MASS AND ENERGY FLOWS IN A MUNICIPAL WASTEWATER TREATMENT PLANT EXPRESSED AS CALORIFIC VALUES

摘要

The Municipal Wastewater Treatment Plant of Yverdon-les-Bains, Switzerland is a conventional plantrnserving 32'000 population equivalents and composed of primary sedimentation, the activated sludge process andrnclarification. Waste sludge is treated by anaerobic digestion and the resulting biogas is used for co-generation tornproduce heat and electricity. Using operational data and calorific value determinations, mass and energy balances werernmade for the unit processes related to anaerobic digestion. The results show that, in terms of calorific value, half of thernpotential energy entering the WWTP as dissolved or suspended solids is lost in the centrifuge cake. Moreover, thernamount of energy input required to operate the plant is almost the same as the amount of energy recovered from thernproduced biogas.