Removal of Microcystis aeruginosa through the Combined Effect of Plasma Discharge and Hydrodynamic Cavitation

Round 1

Reviewer 1 Report

 

 

Comments for author File: Comments.docx

Author Response

Responses to reviewers:

Reviewer 1:

Be consistent in naming Microcystis as cyanobacteria NOT “blue-green”Cyanobacteria (CB) were initially called blue-green algae, CB are NOT algae; cyanobacteria come in different colors, too.

Answer: you are right and it was corrected in the final text.

 

Lines 21 – 24 Comment: If the cells did not recover in seven days, either the cells are dead or badly damaged and unable to recover from the treatment.  If the cells are dead, cytoplasmic components (include toxins) will be eventually released. Suggest running cell viability; check membrane integrity. Light microscopy (visual) is not sensitive to prove these.

Answer:  please see answers to points 13 and 14, which discuss the membrane integrity. You are right and that is why we add the data from flow cytometry.

 

Line 61 cell lysis

Answer: corrected

Line 63 “… aim to develop a practical method for use in drinking water treatment plants”.

Answer:  sure, more better, corrected

 

Lines 215-220 Comments:                  

HC + plasma did NOT totally inactivate Microcystis sp.; remaining viable cells will eventually proliferate.  However, other treatments in the treatment plant will most likely remove these remaining viable cells.

If the treatment inhibited growth, either the cells are dying (or dead) or recovering from the stress and may survive. It’s possible that chlorophyll (the photosynthetic system) may be damaged and cells may eventually die.

Answer:  HC did not inactivate Microcystis, but HC+ plasma remind the cells metabolically inactive, see Figs . 8 and especially 9, where it is clear, that growth of Microcystis cells was stopped, after the combined treatment of HC and plasma.

 

Line 248 hypothesize

Answer:  thank you, corrected

Line 249 proven

Answer:  corrected as well, even the British English is proved, both versions are acceptable.

Lines 257 – 261 suggest putting arrows on cells with less vacuoles

Answer:  Thank you for this simple and perfect idea -  red arrows were used and now it will be more cleasr for readers.

Fig 12B it seems that cells did not settle on the slide surface that’s why some cells were out of focus

Answer: it is true and other cells are in the focus and we can see, that there are already a half of cells with collapsed gas vesicles,  now highlighted by red arrows.

Line 270 clarify what you mean by “extinct” suggestion: replace “extinct” = inactivate/destroy/damage/dead???

Answer: we selected inactivated, what express the situation in better way, thank you.

 

Line 297 rewrite the sentence: “Fact, that cells are not destroyed is…”

Answer: sentence is rewritten, hope now it is more clear

 

Lines 298-306 You presumed that hydroxyl radicals destroyed intracellular microcystins; free radicals can also destroy the outer membrane of cyanobacteria cells which can lead to cytoplasmic component leakage and eventually lyse and/or kill the cells. Did you measure total microcystins? 

Answer:  Microcystins were quantified after the filtration, see M+M please, line 156, so microcystins measured in this study are total extracellular microcystins, e.g. microcystins released out of the cells.

 

Lines 294 – 297 Comment: this study did not really show that the cell membrane is not damaged (intact).   A decrease in microcystin levels may be due to the breakdown of the toxin following treatments. Lines 311 – 314 faulty assumptions that cell remained intact and microcystins not released following treatments

Answer: the last 2 comments (and also comment 2) are based on the fact, that we did not presented here the data concerning the membrane integrity. We have data, we use the flow cytometry and SYTOX dye to prove the membrane integrity, but results were just similar to control and we decided to not use them as the redundant information. We do understand your point of view and now de decided to present data of membrane integrity in Supplement Information file to show, that the combination of hydrodynamic cavitation and plasma treatment can be adjusted really precisely to damage the photosynthetic activity but not destroy the membrane integrity.

 

 

Reviewer 2 Report

This is a very well-written paper on an interesting and important subject: it is certainly publishable in Water.

I have only a few minor comments to make.

1) The authors should clearly state what is new and original in their work.

Is it

- the combination of the two existing technologies

- the design of the system

- the optimization of the parameters of the treatment?

2) The English (not my mother tongue) could be improved.

3) The Table in the Supplementary material is difficult to understand, needs to be rewritten (see uploaded file).

4) Give the full Latin name of the species in the title.

5) Page 5, line 116: "Based on our previous experience" - add the reference.

Comments for author File: Comments.pdf

Author Response

REVIEWER  2:

This is a very well-written paper on an interesting and important subject: it is certainly publishable in Water.

I have only a few minor comments to make.

1) The authors should clearly state what is new and original in their work.

Is it

- the combination of the two existing technologies

- the design of the system

- the optimization of the parameters of the treatment?

Answer: Thank you for your statement, we hope that this paper will be of a high interest of wide spectrum of readers. Novel and certainly important is the possibility to optimise treatment parameters to be able to destroy photosynthesis and gas vesicles, but not cell membrane. Then cells will sediment and are simply separable in drinking water treatment.  Thank you for this idea and we add the clear statement on the merit of this paper in to the Conclusion (line 352-354).

 

2) The English (not my mother tongue) could be improved.

Answer: Also the first reviewer ask to improve and suggest some improvements, we ask again the native speaker Kevin from U.K.  who do professional editing and hope, that now the actual version is clear (at least from the British English point of view).

3) The Table in the Supplementary material is difficult to understand, needs to be rewritten (see uploaded file).

Answer: we rewrite and corrected the information in Table as well as corrected the mistake in title.  Thank you for the detailed reading, now it is correct.

4) Give the full Latin name of the species in the title.

Answer: Good idea, it is there, thank you.

5) Page 5, line 116: "Based on our previous experience" - add the reference.

Answer: we are using this routinely, but paper on it is  Premysl Mikula, Stepan Zezulka, Daniel Jancula & Blahoslav Marsalek (2012): Metabolic activity and membrane integrity changes in Microcystis aeruginosa – new findings on hydrogen peroxide toxicity in cyanobacteria, European Journal of Phycology, 47:3, 195-206  http://dx.doi.org/10.1080/09670262.2012.687144  but i tis 7 years old paper, so we corrected the text in the manuscript.   Moreover, full citation of this paper i also ad in SI.