A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1991

Laboratory scale experiments were carried out to study the feasibility of employing upflow anaerobk sludge blanket (UASB) reactors to treat domestic and relatively low strength wastewater. Four 30- 1 UASB reactors, each with a 0.15 m inner diameter and 2m height, were used in this study which was conducted at an average ambient temperature of 30°C. Three reactors were inoculated with different types of seed sludge, namely: sludge from a facultative waste stabilization pond, anaerobically digested sewage sludge, and anaerobic sludge from a distillery wastewater treatment plant. The fourth reactor was started without inoculum and was studied for possible self inoculation. The AIT wastewater was mixed with a stock glucose solution to increase the influent COD concentrations to about 600 mg/l. All four reactors were started with a hydraulic retention time (HRT) of 24 h and this HRT was later reduced to 12, 6 and 3 h, consecutively, corresponding to organic loading rates (OLR) of 0.6, 1. 2, 2.4 and 4.8 kg COD/(m3.d), respectively. After about 2 months of operation, all four reactors were able to remove approximately 90% of con supplied. Scanning electron microscopic (SEM) examination of the sludge found the presence of Methanothrix bacteria to be predominant. Granulation process was not complete after 130 days of reactor operation; flocculent sludge was observed in the reactors. The experimental results obtained have suggested a technical feasibility of employing UASB reactors to treat domestic wastewaters.