Round 1

Reviewer 1 Report

The topic of the paper is very interesting and a timely topic. However, the manuscript needs to be improved and the authors need to address these issues before it can be accepted for publication in Water.

1-  The reader would like to know the physical environment and the different water sources in the study area (i.e. especially rivers and rainfall in the areas that suffer from water scarcity and has to be supplemented with wastewater reuse).

2-   The authors need to include a methodology section in which they tell us about the methods of collection and analysis of the public and private data.

3-  The section in which the waste water treatment is explained (page 13) needs more elaboration. It needs to include examples of places where secondary and tertiary treatments took place. It would be better if this section is placed earlier (i.e. it can be included in the material of the situation of wastewater treatment in Spain (page. 2).

4-   The sub-heading (The situation of wastewater treatment and water reuse in Spain (page 2- 7) is very long which makes it very difficult for the reader to follow. It would be better to make it short under a new sub-heading (History, regulations and problems of wastewater reuse). Many of the information included in this section can be changed into a table(s) with short explanation.

5-  Finally, the reader would like to know roughly (in the conclusion) the present percentage of the contribution of the treated wastewater from all sources to the need of Spain.

Author Response

Dear editor of the Water Journal,

Please find attached:

-The manuscript showing the suggested changes by reviewers in red colour.

-The manuscript with the changes accepted (black colour).

-The 3 reviewer’s reports. As you can see we have considered all the suggestions.

Kind regards,

The authors.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper has an important information about Wastewater treatment with a general overview.

Nevertheless, the review of information could be analyzed with another perspective. I mean, water treatment cost are consider for many Authors for many kind of water exploitation, like: salinitation, purification or reuse  of wastewater.

How does this paper contribute to take a decision for reduce problems in futures scenarios, with its advantages or disadvantages?

The theoretical proposal of this paper could use all quantitative and qualitative information for a robust conclusion and recommendation of technical way for futures works.

Comments for author File: Comments.pdf

Author Response

Dear editor of the Water Journal,

Please find attached:

-The manuscript showing the suggested changes by reviewers in red colour.

-The manuscript with the changes accepted (black colour).

-The 3 reviewer’s reports. As you can see we have considered all the suggestions.

Kind regards,

The authors.

Author Response File: Author Response.docx

Reviewer 3 Report

Review of : Wastewater Treatment and Water Reuse in Spain. Current Situation and Perspectives.

The paper addresses a timely topic: how wastewater treatment should be considered as a solution to current urban water sustainability issues. Authors portray the situation of wastewater treatment and water reuse in Spain to inform the question. In my view, there is plenty of interesting information in the paper, but it needs to be presented more straightforward.

General comments

My main general comment is to work on the global narrative of the paper. Authors should define clearly their scope, and present their information regarding a central theme. Besides, it might be a manner to link the paper with a broader body of literature. I recommend elaborating from the timely question of urban water sustainability and the so-called modernization process that takes place in the European Union. Authors could reasonably argue on the need to focus on wastewater and water reuse because it is a growing challenge (Bolognesi, 2018; Ferguson et al., 2013; Hoekstra et al., 2018; Marques et al., 2015; Noiva et al., 2016).

Please, clarify all your sources and how you gathered them. Especially, tables present figure without source or information about their compilation.

Detailed comments

1. Introduction

L24-27: please, start with a more direct sentence. Why using ref [4] here as it is a review of models rather than a focus on the evolution of water demand per se? Gleick work could be of interest here.

L24: it is unclear if you mean households water demand, urban water use, or water use in general. Please clarify.

“normative” is used several times alone, please specify: normative guidance, framework, law, public policies, standards?

2. Situation of Wastewater Treatment and Water Reuse in Spain

The section is very informative.

l.75: delete commas around “among its fundamental principles.

L75-77: please refer to literature that focus on this. For instance: (Bolognesi, 2018; Kaika, 2003; Moss, 2008)

L 104-106: please clarify if 2011 refers to when the data were published or the period of measurement.

L 106: “Further” would fit better than “Thus”.

L106: Please turn it in the active voice “Figure 1 depicts the …”. Where the data come from?

Figure 1 (and all the section) is there a possibility for exemption in the implementation of the directive? If so, is the total population of your percentage include exemptions or not ?

L 120-126 please precise at the beginning of the paragraph that the year of reference is 2010.

Table 2: how are these amount distributed across the Spanish regions? Are autonomous communities included in the PNCA? If so, is the allocation of budget in table 2 related with compliance rates in table 1?

L198-l 213: more generally speaking, it is noteworthy that the water sector is the source of most of the infractions to EU environmental legislation (Bolognesi, 2014, Keller, 2011) and that it is costly.

Table 3: I would invert the last two rows/columns to facilitate the reading. For instance, the column “N° of actions” is intuitively understood as the sum of the two-upper columns about the age. I recommend making the reading more intuitive like:

Please add a caption reminding that “AGE” is the Spanish acronym for General State Administration. Besides, you may consider using GSA instead of AGE. Indeed, there is a very few references to this structure elsewhere in the manuscript (see lines: 135, 139, 234, table 3, 242, 275) and using the Spanish acronym is confusing.

Please be careful, in l.135 you refer to the State General Administration and in l. 234 you refer to General State Administration

3. Evolution of the Planned Reuse in Spain

The section is full of figures and the argument hard to follow. I recommend the author to position on the evolution observed and to present it regarding the main characteristics of change: is there a change from one model to another, how, why? A table recapitulating the key figures and stylized facts at different points of time would help a lot in following the narrative; such as does the figure 2.

A similar figure to figure 2 mapping the allocation of funds and needs would help a lot.

4 Uses of reclaimed waters in Spain

This section sounds strange to me. The geographical scope changes, with a main focus on the national level while previously the paper focused on regions. It creates a scale mismatch in the paper contributing to confuse the reader. How can we relate this section to the rest of the paper? If the authors could not clearly make this link, I recommend deleting the whole section in order to reallocate words to the understanding of the main question/purpose of the paper.

5. Costs of wastewater treatment and reuse

The modernization of water management in Europe contributes to implement a watershed based management. Are there any watershed authorities in Spain? How can they affect these costs?

Do taxes affect the costs differently among regions? In Germany, it proved to be an important factor of costs variations (see BDEW, 2011; Bolognesi, 2018; Wackerbauer and others, 2009).

Another key determinant of costs is the urban planning: how dense are cities within the region? Is there a significant urban sprawling? What is the population growth? What is the cities size and the share of urban/rural area? Mean and standard deviation of these indicators as well as linking this with the costs would significantly increase the accuracy of the analysis.

What is the source for table 5

Conclusion

The conclusion is very clear. I recommend rewriting the introduction on the same model, especially drawing on the three last paragraphs.

REFERENCES

Keller, F., 2011. Application du droit communautaire de l’environnement”, Information Report to the French Senate 20, 12 October. French Senate, Paris.

BDEW, 2011. Profile of the German Water Sector. BDEW, Bonn.

Bolognesi, T., 2018. Modernization and Urban Water Governance: Organizational Change and Sustainability in Europe. Palgrave Macmillan UK, London. https://doi.org/10.1057/978-1-137-59255-2

Bolognesi, T., 2014. The paradox of the modernisation of urban water systems in Europe: Intrinsic institutional limits for sustainability. Nat. Resour. Forum 38, 270–281. https://doi.org/10.1111/1477-8947.12052

Ferguson, B.C., Frantzeskaki, N., Brown, R.R., 2013. A strategic program for transitioning to a Water Sensitive City. Landsc. Urban Plan. 117, 32–45. https://doi.org/10.1016/j.landurbplan.2013.04.016

Hoekstra, A.Y., Buurman, J., Ginkel, K.C.H. van, 2018. Urban water security: A review. Environ. Res. Lett. 13, 053002. https://doi.org/10.1088/1748-9326/aaba52

Kaika, M., 2003. The Water Framework Directive: A New Directive for a Changing Social, Political and Economic European Framework. Eur. Plan. Stud. 11, 299–316. https://doi.org/10.1080/09654310303640

Marques, R.C., da Cruz, N.F., Pires, J., 2015. Measuring the sustainability of urban water services. Environ. Sci. Policy 54, 142–151. https://doi.org/10.1016/j.envsci.2015.07.003

Moss, B., 2008. The Water Framework Directive: Total environment or political compromise? Sci. Total Environ. 400, 32–41. https://doi.org/10.1016/j.scitotenv.2008.04.029

Noiva, K., Fernández, J.E., Wescoat, J.L., 2016. Cluster analysis of urban water supply and demand: Toward large-scale comparative sustainability planning. Sustain. Cities Soc. 27, 484–496. https://doi.org/10.1016/j.scs.2016.06.003

Wackerbauer, J., others, 2009. The water sector in Germany. CIRIEC-Université de Liège.

Author Response

Dear editor of the Water Journal,

Please find attached:

-The manuscript showing the suggested changes by reviewers in red colour.

-The manuscript with the changes accepted (black colour).

-The 3 reviewer’s reports. As you can see we have considered all the suggestions.

Kind regards,

The authors.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

This version has been improved a lot and it worth publishing in Water.

Reviewer 3 Report

I acknowledge the authors for the revised manuscript. It is much clearer making the content more pervasive and reinforcing the contribution to the literature.

Authors have taken into my previous comments. I just still recommend them to inform better the evolution of water uses.

·      There are data from Unesco

·      See the different “The World’s water” volume edited by Gleick et al.; and others Gleick’s publications may provide insights on the evolution of water uses and demand, e.g. Gleick, Peter H. "Water use." Annual review of environment and resources 28.1 (2003): 275-314.

·      Duarte, Rosa, Vicente Pinilla, and Ana Serrano. "Looking backward to look forward: water use and economic growth from a long-term perspective." Applied Economics 46.2 (2014): 212-224

I do not recommend citing all these documents but informing the trend. Including this little change, I think the paper is suitable for publication in Water.

If you have found interesting Kaika (2003), you may like reading: Allouche et al., 2008; Bolognesi, 2014; Kallis and Butler, 2001 (but are not necessary in this paper).

All the very best.

Author Response

Dear editor and reviewer of the Water journal,

As a result of the Second Round, within the revision process, please find attached:

-The new version of the paper. Document: Water-538936 (showing changes in red colour)SecondRound.

-The same version with the accepted changes. Document: Water-538936 (Accepted changes)SecondRound.

-The document: Responses to Reviewer3 (Second Round).

Kind regards,

The authors.

Author Response File: Author Response.rar