Recent Progress in Microalgae-Based Technologies for Industrial Wastewater Treatment

Round 1

Reviewer 1 Report

The manuscript “Recent Progress on Microalgae-Based Technologies for Industrial Wastewater Treatment” presents that the wastewater is disposed by the algae. The kind of algae, wastewater type, parameter for bioremediation are also discussed. The manuscript could be useful for the researchers who are interested to the wastewater treatment by the algae technology. Overall, this manuscript is meaningful, also meets the scope of Fermentation. However, several problems need be addressed, the specific comments are as following:

1.       What is the treatment method for the algae with heavy metals?

2.       The mechanism that algae for removing pollutant should be discussed more.

3.       The pH value is important for algae growth, different wastewaters occupy various pH values, the effect of pH on algae growth and pollutant removal need to be discussed.

4.       Figure 1 should be plotted more clear.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper review progress in microalgae-biotechnology for wastewater treatment. A brief overview on microalgae types/classification, cultivation and conditions was provided as well as the bioremediation of specific industrial wastewater. The contents of the review fall into the scope of Water. The manuscript is well-structured. The authors used recent articles published in the literature to support the discussion. The paper is recommended for publication after necessary revision.

1. The figure is not clear and necessary revision is suggested. Besides, the process and mechanism of the microalgae-biotechnology is suggested to illustrate in figure style, which is in accordance with the need for the work.

2. Although the perspectives on the potential scale-up of the technology and some critical considerations were discussed in the paper. The shortcomings of the microalgae-biotechnology as well as the challenges for full-scale demonstration are suggested to discuss. The future study field of the microalgae-biotechnology is also suggested to recommend based on the development trend.

3. Wastewater treatment is not identical to bioremediation. In the manuscript, both wastewater treatment as well as bioremediation were used. What is the difference between the two expressions？

4. The energy and nutrients recovery potential of the microalgae-biotechnology is suggested to emphasize besides of the contaminant removal.

5. For Table 7, Techno-Economical Aspects of Green and Conventional Processes, the comparison is good and necessary. Besides, the novel biological process for treating industrial wastewater is also suggested to mention, such as anammox process (https://doi.org/10.1016/j.biortech.2018.07.013).

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

In this manuscript, the authors reviewed the microalgae-based technologies for industrial wastewater treatment. This manuscript is poor and lacks originality. I believe it should be rejected.

In the 23 pages of the MS, the authors devote 8 pages to the description of microalgae and/or growth parameters and 2 pages to the bioremediation of heavy metal. Considering 5 pages for the bibliography and the space occupied by the tables, only a small fraction of the MS remains in relation to wastewater treatment by microalgae-based technologies. 

Comments

Abstract. Authors mentioned “perspectives on the potential scale-up of the technology and some critical considerations were also discussed” but there is only a small fraction of the MS about scaling up process in the conclusion section.

There are many language errors (tenses, singular/plural) and incomplete sentences in the script. Please check the sentence structure, tenses and language carefully.

 Page 3 line 112. 1.2.2 Phycoerythrin “Phycoerythrin is not a Phylum”

Page 3 line 138. “Algae is composed of 50% C, 10% N2, 2% P, and some other organic contents like protein, lipids, nucleic acid, and carbohydrates” This is not true. In fact Figure 1 shows how composition changes in each microalga strain.

Page 4 line 171. “Extensive research has been done on microalgae cultivation”. Please add some references here.

Please check the pros and cons in Table 1. I think that PBR vertical having small area is a pros. tPBR “pH, DO and CO2 fluctuation among the pipe length, wall might be foul (found??)” This is not always true. Depends on several parameters such as the mixing system.

Section 2.3. is mentioned twice.

3. Parametric evaluation of bioremediation. Here authors describe mainly the microalgal growth parameters.

Page 14 line 398. Replace “200 µmol/m2” and “300 μmol/m2,  with “200 µmol/(m2 s) and “300 μmol/(m2 s) respectively.

References should be checked for correctness since the references 13 and 16 cite the same article “Rasheed, T., Bilal, M., Nabeel, F., Adeel, M. & Iqbal, H. M. N. Environmentally-related contaminants of high concern: Potential sources and analytical modalities for detection, quantification, and treatment. Environment International 122, 52–66 (2019).”.

Also they are missing details in several cited articles. There are many articles with “author et al”

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors have revised their manuscript acknowledging my previous comments. However, this manuscript needs a major revision before publication.

Some comments:

Page 2 Line 80. “MG” I think MG stands for microorganism but where is the explanation?

Page 2 Line 82. The old reference number “26” is still there. Also, in page 6 line 162, Krishnamoorthy et al., corresponds to reference number 73 and not to number 75. Please check references numbering for correctness.

Page 6 Line 197. Please rephrase this sentence.

Page 8 Line 259-260. This sentence is incomplete.

Please put all microalgae names in italics.

Please follow the g/L format instead of g/l.

Author Response

General Comment: The authors have revised their manuscript acknowledging my previous comments. However, this manuscript needs a major revision before publication.

General Response: Thank you for the positive feedback from the reviewer. We appreciate the reviewer’s effort to go into every detail in assessing our manuscript. Thanks to the insightful inputs, now we have revised the manuscript accordingly. Below, we provide a point-by-point response to the reviewer's comments. Apart from the points raised by the reviewer, we have also improved the manuscript to enhance its readability. We hope that this version has met the high standard set by the reviewer.

Comment 1: Page 2 Line 80. “MG” I think MG stands for microorganism but where is the explanation?

Response 1: Thank you so much for pointing out the mistake. Page 2 Line 68 shows an explanation.

Comment 2: Page 2 Line 82. The old reference number “26” is still there. Also, in page 6 line 162, Krishnamoorthy et al., corresponds to reference number 73 and not to number 75. Please check references numbering for correctness.

Response 2: Thank you so much for pointing out the mistake. Page 2 Line 82, the old reference has been replaced with a new one as citation number [20]. On page 7, Krishnamoorthy et al. has been corrected, All the reference has been rechecked.

Comment 3: Page 6 Line 197. Please rephrase this sentence.

Response 3: The mentioned sentence has been rephrased.

Comment 4: Page 8 Line 259-260. This sentence is incomplete.

Response 4: Thank you for pointing out the mistake. The mentioned sentence has been corrected.

Comment 5: Please put all microalgae names in italics.

Response 5: All names have been put in italic.

Comment 6: Please follow the g/L format instead of g/l.

Response 6: All g/l has been replaced with g/L.