Unlocking the Potential of Reclaimed Water: Analysis of the Challenges and Market Size as a Strategic Solution for Water Scarcity in Europe

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work presents a comprehensive analysis of the potential reuse of municipal reclaimed water in Europe, considering factors such as climate, freshwater resources, wastewater treatment capacity and technology, sectorial demand and trends, and associated risk issues. The results provide valuable insights. 

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

 

I hope this letter finds you well. I am writing to inform you that following your insightful comments and suggestions during the review phase, I have made several modifications to the manuscript. I would like to sincerely thank you for your valuable and constructive feedback on our manuscript “Unlocking the Potential of Reclaimed Water: Analysis of the Challenges and Market Size as a Strategic Solution for Water Scarcity in Europe.” Your suggestions have been extremely helpful in improving the clarity, structure, and overall quality of the paper. Below, you will find a detailed account of the changes we have implemented to address your concerns and to enhance the overall quality and clarity of our work.

 

1. Organization of Section 3

We fully agree with your valuable suggestions and have modified Section 3 accordingly.

• Section 3.1 (Water Scarcity): I have avoided duplicate information and moved content related to human-activity-based water demand into Section 3.5. This section now focuses exclusively on climate change effects and their impact on water demand.
• Section 3.2 (Freshwater Resource Availability and Use): Duplicate or overlapping content has been removed. Material related to wastewater treatment plant (WWTP) capacity and effluent reuse has been transferred to Section 3.5. This section now concentrates exclusively on freshwater resources and their sectoral use and without overlaps with Sections 3.6 and 3.6.
• Section 3.5 (Wastewater Treatment and Reuse): Following your comments, this section has been substantially expanded. It now integrates content previously scattered in Sections 3.1 and 3.6. It is dedicated to WWTP capacity, effluent reuse, and wastewater reuse potential, clearly distinguishing it from freshwater use.
• Section 3.6 (Regional Analysis): This section has been kept as a dedicated analysis of WWTP datasets, emphasizing regional variations and trends.
• Section 3.3, 3.4, and 3.7: I have also refined these subsections to improve consistency and avoid repetition.

Overall, Section 3 has been streamlined and restructured following your recommendations, leading to greater clarity and flow.

2. Conclusion as Section 4

Thank you for pointing this out. Indeed, the conclusions correspond to Section 4, not Section 3. I have corrected this mistake. While doing so, I also took the opportunity to slightly revise and strengthen the conclusions to better highlight the implications of our findings.

3. Table 1 Alignment Issue

I appreciate your observation. I have corrected the typographical error in Table 1 where the row for Luxembourg appeared misaligned. The values have now been verified and aligned correctly.

 

In addition to addressing your specific points, I have also added new paragraphs to the Introduction to provide better context, expanded the Methodology section to clarify our approach, and performed a general review of the writing and language to improve readability and consistency. The manuscript has been significantly improved in terms of research design and results performance. I am confident that these changes have substantially improved the manuscript and sincerely thank you again for your thoughtful feedback.

I greatly appreciate your valuable feedback and believe that these revisions have significantly improved our manuscript.

 

Sincerely,

Dr. Víctor Fabregat Tena

Reviewer 2 Report

Comments and Suggestions for Authors

Overall a great paper, easy to understand and very useful information related to water reuse.  Thanks for your work in this field.  

Author Response

Dear Reviewer,

I sincerely thank you for your positive evaluation and encouraging comments on the manuscript. I truly appreciate your recognition of the clarity, usefulness, and contribution of our work to the field of water reuse.

The manuscript has been improved in terms of research design and results performance. The Introduction and Conclusions have been improved to provide better context and highlight the implications of the findings, while the Methodology section has been expanded to clarify the approach and strengthen the rigor of the study. Furthermore, Section 3 (Results and Discussion) has been improved with some additional information. At the request of other reviewers, the section has also been reorganized, maintaining its overall structure but redistributing content across subsections to reduce overlaps and enhance clarity. These modifications ensure a more coherent and comprehensive discussion of the results. For your consideration, you can find attached the revised manuscript with all the suggested improvements incorporated.

Your supportive feedback is highly motivating, and we are grateful for the time and effort you dedicated to reviewing our paper.

 

Sincerely,

Dr. Víctor Fabregat Tena

Reviewer 3 Report

Comments and Suggestions for Authors

The primary objective is to assess the challenges and market potential of reclaimed water as a strategic solution to water scarcity in Europe. The manuscript combines a review of regulatory frameworks, analysis of water scarcity indicators, evaluation of reuse potential, and identification of barriers to wastewater reuse, with a strong focus on EU-wide and regional trends.

1) Speculations

Some claims lack sufficient empirical backing or rely heavily on secondary summaries without proper methodological transparency:

- Section 3.7 (Estimation of the Potential Market): Projections such as “reuse could increase sixfold” lack precise methodology or sensitivity analysis, making the forecast speculative.

- Conclusion (Lines 673–697): Although based on cited data, some affirmations (e.g., reuse will become a “key pillar” for SDGs) could benefit from a more nuanced or conditional tone.

2) Coherence of Title, Keywords, Abstract, and Conclusions

- Title: Accurate and descriptive.

- Keywords: Adequate, although missing terms like “emerging contaminants” or “regulatory innovation”.

- Abstract: Good summary but too general; consider stating clear figures (e.g., % of underutilization).

- Conclusions: In tune with the main text, though slightly repetitive and idealistic.

3) Introduction

- Objectives should be here, not in the Methodology section.

- Suggested sentence for clarity on objectives:
"This study aims to quantify the underexploited market potential for reclaimed water in the EU and identify regulatory and technological pathways to accelerate its adoption."

- Suggested sentence for novelty:
"Unlike prior works focused solely on water reuse technologies or policy reviews, this study integrates geospatial treatment data, legislative analysis, and economic estimations to define regional market potential in reclaimed water."

- Include discussion on public acceptance, economic barriers, and governance frameworks, which are critical in the real-world implementation of reclaimed water solutions.

- Why were other decentralized or nature-based solutions not considered in the comparative discussion?

4) Results and Discussion

- Section 3.3: Have any quantitative risk assessments been conducted regarding pathogen and AMR gene dissemination through reuse?

- Section 3.5: Is there an economic feasibility analysis accompanying the presented water availability and reuse scenarios?

- Section 3.7: How was the potential reuse volume of 6 billion m³/year calculated? Is this based on design capacity or actual operational data?

5) Points to be Improved

- Include economic cost-benefit analyses or techno-economic case studies.

- Improve methodological transparency for projections in Section 3.7.

- Add a discussion on public acceptance, crucial to real-world uptake.

- Highlight case studies beyond Spain for better EU-wide applicability.

 

Comments on the Quality of English Language

Generally understandable, but needs revision for clarity, grammar, and style, especially:
- Misuse of articles ("the reuse", "the reclaimed water sector is poised...").
- Repetitive phrases and verbose constructions.
- Overuse of passive voice in some analytical parts.

Author Response

Dear Reviewer,

 

I hope this letter finds you well. I am writing to inform you that following your insightful comments and suggestions during the review phase, I have made several modifications to the manuscript. I would like to sincerely thank you for your valuable and constructive feedback on our manuscript “Unlocking the Potential of Reclaimed Water: Analysis of the Challenges and Market Size as a Strategic Solution for Water Scarcity in Europe.” Your suggestions have been extremely helpful in improving the clarity, structure, and overall quality of the paper. Below, you will find a detailed account of the changes we have implemented to address your concerns and to enhance the overall quality and clarity of our work.

 

• Speculations

I fully acknowledge the reviewer’s concerns regarding speculative statements. A complete revision of the document has been carried out, with particular emphasis on Section 3. In this revision, the information across subsections has been restructured to avoid overlaps or duplication, and claims lacking sufficient empirical support or relying heavily on secondary summaries without methodological transparency have either been reinforced with proper references or removed, in line with the reviewer’s recommendations. For example, the statement on reuse “increasing sixfold” has been limited to a single mention in Section 3.7, where it is now properly referenced (lines 682-685).

In addition, the Conclusions section has been carefully revised to avoid speculative statements, with changes to the wording and verb tenses to reflect a more nuanced and conditional tone.

• Coherence of Title, Keywords, Abstract, and Conclusions

I thank the reviewer for these suggestions. The Keywords have been updated to include additional relevant terms, as indicated; and the Abstract has been revised to provide clearer figures and align more closely with the main findings. As mentioned above, the Conclusions have also been reviewed to reduce repetition and avoid over-idealistic affirmations.

• Introduction

I am very grateful for the reviewer’s comments. Following the recommendations, the objectives and novelty of the study have been included in the Introduction, immediately before the regulatory review in Section 1.1.

A new paragraph has also been added (lines 109–122) discussing public acceptance, economic barriers, governance frameworks, and communication strategies. In addition, decentralized and nature-based solutions (NbS) are now briefly addressed with references in lines 78–82.

• Results and Discussion

As mentioned earlier, Section 3 has undergone a complete revision, with duplicated information removed and the content restructured for greater clarity. In Section 3.3, a new paragraph has been added (lines 385–393) discussing risk assessment, including references to relevant studies. Similarly, as stated above, speculative claims such as the sixfold potential have been limited, and the figure of 6 billion m³/year is now explicitly referenced to the appropriate source, with a clearer contextualization.

• Points to be Improved

I appreciate these recommendations and have implemented several improvements. Examples with economic parameters, particularly from Spain and Switzerland, have been incorporated. Section 2 (Methodology) has been expanded to more fully explain the procedures applied in Section 3, including Section 3.7.

After restructuring the content, Section 3.7 is now better contextualized and presented with greater methodological transparency. Furthermore, as mentioned earlier, the discussion on public acceptance has been included both in the Introduction and in the Conclusions (lines 757–762), where it is addressed alongside other critical aspects for large-scale adoption.

 

In addition to addressing your specific points, the language throughout the manuscript has also been carefully revised to improve clarity, consistency, and scientific tone. In this updated version, the manuscript has been significantly improved in terms of research design and results performance. We are confident that these changes have substantially improved the manuscript and sincerely thank you again for your thoughtful feedback.

 

I greatly appreciate your valuable feedback and believe that these revisions have significantly improved our manuscript.

 

Sincerely,

Dr. Víctor Fabregat Tena

Reviewer 4 Report

Comments and Suggestions for Authors

This is a timely, well-structured, and comprehensive review article on the potential of reclaimed water to address water scarcity in Europe. The manuscript makes a valuable contribution to the field by combining a detailed regulatory overview with technical, economic, and environmental perspectives on wastewater reuse. Its clarity of writing is commendable, and the text is rich in data, well-supported by up-to-date references. The paper effectively captures the urgency of water reuse in the context of climate change and resource scarcity, offering practical insights aligned with EU regulations and sustainability goals. One of its major strengths lies in its comprehensive scope, which coherently addresses regulatory, technological, environmental, and market dimensions. The regulatory analysis is particularly strong, providing an accurate and timely review of key EU directives, including Regulation (EU) 2020/741 and Directive (EU) 2024/3019. The segmentation of the market by European regions and assessment of wastewater reuse potential are methodologically sound and highly relevant for policy and investment planning. Figures and tables are used effectively to support key arguments and illustrate regional disparities.

However, several areas could be improved to enhance the manuscript’s clarity and overall impact. The methodology section (Section 2) would benefit from more detail regarding the data sources (e.g., Eurostat, WISE), calculation methods, and any underlying assumptions or limitations. This would strengthen the transparency and reproducibility of the analysis. Additionally, while the manuscript thoroughly addresses technical and regulatory challenges, it lacks discussion of public acceptance and the communication strategies needed to build trust in reclaimed water, which are critical for wider adoption. From a stylistic standpoint, some sentences are overly long or contain minor grammatical and typographical errors (e.g., “Europe countries could stablish a global standard”), which should be corrected. A final round of careful proofreading is recommended to improve sentence structure, grammar, and clarity throughout the manuscript.

Moreover, attention should be given to visual consistency: figures should be labeled using uniform fonts and styles, and all acronyms (e.g., IAS, TT, ST) should be defined at first use. Lastly, the repetition of certain statistics—particularly the reference to the “sixfold reuse potential”—should be avoided by consolidating these points into a single clear statement. With these minor revisions, the manuscript will offer an even stronger and more compelling contribution to the growing body of literature on sustainable water management in Europe.

 

Author Response

Dear Reviewer,

 

I hope this letter finds you well. I am writing to inform you that following your insightful comments and suggestions during the review phase, I have made several modifications to the manuscript. I would like to sincerely thank you for your valuable and constructive feedback on our manuscript “Unlocking the Potential of Reclaimed Water: Analysis of the Challenges and Market Size as a Strategic Solution for Water Scarcity in Europe.” Your suggestions have been extremely helpful in improving the clarity, structure, and overall quality of the paper. Below, you will find a detailed account of the changes we have implemented to address your concerns and to enhance the overall quality and clarity of our work.

 

• Methodology (Section 2)

The methodology section has been expanded to provide a more detailed explanation of each subsection of Section 3. In addition, Section 3 itself has been restructured to avoid duplications, improve storytelling, and enhance both transparency and reproducibility of the analysis. The subsections have been updated to clarify methods, contextualize results, and provide a more comprehensive understanding of the study.

• Public acceptance and communication strategies

I acknowledge the importance of this aspect. A dedicated paragraph has been added to the Introduction (lines 109–122) discussing public acceptance, economic barriers, governance frameworks, and communication strategies. Furthermore, the Conclusions now include additional text (lines 757–762) explicitly addressing these issues alongside other critical factors for large-scale adoption.

• Language and writing

The language throughout the manuscript has been carefully revised to improve clarity, consistency, and scientific tone. Overly long sentences and minor grammatical issues have been corrected. In this updated version, the manuscript has been significantly improved in terms of research design and presentation of results.

I am confident that these changes have substantially strengthened the quality and readability of the paper, and I sincerely thank the reviewer for this valuable recommendation.

 

 

• Visual consistency and acronyms

Acronyms are now introduced and defined at their first occurrence in the text, and an abbreviations list has been included at the end of the manuscript to ensure clarity for the reader.

• Avoiding redundancy and speculative claims

As noted by the reviewer, the manuscript previously included some repetition and overly assertive statements. In this revision, information across the subsections of Section 3 has been reorganized to remove overlaps and improve coherence. Claims lacking sufficient empirical backing or relying too heavily on secondary summaries without methodological transparency have been either removed or reinforced with proper references. For example, the statement on reuse “increasing sixfold” has been limited to a single mention in Section 3.7, where it is now properly referenced (lines 682-685).

Additionally, the Conclusions section has been revised to avoid speculative language, with adjustments to wording and verb tenses to reflect a more conditional and evidence-based tone.

 

I am confident that these changes have substantially improved the manuscript. I greatly appreciate your valuable feedback and believe that these revisions have significantly improved our manuscript.

 

Sincerely,

Dr. Víctor Fabregat Tena

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The revised manuscript is of much better quality.