Environmentally Safe Method for Conditioning and Dewatering Sewage Sludge Using Iron Coagulant, Cellulose and Perlite

Abstract

A reasonable strategy for the development of sludge conditioning methods prior to dewatering appears to be the use of substances that allow the safe management of dewatered sludge. It is also justified to use mineral or organic conditioners instead of synthetic chemicals, e.g., polyelectrolytes, or to try to use other substances, e.g., waste. The properties of iron coagulant (PIX 113) combined with perlite and cellulose can be an environmentally safe method of sludge conditioning. The tests were carried out in accordance with European standards on the efficiency of mechanical dewatering of sewage sludge. The most advantageous method of sludge conditioning was the dosing of the iron coagulant PIX 113. The use of at least a coagulant dose of 0.40 g/g DS enabled the achievement of minimum sludge dewatering parameters, i.e., specific resistance of filtration (SRF) < 5.0 E12 m/kg and final hydration of filtration cake (FH) < 80%. The use of cellulose and perlite as stand-alone conditioners or in combination with PIX 113 resulted in a deterioration of the sludge dewaterability and the quality of the filtrate. It is assumed that the further development of environmentally friendly conditioning methods requires the use of easy-to-use, non-toxic and biodegradable substances. It is important to select conditioners which, in practically acceptable doses, can improve the conditioning effect or show a synergistic effect in combination with previously used conditioners.

Keywords

• sewage sludge
• conditioning agents
• iron salts
• structure-forming materials
• sludge dewaterability