Evaluation of Sludge Yield and Phosphorus Removal in a Cannibal Solids Reduction Process

The potential for simultaneous sludge minimization and enhanced biological phosphorus removal (EBPR) in Cannibal solids reduction processes was investigated. To simulate a Cannibal-EBPR system, a sequencing batch reactor (SBR) operated with anaerobic and aerobic cycles was coupled with an anaerobic sidestream bioreactor, which received mixed liquor from the SBR and returned the same amount of treated sludge back to the SBR. The biomass yield in the Cannibal-EBPR system was estimated to be 0.16 mg volatile suspended solids (VSS)/mg chemical oxygen demand, which represented a 16–33% reduction in solids production compared to a Control-EBPR system operated with a 10-day solids retention time, for which conventional digestion of excess sludge was assumed. Regarding EBPR, greater than 98% phosphorus removal was sustainable in the Cannibal-EBPR system, but a mass balance on total phosphorus could not be closed, with nearly 33% of the phosphorus unaccounted. The fate of the missing phosphorus could not be resolved.