Characterization of a Moderately Halotolerant Antimony-Removing Desulfovibrio sp. Strain Isolated from Landfill Leachate
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsPaper Title: Characterization of A Moderately Halotolerant Antimony-Removing Desulfovibrio sp. Strain Isolated from Landfill Leachate.
Manuscript Number: 2684146
Article Type: Research Article
Journal Name: Water
Reviewers Comments;
This paper entitled "Characterization of A Moderately Halotolerant Antimony-Removing Desulfovibrio sp. Strain Isolated from Landfill Leachate". Authors have written manuscript which is scientifically and well-organized so, I do recommend this paper for publication after major revision. However following comments should be addressed. These comments are given below:
1. There are some grammar mistakes these should be removed from manuscript.
2. Do you perform any analysis that these species have what type of interaction with antimony and these species?
3. FTIR analysis are very helpful to explain interaction between species and Sb before and after removal of Sb.
4. Also add findings of characterization techniques briefly in abstract.
5. Also add one keyword about Antimonate removal.
6. Also add toxicity of water pollutant under study to highlight importance of your study with references.
7. In introduction you have given “Cupidesulfovibrio sp. SRB49 was unable to enzymatically reduce Sb(V) to Sb(III) but was able to remove 95 % of Sb(V) at a concentration of 100 mg/L at an initial sulfate concentration of 400 mg/L for 2 days”. Give reason and mechanism for this statement briefly.
8. Study gap should be added in introduction.
9. Also, study reusability of this specie that how much time you remove Sb again and again.
10. Add more explanation and finding in your conclusion.
11. These different articles should be very helpful for this study. Also cite these articles in revised manuscript.
“Engineering of Zirconium based metal-organic frameworks (Zr-MOFs) as efficient adsorbents”
“Biogenic synthesized nanocatalysts and their potential for the treatment of toxic pollutants: environmental remediation, a review”
Comments on the Quality of English LanguageN/A
Author Response
We are very grateful to the reviewers’ valuable and constructive suggestion. Revised parts are underlined in red in the text. Our responses are as follows:
Reviewer #1:
- There are some grammar mistakes these should be removed from manuscript.
Response: This manuscript was revised as suggested. We would appreciate it if you could point out concretely.
Do you perform any analysis that these species have what type of interaction with antimony and these species?
Response: Some bacteria in the enrichment culture may have antimony resistant activities, such as inhibiting its entrance into the cell, promoting its active extrusion from the cell if it gains entry, or achieving its sequestration in a nontoxic form within the cell. Also, some have antimony metabolic activities, such as oxidation, reduction, methylation, although our Desulfovibrio sp. has no apparent direct Sb reducing activity. Those were added in discussion on L300-304. We will perform researches on these microbial Sb biochemistry in future.
- FTIR analysis are very helpful to explain interaction between species and Sb before and after removal of Sb.
Response: FTIR is helpful for analyzing structure of organic matter and nano materials. Structure of the cell surface proteins may change before and after removal of Sb. But it is difficult for us to analyze it because the media used in this study contained not only Sb but also various chemicals with dynamically changing concentrations. We thank the reviewers’ suggestion.
Also add findings of characterization techniques briefly in abstract.
Response: In abstract, we described our findings on the Sb removal by the moderately halotolerant Desulfobvibrio at various conditions on L18-22. Also, it was added that analysis using scanning electron microscope- energy dispersive X-ray spectroscopy confirmed that the orange precipitation consisted of Sb and sulfur supposedly as Sb2S3 on L22-23.
Also add one keyword about Antimonate removal.
Response: The keyword “antimonate” was changed to “antimonate removal” on L27.
Also add toxicity of water pollutant under study to highlight importance of your study with references.
Response: Antimony is a toxic metalloid with similar toxicity and chemical properties to arsenic. They can also interfere with the enzymatic functions to break the ion balance in cells, leading to rashes, myalgia, and cancer risks. These sentences were added on L30-33.
In introduction you have given “Cupidesulfovibrio sp. SRB49 was unable to enzymatically reduce Sb(V) to Sb(III) but was able to remove 95 % of Sb(V) at a concentration of 100 mg/L at an initial sulfate concentration of 400 mg/L for 2 days”. Give reason and mechanism for this statement briefly.
Response: Cupidesulfovibrio sp. SRB49 is a typical SRB. We have already described this reason on L51-55. SRB oxidizes organic compounds by reducing sulfate to sulfide under anaerobic conditions. Subsequently, Sb(V) can be chemically reduced to Sb(III) by the sulfide formed, producing an antimony trisulfide (Sb2S3) precipitate.
Study gap should be added in introduction.
Response: The research gap between this study and former studies is mainly the effects of salinity on Sb removal by SRB, as described on L62-72.
Also, study reusability of this species that how much time you remove Sb again and again.
Response: Chemical catalysts gradually deteriorate as they are used, but Desulfovibrio sp. can grow by reducing sulfate as the electron acceptor to sulfide using lactate as the electron donor and carbon source. A typical biomass yield of a Desulfovibrio strain on lactate is 0.11 g-cell/g-C. This was added on L 313-314. If growth conditions are kept like this study, this bacterium can grow and be used for Sb removal again and again, as described on L332-333.
Add more explanation and finding in your conclusion.
Response: We added results Sb removal in the enrichment culture on L348-351.
These different articles should be very helpful for this study. Also cite these articles in revised manuscript.
“Engineering of Zirconium based metal-organic frameworks (Zr-MOFs) as efficient adsorbents”
“Biogenic synthesized nanocatalysts and their potential for the treatment of toxic pollutants: environmental remediation, a review”
Response: Thank you for your advice. But in these papers, there were no description on Sb removal by those adsorbent and nanocatalyst. I would appreciate it if you could point us the reason for citing these.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThank you very much for inviting me to review the manuscript titled “Characterization of A Moderately Halotolerant Antimony-Removing Desulfovibrio sp. Strain Isolated from Landfill Leachate”. It represents the use of a Desulfovibrio sp. strain isolated from a mixed bacterial culture derived from a leachate sample in antimony (Sb) removal from wastewater. The study objective is clear, and some comments should be addressed:
1- What are the byproducts of sulfate and antimony degradation?
2- What are the biochemical and stoichiometric reactions in these sulfate and antimony degradations?
3- What about the quality of final effluent compared with the WHO and USEPA regulations?
4- A graphical abstract can be added.
5- Highlights can also be added.
6- In the last paragraph of Introduction, clearly illustrate what has been done at work in numbering/bulletin form.
7- Plz write down the material and equipment specification and country of purchase.
8- How did you ensure the precision and accuracy of detection methods?
Comments on the Quality of English LanguageMinor editing of English language required
Author Response
Reviewer #2: Thank you very much for inviting me to review the manuscript titled “Characterization of A Moderately Halotolerant Antimony-Removing Desulfovibrio sp. Strain Isolated from Landfill Leachate”. It represents the use of a Desulfovibrio sp. strain isolated from a mixed bacterial culture derived from a leachate sample in antimony (Sb) removal from wastewater. The study objective is clear, and some comments should be addressed:
1. What are the byproducts of sulfate and antimony degradation?
Response: I would like to ask you to avoid misuse of the expression. Desulfovibrio reduces sulfate to sulfide and oxidizes lactate to acetate. Resulting sulfide reduces antimonate to antimonite, precipitating Sb2S3. Those reactions were not “degradation” but redox reactions (oxidation-reduction). Antimony trisulfide (Sb2S3) can be oxidized to Sb2O3 as a subproduct (byproduct) under aerobic condition. This explanation was added on L54-55. But in our anaerobic culture, we could not find apparent evidence of accumulation of Sb2O3.
- What are the biochemical and stoichiometric reactions in these sulfate and antimony degradations?
Response: We added the biochemical and stoichiometric reactions as eqs. 1-3, on L316-318.
2CH3CH(OH)COO- + SO42- ---> 2CH3COO- + 2HCO3- + HS- + H+
2Sb(OH)6- + 6HS- + 6H+ ---> Sb2S42- + 2S +12H2S
Sb2S42- + H+ ---> Sb2S3 + HS-
Actual reactions should be much more complicated, these are simplified expression. Stoichiometry was discussed on L311-314.
What about the quality of final effluent compared with the WHO and USEPA regulations?
Response: The total soluble Sb removal in the pure culture of strain NSLLLH1b for the initial Sb concentration of 50 mg/L was 91–98 % in the presence of up to 15 g/L NaCl, corresponding to the final concentration of 0.5-1.0 mg/L. WHO and USEPA recommended the maximum allowable concentration of Sb in “drinking water” should be lower than 6 μg/L and 5 μg/L, respectively (added on L34-38). These values cannot be compared with the final concentration in the pure culture of strain NSLLLH1b. Our purpose is not water treatment for drinkable or tap water supply but wastewater treatment for protecting natural water bodies. A discharge standard for Sb from industries has not been established in most countries; however, it is 0.1 mg/L for total Sb in dyeing and finishing wastewater from the textile industry in China, as discussed on L335-337.
A graphical abstract can be added.
Response: A graphical abstract is optional but was added as suggested.
Highlights can also be added.
Response: According to Instructions for Authors, “Water” has no highlight.
In the last paragraph of Introduction, clearly illustrate what has been done at work in numbering/bulletin form.
Response: It was revised on L75-77 that (i) SRB were enriched and isolated from a landfill leachate sample obtained from Hanoi, Vietnam. (ii) The bacterial Sb removal capabilities were characterized at vari-ous pH, salinity, sulfate, and Sb concentrations.
Plz write down the material and equipment specification and country of purchase.
Response: We have already described these information for specific regents in the text. General regents were purchased from Fujifilm Wako Pure Chemical Corp. (Osaka, Japan), as added on L.84-85. We would appreciate it if you could point out concretely.
How did you ensure the precision and accuracy of detection methods?
Response: The Sb removal tests using strain NSLLH1b were conducted in triplicates, as described on L117-118. ICP-OES and ion chromatography systems were properly maintained by consulting Agilent Technologies Japan and Shimadzu Corp., respectively.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors1. The Introduction needs to be expanded. Moreover, in n the introduction part, it is necessary to revise the format of the cited references. Avoid lumping references. Instead, summarise the main contribution of each referenced paper in a separate sentence. Please carefully go through the entire manuscript and correct this. This will make the introduction more informative and useful to readers.
2. The conclusions only talk about some studied parameters, which is insufficient to depict the whole picture of the contribution of this study. The authors are advised to write the conclusions in a comprehensive way and should contain key values, suitability of the applied method, the major findings, contributions and possible future outcomes.
3. Figure 4 (SEM image) needs to be redone. It should be clearer and of higher quality.
4. Why are the initial concentrations given in different units in Figure 5? Justify this choice.
Author Response
Reviewer #3:
1. The Introduction needs to be expanded. Moreover, in n the introduction part, it is necessary to revise the format of the cited references. Avoid lumping references. Instead, summarize the main contribution of each referenced paper in a separate sentence. Please carefully go through the entire manuscript and correct this. This will make the introduction more informative and useful to readers.
Response: The first paragraph (L30-38) was expanded for describing toxicity and drinking water standard on Sb.
The conclusions only talk about some studied parameters, which is insufficient to depict the whole picture of the contribution of this study. The authors are advised to write the conclusions in a comprehensive way and should contain key values, suitability of the applied method, the major findings, contributions, and possible future outcomes.
Response: For depict the whole picture, antimony removal in the mixed bacterial culture derived from of Nam Son landfill leachate in Vietnam was added on L348-351. A major finding is that strain NSLLH1b can remove Sb(V) at NaCl concentration of 0.2–15 g/L (L355). As future outcome is that this bacterium is considered to be used properly for treatment of Sb-containing wastewater with moderate salinity and pH value if electron donors (carbon sources) and nutrients are supplied for its growth (L357-358).
Figure 4 (SEM image) needs to be redone. It should be clearer and of higher quality.
Response: It was replaced with clearer one in Fig. 4.
Why are the initial concentrations given in different units in Figure 5? Justify this choice.
Response: Lactate concentration was changed from mM to mg-C/L in Figure 5 and the text.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAccept
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors responses are satisfactory
