Optimizing sludge dewatering with an alternate pressure and electric field

Sludge dewatering is a prerequisite for the subsequent utilization of sludge. However, the existing mechanical dewatering cannot achieve satisfactory water content (< 60%). Herein, pressure and electric dewatering in alternate operation (P/EDWalt) was proposed to improve dewatering efficiency. Compared with conventional simultaneous mode, P/EDWalt performed better in sludge dewatering. Its optimal dewatering conditions were voltage of 30 V for 20 min in two electric dewaterings, and pressure of 0.04, 0.07 and 0.10 MPa in three pressure dewaterings. Such conditions, the water content of sludge was reduced from 83.7% to 53.3%, the dewatering efficiency was 36.3%, and the energy consumption was 0.138 kWh/kgtotal removed water. These phenomena such as electroosmosis, the ohmic heating and electrophoresis facilitated the removal of water in sludge, and the dewatered sludge has good reusability in incineration, landfill and agriculture. Therefore, P/EDWalt could serve as a promising method for the sludge dewatering.