Utilizing Electricity-Producing Bacteria Flora to Mitigate Hydrogen Sulfide Generation in Sewers through an Electron-Pathway Enabled Conductive Concrete

Round 1

Reviewer 1 Report

The authors present a study focused up on the  the effectiveness of using biological oxidation for hydrogen sulfide (H2S) control. A long-term experiment was conducted using a rod-shaped electrode made of highly conductive concrete, which provided an electron pathway for H2S mitigation. This article is well worthy of publication because the study is a carefully done and the findings are of considerable interesting. But the paper needs significant improvement before acceptance for publication. My detailed comments are as follows:
1. Introduction needs a detailed review of previous work, for example, where are the characteristics and advantages of the materials in this paper?

2. TEM can better study the surface structure and composition. It is suggested to add TEM characterization test of the conductive substance (amorphous carbon) of the electrode. The author can refer to these papers, Chem. Eng. J. 409, 2021, 128185； Advanced Fiber Materials, 2023, DOI: 10.1007/s42765-022-00253-5.

3. The paper needs to avoid some small mistakes, for example, the format of references needs to be unified.

Author Response

Reviewer 1:

The authors present a study focused up on the  the effectiveness of using biological oxidation for hydrogen sulfide (H2S) control. A long-term experiment was conducted using a rod-shaped electrode made of highly conductive concrete, which provided an electron pathway for H2S mitigation. This article is well worthy of publication because the study is a carefully done and the findings are of considerable interesting. But the paper needs significant improvement before acceptance for publication. My detailed comments are as follows:
Question 1: Introduction needs a detailed review of previous work, for example, where are the characteristics and advantages of the materials in this paper?

Response 1:

Thank you very much for your recommendations. In this revised manuscript, we added some information to response for your concerns at Line 84-90 in resubmission manuscript.

Question 2: TEM can better study the surface structure and composition. It is suggested to add TEM characterization test of the conductive substance (amorphous carbon) of the electrode. The author can refer to these papers, Chem. Eng. J. 409, 2021, 128185； Advanced Fiber Materials, 2023, DOI: 10.1007/s42765-022-00253-5.

Response 2

Thank you very much for your question. Your comments are very interesting and provided a useful reference. In this revised manuscript, we conducted SEM characterization test of amorphous carbon in San earth as conductive concrete and would like to keep unchanged information in resubmission manuscript.  We are considering conducting the TEM test in further research.

 Question 3: The paper needs to avoid some small mistakes, for example, the format of references needs to be unified.

Response 3

Thank you very much for your constructive comments. In this time, we checked and revised thoroughly all manuscript in the resubmission manuscript. All are showed in changes marked.

Reviewer 2 Report

Manuscript can be accepted.

Author Response

Reviewer 2: 

Question 1: Manuscript can be accepted.

Response 1: Thank you very much for your constructive comment.  In this time, we checked manuscript again and revised thoroughly all manuscript in the resubmission manuscript. All are showed in changes marked.

Reviewer 3 Report

This manuscript describes “Utilizing electricity producing bacteria flora to mitigate hydrogen sulfide generation in sewers through an electron pathway enabled conductive concrete”. Please see the following comments.

 

Figure 1 describes the concrete sewer. How does concrete sewer have conductive material?

 

Line 93 to line 100: In introduction, this study was already done. It should be past tense.

 

The title of result 3.1 should be modified as “Inhibition of hydrogen sulfide generation using conductive concrete.

 

What is the difference between open circuit and closed circuit? Is there any difference on mitigating hydrogen sulfide generation in sewer?

 

Table 1 should be in the section of “Materials and methods”.

 

The manuscript title says “utilizing electricity producing bacteria to reduce hydrogen sulfide generation”. However, there is no mention how to use those bacteria to mitigate hydrogen sulfide production. Add the role of EPB and how to use in sewers.

 

 

 

 

 

 

 

Minor:

1.    In introduction, authors mentioned “EPB”. Give a full name of EPB.

Author Response

Reviewer 3:

This manuscript describes “Utilizing electricity producing bacteria flora to mitigate hydrogen sulfide generation in sewers through an electron pathway enabled conductive concrete”. Please see the following comments.

Question 1:  Figure 1 describes the concrete sewer. How does concrete sewer have conductive material?

Response 1:

Thank you very much for your interesting comments.  Although concrete is not inherently conductive, it is possible to incorporate conductive materials into the concrete mix. In the case of sewer systems, the purpose of using conductive concrete is to prevent the formation of hydrogen sulfide gas, which can corrode the concrete and create a safety hazard. Conductive materials such as amorphous carbon, San earth can be added to the concrete mix to make it conductive. Another option is to use commercially available conductive concrete. This allows for the creation of a more durable and effective sewer system

Question 2:  Line 93 to line 100: In introduction, this study was already done. It should be past tense.

Response 2

Thank you very much for your constructive comments. I revised them in resubmission manuscript.

Question 3:  The title of result 3.1 should be modified as “Inhibition of hydrogen sulfide generation using conductive concrete.

Response 3

Thank you very much for your constructive comments. I revised them in resubmission manuscript at Line 238-239 in the resubmission manuscript.

Question 4:  What is the difference between open circuit and closed circuit? Is there any difference on mitigating hydrogen sulfide generation in sewer?

Response 4:

Thank you very much for your interesting comments. The main difference between an open circuit and a closed circuit is that in an open circuit, there is no complete path for electric current to flow, while in a closed circuit, there is a complete path for electric current to flow. Regarding the mitigation of hydrogen sulfide generation in sewer, we conducted an experiment using conductive concrete in two different setups. In the first setup, which was an open circuit, the electron pathway could not be activated effectively even though conductive concrete was used. As a result, the biological oxidation of H2S was less effective. In contrast, in the second setup, which was a closed circuit, the electron pathway was activated easily, and the biological oxidation in the surface electrode was enhanced. This resulted in a higher effectiveness of mitigating hydrogen sulfide generation in the sewer when conductive concrete was set up as a closed circuit.

Question 5:  Table 1 should be in the section of “Materials and methods”.

Response 5:

Thank you very much for your constructive comments. I arranged Table 1 to section of “Materials and Methods” and revised them in resubmission manuscript from Line 187  in the resubmission manuscript.

Question 6:  The manuscript title says “utilizing electricity producing bacteria to reduce hydrogen sulfide generation”. However, there is no mention how to use those bacteria to mitigate hydrogen sulfide production. Add the role of EPB and how to use in sewers.

Response 6:

Thank you very much for your comments.   There are several types of bacteria that can generate electricity from effluent wastewater. Some examples of such bacteria include Geobacter, Shewanella, and Anaeromyxobacter, which have been found available in various wastewater treatment systems, including anaerobic digesters and sediments. For instance, in a study by Zhang et al. (2011), microbial communities present in a pilot-scale sewer system were analysed, and several types of EPB were identified, including Desulfobulbus and Geobacter species. (https://doi.org/10.1016/j.biortech.2010.09.044).  Conductive concrete, when applied to sewer systems, activates electrochemical processes that enhance the performance of electroactive bacteria (EPB). As a result, we have been using the term "utilizing EPB" to emphasize the effectiveness of conductive concrete in enhancing EPB activity. However, we are currently considering renaming this term.

Question 7: Minor: 1.    In introduction, authors mentioned “EPB”. Give a full name of EPB.

Response 7:

Thank you very much for your constructive comment. I revised them in resubmission manuscript from Line 87 in the resubmission manuscript.

Round 2

Reviewer 3 Report

No changes are present in the revised version of manuscript.