Biological Dewatering and Waste Treatment of Fly Ash and FGD Sludge Ponds. Final Report

摘要

Wet scrubber sludges (FGD sludges) are a major national environmental problem. Dewatering of these sludges by conventional technologies is costly, but required for their permanent disposal. This report examines a novel concept for FGD sludge dewatering using emergent aquatic plants. The plants would act as wicks to remove moisture from a bed of wet sludge. An extensive literature review was carried out to develop a conceptual process for FGD sludge dewatering based on this idea. Key issues addressed were transpiration rates, salt tolerances, root aeration, organic matter decomposition, heavy metal resistance and climatic factors. Insufficient information was available in many specific areas, however, no fundamental problem or significant obstacle to the development of a marsh plant based FGD sludge dewatering process was apparent except one: hydrogen sulfide production from the reductions of sulfates or sulfites by organic material. Up to 0.1% of the total sulfur in FGD sludges could be removed by such a process, resulting in both increased atmospheric sulfur loads and, most seriously, nuisance and even toxic hydrogen sulfide concentrations. However, there are many factors which could reduce the actual amount of H sub 2 S released, and the rate of such release, well below that calculated as the upper limit; actual H sub 2 S production and release must be measured experimentally. A small scale experimental study of this concept for FGD sludge dewatering is proposed. Based on a conceptual FGD dewatering process developed during the phase I of this project a phase II research project is being submitted. (ERA citation 07:042160)