Improved sludge dewatering by addition of electro-osmosis to belt filter press

Abstract

Gravity-thickened sludge (GTS) and anaerobically-digested sludge (ADS) from a wastewater treatment plant and sludge from drying bed (DBS) from a water treatment plant were dewatered using the pilot-scale electro-osmotic belt filter press (EBFP). The results indicated that the addition of electro-osmosis greatly improved sludge dewaterability, lowering water content (WC) and heavy metal concentration, and increasing heating value. For instance, EBFP produced 56.0% WC for GTS, 58.4% for ADS, and 69.6% for DBS when current density was 41.1, 42.1, and 17.9 A/m2, respectively, and a cationic coagulant was dosed at 0.36% on dried solid, 0.46%, and 0.19%, respectively. Without the addition of electricity, the system achieved only 74.3% WC for GTS, 72.8% for ADS, and 74.7% for DBS. Therefore, EBFP would produce a proper cake WC by simply controlling the current density, depending on the destination of dewatered cake such as land application, compost, or incineration. Key words: belt filter press, cake, electro-osmosis, heating value, heavy metal concentration, water content.