Treating metal-contg. sewage sludge - by adding metal complexing agent, decanting and re-precipitating solubilised metal

摘要

In a process for removing (heavy) metals from aq. sewage sludge, a complex former (I) is first added to convert the metal into water-soluble and dissolved form. The sludge suspension is then sepd. into low solids and high solids phases. The sludge, impoverished w.r.t. metal, is removed. The low solids phase is treated with a reagent to ppte. the metal component, and the pptd metal cpd. and the sludge residue are sepd. from the liquor. Pref. (I) is citric acid, tartaric acid, gluconates or alkanolamines, esp trialkanolamines. Process gives good removal of (heavy) metals from industrial and other wastes. The liquor from the final stage is suitable for disposal in the drains, whilst the solid prod. is despatched to a toxic materials waste tip or to a metal recovery unit.