METHOD FOR THE TREATMENT OF WATER TREATMENT SLUDGE

摘要

A method for the treatment of sludge obtained from such a water treatment process wherein an aluminium or iron chemical is used as a coagulant, so as to reduce the amount of sludge, which method comprises the steps of: a) treating the water treatment sludge with an inorganic acid to produce an acidic sludge comprising dissolved aluminium or iron; b) optionally separating insoluble material from the acidic sludge to produce an acidic solution comprising dissolved aluminium or iron; e) treating said acidic sludge or said acidic solution with a +1-cation compound in the presence of sulphate ions in such conditions that the pH of the sludge or solution remains at a level where aluminium precipitates as an alunite compound or iron precipitates as a jarosite compound; and d) separating the precipitated alunite or jarosite compound from the remaining sludge.