modeling of phosphorus chemical precipitation in aqueous solutions using response surface methodology

Phosphorus is one of the main limiting factors for eutrophication in water resources. according to the increasing population and the worsening of the healthy water shortage crisis in recent years, it is necessary to control the concentration of this element (phosphorus) in water resources. this study was performed with the aim of phosphorus removal efficiency (pre) and sludge volumetric index (svi) modeling in the chemical precipitation process, and by using poly-aluminum chloride as a precipitator. in this study, the response surface method (rsm) was used based on the central composite design (ccd) to model the effects of ph, the precipitator concentration, mixing time, mixing speed, settling time, and phosphorus initial concentration on the two desired answers including pre and svi. analysis of variances (anova) of the responses showed that among the above factors, precipitator concentration, phosphorus initial concentration, and settling time on phosphorus removal efficiency has been significant. also, the most important parameters affecting the sludge volume index were precipitator concentration, settling time, and ph. phosphorus removal efficiency and sludge volume index under optimal condition (ph=7.46, poly-aluminum chloride concentration=104.85 mg/l, mixing time=133 s, mixing speed=152 rpm, settling time=36 min and phosphorus initial concentration= 6.33 mg/l) was predicted to be 84.68% and 151.79 ml/g, respectively. based on the average responses obtained from three times experiment under predicted optimized conditions, the phosphorus removal efficiency was 80.03%, the sludge volumetric index was 200.07 ml/g. the predicted and obtained data from the experiments showed conformity, which indicates the accuracy of modeling. the findings of this study showed that the factors of precipitator concentration, settling time, and ph should be well controlled to manage the chemical precipitation process using poly-aluminum chloride.