Online Storage Technology of the Separate Sewage System: Demonstration Study in a Typical Plain River Network City

Round 1

Reviewer 1 Report

In plain river network area, due to frequent rainfall and high groundwater level, sewage pipes have a large amount of infiltration and inflow （I/I）, and high water level operation is common. Aiming at this problem in the sewage system of Suzhou City, this paper studies the on-line regulation and storage technology, and tries to reduce the operating water level by using the regulation and storage capacity of the sewage system. The research has important reference and application value. However, the article has the following problems that need to be modified or supplemented:

1. In the introduction part, it is necessary to add a discription of the research status and existing problems of online regulation and storage of sewage system at home and abroad;

2. The description of research methods in the article needs to be further refined. For example, for typical areas, the amount of I/I of the sewage system is evaluated on the scale of minute, hour and daily average, and the detailed measurement and calculation methods of I/I need to be supplemented. Moreover, the SWMM model is used for simulation, so it should be supplemented that which modules in the SWMM model are applied, and whether the model has correction and validation.

3. For the results of the demonstration application, it can further summarize a relatively clear scheme of on-line regulation and storage. For example, according to the rainfall situation in the weather forecast, how much rainfall needs to be evacuated in advance, and how much should the water level of the pump station in the typical area be lowered in advance?

4. The structure of the article can be further optimized.

Author Response

Dear reviewer,

Thanks very much for your valuable comments and suggestions. We have revised our paper according to your comments, please refer to the uploaded revised version. In your review report, you mainly address four main issues, we will respond to each of your comments respectively.

In the introduction part, it is necessary to add a description of the research status and existing problems of online regulation and storage of sewage system at home and abroad.

We agree that it is necessary to give a description of the current research status and knowledge gap. In the revised version section 1 Introduction, we supplement a thorough literature review; especially we point out the research status and existing problems.

The description of research methods in the article needs to be further refined. For example, for typical areas, the amount of I/I of the sewage system is evaluated on the scale of minute, hour and daily average, and the detailed measurement and calculation methods of I/I need to be supplemented. Moreover, the SWMM model is used for simulation, so it should be supplemented that which modules in the SWMM model are applied, and whether the model has correction and validation.

We admit the methodology was not clearly described in the initial version. In the revised version, we described the methodology in great details, including measurement and quantification methods for infiltration and inflow(I/I), sampling strategies, SWMM modules utilized, model calibration, etc., please refer to the section 2 Methodology in the revised version.

For the results of the demonstration application, it can further summarize a relatively clear scheme of on-line regulation and storage. For example, according to the rainfall situation in the weather forecast, how much rainfall needs to be evacuated in advance, and how much should the water level of the pump station in the typical area be lowered in advance?

We agree it is a very precious suggestion. However, in our current research, the aim of storage capacity evaluation is to identify the storage capacity of each pumping area, which would provide hints about where to convey the sewage during peak-time discharge and precipitation. The current result could meet the sewage operational demand and requirements to some extent. Next step we will be dedicated to a more specific storage capacity research with various precipitation. In such way, in terms of sewage pre-emptying, we would achieve a more detailed online storage scheduling scheme. We also included this suggestion in the revised version, please refer to section 4 Discussion.

The structure of the article can be further optimized.

We admit the previous structure was not clear enough. We have restructured it into five parts in the revised version, which are Introduction, Methodology, Results, Discussion and Conclusion. 

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors,

I regret to inform you that after reading your submission I found it not suitable for publication on Water.

The reason is that you presented a case study that could be of interest for a local journal, but not for a larger international audience as that one of Water.

You correctly presented and described your study, but you failed in contextualizing it in a broader frame, namely introducing the general scientific question (supported by an adequate bibliography) and explaining in which way your results are improving the general scientific knowledge on the topic.

As it is, the submission seems more a technical report illustrating the functioning of a sewage, although well written, than a scientific paper presenting novel  information useful for similar applications in other part of the world.

Finally, the reference list is really poor, just 9 titles, 7 of which are from Chinese scholars or institutions: when presenting a reference list its internationality is mandatory, namely titles from scholars from different part of the world should be presented. If not, the paper should be proposed to a local audience.

Author Response

Dear reviewer,

Thanks very much for your valuable comments and suggestions. We have revised our paper according to your comments, please refer to the uploaded revised version. In your review report, you mainly address three main concerns, we will respond to each of them, respectively.

First, you emphasize the lack of knowledge gap. We agree that it is necessary to give a description of the current research status and point out the knowledge gap. In the revised version (section 1 Introduction), we supplement a thorough literature review; especially we give a clear introduction of the research status, existing problems, and most importantly, point out the knowledge gap.

Second, you point out there was not a generic methodology in our paper. We admit the methodology was not clearly described in the initial version. In the revised version, we described the methodology in a generic way and in great details, including measurement and quantification methods for infiltration and inflow(I/I), sampling strategies, SWMM modules utilized, model calibration, etc., in which more focus were given to the problem itself not the application status in our study area. Please refer to the section 2 Methodology in the revised version.

The third concern is the reference problem. We agree the previous reference is very poor. Therefore, as mentioned before, we supplemented a thorough literature review. Please refer to the revised version.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear Authors,

after reading the revised version of your manuscript I regret to inform you that it is still not ready for publication.

The abstract does not follow the guidelines of MDPI, and in particular no sentences framing in the general context your work are given.

The introduction was correctly extended to include the general scientific problem.

Methods are really confused, and often an incorrect terminology is adopted: sampling strategy not clear, no location of sampling points, no information about the laboratory where the analyses were carried out, no equation reported but just a very generic reference.

In data presentation the method you followed for developing the model and  the use of the data you collected remain obscure.

The same for the discussion: you wrote about differences between different period, but neither tables nor figures supporting your statements are given.

Finally, the main advances arising from your study and their potential application to other similar cases in other part of the world are given.

I attach a commented pdf with some specific comments

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thanks again for your time and precious comments. I’ve carefully thought about your advice and adjusted our paper. We believe the latest version has improved a lot with your kind advice. The detailed adjustments are specified below.

1. Line 11: The abstract needs to be restructured following the guidelines of Water. It should start with the description of the general scientific problem, followed by the description of the case study, etc. Moreover, you start with "Suzhou" without any specification about where it is located (why should we know that this is a Chinese city?).

Thanks for your good advice. We rewrote the beginning of the abstract and gave “Suzhou” a specification. Now ,the beginning of the abstract is “Due to high underground water level, frequent rainfall, and large amount of infiltration and inflow(I/I) into the sewage system, a city in plain river network region had to face a series of problems caused by high water level operation of drainage system. Suzhou, a city in the Yangtze River Delta region of China, can be a representative of cities in plain river networks, in which this research was carried out. The amount of I/I into the sewage system was evaluated and The SWMM model was used to further evaluate calculate the sewer water storage capacity under dry weather and wet weather with multi-year average rainfall…”

2. Line 73: “Xu, Wu [18]” ——Please check the style for reference citation: this is uncorrect.

Thank you for pointing out the mistake. We corrected the citation as “Xu et al. [18]”. Furthermore, we checked and revised the other reference citations in the manuscript to avoid making the same mistake.

3. Line 145: “Wusong elevation” ——Unclear. What is it?

Sorry, it is really unclear. Wusong elevation was deleted. “The average altitude of Suzhou is 4 meters above sea level” was used to replace the unclear expression.

4. Line 146: “The multi-year aver-145 age precipitation (1956~2012) is 1112 mm” ——Please add reference.

Thanks for your kind suggestion. The reference has been added as [27].

5. Line 183: “Fig.2”——Please add a scale bar.

Thanks for your kind suggestion. A scale bar was added in Fig.2.

6. Line 192: “TN, conductivity and 18O and 2H indicator” ——What is TN? An acronym must be described the first time it is used. What kind of conductivity? I suppose electrical conductivity, but it is desumed from the following text. Please specify here. If 18O and 2H are isotopes, the number must be apexes; "indicators" is ambiguous, please rephrase.

Thanks for your comments. We revised the incorrectly expressions. Now, it is described as “The water quality characteristic factors such as Total Nitrogen (TN), conductivity and stable isotope (¹⁸O and ²H) are selected……”

7. Line 194: “The equations for I/I quantification were taken from 194 Kracht [27] and Yao [28].” ——You should insert the equation; if not, it is impossible following your discussion.

Thank you for your good advice. We added the equations in the revised manuscript.

8. Line 200: “On dry weather 200 day, 24 hours of continual sampling was carried out with each sampling point 201 every 2h sampling.” ——Really confusing. Maybe you mean that you taken 12 samples (one every 2 hours for 24 hours)? Where are located the sampling points (no information about)?

Yes, you are right. The sentence has been revised as “On dry weather day, 12 samples (one every 2 hours for 24 hours) were taken.”

9. Line 203: “conventional pollutants” ——I don't know any "conventional" pollutant. Please, clarify what you mean.

Thanks for your kind advice. We removed inappropriate expressions. It has been modified to “selected water quality characteristic factors”.

10. Line 203: “conductivity” ——Conductivity is a physico-chemical property of an aqueous solution, not a pollutant.

Yes, you are right. We have corrected it.

11. Line 209: “the analytical testing should be based on the national standard method for laboratory testing” ——An anlyses should be based on a valid scientific protocol, not on a national standard.

Thank you for your kind suggestion. We added two references [29] and [30] for the analytical methods. Now, the analytical part was described as the following: “TN was determined according to the standard method [29]. For stable isotopes determination, the samples were taken with low-temperature vacuum extraction and followed with the spectroscopy for isotope analysis[30]. Portable (HACH HQ2100) or on-line (MEACOM) conductivity monitoring instrument was employed for on-site determination of the electrical conductivity.”

12. Line 223: “first groundwater wells were pumped and washed” ——What you mean with "washed"? Maybe cleaning by water pumped before sampling?

We are ashamed that the translation here is not accurate enough. We have revised this part as the following: “The groundwater monitor wells at different locations in the study area were selected. In the morning, noon and evening of typical dry days, 500ml and 50ml samples were collected respectively for the analysis of the concentration of water quality factors and the relative abundance of stable isotopes. Water sample storage and determination methods are the same as above.”

13. Line 238: “The storage and laboratory testing requirements were the as above.” ——No information about the laboratories where the analyses were carried out are given. Please, specify.

The expression here is not accurate enough. We have revised it. See the previous reply for details, please.

14. Line 240: “In this study, several dry weather days” ——Please locate on a map the position of sampling points

A map with the position of sampling points have been added as Fig.4 in the manuscript.

15. Line 246: “For the outlet, water flow and water quality monitoring points” ——See previous note

A map with the position of sampling points have been added as Fig.4 in the manuscript.

16. Line 255: “For groundwater quality, samples” ——See previous note

A map with the position of sampling points have been added as Fig.4 in the manuscript.

17. Line 258: “water (CInfiltraion in Kracht [27]’s research and Cinfil in Yao [28]’s research)” ——Please report and describe the equation.

The equations were added in the manuscript and the parameters in the equations have been described.

18. Line 261: “typical plot (Caixiang Ercun)” ——Please show on a map where this place is.

Caixiang Ercun is the S1 that is shown in the added Fig.4.

19. Line 314: “2.4. Rule-based control strategy for online storage scheduling” ——I cannot see any of the equations used for defining the rules: just a qualitative description.

Here, the rule-based control strategy is mainly adopted an experience-based manual control mode in practice. The multi-tree model of cascade pumping station ( as shown in Fig.6(a)) and the Breadth First Search ( BFS ) algorithm was been used, which can’t be described in several equations.

20. Line 487-500: All these statements are not supported by tables or graphs. You must support them with data that a reader can see for developing an independent opinion.

We have added an analysis of Figures 11 and 12 (now merged into Figures 11 (a) and (b)) to illustrate the effectiveness of the control strategies used in the three pumping stations. The data in Fig 11 can support the effectiveness of the control strategies. All the statements listed in line 487-500 are come form the operation department after they used the control strategies in about half a year.

21. Line 518: I cannot see any consideration for retrieving information useful for a general application of this study.

The separate discussion section has been deleted and we have tried to put some referential results into it.

Author Response File: Author Response.docx

Round 3

Reviewer 2 Report

Dear authors, after reading your last revised version of your manuscript I found it now quite ready for publication, after few minor revisions as indicated in the attached commented pdf

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thanks very much for your review and comments. We really appreciate your kind help in improving our paper for publication. We’ve adjusted cautiously according to your comments. The main adjustments are specified below.

1. Line 13: lack of achronym

Thanks for your good advice. We’ve added the full name of SWMM, which is the storm water management model in the revised version.

2. Line 158: too bad quality of Figure. 2

Thank you for pointing out this drawback. We’ve replaced it with a new picture with high quality.

3. Line 165: incorrect terminologies

Thanks for your kind advice. The correct terminologies have been updated in the revised version.

4. Line 262: lack of scale bar in Figure. 4

Thanks for your kind suggestion. Scale bars were added.

5. Line 357: Please add a reference.

Thanks for your kind suggestion. A reference was added.

6. Line 387 and 388: incorrect apex

Thanks for your comments. We revised the incorrect expressions.

Author Response File: Author Response.docx