This paper covers the treatability results of a laboratory-scale hybrid upflow anaerobic sludge blanket reactor (HUASBR) treating dairy effluents from a large integrated industry with a maximum production capacity of 500 tons of milk per day. The study began wilb the determination of effluent characteristics and pollution profile for the investigated dairy industry. As a result of observations, by-product recovery and waste reduction alternatives were investigated by in-plant control measures. Anaerobic treatability studies were conducted by a laboratory-scale hybrid upflow anaerobic reactor with an effective volume of 81.

The reactor was operated more that 270 days under mesophilic conditions and it was fed wilb the combined effluents from the investigated dairy industry. The hydraulic retention times ranged from 0.21 to 0.96 days under normal operating conditions after the start up. COD removal efficiencies of more than 87% were achieved at an organic loading rate (OLR) of 8.5 kg COD/m3·d OLR was gradually increased from 2.54 to 7.1 kg COD/m3·d within 15 days but the anaerobic reactor performances did not change significantly. The reactor was operated under varying feed characteristics to test the response of the system to high strength acid whey. The system can tolerate OLRs as high as 17 kg COD/m3·d with an average COD removal efficiency of 75% for two weeks. Although the reactor was fed by diluted effluent with an average COD of 1070 mg/l at very high hydraulic loadings (HRT=5 hours), 75% removals of COD were achieved under these conditions.

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