Energy conservation in wastewater treatment for agricultural reuse

Agricultural irrigation is considered to be the most economical way to dispose of municipal wastewater in a sanitary manner in Israel. Due to the location of the irrigated areas, energy expenses for effluent transport cannot be reduced significantly. This paper presents a study which prepares the ground for energy savings at the treatment plants themselves. The study consisted of two parts: a survey of different types of treatment plants and a more detailed analysis of an activated-sludge and an aerated lagoons plant. Results show that energy utilization ranges from 140 to 800 W h/m³ and a properly managed activated-sludge plant can spend less energy than an aerated-lagoon plant. A possible reduction of 20% in plant energy utilization may bring about up to 8% reduction in effluent cost and promote its agricultural application.