Wastewater was collected from an opaque-beer brewing plant just before being discharged into the municipal treatment works. The water had a 5 day biochemical oxygen demand (BOD5) of 6525.5 mg/litre and total solids of 4844 mg/litre. Aerobic thermophilic treatment of the water at 50-degrees-C without pH control reduced the BOD5 by 67% and the suspended solids by 75%. The pH rose from 6.5 to 8.9 during treatment in 7 days. Total plate counts and amylolytic plate counts increased while total lactic acid bacteria and total yeasts decreased dramatically after the treatment.