Challenges and Emerging Trends in Advanced Oxidation Technologies and Integration of Advanced Oxidation Processes with Biological Processes for Wastewater Treatment
Round 1
Reviewer 1 Report
1. Please write down the reference sources of the substances and related data in table1.
2. Please also write down the advantages and disadvantages of each of the different substances used in table1.
3. The references were not new enough. Authors should put more new references into this manuscript.
In my opinion, this article can be published in this journal if the authors explain all the unclear parts and offer enough new references. Also, the authors should recheck and correct the errors of typos and grammar before sending out this manuscript. By all the aspects enumerated above, the author should make a rigorous revision of the paper before its publication.
Comments for author File: 
Comments.pdf
Author Response
Challenges and Emerging Trends in Advanced Oxidation Technologies and Integration of AOPs with Biological Processes for Wastewater Treatment
Comments and suggestions
Reviewer 1:
Thank you for your comments. I have revised the manuscript as suggested by the reviewer 1.
- Please write down the reference sources of the substances and related data in Table 1.
Response:
Included in the manuscript.
- Please write down the advantages and disadvantages of each of the different substances used in Table 1.
Response:
It has been included as per reviewer’s suggestion.
Hydroxyl radicals (OH.) have the highest oxidation potential (E0: 2.8 eV vs normal hydrogen electrode (NHE)). The most potent oxidant, fluorine, which has an oxidation potential of 3.06 V, cannot be utilised to treat wastewater due to its toxicity (Hutalong et al. 2020). Ozone is an extremely potent oxidant with a redox potential of 2.08 eV that may directly oxidise microorganisms and a variety of organic substances. However, it can also cause secondary reactions by generating hydroxyl radicals that can subsequently react with the microcontaminants. However, this process has some drawbacks, including the poor solubility of ozone in water, the need high energy and the generation of reaction products that could be even more hazardous than the parent compounds (Fernandos et al. 2022). Other frequently found oxidants, like hypochlorite, hydrogen peroxide are less reactive because they have paired electrons in their chemical structures. Hydrogen peroxide (H2O2) is an environmentally friendly oxidant with high oxidation potentials across the entire pH range. These properties give it exceptional bleaching and antiseptic capabilities that have led to many applications in wastewater treatment industries (Tong et al.2022).
- The references were not new enough. Authors should put more new references into this manuscript.
Response:
Recent references are included in the manuscript as per the suggestion given by the reviewer.
Reviewer 2 Report
The following report is based on my review of the manuscript entitled “Challenges and Emerging Trends in Advanced Oxidation Technologies and Integration of AOPs with Biological Processes for Wastewater Treatment”. The manuscript sustainability-2195740 suits the scope of “Sustainability” and is also interesting. However, the following minor comments have been pointed out and need to be addressed properly for further improvement of the manuscript. They are as follows:
1. The present work is appreciable. The abstract required through editing due to a typo error in line 12. In line 17 “This review reviews the effectiveness” change review reviews.
2. The introduction is well written. However, improvements can be made to enrich the manuscript to attract readers across the globe.
3. The problem statement should be clearly stated.
4. The novelty of the review is also not clearly mentioned. The authors need to state the novelty of the study.
5. The conclusion section is also well written. However, the authors should mention facts and figures related to the treatment methods.
6. Authors should avoid citations of non-index articles. Kindly, update the reference list with valid indexed citations. Authors should cite only recent 5 years' published articles.
Author Response
Reviewer 2:
- The present work is appreciable. The abstract required through editing due to a typo error in line 12. In line 17 “This review reviews the effectiveness” change review reviews.
Response:
Corrected in the manuscript.
- The introduction is well written. However, improvements can be made to enrich the manuscript to attract readers across the globe.
Response:
Included in the manuscript.
- The problem statement should be clearly stated.
Response:
Explained in the manuscript.
- The novelty of the review is also not clearly mentioned. The authors need to state the novelty of the study.
Response:
Explained in the manuscript
- The conclusion section is also well written. However, the authors should mention facts and figures related to the treatment methods.
Response: Role of reactor configuration is concluded in this section
- Authors should avoid citations of non-index articles. Kindly, update the reference list with valid indexed citations. Authors should cite only recent 5 years' published articles.
Response:
References are updated in the manuscript.
Reviewer 3 Report
The manuscript reviews wastewater treatment technologies rather comprehensively. It is mostly well-written and well-structured, but there are still some weaknesses. The following issues should be considered:
Abbreviations (AOP) should not be used in the title
The purpose and structure of the paper should be introduced in the introduction. The research gap is also a bit unclear.
In lines 57-59, I do not understand why the importance of investigating clean energy is highlighted in paper considering wastewater treatment? I cannot see the link to wastewater treatment. Please explain.
When you are talking about a group of scientists, do not refer to them using “he”. For example in lines 128, 130, 191.
Modify the caption of Table 3. The “shows” must be removed.
Please squeeze Figure 4. There is a lot of empty space between figures and part of the figure is in another page which is not good
Please check the Instructions for authors and re-write the Authors Contributions (line 728)
Author Response
Reviewer 3:
Thank you for your comments and suggestions.
- Abbreviations (AOP) should not be used in the title.
Response:
Corrected in the title.
- The purpose and structure of the paper should be introduced in the introduction. The research gap is also a bit unclear.
Response:
Included in the manuscript
AOPs like photocatalysis and photo-Fenton have been widely considered as being very effective in removing persistent organic pollutants. It has been proved that AOPs can be utilised as a pretreatment to convert contaminants into shorter-chain compounds or partially decompose hazardous compounds to produce wastewaters with increased biodegradable compounds (Garrido-Cardenas et al. 2019). Furthermore, it is also essential to understand that AOPs have several disadvantages, including the production of unwanted intermediates that may be more stable and harmful than the parent contaminant, the consumption of energy and chemicals, and greater treatment costs. Therefore, these limitations can be mitigated by integrating two or more AOPs or by combining them with biological processes (Nidheesh et al., 2022).
- In lines 57-59, I do not understand why the importance of investigating clean energy is highlighted in paper considering wastewater treatment? I cannot see the link to wastewater treatment. Please explain.
Response:
One way of reducing treatment cost of AOP is by using natural resource sunlight. It is included in the introduction part of the manuscript.
- When you are talking about a group of scientists, do not refer to them using “he”. For example in lines 128, 130, 191.
Response:
Corrected in the manuscript.
- Modify the caption of Table 3. The shows must be removed.
Response:
As per the reviewer suggestion it has been removed now.
- Please squeeze Figure 4. There is a lot of empty space between figures and part of the figure is in another page which is not good.
Response:
Removed from the manuscript.
- Please check the instructions for authors and rewrite the Author’s Contributions.
Response: As per the reviewer suggestion it has been modified now.
Round 2
Reviewer 1 Report
The authors already revised their paper point-by-point according to reviewers’ comments and tried their best to improve our manuscript. In my opinion, this article can be published in this journal.
Reviewer 3 Report
The reviewers' suggestions were covered well by the authors.
