Assessment of Nutrients Recovery Capacity and Biomass Growth of Four Microalgae Species in Anaerobic Digestion Effluent

Round 1

Reviewer 1 Report

This paper focuses on the evaluation of the bioremediation capacity of four microalgae species in anaerobic digestion effluent (ADE). The topic is interesting, and the introduction is well written and produces a sufficient background. However, major changes are required in order to further improve the quality of the paper especially in the results section and sometimes the figures and tables are redundant. Moreover, statistical analysis should be included in all the experiments. In any part of the text is mentioned if bacteria were present in ADE or in the microalgal preculture. You can find more comments below:

- line 124 in the materials and methods should be indicated if the microalgal species were axenic or not.

- line 151 in the materials and methods the pore size of used filters should be mentioned. Any other methods of sterilization were used? It was checked the presence of bacteria in the initial ADE?

- lines 186-207 paragraphs 2.4.2, 2.4.3 should go together; 2.4.2 should go after 2.4.3, and the new paragraph named culture conditions

- lines 209-275 this paragraph should be divided into subparagraphs (e.g. growth determination, nutrient analysis, protein determination, pigment analysis…etc); in the first subparagraph 2.5.1 growth determination it should be included the cell number determination. The number of replicates in each analysis should be included.

- line 278 ammonium or nitrogen content?

- line 302 table 1 could be included in table 2.

- lines 323-333 a filtration using filters with pore size of 0.2 um could help to avoid microorganisms contaminations.

- line 424 in the caption of figure 2 those are not lines but bar graphs. At the end of the cultivation, the cell number has been determinate? It is the only way to prove that the algae were growing, od and biomass concentration could be affected by bacterial growth.

- line 428 this table is a summary of all the results that should be put at the end or in a discussion section that is not present on the paper. These data are presented later on in different graphs and table (figures 4-7 and table 5).  If you don’t want to include a discussion section try to present the data just once, eventually using supplementary data.

 

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The Manuscript “Assessment of nutrients recovery capacity and biomass growth of four microalgae species in anaerobic digestion effluent” requires revision before accepted for publication. The specific comments are given below.

1. “Use of microalgae for wastewater bioremediation has been tested in many different
2. types of effluents, such as municipal, industrial, food and livestock” – state whether other researchers obtained satisfactory results. It is worth mentioning items such as:

https://doi.org/10.3390/pr8050517,

https://doi.org/10.1016/j.scitotenv.2019.135303,

https://doi.org/10.3390/en13092186,

3. Also mention the limits on the use of microalgae

https://doi.org/10.1016/j.scitotenv.2020.142168

https://doi.org/10.3390/su12239980

4. Please indicate the manufacturer, city, country when mentioning the equipment.
5. Equations should be in mathype, please revise.
6. Statistical research is very important in experiments! For example, the hypothesis on distribution of each analyzed variable can be verified with a Shapiro-Wilk test. One-way analysis of variance (ANOVA) can be used to determine the significance of the difference between variables. Variance homogeneity in groups can be checked with Levene's test, whereas the significance of differences between the analyzed variables can be determined with a Tukey’s HSD Test. If they have been tested, complete the methodology.
7. Add the standard deviations in the results listed in the text and in bar charts.
8. Graphs should be bar graphs, not spatial ones, because they do not reflect the result on the axis.
9. Please show on the graphs the correlation between the content of ammonium nitrogen in the substrate and the increase in biomass.
10. The conclusions are too extensive. Limit them to the most relevant information.
11. Correct the citation of item 50.

 

 

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript  “Assessment of nutrients recovery capacity and biomass growth of four microalgae species in anaerobic digestion effluent” reports the growth of 4 microalgal species in diluted anaerobic digestion effluent rich in N-NH4 and the effect of ADE on biomass composition. The manuscript contains interesting information but the research results are presented in an incorrect form, e.g. there is no statistical analysis. Hence, the manuscript in this form cannot be published  in Water .

Comments

1) The novelty of the presented research is poorly supported; it requires an extended elaboration in the manuscript.

2) in the manuscript, there is no basic statistic for some results. The authors provide the results without specifying the value of the standard deviation, e.g. table 1, 3,4,5 and some graphs, eg 2 d, e, f; 3 a, b, c. The data should be subjected to statistical analysis

2) line 173-174 and line 184-185 are a repetition

3) the data shown in table 4 and the data from the graphs are repeated, e.g. the data on DCW, OD and the chlorophyll, protein, carbohydrate, and lipid content. Remove the repeated results and present them either only in a table or only in graphs.

4) some figures do not have axes and/or a legend, e.g. graphs 2 d, e, f do not have axes and a legend; graphs 3 a, b, c - no axis; graphs 4 d, e, f - no axis and no legend. This should be completed.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors assisted all the 

Reviewer 2 Report

Thank you the authors for taking into account my suggestions. In my opinion the article may be published as it stands. 

Reviewer 3 Report

The manuscript „Nutrient Recovery from Wastewaters Using Microalgae-Based Systems and Potential Applications of the Produced Biomass”has been corrected according to the comments of reviewers. The authors have referred to each comment of the reviewers, the manuscript has been corrected. The manuscript in this form can be published in Waters