Investigation of energy costs for sludge management: a case study from dairy industry

Abstract

Sludge management has been regarded as an environmental challenge to deal with due tohigh energy costs for wastewater treatment plants. From this perspective, energy costs ofsludge management should be defined and calculated in order to obtain an effective energymanagement in wastewater treatment plants. Energy consumption of sludge managementis the major constituent of the operational costs. Especially, dewatering processes haveled to high electricity consumption at industrial wastewater treatment plants. This paperaimed to define the role of design and operational parameters on energy costs of sludgetreatment process in terms of total organic carbon (TOC) and sludge volume index (SVI)considering water-energy nexus. Dissolved Air Flotation (DAF) sludge and centrifuge decanter were used for sludge dewatering process in a dairy wastewater treatment plant.Lime is used for sludge stabilization. Energy cost index has been figured out using a newderived numerical method. This study proposed a new developed methodology for energy cost assessment of sludge management. This paper revealed that energy costs wouldbe lower if the wastewater treatment plant was operated under design conditions. If theplant was operated at design conditions, nearly 63% of reduction on energy costs of sludgehandling process could be ensured. It has been recommended this plant could be operatedunder design conditions.