A Comparative Study of the Electro-dewatering of Pulp and Paper Mill Biosludge

The activated sludge process, often used in pulp and paper mills, generates biosludge that requires dewatering. Wastewater treatment practices and upstream processes impact biosludge characteristics, including dewaterability. Electro-dewatering, compared to other dewatering methods, has a high dewatering potential while requiring low amounts of energy. The main objective of this study was to determine the variation in the characteristics of mill biosludge and its impact on electro-dewatering. Biosludge was sampled from four different wastewater treatment plants, including a municipal one as cross-reference, and characterized for various properties. Using a bench-scale electro-dewatering device, thickened biosludge was subjected to constant-voltage electro-dewatering at 20 V. Electro-dewatering successfully removed 68-74% of the water while consuming between 0.15 and 0.56 kWh/kg additional water removed. Overall, varying biosludge characteristics did not impact the total amount of water removed, but certain characteristics, particularly the electrical conductivity, dictated the routes of water removal (evaporation, filtration) and energy consumption.M.A.S