Effect of HRT on performance of hybrid upflow anaerobic sludge blanket (HUASB) reactor using bio balls in treatment of pulp and paper mill bagasse wash water

Enormous quantities of bagasse are being used as raw material in agro based large integrated pulp and paper mills. Anaerobic technology is an effective means of biodegradation of organic substance in wastewater and energy production of biogas that can be used as an alternative fuel. This study illustrates the effect of HRT on performance of lab scale hybrid upflow anaerobic sludge blanket (HUASB) reactor on treatment of pulp and paper mill bagasse wash water. The lab scale HUASB reactor was designed for an effective volume of 0.013 m3 with bio balls as packing media at the top of reactor and operated under mesophilic condition. After startup period, the reactor was operated with HRTs of 23.55, 15.98, 12.00, 10.03 and 7.97 h for the average influent COD concentrations of 2503.6 mg/L, 3918 mg/L, 5432 mg/L, 6608 mg/L and 7996 mg/L respectively. The results showed that the maximum COD removal efficiencies and TSS removal efficiencies were in the range of 68.60–92.19% and 89.56–94.66% respectively. The minimum and maximum biogas yield of 0.32 and 0.53 m3/kg CODa were obtained at influent concentration of 2503.6 mg/L and 7996 mg/L respectively.