Start-Up of the Two-Stage UASB Reactor Using Paper Mill Effluent

Abstract

This study is designed to evaluate the treatability potential of using two-stage anaerobic reactors (R-I and R-II) for the treatment of paper mill effluent. It was observed that the bicarbonate alkalinity of the reactors increased from 215 to 266 mg-CaCO3/L in reactor R-I and from 456 to 604 mg-CaCO3/L in reactor R-II, by the addition of an external buffer solution. The average volatile fatty acids formation noticed within the reactors R-I and R-II was about 248 and 645 mg/L, respectively. The treatment efficiency of the reactor R-I was observed to be comparatively better than the reactor R-I throughput the course of study. The maximum COD (chemical oxygen demand) reduction observed in R-I and R-II was about 68 and 73%, respectively corresponding to an organic loading rate of 3.10 kg-COD/m3-d at a hydraulic retention time of 26 h. The average gas conversion rate observed during this study was 0.22 m3/kg-CODremoved, and in terms of methane production it was noticed to be 0.19 m3-CH4/kg-CODremoved, with 54–56% of methane. The results of this study suggest that the use of two-stage UASB (Upflow anaerobic sludge blanket) reactor to biodegrade paper mill effluent is a useful and viable technique.