Low-Carbon Operation Strategies for Membrane-Aerated Biofilm Reactor Through Process Simulation and Multi-Objective Optimization

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The topic is interesting, novel and timely. However, I have some comments which need to be addressed by the authors:

General comment:

1. Can you change the costing estimate unit from CNY/m³ to USD/m³ for the wider audience to easily understand and comprehend?
2. There are lots of formatting issues throughout the manuscript, such as using a comma instead of a full stop, capital letters, etc.

Abstract:

• While the research aim in Lines 15–17 focuses on enhancing process performance, the results in Lines 20-26 fail to report any indicators of process efficiency. As a result, the stated aim is insufficiently supported by the presented findings

Introduction:

• Line 46: Define AAO when first used. Although it is already defined in the abstract, it needs to be defined in the main body of the manuscript when first used
• Line 59, the authors stated that MABR is often placed in the anoxic or aerobic zone. MABRs are commonly installed in either the anoxic or aerobic zone, reflecting the conventional configuration designed to promote simultaneous nitrification and denitrification (SND). However, recent studies indicate that MABRs can also be integrated into alternative process configurations, such as partial nitrification-denitrification (PND) and partial nitritation-anammox (PNA), which may incorporate an anaerobic zone in addition to aerobic and anoxic zones.
• Lines 64 to 66: Social attribute/objective, such as public acceptance as well as public health and safety, is also key in evaluating the sustainability of a WWTP.

Materials and methods:

• Table 1: The authors should provide a more detailed explanation of the criteria used to select the influent and effluent standards. The basis for these values is unclear and lacks supporting citations. For example, why was a COD concentration of 500 mg/L chosen for the medium instead of other values such as 520 or 530 mg/L? Additionally, why didn’t they take directly from published scientific literature or determine through laboratory measurements? A clear justification, supported by references, is needed to strengthen the credibility of the selected parameters.
• Lines 141 to 142: It's not clear which literature sources you are referring to

Results and discussion:

• Do you mind performing some statistical analysis on the results shown in Figure 2? For example, do you think there is any statistical difference between L-A/L-IV, M-A/M-IV and H-A/H-IV for both Figure 2a and b?
• Lines 232 to 238, the authors are referring to previous studies (plural), but then just put only one citation.
• Figures 4 and 5 have very low resolution and are therefore not clear.

Comments on the Quality of English Language

Formatting is required

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Abstract: Please clearly state what is meant by different conditions and different scenarios.

The paper relies solely on simulation data; no experimental work was conducted to compare the plant's performance.

Validation of the data using real-life data is missing. How to evaluate the simulation performance in the absence of experimental data.

The selection of the three units of the bioreactor volume and DO is selected without any reference or mention of previous literature.

The carbon emissions effect is calculated without accounting for chemical costs, membrane costs, or sludge treatment.

How current DO levels are selected and how they are beneficial, based on the literature.

No discussion on the biofilm thickness, membrane fouling, or DO levels in the discussion section.

The English language needs significant improvement before resubmission.

Conclusion: What does it mean by wide applications.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors present in this paper, the performance and efficiency of various wastewater treatment processes, specifically comparing traditional AAO processes with AAO-MABR (anaerobic or aerobic} coupled processes in terms of effluent quality, carbon emissions, and operational costs. And as mentioned by them this is a relatively novel analysis of the advantages of AAO-MABR process. So, the originality.

The authors made a relatively good literature review in the introduction, but they can also add another two papers: 

Jianbo Liao, Shuang Li, Yihong Liu,Siyuan Mao,Tuo Tian, Xueyan Ma, Bing Li and Yong Qiu, “Multi-Objective Optimization Based on Simulation Integrated Pareto Analysis to Achieve Low-Carbon and Economical Operation of a Wastewater Treatment Plant”, Water 2024, 16(7), 995; https://doi.org/10.3390/w16070995    

Mainly related to the part of Pareto analysis to achieve Low carbon and economical operation of WWTP

Huanqi He , Brett M. Wagner , Avery L. Carlson , Cheng Yang and Glen T. Daigger, “Recent progress using membrane aerated biofilm reactors for wastewater treatment”, Water Science & Technology No,1 pp/ 443 (2021)   doi: 10.2166/wst.2021.443

The material and methods, results and discussion sections are OK as are the tables. The conclusion would be much clearer and strongly emphasized if the authors could adopt the following method of presentation of the results for comparing the conventional Anaerobic-Anoxic-Oxic process with either the anoxic AAO-MABR or the oxic AAO-MABR:

1. Characteristics of process effluent quality
2. Process operating costs
3. Carbon emissions
4. Energy consumption and costs

 

 

 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed the comments. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors in their response to my comment on the need to mention in the conclusion:

As they did in the abstract saying: " energy consumption was reduced by an average of 0.11 kwh/m3 lowering the operating costs by 0.036 $/m3" 

did respond that there is no place for specific mention of the energy costs (since they are included in the operational costs).

I do not agree with that.

SInce also as it was important to mention in the abstract the energy costs are one of the conclusions of the paper

 

 

Author Response

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Author Response File: Author Response.pdf