Application of the Anammox Process for Treatment of Liquid Phase Digestate

Round 1

Reviewer 1 Report

The article should be corrected before publication in the scope of:

1. Please explain abbreviation AUR (abstract).
2. The title should be changed, it should emphasize the use of the annamox process for the treatment of leachate from the anaerobic digestion of substrates. The idea behind this process is the degradation and not the production of biogas.
3. The introduction should provide more information / literature discussions on the research topic - annamox procces. The importance of the research should be emphasized more. Basic information about  fermentation can be limited. The introduction should start from annamox information.
4. line 107-110 and Table 1 - it is not easy to understand the idea of loading the reactor with a COD, which is given as % of the reactor volume. Should be explain.
5. Line 126 - Was filtration through a 0.45 µm filter to separate the slurry fraction necessary after centrifuging? 
6. results:It should be more explained: synthetic effluents with COD and synthetic effluents without COD.
7. General dependencies should be provided in the conclusions. Information from the test results should not be repeated.

Author Response

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is bad written and very confusing. The novelty is limited and many important information are missing.

In my opinion the paper is not publishable in the present form and it could be considered for publication only after a major revision.

Specific comments:

• English is very bad and should be completely revised by a native speaker prior to publication. This is mandatory in my opinion.
• Line 73-75: Please describe better your system maybe with a picture or a drawing/scheme in order to be more clear
• Line 96: where did you take your inoculum?
• Line 101. from here this is the most confusing paragraph. The descriptions of your experiments should be much more precise and detailed.
• Line 108: what does it mean that COD was added at a certain percentage of the reactor volume? This doesn't make sense. What these percentages are referred to?
• Table 1: please add all other characteristics, N additions, C/N ratio etc.
• Line 119: The ratio 1:3 was in volume, in dry solid content, in COD...? and the sludge was taken from the oxidation tank? or was waste activated sludge? was it dewatered, thickened? all these details are important in order to made you experiments reproducible
• Line 122 did you record the changes in pH?
• Line 126 Here lies by biggest concern:

  • First of all, which is the destiny of the solid fraction in your proposed treatment line?

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    Secondly, you filtrate at 0.45 um but is this feasible at an industrial level? The level of filtration (cut-off of the membrane) change dramatically the quality of the liquid fraction and the performance of the anammox process

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    You never mention the conductivity of the digestate but this seems to be a key parameter in the process since many small organic molecules and inorganic salts can be retained in the slurry or pass in the liquid phase (and here it depends on the liquid/solid separation technique) with again important consequences on the performance of anamox process. Here you have few examples: https://doi.org/10.1016/j.wasman.2019.08.044  and https://doi.org/10.1016/j.wasman.2016.11.014  

• I believe you should add a table with all the AUR and the SAA for each test, it could make the results a lot more easy to read and understand
• Conclusions are more of an abstract that a conclusion

Author Response

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Authors successfully modified the paper as suggested. I believe the manuscript can be accepted for publication.