Experiments and Modeling for Investigation of Oily Sludge Biodegradation in a Wastewater Pond Environment
, Najem Alarwan 2, Maheswari Chandrasekaran 3, Aishwarya Sundaram 1, Tonje Milde 4 and Saad Rasool 5Round 1
Reviewer 1 Report
This work is regard the oily material biodegradation using dispersants and petroleum-degrading microbial consortia, along with modeling of this system. It is interesting and contain enought data to consider for publishing. However, the author should consider several significant modifications previous to submit newly:
The half of the abstract is an introduction to the work and no relevant methods (dispersants,...) or results (values of biodegradation) are mentioned. The methods should be better describe: The authors could include, at least, how the DE is calculated from the USEPA protocol using the values of the absorvances. Specify the operating conditions use in DE runs (temperature, experiments of the fractional factorial design). Taking into account that some variables were modified along the work, the authors can write the operating conditions (temperature, dispersant and oil quantities, ...) in the captions of the Figures. In addition the design of experiments (fractional factorial design) should be include and explain in this section (a table with the operating conditions of the runs can be prepared to place in a supplementary information). The Eq. 1 taken from the calabrese et al. (reference 9 of the mannuscript) should be revised. In the reference the parameter "D" doesn't appear and in fact in Eq. 1 doesn't have sense because 1/D=(D^(2/3)*D)^(-3/5). In addition, the exponents of the energy dissipation disagree with Calabrese and the equation was proposed for Dmax, instead of D32 (mean droplet size of Sauter). The determination of power number, Np, should be explained and values of Np should be observed in the document. The author should explained better how the Eq. 7 is obtained from the formulas for volume and surface area of a sphere, specially regard to Msxi^(1/3) x Msx^(2/3). The discussion of the results should be extended, since the most of results are not compared with other publications, neither justified (e.g. the differences obtained between dispersants are not discussed, why FFT100 could be better than other ones? why was used petroclean for the rest of the paper, being likely the worse dispersant?). Also, the authors should consider included the discussion in the same section of the results, where the experimental data are slightly commented. Some insignificant results should be placed in a supplementary information (e.g. Figure 7, that is only the representation of the Eq. 1, so there is no experimental data represented) or represented more than once (e.g. Figure 5-6 and 8, since Figure 8 doesn't contribute with more additional information, it's only the representation of equations 2-3 with the DE obtained). A section of conclusions was missed. In references section, two first paragraphs should be removed.The authors should take into account other minor details, such as:
The use of subscripts and supercripts in some units. Revise the units of some variables (e.g. in a part of the paper viscosity has the same units of the interfacial tension and hours appears as "hr", "Hrs" or with complete name "hours"). Improve the representation of the figures.
Author Response
Response to Reviewer Comments on Oily Sludge Biodegradation Paper
Open Review---1
General Comment: This work is regard the oily material biodegradation using dispersants and petroleum-degrading microbial consortia, along with modeling of this system. It is interesting and contain enough data to consider for publishing. However, the author should consider several significant modifications previous to submit newly:
Response: Thank you for the comments so that we may improve this paper. We have made modifications according to your specific comments below.
Comment 1: The half of the abstract is an introduction to the work and no relevant methods (dispersants,...) or results (values of biodegradation) are mentioned.
Response: The abstract has been modified to address this issue.
Comment 2: The methods should be better described: The authors could include, at least, how the DE is calculated from the USEPA protocol using the values of the absorbance.
Response: A more detailed description of determination of the dispersant effectiveness has been added to Section 2.1
Comment 3: Specify the operating conditions use in DE runs (temperature, experiments of the fractional factorial design). Taking into account that some variables were modified along the work, the authors can write the operating conditions (temperature, dispersant and oil quantities, ...) in the captions of the Figures.
Response: Additional test condition details have been added to figures 2 through 6, and also the fraction factorial design test conditions has been added to Table S1 of the supplementary material.
Comment 4: In addition, the design of experiments (fractional factorial design) should be include and explain in this section (a table with the operating conditions of the runs can be prepared to place in a supplementary information).
Response: The fractional factorial design has been added as supplementary table S1. It is also referred to in the text of the materials and methods section.
Comment 5: The Eq. 1 taken from the Calabrese et al. (reference 9 of the manuscript) should be revised. In the reference the parameter "D" doesn't appear and in fact in Eq. 1 doesn't have sense because 1/D=(D^(2/3)*D)^(-3/5). In addition, the exponents of the energy dissipation disagree with Calabrese and the equation was proposed for Dmax, instead of D32 (mean droplet size of Sauter).
Response: The sentences introducing equation 1 in the text have been altered to correctly refer instead that this equation comes from the Pan et al paper (reference 6), in which the subject equation was developed based on the work of Calabrese and others referenced.
Comment 6: The determination of power number, Np, should be explained and values of Np should be observed in the document.
Response: More detailed text regarding the power number calculations is added, and values of the power number calculated for the data shown in figures 4, 5, and 6 has been added in table format in the supplementary material (Tables S2, S3, S4).
Comment 7: The author should explains better how the Eq. 7 is obtained from the formulas for volume and surface area of a sphere, specially regard to Msxi^(1/3) x Msx^(2/3).
Response: The detailed derivation of equation 7 is given now in the supplementary material.
Comment 8: The discussion of the results should be extended, since most of results are not compared with other publications, neither justified (e.g. the differences obtained between dispersants are not discussed, why FFT100 could be better than other ones? why was used petroclean for the rest of the paper, being likely the worse dispersant?). Also, the authors should consider included the discussion in the same section of the results, where the experimental data are slightly commented.
Response: The discussion section has been extended in several places per this comment and other reviewers comments. Additionally, a separate conclusion section was created as suggested by another reviewer’s comment. No change was made for the last sentence of comment 8 shown above, as the reviewer’s comment is incomplete or not understandable as it was written (unknown meaning for “should consider included the discussion”).
Comment 9: Some insignificant results should be placed in a supplementary information (e.g. Figure 7, that is only the representation of the Eq. 1, so there is no experimental data represented). Some results are represented more than once (e.g. Figure 5-6 and 8, since Figure 8 doesn't contribute with more additional information, it's only the representation of equations 2-3 with the DE obtained).
Response: The authors do not believe the figures referred to are insignificant results. As an example, even though figure 8 is not showing new data, it is very helpful in demonstrating the trend of mixing power needed to achieve high levels of DE, at the different scales. Other material requested by the reviewers has been added to the supplementary material.
Comment 10: A section of conclusions was missed. In references section, two first paragraphs should be removed.
Response: The section title for Conclusions has been added, and the paragraphs referred to in the references have been removed.
Comment 11: The authors should take into account other minor details, such as the use of subscripts and superscripts in some units. Revise the units of some variables (e.g. in a part of the paper viscosity has the same units of the interfacial tension and hours appears as "hr", "Hrs" or with complete name "hours"). Improve the representation of the figures.
Response: Corrections have been made as requested.
Reviewer 2 Report
This is an interesting piece of manuscript. However, it requires the following revisions before it can be accepted for publication in Applied Sciences.
The title of the paper should be change to the following:
“Experiments and Modeling for Investigation of Oily Sludge Biodegradation in a Wastewater Pond Environment”
Include some quantitative results in the Abstract.
The Introduction should be expanded. The novelty is not elaborated. Has a previous work like this study been done before using the same conditions, dispersants, etc? What is new in this research/study?
In Section 2, include a sub-section on Experimental Design using Design Expert. Details are required since you include results from a factorial design in the results.
Page 3 line 109: Revise the sentence as follows:
“The energy dissipation and applied energy were calculated” ....
Page 6: Before including Eq. (18), you must present a detailed ANOVA results of the factorial design from Design Expert. You should provide the best model(s) and the significant factors that affected biodegradation of the oil sludge.
Page 10, Figure 9. Include details of “Conditions 1 – 4” in the figure caption for clarity of understanding.
Page 11 line 318: Correct the sentence as follows;
... “parameters presented in Section 2.2.” ....
Author Response
Response to Reviewer Comments on Oily Sludge Biodegradation Paper
Open Review 2
General Comment: This is an interesting piece of manuscript. However, it requires the following revisions before it can be accepted for publication in Applied Sciences.
Response: Thank you for the comments so that we may improve this paper. We have made modifications according to your specific comments below.
Comment 1: The title of the paper should be change to the following:
“Experiments and Modeling for Investigation of Oily Sludge Biodegradation in a Wastewater Pond Environment”
Response: The title has been changed as suggested.
Comment 2: Include some quantitative results in the Abstract.
Response: The abstract has been modified to address this issue.
Comment 3: The Introduction should be expanded. The novelty is not elaborated. Has a previous work like this study been done before using the same conditions, dispersants, etc? What is new in this research/study?
Response: The 2nd paragraph of the introduction has been revised to address these questions.
Comment 4: In Section 2, include a sub-section on Experimental Design using Design Expert. Details are required since you include results from a factorial design in the results.
Response: The Design Expert software was only used for one of the dispersant effectiveness tests, that is the one using two different dispersants in 250-mL flasks. For this particular experiment, the fractional factorial design is presented now in supplementary table S1, and referred to in the text of the materials and methods section.
Comment 5: Page 3 line 109: Revise the sentence as follows:
“The energy dissipation and applied energy were calculated” ....
Response: The suggested change has been made.
Comment 6: Page 6: Before including Eq. (18), you must present a detailed ANOVA results of the factorial design from Design Expert. You should provide the best model(s) and the significant factors that affected biodegradation of the oil sludge.
Response: The ANOVA table has been added as Table S5 in the supplementary material section. The Eqn 18 has been modified to include only those terms indicated significant by the ANOVA, and the text also now includes an identification of those terms not found to be significant.
Comment 7: Page 10, Figure 9. Include details of “Conditions 1 – 4” in the figure caption for clarity of understanding.
Response: The details of the test conditions have been added to the figure caption.
Comment 8: Page 11 line 318: Correct the sentence as follows;
... “parameters presented in Section 2.2.” ....
Response: The correction has been made.
Reviewer 3 Report
The purpose of this study was to investigate potential improvements in oily material biodegradation using dispersants and petroleum-degrading microbial consortia, along with modeling of this system. Results of the study may have important application in the field of oily sludge treatment. Authors may wish to consider the following in the revisions of their manuscript.
1.Please provide cost of dispersant and bioaugmentation formula.
2.What are the limitations of the proposed treatment methods.
3.Authors used commercially available oil substances in the study. Why actual oil substances from industrial plants were not used in the study.
4.Please provide temperature and pH data for biodegradation shaking run.
5.Please provide dissolved oxygen concentration in the biodegradation shaking run.
6.Please provide concentration of 5 different strains of bioaugmentation formula used in the biodegradation run.
7.Please plot microorganism concentration vs shaking time.
8.Please provide TOC data of biodegradation run.
9.Please comment on the limitations of dispersant effectiveness (DE) used in the study.
10.Please comment how much oil materials removal is due to biodegradation and how much is due to bio adsorption in batch biodegradation run.
11.Please clarify oil droplet diameters in Fig 7. Are diameters values based on calculated using equation 1, Line 99, or by actual measurement. If actual measurements were used, please describe methods in your text.
Author Response
Response to Reviewer Comments on Oily Sludge Biodegradation Paper
Open Review 3
General Comment: The purpose of this study was to investigate potential improvements in oily material biodegradation using dispersants and petroleum-degrading microbial consortia, along with modeling of this system. Results of the study may have important application in the field of oily sludge treatment. Authors may wish to consider the following in the revisions of their manuscript.
Response: Thank you for the comments so that we may improve this paper. We have made modifications according to your specific comments below.
Comment 1: Please provide cost of dispersant and bioaugmentation formula.
Response: The dispersants and bioaugmentation formula were provided as donations from the sources, therefore no cost was incurred in procuring them for this study.
Comment 2: What are the limitations of the proposed treatment methods.
Response: Text was added to the conclusions section to address this.
Comment 3: Authors used commercially available oil substances in the study. Why actual oil substances from industrial plants were not used in the study.
Response: As indicated in the first title, this was a preliminary study. A couple of local refinery sources were queried for supply sources of sludge, but none were able to be provided at the time the study was initiated, therefore a readily available crude oil source was used as a surrogate.
Comment 4: Please provide temperature and pH data for biodegradation shaking run.
Response: A statement indicating biodegradation tests were conducted at room temperature has been added to the figure captions. No pH data were acquired during these biodegradation tests.
Comment 5: Please provide dissolved oxygen concentration in the biodegradation shaking run.
Response: Unfortunately, no dissolved oxygen concentrations were measured during biodegradation tests.
Comment 6: Please provide concentration of 5 different strains of bioaugmentation formula used in the biodegradation run.
Response: The concentrations or relative percentages were not provided by the bioaugment vendor, as their formulation is proprietary.
Comment 7: Please plot microorganism concentration vs shaking time.
Response: The direct measurements of biomass concentration were collected during the biodegradation runs. Only residual oil mass was determined by the extraction method described in the M&M section.
Comment 8: Please provide TOC data of biodegradation run.
Response: Unfortunately, no total organic carbon data was collected during biodegradation tests.
Comment 9: Please comment on the limitations of dispersant effectiveness (DE) used in the study.
Response: Text was added to the first paragraph of the discussion section to address this.
Comment 10: Please comment how much oil materials removal is due to biodegradation and how much is due to bio adsorption in batch biodegradation run.
Response: No separate measurements were conducted on the biomass material to distinguish between these two different scenarios. This recommendation will be incorporated into future work on this project.
Comment 11: Please clarify oil droplet diameters in Fig 7. Are diameters values based on calculated using equation 1, Line 99, or by actual measurement. If actual measurements were used, please describe methods in your text.
Response: Oil droplet diameters are only calculated values from Equation 1. The caption for Figure 7 already states “Calculated ….. oil particle size……”.
Round 2
Reviewer 1 Report
The authors adressed all comments well and it is my opinion that the paper was improved. Only a minor details should be considered for publication:
1. They should consider include the meaning of RCRA (first paragraph in the introduction).
2. Revise the new equation E2, since it is expected that Mp has units of mass, but a dimensional analysis of Eq.E2 lead to conclude other units. In fact, E2 does not agree with the E4 equation where Mp is substituted from E3 by other equation.
3. Differences between Msxi and Msx should be better define, since according to E1 and E3 are the same parameters.
Author Response
Open Review---1
General Comment: The authors addressed all comments well and it is my opinion that the paper was improved. Only minor details should be considered for publication:
Response: No changes made based on this comment.
Comment 1: They should consider include the meaning of RCRA (first paragraph in the introduction).
Response: Correction has been completed.
Comment 2: Revise the new equation E2, since it is expected that Mp has units of mass, but a dimensional analysis of Eq.E2 lead to conclude other units. In fact, E2 does not agree with the E4 equation where Mp is substituted from E3 by other equation.
Response: Equation E2 was incorrect (the right hand side should be inverted). Correction has been completed in the supplementary file.
Comment 3: Differences between Msxi and Msx should be better define, since according to E1 and E3 are the same parameters.
Response: These two parameters are defined on pg 5 of the paper. The definitions have been slightly modified to make it more clear that Msxi is the initial value of the Msx parameter.
Reviewer 2 Report
You have addressed almost all the suggestions by the reviewers. However, there are still a few minor revisions to be made to improve the quality of your manuscript. These have been stated as follows:
In the introduction, you must clearly explain or state the specific objectives of the research. In the last paragraph, you presented a summary of the preliminary results, but these are not the objectives or the measurables of your work. You did not include the major outcomes of your results in the conclusion. Page 8 line 267: Please, delete "(hrs"). The correct sentence should now become: "collected at 4 time intervals, namely 0.5, 1.0, 1.5, and 2.0 hrs." Page 15 line 424: Please, change "out to 2 hrs." to "up to 2 hrs." Page 15 line 428: Delete the word "treatment" after "possible" and rewrite the sentence as follows: "dispersion as a possible oily sludge treatment method." ….Author Response
Open Review 2
Comment 1: In the introduction, you must clearly explain or state the specific objectives of the research. In the last paragraph, you presented a summary of the preliminary results, but these are not the objectives or the measurables of your work.
Response: Additional text has now been added at the very end of the second paragraph of the introduction section, to clearly state the objectives of this work.
Comment 2: You did not include the major outcomes of your results in the conclusion.
Response: A paragraph has been added at the beginning of the conclusions section to address the major outcomes of the work.
Comment 3: Page 8 line 267: Please, delete "(hrs"). The correct sentence should now become: "collected at 4 time intervals, namely 0.5, 1.0, 1.5, and 2.0 hrs."
Response: Corrections have been completed.
Comment 4: Page 15 line 424: Please, change "out to 2 hrs." to "up to 2 hrs." Page 15 line 428: Delete the word "treatment" after "possible" and rewrite the sentence as follows: "dispersion as a possible oily sludge treatment method." ….
Response: Corrections have been completed.
