Pilot Scale Evaluation of Electro-Osmotic Enhanced Dewatering at the Plum Island Water Pollution Control Plant
Abstract:The Charleston Water System (CWS) owns and operates the Plum Island Water Pollution Control Plant (WPCP). The plant provides wastewater treatment for all wastewater collected in the CWS system as well as several outlying towns. The plant is a conventional activated sludge plant with primary clarifiers, and it is rated for an average monthly flow of 36 million gallons per day (mgd). Residuals streams originating from the treatment process are thickened and dewatered prior to ultimate disposal by landfilling.
A facility master plan was completed in 2005, and several residuals management options were evaluated. One residuals treatment and management alternative considered was utilization of the ELCOTECH electro-dewatering system. The ELCOTECH electro-dewatering process uses electro-osmosis to enhance water removal from a dewatered cake feedstock. This enhanced dewatering process yields a much dryer cake with solids contents ranging from 30 to 50%. The process also results in the destruction of pathogens, so that the electro-dewatered cake can be classified as a Class A material suitable for land application.
In order to assess estimated performance of the electro-dewatering technology in September 2008, an ELCOTECH CINETIK™ 100 PILOT UNIT was piloted at the plant to estimate operating cost and confirm expected process benefits. Results of the pilot testing indicated the following:
When operating on a centrifuge dewatered 100% WAS feedstock with a dewatered cake concentration of 17% solids, the unit was able to dry the WAS to a solids content of 35%.
Economic evaluations considering increased electrical energy input and resultant reduced residuals mass for landfill disposal indicated that moderate operational savings could be realized with the electro-dewatering unit process.
Lifecycle costs estimates — capital and net present operating costs — indicated an economic payback period in excess of 15-years duration when pairing electro-dewatering with landfill disposal.
The long payback period was not sufficiently attractive to CWS to incorporate this potential improvement into their capital program at an accelerated schedule.
Document Type: Research Article
Publication date: 2010-01-01
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