Co-Treatment of Landfill Leachate and Liquid Fractions of Anaerobic Digestate in an Industrial-Scale Membrane Bioreactor System
, Pascal F. Beese-Vasbender 2, Himanshu Himanshu 1, Christian Wolf 1 and Astrid Rehorek 1
Round 1
Reviewer 1 Report
Reviewer Reports:
I recommend major amendments at this level.
General comments:
I reviewed the manuscript entitled “Effective and sustainable operation of an industrial-scale membrane bioreactor system during the combined treatment of two high strength industrial wastewaters”. The work carried out in the manuscript is interesting and aimed at investigating the possibility of treating landfill leachate in combination with liquid fractions from an anaerobic OFMSW digestion in a full-scale membrane bioreactor LTP with different volumes ratios based on NH4-N load. However, there are several points authors should kindly concentrate on. The manuscript has a lot of information however there are some lacking connectors and the writing style makes it very confusing. I suggest authors take a closer look and adjust the write-up to be more precise and appealing to the readers. The innovation and the importance of this work are not clearly highlighted in the abstract, introduction, and conclusions. The explanation of each section is shallow and needs more elaboration. The authors need to emphasize the research novelty, research significance, and contributions to academics and practices. Please work on this and prove to us why this work is valuable. Please remove all the multiple references. After that please check the manuscript thoroughly and eliminate all the lumps in the manuscript. This should be done by characterizing each reference individually. This can be done by mentioning 1 or 2 phrases per reference to show how it is different from the others and why it deserves mentioning. This comment is applied all over the paper. Please carefully check, revise and improve the whole manuscript as there are few syntax/grammatical errors. The service of an expert in the use of English in scientific writings should be sought if necessary. Too many abbreviations are used in the analysis and results. I recommend a nomenclature section for the abbreviations and variables used throughout the passage.Highlights are necessary for this journal. It is highly recommended to provide a graphical abstract, as it will increase the visibility of the work and make the manuscript more appealing. The detailed comments can be seen below:
Detailed comments:
Title: To me, the title is not well fit but it is the choice of the authors.
Abstract:
In the abstract, it should have one sentence per each: context and background, motivation, hypothesis, methods, results, and conclusions. In the abstract, please add an indication of the achievements from your study that are relevant to the journal scope. Please be concise - maximum 1-2 lines. The abstract should state briefly the purpose of the research, the principal results, and major conclusions. Avoid ALL acronyms in the abstract.
Introduction:
The introduction section, should follow the state of the art in this field and review what has been done, for supporting the research gap and the significance of this study. Please improve the state of the art overview, to clearly show the progress beyond the state of the art. The lack of proper justification creates the wrong impression that the authors are unaware of the recent developments. In the introduction section, the author provides many citations and related works. However, what is the research gap? Which is not presented well. The concluding part of the introduction is not convincing enough. More critical discussion for better highlighting the novelty and significant observations from the study raised by the reviewer. The relevant reference may be of interest to the author according below:
https://www.mdpi.com/2073-4441/10/5/595
https://www.deswater.com/DWT_abstracts/vol_143/143_2019_208.pdf
https://www.sciencedirect.com/science/article/pii/B9780128212646000115
Please eliminate the use of redundant words. Eg. In this way, Recently, Respectively, therefore, currently, thus, hence, finally, to do this, first, in order, however, moreover, nowadays, today, consequently, in addition, additionally, furthermore. Please revise all similar cases, as removing these term(s) would not significantly affect the meaning of the sentence. This will keep the manuscript as CONCISE as possible. Please check ALL. Avoid beginning or ending a sentence with one or a few words, they are usually redundant. Kindly revise all.
Materials and Methods:
Overall the method is clear and sufficient. Please provide references in this section. Overall the method is rich in content and with sufficient details. Please avoid having one heading after another with no discussion in between as in the case of Sections 2 and 2.1. Kindly inspect the entire document for similar instances and revise accordingly.
Results and Discussion:
Please provide error bars for all the figures. The explanation of the results should be elaborated. What can you conclude from the results? Furthermore, it is advised to compare the result with recent relevant state-of-the-art in the result section. The authors need to present how the results can be validated and verified.
Conclusions:
Conclusions must go deeper. Conclusions are not just about summarizing the key results of the study it should highlight the insights and the applicability of your findings/results for further work. Please make it more concise and show only the high-impact outcomes. All conclusions must be convincing statements on what was found to be novel, and impactful based on the strong support of the data. The conclusion is pretty generic and fails to provide any improvement in the existing knowledge base. The conclusion should be clear, coherent, and concise.
References:
Bibliography style is not always consistent, please check the reference section carefully and correct the inconsistency.
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer,
Foremost, I'd like to thank you for reviewing the manuscript and providing suggestions and detailed explanations about each section, reference, and ideas for improving the article's quality. The revised manuscript has been improved in response to your suggestions. The section that has been completely rewritten has been highlighted in yellow. Small grammatical errors have been corrected but not highlighted throughout the manuscript. The revised manuscript includes a list of abbreviations and a graphical abstract, as well as the removal of most unnecessary abbreviations.
Title: To me, the title is not well fit but it is the choice of the authors.
Response: The title has been changed to “Co-treatment of Landfill Leachate and Liquid Fractions of Anaerobic Digestate in an Industrial scale Membrane Bioreactor System”.
Abstract:
In the abstract, it should have one sentence per each: context and background, motivation, hypothesis, methods, results, and conclusions. In the abstract, please add an indication of the achievements from your study that are relevant to the journal scope. Please be concise - maximum 1-2 lines. The abstract should state briefly the purpose of the research, the principal results, and major conclusions. Avoid ALL acronyms in the abstract.
Response: Abstract part is completely rewritten (marked in yellow) in the suggested format, except one all acronyms have been eliminated.
Introduction:
The introduction section, should follow the state of the art in this field and review what has been done, for supporting the research gap and the significance of this study. Please improve the state-of-the-art overview, to clearly show the progress beyond the state of the art. The lack of proper justification creates the wrong impression that the authors are unaware of the recent developments. In the introduction section, the author provides many citations and related works. However, what is the research gap? Which is not presented well. The concluding part of the introduction is not convincing enough. More critical discussion for better highlighting the novelty and significant observations from the study raised by the reviewer. The relevant reference may be of interest to the author according below:
https://www.mdpi.com/2073-4441/10/5/595
https://www.deswater.com/DWT_abstracts/vol_143/143_2019_208.pdf
https://www.sciencedirect.com/science/article/pii/B9780128212646000115
Please eliminate the use of redundant words. Eg. In this way, Recently, Respectively, therefore, currently, thus, hence, finally, to do this, first, in order, however, moreover, nowadays, today, consequently, in addition, additionally, furthermore. Please revise all similar cases, as removing these term(s) would not significantly affect the meaning of the sentence. This will keep the manuscript as CONCISE as possible. Please check ALL. Avoid beginning or ending a sentence with one or a few words, they are usually redundant. Kindly revise all.
Response: Thank you so much for the suggestions and references. The introduction section has been entirely revised to highlight the current state of the art and to examine what has been done on a lab and in a pilot plant scale with various treatment approaches. Following a thorough review of the literature, it was discovered that co-treatment of these two high-strength wastewaters, landfill leachate and liquid fractions of anaerobic digestate from biodegradable municipal waste, had not previously been investigated in an industrial-scale landfill leachate treatment plant. With this study, we can say that long-term co-treatment is possible without any toxic effects on biology and without any changes in the leachate treatment plant's maintenance and operational costs, which is a significant advancement in the state of the art. Multiple citations have been removed from the revised text, and the research gap has been clearly stated.
Materials and Methods:
Overall the method is clear and sufficient. Please provide references in this section. Overall the method is rich in content and with sufficient details. Please avoid having one heading after another with no discussion in between as in the case of Sections 2 and 2.1. Kindly inspect the entire document for similar instances and revise accordingly.
Response: The figures and text in the Materials and Methods section have also been changed. The headings have been clearly structured, and those with no discussion between them have been removed. The entire manuscript was written in this manner.
Results and Discussion:
Please provide error bars for all the figures. The explanation of the results should be elaborated. What can you conclude from the results? Furthermore, it is advised to compare the result with recent relevant state-of-the-art in the result section. The authors need to present how the results can be validated and verified.
Response: Yes, changes have been made to figures and error bars have been included. Results and Discussion section is elaborated now by comparing our results with the relevant sate of the art and validated.
Conclusions:
Conclusions must go deeper. Conclusions are not just about summarizing the key results of the study it should highlight the insights and the applicability of your findings/results for further work. Please make it more concise and show only the high-impact outcomes. All conclusions must be convincing statements on what was found to be novel, and impactful based on the strong support of the data. The conclusion is pretty generic and fails to provide any improvement in the existing knowledge base. The conclusion should be clear, coherent, and concise.
Response: Conclusion part is entirely rewritten by showing the novel work of this study and high-impact outcomes have been highlighted
References:
Bibliography style is not always consistent, please check the reference section carefully and correct the inconsistency.
Response: Bibliography style and reference section has been made consistent
We look forward to hearing from you in due time regarding our submission and to respond to any further questions and comments you may have.
Sincerely
Nitesh Babu Annepogu
Author Response File: Author Response.pdf
Reviewer 2 Report
This paper investigates the combination of treating the anaerobic digestate with landfill leachate on an industrial scale.
The study involved long-term observation based on real-time operating data, which strengthens the value in applicational practice.
However, the writing and organization of this paper are far from good to present its significance, especially for the introduction and conclusion that weaken the readability of this paper.
Here are several issues to be considered in your revision,
1. The introduction part needs a re-organization. The long only-two structure fails to give clear and logical line, making the given information difficult to guide readers to clear and important contents.
2. What is the purpose for setting the two parallel bioreactor lanes (L-1 and L-2)? Are they completely isolated and operate without mutual influence? How are they comparable as the C/N value and other initial conditions are not consistent?
3. Line 104-106: is not convincible to judge merely based on expense. you should list a clear and persuasive reason why biologicals should be considered priorly even if it is a less efficient process.
4. Line 159-166: they are just the background, and have weak relation to figure 1. please make it concise by separating it from the current paragraph.
5. Line 183 OFMSW in L183 first actually appears in line 149, and after L181.
6. Line 193 WW wastewater? MBR? too many XX without an explanation for their first appearance. please add an Abbrev.
7. Line 231 Is the UF pumping process a large proportion of the total energy consumption? why does BR 2-3 need a connection to the UF storage tank instead of connecting to the pump directly?
which I think will involve more pump loss and more complicated adjustment with the increasing concentration?
8. Section 2.4: Clearly point out in the beginning, the purpose is to gain a lower value of what parameters by adjusting what variables? Is there quantitive goal value/existed value in other advanced processes/ averaged value of the same system type for pursuing better performance?
9. NH4-N Load from L1 increases from 0 in phase 0 to 10 in phase 1 and 20 in phase 2. L2 is always 0. Can figure 5 reflect such a trend?
10. Line 467： Is your research comparable to other literature data as they are at the same production level? In other words, for the bioreaction process, are they easily scaled up to a large production output with the same efficiency?
11. Figure 7: L2-NRE, why does it fluctuate severely and finally drop to lower values at the final stage?
12. Line 612: Please specify exceeds to which threshold value?
13. Conclusions, L666-677 is just common sense, overwhelmed the highlight from your own unique research, suggest separating to highlight the value of this study.
Additionally, Acknowledgments: Is there a fund number to be declared for this project?
Author Response
Dear Reviewer,
First and foremost, I want to express my gratitude for taking the time to review the manuscript and offer suggestions for improving its quality. The section that has been completely rewritten has been highlighted in yellow. Small grammatical errors have been corrected but not highlighted throughout the manuscript. The revised manuscript includes a list of abbreviations and a graphical abstract, as well as the removal of most unnecessary abbreviations. The following text responds to the questions you posed.
- The introduction part needs a re-organization. The long only-two structure fails to give clear and logical line, making the given information difficult to guide readers to clear and important contents.
Response: In the revised manuscript, the introduction is fully rewritten.
- What is the purpose for setting the two parallel bioreactor lanes (L-1 and L-2)? Are they completely isolated and operate without mutual influence? How are they comparable as the C/N value and other initial conditions are not consistent?
Response: The goal of the two parallel lanes was to examine if liquid fractions of anaerobic digestate cotreatment had any toxic effects on biocoenosis in lane-1 and compare it to lane 2, which was treated solely with landfill leachate but at higher volumes. The L-2 ultrafiltration system can handle volumes of up to 320 m3/d, whereas the L-1 ultrafiltration system can only handle 150 m3/d. As a result, L-2 was always used for higher volumes. Additionally, We had to treat definite volumes per day because it was an industrial scale plant, and due to some authority restrictions and approvals, we did not have the flexibility to treat equal volumes in both lanes.
Yes, L-1 and L-2 are completely separate from one another and operate independently from each other. After the activated sludge treatment, they have individual ultrafiltration systems.
Because the influent volume pumped in lane-2 was nearly double that of lane-1, the C/N value and the starting circumstances were different. The given external carbon source for L-2 was lower during the experiment, and the N-load was larger since the leachate volume was higher. That is why, in further studies, the C-source will be raised, and the recirculation ratio will be reduced, allowing for increased anaerobic time and to utilize biodegradable COD in leachate. It is also planned to perform microbial community analysis for the samples obtained at different phases of the experiment and compare it with selective oxygen uptake rate measurements. This enables for a more in-depth analysis of the dominant species and abundance of distinct bacterial groups at different stages of the experiment.
- Line 104-106: is not convincible to judge merely based on expense. you should list a clear and persuasive reason why biologicals should be considered priorly even if it is a less efficient process.
Response: The revised manuscript's line 110-115 explains the answer to this query.
- Line 159-166: they are just the background, and have weak relation to figure 1. please make it concise by separating it from the current paragraph.
Response: Figure 1 was included in the old manuscript to provide a comprehensive overview of leachate collection and flow to the landfill leachate treatment plant. However, I do see your perspective. In the revised version, figure 1 has been replaced with a new figure that is more appropriate for the context.
- Line 183 OFMSW in L183 first actually appears in line 149, and after L181.
Response: In the revised version abbreviations are clearly sorted out
- Line 193 WW wastewater? MBR? too many XX without an explanation for their first appearance. please add an Abbrev.
Response: In the revised version of manuscript abbreviations are clearly sorted out and a list of abbreviations is included.
- Line 231 Is the UF pumping process a large proportion of the total energy consumption? why does BR 2-3 need a connection to the UF storage tank instead of connecting to the pump directly? which I think will involve more pump loss and more complicated adjustment with the increasing concentration?
Response: Yes, the UF pumping process consumes large amounts of total energy. Initially, the sludge from both lanes was pumped into a UF storage tank and then transferred to two distinct ultrafiltration units before the cotreatment studies began. However, in this investigation, the UF storage tank was utilized just for L-2 to avoid mixing sludge from both lanes.
- Section 2.4: Clearly point out in the beginning, the purpose is to gain a lower value of what parameters by adjusting what variables? Is there quantitive goal value/existed value in other advanced processes/ averaged value of the same system type for pursuing better performance?
Response: Section 2.3 (in the revised version) has been updated.
- NH4-N Load from L1 increases from 0 in phase 0 to 10 in phase 1 and 20 in phase 2. L2 is always 0. Can figure 5 reflect such a trend?
Response: During phase 1 and 2 of this investigation, percentage NH4-N load (v/v) from LF-AD was increased in L-1 influent. L-2 was always 0 because we have treated only landfill leachate. Figure 4 (revised manuscript), shows the average concentrations of NH4-N, NO2-N, and NO3-N in the first nitrification bioreactors of both lanes. Therefore, the trend of NH4-N load was not shown in figure 5. The NH4-N load on the LLTP is discussed in section 3.3.
- Line 467： Is your research comparable to other literature data as they are at the same production level? In other words, for the bioreaction process, are they easily scaled up to a large production output with the same efficiency?
Response: N-Load is comparable in both cases. We have used a biological process in combination with ultrafiltration and granular activated carbon treatment in this study, and the process demonstrated good ammonium and COD removal efficiencies.
- Figure 7: L2-NRE, why does it fluctuate severely and finally drop to lower values at the final stage?
Response: As we wanted to keep the influent rate constant in L-1 while also treating the higher volumes of leachate generated during the winter, the influent volumes in L-2 were higher. Because of the increased influent volumes, nitrogen load rate in L-2 was higher, resulting in a C/N imbalance and NO3-N instabilities in the system. NO3-N accumulation in L-2 lead to fluctuations in NRE. In further study, to minimise C/N imbalances, it is intended to increase the input of C-source and extend the residence time of activated sludge in the anaerobic phase by changing the current recirculation ratio between bioreactors to better use the biodegradable COD concentrations present in landfill leachate.
Note: The highest influent capacity of the landfill leachate treatment plant in this investigation was 450 m3/d in the winter and 280 m3/d in the summer.
- Line 612: Please specify exceeds to which threshold value?
Response: The revised manuscript's line 743-745 explains the answer to this query.
- Conclusions, L666-677 is just common sense, overwhelmed the highlight from your own unique research, suggest separating to highlight the value of this study.
Additionally, Acknowledgments: Is there a fund number to be declared for this project?
Response: In revised manuscript, conclusion part is entirely rewritten (marked in yellow) by showing the novel work of this study and high-impact outcomes have been highlighted
We look forward to hearing from you soon regarding our submission and to respond to any further questions and comments you may have.
Sincerely
Nitesh Babu Annepogu
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Reviewer Reports:
I have reviewed the revised manuscript entitled" Co-treatment of Landfill Leachate and Liquid Fractions of An-aerobic Digestate in an Industrial scale Membrane Bioreactor System". The paper is modified according to the comments. The paper is recommended for publication.
Reviewer 2 Report
Authors did a good revision and addressed most of my concern. I expect this paper to be published and more valuable fruits for authors' future research.
