| Water treatment residual solids are produced at surface drinking water treatment plants around the world. Coagulants (aluminum sulphate, ferric sulphate, or ferric chloride) are added during the coagulation step of the treatment process and large amounts of residuals are produced. These residuals typically contain metal hydroxides, chemicals that are added during coagulation (polymers or lime agents), organic and colloidal matter, pathogens, and any other constituents that are removed during coagulation. While coagulation is typically performed to reduce total organic carbon in surface water, other specialized uses for coagulants include phosphorus and arsenic removal.;The reuse of water treatment residual solids as a water treatment material provides a two-fold benefit to the water industry, by creating an opportunity to re-use a waste product that is commonly disposed of in a municipal landfill, and providing an option for re-use within the water and wastewater industry. Overall, iron-based residual solids were a better adsorbent for phosphate and arsenate, achieving higher levels of adsorption and better adherence to Langmuir isotherm modeling in all experiments. A chemical characterization showed that iron residual solids contained more elemental metal than the alum residual solids, and a physical characterization showed evidence of smaller pore sizes in the iron residual solid. Therefore, better phosphate or arsenate adsorption by the iron residual solids compared to the alum residual solids can be attributed to the affinity of iron for phosphate or arsenate, the greater amount of iron per solid, and the smaller pore structure in the iron residuals.;This thesis involved the development of a novel adsorbent media, water treatment residual solids, for the removal of phosphorus from agriculture wastewater and the removal of arsenic from groundwater. The experimental protocol involved four separate but similar tasks: to investigate phosphate adsorption using water treatment residual solids in batch adsorption experiments, to investigate arsenate adsorption using water treatment residual solids in batch adsorption experiments, to investigate arsenic adsorption from groundwater in batch adsorption and column adsorption experiments, and to investigate the mechanisms for phosphate arsenate adsorption on water treatment residual solids, including a chemical and physical characterization of the residual solids. |
