Energy Content of Organics in Municipal Wastewater Treatment Streams at Tsumori Wastewater Treatment Plant

摘要

This study elucidated the energy budget in wastewater treatment streams at Tsumori, Ichioka, and Chishima wastewater treatment plants (WWTPs) in Osaka. At Tsumori WWTP, the primary sludge produced in primary settling tanks and excess sludge produced in secondary settling tanks of the three WWTPs were collected and then digested anaerobically to biogas for cogeneration. The energy content of raw sewage at Tsumori WWTP was 4.3 kJ/L. Those at Ichioka and Chishima WWTPs were 2.1 kJ/L. The respective energy contents of primary sludge of Tsumori, Ichioka, and Chishima WWTPs were 16.3, 7.6, and 10.2 kJ/g. Those of excess sludge were 14.6, 8.3, and 9.8 kJ/g, respectively. The total calorific inflow to the three WWTPs was 1.1 × 10⁹ kJ/d. About 40% and 30% of the total calorific energy respectively becomes primary sludge and excess sludge. The remaining 30% is consumed in the aeration tanks. About 30 - 40% the total calorific energy is recovered as biogas by anaerobic digestion, which produces electricity at 1.6 × 10⁸ kJ/d, corresponding respectively to 47% and 33% of the electricity consumption of Tsumori WWTP and the three WWTPs.