Review Reports - Use of Natural Sorbents in the Processes of Removing Biogenic Compounds from the Aquatic Environment

Round 1

Reviewer 1 Report

Review report for paper#1682600 “Use of natural sorbents in the processes of removing biogenic 2 compounds from the aquatic environment”.

In this paper the authors evaluated the removal efficiency of N and P from three types of water by a natural adsorbent, i.e. Opoka Rock. The authors conducted column test and batch adsorption study for two types of granular forms of the adsorbent.

Overall, the quality of the manuscript is average and raised following concerns, which does not support the publication of the manuscript at its current form.

The need for treating these three types of water is not clear in the Introduction section. Any particular reason for selecting the source water?
There is no or very limited information reported on the column and batch experimentation. Also, no standard procedure was followed, which can be supported by the references.
The weakest part of the manuscript is Discussion section. There is no discussion on the results from the experiments conducted in the study. Only presenting the removal efficiency is not sufficient. It is not clear why the removal occurred or not occurred. It is not discussed at all, why grain size affecting the removal efficiency of N and P.
In the discussion, the review of other researches presented only, which does not verify the acceptance of the results obtained from the current experimentation. Comparing the percentage removal is vague if the pollutant concentration of source water is not similar to that reported in the respective literature.
The authors should fully concentrate on the discussion of mechanisms behind the difference in adsorption by the said adsorbent, which can be done by using the experimental data to produce common Adsorption Isotherms.

More comments are made in the appended manuscript.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer #1

Sustainability

Subject: Submission of manuscript for evaluation after Review

Corresponding Author: Dr Marzena Smol

Email: smol@meeri.pl; marzena.smol@wp.pl

Dear Reviewer #1,

I am enclosing here with a manuscript entitled “Use of natural sorbents in the processes of removing biogenic compounds from the aquatic environment” submitted to “Sustainability” for possible evaluation after your review. With the submission of this manuscript I would like to undertake that the above mentioned manuscript has been corrected according to Your (red) and other Reviewers comments.

Reviewer comment: In this paper the authors evaluated the removal efficiency of N and P from three types of water by a natural adsorbent, i.e. Opoka Rock. The authors conducted column test and batch adsorption study for two types of granular forms of the adsorbent. Overall, the quality of the manuscript is average and raised following concerns, which does not support the publication of the manuscript at its current form. The need for treating these three types of water is not clear in the Introduction section. Any particular reason for selecting the source water?

Answer: Thank you for your all valuable comments and suggestions to improve the paper. Water solutions (W1 - tap water from the water supply system located in the region of Silesia) was selected as a control test, constituting standard tap water under natural conditions. of Silesia, W3 - water from a garden pond located in the region of Silesia) were selected as the most common small water reservoirs in this part of the country.

Reviewer comment: There is no or very limited information reported on the column and batch experimentation. Also, no standard procedure was followed, which can be supported by the references.

Answer: : Thank you for the suggestion. The column experiment was described in previous point.

The first system - column analysis consisted in preparing a series of columns filled with the 2 types of tested materials. Then, three types of water (W1, W2, W3) were passed through the prepared filtration systems. Eluate obtained after filtration was subjected to chemical characterization. Each filtration procedure was performed three times for each tested sample. Columns used during the experiment have following dimensions: H=1020 mm, r=25 mm. The effective volume of the individual column was equal to 2000 cm³. To each column, 1000g of tested fraction of opoka rock was introduced. Due to the differences of the material properties each tested fraction showed different water retention time, which is presented below. This parameter was also slightly differs along the different water samples types. However, in this case differences were in the range bellow 0,01%. Retention time for the columns filled with material A was equal to 1,42 l/min +/- 0,0, and retention time for the columns filled with material B was equal to 1,59 l/min +/- 0,03. The amount of water passed through filtration columns was equal to 2 l per the trial. In result overall amount of filtrated water during the analysis was equal to 6 l per the type of sample. After filtration the eluate was collected and subjected to the further analyses.

The second system - the batch test consisted in the quantitative introduction of the tested material into glass containers with a tested water samples. The batch experiment was conducted in 1000dm³ glass containers. To each container 1000 cm³ of water subjected to study was introduced. Next to each prepared sample, 10g of mineral material solution was introduced, in accordance to the similar order as in case of column trials. After that, prepared mixtures were shacked (25 rpm) for the 1h. In the final stage, samples were subjected to the stabilization for the 24h. Then, the solid fraction was separated from the liquid fraction by filtration using membrane filters. After the process, the filtrate was sent for quantitative analysis - determination of the concentration of N (in the form of NO₃⁻, NH₄₊ ), P (PO₄³⁻) and TOC.

Reviewer comment: The weakest part of the manuscript is Discussion section. There is no discussion on the results from the experiments conducted in the study. Only presenting the removal efficiency is not sufficient. It is not clear why the removal occurred or not occurred. It is not discussed at all, why grain size affecting the removal efficiency of N and P. In the discussion, the review of other researches presented only, which does not verify the acceptance of the results obtained from the current experimentation. Comparing the percentage removal is vague if the pollutant concentration of source water is not similar to that reported in the respective literature. The authors should fully concentrate on the discussion of mechanisms behind the difference in adsorption by the said adsorbent, which can be done by using the experimental data to produce common Adsorption Isotherms.

Answer: This part of the paper was extended, according to your suggestions. The Discussion section presents Typical stages in the discussion: summarizing the results, discussing whether results are expected or unexpected, comparing these results to previous work. The purpose of the experiment was to identify the effectiveness of both types of sorbent, Table 4 shows the effectiveness of the removal of selected elements. In the current paper, the analysed opoka rock comes from deposits in the Silesia region in Poland. So far, this material (coming from this source) has not been analysed in terms of its possible use in water and sewage treatment technology. The results of preliminary studies presented in this paper confirm that this material can be used for the treatment of water reservoirs, and also as sorbent in municipal sewage treatment processes. Comparing this analysed sorbent to other materials in the discussion, this material has not been further processed. In the subsequent stages of the research, planning is calcining and obtaining a sorbent that will be transferred for further analysis in terms of the effectiveness of removing biogenic materials from aqueous solutions. Further research on this material will continue. Solution is limited by the material costs. In many cases, water reservoirs, that are affected by the eutrophication issues are large. This fact combined with the relatively high cost of Opoka rock (average price 85 – 120 euro/Mg) may be considered a huge limitation. Many lakes and rivers are also under public jurisdiction which contributes to the complicated legal procedure associated with the potential application of the presented method. The other important limitation is associated with the form of the material that is described in the current paper. The small particle size of the tested fractions may have a temporal effect on the water clarity. Solution after direct introduction to the water forms a semi-soluble mixture that is present on the reservoir surface for 2-4 days. In some case, such an effect may have a negative impact on some biotic ecosystems. However, this aspect of the study is currently under closer evaluation.

Thank you for your consideration. We hope you will accept the article for publication.

D.Sc. Marzena Smol & Dr. Dariusz Włóka

Reviewer 2 Report

Thank you for the opportunity to review this paper that deals with the use of natural sorbents in the processes of removing biogenic compounds from the aquatic environment. The paper presents an interesting topic of worldwide interest. However, in my opinion, the manuscript cannot be considered for publication at its present state. Some improvments are needed.

General Comments

The English of the paper should be improved.

There are many typographic and spelling errors throughout the manuscript. Please, revise the paper carefully.

The authors are suggested to rewrite the introduction (very long) and to present, in a clear way, their research problem and the originality of the methodology used to get to the findings of their work. Some pargarphs arent needed (see sepecif comments)

Specific comments:

Line 21: Please replace "nitrite nitrogen" by "nitrate-nitrogen"

Line 23: Delete dot at the end of this sentence "The use of materials of natural origin in industrial applications is a recommended direction, part of green transition.."

Line 55-70: Please delete or condense this paragraph.

In the figure 1, please replace "Stageep 2 " by Stage 2".

Figure 2 and 3: There is alot of overlaying text. Please only keep what needed.

In the Table 3 the authors are suggested to put the chemical composition of the aquatic solutions after culumn test. The table 4 present only the removal effeciency of used tests.

Troughout the text, the author confused between nitrite nitrogen (NO3-) and nitrate nitrogen (NO3-).

I have some questions to the authors:

1) The use of a natural mineral of opoka rock can be classified as a nature based solutions for water treatment?

2) What are the limitations of this solution and used approach?

Author Response

Response to Reviewer #2

Sustainability

Subject: Submission of manuscript for evaluation after Review

Corresponding Author: Dr Marzena Smol

Email: smol@meeri.pl; marzena.smol@wp.pl

Dear Reviewer #2,

We are enclosing here with a manuscript entitled “Use of natural sorbents in the processes of removing biogenic compounds from the aquatic environment” submitted to “Sustainability” for possible evaluation after your review. With the submission of this manuscript I would like to undertake that the above mentioned manuscript has been corrected according to Your (red) and other Reviewers comments.

Reviewer comment: The English of the paper should be improved. There are many typographic and spelling errors throughout the manuscript. Please, revise the paper carefully.

Answer: Thank you for your comments. The paper was revised step-by-step to correct the typographic and spelling errors.

Reviewer comment: Line 21: Please replace "nitrite nitrogen" by "nitrate-nitrogen"

Answer: Thank you for your comment. It was verified and corrected in all text, according to your suggestion.

Reviewer comment: Line 23: Delete dot at the end of this sentence "The use of materials of natural origin in industrial applications is a recommended direction, part of green transition.."

Answer: Thank you. It was corrected according to your comment.

Reviewer comment: Line 55-70: Please delete or condense this paragraph.

Answer: Thank you for your comment. This part was removed from text, according to your and #Reviewer1 comment.

Reviewer comment: In the figure 1, please replace "Stageep 2 " by Stage 2".

Answer: Thank you. It was corrected according to your comment.

Reviewer comment: Figure 2 and 3: There is a lot of overlaying text. Please only keep what needed.

Answer: Thank you. It was corrected according to your comment.

Reviewer comment: In the Table 3 the authors are suggested to put the chemical composition of the aquatic solutions after culumn test. The table 4 present only the removal effeciency of used tests.

Answer: The purpose of the experiment was to identify the effectiveness of both types of sorbent, therefore Table 3 indicates the value of indicators for the 'raw' analytical medium, and Table 4 shows the effectiveness of the removal of selected elements. Thank you for your comment.

Reviewer comment: Troughout the text, the author confused between nitrite nitrogen (NO3-) and nitrate nitrogen (NO3-).

Answer: Thank you for this comment. It was verified in the text. The ammonium nitrogen (NH4 +) and nitrate nitrogen (NO3-) were analysed.

Reviewer comment: 1) The use of a natural mineral of opoka rock can be classified as a nature based solutions for water treatment?

Answer: According to United Nations definition “Nature-based Solutions (NbS) are actions to protect, sustainably manage, and restore natural or modified ecosystems, that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits”. In this context, the opoka rock can be indicated as a nature based solutions for water treatment.

Reviewer comment: 2) What are the limitations of this solution and used approach?

Answer: Solution is limited by the material costs. In many cases, water reservoirs, that are affected by the eutrophication issues are large. This fact combined with the relatively high cost of Opoka rock (average price 85 – 120 euro/Mg) may be considered a huge limitation. Many lakes and rivers are also under public jurisdiction which contributes to the complicated legal procedure associated with the potential application of the presented method.

The second important limitation is associated with the form of the material that is described in the current paper. The small particle size of the tested fractions may have a temporal effect on the water clarity. Solution after direct introduction to the water forms a semi-soluble mixture that is present on the reservoir surface for 2-4 days. In some case, such an effect may have a negative impact on some biotic ecosystems. However, this aspect of the study is currently under closer evaluation. Therefore no precise conclusion in this matter can be provided at this moment.

Thank you for your consideration. We hope you will accept the article for publication.

D.Sc. Marzena Smol & Dr. Dariusz Włóka

Reviewer 3 Report

I think that the possibility of using natural materials, by-products or waste to reduce water pollution is a very interesting line of research.

I found the article very interesting, showing a line of research that can have a great practical application.

I thought it was a very good idea to include a diagram of the stages of the work (figure 1).

But I have some doubts, questions, suggestions.

What method of analysis of the pH of the material have you used? (material:water, agitation time,...). I don't know the norm for testing reactivity (PN-EN 13971), so I don't know if the pH method is included in it. If the method for analyse pH is not included in this norm, you should add the method used for analyse pH.

I think that you should expand the information that appears on lines 182-185. What kind of columns have you used? What was the retention time of the water in the columns? I think that you should provide any kind of information that would allow others to reproduce your experiment.

There are some mistakes in the text that you should correct:

Lines 21, 286, 292-293, 404: You should change “nitrite nitrogen” by “nitrate nitrogen”

Line 22: You should change “green transition.. The” by “green transition. The”

Figure 1: You should change “Evaluattion” by “Evaluation”

Line 180: You should change “water(Spectrophotometric” by “water (Spectrophotometric”

Line 207: “nutrient removal” appears twice

Is coarse-grained material or sorbent between 2-4 mm or 4-8 mm? 4-8 mm appears in lines 221, 264, 277, 282

Line 229: You should change “materilas” by “materials”

Line 234: You should change “a fish pond” by “a garden pond”

Line 244: Did you analyse the nitrites? Or “The concentrations of nitrates and nitrites” is a mistake and should you change by “The concentrations of ammonia and nitrates”?

Line 246: You should change “4.4.” by “4.4”

Line 250: You should change “41.7” by “27.5”

Line 286: You should change “84% of nitrate nitrogen” by “84% of ammonia nitrogen”

Line 342: You should change “wss” by “was”

Line 405: You should change “analysed” by “analysed”

Line 432: You should change “2022;” by “2022.”

Line 446: You should change “2022;” by “2022.”

Line 449: You should change “2017;” by “2017.”

You should check if all the subscripts and superscripts of the chemical formulas in the text are correct. There are several mistakes.

Author Response

Response to Reviewer #3

Sustainability

Subject: Submission of manuscript for evaluation after Review

Corresponding Author: Dr Marzena Smol

Email: smol@meeri.pl; marzena.smol@wp.pl

Dear Reviewer #3,

Reviewer comment: I think that the possibility of using natural materials, by-products or waste to reduce water pollution is a very interesting line of research. I found the article very interesting, showing a line of research that can have a great practical application.

Answer: Thank you for your positive comments.

Reviewer comment: I thought it was a very good idea to include a diagram of the stages of the work (figure 1).

Answer: Thank you for your positive comments.

Reviewer comment: What method of analysis of the pH of the material have you used? (material:water, agitation time,...). I don't know the norm for testing reactivity (PN-EN 13971), so I don't know if the pH method is included in it. If the method for analyse pH is not included in this norm, you should add the method used for analyse pH.

Answer: Thank You for the comment. The provided norm is based on pH analysis and methodology described in the Norm PN-EN 1397 form includes whole procedure step by step. Norm is available in universal version EN.

Reviewer comment: I think that you should expand the information that appears on lines 182-185. What kind of columns have you used? What was the retention time of the water in the columns? I think that you should provide any kind of information that would allow others to reproduce your experiment.

Answer: Thank you for the useful suggestion. Columns used during the experiment have following dimensions: H=1020 mm, r=25 mm. The effective volume of the individual column was equal to 2000 cm3. To each column a 1000g of tested fraction of opoka rock was introduced. Due to the differences of the material properties each tested fraction showed different water retention time, which is presented below. This parameter was also slightly differs along the different water samples types. However, in this case differences were in the range bellow 0,01%.

Retention time for the columns filled with material A was equal to 1,42 l/min +/- 0,02
Retention time for the columns filled with material B was equal to 1,59 l/min +/- 0,03

The amount of water passed through filtration columns was equal to 2 l per the trial. In result overall amount of filtrated water during the analysis was equal to 6 l per the type of sample. After filtration the eluate was collected and subjected to the further analyses.

Reviewer comment: Lines 21, 286, 292-293, 404: You should change “nitrite nitrogen” by “nitrate nitrogen”

Answer: Thank you for this valuable comments. We have verified all text and corrected this grammatical error.

Reviewer comment: Line 22: You should change “green transition.. The” by “green transition. The”

Answer: Thank you. It was corrected according to your comment.

Reviewer comment: Figure 1: You should change “Evaluattion” by “Evaluation”

Answer: Thank you. It was corrected according to your comment.

Reviewer comment: Line 180: You should change “water(Spectrophotometric” by “water (Spectrophotometric”

Answer: Thank you. It was corrected according to your comment.

Reviewer comment: Line 207: “nutrient removal” appears twice

Answer: Thank you. It was removed according to your comment.

Reviewer comment: Is coarse-grained material or sorbent between 2-4 mm or 4-8 mm? 4-8 mm appears in lines 221, 264, 277, 282

Answer: It was sorbent. It was verified in the text.

Reviewer comment: Line 229: You should change “materilas” by “materials”