Biomethanation of Paper Mill liquid effluent through UASB reactor

A pilot scale UASB reactor designed to handle 6800 L of the liquid influent, was installed in GVG Paper Mill Industry, Udumalpet in Tamil Nadu. The COD of the influent varied from 4100 to 6500 10−3 kg/m3 during the experiments. The liquid waste was passed through the anaerobic reactor in up flow mode, with a hydraulic retention time (HRT) of about 3, 6, 9, 12, and 15 h that correspond to the influent flow rates of 2.27, 1.13, 0.76, 0.57, 0.45 m3/h respectively. Each trial was conducted continuously for 10 days. The highest average biogas production of 9.3 m3 is obtained at 6 h HRT with the corresponding influent flow rate of 1.13 m3/ h. The calorific value of the biogas varies from 5122 to 5406 kcal/m3. The methane content varies from 50.7 to 62.4% . The reactor has the pay back period of 6 to 6.1 years. The 6 h HRT (1.13 m3/h of influent flow rate) can be recommended for biomethanation of paper mill liquid effluent in the designed UASB reactor of 6.8 m3 capacity.