Treatment of p-Cresol with a Recirculating UASB Reactor Using the Concept of Kinetic Control

A series of batch Biochemical Methane Potential(BMP) tests and an Upflow Anaerobic Sludge Bed (UASB) bioreactor were conducted to investigate the biodegradability of p-cresol.The inhibition of microbes caused by substrate accumulation due to shock loading, recirculating pump turn-off and thermal shock were also studied. The results showed that the microbial activity was inhibited or even poisoned in the high concentration range(1000mg/L) of p-cresol. However, the volumetric loading of the reactor could be maintained relatively high at 8.0 kgCOD/m3·day, if the recirculation of effluent was used to maintain the substrate concentration in the reactor within a suitable range. The concept of so-called kinetic control was proved to be a critical strategy for the treatment of the inhibitory substrate. The results of shock loading, recirculation cessation and thermal shock tests all showed that the concentration control in the reactor would be of vital importance for the treatment of inhibitive compounds with biological processes, and the critical concentration of the highest degradation rate could be estimated with a modified Haldane equation derived from the batch BMP data.