Anaerobic treatment of phenolic coal conversion wastewater in semicontinuous cultures

High strength wastewater (7600 mg 1⁻¹ phenolics) from the H-coal liquefaction process was diluted and fed to anaerobic, methane-producing cultures. Total phenolic concentrations of 150 and 300 mg 1⁻¹ were added to 50 ml semicontinuous cultures with hydraulic retention times of 12.5, 16.7 and 25 days. The rates of methane production and effluent concentrations of three fermentable phenolics (phenol, p-cresol and m-cresol) were monitored over a 188-day period. After acclimation to the wastewater, stable periods followed during which each of the six cultures removed essentially all of these fermentable phenolics. The duration of the stable periods decreased with increasing phenolic mass loading rates. m-Cresol was the first phenolic to appear in the effluent and its presence served as the first indicator of reduced phenolic removal capability. The effluent m-cresol concentrations from cultures receiving 300 mg 1⁻¹ total phenolics followed simple washout curves suggesting that its degradation stopped abruptly. Later, p-cresol and ultimately phenol appeared in the effluents from the cultures which received the highest phenolic mass loadings.