Round 1

Reviewer 1 Report

The present work aims to prove that different landscapes can offer different inspirations and possibilities to imagine a WSUD-coherent system, fulfilling the integration requirements with the urban system.  It could be considered for acceptance after modification according to the comments.

1) Abstract. Some conclusions of quantitative data need to be presented.

2）Introduction. The reason and purpose of this study need to be elaborated.

3) How to choose the main operational tools for circular water management?

4) Results. Provide more discussion content and conclusions, especially when compared with the results reported in relevant studies.

5) There are too many formatting problems, such as the presentation of figures and tables.

Extensive editing of English language required

Author Response

Caro recensore, grazie mille per i tuoi utili suggerimenti, di seguito risponderò ai punti che hai sottolineato.

1) Abbiamo aggiunto i dati più completi nell'abstract. Sfortunatamente, non abbiamo potuto ampliarlo a causa del numero di caratteri nel formato.

2) Abbiamo aggiunto il motivo e lo scopo di questo studio che potete leggere tra le righe 139-167.

3) Tra le righe 168-179 leggerete come abbiamo individuato i principali strumenti operativi della gestione circolare dell'acqua.

4) Abbiamo deciso di separare i risultati dalle conclusioni, includendo più contenuti e cercando di chiarire lo studio.

5) Abbiamo deciso di trasformare le tabelle in immagini in modo che possano essere gestite più facilmente dall'editor.

Ti ringraziamo per il suggerimento. Abbiamo fatto correggere l'articolo da un traduttore professionista.

Reviewer 2 Report

Opinion:

In this paper, the author studied the circular water management in public space. The study is focused on three different case studies and analyzed experimenting with circular water usage with no resource waste. The study concluded that a rainwater recovery system could save water up to 80-90% against the current water consumption scenario.

 

 

Strength side:

The subject treated in the manuscript is suitable for the journal. The MS is properly organized, clear, and concise. The article is developed as a high quality and scientific level. The conclusions are supported by the results. Therefore, I would recommend the manuscript to be accepted after minor revision.

Weaknesses side:

The article has no weaknesses.

Minor Revisions:

The results and conclusion sections might be separated, and it is suggested to include a discussion section in the revised version of MS.

Author Response

Dear reviewer,

thank you very much for appreciating our study.

As you suggested, we decided to unbundle the results from the conclusions, included more content, and tried to clarify the study.

Reviewer 3 Report

Introduction

This an interesting piece of work on the key problem: that of retrofitting existing developments.  It has some beautiful illustrations.  Equally, it is nice that it is prepared by a group of architects as it they who have to deliver the closed cycle approach.  The techniques involved are increasingly mainstream, and rainwater harvesting in particular has been around for millennia, as the authors noted, most famously in Venice.  Adoption has primarily however focused on new developments eg

https://www.lyon-confluence.fr/sites/default/files/media/downloads/191105%20DP%20generique%20Lyon%20Confluence.pdf

However, there are cases of city wide adoption of stormwater management:

https://stateofgreen.com/en/news/climate-change-adaptation-in-copenhagen/#video

https://www.youtube.com/watch?v=OF-9nZqKswU

I query whether Copenhagen could have done this project if car ownership rates were not so low and the proportion of travel made by other modes of transport so high.

https://www.toronto.ca/services-payments/water-environment/managing-rain-melted-snow/what-the-city-is-doing-stormwater-management-projects/other-stormwater-management-projects/#:~:text=Toronto%20Water%20manages%2C%20operates%20and,Eastern%20Beaches%20Beaches%20Detention%20Tanks.

These cases primarily focused reducing the risks of local flooding and water pollution. 

The emphasis on which arc of a closed loop approach depends on the immediate importance of that problem – as seen in the above two examples.  So a question for the authors is: why is potable water demand currently the most critical issue in the Palermo area?  Need therefore to provide some information of the projected demand-supply balances for the area.

A preliminary thought is that inventing a new name for something that already exists does not change what it is.  The paper below notes that the use of constructed wetlands to treat wastewater has a very long history.  Thus, I do not see the need to introduce the clumsy term ‘Phytodepuration’, it has not been generally used in water management for what has been going on for nearly 50 years. 

·       Land 2022, 11, 174. https://doi.org/10.3390/land11020174

Similarly, when Australia started to catch up with Germany in sustainable urban water management, authors invented the term ‘WSUD’ to add to the many others in use.

First, I would suggest that the authors include diagram showing how, based on a building, the water loop can be tightened.  

Problems in shifting to closed loop development

There are seven problems in shifting to closed loop development:

·       All physical interventions require space and the appropriate place so has exist.  For example, whilst I have a green roof and a permeable pavement, my original rain garden could not be replaced because of the changed layout of the roof drainage.  I could not install significant rainwater storage because of the impossibility of getting a large tank and digging machinery into the back garden.

·       The need to consider energy and other resource consumption and not just water.  Water is heavy and incompressible so pumping it energy intensive.

·       There are physical economies of scale so, for example, a large storage tank is cheaper than several small ones with the same total capacity.

·       Cost; this is still quite high.  I looked at the cost of rainwater storage tanks (excluding installing).  The economics are poor:

 

 

·       Retrofitting the existing stock of buildings is the real problem but this is more difficult than building water efficiency in from the start.

·       Regulations and design standards: do these exist, are the proposals compatible with current regulations?

·       Who will operate and maintain the systems?  What maintenance is required?  Who is responsible for current stormwater drainage and wastewater collection and treatment?  Will they be prepared to take responsibility for the proposed systems?

 

Case studies

·       These studies tackle the difficult side of the problem: retrofitting existing properties.  Unfortunately, this section needs more data and analysis.  To the water management reader, the first thing they want to know is: what is the pattern of rainfall over the year in these areas? Secondly, what are peak rainfall intensities?

https://nhess.copernicus.org/articles/21/2563/2021/

·       These determine what storage volume is required to provide a given daily supply and a major problem in retrofitting is finding where this storage can be placed.

·       The other questions are: what is the average domestic consumption of water?  I’m not convinced that the figure often cited for Italy of 236 l/p/d is purely for household consumption.  If it is, it is very high.  Secondly, is water scarce, has there been rationing in recent years?  Leakage losses also look high:

https://www.istat.it/it/files//2022/04/Report_ISTAT-WATER-STATISTICS.pdf

·       What charge for water is used? does it take account of high rate of leakage from the distribution system?  As reductions in potable water supply result in reductions in wastewater discharges, savings can be taken to include reductions in wastewater collection and treatment costs.

·       Can’t take average cost per person for the cost of water services but the marginal cost eg reduce demand (say) from 240 to 160, the savings is the difference between 240 times price at 240 l/p/d and 160 times price at 160 l/p/d.  What is the water and wastewater tariff in these areas?

https://tariffs.ib-net.org/ViewTariffNew?tariffId=14491&CountryId=0

·       Are there regulations in Italy concerning quality standards for wastewater (grey and black) recycling/reuse?  The lack of such regulations has been found to be a constraint on such schemes in other countries.  If they are, cite.

·      What is the breakdown of water consumption purposes in each of the three case studies?  In general, rainwater harvested water and grey water recycling is seen as limited to non-potable water uses so without data on the current patterns of water consumption, and quantities involved, it is difficult to judge whether the figures given in l413 et seq. are realistic.  If the figure of 240 l/p/d that has been quoted elsewhere is really the per capita figure for domestic consumption then the savings would be plausible since the figures in some other countries (eg Germany. Copenhagen) are around 100 l/p/d without rainwater harvesting/grey water recycling.

·      I am not engineer so I am only aware that there is a lot technical information to dimension and design the systems discussed in this paper.  The authors need to give references to the technical guidance they used to design the systems.  A couple of references I found in writing this referee’s report which looked interesting (but only skimmed) were:

o   Rainwater harvesting https://www.mdpi.com/2073-4441/15/8/1518

o   Wetlands: Water 2013, 5, 1-12; doi:10.3390/w5010001

Typos

·       L303 ‘exhaust pipes’ = down pipes?

·       L418 ‘current saving’ = ‘current usage’?

Conclusions

I’m a bit confused by the slight gaps between the listed authors, the acknowledgements and the references.  There is lot to like in this paper but from a water management perspective, there is substantial additional material before it can be published.

couple of typos listed above

Author Response

Dear reviewer,

thank you for appreciating our study, and as you pointed out, comparison with existing building stock is not always easy. Your review is very useful to our working group because it will help us in the future to consider even more aspects in the development of the research.

We have defined the current critical problem in the Palermo area, which you will find between lines 141-152.

We share with you the term "Phytodepuration," which we have replaced with natural depuration.

In the study phase, we considered most of the analyses you mention and tried to synthesize and clarify them better in the paper. To that end, we decided to unbundle the results from the conclusions, we included more content, trying to clarify the study. We specified the amount of water that can be collected from an annual precipitation. We specified how we calculated water consumption. We specified the normative references that guided us to calculate the water catchment structures and facilities.

Round 2

Reviewer 1 Report

The present revised manuscript meet the scope of the present journal, it could be accepted after minor revision as followed information.

1) The figure should be clearer.

2) Key measures should be specified in the Abstract section.

Minor editing of English language required, such as some formatting issues.

Author Response

Dear Reviewer,

1) unfortunately, we cannot edit the figures, for which a great deal of graphic work was done anyway and which, moreover, the other reviewers appreciated very much. However, we have taken your comment into account by better describing the captions so that they are clearer.

2) As you suggested, we have made the key measures explicit in the abstract.

Thank you for your suggestions.

Reviewer 3 Report

I am very torn here: I want to approve this paper as it deals with a critical problem, that of retrofitting existing developments to tighten the hydrological cycle in a climate with marked seasonal variations in rainfall, and feels like it is written by young and enthusiastic researchers.  Conversely, I don’t get the sense that they have a deep understanding of the technical issues involved in tightening the hydrological loop.  For example, I worry that if I asked: just using average daily rainfall over the year and average daily water demand over the year what would be the required dimensions of the storage tanks required to bridge the gaps I would not get an answer.  They may have the answer, but they do not give it in the paper.

On the other hand, I worry that it may be simply a cultural gap between my bias towards water management and the authors background and that their direction is more towards persuading architects and planners that sustainable water management would not result in poor quality planning and architecture?  Their emphasis on retrofitting existing development is an important one.  It may be that architects focus on building something following a brief whilst water management has to start with defining the problem.

L119 ‘Depuration’: in my original comments, I suggested that the authors avoid the use of the term – the dictionary definition is to “cleanse or purify” and when I searched google for this term, what I found was treating water for purging shellfish of contaminants. Given that English is not the first language of many readers, I strongly suggest using a term which is more usually used in water treatment rather than forcing them to consult a dictionary.  The other problem with the term is that ‘cleanse or purify’ is too strong; generally, 98% removal of a pollutant is regarded as a highly successful result.  Wetlands can be as good as standard conventional wastewater treatment. Outside of the International Space Station https://www.aquatechtrade.com/news/water-reuse/how-is-water-recycled-in-space and possibly Singapore’s Newater system, I doubt there are many cases where more than 99% removal is achieved.

L139 What I was looking for here is more like a reference to: https://www.meteoblue.com/en/weather/historyclimate/climatemodelled/palermo_italy_2523920.  In a very quick look, I did not see a reference to rainfall intensity which can exceed the infiltration capacity of permeable pavements etc.

L235 reference 16: here and elsewhere: there are several design manuals available for most of the technologies involved.  One for rainwater harvesting is:

Texas Water Development Board in cooperation with Chris Brown Consulting Jan Gerston Consulting Stephen Colley/Architecture Dr. Hari J. Krishna, P.E., Contract Manager The Texas Manual on Rainwater Harvesting Third Edition 2005 Austin, Texas

For wetlands:

UN-HABITAT, 2008. Constructed Wetlands Manual. UN-HABITAT Water for Asian

Cities Programme Nepal, Kathmandu.

Lakho, Fida Hussain, et al. “Decentralized Grey and Black Water Reuse by Combining a Vertical Flow Constructed Wetland and Membrane Based Potable Water System: Full Scale Demonstration.” JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING, vol. 9, no. 1, 2021, doi:10.1016/j.jece.2020.104688.

One of the issues is the residence time in each process, removal of pollutants takes time.  This one of the reasons why the land footprint of wetlands has to be quite large.

Typos:

L144 canals – if open channel, otherwise sewers or drains. Is the existing system a separate or combined system?

L407 ‘cisterna’ – cistern or tank

L454 ‘saving’ – current usage??????

Conclusions

In the end, I don’t feel able to make a recommendation.  From a water management perspective, it is still lacking in sufficient detail to determine whether the recommendations would actually work.  Alternatively, depending who are the readership of the journal, it might serve as an inspiration for architects and planners to look more closely at blue-green retrofits of existing developments.  However, they will then have to find guidance on how to do it elsewhere.   So, I think it is best to leave the decision to the editor.

Would I cite this paper? No. Pity because the illustrations are beautiful.

generally fine

Author Response

Dear Reviewer,

thank you for your suggestions.

Certainly we have calculated the dimensions of the tanks. Due to problems of space and synthesis we had chosen not to include the calculations we made because the real innovation is not in sizing which is a process already standardized by regulations. In our case, the innovation is being able to intervene in existing urban settings with simple actions and create circular water reuse.

On the other hand, we would not have been able to calculate the actual economic savings, which we have made explicit, if we had not sized all the systems.

In any case, we take your advice and briefly include part of the method by which we sized the tanks, a method you will find described from lines 354 to 381.

We followed your suggestions in reference to the term "purification" which we decided to replace with "remediation" since some scientific articles define it that way.

We have corrected the typos you pointed out.

We hope that the contribution will help architects, planners but also administrations especially in small municipalities to put in place actions to recover, treat and reuse wastewater.