Effects of Stepwise Adjustment of C/N during the Start-Up of Submerged Membrane Bioreactors (SMBRs) on the Aerobic Denitrification of Wastewater

Round 1

Reviewer 1 Report

See attached file

Comments for author File: Comments.docx

Author Response

Dear Reviewer:

Thank you for your careful review. We have revised your comments one by one in the attachment. We hope you can check them. 

Author Response File: Author Response.docx

Reviewer 2 Report

• In the introduction the authors reported that "Most of the previous studies focused on nitrogen removal performance, and limited studies have considered the impact of both the time of reactor start-up and membrane fouling with adjusted influent C/N ratios"- a Table with the most articles related this focus, could be added to improve this concept.
• online platform of https://www.genescloud.cn.  (include the day of availability)
• 3.1., a table for summarizing the results would be preferable
• improve the resolution of Figure 6 and 7 and 8
• improve the comments on the significance of the results and comparison to previous similar literature studies

Author Response

Dear Reviewer:

Thank you for your careful review. We have revised your comments one by one in the attachment. We hope you can check them. 

Author Response File: Author Response.docx

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

the article is interesting but the authors could be improves some parts.

The introduction can be contining a little section with comparative studies/results in literature, or similar part can be added in the conclusion/discussion to improve the novelty of this work.

The figure 7 and 8 are not clear.

 

Reviewer 2 Report

See the attached file.

Comments for author File: Comments.docx

Reviewer 3 Report

The present manuscript analyzes the effect on the N removal (denirification) establishes the adaptation of the microbiota of an SMBR to different C / N ratios compared to a non-adapted system. The authors' conclusions are that adaptation determines better levels of denitrification as a consequence of the adaptation process.

 

Unfortunately,  under my point of view the manuscript has certain problems that mean that it cannot be accepted for publication in its current form.

1. I do not see any application of these results on a real scale with particularly urban influences.
2. The experiments are carried out at 150 days of operation, reaching at the end the same C / N ratio in both reactors (R1 and R2).

What happens when the reactor takes 300 days of operation at C / N of 20? It seems clear that both reactors would act in the same way. Therefore from a real point of practical interest this work .

 

Other comments:

 

1. The ammonium concentration is very small.
2. With what inoculum are reactors put into operation?
3. Figure 2 is not easy to evaluate.What experiments are included?It would be necessary to improve the legend.
4. The concentration of N in the bioreactors is studied but it is not described in any case the concentration of organic matter.This is essential to know the real C / N ratio during all the experiment.
5. The microbiological analysis is very superficial and descriptive.Quantitative analyzes of the denitrifying and microbial populations are essential to understand the process.
6. The authors do not consider the denitrifying activity of the biofilm (adhered microorganisms) and the biomass in suspension that evidently exists in the bioreactors.

The present manuscript analyzes the effect on the N removal (denirification) establishes the adaptation of the microbiota of an SMBR to different C / N ratios compared to a non-adapted system. The authors' conclusions are that adaptation determines better levels of denitrification as a consequence of the adaptation process.

 

Unfortunately,  under my point of view the manuscript has certain problems that mean that it cannot be accepted for publication in its current form.

1. I do not see any application of these results on a real scale with particularly urban influences.
2. The experiments are carried out at 150 days of operation, reaching at the end the same C / N ratio in both reactors (R1 and R2).

What happens when the reactor takes 300 days of operation at C / N of 20? It seems clear that both reactors would act in the same way. Therefore from a real point of practical interest this work .

 

Other comments:

 

1. The ammonium concentration is very small.
2. With what inoculum are reactors put into operation?
3. Figure 2 is not easy to evaluate.What experiments are included?It would be necessary to improve the legend.
4. The concentration of N in the bioreactors is studied but it is not described in any case the concentration of organic matter.This is essential to know the real C / N ratio during all the experiment.
5. The microbiological analysis is very superficial and descriptive.Quantitative analyzes of the denitrifying and microbial populations are essential to understand the process.
6. The authors do not consider the denitrifying activity of the biofilm (adhered microorganisms) and the biomass in suspension that evidently exists in the bioreactors.