Comparative Study on Advanced Nitrogen Removal of Landfill Leachate Treated by SBR and SBBR
Round 1
Reviewer 1 Report
- Line 76 «Multi 3620 analyzer for the detection of pH, DO, and ORP, mechanical stirrers…». I understand that these text reductions are well-known, however, for a wide range of readers it is necessary to give explanation.
- Line 80 «The biofilm filler consists of polyurethane and other polymer materials…». What does «other polymer materials» mean? The fillers were made of various materials or contains a mixture of polymers? Why fillers made of pure polyurethane were not used.
- Line 85. «The characteristics of the Landfill leachate are shown in Table 2». Authors need to specify the delivery and storage time and storage of The Landfill Leachate samples. Have it been taken into account possible losses of nitrogen due to transportation and storage of landfill leachate samples?
- Line 98 «The DO concentration was maintained over a range from 2.0mg/L to 4.0 mg/L during the aeration phase». How did the amount of dissolved oxygen maintained? What gas mixture was used for aeration, clean oxygen or air were used? What is the flow rate of the gas mixture?
- Figure 1 (both schemes) written "AETOR" was probably meant "Aerator".
- Give explanation to the text reduction «TN (TNinf, TNeff)» – total nitrogen.
- Figure 5, 6, give explanation to the text reduction «NAR» - nitrous acid reaching
- It is necessary to combine Figures 2 and 3; 4 and 5.
- Figure 6. «The nitrogen removal amount ranged 75 mg/L to 80 mg/L with of SND…». However, the left Y-axis to which the curves belong is indicated as "Amount of Endogenous Denitrification". It is possible that the names of the Y-axes are incorrectly placed.
- Figure 6. Specify the Y-axises by arrows for a group of curves.
- Line 156. «The nitrogen removal of leachate with these two systems was composed of SND and endogenous denitrification (ED)…» however, on Figure 6, the value of "endogenous denitrification" in 60 days is higher for SBR. Could the Authors explain this phenomenon?
- Figure 6. For SSBR "endogenous denitrification" in 65 days there is a sharp peak (blue stars). It is necessary to give an explanation to this phenomenon.
- Line 174. «…was shown in Fig. 6…» have to specified as "Figure 7".
- Figure 7. The Authors show the effect of cycles duration on the efficiency of nitrogen removal. It would be nice to duplicate these values of nitrogen removal efficiency on Figure 7.
- Line 188. «It's mainly caused by the denitrifying bacteria's adsorption…» The Authors should clarify what "bacteria's adsorption" means.
- Line 192. «After the start of aeration, the ammonia nitrogen was dropped drastically». From the text it is not clear the time of the start of aeration. In addition, in Figure 8, you have to specify the start the time of aeration.
- Line 192. What does «SD» mean?
- Line 206-214. The text is almost completely repeated with the previous paragraph (Line 185-194). The Authors must reconsider and reduce the discussion, avoiding the text repetition.
Author Response
Point 1: Line 76 «Multi 3620 analyzer for the detection of pH, DO, and ORP, mechanical stirrers…». I understand that these text reductions are well-known, however, for a wide range of readers it is necessary to give explanation.
Response 1:
Thanks for your suggestions, the following explanations have been added in the article: potential of hydrogen (pH), dissolved oxygen (DO), and oxidation-reduction potential (ORP).
Point 2: Line 80 «The biofilm filler consists of polyurethane and other polymer materials…». What does «other polymer materials» mean? The fillers were made of various materials or contains a mixture of polymers? Why fillers made of pure polyurethane were not used.
Response 2:
Other polymer materials belong to the trade secrets of the filler manufacturer, which is inconvenient for the manufacturer to disclose. In order to ensure the hydrophilicity and mechanical hardness of the filler, the filler manufacturer is generally composed of a variety of materials.
Point 3: Line 85. «The characteristics of the Landfill leachate are shown in Table 2». Authors need to specify the delivery and storage time and storage of The Landfill Leachate samples. Have it been taken into account possible losses of nitrogen due to transportation and storage of landfill leachate samples?
Response 3:
The landfill leachate was taken once a month and use closed plastic barrels for sampling and transportation. After sampling, leachate was stored in a refrigerated environment at 4 ℃ to reduce the impact of microorganisms on it. The characteristics of leachate was tested before each water inflow.
Point 4: Line 98 «The DO concentration was maintained over a range from 2.0mg/L to 4.0 mg/L during the aeration phase». How did the amount of dissolved oxygen maintained? What gas mixture was used for aeration, clean oxygen or air were used? What is the flow rate of the gas mixture?
Response 4:
Between the air diffuser and the air compressor, the aeration volume was controlled by the rotameter, and the dissolved oxygen concentration was detected by the Multi 3620 an-alyzer. Air was used for aeration. And the flow rate of the gas mixture was from 0.4m3/h to 4m3/h.
Point 5: Figure 1 (both schemes) written "AETOR" was probably meant "Aerator".
Response 5:
Indeed, aerator has modified the text in the figure. We are really sorry.
Point 6: Give explanation to the text reduction «TN (TNinf, TNeff)» – total nitrogen.
Response 6:
Explanations have been added in the article, as following:
TNinf: Total nitrogen concentration of influent;
TNeff: Total nitrogen concentration of effluent.
Point 7: Figure 5, 6, give explanation to the text reduction «NAR» - nitrous acid reaching
Response 7:
Explanations have been added in the article, as following:
NAR: Nitrite accumulation rate
Point 8: It is necessary to combine Figures 2 and 3; 4 and 5.
Response 8:
We have combined figures 2 and 3, 4 and 5 for readers to read.
Point 9: Figure 6. «The nitrogen removal amount ranged 75 mg/L to 80 mg/L with of SND…». However, the left Y-axis to which the curves belong is indicated as "Amount of Endogenous Denitrification". It is possible that the names of the Y-axes are incorrectly placed.
Response 9:
The data in the article is wrong, and the correct description should be: The nitrogen removal amount ranged ,150 mg/L to 160mg/L with of SND can be implemented through the aerobic-anoxic microenvironment of biofilm in SBBR, which was up by 40%-50% in comparison to 100mg/L to 110mg/L in SBR.
Point 10: Figure 6. Specify the Y-axises by arrows for a group of curves.
Response 10:
We have modified the coordinate name of Y-axis to make it easier for readers to understand the contents of the diagram.
Point 11: Line 156. «The nitrogen removal of leachate with these two systems was composed of SND and endogenous denitrification (ED)…» however, on Figure 6, the value of "endogenous denitrification" in 60 days is higher for SBR. Could the Authors explain this phenomenon?
Response 11:
The wrong expression of the previous data may mislead you. The ordinate axis in Figure 6 is not wrong, so the problem you said does not exist. We are so sorry.
Point 12: Figure 6. For SBBR "endogenous denitrification" in 65 days there is a sharp peak (blue stars). It is necessary to give an explanation to this phenomenon.
Response 12:
From the 66th day, the influent quality changed greatly, and the influent ammonia nitrogen concentration increased. The change of water quality lengthened the nitrification time of the system, so the amount of SND in the system increased and the amount of ED decreased accordingly, resulting in a peak of the previous amount of ED.
Point 13: Line 174. «…was shown in Fig. 6…» have to specified as "Figure 7".
Response 13:
It should be Figure 7. It has been modified. Thank you.
Point 14: Figure 7. The Authors show the effect of cycles duration on the efficiency of nitrogen removal. It would be nice to duplicate these values of nitrogen removal efficiency on Figure 7.
Response 14:
Your suggestion is very good. We have added the data. Thank you.
Point 15: Line 188. «It's mainly caused by the denitrifying bacteria's adsorption…» The Authors should clarify what "bacteria's adsorption" means.
Response 15:
Microbial degradation of organic matter needs to adsorb organic onto the cell wall, and then enter the cell body through the cell wall and cell membrane. Therefore, the removal process of organic matter by denitrifying bacteria realized adsorption and reabsorption, and finally respiratory utilization. It has been modified. Thanks for your suggestions.
Point 16: Line 192. «After the start of aeration, the ammonia nitrogen was dropped drastically». From the text it is not clear the time of the start of aeration. In addition, in Figure 8, you have to specify the start the time of aeration.
Response 16:
In Section 2.3 Operational procedure, this paper introduced the operation mode of the reactor, that is, anaerobic stirring for 60 minutes after influent, and then aeration. OK, we have modified the diagram.
Point 17: Line 192. What does «SD» mean?
Response 17:
This is a spelling error and should be changed to SND.
Point 18: Line 206-214. The text is almost completely repeated with the previous paragraph (Line 185-194). The Authors must reconsider and reduce the discussion, avoiding the text repetition.
Response 18:
The article has been modified. Thank you for your suggestions.
Reviewer 2 Report
This paper is rejected as it is not complete and lacks proper scientific structure in view of the followings:
- There is no discussion of the results based on scientific publications of previous work and for the various explanations mentioned in the text.
- The materials and methods does not contain any information about the biofilm reactor, how it was formed, how to verify its formation, etc.
- There is no contemplation to the role of the anammox bacteria in the system which might change how the data is presented and discussed.
- There is no statistical analysis of the results to verify the differences.
- English language is poor in many parts making it confusing even for editing.
Author Response
Point 1: There is no discussion of the results based on scientific publications of previous work and for the various explanations mentioned in the text.
Response 1:
I have added comparison with the existing research results in the discussion. Thank you for your comments.
Point 2: The materials and methods does not contain any information about the biofilm reactor, how it was formed, how to verify its formation, etc.
Response 2:
After five days of operation of SBBR, biofilm visible to the naked eye was formed on the filler.
Point 3: There is no contemplation to the role of the anammox bacteria in the system which might change how the data is presented and discussed.
Response 3:
The experiment was mainly divided into three processes: anaerobic stage, aerobic stage and later anoxic stage. There was no nitrification in the anaerobic section in the early stage, so there was no production of nitrite. Naturally, there was no ANAMMOX. After the consumption of ammonia nitrogen in the anaerobic section in the later stage, there was also no condition for ANAMMOX. In the middle aerobic section, through the change of matrix in a cycle, we could see that the removal rate of ammonia nitrogen was basically the same as that of nitrite production. If the system has an obvious anaerobic ammonia oxidation process, according to the reaction law of anaerobic ammonia oxidation, the consumption ratio of ammonia nitrogen and nitrite was 1:1.3, and the nitrite nitrogen in the aerobic reaction process should increase very slowly. Therefore, we inferred that the possibility of ANAMMOX in the system was little.
Point 4: There is no statistical analysis of the results to verify the differences.
Response 4:
Data in this paper were obtained through three parallel experiments. Mean with standard deviation had been plotted in Figure. 7 and 8 .
Point 5: English language is poor in many parts making it confusing even for editing.
Response 5:
Thank you for your suggestions. We had found a third-party organization to improve our English language.
Author Response File: 
Author Response.docx
Reviewer 3 Report
The elements of the article listed below require improvement:
p. 1, lines 12-13: please use capitalic in the names of SBR method and correct spaces
p. 1, line 13: should be N-NH4+
p. 1, Lines 14, 17, 26, 27: before unit must be space
p. 1, line 26: should be mg/L not mg / L
p. 2, line 46: should be (AO), also please check Anaerobic-Oxic or Oxidtaion?
p. 2, line 76: explain shortcuts DO and ORP
p. 2, line 89: the units were described without uppercases; please also decide to use one notation of units in whole paper
p. 3, line 106: see comment p. 1, line 13
In section Materials and Methods Authors decribed standard deviation of presented values. Please explain how they were measured and what components they contain.
p. 4, line 122: should be 650±50 mg/L
Overall merit:
The paper is written in good English. Authors describe some information about SBR and SBBR methods in Introduction section. In the text I suggest describe more informatin about landfills, probe sampling and weather during sampling. In results section Authors present inetersting information but They must supplement the text with discussion. It is very important to show how obtained results readers could use in own research field or use as industrial factors in waste water treatment plant. The conclusion section is very short and present informations described in section 3 - I suggest write some informatins about usage of obtained values, what could be also measured/changed in SBR and SBBR process.
Author Response
Point 1: p. 1, lines 12-13: please use capitalic in the names of SBR method and correct spaces
Response 1: The article has been modified as required. Thank you.
Point 2: p. 1, line 13: should be N-NH4+
Response 2: The article has been modified as required. Thank you.
Point 3: p. 1, Lines 14, 17, 26, 27: before unit must be space
Response 3: The article has been modified as required. Thank you.
Point 4: p. 1, line 26: should be mg/L not mg / L
Response 4: The article has been modified as required. Thank you.
Point 5: p. 2, line 46: should be (AO), also please check Anaerobic-Oxic or Oxidtaion?
Response 5: Anaerobic-oxic has no problem. Thank you.
Point 6: p. 2, line 76: explain shortcuts DO and ORP
Response 6: It has been explained in the article. Thank you.
Point 7: p. 2, line 89: the units were described without uppercases; please also decide to use one notation of units in whole paper.
Response 7: It has been modified. Thank you.
Point 8: p. 3, line 106: see comment p. 1, line 13
In section Materials and Methods Authors decribed standard deviation of presented values. Please explain how they were measured and what components they contain.
Response 8: In the part of Materials and Methods, we introduce the main contents of the experiment. DO, pH, ORP and temperature were detected and recorded in real time by WTW equipment. Other water quality data were detected by international standard methods, which were described in detail in the cited reference.
Point 9: p. 4, line 122: should be 650±50 mg/L
Response 9: The article has been modified as required. Thank you.
Point 10:The paper is written in good English. Authors describe some information about SBR and SBBR methods in Introduction section. In the text I suggest describe more informatin about landfills, probe sampling and weather during sampling. In results section Authors present inetersting information but They must supplement the text with discussion. It is very important to show how obtained results readers could use in own research field or use as industrial factors in waste water treatment plant. The conclusion section is very short and present informations described in section 3 - I suggest write some informatins about usage of obtained values, what could be also measured/changed in SBR and SBBR process.
Response 10: We have revised the article according to your requirements. Thank you for your suggestions. Please see the article for details.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
All comments have been corrected by the Authors.
Author Response
Thanks for your time. Best Wishes!
Author Response File: Author Response.docx
Reviewer 3 Report
Dear Authors, thank You for revised paper. The conclusion section is still very short and must be added before presentations.
Author Response
Point 1: Dear Authors, thank You for revised paper. The conclusion section is still very short and must be added before presentations.
Response 1:
Thank you for your suggestions. We have appropriately enriched the conclusions.
Author Response File: Author Response.docx
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
