Relationship between Instant Sampling and Daily Average Values of COD for Urban Wastewater Treatment Plants in China

Round 1

Reviewer 1 Report

It is a very interesting research topic, therefore for better understanding for non professionals at least conclusion part of the article should be updated and all the relevant findings listed in a more clearly way.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Relationship between Instant Sampling and Daily Average Values of COD for Urban Wastewater Treatment Plants in China”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The main corrections in the paper and the responds to the reviewer’s comments are as following:

Comments:

It is a very interesting research topic, therefore for better understanding for non-professionals at least conclusion part of the article should be updated and all the relevant findings listed in a more clearly way.

Response:

As the Reviewer's good advice, we have updated the conclusion part of the article in a more clearly way.

Special thanks to you for your good comments.

2019-10-31

Author Response File: Author Response.pdf

Reviewer 2 Report

Please see the pdf file.

Comments for author File: Comments.pdf

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Relationship between Instant Sampling and Daily Average Values of COD for Urban Wastewater Treatment Plants in China”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The main corrections in the paper and the responds to the reviewer’s comments are as following:

Comments:

79 The basis that COD data followed log-normal distribution was according to your previous study (published in Water, 2018). However, any tests to verify the log-normal distribution hasn’t been conducted in it. The regression value in normality plot was insufficient to verify it. Some tests such as Shapiro-wilk test, Kolmogorov-Smirnov test, etc.must be used. The assumption that COD data follows log-normal distribution is the key in this paper, and then the more reliable basis should be shown. Equaton (2) the definition of variables such as ?̂ 99, ?̂ (X), X, was not described. They should be explained though they are very common in statistic field. 150 the abbreviations of technical term such as A/O, A/A/O, SBR were hard to be understand for non-specialist. 152 “depth treatment process” It is not common word. I guess that it should be “tertiary treatment process”. Table 1and Table 4. Is “Z1-0.05”correct?It meansZ0.95and the value of Z0.95is fixed to 1.65.

Response:

Thank you for the good advice. Actually we have considered using Shapiro-wilk test or Kolmogorov-Smirnov test to verify the log-normal distribution during our study; however the tests are so theoretical that asking for data with high quality which is hard to control in our data base. In our previous study, we used the plots to reflect the log-normal distribution characteristics, and the correlation coefficient of the fitting linear also gave good evidence to the lognormal distribution. Furthermore, most of the relative references confirmed that the lognormal distribution provided a reasonable and practical basis for analyzing the discharge data of some conventional pollutants. So we took the log-normal distribution as the base for our study. We are very sorry for the unclear definition in Equation (2). We have added the definitions. We are very sorry for the unclear abbreviations of technical term. We have added the definitions. We are very sorry about this. We changed the term “depth treatment process” to “tertiary treatment process”. We are very sorry about this. We changed the term “Z_1-0.05” to “Z_1-a”.

Special thanks to you for your good comments.

2019-10-31

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper deals with a methodology to find a relationship between instant sampling and daily average values of COD for urban wastewater treatment plants. The analysis is carried out by considering China as case study.

The work is interesting, well written and structured.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Relationship between Instant Sampling and Daily Average Values of COD for Urban Wastewater Treatment Plants in China”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. The main corrections in the paper and the responds to the reviewer’s comments are as following:

Comments:

The paper deals with a methodology to find a relationship between instant sampling and daily average values of COD for urban wastewater treatment plants. The analysis is carried out by considering China as case study. The work is interesting, well written and structured.

Response:

Special thanks to you for your good comments.

 

2019-10-31

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

p.3 L. 101

I required the author to show the statistical explanation to verify the log-normal distribution for COD measurement. As authors response, their data was hard to be conducted in statistical test, and instead of the test, they used log-normal plot and show the linearity by correlation coefficient. I could not understand this response because the data which could be controlled to be plotted in log-normal should also be controlled for statistical test for example, Shapiro-Wilk etc.. In addition, the assumption that COD measurement follows the log-normal distribution is the key of this paper.

The authors said also that according to previous reliable papers, COD can be assumed to follows log-normal distribution. However, almost previous papers came from USA. Then the situation maybe different in China. The authors must show the concrete and statistically verified evidence explaining the log-normal distribution assumption in their data.

 

p.5 L.181~L190

I pointed out that the explanation of this paper is not so kind to be understood for readers in first peer review. This part is typical example.

How can the daily average limit be decided. It must be different from instant sampling limit. The ratio of the daily average and instant sampling limits was defined as K value (eq. (5)). This K was decided by the data of each WWTP, not in general. Why can you conclude that the daily average (= average of instant sampling) exceeded the daily average limit which should be decided according to each WWTPs data when CORmin. was larger than assumption value of 0.222.

If instant sampling limit is 4.5 times daily average limit (= K value should be 4.5), I can understand that the daily average must exceed daily average limit always in this condition.

Maybe my understanding ability is too low to understand this result. But it shows also that only expert in this field like you can understand and others cannot.

 

p.8 L.238

The K value is defined as the ratio of VF (variability factor) of instant sampling and daily average, not values of instant sampling and daily average. It results in some conflict.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

I confirmed the correction points and added sentences and equations. They are almost good and I think that it would be helpful for readers to understand.

However, there is one points left to be unclear.

L.196~ When the instant sampling limit was 1.3 times the daily average value (the daily average = 0.7692 x instant sampling limit), daily average didn't always exceed the daily average limit because the daily average limit was set as less than 0.797 x instant sampling limit. In other words, 1.036 x daily average always exceed the daily average limit. (1.036 = 0.797/0.769)

If 0.036 of daily average should be ignored, I understand your conclusion. But it must be mentioned.

Please check it.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf