Study on the Occurrence of Artificial Sweeteners, Parabens, and Other Emerging Contaminants in Hospital Wastewater Using LC-QToF-MS Target Screening Approach

Round 1

Reviewer 1 Report

The article concerns an interesting and current problem of emerging contaminates in sewage. The authors determined a wide range of compounds in hospital wastewater. The results and conclusions will be of interest to readers. However, the proposed changes should be made before publication:

 

·        Keywords - too many keywords. According to the reviewer, health care units, chemical analysis, target analysis are unnecessary words. Emerging contaminants and hospital wastewater are missing

·        Line 38 Replace „rate range” with rate ranged

·        Line 39 Replace „which are” with that are

·        Lines 42-24 Replace  „antibiotic resistant” with  antibiotic-resistant

·        Line 45 Replace „focused to” with focused on

·        Line 46 Replace „Additionally” with In additionally

·        Line 50 Replace „saccharine” with saccharin

·        Line 50 Replace „contained” with were contained

·        Line 59 Replace „Beside” with Besides

·        Lines 67-68 Replace „triethylcitrate” with triethyl citrate

·        Line 83 Replace „differences on” with differences in

·        Table 1- transfer table 1 to the supplementary materials,

·        Point 2.2 – replace „located in” with located on

·        Point 2.4 – replace „elusion program” with elution program,

·        Point 2.5 – sentence „Additionally, for the samples in which target compounds were not detected, a zero value was considered when calculating the mean concentration”. it would be better if the sentence looked like this Additionally, a zero value was considered when calculating the mean concentration for the samples in which target compounds were not detected,

·        Point 2.5 – replace „Table S3 and the respective” with Table S3 and the respectively

·        Point 3.2 Site 16, Line 12 – replace „lauryl diethanolamide that is” with lauryl diethanolamide which is,

·        Conclusions, Lines 78-79- replace „metabolites was investigated” with metabolites were investigated

·        Conclusions – please enter information on the concentrations of the most frequently identified emerging contaminants in the analyzed wastewater

·        consider transferring the Figure S1 to the main text

Comments for author File: Comments.pdf

Author Response

We would like to thank the Reviewer for the comments aiming to the improvement of our work. Please find below a point-by-point response to each comment. All changes in manuscript are marked with tracks

Response to Reviewer’s 1 comments

Comment 1: The article concerns an interesting and current problem of emerging contaminates in sewage. The authors determined a wide range of compounds in hospital wastewater. The results and conclusions will be of interest to readers.

Response:

We would like to thank Reviewer 1 for the positive and constructive comments. Text has been amended accordingly to Reviewer’s suggestions.

 

Comment 2:

1. Keywords - too many keywords. According to the reviewer, health care units, chemical analysis, target analysis are unnecessary words. Emerging contaminants and hospital wastewater are missing
2. Line 38 Replace “rate range” with rate ranged
3. Line 39 Replace “which are” with that are
4. Lines 42 Replace “antibiotic resistant” with antibiotic-resistant
5. Line 45 Replace “focused to” with focused on
6. Line 46 Replace “Additionally” with In additionally
7. Line 50 Replace “saccharine” with saccharin
8. Line 50 Replace “contained” with were contained
9. Line 59 Replace “Beside” with Besides
10. Lines 67-68 Replace “triethylcitrate” with triethyl citrate
11. Line 83 Replace “differences on” with differences in
12. Table 1- Transfer table 1 to the supplementary materials
13. Point 2.2 - Replace “located in” with located on
14. Point 2.4 - Replace “elusion program” with elution program
15. Point 2.5 - sentence “Additionally, for the samples in which target compounds were not detected, a zero value was considered when calculating the mean concentration”. it would be better if the sentence looked like this Additionally, a zero value was considered when calculating the mean concentration for the samples in which target compounds were not detected
16. Point 2.5 - Replace “Table S3 and the respective” with Table S3 and the respectively
17. Point 3.2 Site 16, Line 12 – Replace “lauryl diethanolamide that is” with lauryl diethanolamide which is,
18. Conclusions, Lines 78-79- replace “metabolites was investigated” with metabolites were investigated
19. Conclusions - please enter information on the concentrations of the most frequently identified emerging contaminants in the analyzed wastewater
20. Consider transferring the Figure S1 to the main text

Response:

Please find our changes point-by-point:

1. We revised the keywords
2. Corrected
3. Corrected
4. Corrected
5. Corrected
6. Corrected
7. Both saccharine and saccharin could be used .However, we chose “saccharine” to be consistent throughout the whole manuscript, tables and figures.
8. Corrected
9. Corrected
10. Corrected
11. Corrected
12. We have moved Table 1 to Supplementary file
13. Corrected
14. Corrected
15. Corrected
16. Corrected
17. Corrected
18. Corrected
19. We have added the following phrase in the Conclusions section “The three highest mean concentrations were recorded for cyclamic acid (377 μg/L, Point A), saccharine (295 μg/L, Point A), caffeine (193 μg/L, Point A).”
20. We do not believe that the Figure S1 would be useful to be transferred to the main text. So, we kept it in Supplementary material.

Reviewer 2 Report

The emerging contaminants (ECs) in hospital wastewater (HWW) were studied in the manuscript “Water-2246559“.  The frequency of appearance (FoA), the concentration of ECs and their transformation products (TPs) were investigated. The concentration of ECs in HWW with that in municipal wastewater was also compared. The study concluded that the most important EC in HWW came from coffee and tobacco-related compounds, artificial sweeteners and personal care products as well as industrial chemicals, while " indicate that, in addition to pharmaceuticals, hospitals are a significant source for other groups of emerging pollutants, such as artificial sweeteners, parabens, and stimulants".

The reviewer believe that the above conclusions obtained by LC-QToF-MS analysis are basically credible, which expands people's cognition of hospital wastewater and ECs, and has certain novelty and scientific value. The comparison of HWW and municipal wastewater gives people a clear understanding that this comparison is valuable.

However, in my personal opinion, the research method used in this paper seems not very rigorous. Mainly manifested in:

1) The influence of the sampling season

Samples were collected in November and February, which were late autumn or winter, with lower temperatures. At this time, the microbial activity was weak, the organic matter might be protected from biodegradation and thus showed a concentration higher than that in the other seasons and the transformation products (TPs) of related ECs would be less. When compared with municipal wastewater, there was no indication of the municipal wastewater sampling season, and similarly, the amount of organic matter concentration in municipal wastewater and its TPs would vary more or less.

2) The influence of the wastewater transportation process

Comparison of ECs concentrations in HWW and in municipal wastewater should consider the impact of the municipal wastewater transport procedures. There was an important influence of microbial role in WWTP. In other words, the concentration of ECs in municipal wastewater was not their source concentration, but the ECs data in HWW listed in the paper were the source concentration, we were not sure how the ECs would have changed if HWW after several kilometers of transportation. Under the same conditions (or similar / simulated conditions), the contribution of ECs from HWW to the total ECs in municipal wastewater should be more convincing.

Some other possible flaws:

l  References in the text. If marked in numerical order, do not need to date. For example: Line 72, Gönder et al., (2021) [18], which might be Gönder et al. [18]. Similarly, L 81, L83....

I don't know why the numbers in the text are expressed in both English and Arabic numerals, such as 2.1. Standards and chemicals, "... four (4) artificial sweeteners, six (6) personal care products, five (5) coffee..." 

Author Response

Response to Reviewer’s 2 comments

Comment 1: The emerging contaminants (ECs) in hospital wastewater (HWW) were studied in the manuscript “Water-2246559“. The frequency of appearance (FoA), the concentration of ECs and their transformation products (TPs) were investigated. The concentration of ECs in HWW with that in municipal wastewater was also compared. The study concluded that the most important EC in HWW came from coffee and tobacco-related compounds, artificial sweeteners and personal care products as well as industrial chemicals, while "indicate that, in addition to pharmaceuticals, hospitals are a significant source for other groups of emerging pollutants, such as artificial sweeteners, parabens, and stimulants". The reviewer believe that the above conclusions obtained by LC-QToF-MS analysis are basically credible, which expands people's cognition of hospital wastewater and ECs, and has certain novelty and scientific value. The comparison of HWW and municipal wastewater gives people a clear understanding that this comparison is valuable. However, in my personal opinion, the research method used in this paper seems not very rigorous.

Response:

We thank Reviewer 2 for this general comment. We followed Reviewers’ suggestion and we improved our manuscript.

Comment 2: The influence of the sampling season.

Samples were collected in November and February, which were late autumn or winter, with lower temperatures. At this time, the microbial activity was weak, the organic matter might be protected from biodegradation and thus showed a concentration higher than that in the other seasons and the transformation products (TPs) of related ECs would be less. When compared with municipal wastewater, there was no indication of the municipal wastewater sampling season, and similarly, the amount of organic matter concentration in municipal wastewater and its TPs would vary more or less.

Response:

We thank Reviewer 2 for his/her comment, because it allows us to explain the sampling strategy that was followed. We randomly selected five consecutive days in each of these periods and as a result the first sampling campaign was conducted in early November 2020 and the second in mid-February 2021 (as already written in the main text). It should be mentioned that the examined hospital is located on the island of Crete (South Greece). In this region, November has still sunny days and high temperatures and it is not considered as winter. In this area, the average temperatures in November and February are around 17 and 13 °C, respectively.

We would like also indicate that the collected wastewater samples were raw hospital wastewater. They have not passed through a biological treatment reactor that could enhance further biotransformation of parent compounds. Similarly, the municipal wastewater samples that are used for comparison reasons are raw wastewater.

Finally, the organic loading of the collected samples in this study was typical for hospital wastewater (please see Table 1, range of BOD: 220-480) and quite similar to that found in municipal wastewater.

Comment 3: The influence of the wastewater transportation process.

Comparison of ECs concentrations in HWW and in municipal wastewater should consider the impact of the municipal wastewater transport procedures. There was an important influence of microbial role in WWTP. In other words, the concentration of ECs in municipal wastewater was not their source concentration, but the ECs data in HWW listed in the paper were the source concentration, we were not sure how the ECs would have changed if HWW after several kilometers of transportation. Under the same conditions (or similar / simulated conditions), the contribution of ECs from HWW to the total ECs in municipal wastewater should be more convincing.

Response:

The typical methodology applied during collection of wastewater samples from a municipal WWTP includes the transport of the samples in portable coolers at 4 ^oC using ice packs in order to avoid their spoilage. This procedure is typical for all valid monitoring studies and it is described in all papers used in the current study for examining the occurrence of ECs in municipal wastewater (see for example ref 32, 35, 37). Based to this, no impact of the transport procedures on the samples’ characteristics is expected.

Comment 4: Some other possible flaws:

83. References in the text. If marked in numerical order, do not need to date. For example: Line 72, Gönder et al., (2021) [18], which might be Gönder et al. [18]. Similarly, L 81, L83....
84. I don't know why the numbers in the text are expressed in both English and Arabic numerals, such as 2.1. Standards and chemicals, "... four (4) artificial sweeteners, six (6) personal care products, five (5) coffee..."

Response:

1. All relative references were corrected throughout the manuscript
2. We believe that this expression of numbers aids the readers to read the manuscript.