Full scale electrokinetic dewatering of waste sludge

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2002-11, Vol.210 (2), p.231-241
• Main Authors: Raats, M.H.M, van Diemen, A.J.G, Lavèn, J, Stein, H.N
• Format: Article
• Language: English
• Subjects: Anode corrosion; Dewatering; Electro-osmosis; Filter belt; Waste slurry
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/S0927-7757(02)00380-1

Increasing volumes of waste sludge, an intense environmental awareness and stringent legislation impose increasing demands upon conventional sludge dewatering equipment. In this study, the electrokinetic dewatering of waste slurries is studied. Full-scale electrokinetic facilities were developed that were based on a combination of a gravity-driven thickening belt and a belt press. The method was tested at a drinking water production site. By the use of the electrokinetic facility when drying ‘aluminum-coagulated’ drinking water sludge (i.e. coagulated by the addition of Al-ions), the dry solids content increased by electro-osmosis from 17 to 24% m/m at an additional energy consumption level of 60 kWh per ton dry solids. Additionally, the filter belt fouling was reduced drastically and the loss of solid particles from the cake was almost completely suppressed due to electrophoresis. Corrosion of the anode was effectively suppressed by using Ir 2O 3-coated titanium plates. Supplementary laboratory experiments suggest that electrokinetic dewatering is also useful in dewatering ‘iron-coagulated’ drinking water sludge, sewage treatment sludge and fresh water dredging sludge. Theoretical analyses indicate that electro-osmosis will contribute to dewatering significantly, at lower and especially at higher volume fractions of solids, provided the slurry particles are of the order of micrometers or smaller. Under such conditions the conventional dewatering is slow due to excessive hydrodynamic resistance.