Performance Evaluation of Up-flow Anaerobic Sludge Blanket Reactor and Aerobic Digestor of Raj Brewery, Bhairahawa, Nepal

Abstract

Large amount of wastewater is produced from brewery plants which must be treated before discharging into the environment. This research aims to study the chemical oxygen demand removal efficiency of the UASB technology and the aerobic digestor and estimate the biomethane potential that could be generated from the brewery wastewater by using UASB reactor. During the study, it was found that an average of 11 Nm3 of methane was generated daily by the UASB plant at 48 hours hydraulic retention time and at volumetric loading rate of 84 m3 . The methane yield was found to be around 0.14-0.16 m3 /kg COD removed. The COD value at the influent ranged from 165 to 3950 mg/l and the COD value at the effluent ranged from 121 to 2230 mg/l after digestion in the UASB reactor. During the observation period, the overall efficiency of the UASB reactor in terms of COD removal was found to be 52.5 %. The efficiency of the UASB reactor in terms of COD removal fluctuated from 4% to 83.64 %. The concentration of VFA was found to be 86 to 1457 mg/l. The alkalinity was found to be 400 to 1540 mg/l. The VFA to alkalinity ratio was found to range from 0.14 to 2.46. The VFA/ alkalinity ratio was found comparatively higher during observation period, which hindered the operation of plant at optimal level. The COD removal efficiency of the aerobic treatment plant ranged from 22 % to 95 % during the observation period and the average efficiency was found to be 78.5%. The average pH, BOD, COD and TSS value of treated wastewater from the effluent treatment plant were found to be 7.82, 37.94 mg/l, 100.93 mg/l and 21.33 mg/l respectively and within the disposal guidelines set by Government of Nepal. Financial Evaluation of the UASB Reactor was also conducted and the investment was found profitable provided that the plant is operated at its full capacity i.e. 350 m3 per day.