Application of response surface methodology (RSM) to optimize chemical phosphate precipitation from phosphorus enriched supernatants of a SBR at anaerobic stage.
Abstract:Ferric salt was used as precipitator for phosphorus removal from supernatant of a SBR at anaerobic stage to recovery phosphorus source. To reduce adverse effect of chemical residue on the microorganism and reclaim phosphorus resources as much as possible, Box-Benhnken center combination experimental principle and response surface methodology were adopted, rations of dosage of ferric salt to that of phosphate, agitation speed, flocculation reaction time were chosen as independent variable and residual ferric ion concentration for response value to explore the interaction among those parameters in this study. With the aid of Design-Expert 8.0 software, a quadratic curved surface model was obtained. The result showed that the optimum conditions to be a dose of 1.40:1molar ratio of ferric ion to phosphate, stirring intensity for 275r/min with 30s in coagulation and 60r/min with 18min in flocculation, and precipitation time of 20min. The residual iron ion concentration could be kept at 0.37mg/L, and the efficiency of phosphorus removal could be achieved more than 97.66%.