Wastewaters from coal conversion processes are known to contain significant amounts of carcinogenic, aromatic compounds which are refractory to microbial degradation. Laboratory experiments were performed upon Solvent Refined Coal–II (SRC-II) process wastewater to modify the refractory portion of the wastewater into one that was more amenable to biological degradation. This modification was accomplished by irradiating oxygen pressurized wastewater with ultraviolet (UV) light. Under these conditions, production of the hydroxyl radical resulted in the oxidation of organic compounds.