Integrated Anaerobic–Aerobic Moving Bed Biofilm Reactor and Biochar Adsorption for the Efficient Removal of Organic Matter and Nutrients from Brazilian Landfill Leachate

Round 1

Reviewer 1 Report

The manuscript titled: Integrated anaerobic-aerobic MBBR and biochar adsorption for efficient removal of organic matter and nutrients from Brazilian landfill leachate.

1. In the keywords. Please, add the full name of MBBR.

2.  Line 64 page 2. The word “pound” is fault. It is “compound”.

3. Please, add the number of low OM, ammonium-nitrogen and TP in the previous study like you made for COD and BOD.

4. What is meaning of HRT in line 145 page 3. Add the full name in the first mention (hydraulic retention times), please.

5. Please, refer to “the non-linearity” for the equations 1, 2 and 3.

6. Where is the reference for equations?

7. Where is the equation for removal efficiency (i.e. COD, BOD, etc.)? You can use the following reference or other and add it.

You can use that reference or other for help. You are free.

Tohamy, H. A. S., El-Sakhawy, M., & Kamel, S. (2023). Microwave-assisted synthesis of amphoteric fluorescence carbon quantum dots and their chromium adsorption from aqueous solution. Scientific Reports, 13(1), 11306.‏

8. The same question. Where is the equation used for calculating ammonium-nitrogen and TP?

9. Where s the reference for this paragraph which prove your words “The main process which contributes to ammonium removal was the aerobic MBBR because the main mechanism for the elimination is the aerobic nitrification”

10. Please, revise line 354.

Faggiano, A.; Ricciardi, M.; Motta, O.; Fiorentino, A.; Proto, A.  Greywater Treatment for Reuse: Effect of Combined Foam Fractionation and Persulfate-Iron Based Fenton Process in the Bacterial Removal and Degradation of Organic Matter and Surfactants. Journal of Cleaner Production

11. In line 358 “The majority of contaminants are adsorbed within the first 30 minutes”. Please, add the percentage of removal of different factors like BOD, COD, etc. within the first 30 min.

12. The ssame question. Add the perecentage for the steady state in line 362, please.

 

13. What I meaning when the kinetic is fit with pseudo first order?  It mean there is a bond type between adsorbent and contaminant. What is the type? Please, read the suggested reference for answer or give me answer from other source that’s OK.

14.  Are you sure that R² is the same for COD, Ammonium “0.98 and 0.95”. It is un logic. Please, revise.

15. Where is the kinetic for BOD?  Please, add.

 16. You didn’t talk in details about the results from Elovich. Please, talk.

17. Please, add graphs for removal efficiency or different factors (COD, BOD, etc.).

18. Please, add table about landfill leachate characterization, composition and pH.

19. You made your study on aged 7 years. Please, add a comparable study about young landfill (i.e. fresh not aged).

20. Please, give the ratio between COD to BOD and ammonium to COD. 

GOOD LUCK

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript was well-written and designed, and the authors got interesting results. However, the work needs some enhancements before it can be published. I recommend a minor revision of the manuscript based on the following comments:

Comment 1: The abstract section should include the motivation, methods, and major findings of the paper.

Comment 2: Please provide in the material and methods section the methods for the characterization of the porous materials.

Comment 3: The conclusion section should be improved by mentioning highlights and the best findings.

Comment 4: It is recommended to add some suggestions for future works in this area to improve the conclusion.

Comment 5: The "Introduction" section should be impressive and informative. Some relative papers are highly recommended to improve this section:

·         Amari A, Ali MH, Jaber MM, Spalevic V, Novicevic R. Study of Membranes with Nanotubes to Enhance Osmosis Desalination Efficiency by Using Machine Learning towards Sustainable Water Management. Membranes. 2022 Dec 26;13(1):31.

·         Liu, H., et al.: Head-related transfer function–reserved time-frequency masking for robust binaural sound source localization. CAAI Trans. Intell. Technol. 7( 1), 26– 33 (2022). https://doi.org/10.1049/cit2.12010

·         El Jery A, Aldrdery M, Shirode UR, Gavilán JC, Elkhaleefa A, Sillanpää M, Sammen SS, Tizkam HH. An Efficient Investigation and Machine Learning-Based Prediction of Decolorization of Wastewater by Using Zeolite Catalyst in Electro-Fenton Reaction. Catalysts. 2023 Jul 10;13(7):1085.

·         Choudhuri, S., Venkateswara, H., Sen, A.: Coupling adversarial learning with selective voting strategy for distribution alignment in partial domain adaptation. Journal of Computational and Cognitive Engineering.1(4), 181–186 (2022).https://doi.org/10.47852/bonviewJCCE2202324

·         Zhang, Z., De Luca, G., Archambault, B., Chavez, J., & Rice, B. (2022). Traffic Dataset and Dynamic Routing Algorithm in Traffic Simulation. Journal of Artificial Intelligence and Technology, 2(3), 111-122.

·         Jery AE, Noreen A, Isam M, Arias-Gonzáles JL, Younas T, Al-Ansari N, Sammen SS. A novel experimental and machine learning model to remove COD in a batch reactor equipped with microalgae. Applied Water Science. 2023 Jul;13(7):153.

Comment 6: Authors should characterise the adsorbent materials after adsorption to provide more information about the adsorption mechanisms involved to remove heavy metals. In addition, isotherms and kinetics should be also investigated to determine the type of adsorption.

 

Comment 7: Please cite sources for Equations 1-3.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments on sustainability-2561061

Dear Sir/Madam,

The manuscript “Integrated anaerobic-aerobic MBBR and biochar adsorption for efficient removal of organic matter and nutrients from Brazilian landfill leachate” is well written. Although the authors have tried to collect various techniques and models to elaborate the study but it’s in random order and no scientific planning of the work is performed. Therefore, it is not suitable to represent the study for publication. (Major).

Comment 1: Check the whole manuscript for typing errors and check for grammatical mistakes throughout the text.

Comment 2: Abstract: The abstract only contains some parameters with process conditions or key values from results, which is insufficient to delineate the whole picture of the contribution and possible application of this study. It is suggested to add some background with a few objectives, key values from the results, and possible applications of this study and highlight the novelty of this work clearly.

Comment 3: Abstract: Line 23-25; “The performance of this integrated system was evaluated under different operating conditions, such as hydraulic retention time, organic loading rate, and biochar dosage, to optimize its efficiency and sustainability”. The authors have discussed the parameters in abstract only but their respective effects are not explained and no graphical presentation is observed in the manuscript. This is a major concern that how the results have been evaluated and concluded.

Comment 4: There are various other methods for leachate removal (i.e., freeze drying etc.), why the authors have selected only biological methods for the study. The authors need to explain this selection in light of literature in order to prove their particular selection. Add more information to rearrange the Introduction's last paragraph as; present a summary of the above literature review, research gaps should be highlighted in comparison with the literature review. Explain, how this study is different from others? The novelty of this study should be mentioned here.

Comment 5: Table 1 needs to be compared with literature.

Comment 6: From Table 2 and Figures 5, 6 and 7 it seems that the Pseudo first order (PFO) best fits the phenomenon with R²=0.98. It is also observed that Pseudo second order (PSO) also has a good fit with R²= 0.95. Is it possible that a phenomenon which is following PFO will also follow PSO??? In addition, the authors have not explained the phenomenon based on PFO and PSO and Elovich models. It seems that it’s just a collection of models and their presentation but no specific phenomenon is explained on the bases of mass transfer kinetics. Following studies may be helpful; Industrial Crops and Products, 2018:(116): 122-136, Bioresource Technology, 2019; (289): 121689.

 

 

Comment 7: Revise all Tables, see some high-impact published papers to organize information.

Comment 8: Authors have tried to study adsorption, using standard models but the screening experiments were not performed to proceed with the study. It seems that authors have copied the models and applied them without any further verifications.

Comment 9: The conclusions only talk about some studied parameters, which is insufficient to depict the whole picture of the contribution of this study. The authors are advised to write the conclusions comprehensively and should contain key values, suitability of the applied method, the major findings, contributions and possible future outcomes (250-300 words).

 

 

Thank You

Comments on sustainability-2561061

Dear Sir/Madam,

The manuscript “Integrated anaerobic-aerobic MBBR and biochar adsorption for efficient removal of organic matter and nutrients from Brazilian landfill leachate” is well written. Although the authors have tried to collect various techniques and models to elaborate the study but it’s in random order and no scientific planning of the work is performed. Therefore, it is not suitable to represent the study for publication. (Major).

Comment 1: Check the whole manuscript for typing errors and check for grammatical mistakes throughout the text.

Comment 2: Abstract: The abstract only contains some parameters with process conditions or key values from results, which is insufficient to delineate the whole picture of the contribution and possible application of this study. It is suggested to add some background with a few objectives, key values from the results, and possible applications of this study and highlight the novelty of this work clearly.

Comment 3: Abstract: Line 23-25; “The performance of this integrated system was evaluated under different operating conditions, such as hydraulic retention time, organic loading rate, and biochar dosage, to optimize its efficiency and sustainability”. The authors have discussed the parameters in abstract only but their respective effects are not explained and no graphical presentation is observed in the manuscript. This is a major concern that how the results have been evaluated and concluded.

Comment 4: There are various other methods for leachate removal (i.e., freeze drying etc.), why the authors have selected only biological methods for the study. The authors need to explain this selection in light of literature in order to prove their particular selection. Add more information to rearrange the Introduction's last paragraph as; present a summary of the above literature review, research gaps should be highlighted in comparison with the literature review. Explain, how this study is different from others? The novelty of this study should be mentioned here.

Comment 5: Table 1 needs to be compared with literature.

Comment 6: From Table 2 and Figures 5, 6 and 7 it seems that the Pseudo first order (PFO) best fits the phenomenon with R²=0.98. It is also observed that Pseudo second order (PSO) also has a good fit with R²= 0.95. Is it possible that a phenomenon which is following PFO will also follow PSO??? In addition, the authors have not explained the phenomenon based on PFO and PSO and Elovich models. It seems that it’s just a collection of models and their presentation but no specific phenomenon is explained on the bases of mass transfer kinetics. Following studies may be helpful; Industrial Crops and Products, 2018:(116): 122-136, Bioresource Technology, 2019; (289): 121689.

 

 

Comment 7: Revise all Tables, see some high-impact published papers to organize information.

Comment 8: Authors have tried to study adsorption, using standard models but the screening experiments were not performed to proceed with the study. It seems that authors have copied the models and applied them without any further verifications.

Comment 9: The conclusions only talk about some studied parameters, which is insufficient to depict the whole picture of the contribution of this study. The authors are advised to write the conclusions comprehensively and should contain key values, suitability of the applied method, the major findings, contributions and possible future outcomes (250-300 words).

 

 

Thank You

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 4 Report

Authors have carried out an experimental study to check the feasibility of an innovative system for landfill leachate treatment consisted on anaerobic-aerobic bioreactors followed by biochar adsorption to improve removal efficiencies. First of all, I would like to congratulate the authors for their work and encourage them to keep on working on this research line as it is a very useful contribution for the scientific community. I also would like to say that the manuscript is obviously the result of a hard work carried out by the authors and following, I am providing some comments and suggestions in order to help the authors to improve the quality of the manuscript prior to be published:

1.     Please, revise your English language. Some small mistakes can be found in the text.

2.     In my opinion, Introduction section need to be modified, the connection between different parts of the text could be improved. Please, revise this section and avoid also the repetition of very similar sentences.

3.     I strongly suggest to review and homogenize the use of acronyms, for example, in page 61, the first time that the concept “moving bed bioreactor” appears in the text, the acronym should be indicated in brackets (MBBR) and after that, use the acronym every time that it appears in the manuscript. Other examples such as COD or BOD5 have not been defined the first time they appears (line 60) but later (line 72). Also HRT has been defined in line 149 even though hydraulic retention time was mentioned in the text several times before this line.

4.     Instead of using the range in table 1, I think it would be more appropriate to indicate the average values including the standard deviations for each parameter. This suggestion is also valid for the text. Average values should include standard deviations.

5.     In section 2.1., references describing the methodology used for measuring parameters such as orthophosphate, NH4-N or suspended solids need to be included.

6.     Please, add also the references used to obtain the used equations describing the kinetic empirical models (lines 211-212).

7.     Also regarding the Materials and Methods section, a question raised for me when I was reading section 2. As described in this section, LL samples were monthly taken during 1 year period and kept at 4ºC. Later, the pilot plant was described, indicating that the experiment lasted 90 days. Influent LL was a punctual sample or a mixed one? Could you please indicate the methodology used for the generation of the influent LL and the time spent by the samples in the refrigerator at 4ºC prior to be mixed?

8.     There is something that in my opinion requires a higher discussion. Figure 2 shows the influent and effluent COD concentrations during the whole experiment. According to these results, even though the influent concentration arises almost 5 times the initial value (from 1226 to 4700 mg/L) and lowering the anaerobic HRT from 4 to 2 days, effluent COD maintained constant and even lower than the resulting COD obtained during phase I. These results need to be justified. However, in paragraph 3.1. there is neither references nor a deep discussion about biomass acclimation or any other justification. Moreover, there is no discussion about the effect of HRT and it would be important to remark this influence.

9.     In line 288, the figure related to NH4-N removal must be Figure 3 instead of Figure 2. Moreover, the value indicated in this line for average NH4-N concentration (125 mg/L) is not exactly the same value indicated in table 1. Also, the average value should be indicated including the standard deviation.

10.  In figures 2, 3 and 4, left Y title must be also changed, because it is not only related to COD, NH4-N or TP in the influent but also un the effluents from anaerobic and aerobic reactors.

11.  In my opinion, one of the most important contributions of this manuscript is section 3.3., the evaluation of adsorption kinetics using theoretical models and comparing their results with the experimental ones is the most innovative part of this study. Maybe, this section could be improved comparing these results with some other published works and increasing the discussion about these results.

12. Conclusions must be related to the results obtained in the own manuscript, sentences such as “The proposed method offers several advantages over conventional treatment methods, such as lower energy consumption, reduced sludge production, and higher removal efficiencies” are not really concluded from this work. Just the removal efficiencies have been evaluated in this manuscript.  

 

Hope these suggestions are taken into consideration and help to improve the quality of this manuscript.

Thank you.

English language need to be revised. Some mistakes such as the one found in line 70 (Biological methods are commonly employed for the treatment of LL due to...), can be found along the text. Please, check the whole manuscript.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The manuscript titled: Integrated anaerobic-aerobic MBBR and biochar adsorption for efficient removal of organic matter and nutrients from Brazilian landfill leachate.

1. In the keywords. Please, make m of the word moving in capital form.

2.  You added the ammonium-nitrogen as I asked before but where others? Where Please, the number of low OM and TP in the previous study like you made for COD and BOD?

3. Please, revise the numbering of headings its fault in some places. For example: Operating procedures in page 5 must be 2.2. not 2.1. Please, revise the whole manuscript.

4. Please, revise again lines no. 354–356.

9. Where this sentence which you said in the response letter that you added?

“The majority of contaminants are adsorbed within the first 30 minutes of the experiment (71.4%, 77.6% and 75.6% for COD, NH₄-N and TP respectively). This observation can be attributed to the availability of adsorption sites on the material's surface at the beginning of the experiment [40]. The adsorption capacity increases rapidly during the initial phase, and it takes approximately 60 minutes to reach a steady state (84.4%, 93.7% and 87.8% for COD, NH₄-N and TP respectively).”

10. Please, make spaces between words. For example line no. 468. Revise whole manuscript.

11. About question: Where is the kinetic for BOD?  Please, add this explanation in the manuscript for the reader “The authors did not perform BOD5 kinetics as, with the respirometric method they used, the error is quite high and therefore they preferred to measure only the BOD5 of the raw effluent and the effluent after treatment in order to assess the initial and final BOD5/COD ratio. Therefore, the final BOD5 values for the processes and the percentage removals as well as the final BOD5/COD ratio were included in the text”

12. Please, delete the comments highlights in the whole manuscript.

13. In FTIR spectra, the peak at 1625cm^-1 is refer to C=O while the peak at 1380 cm^-1 is refer to C=C. Please, correct.

14. The word “880 cm⁻¹”  in line 294. What you mean? Its uncompleted.

 

GOOD LUCK

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Please accept after the authors have made these revisions.

Comments on sustainability-2561061

Dear Sir/Madam,

The manuscript “Integrated anaerobic-aerobic MBBR and biochar adsorption for efficient removal of organic matter and nutrients from Brazilian landfill leachate” is being revised by the authors. Although the authors have tried to address maximum comments but there are still some comments that need to be answered for the article to be suitable for publication. (Minor).

Comment 4: There are various other methods for leachate removal (i.e., freeze drying etc.), why the authors have selected only biological methods for the study. The authors need to explain this selection in light of literature in order to prove their particular selection. Add more information to rearrange the Introduction's last paragraph as; present a summary of the above literature review, research gaps should be highlighted in comparison with the literature review. Explain, how this study is different from others? The novelty of this study should be mentioned here.

No such improvement is observed in the introduction section.

Comment 5: Table 1 needs to be compared with literature.

The authors have not still referred literature in the table.

 

 

 

 

 

Thank You

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

In my opinion, the manuscript has been highly improved. I would like to thank the authors for taking into consideration all my suggestions, especially regarding the Introduction section and the renewed Results and Discussion included in the manuscript after revision. There are only few things that I would like to mention:

1. According to your answer to point 7 in the review, "The samples collected monthly (approx. for 9 months from January to the beginning of September) were stored individually at 4°C for the entire time before starting the experiments". It means that some LL samples were stored from january to september. In my opinion, eventhough they are kept at 4ºC, they can be degraded after so much time and, subsequently, the results obtained in the experiments can be altered and&or affected by the storage time. This is an important point for me..

2. The second one is related to the english language as some mistakes were not removed yet.

Best of luck.

Some mistakes were not removed yet.

Author Response

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