The Treatment of Antibiotic Excess Sludge via Catalytic Wet Oxidation with Cu-Ce/γ-Al₂O₃ and the Production of a Carbon Source

Round 1

Reviewer 1 Report

Reviewer's comments on a study titled "water-2921850" authored by Chu, S.; Lin, H.; Zeng, X.

The study aims to find an efficient method for removing antibiotics from aquatic environments. The authors have used Cu-Ce/gamma-Al2O3 to catalytically oxidize antibiotic excess sludge to produce low-molecular carboxylic acid compounds, which can be used as carbon sources by microorganisms. However, the reviewer has raised some concerns and suggested some improvements.

Firstly, the authors have not described the types and concentration of antibiotics present in the sludge, which is a crucial substance for this study. Also, the reviewer has requested the authors to provide more information about the catalysis used in this study. The authors should add control experiment data to clear the effect of the catalysis. For instance, the data for catalysis dosage at 0 g/L should be added to Fig. 3.

The reviewer has also made some minor comments. They have suggested changing the unit for a specific surface area (m2) to m2/g (line 152). In Fig. 3, the experimental conditions such as operation temp, reaction time, and oxygen pressure should be specified (line 160). The reviewer has requested adding data for the absence of catalysis in Fig. 4 (lines 175-180) and lines 208-214. The authors should add analytical methods for VFAs in Table 2 (line 256-257) or cite related references. Finally, the reviewer has asked whether the authors checked whether any antibiotics remained in the influent and effluent (line 286, Fig.7).

English editing should be required. 

Author Response

Please see the attached file. Thanks!

Author Response File: Author Response.pdf

Reviewer 2 Report

The article describes the effectiveness of catalytic wet oxidation caused by the use of Cu-Ce/γ-Al2O3 for the decomposition of excess sludge containing antibiotics. The work concerns the important and current problem of polluting the aquatic environment with persistent compounds such as antibiotics. The work is interesting, provides positive results, and is in line with trends in water and sewage management, however, for the work to be published, the authors must make the necessary corrections. The reviewer sends his comments:

·        Line 34 replace „dispose antibiotic-containing” with dispose of antibiotic-containing

·        Line 44 replace „property” with properties

·        Introduction: The authors should supplement the introduction with the following information: 1) due to the increase in the production and consumption of drugs, an increasing concentration of pharmaceutical compounds is released into the sewage, the presence of which is not monitored. 2) As the authors pointed out, sewage treatment plants do not completely remove pharmaceutical compounds from wastewater due to microbial resistance and ineffective methods. Most of the pollution load accumulates in sludge, hence the authors are developing alternative methods of purifying sewage sludge from pharmaceutical compounds. 3) write the advantages and disadvantages of other methods of utilization and purification of pharmaceutical compounds from sediments. 4) describe briefly the research of other scientists on Catalytic wet oxidation technology.  Completing this information will show greater importance of the research conducted.

·        2.3. Catalytic wet oxidation experiments: Did the authors prepare the antibiotic-sediment mixture themselves or was it a real sample? What percentage of precipitate was there in the antibiotic-sediment mixture? What antibiotics and in what concentration were in the antibiotic-sludge mixture? Were there only antibiotics in the sediment or could there also be other organic compounds?

·        2.3. Catalytic wet oxidation experiments: „COD and VSS analysis with standard method.” Please write details of analytical methods.

·        Please improve the quality of figure 2b

·        3.4. Production of carboxylic acids :What methods were VFAs determined by?

·        Results - no discussion of the results with the literature and results of other authors

·        The authors write that the promoted solution is economically beneficial. Could the authors do a simplified cost-effectiveness that would show the cost of installation, energy consumption, etc., and comparing to the costs of other methods?

·        In future studies, it is recommended that the authors check the effectiveness of antibiotic removal using more advanced methods, e.g. chromatography. Based on the results, it is known that the technology works and requires further research, but it is not known what the degree of removal of individual antibiotics is.

Comments for author File: Comments.pdf

Author Response

Please see the attached file. Thanks!

Author Response File: Author Response.pdf

Reviewer 3 Report

Kindly find the attached comments.

Comments for author File: Comments.pdf

Author Response

Please see the attached file. Thanks!

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have carefully revised the original manuscript based on the comments. The revised manuscript can be acceptable for publication in Water. 

Author Response

Thank you very much for your kind review letter and comments. 
Thanks again!

Reviewer 2 Report

The authors made changes and corrections according to the reviewer's suggestions. The authors put a lot of work and effort into creating the manuscript. The work in its current form is suitable for publication.

Author Response

Thank you very much for your kind review letter and comments. 
Thanks again!