Microbial Fuel Cell United with Other Existing Technologies for Enhanced Power Generation and Efficient Wastewater Treatment

Round 1

Reviewer 1 Report

English in presented manuscript “Microbial Fuel Cell united with other existing technologies for enhanced power generation and efficient wastewater treatment”, especially in the first part, need to be improved. There are some grammar mistakes which make the text more difficult to understand, e.g.:

• “Lab” is rather a colloquial term. “Laboratory scale” is much better.
• In Abstract: “Nowadays, global energy is in an energy crisis because of heavy energy demand”. – there is too much energy in this sentence.
• Lines 130-131: “[…] there are numerous difficulties are remaining to resolved yet […]”
• Line 579: “1.52E-0.2kgCO2-eq” – must be corrected.

Moreover, below, please find my detailed comments and questions:

• Sometimes the full name of MFC is written with capital letter, sometimes with small. Please unify.
• In the text there is lack of description of general MFC construction and working mechanism.
• In the chapter “Stand-alone bio-electrochemical system and their limitations” there are almost no results of wastewater treatment from literature.
• Lines 88-91: “When membrane-less BESs with a distinct compartment was used, there were difficulties such as less energy retrieval and pollution. Another problem is to choose an appropriate cathode.” What type of pollution? Why the cathode choose is a problem?
• Chapter 3 (LCA of MFC) should be definitely expanded with the next few examples.
• Lines 69-71: “These new integrated techniques provide a versatile environment for tackling some difficult challenges […] This paper discusses various categories of integrated MFCs system” – however only 17/89 cited papers are “new” (from past 5 years). Could Authors add and discuss more of recent literature regarding MFC?

Concluding, I suggest major revision of presented article, with the potential for acceptance after Authors’ corrections.

Author Response

Response to reviewers' comments

Manuscript ID: applsci-1426339

Title: Microbial Fuel Cell united with other existing technologies for enhanced power generation and efficient wastewater treatment

The authors would like to appreciate all the reviewers and the editor for their valuable suggestions and comments involved in enhancing the standard of our manuscript. The Authors have incorporated a series of modifications (Page no. 15, Line 1330: Figure 4: A typical integrated sediment-MFC; Page no. 18, Line 1436: Figure 6: A typical representation of constructed wetlands-MFCs; Page no. 21, Line 1624: Figure 7: Illustration of Algae assisted cathode in MFC; Page no. 22, Line 1658: Figure 8: A) Integrated MFC-AA/O system for wastewater treatment; B) Integrated MFC-Septic tank for wastewater treatment; Page no. 12, Line 1130: Table 1: Integrated Systems of microbial fuel cells (MFCs)with Various Techniques;  Page no. 16, Line 1377: Table 2: Several studies demonstrating the performance of sediment MFC; Latest Integration studies: Page no. 10, Line 1054-1072: In another study, microbial fuel cell was integrated with anaerobic forward osmosis membrane bioreactors for generation of biogas,……This study found that integrating an electrocatalytic-assisted MEC into AnOMBR is an excellent method for industrial-scale biofuel generation [50]; Page no. 11, Line 1073-1085: In another experiment, it was observed that, The benefits of organic elimination, bioenergy production, and high-quality water recovery…….the findings of the experiment revealed that water-flux-facilitated proton advection was more essential than NPC-flux-promoted countercurrent proton exchange in regulating the power production in an OsMFC [51]; Page no. 13, Line 1155-1166: An innovative integrated single-stage Dark Fermentation-Microbial fuel cells (MFCs) method was designed………integrated system was capable of achieving a maximum voltage of 459 mV (367 mW) and a maximum cell efficacy of 44% (fuel consumption of 1.5 ×105 mol/h) [57]; Page no. 13, Line 1167-1177: A hybrid approach of dark fermentation (DF) and microbial fuel cell (MFC), known as sDFMFC,………H₂ and energy from a variety of biomass feedstocks while maintaining the individual DF and MFC processes' efficiency [58]; Page no. 15, Line 1340-1350: Quaglio et al. present an effective way for improving power extraction using SMFCs by alternating the anodes……..The Anode Alternation can also be considered of as a step forward in the field of intermittent energy harvesting [65]; Page no. 15, Line 1351-1375: In another study, the power generation capability of mixed-culture algal biomass was investigated using a multi-anode sediment microbial fuel cell (SMFC)………These findings suggested that algal biomass might be employed as a suitable feedstock in SMFCs to enhance electricity output significantly [66]; Page no. 19, Line 1492-1501: Wen et al. investigated the extraction efficiency of sulfamethoxazole (SMX), tetracycline (TC),…….MFC-CWs with plant and circuit connections have the ability to treat SMX and TC-containing wastewater [78]; Page no. 19, Line 1502-1509: The study was conducted by Mittal et al. to design a unique earthen membrane-based two-chambered wetland cum microbial fuel cell (CW-MFC)……..azo dye absorption, with current density and power density output of 544.6 mA/m³ and 148.29 mW/m³, respectively [79]; Page no. 18, Line 1510-1527: The up-flow constructed wetland-MFC system with various fillers were designed for removal of Cr (VI)……..the extensive Cr(VI) stress, microbial diversity in the cathode was higher than in the anode, and Acetoanaerobium and Exiguobacterium were the leading genera in the anode and cathode, respectively [80]; Page no. 20, Line 1600-1631: During the anaerobic digestion of Taihu blue algae, biohydrogen employing migrating ammonia as a nitrogen supply……..As a result, performing ammonia mitigation, hydrogen production, and biogas upgrading all at the same time with BES appears to be an effective approach [90]; Page no. 20, Line 1636-1659: 2.9. Anaerobic-Anoxic-Oxic (AA/O) integrated with MFC An MFC was also combined into an anaerobic-anoxic-oxic (AO/O) system, resulting in a hybrid system…….Because no external energy was required, the system was declared sustainable and viable, and the treated effluent met the local discharge standard; Page no. 24, Line 1728-1737: LCA Studies: Overall, three tasks are done by osmotic MDC integrated system that are- removal of salts, treatment of wastewater and generation of electricity. Although lab scale systems showed as good as 90% desalination, removal of salts from natural water sources has shown less efficiency.…..lesser contribution to greenhouse gas emissions were found when compared to conventional desalination systems directing towards a hope for sustainable development of the integrated system).

Reviewer #1

English in presented manuscript “Microbial Fuel Cell united with other existing technologies for enhanced power generation and efficient wastewater treatment”, especially in the first part, need to be improved. There are some grammar mistakes which make the text more difficult to understand, e.g.:

R1Q1: “Lab” is rather a colloquial term. “Laboratory scale” is much better.

R1A1: The authors are grateful to the reviewer’s suggestions. “Lab” has been replaced by “Laboratory” in the revised manuscript as per your suggestion.

R1Q2: In Abstract: “Nowadays, global energy is in an energy crisis because of heavy energy demand”. – there is too much energy in this sentence.

R1A2: Noted, thank you for pointing it out. The line has been changed in the revised manuscript.

R1Q3: Lines 130-131: “[…] there are numerous difficulties are remaining to resolved yet […]”

R1A3: Thank you for highlighting that out, we have rectified the mistake in Line 183 of the revised manuscript.

R1Q4: Line 579: “1.52E-0.2kgCO2-eq” – must be corrected.

R1A4: The particular line has been removed in the revised manuscript.

Moreover, below, please find my detailed comments and questions:

R1Q5: Sometimes the full name of MFC is written with capital letter, sometimes with small. Please unify.

R1A5: The changes have been done and MFC is used in the revised manuscript as suggested.

R1Q6: In the text there is lack of description of general MFC construction and working mechanism.

R1A6: The general mechanism of MFC has been included along with the typical MFC diagram in Line 112-124 in the revised manuscript as per your suggestion.

R1Q7: In the chapter “Stand-alone bio-electrochemical system and their limitations” there are almost no results of wastewater treatment from literature.

R1A7: As per suggestions, the authors have incorporated relevant studies (Page no. 4, Line 492-499: Ghadge and Ghangrekar (2015) constructed a 26L cheap air cathode MFC employing clayware as a divider, claiming that the efficiency………the MFC had a maximum power of 17.85 mW and removed 78 percent of COD; Page no. 4, Line 272-281: Feng et al. created a stacked large scale horizontally constructed MFC (SHMFC) with such an overall capacity of 250 L that employs carbon brush electrodes to extract 116 mW of current (0.435 A) while also treating sewage………These SHMFC components may be used independently to process sewage and generate electricity without interfering with other SHMFC modules.) with information on wastewater treatment.

R1Q8: Lines 88-91: “When membrane-less BESs with a distinct compartment was used, there were difficulties such as less energy retrieval and pollution. Another problem is to choose an appropriate cathode.” What type of pollution? Why the cathode choose is a problem?

R1A8: Thank you for highlighting that out, we have rectified the mistake in Line 135-143 of the revised manuscript.

R1Q9: Chapter 3 (LCA of MFC) should be definitely expanded with the next few examples.

R1A9: The authors have researched in several literatures but up to most of our knowledge there are not many LCA studies conducted on integrated systems. However, we have incorporated some (Page no. 24, Line 1728-1737: Overall, three tasks are done by osmotic MDC integrated system that are- removal of salts, treatment of wastewater and generation of electricity. Although lab scale systems showed as good as 90% desalination, removal of salts from natural water sources has shown less efficiency.…..lesser contribution to greenhouse gas emissions were found when compared to conventional desalination systems directing towards a hope for sustainable development of the integrated system) in the revised manuscript.

R1Q10: Lines 69-71: “These new integrated techniques provide a versatile environment for tackling some difficult challenges […] This paper discusses various categories of integrated MFCs system” – however only 17/89 cited papers are “new” (from past 5 years). Could Authors add and discuss more of recent literature regarding MFC?

R1A10: As suggested, we have added recent literature regarding integrated MFCs (Page no. 10, Line 1054-1072: In another study, microbial fuel cell was integrated with anaerobic forward osmosis membrane bioreactors for generation of biogas,……This study found that integrating an electrocatalytic-assisted MEC into AnOMBR is an excellent method for industrial-scale biofuel generation [50]; Page no. 11, Line 1073-1085: In another experiment, it was observed that, The benefits of organic elimination, bioenergy production, and high-quality water recovery…….the findings of the experiment revealed that water-flux-facilitated proton advection was more essential than NPC-flux-promoted countercurrent proton exchange in regulating the power production in an OsMFC [51]; Page no. 13, Line 1155-1166: An innovative integrated single-stage Dark Fermentation-Microbial fuel cells (MFCs) method was designed………integrated system was capable of achieving a maximum voltage of 459 mV (367 mW) and a maximum cell efficacy of 44% (fuel consumption of 1.5 ×105 mol/h) [57]; Page no. 13, Line 1167-1177: A hybrid approach of dark fermentation (DF) and microbial fuel cell (MFC), known as sDFMFC,………H₂ and energy from a variety of biomass feedstocks while maintaining the individual DF and MFC processes' efficiency [58]; Page no. 15, Line 1340-1350: Quaglio et al. present an effective way for improving power extraction using SMFCs by alternating the anodes……..The Anode Alternation can also be considered of as a step forward in the field of intermittent energy harvesting [65]; Page no. 15, Line 1351-1375: In another study, the power generation capability of mixed-culture algal biomass was investigated using a multi-anode sediment microbial fuel cell (SMFC)………These findings suggested that algal biomass might be employed as a suitable feedstock in SMFCs to enhance electricity output significantly [66]; Page no. 19, Line 1492-1501: Wen et al. investigated the extraction efficiency of sulfamethoxazole (SMX), tetracycline (TC),…….MFC-CWs with plant and circuit connections have the ability to treat SMX and TC-containing wastewater [78]; Page no. 19, Line 1502-1509: The study was conducted by Mittal et al. to design a unique earthen membrane-based two-chambered wetland cum microbial fuel cell (CW-MFC)……..azo dye absorption, with current density and power density output of 544.6 mA/m³ and 148.29 mW/m³, respectively [79]; Page no. 18, Line 1510-1527: The up-flow constructed wetland-MFC system with various fillers were designed for removal of Cr (VI)……..the extensive Cr(VI) stress, microbial diversity in the cathode was higher than in the anode, and Acetoanaerobium and Exiguobacterium were the leading genera in the anode and cathode, respectively [80]; Page no. 20, Line 1600-1631: During the anaerobic digestion of Taihu blue algae, biohydrogen employing migrating ammonia as a nitrogen supply……..As a result, performing ammonia mitigation, hydrogen production, and biogas upgrading all at the same time with BES appears to be an effective approach [90]; Page no. 20, Line 1636-1659: 2.9. Anaerobic-Anoxic-Oxic (AA/O) integrated with MFC An MFC was also combined into an anaerobic-anoxic-oxic (AO/O) system, resulting in a hybrid system…….Because no external energy was required, the system was declared sustainable and viable, and the treated effluent met the local discharge standard.) in the revised manuscript.

Concluding, I suggest major revision of presented article, with the potential for acceptance after Authors’ corrections.

Author Response File: Author Response.pdf

Reviewer 2 Report

Greetings, Editor thank you for providing me with the opportunity to review the article. I reviewed the article by Patwardhan et al. with title `` Microbial Fuel Cell united with other existing technologies for  enhanced power generation and efficient wastewater treatment ``. The theme of the article is very interesting and promising in the field, but present article have some flaws which need to be address before publication. I am pleased to send you major level comments. The manuscript can be accepted for publication after modification. Please consider these comments/suggestions as listed below.

Comments:

1. The title seems good, but the abstract is totally weird. The first line seems weird. Please revised thoroughly the abstract, it does not communicate your idea in its existing form.
2. The MFC is Microbial fuel cell. Author used microbial fuel (MFC); it is wrong. Please revise your paper accordingly since same issue occurs on several spots in the paper.
3. The novelty of the work must be clearly addressed and discussed, compare and highlight novelty. What is novelty of this review?
4. Is it MFCs or MFC...?? Please stick to one abbreviation and be consistent with it in entire text.
5. Please define the term and next used abbreviation throughout the article. Please revise your paper accordingly since same issue occurs on several spots in the paper.
6. The main objective of the work must be written on the more clear and more concise way at the end of introduction section.
7. Reference 1 is not relevant reference for this statement. Please cite these two references (i) Outlook on the role of microbial fuel cells in remediation of environmental pollutants with electricity generation (ii) Asim AY, Mohamad N, Khalid U, Tabassum P, Akil A, Lokhat D, Siti H. A glimpse into the microbial fuel cells for wastewater treatment with energy generation. Desalination and Water Treatment. 2021;214:379-89.
8. Introduction section must be written on more quality way, i.e., more up-to-date references addressed. Research gap should be delivered on more clear way with directed necessity for the future research work.
9. Page 2, Line 62 need a reference. Please consider this ``Modern trend of anodes in microbial fuel cells (MFCs): an overview``. What is meaning of this sentence `` electrode fouling, outside of the lab``.
10. Author should provide the permission if they adapted these all figures. Please confirm and check.
11. Several abbreviations are not defined. Please check.
12. All heading/subheading should be in one style such as Integration of MFCs with Dark fermentation. Its wrong. It should be `` Integration of MFCs with Dark Fermentation``. Please check thoroughly.
13. Page 10, Line 371, the 49 percent. Its should be %. Please stick to one term (% or percent) and be consistent with it in entire text. Please revise your paper accordingly since same issue occurs on several spots in the paper.
14. Page 11, Line 409 need reference, please cite these references (i) Electricity generation and heavy metal remediation by utilizing yam (Dioscorea alata) waste in benthic microbial fuel cells (BMFCs) (ii) Application of rotten rice as a substrate for bacterial species to generate energy and the removal of toxic metals from wastewater through microbial fuel cells.
15. Reference 56 is not about BMFCs please replace by this reference; Cellulose derived graphene/polyaniline nanocomposite anode for energy generation and bioremediation of toxic metals via benthic microbial fuel cells.
16. Zhang and He (2013) and Zhang and He (2015) reference citation style is wrong. It should be Zhang et al. (2013). Please follow the journal guidelines.
17. Please provide the space between number and units such as 34W/m³. Please revise your paper accordingly since same issue occurs on several spots in the paper.
18. There are a lot of grammatical and language error such as Congo red? C should be in small letter. Please revise your paper accordingly since same issue occurs on several spots in the paper.
19. Commercialization and Practicality for this please consider and cite this article (Development and modification of materials to build cost-effective anodes for microbial fuel cells (MFCs): An overview) to write something advance.
20. What about the electrode challenge which is the hottest talk in the field? Please look this article (Recent advances in anodes for microbial fuel cells: An overview) to add about electrode challenges specially anode.
21. In table 2, please use one term Power generation or Power density . While Table 1 remove the term performance and specify the power density and removal efficiency.
22. Conclusion section is missing some perspective related to the future research work. Please improve this section carefully. I also did not understand your conclusion. What reader can get in conclusion?
23. English need major level revision through the manuscript. Several spot have grammatical errors.

Author Response

Response to reviewers' comments

Manuscript ID: applsci-1426339

Title: Microbial Fuel Cell united with other existing technologies for enhanced power generation and efficient wastewater treatment

The authors would like to appreciate all the reviewers and the editor for their valuable suggestions and comments involved in enhancing the standard of our manuscript. The Authors have incorporated a series of modifications (Page no. 15, Line 1330: Figure 4: A typical integrated sediment-MFC; Page no. 18, Line 1436: Figure 6: A typical representation of constructed wetlands-MFCs; Page no. 21, Line 1624: Figure 7: Illustration of Algae assisted cathode in MFC; Page no. 22, Line 1658: Figure 8: A) Integrated MFC-AA/O system for wastewater treatment; B) Integrated MFC-Septic tank for wastewater treatment; Page no. 12, Line 1130: Table 1: Integrated Systems of microbial fuel cells (MFCs)with Various Techniques;  Page no. 16, Line 1377: Table 2: Several studies demonstrating the performance of sediment MFC; Latest Integration studies: Page no. 10, Line 1054-1072: In another study, microbial fuel cell was integrated with anaerobic forward osmosis membrane bioreactors for generation of biogas,……This study found that integrating an electrocatalytic-assisted MEC into AnOMBR is an excellent method for industrial-scale biofuel generation [50]; Page no. 11, Line 1073-1085: In another experiment, it was observed that, The benefits of organic elimination, bioenergy production, and high-quality water recovery…….the findings of the experiment revealed that water-flux-facilitated proton advection was more essential than NPC-flux-promoted countercurrent proton exchange in regulating the power production in an OsMFC [51]; Page no. 13, Line 1155-1166: An innovative integrated single-stage Dark Fermentation-Microbial fuel cells (MFCs) method was designed………integrated system was capable of achieving a maximum voltage of 459 mV (367 mW) and a maximum cell efficacy of 44% (fuel consumption of 1.5 ×105 mol/h) [57]; Page no. 13, Line 1167-1177: A hybrid approach of dark fermentation (DF) and microbial fuel cell (MFC), known as sDFMFC,………H₂ and energy from a variety of biomass feedstocks while maintaining the individual DF and MFC processes' efficiency [58]; Page no. 15, Line 1340-1350: Quaglio et al. present an effective way for improving power extraction using SMFCs by alternating the anodes……..The Anode Alternation can also be considered of as a step forward in the field of intermittent energy harvesting [65]; Page no. 15, Line 1351-1375: In another study, the power generation capability of mixed-culture algal biomass was investigated using a multi-anode sediment microbial fuel cell (SMFC)………These findings suggested that algal biomass might be employed as a suitable feedstock in SMFCs to enhance electricity output significantly [66]; Page no. 19, Line 1492-1501: Wen et al. investigated the extraction efficiency of sulfamethoxazole (SMX), tetracycline (TC),…….MFC-CWs with plant and circuit connections have the ability to treat SMX and TC-containing wastewater [78]; Page no. 19, Line 1502-1509: The study was conducted by Mittal et al. to design a unique earthen membrane-based two-chambered wetland cum microbial fuel cell (CW-MFC)……..azo dye absorption, with current density and power density output of 544.6 mA/m³ and 148.29 mW/m³, respectively [79]; Page no. 18, Line 1510-1527: The up-flow constructed wetland-MFC system with various fillers were designed for removal of Cr (VI)……..the extensive Cr(VI) stress, microbial diversity in the cathode was higher than in the anode, and Acetoanaerobium and Exiguobacterium were the leading genera in the anode and cathode, respectively [80]; Page no. 20, Line 1600-1631: During the anaerobic digestion of Taihu blue algae, biohydrogen employing migrating ammonia as a nitrogen supply……..As a result, performing ammonia mitigation, hydrogen production, and biogas upgrading all at the same time with BES appears to be an effective approach [90]; Page no. 20, Line 1636-1659: 2.9. Anaerobic-Anoxic-Oxic (AA/O) integrated with MFC An MFC was also combined into an anaerobic-anoxic-oxic (AO/O) system, resulting in a hybrid system…….Because no external energy was required, the system was declared sustainable and viable, and the treated effluent met the local discharge standard; Page no. 24, Line 1728-1737: LCA Studies: Overall, three tasks are done by osmotic MDC integrated system that are- removal of salts, treatment of wastewater and generation of electricity. Although lab scale systems showed as good as 90% desalination, removal of salts from natural water sources has shown less efficiency.…..lesser contribution to greenhouse gas emissions were found when compared to conventional desalination systems directing towards a hope for sustainable development of the integrated system).

Reviewer #2

Greetings, Editor thank you for providing me with the opportunity to review the article. I reviewed the article by Patwardhan et al. with title `` Microbial Fuel Cell united with other existing technologies for enhanced power generation and efficient wastewater treatment ``. The theme of the article is very interesting and promising in the field, but present article has some flaws which need to be address before publication. I am pleased to send you major level comments. The manuscript can be accepted for publication after modification. Please consider these comments/suggestions as listed below.

Comments:

R2Q1: The title seems good, but the abstract is totally weird. The first line seems weird. Please revised thoroughly the abstract, it does not communicate your idea in its existing form.

R2A1: The authors are grateful to the reviewer’s suggestions. The abstract has been modified in Line 27-44 as per your suggestion.

R2Q2: The MFC is Microbial fuel cell. Author used microbial fuel (MFC); it is wrong. Please revise your paper accordingly since same issue occurs on several spots in the paper.

R2A2: The term “microbial fuel (MFC)” has been replaced with “Microbial fuel cell (MFC)” in the revised manuscript.

R2Q3: The novelty of the work must be clearly addressed and discussed, compare and highlight novelty. What is novelty of this review?

R2A3: The novelty of various integrated MFCs (Page no. 2-3, Line 106-335: This paper discusses various categories of integrated MFCs system including integration with Capacitive Deionization Technology, forward osmosis technology, anaerobic digester, constructed wetland technology, microbial desalination cells, etc………..It also highlights disadvantages of stand-alone bio-electrochemical system and explains need for development of integrated MFC system. Further, future application of integrated MFC system on the industrial scale is elaborated.) incorporated in the revised manuscript.

R2Q4: Is it MFCs or MFC...?? Please stick to one abbreviation and be consistent with it in entire text.

R2A4: The term “MFC” is used in the revised manuscript.

R2Q5: Please define the term and next used abbreviation throughout the article. Please revise your paper accordingly since same issue occurs on several spots in the paper.

R2A5: The terms and abbreviations are explained throughout the article in the revised manuscript.

R2Q6: The main objective of the work must be written on the more clear and more concise way at the end of introduction section.

R2A6: The introduction has been modified (Page no. 2-3, Line 106-335: This paper discusses various categories of integrated MFCs system including integration with Capacitive Deionization Technology, forward osmosis technology, anaerobic digester, constructed wetland technology, microbial desalination cells, etc………..It also highlights disadvantages of stand-alone bio-electrochemical system and explains need for development of integrated MFC system. Further, future application of integrated MFC system on the industrial scale is elaborated; Page no. 3, Line 337-352: Organic compounds like acetate and glucose are oxidized anaerobically in MFC, resulting in the liberation……This oxidation and reduction creates the potential difference between the electrodes, results into generation of bio-electricity (Figure.1); Page no. 3-4, Line 354-488: Considering the significance of electrodes in MFCs, selecting the right electrode material is an important part of the system's design..…….One of the most limiting aspects of MFC operation is the steady reduction of oxygen on the interface of carbon or graphite electrodes, which results in a significant overpotential reduction. Hence, selecting appropriate cathode material is important.) in the revised manuscript.

R2Q7: Reference 1 is not relevant reference for this statement. Please cite these two references (i) Outlook on the role of microbial fuel cells in remediation of environmental pollutants with electricity generation (ii) Asim AY, Mohamad N, Khalid U, Tabassum P, Akil A, Lokhat D, Siti H. A glimpse into the microbial fuel cells for wastewater treatment with energy generation. Desalination and Water Treatment. 2021;214:379-89.

R2A7: The respective references have been cited (Page no. 2, Line 78-79: Microbial fuel cell (MFC) operate on the oxidation reaction at anode and reduction mechanism at cathode [1,2].) in the revised manuscript.

R2Q8: Introduction section must be written on more quality way, i.e., more up-to-date references addressed. Research gap should be delivered on more clear way with directed necessity for the future research work.

R2A8: The introduction has been modified (Page no. 2-3, Line 106-335: This paper discusses various categories of integrated MFCs system including integration with Capacitive Deionization Technology, forward osmosis technology, anaerobic digester, constructed wetland technology, microbial desalination cells, etc………..It also highlights disadvantages of stand-alone bio-electrochemical system and explains need for development of integrated MFC system. Further, future application of integrated MFC system on the industrial scale is elaborated; Page no. 3, Line 337-352: Organic compounds like acetate and glucose are oxidized anaerobically in MFC, resulting in the liberation……This oxidation and reduction creates the potential difference between the electrodes, results into generation of bio-electricity (Figure.1); Page no. 3-4, Line 354-488: Considering the significance of electrodes in MFCs, selecting the right electrode material is an important part of the system's design..…….One of the most limiting aspects of MFC operation is the steady reduction of oxygen on the interface of carbon or graphite electrodes, which results in a significant overpotential reduction. Hence, selecting appropriate cathode material is important.) in the revised manuscript.

R2Q9: Page 2, Line 62 need a reference. Please consider this ``Modern trend of anodes in microbial fuel cells (MFCs): an overview``. What is meaning of this sentence `` electrode fouling, outside of the lab``.

R2A9: The respective reference as suggested by reviewer has been cited and also, the respective sentence has been removed.

R2Q10: Author should provide the permission if they adapted these all figures. Please confirm and check.

R2A10: The authors confirm that all the figures are original.

R2Q11: Several abbreviations are not defined. Please check.

R2A11: All the abbreviations have been defined in the revised manuscript.

R2Q12: All heading/subheading should be in one style such as Integration of MFCs with Dark fermentation. Its wrong. It should be `` Integration of MFCs with Dark Fermentation``. Please check thoroughly.

R2A12: The term “Integration of MFCs with Dark fermentation” is replaced by `` Integration of MFCs with Dark Fermentation``. Other subheadings are also revised in the revised manuscript as per your suggestion.

R2Q13: Page 10, Line 371, the 49 percent. Its should be %. Please stick to one term (% or percent) and be consistent with it in entire text. Please revise your paper accordingly since same issue occurs on several spots in the paper.

R2A13: “percent” has been replaced by “%” in the revised manuscript.

R2Q14: Page 11, Line 409 need reference, please cite these references (i) Electricity generation and heavy metal remediation by utilizing yam (Dioscorea alata) waste in benthic microbial fuel cells (BMFCs) (ii) Application of rotten rice as a substrate for bacterial species to generate energy and the removal of toxic metals from wastewater through microbial fuel cells.

R2A14: The respective references have been citied (Page no. 15, Line 945: The contaminants in BMFC sediment aid as a source of energy for bacteria, and the oxidation of contaminants in the sediment and the decrease of oxygen at the surface produces power [71,72].) in the revised manuscript.

R2Q15: Reference 56 is not about BMFCs please replace by this reference; Cellulose derived graphene/polyaniline nanocomposite anode for energy generation and bioremediation of toxic metals via benthic microbial fuel cells.

R2A15: The respective references have been citied (Page no. 15, Line 1291-1292: As previously stated, constant monitoring of produced voltage and retention of power from BMFCs can also be used as monitoring system in the sea [73].) in the revised manuscript.

R2Q16: Zhang and He (2013) and Zhang and He (2015) reference citation style is wrong. It should be Zhang et al. (2013). Please follow the journal guidelines.

R2A16: The reference style has been corrected in the revised manuscript.

R2Q17: Please provide the space between number and units such as 34W/m³. Please revise your paper accordingly since same issue occurs on several spots in the paper.

R2A17: Space has been given in between the number and unit in the revised manuscript.

R2Q18: There are a lot of grammatical and language error such as Congo red? C should be in small letter. Please revise your paper accordingly since same issue occurs on several spots in the paper.

R2A18: The term Congo red has been replaced with “congo red”. We have rectified the mistake in the revised manuscript.

R2Q19: Commercialization and Practicality for this please consider and cite this article (Development and modification of materials to build cost-effective anodes for microbial fuel cells (MFCs): An overview) to write something advance.

R2A19: The respective references have been citied (Page no. 25, Line 1802-1805: Moreover, since integrated MFCs employ costly chemicals to enhance efficiency, investigations need to be carried out to find a cost-effective alternative such as using ozone as the final electron acceptor at large scale applications [112].) in the revised manuscript.

R2Q20: What about the electrode challenge which is the hottest talk in the field? Please look this article (Recent advances in anodes for microbial fuel cells: An overview) to add about electrode challenges specially anode.

R2A20: The authors have incorporated the electrode challenge and also cited the respective reference (Page no. 24, Line 1753: MFC frequently creates low operational voltage in relation to the cell's electromotive force, which is commonly referred to as thermodynamically anticipated irreversible potentials. Excess biofilm and the chemical molecules generated by the biofilm may aggravate anodic biofouling, thus further lowering the transfer of electrons from the microbe to the anodic material [112]) in the revised manuscript.

R2Q21: In table 2, please use one term Power generation or Power density. While Table 1 remove the term performance and specify the power density and removal efficiency.

R2Q22: Conclusion section is missing some perspective related to the future research work. Please improve this section carefully. I also did not understand your conclusion. What reader can get in conclusion?

R2A22: The conclusion has been modified in the revised manuscript.

R2Q23: English need major level revision through the manuscript. Several spot have grammatical errors.

R2A23: The English and grammar of the manuscript has been corrected.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors answered all my questions and doubts as well as corrected the manuscript. In this regard I suggest acceptance of presented revised version. 

Author Response

Response to reviewer's comments

Manuscript ID: applsci-1426339

Title: Microbial Fuel Cell united with other existing technologies for enhanced power generation and efficient wastewater treatment

The authors would like to appreciate all the reviewers and the editor for their valuable suggestions and comments involved in enhancing the standard of our manuscript.

Reviewer #1

Authors answered all my questions and doubts as well as corrected the manuscript. In this regard I suggest acceptance of presented revised version. 

Response: The authors are very grateful to the reviewer for the acceptance.

Author Response File: Author Response.pdf

Reviewer 2 Report

Greetings, Editor thank you for providing me with the opportunity to re-review the article I have reviewed again the manuscript by Patwardhan et al. with title `` Microbial Fuel Cell united with other existing technologies for  enhanced power generation and efficient wastewater treatment ``. The present form is acceptable for publication.

I suggest author to correct the citation style properly before publication. Such as

1. Ghadge and Ghangrekar (2015) constructed a 26L….[14]..It should be Ghadge and Ghangrekar [14]. Again, I request authors to follow any previous article of polymer to follow the style.
2. Zhao et al. [41] should like that. Please cite the number after et al. instead of end at the sentence. Please revise your paper accordingly since same issue occurs on other spots in the paper.

Overall, the quality and scientific contribution of the article is good, and I recommend the publication. 

Author Response

Response to reviewer's comments

Manuscript ID: applsci-1426339

Title: Microbial Fuel Cell united with other existing technologies for enhanced power generation and efficient wastewater treatment

The authors would like to appreciate all the reviewers and the editor for their valuable suggestions and comments involved in enhancing the standard of our manuscript.

Reviewer #2

Greetings, Editor thank you for providing me with the opportunity to re-review the article I have reviewed again the manuscript by Patwardhan et al. with title `` Microbial Fuel Cell united with other existing technologies for enhanced power generation and efficient wastewater treatment ``. The present form is acceptable for publication.

Comments:

R2Q1: I suggest author to correct the citation style properly before publication. Such as

1. Ghadge and Ghangrekar (2015) constructed a 26L….[14]..It should be Ghadge and Ghangrekar [14]. Again, I request authors to follow any previous article of polymer to follow the style.
2. Zhao et al. [41] should like that. Please cite the number after et al. instead of end at the sentence. Please revise your paper accordingly since same issue occurs on other spots in the paper.

Overall, the quality and scientific contribution of the article is good, and I recommend the publication. 

R2A1: The authors would like to appreciate all the reviewers and the editor for their valuable suggestions and comments involved in enhancing the standard of our manuscript. The Authors have modified the reference style as suggested by the reviewer.

Author Response File: Author Response.pdf