Technology for Upgrading the Tailwater of Municipal Sewage Treatment Plants: The Efficacy and Mechanism of Microbial Coupling for Nitrogen and Carbon Removal

Round 1

Reviewer 1 Report

1. The literature review includes only 7 references, of which references 2,3,4 cite a single collective from China. I recommend adding a more profound literature review including authors from other countries.
2. The Materials and Methods section seems to be rather short and lacks the necessary information about the composition of the initial effluent. The methods and devices are not properly described, I also suggest including a scheme of the used MBR.
3. Please provide Fig.1 in better quality. The axes and labels are not readable.
4. When describing the cleaning efficiency (Figs. 1 and 2), comparison with the maximum permissible concentration (MPC) is present only for COD (standards implemented in China (effluent COD≤80 mg L-1), line 167). For the rest of the studied indicators, there is no such comparison. It is not clear whether the permissible values ​​are reached and whether it is possible to discharge the treated water into the reservoir or additional treatment is required. I recommend adding MPC values ​​for the remaining indicators from Figures 1 and 2. It should be noted that MPC depends on the type of water use (fishery, cultural, domestic, drinking), therefore, it is necessary to indicate in which water body the treated wastewater will be discharged.
5. The paper consists of 2 parts. Part 1 is devoted to the effectiveness of wastewater treatment, part 2 is devoted to the study of microbial communities involved in wastewater treatment. Part 2 is longer, the data obtained is described in detail and colorfully at a high level. For the better connection of parts 1 and 2, I recommend after Figures 1 and 2 to write due to which communities there is a sharp increase in the cleaning efficiency.
6. The paper describes biological treatment using MBR. After wastewater treatment by a biological method, waste sludge (dead microbial communities) is formed. I recommend adding how and how often it is necessary to update microbial communities and remove waste sludge.
7. Please, be accurate with abbreviations. For example, you use TN in line 61 without explanation. You also use OD and DO for dissolved oxygen. Some of the abbreviations are expanded multiple times, e.g. TC.

Author Response

Dear reviewer:

We have revised the manuscript accordingly.The modifications were marked with red color in this new version and detailed corrections are attached below point by point.

Kind regards
Hangjun Zhang

Author Response File: Author Response.docx

Reviewer 2 Report

The article presented technology for upgrading the tailwater of municipal sewage  treatment plants: the efficacy and mechanism of microbial coupling for nitrogen and carbon removal is very interesting and important due to the development of the ecological trend in environmental engineering. The materials and methods, the results were described and presented very well and precisely. However, the authors did not do without a few editing errors. Below I present my comments and questions to the author.

In the introduction, the MBR technology is very laconic, and there is little cited literature showing the use of this technology in other countries. I recommend the following article to be viewed and quoted: https://doi.org/10.3390/w12123410

Figures 1 and 2 are illegible, they should be enlarged

Figure 4 is very illegible, the subtitles are blurry, out of focus. It needs to be corrected.

References 3 and 4 are in Chinese for the reader will be incomprehensible, please replace them with items in English, the journal has an international reach.

Conclusions should be expanded and ranked, the most important achievements should be listed.

Author Response

Dear reviewer:

We have revised the manuscript accordingly.The modifications were marked with red color in this new version and detailed corrections are attached below point by point.

Kind regards
Hangjun Zhang

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I have no more comments. I accept the article for publication.