Effects of hydrocarbon degrading inoculum for carwash effluent treatment in a UASB reactor

In the present study, car wash wastewater was treated in up flow anaerobic sludge blanket (UASB) reactor. In the first step reactor was seeded with 1.5 L of anaerobic sludge and in the second step when this reactor stopped its performance 100 mL hydrocarbon degrading culture was added and operated for further one month. Samples from service station and effluent were analyzed for chemical oxygen demand (COD), electrical conductivity (EC), total dissolved solids (TDS), biogas, oil and grease. During both process the reactor was operated at 4, 3 and 2 d hydraulic retention time (HRT). UASB reactor showed good efficiency at 4 d HRT than 2 and 3 d HRT while no change in bioaugmented UASB reactor was observed. In the first phase, the reactor showed 80% and 73% removal of COD and oil/grease respectively. The biogas production was 1.45 m3 kg–1 COD removed and volatile suspended solids (VSS) was 20.69 g L–1. In bioaugmented reactor, 96%, and 96.8% removal of COD and oil/grease respectively was observed. The average biogas production was 2.137 m3 kg–1 COD removed and VSS was 40.5 g L–1. It is concluded that bioaugmentation proved as a good practice and showed better results than sludge process alone in UASB reactor.