Occurrence and Removal Efficiency of Microplastics in Four Drinking Water Treatment Plants in Zhengzhou, China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this paper, the comprehensive comparative analysis of occurrence of microplastics (MPs) and efficiency of its removal for 4 samples taken from different drinking water treatment plants (DWTPs) of Zhengzhou city has been performed. No doubt, the data obtained and systematized are of high importance, in terms of problem of establishing limits for MPs presence in drinking water. The manuscript leaves good impression. The work is carried at high experimental level. However, before being accepted for publication in Water journal, some comments should be addressed (Minor Revision is needed).

 Comments and suggestions:

1) Abstract (Lines 22-23): “… indicated that provided an enriched…” – the sentence should be rephrased.

2) Abstract (45.83%, 74.47%) and further in Results and Discussion (Lines 265, 273 and so on): there is no need in such an accurate values of percentage; they could be rounded off to at least 1 decimal place.

3) Experimental section, Lines 117-118: please rephrase to avoid multi-using the word “stir”.

4) General note for Figures 1-5: the writings and numbers are TOO small and sometimes almost invisible for human eye. Please, enlarge.

5) No electron microscopy data were provided to illustrate the detected MPs of different shape and size.

6) Conclusion section could be slightly shorter.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The MS reports the occurrence and removal efficiency of Microplastics in four drinking water treatment plants in Zhengzhou (China). As underlined by the authors, this type of study is very important because the occurrence of MPs in drinking water treatment plants is a concern for human health and in general for the environment. Despite the importance of the study, there are several issues that should be solved before taking into consideration the MS for publication.

The main concern is about the lack of details about the actions and precautions used to prevent the potential pre-contamination of the samples by external factors. More in detail, it is not clear whether all the instruments and utensils used for the collection of the samples were pre-washed by using pre-filtred water or sterilized by UV. These details are not given in the MS and are of concern because the lack of these precautions could affect the result of the study and distort the real presence of MPs in the samples. (see pdf attached for detailed comments and suggestions) 

Another concern is the lack of any statistical test to compare the obtained results. A simple one-way ANOVA (or analogous test in case of lack of variance) could clarify whether the differences in the occurrence of MPs in the 4 examined plants and samples are significant or not.   

The limitations of the study are not given in the conclusions. These should be included:

1) regional study;

2) only four plants were analyzed,

3) a study based on a single-time sampling for each DWTP (a repetition of the sampling in different seasons could probably give more detailed results). In this regard it is not clear why the sampling was not repeated at different times (during the year) to have more detailed results. This should be clarified.

 For all these reasons the MS requires a deep revision before being reconsidered for publication.

Please find all the other detailed comments and suggestions in the pdf attached.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Moderate editing of the English language is required

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The MS was revised following the suggestions and comments and it is now clearer and more comprehensive. However there are still a few minor revisions requested:

Lines 181- 182 and 226= after the p-value the > 0.05 or <0.05 can be removed.

Author Response

Dear reviewer,

Thanks for your suggestion. The authors have thoroughly examined the entire manuscript and made corresponding revisions, highlighting them in red within the revised version (Lines 181-185, 228-230, 421-424, 442-443). 

Author Response File: Author Response.pdf