlight the novel aspects of your work. Graphics should be as clear as possible; simple schematic diagrams or reaction schemes are preferred to ORTEP- style crystal structure depictions and complicated graphs, for example. The graphic used in the table of contents entry need not necessarily appear in the article itself. Authors should bear in mind the final size of any lettering on the graphic. For examples, please see the online version of the journal.

Every paper must be accompanied by a summary (50-250 words) setting out briefly and clearly the main objects and results of the work; it should give the reader a clear idea of what has been achieved. The summary should be essentially independent of the main text; however, names, partial names or linear formulae of compounds may be accompanied by the numbers referring to the corresponding displayed formulae in the body of the text.

Please bear in mind that readers increasingly use search engines to find literature; recognisable, searchable terms and key words should be included in the abstract to enable readers to more effectively find your paper. The abstract should aim to address the following questions.

• What is the problem or research question being addressed?
• What experimental approach was used to address the problem or question?
• What key data and results were obtained?
• What conclusions can be drawn from the experimental results?
• What are the broader implications for the study with respect to water sustainability?

Water Impact Statement 

Authors must provide a 'Water Impact Statement' (60 words maximum) that clearly highlights the broad-scale implications and real-world relevance of the work. This statement should be different from the abstract and must set the work in broader context with regards to water sustainability. True potential for immediate real-world impact may be subject to further study, but the pathways towards achieving that impact in future should at least be envisioned and explained in this statement.

When composing your Water Impact Statement, please consider the following points:

1.What is the problem? 2.Why is it important? 3.How does this translate to real-world applications/scenarios? 4.How can this be generalised?  5.Why is this work significant for ensuring sustainable water resources?  

This statement will be seen by the reviewers and will help ascertain the relevance of the article for a broad but technical audience. Authors should use it to show that they have given serious consideration to the impact of their presented study. Absence of potential for real-world impact is reason for rejection. If the paper is accepted this statement will also be published. Please note that papers cannot be peer-reviewed without this statement.

Introduction

This should give clearly and briefly, with relevant references, both the nature of the problem under investigation and its background.

Descriptions of methods and/or experiments should be given in detail sufficient to enable experienced experimental workers to repeat them. Standard techniques and methods used throughout the work should be stated at the beginning of the section. Apparatus should be described only if it is non-standard; commercially available instruments are referred to by their stock numbers (for example, Perkin-Elmer 457 or Varian HA-100 spectrometers). The accuracy of primary measurements should be stated. In general there is no need to report unsuccessful experiments. Authors are encouraged to make use of electronic supplementary information (ESI) for lengthy synthetic sections. Any unusual hazards inherent in the use of chemicals, procedures or equipment in the investigation should be clearly identified. In cases where a study involves the use of live animals or human subjects, the author should include a statement that all experiments were performed in compliance with the relevant laws and institutional guidelines, and also state the institutional committee(s) that have approved the experiments. They should also include a statement that informed consent was obtained for any experimentation with human subjects. Referees may be asked to comment specifically on any cases in which concerns arise.

Results and discussion

It is usual for the results to be presented first, followed by a discussion of their significance. Only strictly relevant results should be presented and figures, tables, and equations should be used for purposes of clarity and brevity. The use of flow diagrams and reaction schemes is encouraged. Data must not be reproduced in more than one form - for example, in both figures and tables, without good reason.

This is for interpretation and to highlight the novelty and significance of the work. Authors are encouraged to discuss the real world relevance of the work reported and how it promotes water sustainability. The conclusions should not summarise information already present in the text or abstract.

Acknowledgements

Contributors other than co-authors may be acknowledged in a separate paragraph at the end of the paper; acknowledgements should be as brief as possible. All sources of funding should be declared.

Bibliographic references and notes

These should be listed at the end of the manuscript in numerical order. We encourage the citation of primary research over review articles, where appropriate, in order to give credit to those who first reported a finding. Find out more about our commitments to the principles of  San Francisco Declaration on Research Assessment (DORA).

Bibliographic details should be cited in the order: year, volume , page, and must include the article title. For example: Lukas Mustajärvi, Ann-Kristin Eriksson-Wiklund, Elena Gorokhova, Annika Jahnke and Anna Sobek, Transferring mixtures of chemicals from sediment to a bioassay using silicone-based passive sampling and dosing, Environ. Sci.: Processes Impacts , 2017, 19 , 1404-1413. See  Endnote style files . For Zotero, please use the Royal Society of Chemistry (with titles) template.

Bibliographic reference to the source of statements in the text is made by use of superior numerals at the appropriate place (for example, Wittig3). The reference numbers should be cited in the correct sequence through the text (including those in tables and figure captions, numbered according to where the table or figure is designated to appear).  Please do not use Harvard style for references.

The references themselves are given at the end of the final printed text along with any notes. The names and initials of all authors are always given in the reference; they must not be replaced by the phrase et al . This does not prevent some, or all, of the names being mentioned at their first citation in the cursive text; initials are not necessary in the text. Notes or footnotes may be used to present material that, if included in the body of the text, would disrupt the flow of the argument but which is, nevertheless, of importance in qualifying or amplifying the textual material. Footnotes are referred to with the following symbols: †, ‡, §, ¶, ║etc.

Alternatively the information may be included as Notes (end-notes) to appear in the Notes/references section of the manuscript. Notes should be numbered using the same numbering system as the bibliographic references.

Journals The style of journal abbreviations to be used in RSC publications is that defined in Chemical Abstracts Service Source Index (CASSI) (http://www.cas.org/expertise/cascontent/caplus/corejournals.html).

Bibliographic details should be cited in the order: year, volume , page. Where page numbers are not yet known, articles should be cited by DOI (Digital Object Identifier) - for example, T. J. Hebden, R. R. Schrock, M. K. Takase and P. Müller, Chem. Commun ., 2012, DOI: 10.1039/C2CC17634C.

Books J. Barker, in Catalyst Deactivation , ed. B. Delmon and C. Froment, Elsevier, Amsterdam, 2nd edn., 1987, vol. 1, ch. 4, pp. 253-255.

Patents Br. Pat ., 357 450, 1986. US Pat ., 1 171 230, 1990.

Reports and bulletins, etc R. A. Allen, D. B. Smith and J. E. Hiscott, Radioisotope Data , UKAEA Research Group Report AERE-R 2938, H.M.S.O., London, 1961.

Material presented at meetings H. C. Freeman, Proceedings of the 21st International Conference on Coordination Chemistry, Toulouse, 1980.

Theses A. D. Mount, Ph.D. Thesis, University of London, 1977.

Reference to unpublished material For material presented at a meeting, congress or before a Society, etc., but not published, the following form is used:  A. R. Jones, presented in part at the 28th Congress of the International Union of Pure and Applied Chemistry, Vancouver, August, 1981.

For material accepted for publication, but not yet published, the following forms are used.

• A. R. Jones, Dalton Trans. , 2003, DOI: 10.1039/manuscript number, for RSC journals 
• A. R. Jones, Angew. Chem ., in press, for non-RSC journals

If DOI numbers are known these should be cited in the form recommended by the publisher.

For material submitted for publication but not yet accepted the following form is used.

• A. R. Jones, Angew. Chem ., submitted.

For personal communications the following is used.

• G. B. Ball, personal communication.

If material is to be published but has yet to be submitted the following form is used.

• G. B. Ball, unpublished work.

Reference to unpublished work should not be made without the permission of those by whom the work was performed.

Software F James,  AIM2000, version 1.0, University of Applied Sciences, Bielefeld,  Germany, 2000. T Bellander, M Lewne and B Brunekreef, GAUSSIAN 3 (Revision B.05), Gaussian Inc., Pittsburgh, PA, 2003.

Online resources (including databases) Please note the most important information to include is the URL and the data accessed.

• The Merck Index Online, http://www.rsc.org/Merck-lndex/monograph/mono1500000841, (accessed October 2013).
• ChemSpider, http://www.chemspider.com/Chemicai-Structure.1906.html, (accessed June 2011).

arXiv references V. Krstic and M. Glerup, 2006, arXiv:cond-mat/0601513.

Figures & schemes

Preparation of graphics.

Artwork should be submitted at its final size so that reduction is not required. The appearance of graphics is the responsibility of the author.

• Graphics should fit within either single column (8.3 cm) or double column (17.1 cm) width, and must be no longer than 23.3 cm.
• Graphical abstracts should be no larger than 8 x 4 cm.
• Schemes and structures should be drawn to make best use of single and double column widths.

Colour figures

Colour figure reproduction is provided free of charge both online and in print.

Journal covers

Authors who wish to have their artwork featured on a journal cover should contact the editorial office of the journal to which the article is being submitted. A contribution to the additional production costs will be requested.

Use of such artwork is at the editor's discretion; the editor's decision is final. Examples of previous journal covers can be viewed via the journal homepage.

Electronic supplementary information

The journal's electronic supplementary information (ESI) service is a free facility that enables authors to enhance and increase the impact of their articles. Authors are encouraged to make the most of the benefits of publishing supplementary information in electronic form. Such data can take full advantage of the electronic medium, allowing use of 3D molecular models and movies. Authors can also improve the readability of their articles by placing appropriate material, such as repetitive experimental details and bulky data, as ESI. All information published as ESI is also fully archived. When preparing their ESI data files, authors should keep in mind the following points.

• Supplementary data is peer-reviewed, and should therefore be included with the original submission.
• ESI files are published 'as is'; editorial staff will not usually edit the data for style or content.
• Data is useful only if readers can access it; use common file formats.
• Large files may prove difficult for users to download and access.

Text and graphics

The preferred format for ESI comprising text and graphics is Microsoft Word. Publishing staff will convert Word files to PDF before publication, as this format can be accessed easily and reliably on most computing platforms using the freely available Adobe Acrobat Reader. If other formats are submitted they will also usually be converted to PDF files prior to publication.

Multimedia files

We welcome submission of multimedia files (including videos and animations) alongside articles for publication. Videos are an excellent medium to present elements of your work that can be difficult to communicate only in words. Please note that any videos of general interest are shared with the wider community via the RSC Journals YouTube channel. Please notify the editorial team if you prefer for your video(s) not to be uploaded to YouTube. If you submit a multimedia file alongside your paper, please refer to it within your paper to draw it to the reader’s attention. Also please see the section on submitting multimedia files

Format Acceptable formats for video or animation clips are listed below.

Please minimise file sizes where you can, by considering the following points.

• The recommended maximum frame size is 640 x 480 pixels.
• Our recommended maximum file size is 5 Mb.
• Many packages output 30 frames per second (fps) as standard, but it's possible to specify a lower frame rate; this may not noticeably affect the quality of your video but will reduce the file size.
• Use a 256 colour palette, if that is suitable for the presentation of the material.

Please consider the use of lower specifications for all these points if the material can still be represented clearly.

If your video is very short (that is, several seconds long) then it is recommended that you loop it and repeat a few times to provide a more detailed view.

Submitting multimedia files Upload your video online, together with your manuscript under the category 'electronic supplementary material' and please supply the following.

• A clear file name for your video.
• A short descriptive title for the video, which can be used when uploading the video onto a streaming channel.
• A video legend of approximately 30 words long; this caption must be provided to aid discoverability.
• Five to 10 keywords that can be used to tag the video; the more accurate the tags are the better discoverability videos will have.

Copies of any relevant 'in press' references

Manuscripts should be submitted with copies of any ‘in press’ articles referenced.

Open access publishing options

Environmental Science: Water Research & Technology  is a hybrid (transformative) journal and gives authors the choice of publishing their research either via the traditional subscription-based model or instead by choosing our gold open access option.  Find out more about our Transformative Journals. which are Plan S compliant .

Gold open access

For authors who want to publish their article gold open access , Environmental Science: Water Research & Technology  charges an article processing charge (APC) of £2,750 (+ any applicable tax). Our APC is all-inclusive and makes your article freely available online immediately, permanently, and includes your choice of Creative Commons licence (CC BY or CC BY-NC) at no extra cost. It is not a submission charge, so you only pay if your article is accepted for publication.

Learn more about publishing open access .

Read & Publish

If your institution has a Read & Publish agreement in place with the Royal Society of Chemistry, APCs for gold open access publishing in Environmental Science: Water Research & Technology  may already be covered.

Use our journal finder to check if your institution has an open access agreement with us.

Please use your official institutional email address to submit your manuscript and check you are assigned as the corresponding author; this helps us to identify if you are eligible for Read & Publish or other APC discounts.

Traditional subscription model

Authors can also publish in Environmental Science: Water Research & Technology via the traditional subscription model without needing to pay an APC. Articles published via this route are available to institutions and individuals who subscribe to the journal. Our standard licence allows you to make the accepted manuscript of your article freely available after a 12-month embargo period. This is known as the green route to open access.

Learn more about green open access .

Subscription information

  Online only 2024:  ISSN: 2053-1419, £2,031 / $3,352

*2022 Journal Citation Reports (Clarivate Analytics, 2023)

**The median time from submission to first decision including manuscripts rejected without peer review from the previous calendar year

***The median time from submission to first decision for peer-reviewed manuscripts from the previous calendar year

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Water, Hydration and Health

Barry m. popkin.

Department of Nutrition, University of North Carolina, Chapel Hill, NC

Kristen E. D’Anci

Department of Psychology, Tufts University, Medford, MA

Irwin H. Rosenberg

Nutrition and Neurocognition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA

This review attempts to provide some sense of our current knowledge of water including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, the effects of variation in water intake on health and energy intake, weight, and human performance and functioning. Water represents a critical nutrient whose absence will be lethal within days. Water’s importance for prevention of nutrition-related noncommunicable diseases has emerged more recently because of the shift toward large proportions of fluids coming from caloric beverages. Nevertheless, there are major gaps in knowledge related to measurement of total fluid intake, hydration status at the population level, and few longer-term systematic interventions and no published random-controlled longer-term trials. We suggest some ways to examine water requirements as a means to encouraging more dialogue on this important topic.

I. INTRODUCTION

Water is essential for life. From the time that primeval species ventured from the oceans to live on land, a major key to survival has been prevention of dehydration. The critical adaptations cross an array of species, including man. Without water, humans can survive only for days. Water comprises from 75% body weight in infants to 55% in elderly and is essential for cellular homeostasis and life. 1 Nevertheless there are many unanswered questions about this most essential component of our body and our diet. This review attempts to provide some sense of our current knowledge of water including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, the effects of variation in water intake on health and energy intake, weight, and human performance and functioning.

Recent statements on water requirements have been based on retrospective recall of water intake from food and beverages among healthy non-institutionalized individuals. We provide examples of water intake assessment in populations to clarify the need for experimental studies. Beyond these circumstances of dehydration, we do not truly understand how hydration affects health and well-being, even the impact of water intakes on chronic diseases. Recently, Jéquier and Constant addressed this question based on the human physiology. 2 We need to know more about the extent that water intake might be important for disease prevention and health promotion.

As we note later, few countries have developed water requirements and those that do base them on weak population-level measures of water intake and urine osmolality. 3 , 4 The European Food Safety Authority (EFSA) has been recently asked to revise existing recommended intakes of essential substances with a physiological effect including water since this nutrient is essential for life and health. 5

The US Dietary Recommendations for water are based on median water intakes with no use of measurements of dehydration status of the population to assist. One-time collection of blood samples for the analysis of serum osmolality has been used by NHANES. At the population level we have no accepted method of assessing hydration status and one measure some scholars use, hypertonicity, is not even linked with hydration in the same direction for all age groups. 6 Urine indices are used often but reflect recent volume of fluid consumed rather than a state of hydration. 7 Many scholars use urine osmolality to measure recent hydration status. 8 – 12 Deuterium dilution techniques (isotopic dilution with D2O or deuterium oxide) allows measurement of total body water but not water balance status. 13 Currently we feel there are no adequate biomarkers to measure hydration status at the population level.

When we speak of water we are essentially focusing first and foremost on all types of water, be they soft or hard, spring or well, carbonated or distilled water. Furthermore we get water not only directly as a beverage but from food and to a very small extent also from oxidation of macronutrients (metabolic water). The proportion of water that comes from beverages and food varies with the proportion of fruits and vegetables in the diet. We present the ranges of water in various foods ( Table 1 ). In the United States it is estimated that about 22% of water comes from our food intake while it would be much higher in European countries, particularly a country like Greece with its higher intake of fruits and vegetables or South Korea. 3 , 14 , 15 The only in-depth study of water use and water intrinsic to food in the US found a 20.7% contribution from food water; 16 , 17 however as we show later, this research was dependent on poor overall assessment of water intake.

The Water Content Range for Selected Foods

Source: The USDA National Nutrient Database for Standard Reference, Release 21 provided in Altman. 127

This review considers water requirements in the context of recent efforts to assess water intake in US populations. Relationship of water and calorie intake is explored both for insights into the possible displacement of calories from sweetened beverages by water and also to examine the possibility that water requirements would be better expressed in relation to calorie/energy requirements with the dependence of the latter on age, size, gender, and physical activity level. We review current understanding of the exquisitely complex and sensitive system which protects land animals against dehydration and comment on the complications of acute and chronic dehydration in man against which a better expression of water requirements might complement the physiological control of thirst. Indeed, the fine intrinsic regulation of hydration and water intake in individuals mitigates against prevalent underhydration in populations and effects on function and disease.

Regulation of fluid intake

To prevent dehydration reptiles, birds, vertebrates, and all land animals have evolved an exquisitely sensitive network of physiological controls to maintain body water and fluid intake by thirst. Humans may drink for various reasons, particularly for hedonic ones but most of drinking is due to water deficiency which triggers the so called regulatory or physiological thirst. The mechanism of thirst is quite well understood today and the reason non-regulatory drinking is often encountered is related to the large capacity of kidneys to rapidly eliminate excesses of water or reduce urine secretion to temporarily economize on water. 1 But this excretory process can only postpone the necessity for drinking or for stopping drinking an excess of water. Non regulatory drinking is often confusing, particularly in wealthy societies facing highly palatable drinks or fluids that contain other substance that the drinker seeks. The most common of them are sweeteners or alcohol to which water is served as a vehicle. Drinking these beverages isn’t due to excessive thirst or hyperdipsia as it can be shown by offering pure water instead and finding out that the same drinker is in fact hypodipsic (Characterized by abnormally diminished thirst). 1

Fluid balance of the two compartments

Maintaining a constant water and mineral balance requires the coordination of sensitive detectors at different sites in the body linked by neural pathways with integrative centers in the brain that process this information. These centers are also sensitive to humoral factors (neurohormones) produced for the adjustment of diuresis, natriuresis and blood pressure (angiotensin mineralocorticoids, vasopressin, atrial natriuretic factor). Instructions from the integrative centers to the “executive organs” (kidney, sweat glands and salivary glands) and to the part of the brain responsible for corrective actions such as drinking are conveyed by certain nerves in addition to the above mentioned substances. 1

Most of the components of fluid balance are controlled by homeostatic mechanisms responding to the state of body water. These mechanisms are sensitive and precise, and are activated with deficits or excesses of water amounting to only a few hundred milliliters. A water deficit produces an increase in the ionic concentration of the extracellular compartment, which takes water from the intracellular compartment causing cells to shrink. This shrinkage is detected by two types of brain sensors, one controlling drinking and the other controlling the excretion of urine by sending a message to the kidneys mainly via the antidiuretic hormone vasopressin to produce a smaller volume of more concentrated urine. 18 When the body contains an excess of water, the reverse processes occur: the lower ionic concentration of body fluids allows more water to reach the intracellular compartment. The cells imbibe, drinking is inhibited and the kidneys excrete more water.

The kidneys thus play a key role in regulating fluid balance. As discussed later, the kidneys function more efficiently in the presence of an abundant water supply. If the kidneys economize on water, producing a more concentrated urine, these is a greater cost in energy and more wear on their tissues. This is especially likely to occur when the kidneys are under stress, for example when the diet contains excessive amounts of salt or toxic substances that need to be eliminated. Consequently, drinking enough water helps protect this vital organ.

Regulatory drinking

Most drinking obeys signals of water deficit. Apart from urinary excretion, the other main fluid regulatory process is drinking, mediated through the sensation of thirst. There are two distinct mechanisms of physiological thirst: the intracellular and the extracellular mechanisms. When water alone is lost, ionic concentration increases. As a result, the intracellular space yields some of its water to the extracellular compartment. One again, the resulting shrinkage of cells is detected by brain receptors that send hormonal messages to induce drinking. This association with receptors that govern extracellular volume is therefore accompanied by an enhancement of salt appetite. Thus, people who have been sweating copiously prefer drinks that are relatively rich in Na+ salts rather than pure water. As previously mentioned, it is always important to supplement drinks with additional salt when excessive sweating is experienced.

The brain’s decision to start or stop drinking and to choose the appropriate drink is made before the ingested fluid can reach the intra- and extracellular compartments. The taste buds in the mouth send messages to the brain about the nature, and especially the salt of the ingested fluid, and neuronal responses are triggered as if the incoming water had already reached the bloodstream. These are the so-called anticipatory reflexes: they cannot be entirely “cephalic reflexes” because they arise from the gut as well as the mouth. 1

The anterior hypothalamus and pre-optic area are equipped with osmo-receptors related to drinking. Neurons in these regions show enhanced firing when the inner milieu gets hyperosmotic. Their firing decreases when water is loaded in the carotid artery that irrigates the neurons. It is remarkable that the same decrease in firing in the same neurons takes place when the water load is applied on the tongue instead of being injected in the carotid artery. This anticipatory drop in firing is due to a mediation neural pathways departing from the mouth and by converging on to the neurons which simultaneously sense of the inner milieu (blood).

Non-regulatory drinking

Although everyone experiences thirst from time to time, it plays little day-to-day role in the control of water intake in healthy people living in temperate climates. We generally consume fluids not to quench our thirst, but as components of everyday foods (e.g. soup, milk), as beverages used as mild stimulants (tea, coffee) and for pure pleasure. As common example is alcohol consumption which can increase individual pleasure and stimulate social interaction. Drinks are also consumed for their energy content, as in soft drinks and milk, and are used in warm weather for cooling and in cold weather for warming. Such drinking seems also to be mediated through the taste buds, which communicate with the brain in a kind of “reward system” the mechanisms of which are just beginning to be understood. This bias in the way human beings rehydrate themselves may be advantageous because it allows water losses to be replaced before thirst-producing dehydration takes place. Unfortunately, this bias also carries some disadvantages. Drinking fluids other than water can contribute to an intake of caloric nutrients in excess of requirements, or in alcohol consumption that in some people may insidiously bring about dependence. For example, total fluid intake increased from 79 fluid ounces in 1989 to 100 fluid ounces in 2002 among US adults, all from caloric beverages. 19

Effects of aging on fluid intake regulation

The thirst and fluid ingestion responses of older persons to a number of stimuli have been compared to those seen in younger persons. 20 Following water deprivation older persons are less thirsty and drink less fluid compared to younger persons. 21 , 22 The decrease in fluid consumption is predominantly due to a decrease in thirst as the relationship between thirst and fluid intake is the same in young and old persons. Older persons drink insufficient water following fluid deprivation to replenish their body water deficit. 23 When dehydrated older persons are offered a highly palatable selection of drinks, this also failed to result in an increased fluid intake. 23 The effects of increased thirst in response to an osmotic load have yielded variable responses with one group reporting reduced osmotic thirst in older individuals 24 and one failing to find a difference. In a third study, young individuals ingested almost twice as much fluid as old persons, despite the older subjects having a much higher serum osmolality. 25

Overall these studies support small changes in the regulation of thirst and fluid intake with aging. Defects in both osmoreceptors and baroreceptors appear to exist as well as changes in the central regulatory mechanisms mediated by opioid receptors. 26 Because of their low water reserves, it may be prudent for the elderly to learn to drink regularly when not thirsty and to moderately increase their salt intake when they sweat. Better education on these principles may help prevent sudden hypotension and stroke or abnormal fatigue can lead to a vicious circle and eventually hospitalization.

Thermoregulation

Hydration status is critical to the body’s process of temperature control. Body water loss through sweat is an important cooling mechanism in hot climates and in physical activity. Sweat production is dependent upon environmental temperature and humidity, activity levels, and type of clothing worn. Water losses via skin (both insensible perspiration and sweating) can range from 0.3 L/h in sedentary conditions to 2.0 L/h in high activity in the heat and intake requirements range from 2.5 to just over 3 L/d in adults under normal conditions, and can reach 6 L/d with high extremes of heat and activity. 27 , 28 Evaporation of sweat from the body results in cooling of the skin. However, if sweat loss is not compensated for with fluid intake, especially during vigorous physical activity, a hypohydrated state can occur with concomitant increases in core body temperature. Hypohydration from sweating results in a loss in electrolytes, as well as a reduction in plasma volume, and can lead to increased plasma osmolality. During this state of reduced plasma volume and increased plasma osmolality, sweat output becomes insufficient to offset increases in core temperature. When fluids are given to maintain euhydration, sweating remains an effective compensation for increased core temperatures. With repeated exposure to hot environments, the body adapts to heat stress, and cardiac output and stroke volume return to normal, sodium loss is conserved, and the risk for heat-stress related illness is reduced. 29 Increasing water intake during this process of heat acclimatization will not shorten the time needed to adapt to the heat, but mild dehydration during this time may be of concern and is associated with elevations in cortisol, increased sweating, and electrolyte imbalances. 29

Children and the elderly have differing responses to ambient temperature and different thermoregulatory concerns than healthy adults. Children in warm climates may be more susceptible to heat illness than adults due to greater surface area to body mass ratio, lower rate of sweating, and slower rate of acclimatization to the heat. 30 , 31 Children may respond to hypohydration during activity with a higher relative increase in core temperature than adults do, 32 and sweat less, thus losing some of the benefits of evaporative cooling. However, it has been argued that children can dissipate a greater proportion of body heat via dry heat loss, and the concomitant lack of sweating provides a beneficial means of conserving water under heat stress. 30 Elders, in response to cold stress, show impairments in thermoregulatory vasoconstriction and body water is shunted from plasma into the interstitial and intracellular compartments. 33 , 34 With respect to heat stress, water lost through sweating decreases water content of plasma, and the elderly are less able to compensate for increased blood viscosity. 33 Not only do they have a physiological hypodipsia, but this can be exaggerated by central nervous system disease 35 and by dementia 36 . In addition, illness and limitations in activities of daily living can further limit fluid intake. Coupled with reduced fluid intake, with advancing age there is a decrease in total body water. Older individuals have impaired renal fluid conservation mechanisms and, as noted above, have impaired responses to heat and cold stress 33 , 34 . All of these factors contribute to an increased risk of hypohydration and dehydration in the elderly.

II. PHYSIOLOGICAL EFFECTS OF DEHYDRATION

In this section, the role of water in health is generally characterized in terms of deviations from an ideal hydrated state, generally in comparison to dehydration. The concept of dehydration encompasses both the process of losing body water and also the state of dehydration. Much of the research on water and physical or mental functioning compares a euhydrated state, usually achieved by provision of water sufficient to overcome water loss, to a dehydrated state, which is achieved via withholding of fluids over time and during periods of heat stress or high activity. In general, provision of water is beneficial in those with a water deficit, but little research supports the notion that additional water in adequately hydrated individuals confers any benefit.

Physical performance

The role of water and hydration in physical activity, particularly in athletes and in the military, has been of considerable interest and is well-described in the scientific literature. 37 – 39 During challenging athletic events, it is not uncommon for athletes to lose 6–10% of body weight in sweat loss, thus leading to dehydration if fluids have not been replenished. However, decrements in physical performance in athletes have been observed under much lower levels of dehydration, as little as 2%. 38 Under relatively mild levels of dehydration, individuals engaging in rigorous physical activity will experience decrements in performance related to reduced endurance, increased fatigue, altered thermoregulatory capability, reduced motivation, and increased perceived effort. 40 , 41 Rehydration can reverse these deficits, and also reduce oxidative stress induced by exercise and dehydration. 42 Hypohydration appears to have a more significant impact on high-intensity and endurance activity such as tennis 43 and long-distance running 44 than on anaerobic activities 45 such as weight lifting or on shorter-duration activities, such as rowing. 46

During exercise, individuals may not hydrate adequately when allowed to drink according to thirst. 32 After periods of physical exertion, voluntary fluid intake may be inadequate to offset fluid deficits. 1 Thus, mild to moderate dehydration can therefore persist for some hours after the conclusion of physical activity. Research in athletes suggests that, principally at the beginning of the season, they are at particular risk for dehydration due to lack of acclimatization to weather conditions or suddenly increased activity levels. 47 , 48 A number of studies show that performance in temperate and hot climates is affected to a greater degree than performance in cold temperatures. 41 , 49 , 50 Exercise in hot conditions with inadequate fluid replacement is associated with hyperthermia, reduced stroke volume and cardiac output, decreases in blood pressure, and reduced blood flow to muscle. 51

During exercise, children may be at greater risk for voluntary dehydration. Children may not recognize the need to replace lost fluids, and both children as well as coaches need specific guidelines for fluid intake. 52 Additionally, children may require longer acclimation to increases in environmental temperature than do adults. 30 , 31 Recommendations are for child athletes or children in hot climates to begin athletic activities in a well-hydrated state and to drink fluids over and above the thirst threshold.

Cognitive performance

Water, or its lack (dehydration), can influence cognition. Mild levels of dehydration can produce disruptions in mood and cognitive functioning. This may be of special concern in the very young, very old, those in hot climates, and those engaging in vigorous exercise. Mild dehydration produces alterations in a number of important aspects of cognitive function such as concentration, alertness and short-term memory in children (10–12 y), 32 young adults (18–25y) 53 – 56 and in the oldest adults, 50–82y. 57 As with physical functioning, mild to moderate levels of dehydration can impair performance on tasks such as short-term memory, perceptual discrimination, arithmetic ability, visuomotor tracking, and psychomotor skills. 53 – 56 However, mild dehydration does not appear to alter cognitive functioning in a consistent manner. 53 , 54 , 56 , 58 In some cases, cognitive performance was not significantly affected in ranges from 2–2.6% dehydration. 56 , 58 Comparing across studies, performance on similar cognitive tests was divergent under dehydration conditions. 54 , 56 In studies conducted by Cian and colleagues, 53 , 54 participants were dehydrated to approximately 2.8% either through heat exposure or treadmill exercise. In both studies, performance was impaired on tasks examining visual perception, short-term memory, and psychomotor ability. In a series of studies using exercise in conjunction with water restriction as a means of producing dehydration, D’Anci and colleagues 56 observed only mild decrements in cognitive performance in healthy young men and women athletes. In these experiments, the only consistent effect of mild dehydration was significant elevations of subjective mood score, including fatigue, confusion, anger, and vigor. Finally, in a study using water deprivation alone over a 24-h period, no significant decreases in cognitive performance were seen with 2.6% dehydration 58 . It is possible therefore, that heat-stress may play a critical role in the effects of dehydration on cognitive performance.

Reintroduction of fluids under conditions of mild dehydration can reasonably be expected to reverse dehydration-induced cognitive deficits. Few studies have examined how fluid reintroduction may alleviate dehydration’s negative effects on cognitive performance and mood. One study 59 examined how water ingestion affected arousal and cognitive performance in young people following a period of 12-h water restriction. While cognitive performance was not affected by either water restriction or water consumption, water ingestion affected self-reported arousal. Participants reported increased alertness as a function of water intake. Rogers and coworkers 60 observed a similar increase in alertness following water ingestion in both high- and low-thirst participants. Water ingestion, however, had opposite effects on cognitive performance as a function of thirst. High-thirst participants’ performance on a cognitively demanding task improved following water ingestion, but low-thirst participants’ performance declined. In summary, hydration status consistently affected self-reported alertness, but effects on cognition were less consistent.

Several recent studies have examined the utility of providing water to school children on attentiveness and cognitive functioning in children. 61 – 63 In these experiments, children were not fluid restricted prior to cognitive testing, but were allowed to drink as usual. Children were then provided with a drink or no drink 20–45 minutes before the cognitive test sessions. In the absence of fluid restriction and without physiological measures of hydration status, the children in these studies should not be classified as dehydrated. Subjective measures of thirst were reduced in children given water, 62 and voluntary water intake in children varied from 57 ml to 250 ml. In these studies, as in the studies in adults, the findings were divergent and relatively modest. In the research led by Edmonds and colleagues, 61 , 62 children in the groups given water showed improvements in visual attention. However, effects on visual memory were less consistent, with one study showing no effects of drinking water on a spot-the-difference task in 6–7 year old children 61 and the other showing a significant improvement in a similar task in 7–9 year old children 62 In the research described by Benton and Burgess, 63 memory performance was improved by provision of water but sustained attention was not altered with provision of water in the same children.

Taken together these studies indicate that low to moderate dehydration may alter cognitive performance. Rather than indicating that the effects of hydration or water ingestion on cognition are contradictory, many of the studies differ significantly in methodology and in measurement of cognitive behaviors. These variances in methodology underscore the importance of consistency when examining relatively subtle chances in overall cognitive performance. However, in those studies in which dehydration were induced, most combined heat and exercise, thus it is difficult to disentangle the effects of dehydration on cognitive performance in temperate conditions, from the effects of heat and exercise. Additionally, relatively little is known about the mechanism of mild dehydration’s effects on mental performance. It has been proposed that mild dehydration acts as a physiological stressor which competes with and draws attention from cognitive processes 64 . However, research on this hypothesis is limited and merits further exploration.

Dehydration and delirium

Dehydration is a risk factor for delirium and delirium presenting as dementia in the elderly and in the very ill. 65 – 67 Recent work shows that dehydration is one of several predisposing factors in observed confusion in long-term care residents, 67 although in this study daily water intake was used as a proxy measure for dehydration rather than other, more direct clinical assessments such as urine or plasma osmolality. Older people have been reported as having reduced thirst and hypodypsia relative to younger people. In addition, fluid intake and maintenance of water balance can be complicated by factors such as disease, dementia, incontinence, renal insufficiency, restricted mobility, and drug side effects. In response to primary dehydration, older people have less thirst sensation and reduced fluid intakes in comparison to younger people. However, in response to heat stress, while older people still display a reduced thirst threshold, they do ingest comparable amounts of fluid as younger people. 20

Gastrointestinal function

Fluids in the diet are generally absorbed in the proximal small intestine, and absorption rate is determined by the rate of gastric emptying to the small intestine. Therefore, the total volume of fluid consumed will eventually be reflected in water balance, but the rate at which rehydration occurs is dependent upon factors which affect the rate of delivery of fluids to the intestinal mucosa. Gastric emptying rate is generally accelerated by the total volume consumed and slowed by higher energy density and osmolality. 68 In addition to water consumed in food (1 L/d) and beverages (~2–3 L/d), digestive secretions account for a far greater portion of water that passes through and is absorbed by the gastrointestinal tract (~8 L/d). 69 The majority of this water is absorbed by the small intestine, with a capacity of up to 15 L/d with the colon absorbing some 5 L/d. 69

Constipation, characterized by slow gastrointestinal transit, small, hard stools, and difficulty in passing stool, has a number of causes including medication use, inadequate fiber intake, poor diet, and illness. 70 Inadequate fluid consumption is touted as a common culprit in constipation, and increasing fluid intake is a frequently recommended treatment. Evidence suggests, however, that increasing fluids is only of usefulness in individuals in a hypohydrated state, and is of little utility in euhydrated individuals. 70 In young children with chronic constipation, increasing daily water intake by 50% did not affect constipation scores. 71 For Japanese women with low fiber intake, concomitant low water intake in the diet is associated with increased prevalence of constipation. 72 In older individuals, low fluid intake is a predictor for increased levels of acute constipation 73 , 74 with those consuming the least amount of fluid having over twice the frequency of constipation episodes than those consuming the most fluid. In one trial, researchers compared the utility of carbonated mineral water in reducing functional dyspepsia and constipation scores to tap water in individuals with functional dyspepsia. 75 When comparing carbonated mineral water to tap water, participants reported improvements in subjective gastric symptoms, but there were no significant improvements in gastric or intestinal function. The authors indicate that it is not possible to determine to what degree the mineral content of the two waters contributed to perceived symptom relief, as the mineral water contained greater levels of magnesium and calcium than the tap water. The available evidence suggests that increased fluid intake should only be indicated in individuals in a hypohydrated state. 71 , 69

Significant water loss can occur through the gastrointestinal tract, and this can be of great concern in the very young. In developing countries, diarrheal diseases are a leading cause of death in children resulting in approximately 1.5–2.5 million deaths per year. 76 Diarrheal illness results not only in a reduction in body water, but also in potentially lethal electrolyte imbalances. Mortality in such cases can many times be prevented with appropriate oral rehydration therapy, by which simple dilute solutions of salt and sugar in water can replace fluid lost by diarrhea. Many consider application of oral rehydration therapy to be one of the signal public health developments of the last century. 77

Kidney function

As noted above, the kidney is crucial in regulating water balance and blood pressure as well as removing waste from the body. Water metabolism by the kidney can be classified into regulated and obligate. Water regulation is hormonally mediated, with the goal of maintaining a tight range of plasma osmolality between 275 to 290 mOsm/kg. Increases in plasma osmolality, and activation of osmoreceptors (intracellular) and baroreceptors (extracellular) stimulate hypothalamic release of arginine vasopressin (AVP). AVP acts at the kidney to decrease urine volume and promote retention of water, and the urine becomes hypertonic. With decreased plasma osmolality, vasopressin release is inhibited, and the kidney increases hypotonic urinary output.

In addition to regulating fluid balance, the kidneys require water for the filtration of waste from the blood stream and excretion via urine. Water excretion via the kidney removes solutes from the blood, and a minimum obligate urine volume is required to remove the solute load with a maximum output volume of 1 L/h. 78 This obligate volume is not fixed, but is dependent upon the amount of metabolic solutes to be excreted and levels of AVP. Depending on the need for water conservation, basal urine osmolality ranges from 40 mOsm/kg up to a maximum of 1400 mOsm/kg. 78 The ability to both concentrate and dilute urine decreases with age, with a lower value of 92 mOsm/kg and an upper range falling between 500–700 mOsm/kg for individuals over 70. 79 – 81 Under typical conditions, in an average adult, urine volume of 1.5 to 2.0 L/d would be sufficient to clear a solute load of 900 to 1200 mOsm/d. During water conservation and the presence of AVP, this obligate volume can decrease to 0.75–1.0 L/d and during maximal diuresis can require up to 20 L/d to remove the same solute load. 78 , 80 , 81 In cases of water loading, if the volume of water ingested cannot be compensated for with urine output, having overloaded the kidney’s maximal output rate, an individual can enter a hyponatremic state as described above.

Heart function and hemodynamic response

Blood volume, blood pressure, and heart rate are closely linked. Blood volume is normally tightly regulated by matching water intake and water output, as described in the section on kidney function. In healthy individuals, slight changes in heart rate and vasoconstriction act to balance the effect of normal fluctuations in blood volume on blood pressure. 82 Decreases in blood volume can occur, through blood loss (or blood donation), or loss of body water through sweat, as seen with exercise. Blood volume is distributed differently relative to the position of the heart whether supine or upright, and moving from one position to the other can lead to increased heart rate, a fall in blood pressure and, in some cases, lead to syncope. This postural hypotension (or orthostatic hypotension) can be mediated by drinking 300–500 ml of water. 83 , 84 Water intake acutely reduces heart rate and increases blood pressure in both normotensive and hypertensive individuals. 85 These effects of water intake on the pressor effect and heart rate occur within 15–20 minutes of drinking water and can last for up to 60 minutes. Water ingestion is also beneficial in preventing vasovagal reaction with syncope in blood donors at high risk for post-donation syncope. 86 The effect of water drinking in these situations is thought to be due to effects on the sympathetic nervous system rather than to changes in blood volume. 83 , 84 Interestingly, in rare cases, individuals may experience bradycardia and syncope after swallowing cold liquids. 87 – 89 While swallow syncope can be seen with other substances than water, swallow syncope further supports the notion that the result of water ingestion in the pressor effect has both a neural component as well as a cardiac component.

Water deprivation and dehydration can lead to the development of headache. 90 Although this observation is largely unexplored in the medical literature, some observational studies indicate that water deprivation, in addition to impairing concentration and increasing irritability, can serve as a trigger for migraine and also prolong migraine. 91 , 92 In those with water deprivation-induced headache, ingestion of water provided relief from headache in most individuals within 30 min to 3 h. 92 It is proposed that water deprivation-induced headache is the result of intracranial dehydration and total plasma volume. Although provision of water may be useful in relieving dehydration related headache, the utility of increasing water intake for the prevention of headache is less well documented.

The folk wisdom that drinking water can stave off headaches has been relatively unchallenged, and has more traction in the popular press than in the medical literature. Recently, one study examined increased water intake and headache symptoms in headache patients. 93 In this randomized trial, patients with a history of different types of headache, including migraine and tension headache, were either assigned to a placebo condition (a non-drug tablet) or the increased water condition. In the water condition, participants were instructed to consume an additional volume of 1.5 L water/day on top of what they already consumed in foods and fluids. Water intake did not affect number of headache episodes, but was modestly associated with reduction in headache intensity and reduced duration of headache. The data from this study suggest that water is limited as prophylaxis in headache sufferers, and the ability of water to reduce or prevent headache in a broader population remains unknown.

One of the more pervasive myths regarding water intake is the improvement of the skin or complexion. By improvement, it is generally understood that individuals are seeking to have a more “moisturized” look to the surface skin, or to minimize acne or other skin conditions. Numerous lay sources such as beauty and health magazines as well as the Internet suggest that drinking 8–10 glasses of water a day will “flush toxins from the skin” and “give a glowing complexion” despite a general lack of evidence 94 , 95 to support these proposals. The skin, however, is important in maintaining body water levels and preventing water loss into the environment.

The skin contains approximately 30% water, which contributes to plumpness, elasticity, and resiliency. The overlapping cellular structure of the stratum corneum and lipid content of the skin serves as “waterproofing” for the body. 96 Loss of water through sweat is not indiscriminate across the total surface of the skin, but is carried out by eccrine sweat glands, which are evenly distributed over most of the body surface. 97 Skin dryness is usually associated with exposure to dry air, prolonged contact with hot water and scrubbing with soap (both strip oils from the skin), medical conditions and medications. While more serious levels of dehydration can be reflected in reduced skin turgor, 98 , 99 with tenting of the skin as a flag for dehydration, overt skin turgor in individuals with adequate hydration is not altered. Water intake, particularly in individuals with low initial water intake, can improve skin thickness and density as measured by sonogram, 100 and offsets transepidermal water loss, and can improve skin hydration. 101 Adequate skin hydration, however, is not sufficient to prevent wrinkles or other signs of aging, which are related to genetics, and sun and environmental damage. Of more utility to individuals already consuming adequate fluids, the use of topical emollients will improve skin barrier function and improve the look and feel of dry skin. 102 , 103

Hydration and chronic diseases

Many chronic diseases have multifactorial origins. In particular, differences in lifestyle and the impact of environment are known to be involved and constitute risk factors that are still being evaluated. Water is quantitatively the most important nutrient. In the past, scientific interest with regard to water metabolism was mainly directed toward the extremes of severe dehydration and water intoxication. There is evidence, however, that mild dehydration may also account for some morbidities. 4 , 104 There is currently no consensus on a “gold standard” for hydration markers, particularly for mild dehydration. As a consequence, the effects of mild dehydration on the development of several disorders and diseases have not been well documented.

There is strong evidence showing that good hydration reduces the risk of urolithiasis (See Table 2 for evidence categories). Less strong evidence links good hydration with reduced incidence of constipation, exercise asthma, hypertonic dehydration in the infant, and hyperglycemia in diabetic ketoacidosis. Good hydration is associated with a reduction in urinary tract infections, hypertension, fatal coronary heart disease, venous thromboembolism, and cerebral infarct but all these effects need to be confirmed by clinical trials. For other conditions such as bladder or colon cancer, evidence of a preventive effect of maintaining good hydration is not consistent (see Table 3 ).

Categories of evidence in evaluating the quality of reports

Adapted from Manz 104

Hydration Status and Chronic Diseases

III. Water consumption and requirements and relationships to total energy intake

Water consumption, water requirements and energy intake are linked in fairly complex ways. This is partially because physical activity and energy expenditures affect the need for water but also because a large shift in beverage consumption over the past century or more has led to consumption of a significant proportion of our energy intake from caloric beverages. Nonregulatory beverage intake, as noted earlier, has assumed a much greater role for individuals. 19 In this section we first review current patterns of water intake, then refer to a full meta-analysis of the effects of added water on energy intake. This includes adding water to the diet and water replacement for a range of caloric and diet beverages, including sugar-sweetened beverages, juice, milk, and diet beverages. The third component is a discussion of water requirements and suggestions for considering the use of ml water/kcal energy intake as a metric.

A. Patterns and trends of water consumption

Measurement of total fluid water consumption in free-living individuals is fairly new in focus. As a result, the state of the science is poorly developed, data are most likely fairly incomplete, and adequate validation of the measurement techniques used are not available. We first present varying patterns and trends of water intake for the United States over the past three decades and review briefly the work on water intake in Europe.

We have really no information to allow us to assume that consumption of water alone or beverage containing water affects hydration differentially. 3 , 105 Some epidemiological data suggests water might have differential metabolic effects when consumed as water alone rather than water contained in caffeinated or flavored or sweetened beverages but these data are at best suggestive of an issue deserving of exploration. 106 , 107 We do show below from the research of Ershow that beverages not consisting of solely water do contain less than 100% water.

One study in the United States has attempted to examine all the sources of water in our diet. 16 , 17 These data are cited in Table 4 as the Ershow study and were based on National Food Consumption Survey food and fluid intake data from 1977–78. These data are presented in Table 4 for children 2–18 (Panel A) and for adults 19 and older (Panel B). Ershow and colleagues spent a great deal of time working out ways to convert USDA dietary data into water intake, including water absorbed during the cooking process, water in food, and all sources of drinking water. 16 , 17

Beverage Pattern Trends in the United States for Children aged 2–18 and Adults Aged 19 and older, Nationally Representative

Note: The data are age and sex adjusted to 1965; for 1977–78 the 488, 95, and 736 come from the Ershow calculations.

These created a number of categories and used a range of factors measured in other studies to estimate the water categories. The water that is found in food, based on food composition table data, was 393ml for children. The water that was added as a result of cooking (e.g., rice) was 95 ml. That consumed as a beverage directly as water was 624 ml. The water found in other fluids as noted comprised the remainder of the ml with the most water coming from whole fat milk and juices (506 ml). There is a small discrepancy between the Ershow total fluid intake measures for these children and that of the normal USDA figure. That is because USDA does not remove milk fats and solids, fiber and other food constituents found in beverages, particularly, juice and milk.

A key point to be seen in these nationally representative US data is enormous variability in the amount of water consumed between survey waves (see Figure 1 which highlights that large variation in water intake measured in these surveys). Although adult and child water intake moved up and down at the same time, for reasons we cannot explain, the variation is greater among children than adults. This is partly that the questions asked have varied and there has not been detailed probing for water intake as the focus has been on obtaining measures of macro-and micronutrients. Dietary survey methods in the past have focused on obtaining foods and beverages containing nutrient and nonnutritive sweeteners but not on water. Related are the huge differences between the NHANES 1988–1994 and 1999 and later surveys and the USDA surveys. In addition even the NHANES1999–2002 and the 2003–6 surveys differ greatly. This represents a shift in mode of questioning to inclusion of water intake as part of a standard 24-hour recall rather than as standalone questions. Water was not even measured in 1965, and the way the questions have been asked and the limitation on probes for water intake are very clear from a review of the questionnaires plus these data. Essentially in the past people were asked how much water they consumed in a day and now they are asked these questions as part of a 24-hour recall survey. However, unlike other caloric and diet beverages, there are limited probes for water. These must be viewed as crude approximations of total water intake without any strong research to show if they are over- or underestimated. We know from our own research with several studies of water and two on-going random controlled trials that probes that include consideration of all beverages including water as a separate item provide more complete data.

Water Consumption Trends from USDA and NHANES Surveys (ml/day/capita), weighted to be nationally representative

Note: this includes water from fluids only, excluding water in foods. Sources for 1965, 77–78, 89- are USDA. Others are NHANES and 2005–6 is joint USDA and NHANES

Water consumption data for Europe are collected far more selectively than even the crude water intake questions from NHANES. The recent EFSA report provides measures of water consumption from a range of studies in Europe. 4 , 105 , 108 , 109 Essentially what these studies show is that total water intake is lower across Europe than the United States. As with the United States data, none are based on long-term carefully measured or even repeated 24-hour recall measures of water intake from food and beverages. In unpublished work Popkin and Jebb 110 are examining water intake in UK adults in 1986–87 and 2001–2. Their intake increased by 226 ml/d over this time period but still is only 1787 ml/d in the latter period, far below the US figure for 2005–6 of 2793 or earlier figures for comparably aged adults.

There are a few studies in the US and Europe that utilize 24-hour urine and serum osmolality measures to determine total water turnover and this measure of hydration status. These studies suggest that US adults consume over 2100 ml of water per day while those from Europe consume less than a half liter or more. 4 , 111 Data on total urine collection would appear to be another useful measure for examining total water intake. Of course few studies aside from the Donald adolescent cohort in Germany have collected such data on population levels for large samples. 109

B. The effects of water consumption on overall energy intake

There is an extensive literature that focuses on the impact of sugar-sweetened beverages on weight and risk of obesity, diabetes and heart disease; however the perspective of providing more water and its impact on health has not been examined. The water literature does not address portion sizes but rather focuses mainly on water ad libitum or in selected portions compared with other caloric beverages. Elsewhere we have prepared a detailed meta-analysis of the effects of water intake alone (adding additional water), replacing sugar-sweetened beverages, juice, milk and diet beverages. 112

In general, the results of this review suggest that water, when replacing sugar-sweetened beverages, juice and milk is linked with reduced energy intake. This comes mainly from the clinical feeding studies but also from one very good random controlled school intervention and several other epidemiological and intervention studies. Aside from portion sizes, there are issues of timing of the beverage intake and meals (delay time from the beverage to the meal) and types of caloric sweeteners that remain to be considered. However when beverages are consumed in a normal free-living situations where 5–8 eating occasions are the norm, the delay time from the beverage to the meal may matter less. 113 – 115

The literature on children is extremely limited as it relates to water intake. However, the excellent German school intervention with water would suggest the effects of water on overall energy intake of children might be comparable to that of adults. 116 In this German study children were educated on the value of water and provided in school with special filtered drinking fountains and water bottles. The intervention school children increased by 1.1 glasses/day (P<0.001) and reduced their risk of overweight by 31% (OR=0.69, P=0.40).

C. Water requirements: Evaluation of the adequacy of water intake

Classically, water data are examined in terms of milliliters (or some other measure of water volume consumed per capita per day by age group). This measure does not link fluid and caloric intake. Disassociation of fluid and calorie intake difficult for clinicians dealing with an older person who has reduced caloric intake. This ml water measure assumes some mean body size (or surface area) and a mean level of physical activity – both determinants of not only energy expenditure, but also of water balance. Children are dependent on adults for access to water and studies suggest that a larger surface area to volume ratio makes them susceptible to changes in skin temperatures, linked with ambient temperature shifts. 117 One option utilized by some scholars is to explore in ml/kcal of food and beverage intake as was done in the 1989 US RDAs. 4 , 118 This is an option interpretable for clinicians and does incorporate in some sense body size or surface area and activity. It has one disadvantage, namely that water as consumed with caloric beverages, affects both the numerator and denominator; however we do not know a measure that could be independent of this direct effect on body weight and/or total caloric intake.

Despite its critical importance in health and nutrition, as noted earlier, the array of available research that serves as a basis for determining requirements for water or fluid intake, or even rational recommendations for populations, is limited compared to most other nutrients. While this deficit may be partly explained by the highly sensitive set of neurophysiological adaptations and adjustments that occur over a large range of fluid intake to protect body hydration and osmolarity, this deficit remains a challenge for the nutrition and public health community. The latest official effort at recommending water intake for different subpopulations was a part of the Dietary Reference Intake process of the Institute of Medicine of the National Academy of Science’s Report on Dietary Reference Intakes on Water and Electrolytes as reported in 2005. 3 As a graphic acknowledgement of the limited database upon which to express Estimated Average Requirements for water for different population groups, the Committee and the Institute of Medicine were forced to state “While it might appear useful to estimate an average requirement (an EAR) for water, an EAR based on data is not possible”. Given the extreme variability in water needs that are not solely based on differences in metabolism, but also on environmental conditions and activities, there is not a single level of water intake that would assure adequate hydration and optimum health for half of all apparently healthy persons in all environmental conditions. Thus, an Adequate Intake (AI) is established in place of an EAR for water.

The AI for different population groups was set as the median water intake in populations from the National Health and Nutrition Examination Survey, whose intake levels varied greatly based on the survey years (e.g., NHANES 1988–94 vs NHANES 1999–2002) and also were much higher than the USDA surveys (e.g., 1989–91, 1994–98, or 2005–6). If the AI for adults as expressed in Table 5 is taken as a recommended intake, we question the wisdom of the conversion of an AI into recommended water or fluid intake. The first problem is the almost certain inaccuracy of the fluid intake information from the national surveys, even though that problem may also exist for other nutrients. More importantly, from the standpoint of translating an AI into recommended fluid intake for individuals or populations, is the decision in setting the AI to add an additional roughly 20% of water intake, which is derived from some foods in addition to water and beverages. While this may be a legitimate effort to express total water intake as a basis for setting the AI, the recommendations that derive from this IOM report would better be directed at recommendations for water and other fluid intake on the assumption that the water content of foods would be a “passive” addition to total water intake. In this case, the observations of the DRI committee that water intake needs to meet needs imposed by not only metabolism and environmental conditions, but also body size, gender and physical activity. Those are the well studied factors which allow a rather precise measurement and determination of energy intake requirements. It is only logical that those same factors might underlie recommendations to meet water intake needs in the same populations and individuals, and therefore that consideration be given and data gathering be done by experimental and population research, to the possibility that water intake needs would best be expressed relative to the calorie requirements, as is done regularly in the clinical setting.

Water requirements expressed in relation to energy recommendations

AI for total fluids derived from dietary reference intakes for water, potassium, sodium, chloride, and sulfate

Ratios for water intake based on the AI for water in liters/day calculated using EER for each range of physical activity. EER adapted from the Institute of Medicine Dietary Reference Intakes Macronutrients Report, 2002.

It is important to note that only a few countries even include water on the list of nutrients. 119 The European Food Safety Authority is developing a European wide standard. 105 At present only the United States and Germany provide Adequate intake (AI) values but no other country does that. 3 , 120

Another way of considering an approach to the estimation of water requirements beyond the limited usefulness of the AI or estimated mean intake is to express water intake requirements in relation to energy requirements in ml/kcal. An argument for this approach includes the observation that energy requirements are strongly evidence-based in each age and gender group on extensive research which takes into account body size, and activity level which are crucial determinants of energy expenditure which must be met by dietary energy intake. Such measures of expenditure have used highly accurate methods such as doubly-labeled water and thus EERs (Estimated Energy Requirements) have been set based on solid data rather than the compromise inherent in the AIs for water. Those same determinants of energy expenditure and recommended intake are also applicable to water utilization and balance and this provides an argument for pegging water/fluid intake recommendations to the better studied energy recommendations. The extent to which water intake and requirements are determined by energy intake and expenditure is understudied but in the clinical setting it has long been practice to supply 1 ml per kcal administered by tube to patients unable to take in food or fluids. Factors such as fever or other drivers of increased metabolism affect both energy expenditure and fluid loss and are thus linked in clinical practice. This concept may well deserve consideration in the setting of population intake goals.

Finally, for decades there has been discussion of expressing nutrient requirements per 1000 kcal so that a single number would apply reasonable across the spectrum of age groups. This idea, which has never been adopted by the Institute of Medicine (IOM) and National Academy of Science, may lend itself to an improved expression of water/fluid intake requirements which must replace the AIs eventually. Table 5 presents the IOM water requirements and then develops a ratio of ml/kcal based on them. The European Food Safety Agency refers positively to the possibility of expressing water intake recommendations in ml/kcal as a function of energy requirements. 105 Outliers in the adult male categories which reach ratios as high as 1.5 may well be based on American AI data which are above those in the more moderate and likely more accurate European recommendations.

Exploring the topic of utilizing ml/kcal as the way to examine water intake and water gaps, we take the full set of water intake AIs for each age-gender grouping and examine total intake in Table 6 . They suggest a high level of fluid deficiency. Since a large proportion of fluids in the US are based on caloric beverages and this proportion has changed markedly over the past 30 years, fluid intake increases both the numerator and denominator of this ml/kcal relationship. Nevertheless even using 1 ml/kcal as the AI would leave a gap for all children and adolescents. We then utilize the NHANES physical activity data translated into METS/day to categorize all individuals by physical activity level and thus varying caloric requirements. Using these measures show a fairly large fluid gap, particularly for adult males as well as children.

Water intake and water intake gaps based on US Water Adequate Intake Recommendations (based on utilization of water and physical activity data from NHANES 2005–6.

Note: Recommended water intake for actual activity level is the upper end of the range for moderate and active.

IV. DISCUSSION

This review has pointed out a number of issues related to water, hydration and health. As undoubtedly the most important nutrient and the only one whose absence will be lethal within days, understanding of water measurement and requirements are very important. The effects of water on daily performance and short and long-term health are quite clear. There are few negative effects of water intake and the evidence of positive effects is quite clear from the literature.

Little work has been done to measure total fluid intake systematically and there is no understanding of measurement error and best methods of understanding fluid intake. The most definitive US and European documents on total water requirements as based on these extant intake data. 3 , 105 We feel that absence of validation of methods for water consumption intake levels and patterns represents a major gap. Little exploration of even varying methods of probing to collect better water recall data have been conducted.

Of course, the other half of the issue is the need for understanding total hydration status. We have no acceptable biomarkers of hydration status at the population level. Controversy exists about current knowledge of hydration status among older Americans. 6 , 121 This represents a topic understudied at the population level though certainly scholars are focused on attempting to create biomarkers for measurement of hydration status.

As we have noted, the importance of understanding the role of fluid intake on health has emerged as a more important topic partially because of the shift toward large proportions of fluids coming from caloric beverages. We summarized briefly a related systematic review of the clinical, epidemiological and intervention literature on the effects of added water on health. As a replacement for SSB’s, juice, or whole milk there are clear effects in that energy intake is reduced by about 10–13% of total energy intake. However on these topics, there are only a few longer-term systematic interventions and no published random-controlled longer-term trials. There is very minimal evidence on the effects of just adding water to the diet and of replacing water with diet beverages.

Limitations to this review are many. One certainly is the omission of discussions of the issue of potential differences in the metabolic functioning of different types of beverages 122 . There is little basis at this point for delving into this sparse literature. Another is omission of the potential effects of fructose (from all caloric sweeteners) when consumed in caloric beverages on abdominal fat and subsequently all the metabolic conditions directly linked with this (e.g., diabetes). 123 – 126 We do not review in any detail all the array of biomarkers being considered to measure hydration status as there is just no sense in the field today that there is a measurement that covers more than a very short time period except for 24-hour total urine collection.

We suggest some ways to examine water requirements as a means to encouraging more dialogue on this important topic. Given the importance of water to our health and of caloric beverages to our total energy intake and potential risks of nutrition-related non communicable diseases, understanding both the requirements for water related to energy requirements, and the differential effects of water vs. other caloric beverages remain important outstanding issues.

In the end, this review has attempted to provide some sense of the importance of water to our health, its role in relationship to the rapid increases of obesity and other related diseases, and our gaps in understanding measurement and requirements. Water is essential to our survival and to our civilizations’ and we hope this critical role will sharpen our focus on water in human health.

Acknowledgments

Funding was provided by the Nestlé Waters, Issy-les-Moulineaux, France, 5ROI AGI0436 from the National Institute on Aging Physical Frailty Program, and NIH R01- CA109831 and R01-CA121152. We also wish to thank Ms. Frances L. Dancy for administrative assistance, Mr. Tom Swasey for graphics support, Dr. Melissa Daniels for assistance, and Florence Constant (Nestle’s Water Research) for advice and references.

Contributor Information

Barry M. Popkin, Department of Nutrition, University of North Carolina, Chapel Hill, NC.

Kristen E. D’Anci, Department of Psychology, Tufts University, Medford, MA.

Irwin H. Rosenberg, Nutrition and Neurocognition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA.

Wastewater Treatment and Reuse: a Review of its Applications and Health Implications

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• Published: 10 May 2021
• Volume 232 , article number  208 , ( 2021 )

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• Kavindra Kumar Kesari   ORCID: orcid.org/0000-0003-3622-9555 1   na1 ,
• Ramendra Soni 2   na1 ,
• Qazi Mohammad Sajid Jamal 3 ,
• Pooja Tripathi 4 ,
• Jonathan A. Lal 2 ,
• Niraj Kumar Jha 5 ,
• Mohammed Haris Siddiqui 6 ,
• Pradeep Kumar 7 ,
• Vijay Tripathi 2 &
• Janne Ruokolainen 1  

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Water scarcity is one of the major problems in the world and millions of people have no access to freshwater. Untreated wastewater is widely used for agriculture in many countries. This is one of the world-leading serious environmental and public health concerns. Instead of using untreated wastewater, treated wastewater has been found more applicable and ecofriendly option. Moreover, environmental toxicity due to solid waste exposures is also one of the leading health concerns. Therefore, intending to combat the problems associated with the use of untreated wastewater, we propose in this review a multidisciplinary approach to handle wastewater as a potential resource for use in agriculture. We propose a model showing the efficient methods for wastewater treatment and the utilization of solid wastes in fertilizers. The study also points out the associated health concern for farmers, who are working in wastewater-irrigated fields along with the harmful effects of untreated wastewater. The consumption of crop irrigated by wastewater has leading health implications also discussed in this review paper. This review further reveals that our current understanding of the wastewater treatment and use in agriculture with addressing advancements in treatment methods has great future possibilities.

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1 Introduction

Rapidly depleting and elevating the level of freshwater demand, though wastewater reclamation or reuse is one of the most important necessities of the current scenario. Total water consumption worldwide for agriculture accounts 92% (Clemmens et al., 2008 ; Hoekstra & Mekonnen, 2012 ; Tanji & Kielen, 2002 ). Out of which about 70% of freshwater is used for irrigation (WRI, 2020 ), which comes from the rivers and underground water sources (Pedrero et al., 2010 ). The statistics shows serious concern for the countries facing water crisis. Shen et al. ( 2014 ) reported that 40% of the global population is situated in heavy water–stressed basins, which represents the water crisis for irrigation. Therefore, wastewater reuse in agriculture is an ideal resource to replace freshwater use in agriculture (Contreras et al., 2017 ). Treated wastewater is generally applied for non-potable purposes, like agriculture, land, irrigation, groundwater recharge, golf course irrigation, vehicle washing, toilet flushes, firefighting, and building construction activities. It can also be used for cooling purposes in thermal power plants (Katsoyiannis et al., 2017 ; Mohsen, 2004 ; Smith, 1995 ; Yang et al., 2017 ). At global level, treated wastewater irrigation supports agricultural yield and the livelihoods of millions of smallholder farmers (Sato et al., 2013 ). Global reuse of treated wastewater for agricultural purposes shows wide variability ranging from 1.5 to 6.6% (Sato et al., 2013 ; Ungureanu et al., 2018 ). More than 10% of the global population consumes agriculture-based products, which are cultivated by wastewater irrigation (WHO, 2006 ). Treated wastewater reuse has experienced very rapid growth and the volumes have been increased ~10 to 29% per year in Europe, the USA, China, and up to 41% in Australia (Aziz & Farissi, 2014 ). China stands out as the leading country in Asia for the reuse of wastewater with an estimated 1.3 M ha area including Vietnam, India, and Pakistan (Zhang & Shen, 2017 ). Presently, it has been estimated that, only 37.6% of the urban wastewater in India is getting treated (Singh et al., 2019 ). By utilizing 90% of reclaimed water, Israel is the largest user of treated wastewater for agriculture land irrigation (Angelakis & Snyder, 2015 ). The detail information related to the utilization of freshwater and treated wastewater is compiled in Table 1 .

Many low-income countries in Africa, Asia, and Latin America use untreated wastewater as a source of irrigation (Jiménez & Asano, 2008 ). On the other hand, middle-income countries, such as Tunisia, Jordan, and Saudi Arabia, use treated wastewater for irrigation (Al-Nakshabandi et al., 1997 ; Balkhair, 2016a ; Balkhair, 2016b ; Qadir et al., 2010 ; Sato et al., 2013 ).

Domestic water and treated wastewater contains various type of nutrients such as phosphorus, nitrogen, potassium, and sulfur, but the major amount of nitrogen and phosphorous available in wastewater can be easily accumulated by the plants, that’s why it is widely used for the irrigation (Drechsel et al., 2010 ; Duncan, 2009 ; Poustie et al., 2020 ; Sengupta et al., 2015 ). The rich availability of nutrients in reclaimed wastewater reduces the use of fertilizers, increases crop productivity, improves soil fertility, and at the same time, it may also decrease the cost of crop production (Chen et al., 2013 a; Jeong et al., 2016 ). The data of high nutritional values in treated wastewater is shown in Fig. 1 .

Nutrient concentrations (mg/L) of freshwater/wastewater (Yadav et al., 2002 )

Wastewater reuse for crop irrigation showed several health concerns (Ungureanu et al., 2020 ). Irrigation with the industrial wastewater either directly or mixing with domestic water showed higher risk (Chen et al., 2013). Risk factors are higher due to heavy metal and pathogens contamination because heavy metals are non-biodegradable and have a long biological half-life (Chaoua et al., 2019 ; WHO, 2006 ). It contains several toxic elements, i.e., Cu, Cr, Mn, Fe, Pb, Zn, and Ni (Mahfooz et al., 2020 ). These heavy metals accumulate in topsoil (at a depth of 20 cm) and sourcing through plant roots; they enter the human and animal body through leafy vegetables consumption and inhalation of contaminated soils (Mahmood et al., 2014 ). Therefore, health risk assessment of such wastewater irrigation is important especially in adults (Mehmood et al., 2019 ; Njuguna et al., 2019 ; Xiao et al., 2017 ). For this, an advanced wastewater treatment method should be applied before release of wastewater in the river, agriculture land, and soils. Therefore, this review also proposed an advance wastewater treatment model, which has been tasted partially at laboratory scale by Kesari and Behari ( 2008 ), Kesari et al. ( 2011a , b ), and Kumar et al. ( 2010 ).

For a decade, reuse of wastewater has also become one of the global health concerns linking to public health and the environment (Dang et al., 2019 ; Narain et al., 2020 ). The World Health Organization (WHO) drafted guidelines in 1973 to protect the public health by facilitating the conditions for the use of wastewater and excreta in agriculture and aquaculture (WHO, 1973 ). Later in 2005, the initial guidelines were drafted in the absence of epidemiological studies with minimal risk approach (Carr, 2005 ). Although, Adegoke et al. ( 2018 ) reviewed the epidemiological shreds of evidence and health risks associated with reuse of wastewater for irrigation. Wastewater or graywater reuse has adverse health risks associated with microbial hazards (i.e., infectious pathogens) and chemicals or pharmaceuticals exposures (Adegoke et al., 2016 ; Adegoke et al., 2017 ; Busgang et al., 2018 ; Marcussen et al., 2007 ; Panthi et al., 2019 ). Researchers have reported that the exposure to wastewater may cause infectious (helminth infection) diseases, which are linked to anemia and impaired physical and cognitive development (Amoah et al., 2018 ; Bos et al., 2010 ; Pham-Duc et al., 2014 ; WHO, 2006 ).

Owing to an increasing population and a growing imbalance in the demand and supply of water, the use of wastewater has been expected to increase in the coming years (World Bank, 2010 ). The use of treated wastewater in developed nations follows strict rules and regulations. However, the direct use of untreated wastewater without any sound regulatory policies is evident in developing nations, which leads to serious environmental and public health concerns (Dickin et al., 2016 ). Because of these issues, we present in this review, a brief discussion on the risk associated with the untreated wastewater exposures and advanced methods for its treatment, reuse possibilities of the treated wastewater in agriculture.

2 Environmental Toxicity of Untreated Wastewater

Treated wastewater carries larger applicability such as irrigation, groundwater recharge, toilet flushing, and firefighting. Municipal wastewater treatment plants (WWTPs) are the major collection point for the different toxic elements, pathogenic microorganisms, and heavy metals. It collects wastewater from divergent sources like household sewage, industrial, clinical or hospital wastewater, and urban runoff (Soni et al., 2020 ). Alghobar et al. ( 2014 ) reported that grass and crops irrigated with sewage and treated wastewater are rich in heavy metals in comparison with groundwater (GW) irrigation. Although, heavy metals classified as toxic elements and listed as cadmium, lead, mercury, copper, and iron. An exceeding dose or exposures of these heavy metals could be hazardous for health (Duan et al., 2017 ) and ecological risks (Tytła, 2019 ). The major sources of these heavy metals come from drinking water. This might be due to the release of wastewater into river or through soil contamination reaches to ground water. Table 2 presenting the permissible limits of heavy metals presented in drinking water and its impact on human health after an exceeding the amount in drinking water, along with the route of exposure of heavy metals to human body.

Direct release in river or reuse of wastewater for irrigation purposes may create short-term implications like heavy metal and microbial contamination and pathogenic interaction in soil and crops. It has also long-term influence like soil salinity, which grows with regular use of untreated wastewater (Smith, 1995 ). Improper use of wastewater for irrigation makes it unsafe and environment threatening. Irrigation with several different types of wastewater, i.e., industrial effluents, municipal and agricultural wastewaters, and sewage liquid sludge transfers the heavy metals to the soil, which leads to accumulation in crops due to improper practices. This has been identified as a significant route of heavy metals into aquatic resources (Agoro et al., 2020 ). Hussain et al. ( 2019 ) investigated the concentration of heavy metals (except for Cd) was higher in the soil irrigated with treated wastewater (large-scale sewage treatment plant) than the normal ground water, also reported by Khaskhoussy et al. ( 2015 ).

In other words, irrigation with wastewater mitigates the quality of crops and enhances health risks. Excess amount of copper causes anemia, liver and kidney damage, vomiting, headache, and nausea in children (Bent & Bohm, 1995 ; Madsen et al., 1990 ; Salem et al., 2000 ). A higher concentration of arsenic may lead to bone and kidney cancer (Jarup, 2003 ) and results in osteopenia or osteoporosis (Puzas et al., 2004 ). Cadmium gives rise to musculoskeletal diseases (Fukushima et al., 1970 ), whereas mercury directly affects the nervous system (Azevedo et al., 2014 ).

3 Spread of Antibiotic Resistance

Currently, antibiotics are highly used for human disease treatment; however, uses in poultries, animal husbandries, biochemical industries, and agriculture are common practices these days. Extensive use and/or misuse of antibiotics have given rise to multi-resistant bacteria, which carry multiple resistance genes (Icgen & Yilmaz, 2014 ; Lv et al., 2015 ; Tripathi & Tripathi, 2017 ; Xu et al., 2017 ). These multidrug-resistant bacteria discharged through the sewage network and get collected into the wastewater treatment plants. Therefore, it can be inferred that the WWTPs serve as the hotspot of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Though, these antibiotic-resistant bacteria can be disseminated to the different bacterial species through the mobile genetic elements and horizontal gene transfer (Gupta et al., 2018 ). Previous studies indicated that certain pathogens might survive in wastewater, even during and after the treatment processes, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) (Börjesson et al., 2009 ; Caplin et al., 2008 ). The use of treated wastewater in irrigation provides favorable conditions for the growth and persistence of total coliforms and fecal coliforms (Akponikpe et al., 2011 ; Sacks & Bernstein, 2011 ). Furthermore, few studies have also reported the presence of various bacterial pathogens, such as Clostridium , Salmonella , Streptococci , Viruses, Protozoa, and Helminths in crops irrigated with treated wastewater (Carey et al., 2004 ; Mañas et al., 2009 ; Samie et al., 2009 ). Goldstein ( 2013 ) investigated the survival of ARB in secondary treated wastewater and proved that it causes serious health risks to the individuals, who are exposed to reclaimed water. The U.S. Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) have already declared the ARBs as the imminent hazard to human health. According to the list published by WHO, regarding the development of new antimicrobial agents, the ESKAPE ( Enterococcus faecium , S. aureus , Klebsiella pneumoniae , Acinetobacter baumannii , Pseudomonas aeruginosa , and Enterobacter species) pathogens were designated to be “priority status” as their occurrence in the food chain is considered as the potential and major threat for the human health (Tacconelli et al., 2018 ).

These ESKAPE pathogens have acquired the multi drug resistance mechanisms against oxazolidinones, lipopeptides, macrolides, fluoroquinolones, tetracyclines, β-lactams, β-lactam–β-lactamase inhibitor combinations, and even those antibiotics that are considered as the last line of defense, including carbapenems and glycopeptides (Giddins et al., 2017 ; Herc et al., 2017 ; Iguchi et al., 2016 ; Naylor et al., 2018 ; Zaman et al., 2017 ), by the means of genetic mutation and mobile genetic elements. These cluster of ESKAPE pathogens are mainly responsible for lethal nosocomial infections (Founou et al., 2017 ; Santajit & Indrawattana, 2016 ).

Due to the wide application of antibiotics in animal husbandry and inefficient capability of wastewater treatment plants, the multidrug-resistant bacteria such as tetracyclines, sulfonamides, β-lactam, aminoglycoside, colistin, and vancomycin in major are disseminated in the receiving water bodies, which ultimately results in the accumulation of ARGs in the irrigated crops (He et al., 2020 ).

4 Toxic Contaminations in Wastewater Impacting Human Health

The release of untreated wastewater into the river may pose serious health implications (König et al., 2017 ; Odigie, 2014 ; Westcot, 1997 ). It has been already discussed about the household and municipal sewage which contains a major amount of organic materials and pathogenic microorganisms and these infectious microorganisms are capable of spreading various diseases like typhoid, dysentery, diarrhea, vomiting, and malabsorption (Jia & Zhang, 2020 ; Numberger et al., 2019 ; Soni et al., 2020 ). Additionally, pharmaceutical industries also play a key role in the regulation and discharge of biologically toxic agents. The untreated wastewater also contains a group of contaminants, which are toxic to humans. These toxic contaminations have been classified into two major groups: (i) chemical contamination and (ii) microbial contamination.

4.1 Chemical Contamination

Mostly, various types of chemical compounds released from industries, tanneries, workshops, irrigated lands, and household wastewaters are responsible for several diseases. These contaminants can be organic materials, hydrocarbons, volatile compounds, pesticides, and heavy metals. Exposure to such contaminants may cause infectious diseases like chronic dermatoses and skin cancer, lung infection, and eye irritation. Most of them are non-biodegradable and intractable. Therefore, they can persist in the water bodies for a very long period and could be easily accumulated in our food chain system. Several pharmaceutical personal care products (PPCPs) and surfactants are available that may contain toxic compounds like nonylphenol, estrone, estradiol, and ethinylestradiol. These compounds are endocrine-disrupting chemicals (Bolong et al., 2009 ), and the existence of these compounds in the human body even in the trace amounts can be highly hazardous. Also, the occurrence of perfluorinated compounds (PFCs) in wastewater, which is toxic in nature, has been significantly reported worldwide (Templeton et al., 2009 ). Furthermore, PFCs cause severe health menaces like pre-eclampsia, birth defects, reduced human fertility (Webster, 2010 ), immunotoxicity (Dewitt et al., 2012 ), neurotoxicity (Lee & Viberg, 2013 ), and carcinogenesis (Bonefeld-Jorgensen et al., 2011 ).

4.2 Microbial Contamination

Researchers have reported serious health risks associated with the microbial contaminants in untreated wastewater. The diverse group of microorganisms causes severe health implications like campylobacteriosis, diarrhea, encephalitis, typhoid, giardiasis, hepatitis A, poliomyelitis, salmonellosis, and gastroenteritis (ISDH, 2009 ; Okoh et al., 2010 ). Few bacterial species like P. aeruginosa , Salmonella typhimurium , Vibrio cholerae , G. intestinales , Legionella spp., E. coli , Shigella sonnei have been reported for the spreading of waterborne diseases, and acute illness in human being (Craun et al., 2006 ; Craun et al., 2010 ). These aforementioned microorganisms may release in the environment from municipal sewage water network, animal husbandries, or hospitals and enter the food chain via public water supply systems.

5 Wastewater Impact on Agriculture

The agriculture sector is well known for the largest user of water, accounting for nearly 70% of global water usage (Winpenny et al., 2010 ). The fact that an estimated 20 million hectares worldwide are irrigated with wastewater suggests a major source for irrigation (Ecosse, 2001 ). However, maximum wastewater that is used for irrigation is untreated (Jiménez & Asano, 2008 ; Scott et al., 2004 ). Mostly in developing countries, partially treated or untreated wastewater is used for irrigation purpose (Scott et al., 2009 ). Untreated wastewater often contains a large range of chemical contaminants from waste sites, chemical wastes from industrial discharges, heavy metals, fertilizers, textile, leather, paper, sewage waste, food processing waste, and pesticides. World Health Organization (WHO) has warned significant health implications due to the direct use of wastewater for irrigation purposes (WHO, 2006 ). These contaminants pose health risks to communities (farmers, agricultural workers, their families, and the consumers of wastewater-irrigated crops) living in the proximity of wastewater sources and areas irrigated with untreated wastewater (Qadir et al., 2010 ). Wastewater also contains a wide variety of organic compounds. Some of them are toxic or cancer-causing and have harmful effects on an embryo (Jarup, 2003 ; Shakir et al., 2016 ). The pathway of untreated wastewater used in irrigation and associated health effects are shown in Fig. 2 .

Exposure pathway representing serious health concerns from wastewater-irrigated crops

Alternatively, in developing countries, due to the limited availability of treatment facilities, untreated wastewater is discharged into the existing waterbodies (Qadir et al., 2010 ). The direct use of wastewater in agriculture or irrigation obstructs the growth of natural plants and grasses, which in turn causes the loss of biodiversity. Shuval et al. ( 1985 ) reported one of the earliest evidences connecting to agricultural wastewater reuse with the occurrence of diseases. Application of untreated wastewater in irrigation increases soil salinity, land sealing followed by sodium accumulation, which results in soil erosion. Increased soil salinity and sodium accumulation deteriorates the soil and decreases the soil permeability, which inhibits the nutrients intake of crops from the soil. These causes have been considered the long-term impact of wastewater reuse in agriculture (Halliwell et al., 2001 ). Moreover, wastewater contaminated soils are a major source of intestinal parasites (helminths—nematodes and tapeworms) that are transmitted through the fecal–oral route (Toze, 1997 ). Already known, the helminth infections are linked to blood deficiency and behavioral or cognitive development (Bos et al., 2010 ). One of the major sources of helminth infections around the world is the use of raw or partially treated sewage effluent and sludge for the irrigation of food crops (WHO, 1989 ). Wastewater-irrigated crops contain heavy metal contamination, which originates from mining, foundries, and metal-based industries (Fazeli et al., 1998 ). Exposure to heavy metals including arsenic, cadmium, lead, and mercury in wastewater-irrigated crops is a cause for various health problems. For example, the consumption of high amounts of cadmium causes osteoporosis in humans (Dickin et al., 2016 ). The uptake of heavy metals by the rice crop irrigated with untreated effluent from a paper mill has been reported to cause serious health concerns (Fazeli et al., 1998 ). Irrigating rice paddies with highly contaminated water containing heavy metals leads to the outbreak of Itai-itai disease in Japan (Jarup, 2003 ).

Owing to these widespread health risks, the WHO published the third edition of its guidelines for the safe use of wastewater in irrigating crops (WHO, 2006 ) and made recommendations for threshold contaminant levels in wastewater. The quality of wastewater for agricultural reuse have been classified based on the availability of nutrients, trace elements, microorganisms, and chemicals contamination levels. The level of contamination differs widely depending on the type of source, household sewage, pharmaceutical, chemical, paper, or textile industries effluents. The standard measures of water quality for irrigation are internationally reported (CCREM, 1987 ; FAO, 1985 ; FEPA, 1991 ; US EPA, 2004 , 2012 ; WHO, 2006 ), where the recommended levels of trace elements, metals, COD, BOD, nitrogen, and phosphorus are set at certain limits. Researchers reviewed the status of wastewater reuse for agriculture, based on its standards and guidelines for water quality (Angelakis et al., 1999 ; Brissaud, 2008 ; Kalavrouziotis et al., 2015 ). Based on these recommendations and guidelines, it is evident that greater awareness is required for the treatment of wastewater safely.

6 Wastewater Treatment Techniques

6.1 primary treatment.

This initial step is designed to remove gross, suspended and floating solids from raw wastewater. It includes screening to trap solid objects and sedimentation by gravity to remove suspended solids. This physical solid/liquid separation is a mechanical process, although chemicals can be used sometimes to accelerate the sedimentation process. This phase of the treatment reduces the BOD of the incoming wastewater by 20–30% and the total suspended solids by nearly 50–60%.

6.2 Secondary (Biological) Treatment

This stage helps eliminate the dissolved organic matter that escapes primary treatment. Microbes consume the organic matter as food, and converting it to carbondioxide, water, and energy for their own growth. Additional settling to remove more of the suspended solids then follows the biological process. Nearly 85% of the suspended solids and biological oxygen demand (BOD) can be removed with secondary treatment. This process also removes carbonaceous pollutants that settle down in the secondary settling tank, thus separating the biological sludge from the clear water. This sludge can be fed as a co-substrate with other wastes in a biogas plant to obtain biogas, a mixture of CH 4 and CO 2 . It generates heat and electricity for further energy distribution. The leftover, clear water is then processed for nitrification or denitrification for the removal of carbon and nitrogen. Furthermore, the water is passed through a sedimentation basin for treatment with chlorine. At this stage, the water may still contain several types of microbial, chemical, and metal contaminations. Therefore, to make the water reusable, e.g., for irrigation, it further needs to pass through filtration and then into a disinfection tank. Here, sodium hypochlorite is used to disinfect the wastewater. After this process, the treated water is considered safe to use for irrigation purposes. Solid wastes generated during primary and secondary treatment processes are processed further in the gravity-thickening tank under a continuous supply of air. The solid waste is then passed into a centrifuge dewatering tank and finally to a lime stabilization tank. Treated solid waste is obtained at this stage and it can be processed further for several uses such as landfilling, fertilizers and as a building.

Other than the activated sludge process of wastewater treatment, there are several other methods developed and being used in full-scale reactors such as ponds (aerobic, anaerobic, facultative, and maturation), trickling filters, anaerobic treatments like up-flow anaerobic sludge blanket (UASB) reactors, artificial wetlands, microbial fuel cells, and methanogenic reactors.

UASB reactors are being applied for wastewater treatment from a very long period. Behling et al. ( 1996 ) examined the performance of the UASB reactor without any external heat supply. In their study, the COD loading rate was maintained at 1.21 kg COD/m 3 /day, after 200 days of trial. They achieved an average of 85% of COD removal. Von-Sperling and Chernicharo ( 2005 ) presented a combined model consisted of an Up-flow Anaerobic Sludge Blanket-Activated Sludge reactor (UASB–AS system), using the low strength domestic wastewater with a BOD 5 amounting to 340 mg/l. Outcomes of their experiment have shown a 60% reduction in sludge construction and a 40% reduction in aeration energy consumption. In another experiment, Rizvi et al. ( 2015 ) seeded UASB reactor with cow manure dung to treat domestic wastewater; they observed 81%, 75%, and 76% reduction in COD, TSS, and total sulfate removal, respectively, in their results.

6.3 Tertiary or Advanced Treatment Processes

The tertiary treatment process is employed when specific constituents, substances, or contaminants cannot be completely removed after the secondary treatment process. The tertiary treatment processes, therefore, ensure that nearly 99% of all impurities are removed from wastewater. To make the treated water safe for drinking purposes, water is treated individually or in combination with advanced methods like the US (ultrasonication), UV (ultraviolet light treatment), and O 3 (exposure to ozone). This process helps to remove bacteria and heavy metal contaminations remaining in the treated water. For the purpose, the secondarily treated water is first made to undergo ultrasonication and it is subsequently exposed to UV light and passed through an ozone chamber for the complete removal of contaminations. The possible mechanisms by which cells are rendered inviable during the US include free-radical attack and physical disruption of cell membranes (Phull et al., 1997 ; Scherba et al., 1991 ). The combined treatment of US + UV + O 3 produces free radicals, which are attached to cell membranes of the biological contaminants. Once the cell membrane is sheared, chemical oxidants can enter the cell and attack internal structures. Thus, the US alone or in combination facilitates the deagglomeration of microorganisms and increases the efficiency of other chemical disinfectants (Hua & Thompson, 2000 ; Kesari et al., 2011a , b ; Petrier et al., 1992 ; Phull et al., 1997 ; Scherba et al., 1991 ). A combined treatment method was also considered by Pesoutova et al. ( 2011 ) and reported a very effective method for textile wastewater treatment. The effectiveness of ultrasound application as a pre-treatment step in combination with ultraviolet rays (Blume & Neis, 2004 ; Naddeo et al., 2009 ), or also compared it with various other combinations of both ultrasound and UV radiation with TiO 2 photocatalysis (Paleologou et al., 2007 ), and ozone (Jyoti & Pandit, 2004 ) to optimize wastewater disinfection process.

An important aspect of our wastewater treatment model (Fig. 3 ) is that at each step of the treatment process, we recommend the measurement of the quality of treated water. After ensuring that the proper purification standards are met, the treated water can be made available for irrigation, drinking or other domestic uses.

A wastewater treatment schematic highlighting the various methods that result in a progressively improved quality of the wastewater from the source to the intended use of the treated wastewater for irrigation purposes

6.4 Nanotechnology as Tertiary Treatment of Wastewater Converting Drinking Water Alike

Considering the emerging trends of nanotechnology, nanofillers can be used as a viable method for the tertiary treatment of wastewater. Due to the very small pore size, 1–5-nm nanofillers may eliminate the organic–inorganic pollutants, heavy metals, as well as pathogenic microorganisms and pharmaceutically active compounds (PhACs) (Mohammad et al., 2015 ; Vergili, 2013 ). Over the recent years, nanofillers have been largely accepted in the textile industry for the treatment of pulp bleaching pharmaceutical industry, dairy industry, microbial elimination, and removal of heavy metals from wastewater (Abdel-Fatah, 2018 ). Srivastava et al. ( 2004 ) synthesized very efficient and reusable water filters from carbon nanotubes, which exhibited effective elimination of bacterial pathogens ( E. coli and S. aureus ), and Poliovirus sabin-1 from wastewater.

Nanofiltration requires lower operating pressure and lesser energy consumption in comparison of RO and higher rejection of organic compounds compared to UF. Therefore, it can be applied as the tertiary treatment of wastewater (Abdel-Fatah, 2018 ). Apart from nanofilters, there are various kinds of nanoparticles like metal nanoparticles, metal oxide nanoparticles, carbon nanotubes, graphene nanosheets, and polymer-based nanosorbents, which may play a different role in wastewater treatment based on their properties. Kocabas et al. ( 2012 ) analyzed the potential of different metal oxide nanoparticles and observed that nanopowders of TiO 2 , FeO 3 , ZnO 2 , and NiO can exhibit the exceeding amount of removal of arsenate from wastewater. Cadmium contamination in wastewater, which poses a serious health risk, can be overcome by using ZnO nanoparticles (Kumar & Chawla, 2014 ). Latterly, Vélez et al. ( 2016 ) investigated that the 70% removal of mercury from wastewater through iron oxide nanoparticles successfully performed. Sheet et al. ( 2014 ) used graphite oxide nanoparticles for the removal of nickel from wastewater. An exceeding amount of copper causes liver cirrhosis, anemia, liver, and kidney damage, which can be removed by carbon nanotubes, pyromellitic acid dianhydride (PMDA) and phenyl aminomethyl trimethoxysilane (PAMTMS) (Liu et al., 2010 ).

Nanomaterials are efficiently being used for microbial purification from wastewater. Carbon nanotubes (CNTs) are broadly applied for the treatment of wastewater contaminated with E. coli , Salmonella , and a wide range of microorganisms (Akasaka & Watari, 2009 ). In addition, silver nanoparticles reveal very effective results against the microorganisms present in wastewater. Hence, it is extensively being used for microbial elimination from wastewater (Inoue et al., 2002 ). Moreover, CNTs exhibit high binding affinity to bacterial cells and possess magnetic properties (Pan & Xing, 2008 ). Melanta ( 2008 ) confirmed and recommended the applicability of CNTs for the removal of E. coli contamination from wastewater. Mostafaii et al. ( 2017 ) suggested that the ZnO nanoparticles could be the potential antibacterial agent for the removal of total coliform bacteria from municipal wastewater. Apart from the previously mentioned, applicability of the nanotechnology, the related drawbacks and challenges cannot be neglected. Most of the nanoengineered techniques are currently either in research scale or pilot scale performing well (Gehrke et al., 2015 ). Nevertheless, as discussed above, nanotechnology and nanomaterials exhibit exceptional properties for the removal of contaminants and purification of water. Therefore, it can be adapted as the prominent solution for the wastewater treatment (Zekić et al., 2018 ) and further use for drinking purposes.

6.5 Wastewater Treatment by Using Plant Species

Some of the naturally growing plants can be a potential source for wastewater treatment as they remove pollutants and contaminants by utilizing them as a nutrient source (Zimmels et al., 2004 ). Application of plant species in wastewater treatment may be cost-effective, energy-saving, and provides ease of operation. At the same time, it can be used as in situ, where the wastewater is being produced (Vogelmann et al., 2016 ). Nizam et al. ( 2020 ) analyzed the phytoremediation efficiency of five plant species ( Centella asiatica , Ipomoea aquatica , Salvinia molesta , Eichhornia crassipes , and Pistia stratiotes ) and achieved the drastic decrease in the amount of three pollutants viz. total suspended solids (TSS), ammoniacal nitrogen (NH 3 -N), and phosphate levels . All the five species found to be efficient removal of the level of 63.9-98% of NH 3 -N, TSS, and phosphate. Coleman et al. ( 2001 ) examined the physiological effects of domestic wastewater treatment by three common Appalachian plant species: common rush or soft rush ( Juncus effuses L.), gray club-rush ( Scirpus Validus L.), and broadleaf cattail or bulrush ( Typha latifolia L.). They observed in their experiments about 70% of reduction in total suspended solids (TSS) and biochemical oxygen demand (BOD), 50% to 60% of reduction in nitrogen, ammonia, and phosphate levels, and a significant reduction in feacal coliform populations. Whereas, Zamora et al. ( 2019 ) found the removal efficiency of chemical oxygen demand (COD), total solids suspended (TSS), nitrogen as ammonium (N-NH 4 ) and nitrate (N-NO 3 ), and phosphate (P-PO 4 ) up to 20–60% higher using the three ornamental species of plants viz. Canna indica , Cyperus papyrus , and Hedychium coronarium . The list of various plant species applied for the wastewater treatment is shown in Table 3 .

6.6 Wastewater Treatment by Using Microorganisms

There is a diverse group of bacteria like Pseudomonas fluorescens , Pseudomonas putida , and different Bacillus strains, which are capable to use in biological wastewater systems. These bacteria work in the cluster forms as a floc, biofilm, or granule during the wastewater treatment. Furthermore, after the recognition of bacterial exopolysaccharides (EPS) as an efficient adsorption material, it may be applied in a revolutionary manner for the heavy metal elimination (Gupta & Diwan, 2017 ). There are few examples of EPS, which are commercially available, i.e., alginate ( P. aeruginosa , Azotobacter vinelandii ), gellan (Sphingomonas paucimobilis ), hyaluronan ( . aeruginosa , Pasteurella multocida , Streptococci attenuated strains ), xanthan (Xanthomonas campestris ), and galactopol ( Pseudomonas oleovorans ) (Freitas et al., 2009 ; Freitas, Alves, & Reis, 2011a ; Freitas, Alves, Torres, et al., 2011b ). Similarly, Hesnawi et al. ( 2014 ) experimented biodegradation of municipal wastewater using local and commercial bacteria (Sludge Hammer), where they achieved a significant decrease in synthetic wastewater, i.e., 70%, 54%, 52%, 42% for the Sludge Hammer, B. subtilis , B. laterosponus , and P. aeruginosa , respectively. Therefore, based on the above studies, it can be concluded that bioaugmentation of wastewater treatment reactor with selective and mixed strains can ameliorate the treatment. During recent years, microalgae have attracted the attention of researchers as an alternative system, due to their applicability in wastewater treatment. Algae are the unicellular or multicellular photosynthetic microorganism that grows on water surfaces, salt water, or moist soil. They utilize the exceeding amount of nutrients like nitrogen, phosphorus, and carbon for their growth and metabolism process through their anaerobic system. This property of algae also inhibits eutrophication; that is to avoid over-deposit of nutrients in water bodies. During the nutrient digestion process, algae produce oxygen that is constructive for the heterotrophic aerobic bacteria, which may further be utilized to degrade the organic and inorganic pollutants. Kim et al. ( 2014 ) observed a total decrease in the levels of COD (86%), total nitrogen (93%), and total phosphorus (83%) after using algae in the municipal wastewater consortium. Nmaya et al. ( 2017 ) reported the heavy metal removal efficiency of microalga Scenedesmus sp. from contaminated river water in the Melaka River, Malaysia. They observed the effective removal of Zn (97-99%) on the 3 rd and 7 th day of the experiment. The categorized list of microorganisms used for wastewater treatment is presented in Table 4 .

7 The Computational Approach in Wastewater Treatment

7.1 bioinformatics and genome sequencing.

A computational approach is accessible in wastewater treatment. Several tools and techniques are in use such as, sequencing platforms (Hall, 2007 ; Marsh, 2007 ), metagenome sequencing strategies (Schloss & Handelsman, 2005 ; Schmeisser et al., 2007 ; Tringe et al., 2005 ), bioinformatics tools and techniques (Chen & Pachter, 2005 ; Foerstner et al., 2006 ; Raes et al., 2007 ), and the genome analysis of complex microbial communities (Fig. 4 ). Most of the biological database contains microorganisms and taxonomical information. Thus, these can provide extensive details and supports for further utilization in wastewater treatment–related research and development (Siezen & Galardini, 2008 ). Balcom et al. ( 2016 ) explored that the microbial population residing in the plant roots immersed in the wastewater of an ecological WWTP and showed the evidence of the capacity for micro-pollutant biodegradation using whole metagenome sequencing (WMS). Similarly, Kumar et al. ( 2016 ) revealed that bioremediation of highly polluted wastewater from textile dyes by two novel strains were found to highly decolorize Joyfix Red. They were identified as Lysinibacillus sphaericus (KF032717) and Aeromonas hydrophila (KF032718) through 16S rDNA analysis. More recently, Leddy et al. ( 2018 ) reported that research scientists are making strides to advance the safety and application of potable water reuse with metagenomics for water quality analysis. The application of the bio-computational approach has also been implemented in the advancements of wastewater treatment and disease detection.

A schematic showing the overall conceptual framework on which depicting the computational approach in wastewater treatment

7.2 Computational Fluid Dynamics in Wastewater Treatment

In recent years, computational fluid dynamics (CFD), a broadly used method, has been applied to biological wastewater treatment. It has exposed the inner flow state that is the hydraulic condition of a biological reactor (Peng et al., 2014 ). CFD is the application of powerful predictive modeling and simulation tools. It may calculate the multiple interactions between all the water quality and process design parameters. CFD modeling tools have already been widely used in other industries, but their application in the water industry is quite recent. CFD modeling has great applications in water and wastewater treatment, where it mechanically works by using hydrodynamic and mass transfer performance of single or two-phase flow reactors (Do-Quang et al., 1998 ). The level of CFD’s capability varies between different process units. It has a high frequency of application in the areas of final sedimentation, activated sludge basin modeling, disinfection, and greater needs in primary sedimentation and anaerobic digestion (Samstag et al., 2016 ). Now, researchers are enhancing the CFD modeling with a developed 3D model of the anoxic zone to evaluate further hydrodynamic performance (Elshaw et al., 2016 ). The overall conceptual framework and the applications of the computational approach in wastewater treatment are presented in Fig. 4 .

7.3 Computational Artificial Intelligence Approach in Wastewater Treatment

Several studies were obtained by researchers to implement computer-based artificial techniques, which provide fast and rapid automated monitoring of water quality tests such as BOD and COD. Recently, Nourani et al. ( 2018 ) explores the possibility of wastewater treatment plant by using three different kinds of artificial intelligence methods, i.e., feedforward neural network (FFNN), adaptive neuro-fuzzy inference system (ANFIS), and support vector machine (SVM). Several measurements were done in terms of effluent to tests BOD, COD, and total nitrogen in the Nicosia wastewater treatment plant (NWWTP) and reported high-performance efficiency of artificial intelligence (Nourani et al., 2018 ).

7.4 Remote sensing and Geographical Information System

Since the implementation of satellite technology, the initiation of new methods and tools became popular nowadays. The futuristic approach of remote sensing and GIS technology plays a crucial role in the identification and locating of the water polluted area through satellite imaginary and spatial data. GIS analysis may provide a quick and reasonable solution to develop atmospheric correction methods. Moreover, it provides a user-friendly environment, which may support complex spatial operations to get the best quality information on water quality parameters through remote sensing (Ramadas & Samantaray, 2018 ).

8 Applications of Treated Wastewater

8.1 scope in crop irrigation.

Several studies have assessed the impact of the reuse of recycled/treated wastewater in major sectors. These are agriculture, landscapes, public parks, golf course irrigation, cooling water for power plants and oil refineries, processing water for mills, plants, toilet flushing, dust control, construction activities, concrete mixing, and artificial lakes (Table 5 ). Although the treated wastewater after secondary treatment is adequate for reuse since the level of heavy metals in the effluent is similar to that in nature (Ayers & Westcot, 1985 ), experimental evidences have been found and evaluated the effects of irrigation with treated wastewater on soil fertility and chemical characteristics, where it has been concluded that secondary treated wastewater can improve soil fertility parameters (Mohammad & Mazahreh, 2003 ). The proposed model (Fig. 3 ) is tested partially previously at a laboratory scale by treating the wastewater (from sewage, sugar, and paper industry) in an ultrasonic bath (Kesari et al., 2011a , b ; Kesari & Behari, 2008 ; Kumar et al., 2010 ). Advancing it with ultraviolet and ozone treatment has modified this in the proposed model. A recent study shows that the treated water passed quality measures suited for crop irrigation (Bhatnagar et al., 2016 ). In Fig. 3 , a model is proposed including all three (UV, US, nanoparticle, and ozone) techniques, which have been tested individually as well as in combination (US and nanoparticle) (Kesari et al., 2011a , b ) to obtain the highest water quality standards acceptable for irrigation and even drinking purposes.

A wastewater-irrigated field is a major source of essential and non-essential metals contaminants such as lead, copper, zinc, boron, cobalt, chromium, arsenic, molybdenum, and manganese. While crops need some of these, the others are non-essential metals, toxic to plants, animals, and humans. Kanwar and Sandha ( 2000 ) reported that heavy metal concentrations in plants grown in wastewater-irrigated soils were significantly higher than in plants grown in the reference soil in their study. Yaqub et al. ( 2012 ) suggest that the use of US is very effective in removing heavy or toxic metals and organic pollutants from industrial wastewater. However, it has been also observed that the metals were removed efficiently, when UV light was combined with ozone (Samarghandi et al., 2007 ). Ozone exposure is a potent method for the removal of metal or toxic compounds from wastewater as also reported earlier (Park et al., 2008 ). Application of US, UV, and O 3 in combination lead to the formation of reactive oxygen species (ROS) that oxidize certain organics, metal ions and kill pathogens. In the process of advanced oxidizing process (AOP) primarily oxidants, electricity, light, catalysts etc. are implied to produce extremely reactive free radicals (such as OH) for the breakdown of organic matters (Oturan & Aaron, 2014 ). Among the other AOPs, ozone oxidization process is more promising and effective for the decomposition of complex organic contaminants (Xu et al., 2020 ). Ozone oxidizes the heavy metal to their higher oxidation state to form metallic oxides or hydroxides in which they generally form limited soluble oxides and gets precipitated, which are easy to be filtered by filtration process. Ozone oxidization found to be efficient for the removal of heavy metals like cadmium, chromium, cobalt, copper, lead, manganese, nickel, and zinc from the water source (Upadhyay & Srivastava, 2005 ). Ultrasonic-treated sludge leads to the disintegration of biological cells and kills bacteria in treated wastewater (Kesari, Kumar, et al., 2011a ; Kesari, Verma, & Behari, 2011b ). This has been found that combined treatment with ultrasound and nanoparticles is more effective (Kesari, Kumar, et al., 2011a ). Ultrasonication has the physical effects of cavitation inactivate and lyse bacteria (Broekman et al., 2010 ). The induced effect of US, US, or ozone may destroy the pathogens and especially during ultrasound irradiation including free-radical attack, hydroxyl radical attack, and physical disruption of cell membranes (Kesari, Kumar, et al., 2011a ; Phull et al., 1997 ; Scherba et al., 1991 ).

8.2 Energy and Economy Management

Municipal wastewater treatment plants play a major role in wastewater sanitation and public health protection. However, domestic wastewater has been considered as a resource or valuable products instead of waste, because it has been playing a significant role in the recovery of energy and resource for the plant-fertilizing nutrients like phosphorus and nitrogen. Use of domestic wastewater is widely accepted for the crop irrigation in agriculture and industrial consumption to avoid the water crisis. It has also been found as a source of energy through the anaerobic conversion of the organic content of wastewater into methane gas. However, most of the wastewater treatment plants are using traditional technology, as anaerobic sludge digestion to treat wastewater, which results in more consumption of energy. Therefore, through these conventional technologies, only a fraction of the energy of wastewater has been captured. In order to solve these issues, the next generation of municipal wastewater treatment plants is approaching total retrieval of the energy potential of water and nutrients, mostly nitrogen and phosphorus. These plants also play an important role in the removal and recovery of emerging pollutants and valuable products of different nature like heavy and radioactive metals, fertilizers hormones, and pharma compounds. Moreover, there are still few possibilities of improvement in wastewater treatment plants to retrieve and reuse of these compounds. There are several methods under development to convert the organic matter into bioenergy such as biohydrogen, biodiesel, bioethanol, and microbial fuel cell. These methods are capable to produce electricity from wastewater but still need an appropriate development. Energy development through wastewater is a great driver to regulate the wastewater energy because it produces 10 times more energy than chemical, thermal, and hydraulic forms. Vermicomposting can be utilized for stabilization of sludge from the wastewater treatment plant. Kesari and Jamal ( 2017 ) have reported the significant, economical, and ecofriendly role of the vermicomposting method for the conversion of solid waste materials into organic fertilizers as presented in Fig. 5 . Solid waste may come from several sources of municipal and industrial sludge, for example, textile industry, paper mill, sugarcane, pulp industry, dairy, and intensively housed livestock. These solid wastes or sewage sludges have been treated successfully by composting and/or vermicomposting (Contreras-Ramos et al., 2005 ; Elvira et al., 1998 ; Fraser-Quick, 2002 ; Ndegwa & Thompson, 2001 ; Sinha et al., 2010 ) Although collection of solid wastes materials from sewage or wastewater and further drying is one of the important concerns, processing of dried municipal sewage sludge (Contreras-Ramos et al., 2005 ) and management (Ayilara et al., 2020 ) for vermicomposting could be possible way of generating organic fertilizers for future research. Vermicomposting of household solid wastes, agriculture wastes, or pulp and sugarcane industry wastes shows greater potential as fertilizer for higher crop yielding (Bhatnagar et al., 2016 ; Kesari & Jamal, 2017 ). The higher amount of solid waste comes from agricultural land and instead of utilizing it, this biomass is processed by burning, which causes severe diseases (Kesari & Jamal, 2017 ). Figure 3 shows the proper utilization of solid waste after removal from wastewater; however, Fig. 5 showing greater possibility in fertilizer conversion which has also been discussed in detail elsewhere (Bhatnagar et al., 2016 ; Nagavallemma et al., 2006 )

Energy production through wastewater (reproduced from Bhatnagar et al., 2016 ; Kesari & Jamal, 2017 )

9 Conclusions and future perspectives

In this paper, we have reviewed environmental and public health issues associated with the use of untreated wastewater in agriculture. We have focused on the current state of affairs concerning the wastewater treatment model and computational approach. Given the dire need for holistic approaches for cultivation, we proposed the ideas to tackle the issues related to wastewater treatment and the reuse potential of the treated water. Water resources are under threat because of the growing population. Increasing generation of wastewater (municipal, industrial, and agricultural) in developing countries especially in India and other Asian countries has the potential to serve as an alternative of freshwater resources for reuse in rice agriculture, provide appropriate treatment, and distribution measures are adopted. Wastewater treatment is one of the big challenges for many countries because increasing levels of undesired or unknown pollutants are very harmful to health as well as environment. Therefore, this review explores the ideas based on current and future research. Wastewater treatment includes very traditional methods by following primary, secondary, and tertiary treatment procedures, but the implementation of advanced techniques is always giving us a big possibility of good water quality. In this paper, we have proposed combined methods for the wastewater treatment, where the concept of the proposed model works on the various types of wastewater effluents. The proposed model not only useful for wastewater treatment but also for the utilization of solid wastes as fertilizer. An appropriate method for the treatment of wastewater and further utilization for drinking water is the main futuristic outcome. It is also highly recommendable to follow the standard methods and available guidelines provided WHO. In this paper, the proposed role of the computational model, i.e., artificial intelligence, fluid dynamics, and GIS, in wastewater treatment could be useful in future studies. In this review, health concerns associated with wastewater irrigation for farmers and irrigated crops consumers have been discussed.

The crisis of freshwater is one of the growing concerns in the twenty-first century. Globaly, about 330 km 3 of municipal wastewater is generated annually (Hernández-Sancho et al., 2015 ). This data provides a better understanding of why the reuse of treated wastewater is important to solve the issues of the water crisis. The use of treated wastewater (industrial or municipal wastewater or Seawater) for irrigation has a better future for the fulfillment of water demand. Currently, in developing countries, farmers are using wastewater directly for irrigation, which may cause several health issues for both farmers and consumers (crops or vegetables). Therefore, it is very imperative to implement standard and advanced methods for wastewater treatment. A local assessment of the environmental and health impacts of wastewater irrigation is required because most of the developed and developing countries are not using the proper guidelines. Therefore, it is highly required to establish concrete policies and practices to encourage safe water reuse to take advantage of all its potential benefits in agriculture and for farmers.

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Acknowledgements

All the authors are highly grateful to the authority of the respective departments and institutions for their support in doing this research. The author VT would like to thank Science & Engineering Research Board, New Delhi, India (Grant #ECR/2017/001809). The Author RS is thankful to the University Grants Commission for the National Fellowship (201819-NFO-2018-19-OBC-UTT-78476).

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Kavindra Kumar Kesari and Ramendra Soni contributed equally to this work.

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Department of Applied Physics, Aalto University, Espoo, Finland

Kavindra Kumar Kesari & Janne Ruokolainen

Department of Molecular and Cellular Engineering, Sam Higginbottom University of Agriculture, Technology and Sciences, Naini, Allahabad, India

Ramendra Soni, Jonathan A. Lal & Vijay Tripathi

Department of Health Informatics, College of Public Health and Health Informatics, Qassim University, Al Bukayriyah, Saudi Arabia

Qazi Mohammad Sajid Jamal

Department of Computational Biology and Bioinformatics, Sam Higginbottom University of Agriculture, Technology and Sciences, Naini, Allahabad, India

Pooja Tripathi

Department of Biotechnology, School of Engineering & Technology, Sharda University, Greater Noida, UP, India

Niraj Kumar Jha

Department of Bioengineering, Faculty of Engineering, Integral University, Lucknow, India

Mohammed Haris Siddiqui

Department of Forestry, NERIST, Nirjuli, Arunachal Pradesh, India

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Kesari, K.K., Soni, R., Jamal, Q.M.S. et al. Wastewater Treatment and Reuse: a Review of its Applications and Health Implications. Water Air Soil Pollut 232 , 208 (2021). https://doi.org/10.1007/s11270-021-05154-8

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As part of the long-standing partnership between NASA and Google, NASA worked with Google Arts & Culture and artist Yiyun Kang to create an interactive digital experience around global freshwater resources titled “A Passage of Water.” This immersive experience leverages data from the Gravity Recovery and Climate Experiment ( GRACE) satellites and new high-resolution data from the Surface Water and Ocean Topography (SWOT) mission to illustrate how climate change is impacting Earth’s water cycle.

A digital version of “A Passage of Water” will be released online on Thursday, Nov. 30, ahead of the beginning of the United Nations’ Climate Change Conference of Parties (COP 28) in Dubai, United Arab Emirates. Google also will host a physical installation of the visualization project in the Blue Zone at COP 28.

“NASA is the U.S. space agency that provides end-to-end research about our home planet, and it is our job to inform the world about what we learn,” said Kate Calvin, NASA’s chief scientist and senior climate advisor in Washington. “Highlighting our Earth science data in the installation of ‘A Passage of Water’ is a unique way to share information, in a digestible way, around the important connection between climate change and the Earth’s water cycle.”

For six decades, NASA has been collecting data on Earth’s land, water, air, and climate. This data is used to inform decision-makers on ways to mitigate, adapt and respond to climate change. All of NASA’s Earth science data is available for scientists and the public to access in a variety of ways.

“NASA studies our home planet and its interconnected systems more than any other planet in our universe,” said Karen St. Germain, director of NASA’s Earth Science Division. “‘A Passage of Water’ provides an opportunity to highlight the public availability of SWOT data and other NASA Earth science data to tell meaningful stories, improve awareness, and help everyday people who have to make real decisions in their homes, businesses, and communities.”

A collaboration between NASA and the French space agency CNES (Centre National d’Études Spatiales), SWOT is measuring the height of nearly all water on Earth’s surface, providing one of the most detailed, comprehensive views yet of the planet’s freshwater bodies. SWOT provides insights into how the ocean influences climate change and how a warming world affects lakes, rivers, and reservoirs.

“The detail that SWOT is providing on the world’s oceans and fresh water is game-changing. We’re only just getting started with respect to data from this satellite, and I’m looking forward to seeing where the information takes us,” said Ben Hamlington, a research scientist at NASA’s Jet Propulsion Laboratory in Southern California.

The Google project also uses data from the GRACE and GRACE Follow-On missions –the former is a joint effort between NASA and the German Aerospace Center (DLR), while the latter is a collaboration between NASA and the German Research Centre for Geosciences (GFZ). GRACE tracked localized changes to Earth’s mass distribution, caused by phenomena including the movement of water across the planet from 2002 to 2017. GRACE-FO came online in 2018 and is currently in operation.

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As with GRACE before it, the GRACE-FO mission monitors changes in ice sheets and glaciers, near-surface and underground water storage, the amount of water in large lakes and rivers, as well as changes in sea level and ocean currents, providing an integrated view of how Earth’s water cycle and energy balance are evolving.

“A Passage of Water” is the most recent digital experience created under NASA’s Space Act Agreement with Google, with resulting content to be made widely available to the public free of charge on Google’s web platforms. This collaboration is part of a six-project agreement series that aims to share NASA’s content with audiences in new and engaging ways.

Learn more about SWOT, GRACE, GRACE-FO, and NASA’s Earth Science missions at:

https://science.nasa.gov/earth

To learn more about NASA Partnerships, visit:

https://www.nasa.gov/partnerships

News Media Contact

Katherine Rohloff

NASA Headquarters, Washington

202-358-1600

[email protected]

Jane J. Lee / Andrew Wang

Jet Propulsion Laboratory, Pasadena, Calif.

818-354-0307 / 626-379-6874

[email protected] / [email protected]

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