Intelligent energy exploitation from sewage

Abstract

Wastewater treatment plants are distinguished by considerable electricity consumption; on the other hand, organic contents of sewage allow for local energy recovery from, e.g. anaerobic digestion of sludge and subsequent use of resulting biogas in a combined heat and power unit. Supplementary incineration of dehydrated sludge in a local boiler feeding a steam turbine/generator set can provide another quantity of electricity and, at the same time, exonerates from further treatment/deposition of infectious sludge. Waste heat from both steam circuit and combustion engine can contribute to sludge drying, thus significantly increasing its heating value. Furthermore, large expanse and usual location remote of residential areas make sewage plants eligible for harvesting renewable energy. As innovative approach this study exposes that – even if all techniques considered for energy harvest in particular are state-of-the-art – under proper combination/design and intelligent operation of devices and processes, sewage plants can be widely brought towards independence of external energy supply under reasonable economic conditions.