Using thermal-acidic-modified kaolin as a physical-chemical conditioner for waste activated sludge dewatering.

[Display omitted] • Thermal-acidic-modified kaolin (TAMK) is an inorganic coagulant. • TAMK acts as a physical-chemical conditioner in sludge dewatering. • SiO 2 and Al3+ are the main elements of TAMK in sludge dewatering. • TAMK is competitively priced for inorganic coagulant. In this study, the effect of thermal-acidic-modified kaolin (TAMK) on waste activated sludge (WAS) conditioning and dewatering was investigated for the first time. Using analyses of XRD, XRF, FT-IR, porosity and specific surface area, structural changes of kaolin were evaluated before and after modification. Conditioning with TAMK reduced the specific resistance to filterability (SRF) and time to filter (TTF), capillary suction time (CST) of WAS to 91.2%, 73.1% and 70.8% respectively. WAS conditioning with TAMK resulted in reducing compressibility and increasing filtration yield, the porosity of WAS, that indicating its function as a physical conditioner (skeleton builder). TAMK increased the WAS particle size significantly (from 47.8 μm to 451 μm) and improved their resistance against shear force. TAMK decreased the bound water (58.1%), negative zeta potential (from −31.4 mV to −7.2 mV) and EPS (extracellular polymeric substances) of WAS, indicating its function as a chemical conditioner. This study showed that TAMK acts as a physical-chemical conditioner. Also, the estimated costs of WAS conditioning with TAMK is 35.22 $/ton dry solids (DS). In general, TAMK is an affordable, inexpensive and effective option for sludge conditioning and dewatering. [ABSTRACT FROM AUTHOR]