Anaerobic Filter Treatment of Molasses Fermentation Wastewater

Two anaerobic filters were used to assess the treatability of a high strength acidic molasses fermentation wastewater containing up to 3000 mg/l of sulphate ion. The waste had to be neutralized and buffered prior to treatment and the filters operated at ambient temperature. The inlet COD concentrations were increased from 10,000 to 50,000 mg/l, organic loads ranged from 2 to 12 Kg COD/m³ day at hydraulic retention times of 2.5 and 5 days. COD removals varied from 57 to 79% and removal rates as high as 6.8 Kg COD/m³.day were obtained. Although the gas productions were reasonable, reaching 4.8 m³/m³.day, the methane content was always lower than 40% and high concentrations of hydrogen sulphide were detected in the gas. The filters were operated for seven months without sludge removal.