A Review of Bubble Aeration in Biofilter to Reduce Total Ammonia Nitrogen of Recirculating Aquaculture System
, Camellia Panatarani 1,2, Wawan Hermawan 2,3 and I Made Joni 1,2,*Round 1
Reviewer 1 Report
This paper reviews the effects of air bubble size on microbial community of nitrifying bacteria, consequently, determine the biofilm growth and the biofilm thickness and ultimately, the efficiency of ammonia reduction. It has wide but exact coverage on the content ought to be reviewed and provides much relevance on practical application of aeration in RAS. However, some errors need to be corrected before it can be completely accepted:
1. A very serious problem in text and needs correction. Citation format is inconsistent. For example, (1) Line 74-76: Khuntia, et al....(2) Line 76-78: Another review... (3) Line 195-198: Fine bubbles... or plates [35]. Furthermore, before Line 195, there should be 34 citations, but none. Citation from [37] till [40] are absent between Line 200 and Line 230.
2. Equation (4) reads wrong on nitrate: not 4 but 3.
3. In Table 1, it should read Patents, not 'Paten'.
4. Table 2 in page 12-13. (1) I do not see how the order of Type of Aerator was followed. It should follow either ascending order or descending order of the bubble size. (2) Scientific names of RAS Culture species should be all provided. (3) Check data correctness of the third row by reference [48].
5. Same problem in the above also appears in Table 3 in page 17-18.
In conclusion, Table 2 and 3 should be very carefully checked, especially on the data.
Author Response
Dear Reviewer,
thank you for the suggestion and comment, we have attached the feedback with some revised on the manuscript.
Regards,
Authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The present manuscript reviewed the effect of bubble aeration on nitrification performance in biofilters treating RAS water.
The manuscript is intended to be a review, but it contains large amounts of text where no references are included!
In the discussion, results from different studies are lined up, but it is difficult for the reader to extract the main conclusions. The authors should make
The authors have not considered the effect of larger bubbles creating higher turbulence in the biolfilter, which can reduce the diffusion boundary layer, potentially leading to an increased flux of TAN into the biofilm and thus higher degradation rates of TAN.
Lines:
32-34 Typically, not all pollutants are removed during water treatment in RAS. Therefore, there will always be an impact on the environment.
40-41 The authors state: “…degradation of organic matter such as ammonia nitrogen.”. However, ammonia nitrogen (NH4-N) does not classify as organic matter since it doesn’t contain organic carbon.
There are almost no references in the introduction. For example in lines 71-73 numbers are reported without giving reference to it. The manuscript title says that this manuscript is a review, but why didn’t the authors include references that have been reviewed?
The referencing needs to be improved. For example in Line 74 Khuntia et al. is mentioned but the reference list is organized by numbers and not by last name of the authors that is referenced to! In the next sentence (line 76) it is written “ Another review focus(sed) on…” without giving reference to the actual work. Similarily, in line 81 it is written “A recent review reports…” without naming the actual reference.
Lines 140-183 There should be references included as well to back up what is stated.
Figures: The figures need to have a reference too, unless they have been produced by the authors.
Line 237 “nitrate oxidizing bacteria” should be “nitrite oxidizing bacteria”
Discussion: Please use past tense when reporting values from previous studies. For example “is used” should be replaced by “was used”.
In the results and discussion section, results from other studies are gathered but the authors lack to link the results and compare them with each other. It is thus difficult the read the chapter and to make conclusions from the gathered studies.
Author Response
Dear Reviewer,
thank you for the suggestion and comment, we have attached the feedback with some revised on the manuscript.
Regards,
Authors
Author Response File: Author Response.pdf
Reviewer 3 Report
The author summarized the research on bubble aeration in biofilter for RAS，and emphasized the prospect of fine bubble and nanobubble on improving biofilter performance，especially in RAS. However, the review still needs to be supplemented or modified. The suggestions are as follows:
1. This review does not explain how microorganisms absorb and utilize oxygen. Does the oxygen absorbed by microorganisms come directly from bubbles or from oxygen molecules in liquid phase?
2. This review quotes a lot of literature on MBBR, please analyze the pollution of excessive aeration on biofilm, and clarify under what aeration conditions the biofilm will be polluted.
3. As solids or media of different sizes and shapes have different structures, please supplement the influence of common media on microorganism attachment, including biofilm formation time, biofilm thickness, etc.
4. Bubbles have different hydrodynamic characteristics on the surface of different solid surface. Will it affect the mass transfer of oxygen?
5.This review mentioned many times that advanced aeration technology can reduce operating costs and energy savings. Please analyze the operating costs and energy consumption of typical aeration technology.
6.This review highlights an overview of bubble aeration features in a biofilter to reduce ammonia nitrogen. Therefore, it is recommended to reflect “TAN” in the title.
Author Response
Dear Reviewer,
thank you for the suggestion and comment, we have attached the feedback with some revised on the manuscript.
Regards,
Authors
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
We have browsed the author's modification opinions and carefully read the manuscript again. Here we put forward some suggestions again. It is suggested that the article can be published after modification again.
1) Lines 35-36 The authors state: “…physical, biological, and chemical processes that take place in order.” Please check the relationship between the three methods in the industrial treatment of wastewater.
2) In section 3.4 there are some inconsistent expressions, for example, kLa and kLa(T), they are not clear. Please analyze the processes of oxygen transfer from bubble to liquid and from liquid to biofilm.
Author Response
Dear Reviewer,
We have revised and response to your comment or suggestion as in attached file. Thank you
Best Regards,
Authors
Author Response File: 
Author Response.docx
