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Posted 4/1/2008 5:09:43 PM
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We're considering this at a 6 Mgd Tertiary Plant (Ox ditch, clarifier, continuous backwash filter).  Would like to review case studies and experiences from existing operations - particularly how other biological processes were affected - positive or negative. General real life Pros and Cons.  Thanks.
Post #8799
Posted 4/1/2008 5:51:56 PM


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Warner:

You may want to get a hold of the following article by John T. Novak et al, "Biological Solids Reduction using the Cannibal Process", Water Environment Research, Vol. 79, No. 12, Nov. 2007, pp 2380-2386.  Use the following link to view abstract of article and other information:

Biological Solids Reduction Using the Cannibal Process

Abstract:

A laboratory study of the Cannibal process was undertaken to determine if the Cannibal system would generate less sludge compared with a conventional activated sludge system. Side-by-side sequencing batch reactors were operated—one using the Cannibal configuration and the other as conventional activated sludge. It was found that the Cannibal process generated 60% less solids than the conventional activated sludge system, without any negative effect on the effluent quality or the settling characteristics of the activated sludge. The oxygen uptake rate for the centrate from the Cannibal bioreactor showed that readily biodegradable organic matter was released from the recycled biomass in the Cannibal bioreactor. It is proposed that the mechanism for reduced solids from the Cannibal system is that, in the Cannibal bioreactor, iron is reduced, releasing iron-bound organic material into solution. When the Cannibal biomass is recirculated back to the aeration basin, the released organic material is rapidly degraded.

E. coli happens!

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Post #8801
Posted 4/2/2008 1:33:36 PM


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My impression of the Cannibal process is that the fine screens remove toilet paper fibers etc and the cyclones remove "sugar sand" so the MLSS is composed of a much higher % of real active bugs and less organic and inorganic trash.   That means for a given MLSS, Cannibal MLSS has more capacity than normal MLSS.  Since loading to clarifiers can limit capacity I would think a Cannibal plant would have more capacity for a similar aeration basin and clarifier.  The MLSS is aerobically digested.

Does that sound right?

Post #8806
Posted 6/5/2008 2:03:02 PM
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Rob has it pretty close. The two main components are the solids removal system on the RAS that removes fines and inerts, and the interchange reactor, which acts as a sort of facultative digester. The difference is the ML is then returned to the main treatment process. There is a need for an occasional "purge" or blowdown of solids from the system (actual WAS), based on the need to remove very fine inerts that build up in the system over time.

The vendor applies the system only to relatively long SRT processes (i.e., 8 days+). The return of the interchanged solids actually adds about 10% organic loading to the aeration system, which in turn increases oxygen demand. I know of no claim that the system allows higher loadings.

The reports I've seen from operating facilities are positive; the secondary process is generally healthy, with good SVIs and good effluent quality. Net solids production is very low, and operators have the freedom to time the wasting. The purged material does not meet Part 503 requirements for anything; processing is needed for pathogens and vector attraction reduction.

It will be interesting to watch how the process unfolds as more installations are brought into service.

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