UV Disinfection Systems for Wastewater Treatment: Emphasis on Reactivation of Microorganisms

Round 1

Reviewer 1 Report

Please find attached PDF for comments and suggestions for authors.

Comments for author File: Comments.pdf

Author Response

The answer to Reviewer1 is in the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Undoubtedly, the highlight of the work is the extensive bibliography used and referenced. However, it is obvious that this must be its greatest potential, since the article is based, as mentioned in the abstract, on a review of previously published and documented studies.

And there also lies the greatest criticism that can be made, since in no case is it mentioned what has been the methodological systematization that has been used to carry out these queries: selection criteria for authors and articles, search process, sources of consultation, time period, etc. Thus, the structuring of the headings is organized with a merely descriptive character at the thematic level (theoretical and applied) based on the results obtained in the previous referenced studies. For this reason, it lacks the appropriate methodological justification, as has already been pointed out.

This becomes even more evident in section 4 (and in the attached graph) in which the prospects for research on wastewater treatment with the UV system are indicated. It refers only to the chronological period (2003-2022), but some other variable should be provided: consultation bases, type of publications, countries, etc.

In all the figures (the four) and tables (the two) it would be necessary to establish the authorship or, where appropriate, the source that serves as a reference. Sometimes it is a literal transcription, therefore, it is necessary to include it, regardless of whether it has been included in the text as a note. And if it is an elaboration of the authors of the evaluated article taking materials from other studies, it would also be convenient to indicate it.

Finally, the conclusions are too obvious and brief. And we believe that including a discussion section would contribute to introducing a critical and reflective approach to the methods analyzed, establishing a argued position and not a mere abridged description of previous research by other authors.

Author Response

The answer to Reviewer2 is in the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

General Overview:

The authors performed a literature review of contaminated water treatment by UV disinfection and adjuncts. They address limitations of the technique and factors related to reactivation of treated microorganisms.

Introduction & Discussion:

The authors note some disadvantages of chlorine and ozone water decontamination – mainly disinfection byproducts (DBP) generation. They emphasize that UV radiation has the potential advantages of not requiring the addition of chemicals to create oxidative stress, given the mechanism of UV radiation is DNA damage. Thus, UV radiation avoids DBP formation. As UV disinfection acts on DNA, it may also cause damage to antibiotic  resistance genes (ARGs).

The authors note that the organisms most resistant to UV rays are viruses, specifically adenoviruses and bacterial spores. Unfortunately, some pathogenic microorganisms are capable of reactivating in the presence of light – i.e., the process known as photoreactivation – or through dark repair, limiting the effectiveness of this disinfection method.

The authors note that UV radiation can be coupled with dilution to reduce the amount of effluent needed for water treatment. They review multiple chemical, biochemical and physical factors which impact the efficacy of UV radiation disinfection.

Conclusions:

It would be helpful for the reader if the authors would provide general recommended operational parameters for UV radiation water treatment plants. Although, the optimal UV wavelength and exposure duration will vary depending on key parameters the authors mention (e.g., mean particulate size & concentration, bacterial versus viral targets, extent of allowable pathogen load, solution pH, etc.), it seems that some general recommendations could be derived from the available data. It would be helpful to provide this information in a multivariate table and denote where hard evidence versus extrapolated information is used to complete the table.

References:

The authors should include commentary on the work of Adel Haji Malayeri, Madjid Mohseni, Bill Cairns and James R. Bolton on “Fluence (UV Dose) Required to Achieve Incremental Log Inactivation of Bacteria, Protozoa, Viruses and Algae” https://www.ledrise.eu/files/UV_Sensitivity_Review_full.pdf

It may be valuable to provide a table defining acronyms and referencing background reading regarding specific chemical, biochemical, and physical phenomenon. 

Author Response

The answer to Reviewer 3 is in the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have well-addressed the comments and suggestions. The paper is now ready for publications. Good job; congrats!