Anaerobic treatment of a biologically inhibitory wastewater

A sequence of unit processes consisting of a berl-saddle-packed-bed anaerobic reactor and an expanded-bed, granular activated carbon fluidized-bed anaerobic reactor was used for the treatment of a synthetically prepared coal conversion wastewater. The wastewater, with high concentrations of inhibitory compounds, was fed at three different chemical oxygen demand (COD) concentrations: 1513, 3027, and 7567 mg/L. Excellent removal of organic matter combined with high conversion of COD to methane was achieved. Negligible removal of COD was observed in the packed-bed reactor whereas the expanded-bed GAC reactor removed the majority of the organics in the wastewater. Ortho- and meta-cresol resisted biodegradation and their toxicity to the anaerobic culture in the GAC reactor was overcome by partial replacement of the granular activated carbon medium in that reactor.