Commercially available bacterial products were used in enhancing biodegradation of monoaromatic hydrocarbons in an attached-growth bioreactor and the treatment of wastewaters containing high concentration levels of organic wastes. For the augmented attached growth system empty bed hydraulic retention times (EBHRT) of 1.9 hours to 11.6 hours were run. Results showed that at 11.6 hour EBHRT 80% removal of 10.8 mg/L feed benzene, 96.8% removal of 8.1 mg/L feed toluene and 12.7% removal of 6.1 mg/L feed xylene were achieved. In the treatment of high strength sewage, significant removal of COD, BOD and oil and grease was observed over a 4 month trial run period.