Study on the Decontamination Effect of Biochar-Constructed Wetland under Different Hydraulic Conditions
Round 1
Reviewer 1 Report
-Although, it is possible to optimize the efficiency of the decontamination with an univariate study, and it can be useful in a preliminary study, it does not provide enough information. The work could be improved using any multivariable methods, such as a simplex method, experimental design or ANOVA.
-Removal efficiency: Is it really necessary to use so many decimal numbers? I my opinion so much accuracy is not possible. It is more appropriate to indicate the value of the standard deviation for each averaged.
- Figures 3-10 should include the error bars
- In Table 2: The authors should clarify the meaning of NH3-N (Ammonia nitrogen), TN (Total nitrogen), TP(Total phosphorus), COD (Chemical oxygen demand)
- In the discussion section, the authors should increase the comparison between their results and other data reported in literature.
Author Response
Response to Reviewer 1 Comments
Point 1: Although, it is possible to optimize the efficiency of the decontamination with an univariate study, and it can be useful in a preliminary study, it does not provide enough information. The work could be improved using any multivariable methods, such as a simplex method, experimental design or ANOVA.
Response 1: Thank you very much for your suggestion, the method of ANOVA has been used in the modification process. Lines 189-191; line 218; line 242; line 269; line 297; line 320; line 342; line 364.
Point 2: Removal efficiency: Is it really necessary to use so many decimal numbers? I my opinion so much accuracy is not possible. It is more appropriate to indicate the value of the standard deviation for each averaged.
Response 2: The representation of numbers has been modified. The value of the standard deviation for each averaged has been added in the manuscript to denote numbers.
Line 16; line 23; lines 178-184; lines 206-216; lines 229-233; lines 249-266; lines 282-285; lines 308-309; line 332; line 358
Point 3: Figures 3-10 should include the error bars.
Response 3: The error bars have been added to the graphs. Line 192; line 221; line 244; line 272; line 330; line 322; line 344; line 366.
Point 4: In Table 2: The authors should clarify the meaning of NH3-N (Ammonia nitrogen), TN (Total nitrogen), TP(Total phosphorus), COD (Chemical oxygen demand).
Response 4: The meaning of NH3-N (Ammonia nitrogen), TN (Total nitrogen), TP(Total phosphorus), COD (Chemical oxygen demand) has been added in the article. Lines 133-142
Point 5: In the discussion section, the authors should increase the comparison between their results and other data reported in literature.
Response 5: The comparison between their results and other data reported in literature has been added in the article. Lines 179-180; lines 211-212; lines 230-231; line 256; lines 284-285; lines 309-310; lines 331-333; lines 357-358.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript "Study on the decontamination effect of biochar constructed wetland under different hydraulic conditions" has several major weaknesses, therefore I recommend major revisions.
Some specific comments are detailed as follows.
The manuscript should be revised by an English native speaker to improve the language (i.e. several words are repeated too many times; some words are wrongly used - e.g. "decontamination" and "purification" instead of "treatment"; sentences are often too long, etc.).
lines 11-22: please add quantitative data, too vague.
lines 42-55: please provide quantitative details about biochar physics-chemical characteristics and performances in pollutants' removal when used as additive in constructed wetlands.
the literature survey should be heavily improved, 17 references are not enough. the Authors should describe synthetically the performances of constructed wetlands in wastewater treatment in rural areas, what are the main bottlenecks and why they think that biochar could improve their performances. there is much literature available on the topic. moreover, the role of biochar as adsorbent for the considered pollutants (nutrients and COD) has been extensively explored, and the Authors didn't mention it.
lines 57: the main weakness of the manuscript is that the physico-chemical properties of the biochar materials involved in the tests were not accounted at all. I agree that HRT and hydraulic load are significant factors to be explored (and I appreciated how the Authors design and performed the tests). Actually, the main findings of the manuscript were that biochar substantially improved the performances of the constructed wetlands in the considered experimental conditions. However, not all biochars are equal. Biochar's physico-chemical features (i.e. C, H, O, ash contents, specific surface area, pore size and volume, pH, alkaline metals contents, etc) depend on the biomass from which the biochar is derived, from the pyrolysis (or other thermochemical process) process' conditions and plant design, from the biochar activation process. these are key issues and they could not be ignored. Therefore, I kindly invite the Authors to improve this part of the research characterising the employed biochar materials (just mentioning "coconut shell and nutshell biochars" at line 77 is not enough), to find more support to the main findings of the research.
line 58: the novelty statement of the manuscript should be improved and the objectives clearly described.
Author Response
Point 1: The manuscript should be revised by an English native speaker to improve the language (i.e. several words are repeated too many times; some words are wrongly used - e.g. "decontamination" and "purification" instead of "treatment"; sentences are often too long, etc.).
Response 1: Thank you very much for your suggestion, I have submitted the manuscript to MDPI's English editing service to revise my article. Some wrong words were also corrected.
Point 2: Lines 11-22: please add quantitative data, too vague..
Response 2: The quantitative data has been added in the manuscript. Lines 14-16; lines 21-23.
Point 3: Lines 42-55: please provide quantitative details about biochar physics-chemical characteristics and performances in pollutants' removal when used as additive in constructed wetlands.
Response 3: The quantitative details about biochar physics-chemical characteristics and performances have been added in the manuscript. Lines 66-87.
Point 4: The literature survey should be heavily improved, 17 references are not enough. the Authors should describe synthetically the performances of constructed wetlands in wastewater treatment in rural areas, what are the main bottlenecks and why they think that biochar could improve their performances. there is much literature available on the topic. moreover, the role of biochar as adsorbent for the considered pollutants (nutrients and COD) has been extensively explored, and the Authors didn't mention it.
Response 4: The relevant literature about the performances of constructed wetlands in wastewater treatment in rural areas has been added in the manuscript, and explained the main bottlenecks as well as why they think that biochar could improve their performances. Lines 36-46.
Point 5: Lines 57: the main weakness of the manuscript is that the physico-chemical properties of the biochar materials involved in the tests were not accounted at all. I agree that HRT and hydraulic load are significant factors to be explored (and I appreciated how the Authors design and performed the tests). Actually, the main findings of the manuscript were that biochar substantially improved the performances of the constructed wetlands in the considered experimental conditions. However, not all biochars are equal. Biochar's physico-chemical features (i.e. C, H, O, ash contents, specific surface area, pore size and volume, pH, alkaline metals contents, etc) depend on the biomass from which the biochar is derived, from the pyrolysis (or other thermochemical process) process' conditions and plant design, from the biochar activation process. these are key issues and they could not be ignored. Therefore, I kindly invite the Authors to improve this part of the research characterising the employed biochar materials (just mentioning "coconut shell and nutshell biochars" at line 77 is not enough), to find more support to the main findings of the research.
Response 5: The physico-chemical properties of the biochar materials have been introduced briefly in the modification. Lines 55-63.
Point 6: Line 58: the novelty statement of the manuscript should be improved and the objectives clearly described.
Response 6: This section has also been revised. In the revision, the research purpose of the manuscript is re-stated. Lines 91-94.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The Authors applied all the recommendations and the manuscript was significantly improved. Good job!
