Effect of Salinity on Cr(VI) Bioremediation by Algal-Bacterial Aerobic Granular Sludge Treating Synthetic Wastewater
, Xiaojing Yang 1,3,†, Shota Hirayama 1, Jixiang Wang 1, Ziwen Zhao 1, Zhongfang Lei 1,*, Kazuya Shimizu 1, Zhenya Zhang 1 and Sinh Xuan Le 2Round 1
Reviewer 1 Report
Dear authors,
The manuscript is well designed and written. It is understandable.
However, it must be improved in several aspects.
MATERIAL AND METHODS
- First of all, a 250 ml reactor is not representative for a biological system.
- 7 days of treatment are not representative for a biological system, since these systems work at long term. Even, only the acclimatization of biomass takes long time. For a punctual treatment it is better use a chemical method. Therefore, the experiment should last longer.
RESULTS AND DISCUSSION
- According to the results, the figures are not enough to see the differences that you present in the manuscript. The data should be supported by statistical analysis, such as ANOVA, t-student, PERMANOVA…
- In lines 166-177, I am not pretty sure if the increase of mean size was statistically significant, since when the standard deviation is observed, we can conclude that there is not difference.
- Figure 2 needs the error bars.
- Figure 4, it would be interesting to see the error bars.
- Lines 229 and Figure 4, was the difference between R1 and R2 statistically significant?
- Figure 6, it would be interesting to see the error bars.
- Line 284 and Figure 6, why there was initial difference between TP removal for R1 and R2? According to Figure 3, the biomass concentration was the same for this stage.
- Lines 311-315 and Figure 7, was the difference between R1 and R1 statistically significant for Cr(VI) removal?
- Line 396, was the increase of PN/PS to 3.92 statistically different from the previous values?
- Lines 411-412, were the differences between 31-51% and 28-48% statistically significant?
- Line 414, did PN excretion increase (from the statistics point of view) when Cr was introduced?
OTHER SUGGESTIONS
- In Figure 1, it is not possible to see what size the bar represents.
- It would be clearer if salinity were expressed as conductivity, to be able to compare with the conductivity of effluents of industry.
- In Figures 2 and 3, I miss more data for the same period of time, to be able to see the tendency inside the same treatment. It would be more representative.
- It would be very interesting to know the microorganisms present in the granules. (To see how the population changes and to see the main genera).
- In the legend of Figure 4, there are two letters (D and E), I think this does not correspond with a variable and they should be removed.
Comments for author File: 
Comments.pdf
Author Response
Please kindly refer to the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper reports the results of a study aimed at examining the effects of salinity on Cr(VI) bioremediation and nutrients removal performance by algal-bacterial aerobic granular sludge. The topic of this study is highly relevant and the results are a valuable source of knowledge relating to the bioremediation of algal-bacterical AGS. In my opinion, the manuscript is well prepared and organized. The method of conducting the analyses as well as the obtained results raise no objections. However, it still requires minor revision before being accepted; the details are listed below:
- The introduction could be enriched with information about novelty of the study. The originality of the study compared to previously published articles should be more emphasized (especially for work: Yang et al., 2021).
- What were the indications for the use of 1% salinity? I think it would be worth explaining why this salinity level was chosen.
- Figure 4 shows double line descriptions (D and E to the same lines as Effl. DOC R1 and R2).
- Line 312-313 – I think it would be worth explaining in more detail than "the slightly negative effect"
- Chapter 3.2.4. is very interesting and, in my opinion, it is crucial in this work, it would be worth expanding it, referring to the results found in Supplementary materials (FTIR spectra and metal fractionation).
Author Response
Please kindly refer to the attached file.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Dear authors,
the quality of the manuscript has improved, especially in the results section.
On the other hand, I still think that the volume is too small and the period of the experiment is too short. However, I understand the reasons that led you to do this investigation.
In my opinion, the manuscript is good for pubblication.
