Shock and transient loading on anaerobic reactor coupled with adsorber

The resilience and operational control of a unique reactor design was studied in a series of transient experiments. The reactor design included an expanded-bed granular activated carbon (GAC) anaerobic reactor with a GAC adsorber located in the recycle line. The reactor was subjected to variable loadings, a shutdown period, and a step decrease in the hydraulic residence time (HRT). During the variable-loading experiment, the influent chemical oxygen demand (COD) loading was increased from 24 kg COD/m³-d to 71 kg COD/m³-d, three times. After extended operation at 71 kg COD/m³-d, severe biological inhibition was observed and reactor failure was imminent. Rapid recovery was facilitated by the replacement of GAC from the GAC adsorber. Adsorbed organics provided substrate during a 60 h shutdown, and removal efficiencies were not affected. A step decrease in the HRT from 1 d to 2.8 h did not affect biological removal efficiency and washout of attached biomass was negligible. When subjected to severe transient operation, the performance of this reactor system was robust, and operational control allowed for rapid recovery from severe inhibition.