Toxic Effects of Liquors Generated During Kraft Pulp Production Process on Aerobic Biomass and Growth of Selenastrum capricornutum
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe topic is relevant, and the experimental work is well conducted. Below, I offer a some suggestions aimed at improving the clarity, structure, and contextual grounding of your manuscript. I hope these comments help strengthen the scientific quality and overall impact of your work:
The introduction provides adequate background on the Kraft pulping process and its environmental implications. However, it lacks empirical grounding regarding the frequency or documented occurrence of liquor spills, which form the central motivation of the study. The authors mention that accidental spills can occur and potentially affect biological treatment and receiving ecosystems, but no quantitative data, industrial incident reports, or references are provided to support this claim. Including statistics or regulatory information would strengthen the justification for the research. In my opinion, such spills are likely to be extremely rare in modern industrial settings, making this an arguably weak justification for the study’s relevance.
Furthermore, the introduction should include a clear and concise description of the chemical recovery cycle, particularly how the different liquors (white, green, black, and condensates) are generated and recycled within the process. These streams are not simply discharged to wastewater treatment systems, but rather are mostly recovered and reused in the Kraft process. Presenting this recovery cycle is essential for readers to understand the real role and fate of these liquors in industrial practice. As it stands, the text may lead readers to believe that these streams are routinely sent to treatment lagoons, which is inaccurate and may misrepresent the operational reality of Kraft pulp mills.
The methods section is comprehensive and well organized, with adequate detail for reproducibility. The use of both respirometric analysis and algal bioassays provides a robust dual approach to toxicity assessment. However, the number of replicates should be clearly specified, especially for control treatments. Including a simplified experimental diagram or flowchart could further enhance clarity for readers unfamiliar with these techniques.
The results are presented in a logical order and are supported by well-constructed tables and figures. The interpretation of findings is generally sound, particularly the discussion on the role of pH and alkali compounds in toxicity. It is suggested, however, that the discussion be better structured by clearly separating the results related to aerobic biomass from those related to microalgal inhibition. Additionally, the authors could explore more deeply the mechanisms behind observed effects, especially the unexpected stimulation of S. capricornutum growth at low concentrations of black liquor. This observation deserves further elaboration, particularly in light of recent studies suggesting the potential valorization of black liquor as a carbon source for microbial growth.
The figures are clear and relevant, though figure captions could be more descriptive, particularly in explaining symbols and treatments. In Figure 3, it would be helpful to improve the labeling of trends and ensure visual consistency between 48h and 96h results for easier interpretation.
Moreover, to ensure a more robust and reliable interpretation of the results, the use of appropriate statistical tools is recommended. The absence of such analyses may compromise the objectivity of the interpretation, particularly in ecotoxicological studies where biological variability is expected. Including measures such as analysis of variance (ANOVA), confidence intervals, and post-hoc tests would significantly enhance the scientific rigor of the study.
The reference list is generally composed of relevant and recent sources. However, the manuscript includes only 25 references, which is relatively limited considering the technical scope and environmental complexity of the study. The authors are strongly encouraged to expand the literature review to incorporate additional studies addressing effluent toxicity, ecological risk assessment, and biological treatment systems in pulp and paper industries. Furthermore, approximately 20% of the references are self-citations, primarily from the senior author. While these citations appear methodologically justified, the authors should ensure that the manuscript reflects broader engagement with independent and international literature to support its arguments and enhance the scientific impartiality of the discussion.
Author Response
Ms. Monica Tiron
Section Managing Editor
Email: tiron@mdpi.com
Sustainability Journal
Concepción (Chile), April 26th, 2025
Dear Editor,
Please find here with the revised version of the manuscript “Toxic effects of liquors generated during the Kraft pulp production process on aerobic biomass and growth of Selenastrum capricornutum” by Constanza Hidd, Gabriela Morales, Naomi Monsalves, Gladys Vidal assigned as Manuscript ID: sustainability-3583136.
We want to thank the reviewers for carefully reading the manuscript. All the comments were attended and the paper was carefully checked according to the editorial suggestions.
The following comments indicate our response to all of the questions and notes indicated by the Reviewer #1. Please consider that unless otherwise expressed, the referenced lines correspond to the current numeration after the corrections were made.
REVIEWER # 1
The topic is relevant, and the experimental work is well conducted. Below, I offer a some suggestions aimed at improving the clarity, structure, and contextual grounding of your manuscript. I hope these comments help strengthen the scientific quality and overall impact of your work:
- Comment 1: The introduction provides adequate background on the Kraft pulping process and its environmental implications. However, it lacks empirical grounding regarding the frequency or documented occurrence of liquor spills, which form the central motivation of the study. The authors mention that accidental spills can occur and potentially affect biological treatment and receiving ecosystems, but no quantitative data, industrial incident reports, or references are provided to support this claim. Including statistics or regulatory information would strengthen the justification for the research. In my opinion, such spills are likely to be extremely rare in modern industrial settings, making this an arguably weak justification for the study’s relevance.
Furthermore, the introduction should include a clear and concise description of the chemical recovery cycle, particularly how the different liquors (white, green, black, and condensates) are generated and recycled within the process. These streams are not simply discharged to wastewater treatment systems, but rather are mostly recovered and reused in the Kraft process. Presenting this recovery cycle is essential for readers to understand the real role and fate of these liquors in industrial practice. As it stands, the text may lead readers to believe that these streams are routinely sent to treatment lagoons, which is inaccurate and may misrepresent the operational reality of Kraft pulp mills.
- Answer: Thank you very much for the comments from Reviewer 1. All of them are highly relevant to this study. This study was conducted because, although the modern industry is very well controlled, there are annual shutdowns every year to renew and adjust all the equipment and unit operations in a Kraft pulp mill. Every startup generates various accidental spills. One of them, very important for this type of sector, is the one discussed in this publication.
Furthermore, due to current environmental regulations, there is only one discharge point for liquid spills, and that is through the activated sludge system.
Hence, the importance of examining the toxicity of these spills on the biology of the aerobic bacteria in the activated sludge. Due to this the objective on this paper is to assess the toxicity of each liquor spill on the aerobic biomass of an activated sludge, using Selenastrum capricornutum as bioindicator of water quality.
The Kraft mill process and the generation of the different liquors (white, green, black, and condensates) are described between lines 36 and 45. Moreover, Figure 1 shows the process of Kraft mill.
- Comment 2: The methods section is comprehensive and well organized, with adequate detail for reproducibility. The use of both respirometric analysis and algal bioassays provides a robust dual approach to toxicity assessment. However, the number of replicates should be clearly specified, especially for control treatments. Including a simplified experimental diagram or flowchart could further enhance clarity for readers unfamiliar with these techniques.
- Answer: Many thanks for your comments on the publication methodology. The number of replicates was specified. The different sampled spill streams were exposed to different concentrations of aerobic biomass from the activated sludge using a respirometry system; this is explained in section 2.3 "Measurement via respirometry of aerobic biomass activity of an activated sludge system exposed to different COD concentrations of white, black, and green liquors and condensate." Furthermore, these same samples were evaluated for toxicity, as described in section "2.4. Determination of Selenastrum capricornutum growth and inhibition rates upon exposure to different COD concentrations of white, black, and green liquors and condensate."
- Comment 3: The results are presented in a logical order and are supported by well-constructed tables and figures. The interpretation of findings is generally sound, particularly the discussion on the role of pH and alkali compounds in toxicity. It is suggested, however, that the discussion be better structured by clearly separating the results related to aerobic biomass from those related to microalgal inhibition. Additionally, the authors could explore more deeply the mechanisms behind observed effects, especially the unexpected stimulation of S. capricornutum growth at low concentrations of black liquor. This observation deserves further elaboration, particularly in light of recent studies suggesting the potential valorization of black liquor as a carbon source for microbial growth.
- Answer: Thank you very much for your suggestion. In the revised manuscript, the results and discussion related to aerobic biomass and microalga inhibition have been organized into separate sections. 3.2 and 3.3, respectively. Additionally, the discussion has been expanded to explore possible mechanisms involved in the stimulation of S. capricornutum growth at low concentrations of black liquor and studies that demonstrate the potential valorization of black liquor as a carbon source (between lines 291 – 308).
- Comment 4: The figures are clear and relevant, though figure captions could be more descriptive, particularly in explaining symbols and treatments. In Figure 3, it would be helpful to improve the labeling of trends and ensure visual consistency between 48h and 96h results for easier interpretation.
Moreover, to ensure a more robust and reliable interpretation of the results, the use of appropriate statistical tools is recommended. The absence of such analyses may compromise the objectivity of the interpretation, particularly in ecotoxicological studies where biological variability is expected. Including measures such as analysis of variance (ANOVA), confidence intervals, and post-hoc tests would significantly enhance the scientific rigor of the study.
- Answer: Hence, the importance of examining the toxicity of these spills on the biology of the aerobic bacteria in the activated sludge. Due to this the objective on this paper is to assess the toxicity of each liquor spill on the aerobic biomass of an activated sludge, using Selenastrum capricornutum as bioindicator of water quality.
The Kraft cellulose process and the generation of the different liquors (white, green, black, and condensates) are described between lines 36 and 45. Moreover, Figure 1 shows the process of Kraft mill.
Regarding the statistical analysis, we appreciate the reviewer’s observation. We would like to clarify that all toxicity assays —including those conducted on aerobic biomass as well as those involving Selenastrum capricornutum— were carried out under controlled laboratory conditions, using a single experimental unit per concentration. This methodological decision was due to the limited availability of liquor samples and the exploratory nature of the study, which aimed to conduct an initial assessment of the toxic effects of each type of liquor. Despite this limitation, all experiments were conducted following standardized protocols (OECD guidelines), under strictly controlled conditions, and using calibrated instrumentation, which ensures the technical validity and reproducibility of the results. Therefore, the data presented corresponds to representative values for each tested condition.
- Comment 5: The reference list is generally composed of relevant and recent sources. However, the manuscript includes only 25 references, which is relatively limited considering the technical scope and environmental complexity of the study. The authors are strongly encouraged to expand the literature review to incorporate additional studies addressing effluent toxicity, ecological risk assessment, and biological treatment systems in pulp and paper industries. Furthermore, approximately 20% of the references are self-citations, primarily from the senior author. While these citations appear methodologically justified, the authors should ensure that the manuscript reflects broader engagement with independent and international literature to support its arguments and enhance the scientific impartiality of the discussion.
- Answer: The number of references increased, according to the suggestions of Reviewer 1. All of them were highlighted in yellow.
Yours sincerely,
Prof. Gladys Vidal
Engineering and Environmental Biotechnology Group
Environmental Science Faculty & Center EULA-Chile
Universidad de Concepción, Concepción, Chile.
E-mail: glvidal@udec.cl
ww.eula.cl/giba
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe work assesses the potential toxicity of a liquor spill to Selenastrum capricornutum, a microalga used as a water quality indicator. The work was carried out at a sufficiently professional level and has great practical significance.
There are the following minor remarks:
- The correct writing of formulas 2 and 3 is as follows:
Ir=(1-((OD-ODa)/ODb))∙100% (2)
K=(Ln(Nt/N0))/∆t. (3)
- pH 13.0 must be indicated everywhere in the article instead of 13, and not just in Table 2. The designation of the dimension of the rate of oxygen uptake should be given in the form of mgO2/L/h or mgO2/(LË‘h). Also, formula 1 implies that instead of hours there should be minutes. The authors should figure this out.
- Table 1: In the first column it is desirable to give the full name of the parameters, and their designations should then be given in brackets. In the footnote it is necessary to indicate the number of measurements that allowed obtaining the average values ​​and SD. The color was determined in g/L, is this correct?
- Table 2: Instead of the value 141,350±2,275 mg/L it is better to give 141.4±2.3. That is, the value of COD is given in g/L. Rounding has also been performed since averages cannot contain 5 significant digits and standard deviations cannot contain 4.
- Table 3: There is no need to give 5 significant digits (2,854.5), 4 digits are enough.
- In conclusion, the authors present the main numerical data they obtained. They also need to formulate in a few sentences what significance their research had for Kraft pulp industry and ecology.
Author Response
Ms. Monica Tiron
Section Managing Editor
Email: tiron@mdpi.com
Sustainability Journal
Concepción (Chile), April 26th, 2025
Dear Editor,
Please find here with the revised version of the manuscript “Toxic effects of liquors generated during the Kraft pulp production process on aerobic biomass and growth of Selenastrum capricornutum” by Constanza Hidd, Gabriela Morales, Naomi Monsalves, Gladys Vidal assigned as Manuscript ID: sustainability-3583136.
We want to thank the reviewers for carefully reading the manuscript. All the comments were attended and the paper was carefully checked according to the editorial suggestions.
The following comments indicate our response to all of the questions and notes indicated by the Reviewer #2. Please consider that unless otherwise expressed, the referenced lines correspond to the current numeration after the corrections were made.
REVIEWER # 2
The work assesses the potential toxicity of a liquor spill to Selenastrum capricornutum, a microalga used as a water quality indicator. The work was carried out at a sufficiently professional level and has great practical significance.
- Comment 1:
There are the following minor remarks:
- The correct writing of formulas 2 and 3 is as follows:
Ir=(1-((OD-ODa)/ODb))∙100% (2)
K=(Ln(Nt/N0))/∆t. (3)
- Answer: The correction was made according to reviewer 2, see equations 2 and 3, highlighted in yellow.
- Comment 2: - pH 13.0 must be indicated everywhere in the article instead of 13, and not just in Table 2. The designation of the dimension of the rate of oxygen uptake should be given in the form of mgO2/L/h or mgO2/(LË‘h). Also, formula 1 implies that instead of hours there should be minutes. The authors should figure this out.
- Answer: The pH = 13.0 notation in the text has been improved. All changes have been highlighted in yellow, see lines 19-21.
- Comment 3: Table 1: In the first column it is desirable to give the full name of the parameters, and their designations should then be given in brackets. In the footnote it is necessary to indicate the number of measurements that allowed obtaining the average values and SD. The color was determined in g/L, is this correct?
- Answer: The full name of each parameter is described in the table below. This has been done due to space limitations in Table 1. In the footnote of Table 1 is indicate the number of measurements. The color was determined in Abs, this is absorption units 1x, 1cm.
- Comment 4: Table 2: Instead of the value 141,350±2,275 mg/L it is better to give 141.4±2.3. That is, the value of COD is given in g/L. Rounding has also been performed since averages cannot contain 5 significant digits and standard deviations cannot contain 4.
Table 3: There is no need to give 5 significant digits (2,854.5), 4 digits are enough.
- Answer: Because this work is one of the few that addresses spills in the kraft pulp industry and assesses toxicity, it is important to consider all the figures to generate basic information for other ecotoxicology researchers in this sector. As the Reviewer knows, there is no information on this type of research in this area. Furthermore, all kraft pulp industries have closed in developed countries, and the opening of new pulp industries has been encouraged in underdeveloped regions (e.g., Latin America, Africa, etc.) with low environmental regulations.
- Comment 5: In conclusion, the authors present the main numerical data they obtained. They also need to formulate in a few sentences what significance their research had for Kraft pulp industry and ecology.
- Answer: In the conclusion sector the following sentence was added: “The conclusions of this publication are highly relevant, as there is very little information about the physicochemical and toxicity of the e black, white, green and condensate liquors coming from Kraft processes. If a liquor spill occurs at a Kraft plant, the information from this study makes it possible to calculate how much liquor can be fed to an activated sludge system so that it does not lose the biological activity of aerobic bacteria.”
Yours sincerely,
Prof. Gladys Vidal
Engineering and Environmental Biotechnology Group
Environmental Science Faculty & Center EULA-Chile
Universidad de Concepción, Concepción, Chile.
E-mail: glvidal@udec.cl
ww.eula.cl/giba
Author Response File: 
Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsIn this study, the toxic effects of liquors generated from the production process of Kraft pulp on aerobic biomass of activated sludge were determined by using the growth of Selenastrum capricornutum using a bioindicator of water quality. The content of this study is interesting and useful for the treatment of the liquors from Kraft pulp production.
Here are some suggestions for the authors to improve the content of this study:
Title: Some alternative titles are suggested, such as "Toxic effects of liquors generated from different production stages of Kraft pulp on ecosystems".
Abstract: Please revise lines 19-20. It is very confusing. Please give a short conclusion at the end of the abstract.
Materials and Methods
Please add a scheme to illustrate the production of each type of spill – white liquor, green liquor, black liquor, and condensate during the production of Kraft pulp.
Statistical analysis should be introduced at the end of methods.
Results and discussion:
Data in the tables should be expressed as mean ± standard deviation of at least three replicates.
However, in the tables, there is only one data for each index.
Table 3: Please explain why EC20 is used here.
At the end of results, it is suggested to thoroughly discuss the relationship between the physicochemical characteristics of liquors and their toxic effects.
Conclusions:
This section should be shortened by retaining the most important findings and give some perspectives for future studies.
References:
Many references are not up-date.
Author Response
Ms. Monica Tiron
Section Managing Editor
Email: tiron@mdpi.com
Sustainability Journal
Concepción (Chile), April 26th, 2025
Dear Editor,
Please find here with the revised version of the manuscript “Toxic effects of liquors generated during the Kraft pulp production process on aerobic biomass and growth of Selenastrum capricornutum” by Constanza Hidd, Gabriela Morales, Naomi Monsalves, Gladys Vidal assigned as Manuscript ID: sustainability-3583136.
We want to thank the reviewers for carefully reading the manuscript. All the comments were attended and the paper was carefully checked according to the editorial suggestions.
The following comments indicate our response to all of the questions and notes indicated by the Reviewer #3. Please consider that unless otherwise expressed, the referenced lines correspond to the current numeration after the corrections were made.
REVIEWER # 3
In this study, the toxic effects of liquors generated from the production process of Kraft pulp on aerobic biomass of activated sludge were determined by using the growth of Selenastrum capricornutum using a bioindicator of water quality. The content of this study is interesting and useful for the treatment of the liquors from Kraft pulp production.
Here are some suggestions for the authors to improve the content of this study:
- Comment 1: Title: Some alternative titles are suggested, such as "Toxic effects of liquors generated from different production stages of Kraft pulp on ecosystems".
- Answer: The authors prefer to keep the title more general. One of the aims of this publication is to understand how to feed an activated sludge system with liquor from the kraft pulp process when a spill has occurred within the plant (i.e., from a plant startup; this occurs annually in plants). In this case, all the knowledge of activated sludge toxicity to aerobic bacteria will be utilized, but the discharges would not impact the aquatic ecosystem.
- Comment 2: Abstract: Please revise lines 19-20. It is very confusing. Please give a short conclusion at the end of the abstract.
- Answer: The writing of lines 19-20 was improved. A short conclusion was included at the end of the abstract: “The information from this study makes it possible to calculate how much liquor can be fed to an activated sludge system, keeping it optimized to eliminate liquor discharges generated within the Kraft mill's processing units”.
- Comment 3: Materials and Methods. Please add a scheme to illustrate the production of each type of spill – white liquor, green liquor, black liquor, and condensate during the production of Kraft pulp.
Statistical analysis should be introduced at the end of methods.
- Answer: Now in Figure 1 was added a diagram of the Kraft mill process, with the production of the liquors.
- Comment 4: Results and discussion: Data in the tables should be expressed as mean ± standard deviation of at least three replicates.
However, in the tables, there is only one data for each index.
- Answer: Table 1 and Table 2 show the values as mean ± standard.
- Comment 5: Table 3: Please explain why EC20 is used here.
At the end of results, it is suggested to thoroughly discuss the relationship between the physicochemical characteristics of liquors and their toxic effects.
- Answer: The following paragraph was added “The results obtained from EC50 and EC20 from the exposure of the different liquors on aerobic biomass from an activated sludge system do not have a direct correction with the characterization of COD, TOC, Lignosulfonic acids, Lignin or Aromatic compounds discussed in Table 2.»
- Comment 6: Conclusions: This section should be shortened by retaining the most important findings and give some perspectives for future studies.
- Answer: The writing of the conclusions was improved.
- Comment 7: References: Many references are not up-date.
- Answer: The references in this paper were included, prioritizing the information they provide for discussion of the publication. This review included other more up-to-date references highlighted in yellow.
Yours sincerely,
Prof. Gladys Vidal
Engineering and Environmental Biotechnology Group
Environmental Science Faculty & Center EULA-Chile
Universidad de Concepción, Concepción, Chile.
E-mail: glvidal@udec.cl
ww.eula.cl/giba
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThe article shows the difference in the effect of different liquors from Kraft process on active sludge and indicator algae. Following improvements are required:
- Introduction, first paragraph. First paragraph contains description of Kraft process. It is better to include flow sheet diagram of the process demonstrating main flows and formation of the liquors formed (white, black, green and condensate), which were used in the study.
- Line 54. “…in a Kraft pulp mill there may be accidental spills of liquors”, which negatively affect AS. Add short explanation. Is AS used in paper mills for waste treatment? Which flows from paper mills are treated using AS? Are these wastes undergoing to pretreatment before treatment with AS?
- Line 95. total volatile solids (VSS) – or Volatile Suspended Solids?
- Line 137. 104 cells·- 10^4 cells?
- Line 139. % - vol %?
- Line 213. The toxicity of the liquors to the aerobic biomass could be related to pH… Did you control the pH of the media with different content of the liquors?
- Figures. Enlarge all figures and use colored lines in the diagrams.
- Line 139. % - vol % and results shown in Figure 3 and subsection 3.3. In the Methods, % of liquor content in the media are shown. In the subsection 3.3, contents of the liquors are shown as mgCOD/L. Could you show the correspondence of % to mgCOD/L?
- Did you control the pH of the media with different content of the liquors?
- Conclusions. Based on the difference of the effects of different liquors on the AS and S. capricornutum, could you propose possible different pathways for the treatment of different liquors?
Author Response
Ms. Monica Tiron
Section Managing Editor
Email: tiron@mdpi.com
Sustainability Journal
Concepción (Chile), April 26th, 2025
Dear Editor,
Please find here with the revised version of the manuscript “Toxic effects of liquors generated during the Kraft pulp production process on aerobic biomass and growth of Selenastrum capricornutum” by Constanza Hidd, Gabriela Morales, Naomi Monsalves, Gladys Vidal assigned as Manuscript ID: sustainability-3583136.
We want to thank the reviewers for carefully reading the manuscript. All the comments were attended and the paper was carefully checked according to the editorial suggestions.
The following comments indicate our response to all of the questions and notes indicated by the Reviewer # 4. Please consider that unless otherwise expressed, the referenced lines correspond to the current numeration after the corrections were made.
REVIEWER # 4
The article shows the difference in the effect of different liquors from Kraft process on active sludge and indicator algae. Following improvements are required:
- Comment 1: Introduction, first paragraph. First paragraph contains description of Kraft process. It is better to include flow sheet diagram of the process demonstrating main flows and formation of the liquors formed (white, black, green and condensate), which were used in the study.
- Answer: A new Figure 1 with a diagram of Kraft mill process was added.
- Comment 2: Line 54. “…in a Kraft pulp mill there may be accidental spills of liquors”, which negatively affect AS. Add short explanation. Is AS used in paper mills for waste treatment? Which flows from paper mills are treated using AS? Are these wastes undergoing to pretreatment before treatment with AS?
- Answer: Kraft pulp mill is not a paper mill. In the lines 55-57 It was adding an explanation about primary treatment and AS. Also, see the Figure 1.
- Comment 3: Line 95. total volatile solids (VSS) – or Volatile Suspended Solids?
- Answer: Now in line 95: volatile suspended solids (VSS).
- Comment 4: Line 137. 104 cells·- 10^4 cells?
- Answer: Now in line 137: 104 cells.
- Comment 5: Line 139. % - vol %?
- Answer: Now in the sentence was added: % v/v.
- Comment 6: Line 213. The toxicity of the liquors to the aerobic biomass could be related to pH… Did you control the pH of the media with different content of the liquors?
- Answer: The pH was controlled in the respirometry assay agree with the methodology.
- Comment 7: Figures. Enlarge all figures and use colored lines in the diagrams.
- Answer: All figures were enlarged.
- Comment 8: Line 139. % - vol % and results shown in Figure 3 and subsection 3.3. In the Methods, % of liquor content in the media are shown. In the subsection 3.3, contents of the liquors are shown as mgCOD/L. Could you show the correspondence of % to mgCOD/L?
- Answer: The results were described in mgCOD/L because it is easier to visualize concentrations of the different liquors. For example, in the following paragraph “Regarding Selenastrum capricornutum exposure to black liquor, different behavior is ob-served at 48 h and 96 h. At 48 h of exposure, microalga growth inhibition ranges from 3.1% at 0.04 mgCOD/L of black liquor”. In this paragraph the 0.04 mgCOD/L is equivalent to 0,0000283% v/v.
- Comment 9: Did you control the pH of the media with different content of the liquors?
- Answer: Yes, the pH is controlled in the different assays, agree with methodology recommended by the OECD [18].
- Comment 10: Conclusions. Based on the difference of the effects of different liquors on the AS and S. capricornutum, could you propose possible different pathways for the treatment of different liquors?
- Answer: At the end of the conclusion section a new paragraph was added.
Yours sincerely,
Prof. Gladys Vidal
Engineering and Environmental Biotechnology Group
Environmental Science Faculty & Center EULA-Chile
Universidad de Concepción, Concepción, Chile.
E-mail: glvidal@udec.cl
ww.eula.cl/giba
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsDear authors,
Thank you very much for the changes and the argumentative counter-responses.
In my opinion, the manuscript can be approved.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe revised manuscript is fine and can be accepted.
Reviewer 4 Report
Comments and Suggestions for AuthorsAuthors have improved the manuscript. Therefore, it may be accepted.
