Multi-Objective Design of a Horizontal Flow Subsurface Wetland

Round 1

Reviewer 1 Report

In this manuscript, the author proposes using the NSGA-II algorithm to optimize the design of an HFSW for grey-water treatment, in order to minimize the physical volume of wetland and maximize the contaminant removal efficiency. This work summarizes the differences in the design and actual operation of constructed wetlands and provides new insights and ideas for addressing these differences and optimizing wetland structures. The following advice is given for manuscripts:

1. The content of lines 1-7 in the abstract is not closely related to the theme of this manuscript, and it is recommended to make revisions.

2. The introduction to the literature review section is too long. References to existing research should be concise and provide a clear depiction of the current state of knowledge, findings, and perspectives related to the study. Avoid introducing a large amount of background information unrelated to the study.

3. The NSGA-II algorithm is prone to producing identical individuals between generations during the process of crossover and mutation, which limits the algorithm's search ability and makes it easy for the algorithm to find local optimal solutions. Does the author consider combining with other algorithms to solve this problem?

4. The unit symbols in the manuscript should be written in a standardized manner.

5. Figure 2 only shows the scatter plot of Pareto-front at P=200 and P=600, but lacks the scatter plot of Pareto-front at P=400.

6. Note that the design parameters for hydraulic retention time in Table 2 range from 11 to 16, even reaching 613. However, in Section 2.1, line 156, the unit of hydraulic retention time is in days, which is not in line with the design parameters of constructed wetlands in real life. In most cases, the hydraulic retention time of constructed wetlands is 1-3 days. Excessive hydraulic retention time in constructed wetlands can lead to an increase in anaerobic zones and affect sewage treatment efficiency.

7. What does DBO₅ mean in line 231 of Section 4.1? I guess the author should be referring to BOD₅.

8. The slope unit of the constructed wetland is represented by "%", and it was found in Section 2.1, line 161, and Table 1 that the author labeled the slope unit as "m".

9. The discussion section should compare and analyze the conclusions drawn horizontally or vertically with previous research findings.

10. The conclusion summarizes the limitations of this research topic. Correspondingly, the future research direction of the research topic can be pointed out or prospects for future work can be provided.

11. Further language polishing work should be carried out on the manuscript, as there are still some grammar issues in the manuscript.

Further language polishing work should be carried out on the manuscript

Author Response

see file pdf

Author Response File: Author Response.pdf

Reviewer 2 Report

The study addresses an important issue in wastewater treatment technology. The use of a multi-objective evolutionary algorithm for optimizing the design of a horizontal flow subsurface wetland for grey-water treatment is innovative and adds value to the existing literature. However, certain aspects of the manuscript require improvement before consideration for publication. The revisions are required to improve clarity, thoroughness, and overall quality.

Many sentences in the manuscript exhibit grammatical errors. It is recommended to perform a comprehensive language review of the entire manuscript to minimize redundancy and incorporate supporting references and data where appropriate.

The introduction section lacks clarity largely because it condenses information into only two paragraphs with few references. To enhance clarity, it would be beneficial to provide a summary at the end of this section outlining the methods, objectives of the study, and expected results. This summary could serve as a roadmap for readers, offering a concise overview of the research approach and goals. By expanding on these aspects, readers could gain a clearer understanding of the significance of the study, facilitating their engagement with the subsequent sections of the paper. Starting a paragraph with “As can be seen in the papers reported up to date without references” does indeed introduce confusion, as it requires readers to refer to the previous paragraph without clear guidance. Furthermore, the sentence suggests a discussion rather than a clear introduction of the topic. It is advisable to rewrite the introduction with a more organized structure that presents the background information and context of the study in a concise and logical manner. This will better prepare readers to understand the study's purpose and significance.

NSGA-II algorithm contributes to the novelty of the work, as its utilization has been limited in previous investigations. However, the limitations of this approach are not clearly articulated, hindering the prioritization of future studies employing the same methodology. This is an important aspect that should be addressed in the discussion of the paper. By outlining priorities for future research utilizing similar approaches, researchers can effectively explore the potential of NSGA-II and expand its application to other problem domains.

L12 The phrase “design variables” should precede the list of variables it describes: ...based on six design variables: hydraulic retention time, width, ...

L14 Numbers and units should be kept separate. It is advisable to conduct a thorough language check for the entire manuscript (e.g., L112, L193, etc.).

L22 The sentence is logical, but it is somewhat redundant because it repeats the word “pollution” twice. It would be better to improve it by avoiding repetition and by including other types of environmental issues (e.g., water scarcity, soil erosion, and atmospheric drought).

L147 The information introduced at L138 makes the use of the word "section" unnecessary.

The figure caption should include the meanings of parameters h_a, h_m, W, and L to clearly illustrate the design of a horizontal flow subsurface wetland (HFSW) for grey-water treatment.

L236 What version of Matlab was utilized?

L 263 and L 264 Please indicate the location of the values considered for this analysis by providing supporting material or including relevant statistics. Furthermore, incorporating the works of other researchers in discussing the findings would enhance transparency and allow for a more comprehensive analysis of the significance and scope of the study. Otherwise, the findings may solely reflect the authors' perspective.

L267 Where can established constraints be found?

Moderate editing of English language required.

Author Response

see file pdf

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

All issues in the review have been addressed item by item.

Minor editing of English language required