Application of Tea Polyphenols and Their Effects on Ultrafiltration Effluent Disinfection and Microbial Risk

Round 1

Reviewer 1 Report

The manuscript analyzes the effectiveness of using different doses of tea polyphenols for water disinfection. In addition, laboratory studies were conducted to assess the effectiveness of removing various strains of bacteria, viruses, fungi, etc., using tea polyphenols, conducting metagenomic analysis. In general, the work was done at a high level, but there are several issues.

 

The introduction requires a broader analysis of the use of plant polyphenols and plant sources of polyphenolic acid, their advantages and disadvantages for water disinfection (for instance, tannic acid, 10.1007/s12221-021-0019-9, etc.).

When discussing the results, it is crucial to analyze the possibility of removing the tea polyphenols from the water after the disinfection process. In addition, it is imperative to indicate if there is information on the health hazards of tea polyphenols and at what concentrations.

Section 2.2. Experimental design: A more detailed description of the research methodology is required. In what containers (material, volume) was the experiment carried out? How was the preliminary cleaning of the containers for the experiment? How many replicates was the experiment run for each added volume of tea polyphenols?

Section 2.3. Data detection and processing: please briefly describe the ferrous tartrate method for mass concentration of tea polyphenols analysis, indicating the instruments used. It is also necessary to indicate what methods and instruments were used to obtain the information presented in Table 1. In how many replicates were the studies performed to obtain the information in Table 1?

Lines 135-136: It is not clear why were 100 L of water samples disinfected with the ideal dosage of tea polyphenols, if according to Section 2.2. experiments were done using raw water?

Lines 200-201: “Some studies have shown that the higher the temperature, the faster the tea polyphenols decompose” - please confirm this with specific references to other works.

 

Minor issues:

Lines 21, 23: “tea polyphenols” -> “TP”.

Lines 32-42: Please make sure that a point instead of a semicolon separates sentences. Check it out in the rest of the manuscript as well.

Line 75: “that there can be around 104 microorganisms” -> “that there can be around 10⁴ microorganisms”? Or specify units.

Table 1: TP = 0.69 mg/L. It is not clear what was the source of the tea polyphenols (TP) in the source waters. Or was it total phosphorus in this case? Explanations in the table are required.

Line 126: “was 5TP” – please decipher.

Line 184: “The R2 value” -> “The R² value”.

Line 185: “the regression equation for your concentration” -> “the regression equation for the TP concentration.”

Table 2: Please, use superscripts on data in the column k/(L/(mg·h)).

References must be designed following the “Instructions for Authors.”

 

The manuscript requires major revisions.

Author Response

Response to Reviewer 1 Comments

Point 1: The introduction requires a broader analysis of the use of plant polyphenols and plant sources of polyphenolic acid, their advantages and disadvantages for water disinfection (for instance, tannic acid, 10.1007/s12221-021-0019-9, etc.). 


Response 1: Thank you for your advice. In the first part, the sources and uses of plant polyphenols and their advantages and disadvantages in water disinfection have been introduced. See the first paragraph of Introduction for details.

 

Point 2: When discussing the results, it is crucial to analyze the possibility of removing the tea polyphenols from the water after the disinfection process. In addition, it is imperative to indicate if there is information on the health hazards of tea polyphenols and at what concentrations. 


Response 2: Tea polyphenols, as a kind of plant polyphenols, are green in origin, mild in performance, non-toxic to humans and have health effects. Tea polyphenols are stable in solution and the regression equation fitted to their mass concentration versus time in a sterile, natural state conforms to the first order kinetic equation. The decay rate of tea polyphenols when used as a disinfectant is described in section 2.2.

 

Point 3: Section 2.2. Experimental design: A more detailed description of the research methodology is required. In what containers (material, volume) was the experiment carried out? How was the preliminary cleaning of the containers for the experiment? How many replicates was the experiment run for each added volume of tea polyphenols?


Response 3: The experimental set-up and methods are described in detail in the supplementary section 2.1. The experimental set-up was autoclaved and three parallel sets of experiments were carried out to obtain mean values.

 

Point 4: Section 2.3. Data detection and processing: please briefly describe the ferrous tartrate method for mass concentration of tea polyphenols analysis, indicating the instruments used. It is also necessary to indicate what methods and instruments were used to obtain the information presented in Table 1. In how many replicates were the studies performed to obtain the information in Table 1?


Response 4: The concentration of tea polyphenols in solution was tested using the ferrous tartrate method in GB/T21733-2008. The principle is that ferrous tartrate will complex with tea polyphenols to produce a blue-violet complex, and the content of tea polyphenols is proportional to the colour shade, which can be determined spectrophotometrically. The UV spectrophotometer is used for determination. Raw water quality required testing instruments and testing methods have been pointed out in Table 1, each data from three parallel experiments.

 

Point 5: Lines 135-136: It is not clear why were 100 L of water samples disinfected with the ideal dosage of tea polyphenols, if according to Section 2.2. experiments were done using raw water?


Response 5: Lines 135-136 cover microbial community structure and risk microbial analysis methods. Disinfection of filtered water with a better dose of tea polyphenols is more relevant and convincing.

 

Point 6: Lines 200-201: “Some studies have shown that the higher the temperature, the faster the tea polyphenols decompose” - please confirm this with specific references to other works.


Response 6: Guo Ziyu, Feng Cuimin, Wang Changzheng, et al. Study on the chemical stability of tea polyphenols and its decay kinetics in the disinfection process. China Sciencepaper, 2018(3):304-309.

http://qikan.cqvip.com/Qikan/Article/Detail?id=7000646655&from=Qikan_Search_Index

 

Point 7: Lines 21, 23: “tea polyphenols” -> “TP”


Response 7: TP is an abbreviation for Tea polyphenols, both being the same substance.

 

Point 8: Lines 32-42: Please make sure that a point instead of a semicolon separates sentences. Check it out in the rest of the manuscript as well.


Response 8: Thank you for your correction, I have revised it sentence by sentence.

 

Point 9: Line 75: “that there can be around 104 microorganisms” -> “that there can be around 104 microorganisms”? Or specify units.


Response 9: This means that if the total number of colonies per ml of water is 100 UFC, there could be around 10⁴ microorganisms present.

 

Point 10: Table 1: TP = 0.69 mg/L. It is not clear what was the source of the tea polyphenols (TP) in the source waters. Or was it total phosphorus in this case? Explanations in the table are required.


Response 10: TP is total phosphorus in Table 1 and it has been modified.

 

Point 11: Line 126: “was 5TP”-please decipher.


Response 11: Disinfected water samples with better dosing of tea polyphenols were marked as 5TP for use below.

 

Point 12: Line 184: “The R² value” -> “The R² value”.


Response 12: The decay of tea polyphenols during disinfection was consistent with the secondary reaction kinetic equation, and the R² values of the regression equations for their concentrations were all greater than 0.93. The R2 value is the fit between the measured values and the regression equation, and the higher the value, the better the fit.

 

Point 13: Line 185:“the regression equation for your concentration” -> “the regression equation for the TP concentration.”


Response 13: The regression equation for the concentration here is the regression equation for the concentration of tea polyphenols.

 

Point 14: Table 2: Please, use superscripts on data in the column k/(L/(mg·h)).


Response 14: Modified to k/(L∙(mg·h)^-1).

 

Point 15: References must be designed following the “Instructions for Authors.”


Response 15: The format of the references has been modified as required.

Reviewer 2 Report

Overall, the study is interesting, and the results are promising. However, I have some important concerns related to the study, which are stated below:

1. The authors should provide adequate details in the methodology section for reproducibility.
2. It is highly recommended that all the experiments be performed at least three times. Indicate it in the manuscript. Accordingly, the data should be reported as mean ± S.D. Furthermore, provide error bars in the figures.
3. All the abbreviations should be defined at their first mention.
4. Discussion section should be rewritten to emphasize the role of the tea polyphenols in the disinfection with the help of relevant literature reports.
5. English grammar needs improvement.

Author Response

Response to Reviewer 2 Comment

Point 1: The authors should provide adequate details in the methodology section for reproducibility. 


Response 1: Additional notes have been made on the experimental set-up and methods in Chapter 2

 

Point 2: It is highly recommended that all the experiments be performed at least three times. Indicate it in the manuscript. Accordingly, the data should be reported as mean ± S.D. Furthermore, provide error bars in the figures.


Response 2: All experiments in the text were conducted in three parallel experiments to eliminate systematic errors. The data in Table 1 have been changed to mean ± standard deviation. Error bars have been provided in Figure 2, Figure 3 and Figure 4  would lead to confusing imaging and inconvenience to the reader if the standard deviation were to be added, so the mean is used for presentation.

 

Point 3: All the abbreviations should be defined at their first mention.


Response 3: Thank you for your comments, changes have been made.

 

Point 4: Discussion section should be rewritten to emphasize the role of the tea polyphenols in the disinfection with the help of relevant literature reports.

Response 4: Modifications have been made, please see Chapter 4 Conclusions for more details.

Round 2

Reviewer 1 Report

The authors corrected all comments and answered all questions. In its current form, the manuscript contains interesting results and can be accepted for publication.

Reviewer 2 Report

The authors have satisfactorily addressed the comments. The revised version is  now improved. Therefore, the manuscript can be accepted for publication. 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Line 29 has a grammar mistake take out which.  Line 31 for should be as stand out as having. In line 31 they should be specify, is it tea or the the polyphenols in tea.  The first paragraph needs to be reexamine for readability.

Can you show the mechanism of the oxidation of the polymerization (line 153)

The paper is really hard to read.  It jumps around. The paper needs better transitions and more smoother explanations.  I don't understand the difference between your study and the study already done in literature.  I'm sure there is a difference it just needs to be more clearly stated  

Author Response

Response to Reviewer 1 Comments

Point 1: Line 29 has a grammar mistake take out which. Line 31 for should be as stand out as having. In line 31 they should be specify, is it tea or the the polyphenols in tea. The first paragraph needs to be reexamine for readability. 


Response 1: Which has been taken out in line 29. Line 31 has been changed to “polyphenols have natural antibacterial properties” and what I can confirm is that tea polyphenols are extracted from tea leaves. The first paragraph has been reorganized. Please see the text for details.

 

Point 2: Can you show the mechanism of the oxidation of the polymerization (line 153) 


Response 2: The phenolic hydroxyl groups in tea polyphenols are oxidized and polymerized under the catalysis to form dimers and polymers, and the reaction temperature will affect the enzyme activity and catalytic efficiency, so as to affect the oxidative polymerization reaction in the disinfection process of tea polyphenols and attenuate tea polyphenols to varying degrees. Please see the text for details.

 

Point 3: The paper is really hard to read. It jumps around. The paper needs better transitions and more smoother explanations. I don't understand the difference between your study and the study already done in literature. I'm sure there is a difference it just needs to be more clearly stated.


Response 3: The structure of the article has been reorganized and the conclusion has been clarified. Please see the text for details.

Reviewer 2 Report

Manuscript entitled “Effect of disinfection of tea polyphenols on ultrafiltration effluent and microbial risk” raises an important topic of water disinfection, supported with good quality results, however, presented in a very chaotic and unintuitive way.

Starting with the title, for me, it suggests that tea polyphenols are contaminants which should be eliminated, instead using them as disinfectants.

Further in the text:

• In Abstract, Authors mentioned “Illumina’s high-throughput sequencing technology” as a method of virulence factors detection. However, this method is not mentioned in main text.
• Introduction, line 33: “Cuimin Feng, Wanxia Fu [1,2] found that […]”, in my opinion presented citation way is not fully clear. I suggest using commonly used “Feng et al. [1] and Fu et al. [2]”.
• Introduction, lines 47-48: “[…] tea polyphenols can be considered instead of chlorine or chlorine disinfection […]”, whether the presented methods are by coincidence one and the same?
• The novelty of the research should be more highlighted, e.g. by adding similar research for comparison.
• Table 1: Superscripts and subscripts are missing.
• Materials and methods section: “the better/ideal dosage” are not the best formulation
• Chapter 2.3: The descriptions of plate counting method and ferrous tartrate method should be included in the manuscript, even in very brief form, or suitable reference should be given.
• Figure 1: What was the temperature of presented experiment? I think it should be noted in the figure caption.
• The lines 121-127 are very confusing. Authors are much more concentrated on decreasing of tea polyphenols concentration (which will be mentioned later, in chapter 3.2) than their inhibitory effect. Further, in line 131, the number of colonies unit is written wrongly (UFC/ml).
• Lines 131-135 raise and important issue of tea polyphenols effect on the bacteria cells. I think this part should be expanded in a separate subsection.
• Authors should be consistent in units describing. Ones is “L·mg^-1h^-1”, ones “L/mg·h”. Please standardize them. Also, in Table 2, superscripts are missing.
• In line 209 Authors write: “after disinfection of tea polyphenols”, while later (line 213 etc.) is “after disinfection with tea polyphenols”. I think the “with” version is more appropriate.
• What are the by-products of tea polyphenols degradation? Could Authors present the scheme of their degradation?

Concluding, I suggest major revision of presented manuscript, with the potential for acceptance after Authors’ corrections.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Title: Effect of disinfection of tea polyphenols on ultrafiltration effluent and microbial risk

Reviewer comments:

##Overall comments

The paper addresses the use of green tea polyphenols to disinfect ultrafiltration water. The authors have published similar work previously.  Paper has no novelty. I can’t recommend this paper for publication in this journal.

Major concerns:

1. Authors must provide the findings of a comparison of two processes, such as chlorination disinfection and polyphenols disinfection.
2. UV-light disinfection is a less expensive approach. The authors should clarify in the introduction section how polyphenol disinfection procedures differ from UV-light disinfection.
3. The reviewer cannot find the paper in reference 1. Please check.
4. The reviewer is interested if the organisms present in drinking water are entirely harmful to humans or whether there are some beneficial bacteria.
5. Line 106 has a membrane pore size of 0.2 μm, while line 76, membrane pore size of 0.01 μ The reviewer would like to know which one was utilized for this experiment.
6. Table 2. The sharp decreases in TP concentration occurred when the concentration was 10 mg/l at 4-20^o C compared to 5 mg/l at 4-20^o What are the causes behind this?
7. The following study was recently published in this journal: Water 2021, 13, 1835. https://doi.org/10.3390/w13131835; Authors should reference this study in their article and explain how polyphenol activity has improved over the combined ozone/tea polyphenols disinfection approach.
8. References should be updated.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Authors answers all my questions and corrected the manuscript. In this regard I suggest acceptance of presented revised manuscript.

Reviewer 3 Report

The authors only made minor modifications. I received unsatisfactory responses to my comments (1, 3 and 7).

Lines 30-33: What is the secondary pollution of drinking water caused by the transport pipe process?