UASB Treatment of Tapioca Starch Wastewater

Feasibility of the upflow anaerobic sludge blanket (UASB) process was investigated for the treatment of tapioca starch industry wastewater. After removal of suspended solids by simple gravity settling, starch wastewater was used as a feed. Start-up of a 21.5-L reactor with diluted feed of approximately 3,000 mg/L chemical oxygen demand (COD) was accomplished in about 6 weeks using seed sludge from an anaerobic pond treating tapioca starch wastewater. By the end of the start-up period, gas productivity of 4-5 m3/m3r·day was obtained. Undiluted supernatant wastewater with a COD concentration of 12,000-24,000 mg/L was fed during steady-state reactor operation at an organic loading rate of 10-16 kg COD/m3r·day. The upflow velocity was maintained at 0.5 m/h with a recirculation ratio of 4:1. COD conversion efficiencies >95% and gas productivity of 5-8 m3/m3r·day were obtained. These results indicated that removal of starch solids from wastewater by simple gravity settling was sufficient to obtain satisfactory performance of the UASB process.