Abstract
We desperately need to reduce the thickened sewage sludge, as it is becoming difficult to discharge in the sea from 2012. Among many ways to do it, the methane recollection by anaerobic digestion has the merit to get biogas. So, we digested waste sludge at the temperature of mesophilic digestion (35oC ± 2). At this time, HRTs were 7, 10, 15 and 20 days and the organic loads were 0.83, 1.09, 1.65 and 2.35 kg VS/m3?ay. The digester was operated for 15 days and organic material load was digested the best at 1.09 kg VS/m3·day. In case of the best digestion, pH was 7.22, alkalinity 1,978 mg/L and volatile acid 289 mg/L, and the elimination rates of the waste material of COD and BOD were 35.5% and 56.2%. Also, the elimination rate of TS and VS were 28% and 36%. Under the condition as above, the biogas production from the digester was 0.165 m3 (165 L) per the insertion of VS kg, and the methane concentration was 64.6%. In this case, the methane gas production was 0.114 m3 (114 L). But, the gas production per VS kg elimination amount was 0.520 m3 (520 L) 3.15 times more than the gas production per VS insertion and the methane gas production was 0.360 m3 (360 L). For the final processing of the digest fluid, the dehydration was good from the specific resistance of 2.53 ´ 1013 (sec2/g) in dehydration experiment by Buchner Funnel System, so the finally generated sludge cake amount will be very little and the reduction rate will be very high.