Temporal Variation of Nitrogen and Sulfur Species of Food Waste and Sludge during Anaerobic Co-Digestion
Round 1
Reviewer 1 Report
I am pleased to review the manuscript (sustainability-166965) by Kang et al., titled " Temporal Variation of N and S species of food waste and sludge during anaerobic co-digestion ".
In this manuscript, the authors investigated the Anaerobic coDigestion (AcoD) of Food Waste and Sewage Sludge at different ratios analyzing the changes of Nitrogen and Sulfur compounds and the microbial community. The results are interesting; I think that it is acceptable for publication but are requires major modifications.
Major comments:
In the Analytical Methods section (2.3): Provide details of the chromatographic column type and the operating conditions of the chromatographs. Provide details of the operating conditions of the PCR amplification of archaea and bacteria. Provide details of the manufacturer’s protocols of purification and quantification of PCR products
The richness and diversity indices must be defined in the Materials and Methods section (including equations).
All the acronyms must be defined.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The submitted article, “Temporal Variation of N and S species of food waste and sludge during anaerobic co-digestion” is interesting, original and within the scope of the journal but some changes should be addressed:
- The state-of-the art is based on 11 references and up to 47 are in the rest of manuscript. In my opinion the introduction section must be better documented by adding other new references. It will be interesting to discuss about other potential uses of sewage sludge in order to highlight your application (please see https://doi.org/10.3390/app11157139 and https://doi.org/10.37358/RC.20.10.8361).
- Please describe briefly the standards methods used for S2- measures according to reference
- Please provide the information regarding the manufacturer and the origin country of the reactants and gases used for experiments, not only for equipments.
- I recommend to use the same size and font for axes titles in figures.
- Please make figure 7 more readable.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper presents the results of a research funded by the National Key Research & Development Program of China and the Fundamental Research Funds for the Central Universities on N and S metabolism of food waste and sludge during anaerobic co-digestion. The topic of this manuscript is interesting and meaningful for two main reasons: Ammonia and sulfate are typical inhibitors for anaerobic digestion, and regulation of N and S compounds in the anaerobic digester can be a potential strategy to optimize methane production.
The paper is well written and organized. However, there are some issues that should be clarified before acceptance. Detailed comments are listed as follows:
1:Provide highlights and nice graphical abstract representing the research work.
2:Add N2 and S0 to inorganic N-forms (NO3-, NO2-, NH4+ and NH3) and inorganic S-forms (SO42-, SO32-, S2- and H2S), and give N and S mass balance of the study.
3:The conclusion of the study is not discussed with the specific output obtained from the study, it could be modified with precise outcomes.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I am pleased to review the manuscript Sustainability1666965-V2 by Kang et al., titled " Temporal Variation of Nitrogen and Sulfur species of food waste and sludge during anaerobic co-digestion ".
In this manuscript, the authors investigated the Anaerobic coDigestion (AcoD) of Food Waste and Sewage Sludge at different ratios analyzing the changes of Nitrogen and Sulfur compounds and the microbial community. The results are interesting; I think that it is already acceptable for publication with the modifications made. I only have some minor comments.
Minor comments:
In Analytical methods section (2.3):
In “Anion analysis was equipped with the SH-AC-18…..” The first letter is bold, change it to normal.
In “The eluent of ionic was consisted of 2.0 mM Na2CO3 and 10.0 mM NaHCO3. I think the word “was” can be removed.
In “ ….and the corresponding eluent of ionic was consisted of 2.0…. I think the word “was” can be removed.
In Reagent (2.4) section:
In “Standard materials used for the analysis of inorganic nitrogen and sulfue including Anion mix standard solution of SO42-, SO32-, NO3-, and NO2- (1000 mg/L), and Standard solution…. To correct the word “sulfue” and is it necessary to put the first letter of the words “Standard” and “Anion” in capital letters?
In 4. Conclusions section:
In “Accroding to the Functional pre- diction, the ureolysis, nitrate respiration, nitrogen respiration and nitrate reduction, were contributied to high NH4+, while sulfite respiration and sulfate respiration for S cycle”. Check that the words "according" and "contributed" are spelled correctly, also is it necessary to put the first letter of the word “Functional” in capital letters?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
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.
