Over-Produced Extracellular Polymeric Substances and Activated Antioxidant Enzymes Attribute to Resistance of Pb(II) for Algal–Bacterial Granular Sludge in Municipal Wastewater Treatment

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study deciphered the influence of Pb(II) on the treatment efficiency of algal-bacterial granular sludge process and demonstrated the availability of algal-bacterial granular sludge process for municipal wastewater treatment. Overall, this article falls in the scope of this journal and adds new perspectives of engineering feasibility for algal-bacterial granular sludge process. However, the paper needs to be polished and clarified. I will recommend the manuscript publishable for Water after minor revisions. Some comments are listed as follows.

 

1.      2.2 Experimental design

The light cycle was 8 h of light and 16 h of dark. Why the sampling was carried out at 8 h should be described.

Extracellular polymeric substances (EPS) were extracted by a modified heat extraction method. A suitable reference should be given here.

2.      Figure 3: The expression of PN and PS should be consistent with other parts in the manuscript.

3.      Figure 7: What the symbols stand for?

4.      3.4 Performance in treating municipal wastewater. The variations of Pb(II) removal by algal-bacterial granular sludge across 90 days of operation were that neary all Pb(II) added was removed from the solution. How much Pb(II) has been specifically removed?

 

5.      The references should be in a same style.

Comments on the Quality of English Language

Fine.

Author Response

Reply to Reviewer #1 Comments

 

This study deciphered the influence of Pb(II) on the treatment efficiency of algal-bacterial granular sludge process and demonstrated the availability of algal-bacterial granular sludge process for municipal wastewater treatment. Overall, this article falls in the scope of this journal and adds new perspectives of engineering feasibility for algal-bacterial granular sludge process. However, the paper needs to be polished and clarified. I will recommend the manuscript publishable for Water after minor revisions. Some comments are listed as follows.

Thank you very much for your kind comments on the manuscript water-2684052, according to which the manuscript has been carefully revised.

 

 

Q1. 2.2 Experimental design

The light cycle was 8 h of light and 16 h of dark. Why the sampling was carried out at 8 h should be described.

A1. Added as suggested, please refer to Section 2.2.

 

Q2. Extracellular polymeric substances (EPS) were extracted by a modified heat extraction method. A suitable reference should be given here.

Q2. Reference 29 was added here.

 

Q3. Figure 3: The expression of PN and PS should be consistent with other parts in the manuscript.

A3. Revised as suggested, please refer to Figure 3.

 

Q4. Figure 7: What the symbols stand for?

A4. The meanings represented by these symbols have been explained, please refer to Figure 7.

 

Q5. 3.4 Performance in treating municipal wastewater. The variations of Pb(II) removal by algal-bacterial granular sludge across 90 days of operation were that neary all Pb(II) added was removed from the solution. How much Pb(II) has been specifically removed?

A5. Pb(II) removal efficiencies were added as suggested, please refer to Section 3.4.

 

Q6. The references should be in a same style.

A6. The references have been carefully checked to ensure they are in the same style.

Reviewer 2 Report

Comments and Suggestions for Authors The authors set the stage to investigate the impact of coexisting Pb(II) on the symbiosis of algal-bacterial granular sludge. The results revealed that 2.5-10.0 mg/L of Pb(II)-exposed increased the relative abundance of Pro-teobacteria. More protein in extracellular polymeric substances (EPS-PN) was secreted at 2.5 mg/L of Pb(II)-exposed, while EPS-PN content reduced at 5.0-10.0 mg/L of Pb(II). The activities of SOD and CAT enzymes in cells showed an upward trend to eliminate ROS produced in cells. In addition, the performance of algal-bacterial granular sludge in treating COD, ammonia-N and phosphate-P kept at above 95%. This study is interesting and can provide useful information to improve algal-bacterial granular sludge process.   1) In Introduction, the authors should analyze the limited information regarding the effect of Pd(II)-exposed on the removal efficiency of nutrients (page 95). Justify it also with references.

Author Response

Reply to Reviewer #2 Comments

 

The authors set the stage to investigate the impact of coexisting Pb(II) on the symbiosis of algal-bacterial granular sludge. The results revealed that 2.5-10.0 mg/L of Pb(II)-exposed increased the relative abundance of Pro-teobacteria. More protein in extracellular polymeric substances (EPS-PN) was secreted at 2.5 mg/L of Pb(II)-exposed, while EPS-PN content reduced at 5.0-10.0 mg/L of Pb(II). The activities of SOD and CAT enzymes in cells showed an upward trend to eliminate ROS produced in cells. In addition, the performance of algal-bacterial granular sludge in treating COD, ammonia-N and phosphate-P kept at above 95%. This study is interesting and can provide useful information to improve algal-bacterial granular sludge process.

Thank you very much for your encourage comments on this manuscript, according to which the manuscript has been carefully revised. The point-to-point reply is arranged below for your kind consideration.

 

Q1. In Introduction, the authors should analyze the limited information regarding the effect of Pd(II)-exposed on the removal efficiency of nutrients (page 95). Justify it also with references.

A1. Added as suggested, please refer to Section 1.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

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