Effect of Diclofenac Concentration on Activated Sludge Conditions in a Biological Wastewater Treatment Plant

Round 1

Reviewer 1 Report (Previous Reviewer 3)

I have checked both versions of your manuscript. My issues in the last submission have been adequately addressed in the new submission. I have no further query/comment. The manuscript can be accepted in current form.

Author Response

After a careful consideration of all comments, we have produced a new revised version. 

Reviewer 2 Report (New Reviewer)

Lines 15-16. Why did you explore these concentrations? Also, do you mean "phosphate accumulating organisms"? Or was the phosphorous removed by heterotrophic bacteria following the C/N/P ratio 100:5:1? Please, clarify.

Lines 135-146. Please, report the specific objectives as i)..., ii)...

Line 155. Do you mean [mgO2/dm3] or [mg O2/d*m3]?

Lines 183-184. It would be best if you showed a picture of the bioreactor functioning.

Lines 190-193. Do you have any recirculation? Otherwise, this is scientifically incorrect. It would be best to have nitrification before denitrification to produce nitrate for conversion in N2. Please, clarify.

Lines 212-214. How did you ensure anaerobic conditions?

Results and discussion. 

-Comparison with the literature should be improved.

-Do you have any data about removing diclofenac through the aerobic and anaerobic processes?

-What about the accumulation of volatile fatty acids (VFA)?

Table 2. Data should be reported as "VS" (volatile solids).

Lines 341-343. Of course, you have an increase in ammonia since you are under anaerobic conditions and cannot oxidize NH4+ to NO3-. And I can exclude the presence of anammox in your sludge. Please, clarify.

Lines 392-396. But you have improved methane production at a specific diclofenac concentration. How could you justify that?

Figure 5. It would be best if you also showed the nitrate increase during nitrification.

Table 1. What do AUR and NUR mean?

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report (New Reviewer)

The text describes a study of the effect of DCF (a pharmaceutical compound) on the respiratory activity of activated sludge used in wastewater treatment. The experiment was performed in two series, with different wastewater compositions and DCF concentrations. Respirometry was used to measure oxygen uptake by the sludge, which can be used as a toxicity test to detect substances that inhibit the purification processes. The results showed that, in the range of concentrations used in the experiment, DCF did not negatively affect the metabolism of activated sludge. Although the graphs of oxygen uptake differed in the course of changes, there was no indication of poisoning of the activated sludge, and there was no dependence of the course of the graphs on the size of the DCF dose. However, the text emphasizes that the environmental impact of DCF should not be underestimated, as it can exhibit chronic toxicity to phytoplankton and benthos, and long-term exposure to DCF can cause kidney damage and gill lesions in fish.

One weakness of the study described in the passage is that it only examined the effects of DCF on the specific WWTP process used in the study, and may not be directly applicable to other wastewater treatment systems. Additionally, the study only focused on the effects of DCF on nitrifying, denitrifying, and phosphate bacteria, and did not examine the potential effects on other microorganisms in the activated sludge. Furthermore, the study only considered the short-term effects of DCF exposure, and long-term effects on the efficiency of the wastewater treatment process were not investigated. Finally, the study was conducted under controlled laboratory conditions, which may not fully reflect the complexity and variability of real-world environmental systems. However, based on my analysis of the passage, here are some general comments that editors may find helpful:

• The passage uses technical terms and abbreviations that may not be immediately clear to all readers. Consider including a glossary or providing definitions of key terms in the text.

• Some of the sentences could benefit from being broken up into shorter, more easily digestible chunks. This would make the content more accessible and easier to follow for readers.

• There are a few minor errors in spelling and grammar that could be corrected to improve the overall quality of the text.

• Consider adding more detail or examples to help readers better understand the practical implications of the research being discussed.

• Finally, it may be helpful to include a summary or conclusion at the end of the passage, summarizing the main points and key takeaways for readers.

The quality of English is very good. The sentences are well-constructed, and the vocabulary is appropriate for a technical scientific report. The writer uses technical terms such as "nutrient removal," "methane generation," and "nitrification process," which are appropriate for the topic. The sentences are well-structured and the vocabulary is appropriate for scientific writing. The writer has used technical terms and expressions accurately, demonstrating a good understanding of the subject matter. There are a few minor errors, such as missing commas and typos, but they do not significantly affect the readability or meaning of the text.Overall, the quality of English language in this passage is good. The sentences are well-structured and convey a clear message. There are a few technical terms and abbreviations used, which may be difficult for some readers to understand without prior knowledge. However, given the technical nature of the topic, this is to be expected.

There are a few minor errors or areas where the wording could be improved. For example, in sentence 13, "sensitive" should be spelled "sensitive." In sentence 14, "1.04 mg/dm3 -12.5 mg/dm3" should be written with a space between the dash and the numbers, like this: "1.04 mg/dm3 - 12.5 mg/dm3." In sentence 18, "ability of me-thane-forming bacteria" should be written as "ability of methane-forming bacteria."

In general, however, the passage is well-written and effectively communicates the main ideas.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report (New Reviewer)

Point 4: Lines 183-184. It would be best if you showed a picture of the bioreactor functioning.

Response 4:

The apparatus used, and the probes used in it were only installed in the Swarzewo WWTP laboratory for the duration of the study. Unfortunately, they were not captured in photographs.

Rev response: You need to draw your reactor scheme on ppt.

Author Response

 Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report (New Reviewer)

Upon reviewing the manuscript and the reviewer's comments, it appears that the authors have addressed the reviewer's feedback in a thorough and professional manner. The revisions made, including the addition of a list of abbreviations, breaking up long sentences into shorter fragments, correcting spelling and grammar errors, providing practical implications of the research, and including summaries at the end of relevant subsections, are all positive steps that have improved the clarity, accessibility, and overall quality of the manuscript.

Based on the reviewer's decision of "Accept after minor revision," it seems appropriate to accept the manuscript pending the completion of any necessary minor revisions. However, I would recommend that the authors carefully review the reviewer's comments and address any remaining issues or concerns before submitting the final version of the manuscript.

ok

Author Response

 Please see the attachment

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The submitted work does not have enough novel content to be accepted. My comments are as below:

1. The introduction section is too long and contains unnecessary information not being answered in the discussion section. Please refine it further. There is a lot of problem statements in the introduction section, however, the authors neglect most of them in the discussion part.

2. Please provide the data for the commercial anti-inflammatory drug ‘DicloDuo’ from PharmaSwiss.

3. The composition data for the Sludges: primary, activated, and from the digester, as well as raw sewage for the study that was taken directly from the ‘Swarzewo’ WWTP need to be provided. What are their alkalinity, BOD, COD/BOD, and C/N/P ratio?

4. The composition of the inflowing wastewater was characterized in other studies. Is this just an extension of the work cited in [22, 28]?

5. Why did the authors choose the temperature that was maintained at 38 ± 1 °C, and the pH was 7.3 ± 0.2?

6. How did the authors validate that there is no poisoning in the activated sludge as claimed on page 7?

7. Why does the 3 mg/TS sample has the highest rate recorded compared to another sample? Please explain further with scientific evidence.

8. There are a lot of uncertain in this work's findings which required a major revamp in discussion and analysis. Most of the discussion section only discuss in trend of the graph with lack of scientific discussion. 

Author Response

 "Please see the attachment."

Author Response File: Author Response.docx

Reviewer 2 Report

In this study, the effects of high concentrations of diclofenac on the effectiveness of nitrifying, denitrifying and phosphorus bacteria in the wastewater treatment cycle, as well as the ability of methane-forming bacteria to produce biogas in an anaerobic digester, were discussed and investigated.

The paper is easy to understand. The illustrations in this manuscript are useful. The references are mostly relevant. However, there are still some problems, listed as following:

1. Introduction. This section is too long and somewhat disorganized; it is recommended that half of the content be placed in the discussion section, which should be streamlined and reorganized.

2. Materials and Methods. Please indicate the number of replicates in each treatment, i.e. the number of sample replicates and the number of technical replicates.

3. Results and discussion. Error bars or standard deviations are missing from all charts. Please revise and add.

4. Conclusions. This part of the content is long and complicated; it is suggested to be concise.

5. It is suggested to add the results about biomass of functional microorganisms involved in the nitrification, denitrification, methane production and methane oxidation and so on.

Author Response

 "Please see the attachment."

Author Response File: Author Response.docx

Reviewer 3 Report

The current manuscript entitled “The Effect of Diclofenac Concentration on Activated Sludge Condition in Biological Treatment Plant” by Dereszewska and Cytawa deals with the effect of high concentrations of diclofenac on the effectiveness of nitrifying, denitrifying and phosphorus bacteria in the wastewater treatment cycle. After a careful reading, I found that this manuscript is interesting and the data presented is fine. The manuscript can be considered for publication in a water journal pending suitable major revision. My specific comments are:

1.      The title of the manuscript needs revision, if possible, do not start with “The”.

2.      The abstract is ordinary and provides very less information about the actual study problem and its solution. I suggest rewriting the whole abstract with sentences from the following components and order: research problem, solution, study design, methods, major numerical findings, overall usefulness of the results, and novelty of the work.

3.      Line 17: why repeat the units mg/dm3 and mg/gTS for each treatment?

4.      Line 22: DCF is not defined here.

5.      Line 25: OUR; AUR; NUR not relevant.

6.      Authors need to revise the manuscript considering the fact that they can’t make claims without an appropriate source of information. Most of the paragraphs are sections almost without citations. E.g. Lines 29-40, why not the references are there while the authors made a very strong claim that they have not yet proved in this study? I suggest revising the whole manuscript and providing citations for almost every claim they made.

7.      DCF or Diclofenac? After its first use please follow DCF. Be consistent while writing abbreviations in the whole manuscript.

8.      The chemical structure of DCF must be given within the Introduction section.

9.      Major parts of the introduction can be shifted under the discussion section. The current flow of reading is inappropriate.

10.   Difference subsections of methods, e.g., 208 should be numbered accordingly.

11.   The number and units on the x-axis in fig. 1 must be corrected, delete commas and add doot and standard error bars.

12.   The spacing problem exists in the whole manuscript, please correct it accordingly.

13.   Line 386: Source: own research, delete. From other tables too.

14.   Mg or mg? Be consistent.

Author Response

 "Please see the attachment."