Research Progress on the Configurations and Performance of Reducing Pollution and Carbon Emissions by Bacterial–Algal Reactor
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn reviewing this manuscript, it's apparent that the work contributes to the understanding of bacterial-algal symbiotic reactors for wastewater treatment. The paper explores various reactor types and their mechanisms, establishing a robust foundation in the field. The discussed systems include closed photobioreactors, rotating biological contactors, membrane aerated biofilm reactors, and open reactors like high-efficiency algae ponds and algal turf scrubbers. Additionally, the paper touches on the challenges faced by these symbiotic reactors and proposes potential solutions to enhance their efficiency.
However, major revisions are needed. The absence of quantitative data on pollutant removal efficiencies for specific reactors is a notable gap, and inconsistencies in referencing and formatting should be addressed for clarity. While the paper acknowledges challenges, a more comprehensive discussion on potential drawbacks and a clearer demonstration of novel insights would enhance its overall quality. Therefore, my recommendation is to reconsider after addressing these substantial revisions. Please consider the questions and comments below, which must be clarified before moving forward with acceptance.
Major revision questions or comments:
1. Please elaborate more clearly on novel insights gained from the review to enhance the paper's impact. I suggest to make a short statement at the introdcution section of the paper. What is the contribution of this review paper?
2. In my opinion, the paper would benefit from a clearer demonstration of novel insights gained from the review. I strongly advise to revise the paper to cover the absence of a detailed discussion on limitations and challenges impact the overall reliability of the findings covered in this review.
3. Could the authors provide specific data on pollutant removal efficiencies for the discussed bacterial-algal symbiotic reactors?
4. Please address to the inconsistency in referencing and formatting observed along the text.
5. Could you include a more comprehensive discussion on potential drawbacks of the proposed reactors to strengthen the analysis?
6. I suggest to include a glossary of relevant terms used in the paper.
7. The paper briefly touches on the various reactor types but lacks a thorough exploration of their practical applications and contexts. Please revise this.
Minor revision questions or comments:
8. The manuscript demonstrates a tendency to use certain terms interchangeably. For instance, the varied use of "reactor types" and "system configurations". Please revise the text to ensure consistency in terminology usage throughout the manuscript.
9. Pleaes revise the text for missing references. Example: in section 2.3, the reference to Johnson et al. (2015) is mentioned in the text but not included in the References.Also, for Smith and Brown (2018) in Figure 5.
10. All the 8 figures could have their quality improved. Overall they are low or medium quality. Do you have permission for usage?
11. Can you provide more details about specific reactor configurations used in different studies for better understanding?
12. Could you clarify terminology in certain sections, particularly regarding reactor types? FOr instance, what does means "mixing method" in the sentence "The HRAP mixing method prevents cell settlement, eliminates thermal stratification, promotes the growth of micro-algae, and distributes nutrients uniformly in the water."?
13. How does the paper account for potential variations in results due to differences in experimental conditions among the studies reviewed?
14. Please reconsider to change organization of the manuscript for a smoother flow of its content. Here's my suggestion (please feel free to agree with it, or not): 1-Introduction: clearly outline the importance and goals of bacterial-algal symbiotic reactors in wastewater treatment. Also, provide a brief overview of various reactor types. 2- Closed and open systems: Discuss closed systems (e.g., MBR, SBR, biofilm reactors) and their mechanisms, citing relevant studies. Explore open systems (High-Efficiency Algae Ponds, Algal Turf Scrubbers) and highlight key features. 3-Comparative analysis: Compare closed and open systems, emphasizing strengths and weaknesses. Highlight scenarios favoring one system over the other. 4-Challenges and ppportunitiess: consider to address the challenges in bacterial-algal symbiotic reactors (e.g., resource recycling, biofuel production). Also, you could discuss potential solutions and opportunities for improvement. Finally, section 5- Conclusions: Summarize key findings and stress the significance of bacterial-algal symbiotic reactors in advancing sustainable wastewater treatment. As well as highlight future research directions of your work on the topic.
15. I believe that the paper does not extensively discuss potential biases or limitations arising from the selective inclusion of studies in the review. Please revise it.
16. Please revise the paper to check for grammatical consistency. I suggest that the authors should consider thorough proofreading, with attention to maintaining consistent grammatical conventions.
17. How do the authors plan to address the discrepancy in reported biomass yields from different studies covered in the review?
18. Please add a section in the Conclusions highlighting future research directions for researchers interested in advancing this topic.
19. I believe that the authors could include a concise summary or graphical abstract representation comparing key features of the various reactors.
Comments on the Quality of English Language16. Please revise the paper to check for grammatical consistency. I suggest that the authors should consider thorough proofreading, with attention to maintaining consistent grammatical conventions.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors1. This paper introduces and summarizes several types of bacterial-algal reactors published previously. However, evaluation of each reactors system by the authors is not enough.
2. The important points of these comparison are how to show each characteristics
by a glance.
3. The tables should prepare for all configurations, including loads of pollutants,
removability of all pollutants, CO2 removability, properties of membranes,
advantages of each configuration, mechanism etc.
Comments on the Quality of English LanguageThe most parts of the content are understandable , but some minor revision is needed.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript “Research Progress on the Configurations and Performance of Reducing Pollution and Carbon Emissions by Bacterial-Algal Reactor” offered a detailed comparison of the different types of mycobacterial-algal symbiotic reactors. The topic is very interesting. Minor revision is suggested.
1. Through analysis, this article has obtained some conclusions and viewpoints, and it is recommended to include them in the abstract.
2. It is suggested to compare the differences between this article and previous literature, and further emphasize the novelty of this article in the introduction part.
3. It is recommended to replace all the figures in this article with colored ones and enhance the clarity of the figures.
4. Is it possible to use the Bacterial Algal Reactor to produce lipids? It is recommended to discuss this.
5. Some work such as “Combined transcriptomic and metabolomic analyses of temperature response of microalgae using waste activated sludge extracts for promising biodiesel production” can be updated to further improve the discussion of this article.
6. What are the main problems faced by the industrialization and large-scale application of Bacterial-Algal Reactor? How to solve these problems? It is recommended to discuss and look forward to this in the Summary and Outlook.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThe study is intended to determine the performance of different configurations of Bacterial-Algal Reactors regarding reduction of pollutants and CO2. However there is only systematic comparison of different reactor configurations in this manuscript detectible. Regarding the performance different values from individual publications are cited (not always correct, see bellow) with do not allow all the time a direct comparison of the performance. Also the amount of publications elaborated to each system I would increase to at least tree, in order to allow broader comparison. I recommend to accept this manuscript only after major revision. The manuscript need more structure regarding comparison of different systems. May suggestion is to apply the energy efficiency and biomass productivity as a common measure, to be able to compare different systems and individual publications.
Page 3
„A separate study by Sun[11] showed that the membrane fouling was improved under proper inoculation ratio compared with the conventional MBR, indicating the positive effect of algae system on mitigating membrane fouling in MBR.“ Membrane fouling is an negative effect for the process but here says it is improved and it seems like it positive for the process, please express more clearly!
“Radmehr et al[13] found that the ASB -MBR can reduce the amount of mechanical aeration by about 60% compared to the ordinary activated sludge MBR reactor, which accounts for about 60% of the total energy demand for the operation of MBRs[14].” Maybe it makes sense give also name percent of whole process cost/energy demand reduction (36 %)? For example like this: “This means that the ASB -MBR system can reduce aeration energy consumption and save operating costs by 36%.”
Page 4
“The removal rates of COD, NH4+-N, and TN in the bacterial-algae-SBR reactor were 99.45%, 99.93%, and 90.39% at lower aeration intensities (~0.02 vvm), while the removal rates of COD, NH4+-N, TN, and TP of single activated sludge were 98.36%, 83.51, 78.96%, and 97.75%, respectively.” Aeration rate for the single activated sludge is missing for complete comparison.
Page 8
“The study found that the average removal rates of COD and TKN were 76±11% and 88±6%, respectively, with a biomass yield range of 21-28mg/(m2·d) in between.” It is 21-28 g/(m2·d) not mg, huge difference!
Page 9
There are several publications regarding ATS systems. It would be good to have at least tree to be compared (DOI 10.1016/j.seppur.2022.122471) regarding biomass productivity.
Summary and Outlook do not contain any specific information in terms of productivity or energy efficiency of individual systems. I would expect some conclusions like most efficient systems have to fulfil some criteria like efficiency regarding input energy per g produced biomass or sequestrated CO2. This comparison can be applied for most of publication in order to compare them regardless different technical compilation.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have provided detailed feedback for all comments and questions that were addressed by this reviewer in the previous round. I agree with the modifications that have been made and I also appreciate the work associated with all these modifications. I have no more questions or comments to the authors and I believe that this revised and improved version of the manuscript can be considered for publication. The references should be edited to put them to the journal's standards.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe revised paper improved the content and description compared with the original one.
Comments on the Quality of English Language
The most parts of text give well-organized expression in English.
