Optimization of pre-oxidation enhanced coagulation for micro-polluted water treatment by response surface method

Taking the natural water in Anhui Polytechnic University as the research object, the removal of micro-pollutants in water body by KMnO₄ pre-oxidation enhanced polyaluminium chloride (PAC) coagulation process was studied. Firstly, the ability of different experimental schemes to remove turbidity, TP (Total Phosphorus) and UV₂₅₄ was investigated to determine the pre-oxidation scheme. Then, on the basis of the selected pre-oxidation scheme, the effects of the dosage of KMnO₄, dosage of PAC, pre-oxidation time and pH on the removal of pollutants were investigated. Taking removal rate of turbidity, UV₂₅₄ and TP as the response values, the response surface method (RSM) was used to investigate the independent and interactive effects of the dosage of KMnO₄ (A), PAC dosage (B) and pre-oxidation time (C). The technological parameters of KMnO₄ pre-oxidation enhanced coagulation treatment of micro-polluted water were optimized. The results showed that adding KMnO₄ for 5 min followed by adding PAC had the best treatment effect. The influence order is as follows: turbidity (B > A > C), UV₂₅₄ (B > C > A), TP (A > B > C). The optimal technology parameters predicted by the model are as follows: A is 0.886 mg/L, B is 47.498 mg/L, and C is 13.1 min. Under these conditions, the best removal rates of turbidity, TP and UV₂₅₄ were 92.43%, 86.25% and 40.6%, respectively, and the validated values were 92.51%, 88.67% and 41.32%, respectively. The deviation values from the model prediction are 0.07%, 2.42% and 0.72%.