Application of Bioelectrochemical Systems and Anaerobic Additives in Wastewater Treatment: A Conceptual Review

Round 1

Reviewer 1 Report

Madondo et al. review recent advances in bioelectrochemical systems and anaerobic additives in wastewater treatment. The manuscript is well organized and well presented, which adequate background and data are provided to understand. There are some comments for further improvement of the manuscript before publishing.

1. The Figure 1 shows a clear upward trend of bioelectrochemical study cases. How dose the claim make sense, “Despite such promising findings, the effect of bioelectrochemical processes and anaerobic additives on anaerobic digestion has been inadequately investigated”?

2. “In this process, the generated hydrogen is reduced to methane on the cathode...” in Page 11, is hydrogen reduced or oxidized here?

3. In section of 4.2.2, it would be great to add a table showing efficiencies of existing works. Thus, it can be easier for audience to know current progress.

4. In Figure 7, it shows the formation of protons during electron transfer but no molecular hydrogen. How does the process facilitate degradation? Where does the generated protons go in case of H+ accumulation?

5. When Acronym first appear in text, the backronym should be provided to help understand. For example, COD

Author Response

Thank you so much for your comments. Kindly see attached responses to your comments. 

Author Response File: Author Response.docx

Reviewer 2 Report

In this review-manuscript the authors have presented detailed information on types and synergistic influence of bioelectrochemical systems and anaerobic additives on the anaerobic digestion in wastewater treatment. The authors have conducted and published studies in the same area (doi.org/10.3390/catal12060642). Similar reviews exploring synergistic effect of materials and bioelectrochemical systems on Anaerobic Digestion have been previously published (doi.org/10.3390/bioengineering8120198; doi.org/10.1016/j.biortech.2021.126519;  doi.org/10.1080/12269328.2015.1037966). In this review, the authors discuss the types of additives used and their relevant effects on bioelectrochemical systems as it pertains to renewable energy systems. The manuscript is well written, the motivation is clear and has moderate significance in novelty of discussion. The contents of the manuscript are within the scope of the Journal. I would advise the authors to check on self-citations to make sure the papers (from their group) cited in the manuscript are highly relevant to the manuscript or remove them. The authors may modify their manuscript to make it better based on comments below:

1.       Please add relevant quantitative data (numbers with units) and reference numbers for each row for Tables 1 and 2.

2.       Figure 3: Please check the resolution of the image for final publication.

3.       Figure 5: May have scaling issues as figure appears stretched. Please check original scale and resolution of the image.

4.       Please add a diagram for metabolic, nanoparticle catalysis, and enzymatic method sections. Readers may find that useful.

5.       Would recommend the authors to add a table showing various approaches using nanoparticles, enzymes etc.

6.       Would recommend the authors to add more information on recent developments on common-nanoparticulate based treatment approaches such as the use of gold nanoparticles in industrial wastewater (10.1016/j.jhazmat.2011.10.057), flocculation based magnetic nanoparticles (doi.org/10.3390/w14030505), use of ultrafiltration membranes (doi.org/10.3390/chemengineering5030034) and silver nanoparticles (doi.org/10.1021/es1041892).

7.       Diagram for bioelectrochemical systems can also show repurposing for renewable energy generation. Authors may modify accordingly.

8.       Would recommend the authors to add a graph that can visualize both the scale and shift in material-use based on duration (years) in developments of wastewater treatment methodologies.

 

Author Response

Thank you so much for your comments. Kindly see attached responses to your comments. 

Author Response File: Author Response.docx