Anaerobic Digester Pilot Study

[Fred3]

I would like to build a pilot-scale anaerobic digester to demonstrate the advantages of such a system for reducing sludge volume, dewatering odors, and electrical needs at a wastewater plant. Does anyone have a working knowledge of this process? If so, I am looking for the following information/advice.

1. For a continous flow digester, should one really expect a 20 day detention time to completely digest the sludge? This is the amount of time I have been seeing on various websties and I am amazed that it takes so long.

2. Can activated sludge from the secondary clarifier be digested or is it only a viable process for sludge from primary clarifiers?

3. Are there any pictures of pilot scale digesters that I can look at to see a general layout? I am mainly concerned with the layout of the digester itself rather than the entire setup. I will need to know where to place baffles, inlets, and outlets, etc.

4. What reduction in sludge volume should be expected?

5. How much electricity (ballpark) can be generated from sludge in terms of kwH per lb VSS or TSS?

 

[orenda1168]

If you haven't done so, reviewing anaerobic digestion in "Wastewater Engineering" by Metcalf & Eddy would be a start.

Orenda

 

[ch81pc]

If carrying out mesophillic digestion (~35 degrees C) then we tend to use a retention time of 12-15 days in the primary digestor (heated)and then a further 14-16 days in the seconday open top (ambient temperature) digester. We have found a total retention of 28 days gives us a product that has a greater than 5 log reduction in Ecoli, allowing the digested sludge to be use as fertiliser. As a broad rule of thumb you can get 2 cubic feet of gas per person per day.

You can digest SAS, but the performance in terms of gas yeild and digested sludge dewaterability will decrease the more SAS is in the mixture.

How big a pilot trial do you want to carry out? I've done trials on 5 litre upto 2 ton so can let you know what set up we used for either.