Novel Oxidation Strategies for the In Situ Remediation of Chlorinated Solvents from Groundwater—A Bench-Scale Study

Round 1

Reviewer 1 Report

The title is indicating that this is an review article. 

For section 2.4 have you used any statistical design to find out the probability of the results. 

All graphs needs to be made again because they are not clear and readable.

Results are given well but they are not supported the literature and discussion.

Overall, There are hundreds of abbreviations utilized which creates serious misleadings during reading.

Overall the paper needs to be restructured, and revised again.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This study presents a thorough investigation of novel oxidation strategies for in-situ remediation of chlorinated solvents in groundwater using a combination of oxidation treatments. The research provides important insights into the efficiency of these treatments, particularly highlighting the combined use of persulfate (PS) and sulfidated nano-zero valent iron (S-nZVI) as a potent method for the degradation of chlorinated solvents such as trichloroethylene, tetrachloroethylene, and cis-1,2-dichloroethylene. The study is well structured and provides valuable contributions to the field of groundwater remediation. However, it would benefit from further exploration of the practical applications and potential limitations of the proposed remediation strategies in real-world scenarios.

1. The introduction provides a comprehensive background, but lacks a clear statement of the research gaps that the study seeks to address. It would be beneficial to more explicitly articulate the specific knowledge gaps and how this research intends to fill them.

2. While the experimental design is generally well explained, further clarification of the choice of concentration levels for the oxidants and activators would enhance the reader's understanding of the rationale of the study. In addition, the inclusion of more detailed information on control setups and their relevance to the study objectives could provide deeper insights into the experimental approach.

3. The manuscript mentions the use of statistical tests for data analysis, but lacks a detailed explanation of the choice of these tests and the criteria for statistical significance. Expanding on this could improve the methodological transparency of the manuscript.

4. The discussion benefits from comparisons with existing remediation techniques; however, it could be further enriched by a more detailed analysis of how the proposed method compares in terms of cost, efficiency, and feasibility for large-scale application.

5. The risk assessment sections provide valuable insights, but the discussion of the implications of these results is somewhat brief. It would be valuable to elaborate on how these results compare to existing standards and what they mean for real-world applications.

6. The manuscript addresses the absence of vinyl chloride as a transformation product, but does not discuss the long-term stability of the remediation results or the potential formation of other by-products over time. Addressing these issues could provide a more complete understanding of the effectiveness and safety of the treatment.

7. While the study mentions further field-scale studies as a future direction, a more explicit discussion of the limitations of the current research, including the bench-scale nature of the experiments and potential challenges in scaling up the process, would provide a balanced view of the work.

The authors must have their English proofread by a native speaker, which may be again.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

First, define all acronyms.

For your batch 2, 3, and 4 experiments, it is not clear why you used 10 microgram/liter combined TCE, DEC, and PCE. You state that the acceptable limit is 10 micrograms/liter combined, so why conduct experiments at a concentration that meets the limit? It would make more sense to see if a higher concentration could be brought within acceptable limits. If the actual groundwater levels are below the acceptable limit. is treatment even needed?

You list 59 VOCs in groundwater samples in lines 187-189. Which ate the dominant ones? Perhaps include a table? Are any of these at trace levels low enough to be insignificant?

For this particular study, you note that the polluting industries are no longer in operation. In this case, if there are no more inputs and the levels are below acceptable, why is treatment needed? From a theoretical aspect, the research is interesting, but from a practical aspect, treatment is not required.

Figures 3 and 4 don't present the information in a meaningful way. In addition to giving the percent removal, also give the residual concentration. Ultimately, what is important is the the level is below the acceptable limit.

Give a better explanation of information in Table 7 and the discussion of the results. The different bars on a, b, and c are not clearly explained.

Moderate editing by a native speaker would help.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Dear Authors,

I appreciate your experimental work, which was carried out correctly and professionally planned. The topic developed by your is extremely important and still relevant. Congratulations.

This manuscript is methodologically correct, but contains (in my opinion) numerous imperfections that should be corrected and/or supplemented.

Below are my comments/suggestions:

1. instead of the formula: "submitted", "indicated", "written", indicate the authors of the cited publication to which the authors refer and enter her number in the bibliography

2. in the introduction or in other parts of the work, the nature of the industry located around the researched area can be indicated (short description); Is a specific load of pollutants continuously released into the ground from these enterprises? i.e. can they be limited or is permanent reclamation and water purification in the indicated area necessary - has the accumulation time of the analyzed pollutants been determined and has the time after which the treated surface waters will be polluted again been determined to what level they can be recultivated again?  this remark is valid, although the information about the lack of industrial activity in the studied area was revealed at the end of the manuscript

3. chapter 2.5 - there is no need to describe in detail the technical operation of the device. Just indicate the method with an explanation. In my opinion, this chapter could be reworded without harming its content

4. a similar comment as above applies to chapter 2.6 - it is worth considering and correcting this section

5. Why were 13 of the 20 identified compounds tested when there were 59 of them? What about other chemicals? Are they safe for the environment? - these are questions that occur before analyzing the supplement.  It is worth pointing out to the reader the authors' choices/decisions.

6. Suggests improving the readability of drawings

7. Chapter 3.6 is comparative in nature, but contains only a few sentences relating to other techniques for removing organic pollutants from surface/groundwater. I suggest placing this section in appropriate places to analyze the results or narrowing the thematic section of the section, treating it as a summary ( + comment 11)

8. The conclusions are very detailed and short in relation to the widely presented and discussed results of physicochemical research. In my opinion, the full names of the test chemicals should be included in this section. In the experimental part of the manuscript, the use of abbreviations was justified.

9. To maintain the flow of the text, the authors introduced numerous letter abbreviations, which is not an error. However, due to the large amount of experimental data, the indicated abbreviations made the manuscript very difficult to read. It is also difficult to correctly link the proper names of compounds with the results obtained. You should re-read selected fragments of the study.

I suggest the authors analyze/think about the way they present the results so that the reader understands them properly. This would be very beneficial for improving the manuscript.

Maybe it's worth introducing a list of abbreviations

10. In the content of the study, please define the letter symbols used (lowercase letters) written on bar charts. The authors indicate that the data is included in the attachments (I didn't find them),, but it is worth describing them additionally for the reader who will not analyze the attachments (there are such readers too)

11. Why does the literature review (Table S6) for chapters 3,6 of the manuscript contain only a few publications, the last of which was published in 2020. The above list of examples does not constitute a literature review. Please explain why these publications were chosen? what makes them stand out?

I believe that introducing significant modifications will significantly improve this manuscript

Kind regards

Reviewer

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The paper has been much improved now and can be considered for the publications.

Reviewer 3 Report

n/a

Reviewer 4 Report

Dear Authors,

Thank you for using the comments included in the review to improve the manuscript.

The rewording of the "introduction" and the new arrangement of content in the "Materials and Methods" section have significantly improved the reception of the manuscript's content. It is especially worth mentioning the "Experimental design" section, which is a recipe for correct repetition of research for other scientists. Well done.

The new form of presenting the results is good and easier for the reader to interpret. Of course, the results are not presented in as much detail as in the first version of the study, but this does not reduce the value of the manuscript. It should be noted that the authors have prepared the set of results as a supplement, so an additional set of results is available for very inquisitive readers.

Kind regards,

Reviewer