Evaluation of the effect of copper on the restart of a novel combined two‐stage anaerobic digester

Abstract

The performance of the modified upflow anaerobic sludge blanket (MUASB) reactor–static granular bed reactor (SGBR) series was evaluated during the restart after a starvation period of 6 months. The steady‐state chemical oxygen demand (COD) removal of the reactor series obtained during the restart with copper was 98 ± 1.96% with the corresponding biogas production and copper removal of 0.218‐m3/kg CODdigested and 81.5%, respectively. Even though the biogas production of the reactor series with copper decreased because of the inhibitory effect of the accumulated copper on the methanogens, the reactor series was maintained stable throughout the operation with the effluent characteristics well within the discharge standards. The resumption of feed after starvation was sufficient for the recovery of the biomass from a dormant to an active state when operated with and without copper. The restart of the reactor series with copper was achieved in 35 days, indicating robustness and sustainability even after starvation.