Quality Assessment of Sludge from Filter Backwash Water in Swimming Pool Facilities

Round 1

Reviewer 1 Report

Conclusions should be corrected, they are too detailed.

Author Response

Dear Reviewer,

thank you for taking the time to review the manuscript.

Point 1: Conclusions should be corrected, they are too detailed.

Response 1: In accordance with the comments, the conclusions have been redacted and shortened.

In addition, the text has been subjected to linguistic correction. I am attaching the manuscript after the changes.

Yours faithfully,

Edyta Łaskawiec

 

Author Response File: Author Response.docx

Reviewer 2 Report

The article, after a thorough shortening, can only be publicized as a Short note. It lacks the analysis of toxic substances content, pH and pathogenic microorganisms to support the discussion and conclusions.  The studies should be extended by samples from different periods of the swimming pools’ usage to support the considerations in lines 366-371.

L103 and L115 – Specify the exact dosage of the coagulants used for the precipitation process.

L127 – Provide information on the glass fibrer filters used; What volume of water has been filtered?

L201 – What physicochemical analyzes were performed?

L201-203: Change: The washings collected from Circuit 1 had the TSS content ranging between 251 ± 23 mg/L (Sample 1)  and 128 ± 4 mg/L (Sample 3) (Figure 1 (a) – (d)).

L226-228: Change: The TSS content ranged from 489 ± 15 (Sample 1) to 228 ± 15 mg/L (Sample 4) (Figure 1 (e) – (h)).

L231 – Probably Figure 1., not Figure 2.?

Figure 1 – Are the Y axes correctly described?

L415-468 – Informations unnecessary in Discussion section (in general, they do not have significant connection to the studies carried out – e.g. there are no metal content tests), they can be partially moved to the Introduction section.

Conclusions ought to be redrafted and shortened

Author Response

Dear Reviewer,

thank you for taking the time to review my manuscript. The article has been revised taking into account the reviewers' suggestions. The text has also been linguistically corrected again. Below are the answers and detailed comments, and the revised manuscript is attached.

Yours faithfully,

Edyta Łaskawiec

Point 1: The article, after a thorough shortening, can only be publicized as a Short note. It lacks the analysis of toxic substances content, pH and pathogenic microorganisms to support the discussion and conclusions. The studies should be extended by samples from different periods of the swimming pools’ usage to support the considerations in lines 366-371.

Response 1: The presented studies are new and preliminary analyses, no doubt in the future they will require extension and further analyses. Especially in the range you propose. The studies conducted so far on the possibilities of using swimming pool washings have focused primarily on water recovery, and such analyzes are available (also my co-author). A supplement is attached to this manuscript that summarizes the results of 4 independent samplings for each of the circuits.

Point 2: L103 and L115 – Specify the exact dosage of the coagulants used for the precipitation process.

Response 2: Thank you, this may also be valuable information for the reader. Usually, in the swimming pool technique, the dose of the commercial product - coagulant, depending on the pool load, is 0.2-0.6 g (for pre-hydrolyzed) or 0.4-1.2 g for each m³ of circulating water. Therefore, the text has been supplemented with a more detailed explanation:

From L116 ‘’ Usually, in pool technology, the coagulant dose is selected based on the estimated load of the facility with bathers, circulation efficiency, and previous service experience. The dose may vary from hour to hour, resulting from manual adjustment. However, for the tested circuits, it is possible to determine the average dosing dose based on the efficiency of the circuit - the volume of treated water per unit of time. The capacity of Circuit 1 was 1500 m³/h, and the dosed average dose of aluminum sulfate (8.5%) was 0.75 g/m³. The capacity of Circuit 2 during the sludge sampling period was 4000 m³/h, and the dosed average dose of aluminum hydroxychloride (10%) was 0.54 g/m³.’’

Point 3: L127 – Provide information on the glass fibrer filters used; What volume of water has been filtered?

Response 3: TSS Glass Fiber Filter, Pore Size 1.5 µm, Diameter 47 mm (Hach), the sample volume was increased to 200 ml, originally the Method recommended 100 ml of the sample. Supplemented information in the text: L136 ‘’(…) through glass fiber filters (made by Hach with pore size 1.5 µm, sample volume 200 mL) [19].’’

Point 3: L201-203: Change: The washings collected from Circuit 1 had the TSS content ranging between 251 ± 23 mg/L (Sample 1)  and 128 ± 4 mg/L (Sample 3) (Figure 1 (a) – (d)).

Response 3: Thank you, has been changed.

Point 4: L231 – Probably Figure 1., not Figure 2.?

Response 4: Thank you, has been changed.

Point 5: Informations unnecessary in Discussion section (in general, they do not have significant connection to the studies carried out – e.g. there are no metal content tests), they can be partially moved to the Introduction section.

Response 5: The discussion of the results summarizes the results obtained in the context of the theory on which I based my research. I especially wanted to emphasize the importance of the coagulation process in a swimming pool facility, and how the type of coagulant can affect the characteristics of the sludge produced. Post-coagulation sludge from swimming pool facilities have not been characterized so far, hence the desire to refer to a wide research field. Including the desire to highlight the presence of heavy metals as a factor potentially preventing the reuse of sludge. Phytotoxicity assessment tests can contribute in particular to the environmental assessment of the impact of sludges.

Point 6: Conclusions ought to be redrafted and shortened.

Response 6: Thank you. In accordance with the comments, the conclusions have been redacted and shortened.

In addition, a block diagram of the research process appeared in the text. And in additional materials, a table with selected physicochemical parameters of washings.

 

Author Response File: Author Response.docx

Reviewer 3 Report

 

The topic of the article is interesting and stimulating. Here you can find my comments:

 

OVERALL: - Please, enlarge and re-arrange font sizes to guide the reader properly in all sections. All figures must be composed of HD images. It is mandatory to improve the scientific quality of the whole manuscript.

-      Please, pay attention to the JOURNAL TEMPLATE in all sections, including tables, references, captions, units, equations, and Figures.

 

-      Please, insert all corrected axes and labels, in order to guide the reader properly in understanding the whole manuscript. In addition, please improve the contrast between colours.

INTRODUCTION: Please, consider in the scientific background of your study the importance of advanced data analysis in the management and monitoring of natural resources broadly speaking (i.e.,

 

Khan, M.A., Sharma, N., Lama, G.F.C., Hasan, M., Garg, R., Busico, G., Alharbi, R.S. 2022. Three-Dimensional Hole Size (3DHS) Approach for Water Flow Turbulence Analysis over Emerging Sand Bars: Flume-Scale Experiments. Water 14, 1889. https://doi.org/10.3390/w14121889.

 

Box, W., Järvelä, J.,Västilä, K. 2021. Flow resistance of floodplain vegetation mixtures for modelling river flows. Journal of Hydrology, 601, 126593.

 

Lama, G.F.C., Errico, A., Francalanci, S., Solari, L., Chirico, G.B., Preti, F. 2020. Hydraulic Modeling of Field Experiments in a Drainage Channel Under Different Riparian Vegetation Scenarios. In Innovative Biosystems Engineering for Sustainable Agriculture, Forestry and Food Production; Coppola A., Di Renzo G., Altieri G., D’Antonio P., Eds.; Springer: Cham, Switzerland, 2020; 69–77; doi:10.1007/978-3-030-39299-4_8.

 

METHODS: Please, insert a Figure for each sub-section. This will improve the scientific quality of your study, as a great support to all the equations proposed here.

 

DISCUSSION and CONCLUSIONS: These two sections must be re-arranged according to the suggestions indicated by the reviewer.

 

These points can considerably improve the scientific sound of the article overall.

Author Response

Dear Reviewer,

thank you for your valuable comments and work on my manuscript.

The article has been corrected. In addition, the text has undergone linguistic proofreading. I am attaching the manuscript after the changes.

Yours faithfully,

Edyta Łaskawiec

Point 1: OVERALL: - Please, enlarge and re-arrange font sizes to guide the reader properly in all sections. All figures must be composed of HD images. It is mandatory to improve the scientific quality of the whole manuscript.

- Please, pay attention to the JOURNAL TEMPLATE in all sections, including tables, references, captions, units, equations, and Figures.

- Please, insert all corrected axes and labels, in order to guide the reader properly in understanding the whole manuscript. In addition, please improve the contrast between colours.

Response 1: The text has been reviewed again in terms of your comments and the guidelines of the MDPI publishing house.

Point 2: INTRODUCTION: Please, consider in the scientific background of your study the importance of advanced data analysis in the management and monitoring of natural resources broadly speaking (i.e.,

Khan, M.A., Sharma, N., Lama, G.F.C., Hasan, M., Garg, R., Busico, G., Alharbi, R.S. 2022. Three-Dimensional Hole Size (3DHS) Approach for Water Flow Turbulence Analysis over Emerging Sand Bars: Flume-Scale Experiments. Water 14, 1889. https://doi.org/10.3390/w14121889.

Box, W., Järvelä, J.,Västilä, K. 2021. Flow resistance of floodplain vegetation mixtures for modelling river flows. Journal of Hydrology, 601, 126593.

Lama, G.F.C., Errico, A., Francalanci, S., Solari, L., Chirico, G.B., Preti, F. 2020. Hydraulic Modeling of Field Experiments in a Drainage Channel Under Different Riparian Vegetation Scenarios. In Innovative Biosystems Engineering for Sustainable Agriculture, Forestry and Food Production; Coppola A., Di Renzo G., Altieri G., D’Antonio P., Eds.; Springer: Cham, Switzerland, 2020; 69–77; doi:10.1007/978-3-030-39299-4_8.

Response 2: Thank you very much, unfortunately, the proposed publications do not fit into the thematic context of the publication.

Point 3: METHODS: Please, insert a Figure for each sub-section. This will improve the scientific quality of your study, as a great support to all the equations proposed here.

Response 3: Thank you for your valuable comment. The manuscript was supplemented with a block diagram presenting the idea of the research.

Point 4: DISCUSSION and CONCLUSIONS: These two sections must be re-arranged according to the suggestions indicated by the reviewer.

Response 4: Thank you, the results and discussion sections have been reviewed and edited in line with the reviewers' comments.

Author Response File: Author Response.docx

Reviewer 4 Report

The manuscript death with the Quality assessment of sludge obtained from filter washings in swimming pool facilities. The manuscript contains meaningful information of swimming pool water sludge properties. The major weakness of the manuscript is methodology. Therefore, I am not recommending to accept this manuscript for publication in its present form.  

 

Comments:

1.      Abstract, line 8-10:   One of the solutions is the recovery of water from wastewater. How to recover water from wastewater? I have not found anything connection of these lines with the present study.   

2.      Introduction: The authors should add a statement on how is the quality assessment sludge benefit the swimming pool water quality or in the circular economy.

3.      Methodology: (i) I have not found any data on swimming water properties, such as BOD, COD, SS and TDS. (ii), Based on the Section 2.1, the sample was collected from two swimming pools after sand bed filtration, then when was the coagulation conducted? (iii). What is the parameter of the coagulation-flocculation (i.e, coagulant doses, pH, coagulation time..etc).

4.      Methodology: The authors compared the sludge properties obtained from the sample collected from two different swimming pools. However, the coagulant and the doses are differents. What is the logic of comparing the findings, when the coagulant and its doses are different?

 

5.      Methodology, Section 2.1: It is strongly suggested to add a flow diagram of swimming pools with indicating the point of sample collection.

Author Response

Dear Reviewer,

thank you for your comments and work on my manuscript. The article has been corrected. In addition, the text has undergone linguistic proofreading. I am attaching the revised manuscript and replies to detailed comments.

Yours faithfully,

Edyta Łaskawiec

Point 1: Abstract, line 8-10: One of the solutions is the recovery of water from wastewater. How to recover water from wastewater? I have not found anything connection of these lines with the present study. 

Response 1: Indeed, a large mental shortcut was used here. The sentence has been changed to: ‘’One of the solutions supporting savings is the recovery of water from wastewater, including washings obtained while rinsing the filter bed.’’

Point 2: Introduction: The authors should add a statement on how is the quality assessment sludge benefit the swimming pool water quality or in the circular economy.

Response 2:  From line 81 to 85, reference was made to the importance of the use of pool sludge in the circular economy: ‘’ Considering the significant share of sludge and suspended particles in the volume of washings, we should also analyze the potential possibilities of managing sludge from swimming pool washings - its volume share in the stream, its physicochemical properties, chemical stability and ecotoxicological risk. Because the management of waste sludge is an increasingly studied problem of the circular economy [18]’’.

Point 3: Methodology: (i) I have not found any data on swimming water properties, such as BOD, COD, SS and TDS. (ii), Based on the Section 2.1, the sample was collected from two swimming pools after sand bed filtration, then when was the coagulation conducted? (iii). What is the parameter of the coagulation-flocculation (i.e, coagulant doses, pH, coagulation time..etc).

Response 3: Thank you for your valuable comment. Generally, pool water quality was not addressed in this manuscript. I will gladly add information about the output quality of the washings in the Supplement to the article - as Table 9S. I have attached the tables here as well for your reference.  

Usually, in the swimming pool technique, the dose of the commercial product - coagulant, depending on the pool load, is 0.2-0.6 g (for pre-hydrolyzed) or 0.4-1.2 g for each m³ of circulating water. Therefore, the text has been supplemented with a more detailed explanation:

From L116 ‘’ Usually, in pool technology, the coagulant dose is selected based on the estimated load of the facility with bathers, circulation efficiency, and previous service experience. The dose may vary from hour to hour, resulting from manual adjustment. However, for the tested circuits, it is possible to determine the average dosing dose based on the efficiency of the circuit - the volume of treated water per unit of time. The capacity of Circuit 1 was 1500 m³/h, and the dosed average dose of aluminum sulfate (8.5%) was 0.75 g/m³. The capacity of Circuit 2 during the sludge sampling period was 4000 m³/h, and the dosed average dose of aluminum hydroxychloride (10%) was 0.54 g/m³.’’

Point 4: Methodology: The authors compared the sludge properties obtained from the sample collected from two different swimming pools. However, the coagulant and the doses are differents. What is the logic of comparing the findings, when the coagulant and its doses are different?

Response 4: The manuscript deliberately compared two independent circuits, differing in the type of coagulant. These are also the two most popular technological solutions used in public swimming pools. The author tried to demonstrate both the differences in the properties of sludge from different cycles, as well as their ecotoxicological potential, related, among others, to the nature of the coagulant.

Point 5: Methodology, Section 2.1: It is strongly suggested to add a flow diagram of swimming pools with indicating the point of sample collection.

Response 5: A block diagram has been added as Figure 1.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

In the revised manuscript, the authors did not address all of my suggestions and comments during the revision.

Author Response

Dear Reviewer,

thank you for your effort in reviewing my manuscript.

Yes, one element that I have not corrected is ''Discussion''. In the previous answer, I tried to explain why, despite your valuable comments, I did not do it. The Discussion of the results summarizes the results obtained in the context of the theory on which I based my research.

Yes, the subject of my work was not the analysis of heavy metal concentrations in the post-coagulant sludge but only the ecotoxicological assessment of the growth initiation of selected plant indicators. However, I wanted to highlight the reasons for the increased toxicity of sludge, and heavy metals and aluminum are undoubtedly one of the factors.

Although millions of tons of sludge from water treatment processes are produced annually worldwide, there needs to be more analysis concerning only sludge from swimming pool facilities, as they have a significant share.

Post-coagulation sludge from swimming pool facilities has yet to be characterized, hence the desire to refer to a broad research field. In the Discussion, I devoted much space to aluminum as a factor that can play a significant role in the toxic effect of sludge and is a starting point for further research. The Discussion emphasized the specificity of water treatment in such facilities and, thus, the need to constantly adjust the course of the process to the current physicochemical parameters of water. This may significantly hinder the assessment of the safety and the possibility of using post-coagulation sludge from this type of facility.

The Discussion includes a lot of valuable and essential information that will help the reader better understand the specifics of the research.

I encourage you to re-read the text.

Yours faithfully,

Edyta Łaskawiec

Author Response File: Author Response.docx

Reviewer 3 Report

The article has been improved after the first round of review. Few comments are still needed:

 

OVERALL: Please, improve the contrast between colours in the Figures. This is extremely useful for the reader.

 

INTRODUCTION: Please, consider in the scientific background of your study the importance of both advanced experimental and modeling analysis of the prediction of natural phenomena (i.e.,

 

Lama, G.F.C., Crimaldi, M., De Vivo, A., Chirico, G.B., Sarghini, F. 2021b. Eco-hydrodynamic characterization of vegetated flows derived by UAV-based imagery, 2021 IEEE International Workshop on Metrology for Agriculture and Forestry (MetroAgriFor), 273–278, doi:10.1109/MetroAgriFor52389.2021.9628749.

 

Pirone, D., Cimorelli, L., Del Giudice, G., Pianese, D. 2022. Short-term rainfall forecasting using cumulative precipitation fields from station data: a probabilistic machine learning approach. J. Hydrol. 128949. https://doi.org/10.1016/j.jhydrol.2022.128949.

 

Lama, G.F.C., Rillo Migliorini Giovannini, M., Errico, A., Mirzaei, S., Chirico, G.B., Preti, F. 2021b. The impacts of Nature Based Solutions (NBS) on vegetated flows’ dynamics in urban areas, 2021 IEEE International Workshop on Metrology for Agriculture and Forestry (MetroAgriFor), 2021, 58–63. doi:10.1109/MetroAgriFor52389.2021.9628438).

 

Author Response

Dear Reviewer,

thank you very much for re-reviewing my manuscript.

According to your recommendations

Point 1: OVERALL: Please, improve the contrast between colors in the Figures. This is extremely useful for the reader.

Response 1: I changed the colors of the graphs, where possible, to increase the contrast and improve the visibility of the data.

Point 2: INTRODUCTION: Please, consider in the scientific background of your study the importance of both advanced experimental and modeling analysis of the prediction of natural phenomena (i.e., Lama, G.F.C., Crimaldi, M., De Vivo, A., Chirico, G.B., Sarghini, F. 2021b. Eco-hydrodynamic characterization of vegetated flows derived by UAV-based imagery, 2021 IEEE International Workshop on Metrology for Agriculture and Forestry (MetroAgriFor), 273–278, doi:10.1109/MetroAgriFor52389.2021.9628749. Pirone, D., Cimorelli, L., Del Giudice, G., Pianese, D. 2022. Short-term rainfall forecasting using cumulative precipitation fields from station data: a probabilistic machine learning approach. J. Hydrol. 128949. https://doi.org/10.1016/j.jhydrol.2022.128949. Lama, G.F.C., Rillo Migliorini, Giovannini, M., Errico, A., Mirzaei, S., Chirico, G.B., Preti, F. 2021b. The impacts of Nature Based Solutions (NBS) on vegetated flows’ dynamics in urban areas, 2021 IEEE International Workshop on Metrology for Agriculture and Forestry (MetroAgriFor), 2021, 58–63. doi:10.1109/MetroAgriFor52389.2021.9628438).

Response 2: I took into account the broader aspect of the presented research in the context of literature. However, I placed this part of the work in ''Discussion'', where I thought it fit better.

I encourage you to familiarize yourself with the revised text.

Kind regards,

Edyta Łaskawiec

Author Response File: Author Response.docx