This is a very high strength waste and may be difficult to treat in an SBR. What type of waste? What is the volume you're dealing with? Is this an existing plant?

There's not a magic number for the MLVSS. You want to find a concentration that meets your maximum F/M ratio (in municipalities you can base this on the average F/M).

I would be sure there's enough nutrients and run some respirometry on this first. (make sure there's nothing inhibitory present). I would fed based on the oxygen uptake rate and try to keep this under 55 mg/L/hr or so. (where I usually notice dispersed growth)

What's the BOD? Assuming most of this is biodegradeable a pre-treatment step would be ideal.

COD may not be the only parameter of concern for compliance. Sludge age is important for determining treatment requirements and somewhat for MLVSSs. Because you have also run a pilot SBR, you should have measured the WAS for satisfactory operation. My opinion is that the pilot data should be more reliable than conventional textbook estimates.

grrun

Thanks all,

but i am not asking about the sludge age or the way of treatment..i am only asking about the VSS...if i worked with VSS of 10g/l or 20g/l or even more , this will increase the degradation rate or not ?

Dear Grrun,

Thanks for clarification.

you mean that the problem of MLVSS increasing is the lake of DO..thats mean if i still have excess oxgen it is better to increase the MLVSS as much as i could ?

Your SBR MLSS and MLVSS has no relationship to the feed COD. SBR MLSS conc. is controlled by the biomass settleability and WAS. As DS suggested, SBR MLSS should be 3-6 g/L. High MLSS will encourage a settle problem and SS wash out.

High feed COD will need a big SBR tank and more initial dilution, via less % fill at each cycle.

It is unlikely that the high saline water is the reason that the sludge is settling well, in fact I would expect the opposite to be the case.
Others have suggested that you consider anaerobic digestion for this high COD load so that you can recover some energy, and I believe that this suggestion should be given serious consideration.
With regard to selecting the MLVSS concentration as a basic design parameter, I think that this may not be a wise decision. Many aspects of the incoming wastewater, and the emission limit values need to be considered when making the final design choices, and included in the considerations should also be capital and running costs for the process when complete.

I fear that your focus may be too narrow in this case and it could be beneficial for the process and the client to broaden this focus. (This is not intended as a criticism, but is intended as advice that could be helpful).