Value-Added Product from Water Treatment Waste Streams

Water treatment infrastructure is necessary to facilitate thriving human life, and as such, methods have been developed to ensure that water from various sources is made potable. One such process is the addition of metal salts, such as polyaluminum chloride (PACl), to the influent to facilitate particle coagulation and flocculation. This treatment process accounts for a large percentage of total particulate and turbidity removal from the water; however, the aluminum-based coagulation process yields sludge with high concentrations of aluminum as a by-product. Traditionally, the sludge is dewatered then shipped to landfill at the expense of the treatment facility. This places a financial burden on the treatment plant and incurs negative effects on the environment, such as leaching of metallic elements. Internationally, literature suggests that water treatment waste contains valuable chemical and mineral components which may be reclaimed and used to create a value-added product. Using water treatment residual (WTR) from the Buffalo Pound Water Treatment Corporation (BPWTC), which serves two of Saskatchewan’s largest cities, the authors will work in-lab to design a process to synthesize a viable product for future revenue generation. The most probable product choice is ceramsite, which is a heat-treated, porous material that can be used to remove contaminants from water. The WTR’s chemical composition lends itself to ceramsite creation, and the University of Regina possesses sufficient equipment to perform on-site experimentation and develop a product sample. Through our preliminary tests, the resultant ceramsite demonstrated the following physical properties: 24 h water absorption rate of 13–59% and compression strength of 0.26–18.57 MPa. Such results suggest that this waste-origin product can have high potential to be used for various beneficial purposes, such as adsorption media and construction material. This is deemed to be a noble and sustainable cause, as successful development of this WTR treatment process will divert sludge from landfill, directly protecting the local water table from potential metals contamination, while simultaneously abating the current expenses annually by BPWTP on sludge disposal.