Additional Treatment of Nitrogen and Phosphorus Using Natural Materials in Small-Scale Domestic Wastewater Treatment Unit
Round 1
Reviewer 1 Report
The NCU technology developed in this paper has the characteristics of high efficiency, low cost, simple operation and low sludge yield compared with the existing methods of adding chemical agents, bactericides or extended aeration, and is suitable for the application of small sewage treatment facilities. The research results of this paper have innovative and practical significance.
Suggestion:
1. The experiment lasted for 4 months, and the adsorption capacity of the adsorbent materials (Zeolite and OCS) had not reached saturation, indicating that the adsorbent had a good adsorption capacity. It is suggested that the protective adsorption capacity of the adsorbent material should be given in addition to the laboratory simulation experiment.
2. In the paper, the research results of others are quoted to explain the analytical method and resource utilization of adsorbed saturated materials. It is suggested to supplement the small experiment of regeneration and resource utilization of adsorbent materials developed in this paper.
3. Necessary analysis should be made on the physical and chemical properties of adsorbed materials after 4 months of operation. For example, the content of nitrogen and phosphorus in the adsorption material
Author Response
Response to Reviewer 1 Comments
Comments and Suggestions for Authors:
The NCU technology developed in this paper has the characteristics of high efficiency, low cost, simple operation and low sludge yield compared with the existing methods of adding chemical agents, bactericides or extended aeration, and is suitable for the application of small sewage treatment facilities. The research results of this paper have innovative and practical significance.
Suggestion:
Point 1: The experiment lasted for 4 months, and the adsorption capacity of the adsorbent materials (Zeolite and OCS) had not reached saturation, indicating that the adsorbent had a good adsorption capacity. It is suggested that the protective adsorption capacity of the adsorbent material should be given in addition to the laboratory simulation experiment.
Response 1: Thanks for the note, now the protective adsorptive ability has been added (215-217 lines).
Point 2: In the paper, the research results of others are quoted to explain the analytical method and resource utilization of adsorbed saturated materials. It is suggested to supplement the small experiment of regeneration and resource utilization of adsorbent materials developed in this paper.
Response 2: The authors are not yet able to provide data on the regeneration or use of aggregates for soil improvement. This is a future task that will be addressed later.
Point 3: Necessary analysis should be made on the physical and chemical properties of adsorbed materials after 4 months of operation. For example, the content of nitrogen and phosphorus in the adsorption material
Response 3: The authors agree with this observation, but studies of the chemical properties of the used filter media have not yet been carried out. The main objective of this work was to investigate the efficiency of nitrogen and phosphorus removal from wastewater. The reviewer's suggestion is very acceptable, and the properties of the filter media used will be investigated in detail in the future.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In the study, the authors developed the NCU unit to evaluate the ability to simultaneously eliminate nitrogen (NH4-N, NO3-N) and phosphorus (PO4-P) from wastewater by adsorption. The research is essential for dealing with the issues of phosphorus and nitrogen removal with ecological and environmentally friendly methods suitable for decentralized wastewater treatment. However, moderate revisions are needed in the current edition. It was recommended for acceptance after appropriate revision.
General Suggestion:
1. How to overcome the problem of insufficient innovation in the manuscript.
2. In the section on results, it is possible to analyze the reasons for the low removal of COD, TSS, and BOD.
3. In the conclusion section, the advantages of the NCU can be described in subparagraphs and points to highlight the positive aspects of the NCU device for practical engineering applications.
Specific suggestion:
1.P1, Keywords, the keyword "removal" is recommended to be removed or changed to nitrogen removal and/or phosphorus removal.
2.P3, Figure 2, It is recommended to indicate the pumps in structure 2 in the diagram to make the flow chart more visual and clearer.
3.P4, Table 1, The layout of the table content needs to be optimized.
4.P5, Table 3, The title of the vertical coordinate needs to be changed, “PO4-P” should be modified to “PO4-P”.
5. P6, Table 5, The removal rate curve in the graph overlaps with the dark bar of the incoming water and affects the reading, it is recommended to modify.
6. Some related studies can be cited, such as Science of the Total Environment, 2023, 857, 159462; Journal of Environmental Sciences, 2023, 125, 160-170; Chemosphere, 2021, 278, 130436.
Author Response
Response to Reviewer 2 Comments
Comments and Suggestions for Authors
In the study, the authors developed the NCU unit to evaluate the ability to simultaneously eliminate nitrogen (NH4-N, NO3-N) and phosphorus (PO4-P) from wastewater by adsorption. The research is essential for dealing with the issues of phosphorus and nitrogen removal with ecological and environmentally friendly methods suitable for decentralized wastewater treatment. However, moderate revisions are needed in the current edition. It was recommended for acceptance after appropriate revision.
General Suggestion:
Point 1: How to overcome the problem of insufficient innovation in the manuscript.
Response 1: Thank you for your note. Now the article highlights the novelty of the study (81-86 lines).
Point 2: In the section on results, it is possible to analyze the reasons for the low removal of COD, TSS, and BOD.
Response 2: Thanks for the note, it's now in the text (198-203 lines).
Point 3: In the conclusion section, the advantages of the NCU can be described in subparagraphs and points to highlight the positive aspects of the NCU device for practical engineering applications.
Response 3: Now positive aspects of the NCU are highlighted more in the conclusions section (345-349 lines).
Specific suggestion:
Point 1. P1: Keywords, the keyword "removal" is recommended to be removed or changed to nitrogen removal and/or phosphorus removal.
Response 1. P1: Thanks for the note, it's done now.
Point 2. P3: Figure 2, It is recommended to indicate the pumps in structure 2 in the diagram to make the flow chart more visual and clearer.
Response 2. P3: Figure 2 has been corrected based on a reviewer's comment.
Point 3. P4: Table 1, The layout of the table content needs to be optimized.
Response 3. P4: Thanks for the note, it's done now.
Point 4. P5: Table 3, The title of the vertical coordinate needs to be changed, “PO4-P” should be modified to “PO4-P”.
Response 4. P5: Thank you very much for your note. Now it is done (Fig. 3).
Point 5. P6: Table 5, The removal rate curve in the graph overlaps with the dark bar of the incoming water and affects the reading, it is recommended to modify.
Response 5. P6: The fifth figure is now corrected.
Point 6: Some related studies can be cited, such as Science of the Total Environment, 2023, 857, 159462; Journal of Environmental Sciences, 2023, 125, 160-170; Chemosphere, 2021, 278, 130436.
Response 6: Thanks for the note, valuable article (Science of the Total Environment, 2023, 857, 159462) is now cited.
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript "Additional treatment of nitrogen and phosphorus using natural materials in small-scale domestic wastewater treatment unit" is an interesting read. The following comments may be addressed;
1. How are you going to ensure that the wastewater is not contaminated with substances that would lead to the release of Phosphorus from sorption filters?
2. Do you think the NCU would be efficient enough if the inflow water to NCU has variable pH? Upto what pH range it is expected to work with more than 95% efficiency for P and N removal?
3. Since the method is adsorption based what are the chances of resuspension of adsorbed material from the OCS on completion of their life cycle?
4. Is there any possibility of consistently reducing the P content to less than 0.3 mg/L before releasing the treated wastewater?
Minor corrections in the manuscript are suggested in the attachment.
Comments for author File: Comments.pdf
Minor corrections of text editing are needed.
Author Response
R1
Response to Reviewer 3 Comments
Comments and Suggestions for Authors
The manuscript "Additional treatment of nitrogen and phosphorus using natural materials in small-scale domestic wastewater treatment unit" is an interesting read. The following comments may be addressed;
Point 1: How are you going to ensure that the wastewater is not contaminated with substances that would lead to the release of Phosphorus from sorption filters?
Response 1: Thank you for your note. Phosphorus did not release from the sorbent layers during the research carried out by the authors. Phosphorus concentration in the NCU unit could increase if activated sludge from the biological treatment plant enters it. In order to prevent the activated sludge from entering the sorbent fillers, a geotextile was laid over the zeolite layer (Fig.1 (3)). The geotextile would retain the sludge that could be removed.
Point 2: Do you think the NCU would be efficient enough if the inflow water to NCU has variable pH? Upto what pH range it is expected to work with more than 95% efficiency for P and N removal?
Response 2: Thank you for your note. Phosphorus adsorption efficiency depends on pH. However, the pH of domestic wastewater does not vary over a large range. Moreover, after biological treatment, the pH of the wastewater remains close to neutral. The authors have been studying the parameters of individual sewage treatment plants for five years, and pH is usually in the range of: 6.5-8.2.
Point 3: Since the method is adsorption based what are the chances of resuspension of adsorbed material from the OCS on completion of their life cycle?
Response 3: Thank you very much for your note. According to the authors, at the end of the life cycle of OCS, phosphorus could be recovered from it. Phosphorus could be separated from quartz sand grains by the action of organic or inorganic acids. Research on phosphorus recovery from spent aggregates is a new topic and is not covered in this article.
Point 4: Is there any possibility of consistently reducing the P content to less than 0.3 mg/L before releasing the treated wastewater?
Minor corrections in the manuscript are suggested in the attachment.
Response 4: Thank you very much for your note. Such a possibility is: during 20 days of operation of the NCU, the concentration of PO4-P in the outflow was lower than 0.3 mg/L. Phosphorus concentration could be < 0.3 mg/L for a longer time if we increase the height of the OCS layer (292-294 lines).
Thanks for the corrections in the manuscript (in the attachment). Now the corrections have been taken into account, the errors have been fixed.
Author Response File: Author Response.pdf
Reviewer 4 Report
Review Report
Journal Name: water
Manuscript Title: Additional treatment of nitrogen and phosphorus using natural materials in small-scale domestic wastewater treatment unit
Manuscript ID: 2496179
Manuscript type: Research Paper
The paper examines sustainable technology for wastewater treatment and seeks to improve the efficacy of nitrogen and phosphorus removal, which is crucial for environmental protection. The paper is of little interest and innovation, so need some improvements which are as follows:
1. This study's formatting is improper. Please review the author guidelines.
2. The excerpts do not provide sufficient information on the methodology employed, making it difficult to evaluate the research's rigor.
3. It is unclear whether the paper contains a discussion section that interprets the results in the context of previous research.
4. The excerpts do not indicate whether or not the article discusses the practical implications of the findings for effluent treatment.
5. Can the authors expand on the methodology used to modify natural sorbents and assess their efficacy at removing nitrogen and phosphorus?
6. How do the results of this study compare to the extant wastewater treatment literature? The content is plentiful, but some part of the reference literatures is kind of obsolete (in 5 years). Key publications should be cited as completed as possible. Please also clarify the novelty and application implication of your work in this section. I suggest authors refer to the latest literatures from “MDPI”, and other related journals. But please do not exceed 30% of all citations from sustainability. Authors may see the following reference while revising. “Energies, 2022, 15, 2236”; “Processes, 2022, 10(8), 1581.”; “Processes, 2023, 11(1), 183.”
7. Can the authors discuss the practical implications of using natural sorbents that have been modified for effluent treatment?
The paper appears to be founded on experimental data and addresses an important environmental issue. Due to the limited information provided in the excerpts, it is difficult to completely evaluate the research's methodology, discussion, and practical implications. Though there are some weaknesses, the authors provide extensive analysis and valuable insights into the research topic. Therefore, I recommend major revisions before publication.
Comments for author File: Comments.pdf
Author Response
R1
Response to Reviewer 4 Comments
The paper examines sustainable technology for wastewater treatment and seeks to improve the efficacy of nitrogen and phosphorus removal, which is crucial for environmental protection. The paper is of little interest and innovation, so need some improvements which are as follows:
Point 1: This study's formatting is improper. Please review the author guidelines.
Response 1: Thanks for the comment, the formatting of the article has been revised. The authors used a Microsoft Word template.
Point 2: The excerpts do not provide sufficient information on the methodology employed, making it difficult to evaluate the research's rigor.
Response 2: Thank you very much for your note. Now the methodology section has been supplemented (102-108 lines).
Point 3: It is unclear whether the paper contains a discussion section that interprets the results in the context of previous research.
Response 3: Thanks for the comment. Now the discussion section is supplemented, and the results are compared with the data of previous studies.
Point 4: The excerpts do not indicate whether or not the article discusses the practical implications of the findings for effluent treatment.
Response 4: Thank you very much for your note. The article has been supplemented, the practical meaning has been highlighted more (279-282, 294-297 lines).
Point 5: Can the authors expand on the methodology used to modify natural sorbents and assess their efficacy at removing nitrogen and phosphorus?
Response 5: Thank you very much for your note. The discussion section now discusses the modification of natural sorbents and their effectiveness (319-323 lines).
Point 6: How do the results of this study compare to the extant wastewater treatment literature? The content is plentiful, but some part of the reference literatures is kind of obsolete (in 5 years). Key publications should be cited as completed as possible. Please also clarify the novelty and application implication of your work in this section. I suggest authors refer to the latest literatures from “MDPI”, and other related journals. But please do not exceed 30% of all citations from sustainability. Authors may see the following reference while revising. “Energies, 2022, 15, 2236”; “Processes, 2022, 10(8), 1581.”; “Processes, 2023, 11(1), 183.”
Response 6: Thank you very much for your note. Now the article highlights the novelty and applicability of the study (81-86, 345-349
lines). The list of publications has been expanded, the publications "Energies, 2022, 15, 2236", "Processes, 2022, 10(8), 1581" are cited in the article.
Point 7: Can the authors discuss the practical implications of using natural sorbents that have been modified for effluent treatment?
The paper appears to be founded on experimental data and addresses an important environmental issue. Due to the limited information provided in the excerpts, it is difficult to completely evaluate the research's methodology, discussion, and practical implications. Though there are some weaknesses, the authors provide extensive analysis and valuable insights into the research topic. Therefore, I recommend major revisions before publication.
Response 7: Thank you very much for your note. Now the practical implications are discussed in more detail in the article. The article was supplemented according to the reviewers' comments.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The author basically modified what could be modified according to the first review comments. Unable to modify, put forward further experimental research description. Agree to accept the current manuscript for publication。
Minor editing of English language required。
Author Response
Thank you for your comment, english language is corrected using grammarly.com
Reviewer 2 Report
From my point of view, the revised manuscript can be accepted in present form.
Author Response
Thank you for your review.
