Performance Evaluation And Research For Anaerobic Digestion Process Treating Two Kinds Of Waste Activated Sludge

In this paper, the anaerobic digestion processes treating two kinds of waste activated sludge from different municipal wastewater treatment plants(WWTP) were researched and compared. Because of its containing plenty of inorganic sand, the raw water of Taiwan Anping WWTP which was transported by the canal caused the misfunction of anaerobic digestion tank. The raw water of Taibei Dihua WWTP was transported by the complete sewer system and the anaerobic digestion tank run properly. In this study, Biochemical Methane Potential (BMP) method which was proposed by Owen et al. was adopted to study the anaerobic digestion process of anaerobic sludge and waste activated sludge from two WWTPs.The anaerobic sludge was researched through selecting same substrate NaAc and setting 5 adding ratios. Inhibition of NaAc was found; the duration of lag period and gas production rate were proportional to the adding ratio. The maximum gas production rate and Km of Anping and Dihua WWTP were 67.93, 62.65 (mL/gVSS/day) and 1517, 801mg/L respectively, which indicated the anaerobic sludge of Dihua WWTP metabolized vigorously and had great biocompatibility with NaAc compared with anaerobic sludge of Anping WWTP. The anaerobic digestion of waste activated sludge was researched through setting 6 adding ratios. Waste activated sludge had little inhibition and two gas production phrases were found; in the first phrase the soluble organic and readily hydrolyzed compounds were utilized to generate CH4 rapidly; in the second phrase hydrolysis process was the limit of gas production and the maximum gas production rate was proportional to the adding ratio. The maximum gas production rate and Km of Anping and Dihua WWTP were 74.21, 51.05 (mL/gVSS/day) and 54,010, 19,010mg/L respectively, which indicated the waste activated sludge of Anping WWTP was difficult to be digested.The methanogic microbial community of the anaerobic sludge was monitored through T-RFLP. It was found that the relative content of diverse bacterium was up to 45% and Methanosaeta spp. is predominant in the methanogens in the anaerobic sludge from Anping WWTP. On the other hand, the relative content of Methanosaeta spp. in the anaerobic sludge from Dihua WWTP is 64% with the diverse bacterium a percentage of 7%. At the same time, Methanomicrobiacea, Methanobacteriacea were also found from the two kinds of anaerobic sludge. After the batch test treating NaAc, the relative content of Methanosaeta spp., which utilizes HAc to generate CH4, was improved greatly. After the batches treating waste activated sludge, the relative content of diverse bacterium was decreased while the relative contents of methanogens were improved. Observed with scanning electronic microscopy, anaerobic sludge from Dihua WWTP contained diverse methanogens which formed a microbial community while ananerobic sludge from Anping WWTP contained sparse methanogens, which were in accordance with their performance in the BMP test.