Analytical Method for Polyelectrolytes in Sludge Condensation (Centrate) Units of a Wastewater Treatment Plant

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript focuses on the detection methods for polyelectrolytes (PE) used in wastewater treatment, proposing the use of UV-VIS spectrophotometry to measure the concentration of polyelectrolytes during the wastewater treatment process. This method demonstrates high sensitivity and accuracy, capable of detecting polyelectrolyte concentrations as low as 0.05 mg/L. The results' reliability is validated through repeated experiments and the standard addition method, ensuring the accuracy and reproducibility of the data. The reviewer suggests the following revisions:

1. The study was conducted at only two wastewater treatment plants in Istanbul. It is recommended to collect samples from more wastewater treatment plants in different regions and of various types to validate the universality and reliability of the method.

2. The reviewer suggests that the authors further investigate and discuss potential interference factors in UV-VIS spectrophotometry when applied to complex water samples and propose corresponding solutions.

 

3. In the data analysis section, the manuscript should include a more in-depth discussion of the behavioral differences of different polyelectrolytes in various water samples and explore the reasons behind these differences.

Comments on the Quality of English Language

This manuscript focuses on the detection methods for polyelectrolytes (PE) used in wastewater treatment, proposing the use of UV-VIS spectrophotometry to measure the concentration of polyelectrolytes during the wastewater treatment process. This method demonstrates high sensitivity and accuracy, capable of detecting polyelectrolyte concentrations as low as 0.05 mg/L. The results' reliability is validated through repeated experiments and the standard addition method, ensuring the accuracy and reproducibility of the data. The reviewer suggests the following revisions:

1. The study was conducted at only two wastewater treatment plants in Istanbul. It is recommended to collect samples from more wastewater treatment plants in different regions and of various types to validate the universality and reliability of the method.

2. The reviewer suggests that the authors further investigate and discuss potential interference factors in UV-VIS spectrophotometry when applied to complex water samples and propose corresponding solutions.

 

3. In the data analysis section, the manuscript should include a more in-depth discussion of the behavioral differences of different polyelectrolytes in various water samples and explore the reasons behind these differences.

Author Response

 

Dear Editor,

All the suggestions made by the referees were very helpful in improving the quality of our article. All suggestions of the referees were taken into consideration and necessary corrections were made and placed in the relevant section of the article. The corrections of Reviewer-1 are colored red, and the corrections of Reviewer-2 are colored blue and placed in the appropriate sections within the article. Some answers also include suggestions from both of our referees. Thank you for all your efforts.

 

REVİEWER-1 (Corrections for Reviewer 1)

 

Formun Üstü

 

 

 

This manuscript focuses on the detection methods for polyelectrolytes (PE) used in wastewater treatment, proposing the use of UV-VIS spectrophotometry to measure the concentration of polyelectrolytes during the wastewater treatment process. This method demonstrates high sensitivity and accuracy, capable of detecting polyelectrolyte concentrations as low as 0.05 mg/L. The results' reliability is validated through repeated experiments and the standard addition method, ensuring the accuracy and reproducibility of the data. The reviewer suggests the following revisions:

1. The study was conducted at only two wastewater treatment plants in Istanbul. It is recommended to collect samples from more wastewater treatment plants in different regions and of various types to validate the universality and reliability of the method.

 

The necessary explanation has been made on this issue. However, since the work to be done for each treatment facility would take too much time, the work has been directed to two main facilities. We expect tolerance on this issue. This issue is explained in detail in the introduction.

The necessary explanations and evaluations have been made and added to page 3. It is colored red. Below is a section from the explanation regarding the answer to this question.

“In this study, Ataköy Advanced Biological Treatment Plant, which receives wastewater from industrial facilities after pretreatment, and Büyükçekmece Advanced Biological Treatment Plant, which does not receive industrial water, were selected compared to wastewater treatment plants in other regions.”

2. The reviewer suggests that the authors further investigate and discuss potential interference factors in UV-VIS spectrophotometry when applied to complex water samples and propose corresponding solutions.

The necessary explanations and evaluations have been made and added to page 10. It is colored red.

3. In the data analysis section, the manuscript should include a more in-depth discussion of the behavioral differences of different polyelectrolytes in various water samples and explore the reasons behind these differences.

The necessary explanations and evaluations have been made and added to page 7-8. It is colored red

Comments on the Quality of English Language

This manuscript focuses on the detection methods for polyelectrolytes (PE) used in wastewater treatment, proposing the use of UV-VIS spectrophotometry to measure the concentration of polyelectrolytes during the wastewater treatment process. This method demonstrates high sensitivity and accuracy, capable of detecting polyelectrolyte concentrations as low as 0.05 mg/L. The results' reliability is validated through repeated experiments and the standard addition method, ensuring the accuracy and reproducibility of the data. The reviewer suggests the following revisions:

1. The study was conducted at only two wastewater treatment plants in Istanbul. It is recommended to collect samples from more wastewater treatment plants in different regions and of various types to validate the universality and reliability of the method.

The necessary explanation has been made on this issue. However, since the work to be done for each treatment facility would take too much time, the work has been directed to two main facilities. We expect tolerance on this issue. This issue is explained in detail in the introduction.

Below is a section from the explanation regarding the answer to this question.

“In this study, Ataköy Advanced Biological Treatment Plant, which receives wastewater from industrial facilities after pretreatment, and Büyükçekmece Advanced Biological Treatment Plant, which does not receive industrial water, were selected compared to wastewater treatment plants in other regions.”

 

2. The reviewer suggests that the authors further investigate and discuss potential interference factors in UV-VIS spectrophotometry when applied to complex water samples and propose corresponding solutions.

The necessary explanations and evaluations have been made and added to page 10. It is colored red.

 

3. In the data analysis section, the manuscript should include a more in-depth discussion of the behavioral differences of different polyelectrolytes in various water samples and explore the reasons behind these differences.

 

The necessary explanations and evaluations have been made and added to page 7-8. It is colored red.

We thank you for all your suggestions.

Best regards

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I recommend that this manuscript be accepted after major revision.

After carefully reviewing this work, I found that the manuscript has good strength and has shown interesting work with highly appreciated protocol. Still, it requires some major revisions, and the questions below are clarified:

Introduction

The background is well defined in the introduction. However, reinstate references from 2018 and onwards show improvements in polyelectrolyte detection technologies.

In lines 44-45, proper evidence or citation from high-impact studies should be provided, as the phrase from the statement is much more presumptive than it sounds; the potential carcinogenic effect of polymers is not trivial. The aspects of the importance of UV-VIS spectroscopy concerning other analytical techniques must be discussed.

Materials and Methods:

Chemicals and instruments:

Two types of polymers are used (Zetag™ 8185 and Neu Floc 7331), all of which are clear. However, provide a brief explanation of why you chose these specific polymers; Preparation of stock and working solutions is described, but it is not clear why three concentration ranges were covered (0.05-1 mg/L, 1-5 mg/L, 0-1 mg/L).

Sample Collection and preparation:

Are the two wastewater treatment plants sampled significantly different concerning processes or other characteristics that could affect results? The filtration and the dilution are well enough described, but it should be noted if potential matrix effects from organic matter in the sludge were addressed (beyond dilution).

Measurement Techniques:

The long-wave selection (190-300 nm) is quite normal. Still, there is no evidence of why there are no long-wave spectral data above 300 nm (including relevant references and/or preliminary results).

Results:

The results section is well-structured, and figures and tables are used to improve clarity.

However: Figures 1-6: All axes should be labeled with their units. Summarize important findings, e.g. the comparison of absorbance spectra of the two polymers.

Linear regression results: Highlight the practical implications of the high R² values (e.g., ease of quantification in real-world settings).

Detection limits: Detection limits across matrices are well defined. Note other studies that put these findings in context.

Discussion:

Discuss the environmental impact of the findings. For instance, explain how better detection of polyelectrolytes may affect regulatory compliance or ecosystem health. Limitations of study, such as being sensitive to matrix effects or needing additional calibration curves for other types of polymers Suggest avenues for future research (e.g., exploring other approaches to validate UV-VIS outcomes).

Conclusion:

 

A summary is good but could be more focused on the importance of the application aspects."

Comments for author File: Comments.pdf

Author Response

Dear Editor,

All the suggestions made by the referees were very helpful in improving the quality of our article. All suggestions of the referees were taken into consideration and necessary corrections were made and placed in the relevant section of the article. The corrections of Reviewer-1 are colored red, and the corrections of Reviewer-2 are colored blue and placed in the appropriate sections within the article. Some answers also include suggestions from both of our referees. Thank you for all your efforts.

 

REVİEWER-2 (Corrections for Reviewer 2)

Formun Üstü

 

Comments and Suggestions for Authors

I recommend that this manuscript be accepted after major revision.

After carefully reviewing this work, I found that the manuscript has good strength and has shown interesting work with highly appreciated protocol. Still, it requires some major revisions, and the questions below are clarified:

Introduction

The background is well defined in the introduction. However, reinstate references from 2018 and onwards show improvements in polyelectrolyte detection technologies.

In lines 44-45, proper evidence or citation from high-impact studies should be provided, as the phrase from the statement is much more presumptive than it sounds; the potential carcinogenic effect of polymers is not trivial. The aspects of the importance of UV-VIS spectroscopy concerning other analytical techniques must be discussed.

 

Recent research on polyelectrolyte analysis (after 2018) has been re-investigated and added to the introduction section (page 3-4). It is colored blue.

The necessary corrections and additions were made and added to the “Introduction” section (page 2-3). It is colored blue.

.

Materials and Methods:

Chemicals and instruments:

Two types of polymers are used (Zetag™ 8185 and Neu Floc 7331), all of which are clear. However, provide a brief explanation of why you chose these specific polymers; Preparation of stock and working solutions is described, but it is not clear why three concentration ranges were covered (0.05-1 mg/L, 1-5 mg/L, 0-1 mg/L).

The necessary corrections and additions were made and added to the “Materials and Methods” section (page 4 an page 5). It is colored blue.

 

Sample Collection and preparation:

Are the two wastewater treatment plants sampled significantly different concerning processes or other characteristics that could affect results? The filtration and the dilution are well enough described, but it should be noted if potential matrix effects from organic matter in the sludge were addressed (beyond dilution).

 

The necessary corrections and additions were made and added to Sample Collection and preparation” section (page 6). It is colored blue.

 

Measurement Techniques:

The long-wave selection (190-300 nm) is quite normal. Still, there is no evidence of why there are no long-wave spectral data above 300 nm (including relevant references and/or preliminary results).

The necessary corrections and additions were made and added to the “Measurement Techniques” section (page 6). It is colored blue.

 

Results:

The results section is well-structured, and figures and tables are used to improve clarity.

However: Figures 1-6: All axes should be labeled with their units. Summarize important findings, e.g. the comparison of absorbance spectra of the two polymers.

Linear regression results: Highlight the practical implications of the high R² values (e.g., ease of quantification in real-world settings).

Detection limits: Detection limits across matrices are well defined. Note other studies that put these findings in context.

 

The units on the graphs have been rearranged. Thanks for this suggestion.

The comparison of absorbance spectra of the two polymers are located on page 11-12. It is colored blue.

The linear regression results and evaluation of the practical implications of high R² values ​​and their relevance in real-world environments are located on page 17. It is colored blue.

Limits of detection: Studies on limits of detection across matrices have been researched and re-evaluated and located on page 17-18 and 19. It is colored blue.

 

Discussion:

Discuss the environmental impact of the findings. For instance, explain how better detection of polyelectrolytes may affect regulatory compliance or ecosystem health. Limitations of study, such as being sensitive to matrix effects or needing additional calibration curves for other types of polymers Suggest avenues for future research (e.g., exploring other approaches to validate UV-VIS outcomes).

 

The discussion section has been revised and interpreted in line with the suggestions made. We thank you for these suggestions. and located on page 20. It is colored blue.

 

Conclusion:

 

A summary is good but could be more focused on the importance of the application aspects."

We thank you for all your suggestions. A sentence has been added to the summary section to strengthen the meaning. It has not been changed further in order not to distort the meaning.

We thank you for all your suggestions.

Best regards

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

All the question raised from my side have been well explained, and corresponding revisions have made in the revised manuscript. I agree to accept the manuscript.

Reviewer 2 Report

Comments and Suggestions for Authors

I accept this version, and the manuscript has significantly improved.