Using the Response Surface Methodology to Treat Tannery Wastewater with the Bicarbonate-Peroxide System

Round 1

Reviewer 1 Report

Dear Editor:

Thank you for giving me the opportunity to revise the MS entitled “Use the response surface methodology for treating tannery wastewater using the bicarbonate-peroxide system (BAP)” by Néstor A. Urbina-Suarez and his/her colleagues that was submitted to “ChemEngineering”.  This study used response surface methodology to obtain the optimal process for treating tannery wastewater using the bicarbonate-peroxidide system (BAP) system, which has good research value. However, there are several requirements that have to consider by the authors. In this regard, the following comments are requested to be addressed by the authors:

1.      The comparative analysis of the treatment processes for organic wastewater is not comprehensive enough, and we hope to provide a more comprehensive overview.

2.      Lack of cost analysis on various processes for treating tannery wastewater, and whether BAP has a cost advantage.

3.      Further research can be conducted on the mechanism of BAP removal of tannery wastewater.

4.      The references are somewhat outdated, and it is recommended to add some recent relevant literature.

I would suggest that the authors include the following recent studies to improve the manuscript.

Comparison of the degradation of molecule and ionic ibuprofen in UV/H2O2 system [J]. Water Science & Technology, 2018, 77 (9), 2174-2183.

Oxygen reduction reaction in the field of water environment for application of nanomaterials, Nanomaterials. 2020, 10(9), 1719.

5.      The format of the entire text needs to be carefully checked, such as some superscripts and subscripts (Line 500).

Best regards,

Author Response

EVALUATOR 1

1. The comparative analysis of the treatment processes for organic wastewater is not comprehensive enough, and we hope to provide a more comprehensive overview.

R/ Thank you for your comment; the comparison of AOPs processes used in tannery wastewater treatment was expanded in the introduction.

2. Lack of cost analysis on various processes for treating tannery wastewater, and whether BAP has a cost advantage.

R/ A table comparing the costs of different treatment processes and the BAP system is included at the end of the manuscript.

3. Further research can be conducted on the mechanism of BAP removal of tannery wastewater.

R/ Thank you for your comment; indeed, the working group is still working on this system applied to other types of wastewater and its coupling with biological systems.

4. The references are somewhat outdated, and it is recommended to add some recent relevant literature.

I would suggest that the authors include the following recent studies to improve the manuscript.

Comparison of the degradation of molecule and ionic ibuprofen in UV/H2O2 system [J]. Water Science & Technology, 2018, 77 (9), 2174-2183.

Oxygen reduction reaction in the field of water environment for application of nanomaterials, Nanomaterials. 2020, 10(9), 1719.

R/ Thank you for your comment; it is essential to point out that literature on this subject is scarce, and there have been no publications on tannery wastewater. Likewise, in the introduction and other sections of the manuscript, more recent references related in some way to the research topic were included. The citations suggested by the reviewer were included.

5. The format of the entire text needs to be carefully checked, such as some superscripts and subscripts (Line 500).

R/ Thank you for your comment; the corresponding correction has been made.

Reviewer 2 Report

It's a really interesting work. Aim and scope are clearly defined and the results are well discussed. I think that results can be improved with one paragraph which exposes the experimental results obtained, discuss it and only after the part just written.

 This work aims to contribute to the knowledge of the potential applications of the BAP system in the treatment of tannery wastewater and optimize the process parameters.

AOPs for the removal of contaminants are a discussed topic, especially in the tannery sector. In this work, a variant of these treatments has been tested which to date had never been tested in this particular sector. So I believe that the topic is original and of considerable interest. Other applications of this system focus on other types of wastewater, this is the first study on the application of the bicarbonate-peroxide system to tannery wastewater.

It's a really interesting work. Aim and scope are clearly defined and the results are well discussed. I think that results can be improved with one paragraph which exposes the experimental results obtained, discuss it and only after the part just written

There is a lack of comparison between this application and other experiments with different AOP in tannery waste, useful for understanding the potential advantages and criticalities of this system. It would also be advisable to include some estimates of the costs of this treatment, comparing it with other treatments.

English is good. There are just some long sentences that have to be reduced.

Author Response

EVALUATOR 2.

It's a really interesting work. Aim and scope are clearly defined and the results are well discussed. I think that results can be improved with one paragraph which exposes the experimental results obtained, discuss it and only after the part just written.

This work aims to contribute to the knowledge of the potential applications of the BAP system in the treatment of tannery wastewater and optimize the process parameters. 

AOPs for the removal of contaminants are a discussed topic, especially in the tannery sector. In this work, a variant of these treatments has been tested which to date had never been tested in this particular sector. So I believe that the topic is original and of considerable interest. Other applications of this system focus on other types of wastewater, this is the first study on the application of the bicarbonate-peroxide system to tannery wastewater.

It's a really interesting work. Aim and scope are clearly defined and the results are well discussed. I think that results can be improved with one paragraph which exposes the experimental results obtained, discuss it and only after the part just written

There is a lack of comparison between this application and other experiments with different AOP in tannery waste, useful for understanding the potential advantages and criticalities of this system. It would also be advisable to include some estimates of the costs of this treatment, comparing it with other treatments.

R/ We thank you for your comments, and the discussion of the results was expanded by the statements made. A section comparing the BAP system and the cost analysis with other AOPs was also added.

Reviewer 3 Report

1.       You must specify the full name of the abbreviations, such as COD, BOD, etc.

2.   It is required to indicate the valence form of heavy metals, for example, Zn, Cr, etc.

3.       It is necessary to reflect in the formula the anionic form of compounds , etc.

4.       A reference is provided to the 23rd edition of the standard methods, while the 24th edition was put into effect on 03/31/2023

5.       It needs to be clarified whether the contact time of bicarbonate and hydrogen peroxide with treated water is a significant factor

6.       It is necessary to present the indicators of pollution after treatment of wastewater from the tannery, in the same order as the indicators presented before treatment in table 3.

7.       BOD/CBD and BOD/COD ratios after treatment of tannery wastewater according to the presented methodology must be submitted

8.       Recommendations for post-treatment of the cleaning method under consideration should be provided, as biological treatment requires temperature adjustment, ph

9.       Recommendations are also needed on the biological treatment method applied after BAP

Comments for author File: Comments.docx

Author Response

1. You must specify the full name of the abbreviations, such as COD, BOD, etc.

R/ Thank you for your comments; all the suggested adjustments have been made.

2. It is required to indicate the valence form of heavy metals, for example, Zn, Cr, etc.

R/ Thank you for your comments; all the suggested adjustments have been made.

3. It is necessary to reflect in the formula the anionic form of compounds, etc.

R/ Thank you for your comments; all the suggested adjustments have been made.

4. A reference is provided to the 23rd edition of the standard methods, while the 24th edition was put into effect on 03/31/2023

R/ Thank you for your comment about the edition of the reference for the standard methods. We want to let you know that we used edition 23 since it was available when the experiments were conducted, and the manuscript was under review by the research director. We believe keeping the edition and reference used for all the measurement protocols is relevant.

5. It needs to be clarified whether the contact time of bicarbonate and hydrogen peroxide with treated water is a significant factor

R/ We appreciate your comments. Regarding the reaction time, it is essential to point out that previous tests preliminarily determined the 1 hour reaction time. To assess the conditions that were evaluated in the response surface methodology, tests were performed where it was determined that time was not a very significant factor. Also, from the little literature available, it was found that after 1 hour, the variations in COD concentrations were not significant.

6. It is necessary to present the indicators of pollution after treatment of wastewater from the tannery, in the same order as the indicators presented before treatment in table 3.

R/ We appreciate your comments. In response to your comment, table 8 has been added, which contains the information requested by the evaluator.

7. BOD/CBD and BOD/COD ratios after treatment of tannery wastewater according to the presented methodology must be submitted

R/ Thank you for your comment, the calculation of the BOD/DQO ratio after the BAP process was integrated into the manuscript according to the comment made by the evaluator in the item made by the evaluator.

8. Recommendations for post-treatment of the cleaning method under consideration should be provided, as biological treatment requires temperature adjustment, ph

R/ We appreciate your comment; currently, in the working group, we are working on the coupling of the BAP system and the cultivation of thermotolerant microalgae and cyanobacteria; here, we are evaluating the optimum pH and the ability to grow at the temperature that comes with out of the BAP system. Also included in the manuscript are recommendations on the aspects to continue evolving to achieve the coupling of the BAP system with biotechnological strategies, such as microalgae cultivation.

9. Recommendations are also needed on the biological treatment method applied after BAP

R/ Thank you for your comment; we would like to point out that currently, the working group is evaluating the growth of strains of microalgae and autochthonous thermotolerant cyanobacteria in tannery effluents that have been treated with the BAP system, where through experimental designs, we are evaluating the production of biomass and metabolites of interest in these effluents. Likewise, at the end of the manuscript, some recommendations were made on what topics to address in future research.

Author Response File: Author Response.docx

Reviewer 4 Report

In this work, the authors used a bicarbonate-peroxide system (BAP) system in the treatment of tannery wastewater, including the optimization of process parameters (pH, temperature, H2O2 concentration, and bicarbonate concentration) to maximize the removal of contaminants (COD removal, ammonia nitrogen removal, and nitrate concentration). Thus, it can be recommended for publication in the Journal of “ChemEngineering” after the following addressed:

1. Abstract part: Detail the problem to be solved with the present study (i.e., the problem of tannery wastewater). Moreover, it shows details about the BAP system and quantitative results obtained, and the novelty of this manuscript.

2.  Change M to mol L^-1

3. Improve the quality of Figure 1 which is blurred

4. Line 154: What is the ambient temperature?

5. Line 156: Why choose 610 nm?

6. Line 173: Introduce discussion for all parameters such as nitrates, nitrites, ammonia nitrogen, phosphates, conductivity, and TSS. Also, is there any reference value in environmental legislation for comparison purposes?

7. Present the Pareto charts from the experimental design

8. Perform ANOVA analysis for BOD removal, as it is an important parameter in removal (as in the BOD/COD ratio)

9. Do not break Table 5, leave it on the same page

10. Line 294: Check the numbering of Table 6, which in this case would be Table 5

11. All results need in-depth discussion and correlation with the literature.

Author Response

In this work, the authors used a bicarbonate-peroxide system (BAP) system in the treatment of tannery wastewater, including the optimization of process parameters (pH, temperature, H2O2 concentration, and bicarbonate concentration) to maximize the removal of contaminants (COD removal, ammonia nitrogen removal, and nitrate concentration). Thus, it can be recommended for publication in the Journal of “ChemEngineering” after the following addressed:

1. Abstract part: Detail the problem to be solved with the present study (i.e., the problem of tannery wastewater). Moreover, it shows details about the BAP system and quantitative results obtained, and the novelty of this manuscript.

R/ We appreciate your comments; all comments were taken into account to improve the manuscript.

2. Change M to mol L^-1

R/  Thank you for your comments, the adjustment was made in accordance with the observations made by the evaluator.

3. Improve the quality of Figure 1 which is blurred

R/  Thank you for your comment; the adjustment of Figure 1 was made.

4. Line 154: What is the ambient temperature?

R/ Thank you for your comment, the adjustment followed by the evaluator incorporated the ambient temperature Line 177.

5. Line 156: Why choose 610 nm?

R/ Thank you for your comment; the adjustment was made according to the method used; by error, it was stated that the measurement was made by spectrophotometry, the correction was made, and the procedure for calculating COD was indicated.

6. Line 173: Introduce discussion for all parameters such as nitrates, nitrites, ammonia nitrogen, phosphates, conductivity, and TSS. Also, is there any reference value in environmental legislation for comparison purposes?

R/ We thank you for your comment, a discussion of the comment made by the reviewer was incorporated into the manuscript.

7. Present the Pareto charts from the experimental design.

R/ We thank you for your comment. We respectfully point out that the ANOVA information tables for each parameter contain the information of the Pareto diagrams; therefore, they are not included to avoid data duplication and maximize space in the manuscript.

8. Perform ANOVA analysis for BOD removal, as it is an important parameter in removal (as in the BOD/COD ratio)

R/ We thank you for your comment, about your observation we respectfully allow us to indicate that the study was designed with the COD because compared to the BOD, the results were less statistically dispersed in the preliminary tests; likewise, for time, cost, and material availability issues, it was complex to perform the analysis with the BOD, each evaluation lasts five days, allowing not having available material since each test was performed in triplicate. The number of samples made this analysis complex. It is an important parameter, but only the ANOVA was performed with the parameters established in the manuscript for practical reasons.

9. Do not break Table 5, leave it on the same page

R/ Thank you for your comment; the correction was made in accordance with the observation made.

10. Line 294: Check the numbering of Table 6, which in this case would be Table 5

R/ Thank you for your comment; the correction has been made according to the observation.

11. All results need in-depth discussion and correlation with the literature.

R/ Thank you for your comment; the discussion of the results was expanded.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

ok to accept.