Effects of step loadings on stability of anaerobic hybrid reactor

Abstract

Plastic rings were packed in the separator zone of a conventional upflow anaerobic sludge blanket reactor (UASB) to form an additional biofilter (BF) section. The resulting anaerobic hybrid reactor (AHR) was used to treat food - processing wastewater. The treatment performance at different step loadings was studied. The hydraulic retention time (HRT) decreased stepwise from 1.50 to 1.00, 0.75, 0.60, 0.50 and 0.40, and corresponding steady state COD removal efficiencies were 72.9, 65.9, 61.5, 56.0, 48.7 and 33.2 % respectively. In the UASB section, the COD removal accounted for between 78.2 and 64.2 % of overall removal in the AHR. In the BF section, the COD removal accounted for between 21.8 and 35.8 % of overall removal in the AHR. On the other hand, during the transient state when each step loading was introduced, the COD removal in the BF section accounted for significantly high percentage, between 66.9 % and 98.6 % of the overall removal in the AHR, because of the better stability of the immobilised microorganisms in this section. Immobilised microorganisms in the BF remained in a normal population distribution during the transient state operation, which rendered a swift recovery when favourable operation conditions were restored.