A two-stage statistical approach for optimizing phosphate recovery in a fluidized bed reactor

This study aims to optimize phosphate recovery from wastewater using a fluidized bed reactor through chemical precipitation. Phosphate is a nonrenewable resource, and its overexploitation disrupts the natural phosphorus cycle, leading to water pollution via eutrophication. To achieve efficient recovery, a two-stage experimental design was employed: the Plackett-Burman design for screening significant parameters and the Box-Behnken design for optimization. Key parameters included pH, temperature, flow rate, initial phosphate concentration, and the molar ratio of calcium to phosphate ions ([Ca]/[P]). The results indicated that the most influential factors were the [Ca]/[P] molar ratio, pH, and temperature. Under optimal conditions; [Ca]/[P] molar ratio of 2.25, pH of 9, and temperature of 40 °C; the maximum phosphate recovery efficiency reached 94.38%. The recovered phosphate was characterized as hydroxyapatite (Ca5(PO4)3OH), a stable and reusable form of calcium phosphate. Unlike struvite-based methods, which often necessitate higher phosphate concentrations, expensive magnesium additions, and present operational challenges, this approach achieves effective recovery from wastewater using accessible calcium sources and minimal chemical inputs. These findings highlight the effectiveness of the fluidized bed reactor for sustainable phosphate recovery, supporting a more sustainable and economically viable solution for phosphate management and reducing environmental pollution.