Biodegradation of TCP in a sequencing batch-fluidized bed bioreactor with waste coke particles as the carrier

This study investigated the biodegradation of synthetic wastewater containing 2,4,6-trichlorophenol (TCP) in a sequencing batch-fluidized bed bioreactor (SBFBBR) with waste coke particles (WCPs) as the biofilm carrier. The irregular surfaces of WCPs (diameter range from 0.6 to 2.3 mm) rendered them ideal biomass carriers. The attached biomass was 4.0-4.5 mg volatile suspended solids (VSS)/g WCPs 3 weeks after reactor start-up, and the biofilm thicknesses were 35-110 μm. Biodegradation, not adsorption-degradation or volatilization-degradation, was found to be the main TCP removal mechanism. At the initial chemical oxygen demand (COD) concentration of 300 mg L-1, removal of COD was more efficient and faster than that of TCP. The air-water ratio (ranging from 0.280 to 0.58 min-1) exerted negligible effects at dissolved oxygen (DO) concentrations above 2 mg L-1. Maximum TCP degradation (62.1% after 3 h retention time and 75.8% after 6 h) occurred at initial COD concentration of 45 mg L-1. TCP can be removed by biofilm as a sole source of carbon and energy. Furthermore, the TCP biodegradation follows zero-order reaction kinetics, with the zero-order specific biodegradation rate dependent on initial COD concentration.