The Development of In-situ Dewatering of Lagooned Sewage Sludge Using Electrokinetic Geosynthetics (ekg)

Once deposited in a lagoon sewage sludge in the form of a very thick liquid or cake is a difficult deposit to handle and most known methods to remediate or stabilise them are very costly or environmentally intrusive or both, EKG has the unique potential for dewatering sludge after it has been deposited in a tip or lagoon. The basic EKG concept is to combine electrokinetic phenomena with the established functions of geosynthetics. The patented electrodes known as electrokinetic prefabricated vertical drains or ePVDs include filtration and drainage functions to clean and remove the electroosmotically gathered water, engineered corrosion management and the design provide for good current distribution and electrical contact with the substrate. By functioning equally as cathodes or anodes the electrodes permit the use of polarity reversal, which is a crucial procedure in dewatering and controlling water quality. A recent field pilot trial has demonstrated the effectiveness and efficiency of using ePVDs to dewater lagooned sludge by an in situ process. The trial demonstrated that the technology could dewater sewage sludge thus raising the solids content from 10.5% to 27% whilst at the same time producing a clean discharge filtrate water with BOD< 3.0 mg/l and a COD of 250mg/l. The power consumption was 43kWhr/m. These data represent the first field trial of this technique and indicate that it can provide a viable economic solution to treating in situ lagoon sludges. The trial also indicated that significant further improvements in solids contents and reductions in power consumption are achievable at full scale.