The quality of sludge liquids produced in the process of mechanical dewatering of digested sludge

Abstract

The quality of sludge liquids produced in the processes of mechanical dewatering of sludge depends on the stabilization technology and the kind of device, its proper operation, and an appropriate choice of conditioning chemicals. The article presents the impact of selected conditioning chemicals and methods, such as: PIX 113, PIX 123, Zetag 8160 polyelectrolyte, ultrasonic field, and their combined effect on the properties of sludge liquids. crude sludge liquids were characterized by high concentrations of ammonium nitrogen (931–1,508.9 mg N-NH4 /dm), phosphates (24.3–89.4 mg PO4 /dm) and organic compounds referred to as COD (784–1,856 mg O2/dm ). It was found that the combined effect of inorganic coagulant PIX 123 and polyelectrolyte allowed the reduction of suspended solids and COD in sludge liquids. In the case of suspension, the highest reduction (53.8%) was obtained when using PIX 123. With regard to the changes of COD, similar effects were obtained for PIX 123 (43%) and the combined method (41.6%). The use of the PIX 113 coagulant and Zetag 8160 polyelectrolyte increased the ratio of total suspended solids in the sludge liquids in relation to crude sludge liquids. The PIX 113 coagulant led to reducing the values of COD (90%), ammonium nitrogen (14.9%) and phosphates (93.8%) with relation to crude sludge liquids. Zetag 8160 alone proved to be the least effective.