ANAEROBIC TREATMENT OF BAKERS-YEAST EFFLUENT USING A HYBRID DIGESTER WITH POLYURETHANE AS SUPPORT MATERIAL

A high-strength baker's yeast effluent was anaerobically treated using a hybrid digester under mesophilic conditions. The digester was subje cted to a substrate COD concentration of 21 767 mg/l at three differen t HRTs. At HRTs of 3.0, 2.0 and 1.0 d, the digester reduced the substr ate COD by 76, 61 and 33%, respectively. Although the best COD removal was obtained at an OLR of 7.30 kg COD/m3.d, the highest COD removal r ate (6.51 kg COD/m3.d) was found at 10.65 kg COD/m3.d at an HRT of 2.0 d. The low methane yield and VFA accumulation found in the digester e ffluent, indicated inhibition on methanogenic level and this was consi dered to be the rate-limiting step during the anaerobic treatment proc ess. The overall efficiency of the digester indicated that this digest er design and support medium was suitable for the treatment of a high- strength, sulfate-rich baker's yeast effluent.