Wastewater sludge conditioning by fly ash

Conditioning wastewater sludge from the City of Regina Wastewater Treatment Plant by fly ash from Boundary Dam Power Station, Saskatchewan, Canada, was studied. Toxicity characteristic leaching procedure (TCLP), equilibrium leach test (ELT), and long-term leaching test (LTLT) were used to investigate the leachability of heavy metals. Results from these leaching tests indicated that, on the basis of concentrations of microorganisms and heavy metals (Cd, Cr, Cu, Ni and Zn), the sludge produced at the Regina Wastewater Treatment Plant conditioned by the locally available fly ash can be disposed of in landfills and used as a soil conditioner for land application. Sorption, and silicate and hydroxide precipitations were considered to be the three important mechanisms in fixation of heavy metals. High pH conditions were considered to be the predominant mechanism in killing microorganisms.