Comparison of the Advantages and Disadvantages of Algae Removal Technology and Its Development Status

Round 1

Reviewer 1 Report

The authors presented in a very descriptive form many algae removal technologies, however, such a review should be much more comprehensive. In the entire manuscript, mainly descriptive information about the advantages/disadvantages of processes is presented, and this is why it is very difficult to assess their potential. For example, what does it mean that chemical methods can kill algae quickly? Some concentration of the reagents should be presented, contact time details, mortality rate, etc. Maybe some figures? In my opinion, the authors should avoid using such statements as good removal, low concentration, low turbidity, suitable for water bodies with small watersheds, low impact on the ecosystem, etc.  Without structured measurable data it is very difficult to assess the efficiency of the given techniques. The presented techniques should be described according to many crucial details: when they can be used (what kind of critical concentration of biogenic substances, oxygen, and algae is required to use specific techniques, etc), in which water bodies according to their surface. In the present form, the ms seems to be far from the scientific form, and this is why it could not be recommended for publication.  

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

In the light of the growing worldwide problems associated with toxic cyanobacterial blooms, this paper provides an interesting overview of the various methods (physical, chemical, biological) of removing them from the environment. These methods include many removal technologies that combine different approaches and are often still in the laboratory research phase. What I miss in the article is a clearer opinion from the authors on the applicability and effectiveness of these new methods in large aquatic ecosystems and the possibility of their integration with biological methods.

 

Some minor errors and shortcomings found in the paper are listed below:

 

1.        Line 44: What is the “Sai's transparency” method? I have not encountered such a method in limnologic research. 2.        Line 60: please delete duplicated word "collapse" in the phrase: “collapse of the freshwater ecosystem collapse” 3.        Line 62: to be precise instead of “algal toxins (MCs)” write „cyanobacterial toxins (MCs)”. 4.        Line 74: the source of the classification presented in the table 1 should be indicated in the table heading. 5.        Lines 133, 146, 367, 369: remove the initials for a first name of the authors of the cited papers. 6.        Line 176-177: the phrase should rather be: “The biological method uses the food chain relationship between organisms in the natural ecosystem…” 7.        Table 3: describing the advantage of using aquatic plants as algae removal technology the authors write: “high water bloom time can effectively inhibit algae” and similarly in lines 254-255: “high hydration can effectively inhibit algae…”. What do the authors have in mind here? High hydration has usually little effect on competition between algae and submerged and/or floating plants which are the main competitors of algae. On the contrary, an increase in the water level may restrict light access to submerged, bottom-rooted plants and limit their growth and competitive ability. 8.        Line 229: fungi are mentioned here as organisms used to control algal blooms, but I have not found a citation of any article on this subject in the entire text. 9.        Lines 274-275: I do not entirely agree with the authors' statement that “… zooplankton feeding on phytoplankton is extremely inefficient”. There are many examples of how zooplankton can effectively filter algae and prevent cyanobacterial blooms, especially in mesotrophic temperate zone lakes (e.g. the occurrence of a “clear water phase” even in strongly eutrophic lakes). 10.    Lines 278-282: This part of the text needs to be rewritten as it is currently difficult to understand. 11.    Lines 289-291: it is worth clarifying here that 'high environmental impact' only applies when we introduce alien species into the ecosystem, which should not be the case in classical biomanipulation. 12.    Lines 320-321: which name is correct, the one in the text (polydimethyldiallylammonium chloride) or the one in the cited paper (polydiallyldimethylammonium chloride)? 13.    Line 325: correct to “Anderson”. 14.    Lines 413-414: please delete duplicated word "improvement" in the phrase: “At present, due to the improvement and improvement of drinking water quality standards…”. 15.    Line 585: replace 催化剂 with “catalysts”.

 

16.    Line 669: the abbreviation “TOC” appears here for the first time so its full name should be given.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The frequent outbreaks of algae blooms lead to severe water pollution. This paper summarizes the algae removal technologies and makes comments on the advantages and disadvantages of them. This topic is fit for this journal and is useful for the related readers. But it needs further improvements, and the specific comments are as follows.

(1)   The title is on a wider topic of algae removal, while the introduction section only focuses on cyanobacteria removal. Some eukaryotic algae also cause problems. A balance in the introduction section is needed, and the topic should not be narrowed down from algae to cyanobacteria.

(2)   For some of the technologies, the mechanism, advantages and disadvantages are introduced, while the new and major research achievements in overcoming the disadvantages are not thoroughly introduced.

(3)   The following comment is for your reference only: It might be better to add one more sub-section on the newly typical and successful applications of the technologies on algae removal in the typical water bodies like sea water near the sea shore, lake, river etc., and comment on the usefulness and further improvements needed for real applications.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

This review concerns a manuscript titled: “Comparison of the advantages and disadvantages of algae removal technology and its development status” submitted for consideration to the Water journal. The manuscript reviews various methods/technologies for removal of algae from water. The manuscript is interesting, generally well prepared, and on the topic relevant to the journal’s readership. There are however some points that should be addressed before possible publication.

 

1.    The classification of eutrophication provided on page 1 does not match the classification provided in Table 1.

2.    The manuscript uses numerous abbreviations that are never defined. MC-LR, BDD, and TOC are just a few examples. All abbreviations should be defined before being used.

3.    The reviewer noted frequent issues with many chemical reactions, such as missing products, unbalanced equations, and non-English characters. Rxs 2,3,5, and 11 are just a few examples. All reactions should be reviewed and revise to correct these errors.

4.    Molecular masses are missing proper units. All quantities should be provided with their proper units.

5.    There are quite a few statements in the manuscript that are not sufficiently supported with references. For example: “Currently, hydrodynamic cavitation/hydrogen peroxide co-oxidation technology has been more reported in the field of wastewater treatment.” but not references are provided to support that evaluation. Subsequently, a single publication using such method is discussed. It’s advised that the authors either revise such sentences (there are more than this example) or sufficiently support them with literature references.

6.    Is the explanation of clay flocculation provided in table 2 correct? It is not clear how settling of particles of clay and water serves the purpose of removing algae.

7.    The manuscript lists a number of membrane filtration methods without commenting on the differences or providing details. It would be educational to the prospective reader to include such information.

Author Response

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