Thermophilic process and enhancement of excess activated sludge degradability – two ways of intensification of sludge treatment in the Prague central wastewater treatment plant

Abstract

The paper describes two ways of intensification of sludge treatment in the Prague Central Wastewater Treatment Plant: full-scale experiment with thermophilic anaerobic digestion and full-scale experiment with lysis thickening centrifuge. Increasing temperature from the mesophilic to thermophilic level in the full-scale digesters leads to a better utilization of the existing facilities and consequently avoids digester overloading. The higher degradation efficiency is associated with higher biogas production and improvement of the energy balance of the process. Due to a careful and slow increasing of the operating temperature the thermophilic process was very stable. The partial destruction of excess activated sludge cells during the thickening by means of a lysis-thickening centrifuge produces cell lysate. The presence of the cell lysate in thickened excess activated sludge causes a substantial increment in the methane yield and the biodegradability of thickened activated sludge in comparison with untreated excess sludge. The improvement of methane yield from thickened activated sludge was on average 11.5–31.3% dependent on the sludge quality. The operation of lysis-thickening centrifuges in the Prague Central Wastewater Treatment Plant proved the possibility of full-scale application of the disintegration method.