The Influence of Sulfate on Anaerobic Ammonium Oxidation in a Sequencing Batch Reactor
Round 1
Reviewer 1 Report
This manuscript describes a study to investigate the influence of sulfate on anaerobic ammonium oxidation. Specifically, the study seeks to understand the influence of influent sulfate concentration on the extend of ammonium removal. The study is interesting, but does not clearly present novel information when considering the findings of other studies cited in the manuscript. The manuscript also uses units that are not typical and language that is difficult to understand. English language and style need improvement, particularly in the Methods section.
Author Response
Author Response File: 
Author Response.pdf
Reviewer 2 Report
I go through the manuscript and found that by using two sequencing batch reactors, the authors explained the effect of sulfate ion on the anaerobic ammonium oxidation process. Authors also reported these findings by introducing to the batch reactor several chemicals such as MgSO4, NH4Cl and NaNO2. For the readers, I don't find any interesting bits or novelties. But it reflects the previous literature findings. If authors, consider a major revision and after the revision, the paper may be accepted for publication.
The following are significant issues.
## Comments on Abstract, Title and References
Abstract and title are well informed. The abstract contains a typographical mistake i.e. inline 19-20. Only 17 references have been cited in the manuscript. If possible authors may include more references.
## Comments on Introduction
The introduction part is not well informed. E.g. line 35, "Recently other phenomena of anaerobic oxidation of NH4-N were discovered". Background studies and objective is not clear here. Need improvement with more citation.
## Comments on Materials and methods
Material and method section is also not well informed. There is no report regarding the quality of effluent using in this experiment. Need a schematic for a better understanding of the process.
Why authors use MgSO4 for increasing SO42- ion concentration? I know that Mg2+ ions are responsible for making hard water.
## Comments on Results and discussions
Table 1 is not informative. Authors should include chemicals details in concentration or weight, which are added during the experiment and report of pH changes.
Line 108, “In R1, where the influent SO42- concentration was constant at 22 mg SO42-/dm” is it 22 mg SO42-/dm or 44 mg SO42-/dm? Pleases check.
It would better if the authors write chemical equations in Fig. 2.
##Comments on conclusions
The conclusion part is well written according to the result and discussion.
Author Response
Author Response File: Author Response.pdf
Reviewer 3 Report
Dear authors
an interesting study and for this I have some comments to work on:
- The introduction is very short and the main hypothesis is not well outlined.
- Fig2; here the redox state should be corrected. and the arrow colors should be explained in the legend.
- in methods the euipment is described like in sales description which is not needed and can be simplified.
minor:
- L56; "." there seems a sentence missing?
- Sulfate is clear; but I wonder why only MgSO4 was used? can u comment. Why not ammonium sulfate?
- Does chloride effect the system; typically it adds stress to bacteria in higher concentrations.
- L173 "SAA.," why a dot?
- Table 2 is not well summarized in the text; I wonder what is the main message you like to show!
Finally:
I think it is a novel aspect but the presentation is week as it not shows the novelty and the chemistry is sometimes not excat. I suggest to improve the scientific presentation and formulation.
Author Response
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I have reviewed the manuscript and found improvements in the introduction section and the experimental section. Therefore, I am happy to recommend this paper for publication in this journal. The following issues should be corrected by authors before publication.
- Resolution of Fig. 1 is not good. Please provide a high-resolution figure.
- The caption of Fig. 1 is incomplete. Please complete the “Laboratory scale system” for what.
- The caption of Table 1 needs correction. Please don’t use a formula for starting a sentence.
Best wishes….
Author Response
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript improved - still the presentation could be improved - but it is ok to contribute to the field.
Author Response
Author Response File: Author Response.pdf
