Algal–Bacterial Symbiotic Granular Sludge Technology in Wastewater Treatment: A Review on Advances and Future Prospects

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General comment:

The manuscript is well-organized, providing a thorough look at the algal-bacterial granular role of sludge technology in sustainable wastewater treatment. It effectively demonstrates the ability of the technology to eliminate organic materials, nutrients, and heavy metals. The review draws from extensive research and real-world examples, making it a significant resource for both researchers and practitioners in the field.

 

Suggestions for Improving the Manuscript:

1. There are sections with repetitive information that should be streamlined for clarity. For instance, discussions on system stability and shock resistance appear in multiple sections (such as 4.4 and 5.4). Merging these sections can enhance readability.
2. Tables 1 and 2, which provide a comparison of reactor types and list optimal operating parameters, require clearer formatting. Improve the table captions, ensure units are consistent, and make headings easy to understand.
3. The manuscript cites several figures (like Figures 1-5), yet they are absent from the text. Ensure these figures are included and properly labeled to complement the text.
4. Some claims lack proper citations, reducing their credibility. For example, the economic benefits of algal-bacterial systems discussed in Section 5.1 need specific references. Adding citations will strengthen these claims and ensure proper source attribution.
5. The use of technical jargon might be challenging for those not specialized in the field. Simplifying the language or providing explanations for key terms would make the manuscript more accessible. Including a glossary for complex terms could also help engage a wider scientific audience.
6. While detailing the microbial community composition, it is important to clearly explain the role of specific microorganisms, such as Chlorella and Scenedesmus, in the granulation process.
7. Address the trade-offs between different reactor types, focusing on aspects like cost versus efficiency, to help readers make informed choices.
8. Provide more information on long-term performance and scalability challenges to present a balanced perspective. Discuss the potential environmental impact of scaling up this technology, including aspects like reducing the carbon footprint.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Research and Prospect Analysis of Algae Bacteria Symbiotic Granular Sludge Technology in Wastewater Treatment”(ID:water-3520905).Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval.

The main corrections in the paper and the responds to the reviewer’s comments are as flowing:

1.There are sections with repetitive information that should be streamlined for clarity. For instance, discussions on system stability and shock resistance appear in multiple sections (such as 4.4 and 5.4). Merging these sections can enhance readability.

The author's answer：We apologize for the fact that some of the information in the article is repetitive, and we have made some deletions and changes to section 4.4 of the article to improve the readability of the article.

2.Tables 1 and 2, which provide a comparison of reactor types and list optimal operating parameters, require clearer formatting. Improve the table captions, ensure units are consistent, and make headings easy to understand.

The author's answer：As suggested by the evaluators, we have revised the table headings in Tables 1 and 2 to ensure that they are formatted consistently and are visible in Line272 and Line312 in the text.

3.The manuscript cites several figures (like Figures 1-5), yet they are absent from the text. Ensure these figures are included and properly labeled to complement the text.

The author's answer：Taking into account the evaluator's suggestion, we have marked the image in the text and annotated accordingly, and the introduction points can be found in Line92, Line129, Line130 and Line150 in the text.

4.Some claims lack proper citations, reducing their credibility. For example, the economic benefits of algal-bacterial systems discussed in Section 5.1 need specific references. Adding citations will strengthen these claims and ensure proper source attribution.

The author's answer：It is really true as Reviewer suggested that We did not provide sufficient references for the discussion of the economic benefits of algae-bacterial systems, for which we introduced references, Line545 in the text, Ref. [109].

5.The use of technical jargon might be challenging for those not specialized in the field. Simplifying the language or providing explanations for key terms would make the manuscript more accessible. Including a glossary for complex terms could also help engage a wider scientific audience.

The author's answer：We added annotations after some nouns, such as lines 182 and 261.

6.While detailing the microbial community composition, it is important to clearly explain the role of specific microorganisms, such as Chlorella and Scenedesmus, in the granulation process.

The author's answer：We have made corrections based on the comments of the reviewers, and in the article Line105 introduces the role of chlorella in algae-bacterial granular sludge systems.

7.Address the trade-offs between different reactor types, focusing on aspects like cost versus efficiency, to help readers make informed choices.

The author's answer：We have revised this section based on the reviewers' suggestions, and we have added a new paragraph in Section 3.1 to weigh the trade-offs between different reactor types to help readers make an informed choice.

8.Provide more information on long-term performance and scalability challenges to present a balanced perspective. Discuss the potential environmental impact of scaling up this technology, including aspects like reducing the carbon footprint.

The author's answer：We have added a discussion on the carbon footprint in line 575.

Thank you very much for your attention and time Look forward to hearing from you

Yours sincerely,

ShengNan-Chen

03-May-2025

Qingdao University of Technology

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript reports on cultivation method and efficiency of fungal symbiotic granular sludge for wastewater treatment. This is an interesting topic in the area of wastewater treatment. However, some information need to be included in the manuscript as below:

1)‘A Review’ should be included in the title.

2)L39: Algae are aerobic organisms. How pumping/providing CO2 can help algae to grow faster? Please check this out or explain with references and relevant mechanism.

3)Fig 1: Title need more details; Can authors indicate what the growth media and cultured/grown microorganisms are in each case; A, B, …?  

4)Fig 2: Title need more details; Can authors indicate what microorganism each image represents? Or at least by shape, arrangement or color?

5)Fig 3: Abbreviates on x-axis need to be described under title.

6)Each graph/figure needs relevant explanation and discussion in the text.

7)Fig 3: The two graphs should be labeled a and b and need to be distinguished and explained in the title and in the text why they are different.

8)L135: What is the structure of this polymers? Carbohydrates? Proteins? Not indicated.

9)Table 2: What are the references for this information?

10)Can authors add a section for importance and mass transfer and diffusion effect on granulation and process efficiency? Als, the importance of granule size?

 

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Research and Prospect Analysis of Algae Bacteria Symbiotic Granular Sludge Technology in Wastewater Treatment”(ID:water-3520905).Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval.

The main corrections in the paper and the responds to the reviewer’s comments are as flowing:

1.‘A Review’ should be included in the title.

The author's answer：As suggested by the evaluators, we have revised the title "Research and Prospect Analysis of Algae Bacteria Symbiotic Granular Sludge Technology in Wastewater Treatment" to a new title "Algae-Bacteria Symbiotic Granular Sludge". Technology in Wastewater Treatment: A Review on Advances and Future Prospects".

2.L39: Algae are aerobic organisms. How pumping/providing CO2 can help algae to grow faster? Please check this out or explain with references and relevant mechanism.

The author's answer：Sorry for the fact that there is no mention in this article about how algae can contribute to the growth rate of algae by providing carbon dioxide, we have added it to the new position in the article as Line42

3.Fig 1: Title need more details; Can authors indicate what the growth media and cultured/grown microorganisms are in each case; A, B, …? 

The author's answer：We updated the explanation after Figure 1, detailing the meaning of Figure 1.

4.Fig 2: Title need more details; Can authors indicate what microorganism each image represents? Or at least by shape, arrangement or color?

The author's answer：Taking into account the evaluator's suggestion,We have annotated Figure 2 more, a scanning electron microscope image of a particle sample, and a new Figure 2 title can be seen in Line119 in the article.

5.Fig 3: Abbreviates on x-axis need to be described under title.

The author's answer：We have added new annotations regarding the meaning of the data on the X-axis in line 136.

6.Each graph/figure needs relevant explanation and discussion in the text.

The author's answer：Taking into account the evaluator's suggestion, we have marked the image in the text and annotated accordingly, and the introduction points can be found in Line92, Line129, Line130 and Line150 in the text.

7.Fig 3: The two graphs should be labeled a and b and need to be distinguished and explained in the title and in the text why they are different.

The author's answer：We have revised this section based on the reviewers' suggestions,We divided it into group 1 and group 2 and explained the differences, in the article Line138.

8.L135: What is the structure of this polymers? Carbohydrates? Proteins? Not indicated.

The author's answer：We're sorry for this in our article, we've added a substance-specific introduction to Line148 in the article.

9.Table 2: What are the references for this information?

The author's answer：We marked the data source literature after each parameter in the parameter column.

10.Can authors add a section for importance and mass transfer and diffusion effect on granulation and process efficiency? Als, the importance of granule size?

The author's answer：Thanks to the reviewers' suggestions, we have included a Section 3.4 Line387 article to describe the effects of mass transfer and diffusion effects on granulation and process efficiency.

Thank you very much for your attention and time Look forward to hearing from you.

Yours sincerely,

ShengNan-Chen

03-May-2025

Qingdao University of Technology

Reviewer 3 Report

Comments and Suggestions for Authors

General comments

The manuscript titled “Research and Prospect Analysis of Algae Bacteria Symbiotic Granular Sludge Technology in Wastewater Treatment” provides an overview of the research conducted on technologies for purifying contaminated water, specifically focusing on the application of granular sludge derived from the symbiotic relationship between various algal and bacterial species.

This paper deals with a very interesting topic, well-structured and elaborated.

The template supplied is neither in accordance with the specifications for the Journal Water nor with the editorial standards for the current publishing year.

I am sorry but, since I only have access to the pdf, I cannot review the format of the entire article, although I have checked that it is not in accordance with the guidelines provided by Water.

Based on the review of the provided manuscript here are my comments and recommendations:

I like the way the problem has been introduced in the abstract. It does a good job of summarizing the primary goals, procedures, and previous results.

Regardless of the format not adhering to journal’s guidelines, there are typographical errors requiring correction, such as the missing spaces on lines 32, 37, 40, 43, 45, 49, and so forth. I would recommend a deep review of format, not only of the text but of the tables.

Having reviewed your citation number 7, I would recommend using the term “phosphorus” rather than “phosphate”.

I appreciate the quality of the images.

The comparative analysis of the different technologies in Table 1 is well-executed.

All references must be reviewed and adjusted to conform to the template provided by the journal’s template.

Conclusions are in accordance with the review developed.

Despite my appreciation for the article’s structure and overall quality, the presence of many typographical and formatting errors means it cannot be accepted in its current form.

 

Comments for author File: Comments.pdf

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Research and Prospect Analysis of Algae Bacteria Symbiotic Granular Sludge Technology in Wastewater Treatment”(ID:water-3520905).Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval.

The main corrections in the paper and the responds to the reviewer’s comments are as flowing:

Thank you for the reviewers' suggestions, I'm glad you liked the structure of the article as well as the overall quality, and we're sorry that our article format doesn't conform to Journal Water's specifications, so we have not only made your proposed changes to lack spaces between natural paragraphs, using the term "phosphorus" instead of "phosphate", reviewing and adjusting all references to conform to the template provided by the journal template, etc.

Thank you very much for your attention and time Look forward to hearing from you

Yours sincerely,

ShengNan-Chen

03-May-2025

Qingdao University of Technology

Reviewer 4 Report

Comments and Suggestions for Authors

title too broad and unspecific, need to narrow down'

abstract too general, and mostly with sweeping statements, failed to highlight main research significant from this review study

Many figures provided are extracted/adopted from past studies, kindly ensure copyrights and permission obtained. and if possible, avoid doing so. Highly recommend to create own graphical abstract and create own figures related to your scope of review paper. Unless you have strong justifications for it in the current version.

 

 

Comments for author File: Comments.pdf

Author Response

Dear Editors and Reviewers:

 

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Research and Prospect Analysis of Algae Bacteria Symbiotic Granular Sludge Technology in Wastewater Treatment”(ID:water-3520905).Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval.

 

The main corrections in the paper and the responds to the reviewer’s comments are as flowing:

 

 

1. Title too broad and unspecific, need to narrow down

 

Author response: Based on the reviewers’ suggestions, we have revised the title to clarify that this paper is a review, and with minor modifications, we have changed the title “Research and Prospect Analysis of Algae-Bacteria Symbiotic Granular Sludge Technology in Wastewater Treatment” to the new title “Algae-Bacteria Symbiotic Granular Sludge”. Wastewater treatment technologies: A review of progress and future prospects”.

 

2.Abstract too general, and mostly with sweeping statements, failed to highlight main research significant from this review study

 

Authors' response: Based on the evaluators' suggestions, we have rewritten the abstract of this article to comply with your suggestions.

 

3. Many figures provided are extracted/adopted from past studies, kindly ensure copyrights and permission obtained. and if possible, avoid doing so. Highly recommend to create own graphical abstract and create own figures related to your scope of review paper. Unless you have strong justifications for it in the current version.

 

Author's answer: We have sent emails to the authors of the cited literature to obtain authorization, and the chart comparison has also been optimized.

 

Thank you very much for your attention and time Look forward to hearing from you

 

Yours sincerely,

 

ShengNan-Chen

 

03-May-2025

 

Qingdao University of Technology

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Authors have made the appropriate corrections. The manuscript is now suitable for acceptance.

Author Response

Dear Reviewer , 

 

Thank you for your encouraging feedback and confirmation that the manuscript now meets the journal's standards. We are grateful for your thorough review and insightful suggestions, which have significantly strengthened this work. 

 

We confirm that all revisions have been carefully implemented as per the reviewers' and editors' comments. Please let us know if any additional clarifications are needed prior to formal acceptance. 

 

Sincerely, 

Shengnan Chen

On behalf of all authors 

Reviewer 2 Report

Comments and Suggestions for Authors

Authors put some effort to address the comments. Unfortunately, the answers do not match with the line in the text. Even the modified title of the manuscript is not carefully reflected in the revised version. Also, each correction needs to be carefully relevant to the comment. Authors should consider what they are asked to do as a correction to improve the manuscript.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Research and Prospect Analysis of Algae Bacteria Symbiotic Granular Sludge Technology in Wastewater Treatment”(ID:water-3520905).We are very sorry that we did not fully understand and correct all your opinions. We are striving to make our article look more perfect. The following are our further corrections based on your suggestions.

1.‘A Review’ should be included in the title.

The author's answer：As suggested by the evaluators, we have revised the title "Research and Prospect Analysis of Algae Bacteria Symbiotic Granular Sludge Technology in Wastewater Treatment" to a new title "Algae-Bacteria Symbiotic Granular Sludge". Technology in Wastewater Treatment: A Review on Advances and Future Prospects".

2.L39: Algae are aerobic organisms. How pumping/providing CO2 can help algae to grow faster? Please check this out or explain with references and relevant mechanism.

The author's answer：Thank you very much for your question. We have supplemented the specific promotion mechanism after the sentence. We have added it to a new position in the article as Line42-48.

3.Fig 1: Title need more details; Can authors indicate what the growth media and cultured/grown microorganisms are in each case; A, B, …? 

The author's answer：We updated the explanation after Figure 1, detailing the meaning of Figure 1. We have added it to a new position in the article as Line102-104.

4.Fig 2: Title need more details; Can authors indicate what microorganism each image represents? Or at least by shape, arrangement or color?

The author's answer：Taking into account the evaluator's suggestion,We have annotated Figure 2 more, a scanning electron microscope image of a particle sample, and a new Figure 2 title can be seen in Line122-125 in the article.

5.Fig 3: Abbreviates on x-axis need to be described under title.

The author's answer：We have added new annotations regarding the meaning of the data on the X-axis in line 141-148.

6.Each graph/figure needs relevant explanation and discussion in the text.

The author's answer：Taking into account the evaluator's suggestion, we have marked the image in the text and annotated accordingly, and the introduction points can be found in Line92, Line129, Line130 and Line150 in the text.

7.Fig 3: The two graphs should be labeled a and b and need to be distinguished and explained in the title and in the text why they are different.

The author's answer：We have revised this section based on the reviewers' suggestions,We divided it into group 1 and group 2 and explained the differences, in the article Line141-148 and Line136-139.

8.L135: What is the structure of this polymers? Carbohydrates? Proteins? Not indicated.

The author's answer：We're sorry for this in our article, we've added a substance-specific introduction to Line132-139 in the article.

9.Table 2: What are the references for this information?

The author's answer：We marked the data source literature after each parameter in the parameter column.

10.Can authors add a section for importance and mass transfer and diffusion effect on granulation and process efficiency? Als, the importance of granule size?

The author's answer：Thanks to the reviewers' suggestions, we have included a Section 3.4 Line392-404 article to describe the effects of mass transfer and diffusion effects on granulation and process efficiency.

Thank you very much for your attention and time Look forward to hearing from you

Yours sincerely,

ShengNan-Chen

Qingdao University of Technology

Reviewer 3 Report

Comments and Suggestions for Authors

Based on the review of the provided manuscript here are my comments and recommendations:

I truly appreciate the improvement of the paper after corrections.

After reviewing corrections made, I highlight that the date that appears in the paper continues being 2022 instead of 2025, as it was made in my first review.

Furthermore, various typographical error and missing spaces after full stops continue to appear throughout the entire tex. I would appreciate that this minor mistake could be solved.

As current template has not been used, several discrepancies continue to be observed. That is the case of the page numbering is incorrect and in the case of references, for example, authors’ names should not be capitalised, the year should be in bold, and the journal names should be in italicised and abbreviated, etc.

I consider the manuscript very interesting and improved after recommendations but I cannot recommend it to be published in its present form.

 

Comments for author File: Comments.pdf

Author Response

Dear Reviewer ,

Thank you for your significant reminding.  According to your suggestion, we corrected the above grammatical errors and made an effort to correct the spelling and grammar errors and polish the whole manuscript.  We would like to confirm that the suitably revised manuscript is understandable to readers.

We greatly appreciate your rigorous feedback, which has significantly improved the quality of this work. Please let us know if further revisions are needed.

Reviewer 4 Report

Comments and Suggestions for Authors

The title maybe can be further improved, "Research and Prospect" perhaps can change to Prospects Analysis of Algae...

Author Response

Dear Reviewer ,

Thank you for identifying this area for improvement. We have carefully revised the manuscript according to your suggestion. The specific changes are outlined below:

Original Text (Lines 525):
" Economic evaluation and development prospects "

Revised Text:
" Economic evaluation and prospects analysis of algae "

We confirm that all revisions have been carefully implemented as per the reviewers' and editors' comments. Thank you very much for your revision suggestions.

 

Sincerely, 

Shengnan-Chen

On behalf of all authors 

Round 3

Reviewer 2 Report

Comments and Suggestions for Authors

The comments are addressed carefully and the manuscript is suggested for publication.

Reviewer 3 Report

Comments and Suggestions for Authors

I consider that after revisions made, the manuscript is adequate to be publish in its present form.

Comments for author File: Comments.pdf