Dewatering of drinking water treatment sludge by vacuum electro-osmosis

The objective of this research was to evaluate the dewatering of drinking water treatment sludge (DWTS) by vacuum electro-osmosis dewatering (VEOD) technology. DWTS has a high moisture content, with the water existing as free water, pore water, surface adhesion water and internal combined water. Vacuum filtration of 0.05 MPa can quickly dewater sludge and has low energy consumption, but can only remove free water and some pore water. The moisture content of the DWTS was reduced to below 79% by vacuum filtration technique alone. At this moisture content, all free water had been expelled by vacuum filtration. Electro-osmosis optimized for the experimental conditions (0.05 MPa, 2.5 V/cm) began after vacuum filtration ceased, and drew pore water and surface adhesion water to the cathode, where it was expelled through vacuum filtration. The VEOD process removed all free water. In addition, pore water and surface adhesion water were reduced by 60.2% and 15.9%, respectively.