Quantifying the Effect of COD to TN Ratio, DO Concentration and Temperature on Filamentous Microorganisms’ Population and Trans-Membrane Pressure (TMP) in Membrane Bio-Reactors (MBR)
, Alexandros Pentedimos 1, Margaritis Kostoglou 1,* and Anastasios Zouboulis 1,*Round 1
Reviewer 1 Report
The paper deals with the problem of reducing membrane fouling in a pilot-scale MBR by using filamentous microorganisms’ population. According to the obtained results, the authors developed the equation that correlates fouling rate (dTMP/dt) with a population of filamentous microorganisms, assessed by the FI and the concentration of SMPc.
The topic of this study is highly relevant and the results are a valuable source of knowledge relating to the membrane fouling phenomenon. The manuscript is well organized and the purpose of the study is clearly defined. In my opinion, the method of conducting the analyses as well as the obtained results raise no objections. However, it still requires revision before being accepted; the details are listed below.
In the Materials and Methods sections: The authors did not provide the concentrations (g/m3) of individual components of synthetic wastewater.
For how long the sludge was acclimated to the synthetic wastewater?
Did the Authors monitor the treatment effect? How does keeping the DO so low (0.5 mg/L) and using these kinds of populations of filaments in the biomass affect the parameters of the effluent?
It would be useful to enrich the discussion with more references to literature.
The paper should be rechecked in terms of editing and language (proofreading by a native speaker).
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Filamentous bacteria are important for the sludge flocs robusteness not only in MBR butin any ativated sludge process. In all cases a good balance is required between non filamentous and filamentous bacteria.
It cannot be said that the MBR has been operated for 8 months. Four experiments lasting 2 months each were performed. How long does it takes for the MBR to be stable in each experiment ? How the stability was assessed ?
There has been many automated image-based procedure described in the literature to be able to assess in a robust manner the filament index. The clarity of Figure 3 is very low. In any case it is not said how many images were considered manually and what was the operator effect.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
No more specific comments, although I still think that more "modern" analysis of filaments could have been done initially
