A Critical Study on Operational Feasibilit Development of Aluminium Dross to Treat Pollutants of the Aqueous Environment : Waste Reuse for Resource Recovery

The need to reduce eutrophication in water bodies and the depletion of phosphate rock reserves have prompted the search for sequestration and recovery of phosphate from alternative sources, such as effluent. In this investigation, aluminium dross (AD), an industrial waste encapsulated in calcium alginate (Ca-Alg) beads, was used for phosphate removal. The removal of phosphate was evaluated both in batch and continuous operation modes. In addition, two prototype scale studies utilizing actual municipal wastewater have been conducted: (i) constructed wetlands (CWs) followed by Ca-Alg-AD beads based fixed bed and (ii) Ca-Alg-AD beads based free water surface (FWS) CW assembly. The bulk adsorption study revealed that 96.86% of the initial 10 mg/L phosphate concentration was removed in 70 minutes. Multiple characterizations, were performed in order to comprehend the influence of surface properties on the phosphate adsorption behavior. In addition, data analysis indicates that phosphate adsorption on Ca-Alg-AD beads follows a pseudo-kinetic model of second order and is best described by the Freundlich isotherm with regeneration capacity up to five consecutive adsorption-desorption cycles. In a 30-day pilot scale experiment, constructed wetlands (CWs) followed by a Ca-Alg-AD bead-based fixed bed system removed an average maximum of 85 0.41 percent phosphate while simultaneously removing 93.4 percent ammonium (in a regenerated column). In addition, the Ca-Alg-AD bead-based FWS CW assembly exhibited a maximal phosphate removal of 79 8.56 % and a simultaneous ammonium removal of 65.45 21 %. The algal growth control study demonstrated that the innovative Ca-Alg-AD-based FWS CW assembly is effective in remediating and upgrading eutrophic lentic water bodies such as lakes and ponds. The results validate the applicability of Ca-Alg-AD bead-based systems in the field. Ca-Alg-AD beads have been conclusively demonstrated to be effective for the imultaneous remediation and recovery of phosphate and ammonium from actual municipal wastewater and are therefore suitable for use as a wastewater treatment technology.