A BIOLOGICAL PROCESS THAT REDUCES METALS IN MUNICIPAL SLUDGE TO YIELD SULPHUR ENHANCED BIOSOLIDS

摘要

Heavy metal contamination can often restrict or prohibit land application of municipal sludge. In the present investigation a continuous biological process with powdered elemental sulphur as energy source was examined for solubilization of metals from anaerobically digested municipal sludge. The results showed that the continuous process can be designed to achieve both metal solubilization and efficient sulphur utilization. With a sulphur addition of 1.5 g l~(-1) and an HRT of 14 days, solubilization efficiencies of 50, 33, 48, and 74% were obtained for cadmium, copper, nickel, and zinc, and about 80 % of the added sulphur was oxidized. Addition of ferrous sulphate as an additional energy source did not improve the performance of the process. The residual sulphur in the metal decontaminated biosolids was in balance with the phosphorus content, potentially making it an effective sulphur fertilizer for soils deficient in the nutrient.