Optimization of turbidity and iron removal process for mine reuse water based on response surface methodology

Response surface methodology(RSM) was used to optimize the turbidity and iron removal coagulation process for coal mine reuse water. On the basis of single-factor experiments, pH, coagulant dosage and aeration time were selected as influencing factors, turbidity removal efficiency and total iron removal efficiency were taken as the response values, three-factor three-level experimental design was carried out by using Box-Benhnken design(BBD), to study the effects of individual and interactive interactions between the respective variables on the response values. The results showed that each factor had the following effects on turbidity removal efficiency of aeration time>pH>coagulant dosage and on total iron removal efficiency of pH>aeration time>coagulant dosage. According to the fitted quadratic regression equation, the optimal condition was determined with the coagulant dosage of 84.9 mg/L, pH of 6.8 and aeration time of 7.3 min. According to the actual operating conditions, the best conditions for coagulation experiments were modified as pH of 6.8, coagulant dosage of 90 mg/L, and aeration time of 7 min. Three sets of parallel experiments were carried out under the optimal condition,the average removal rates of turbidity and total iron were (97.2±0.3)% and (97.0±0.2)%, which were both deviated from the model predictions by 0.6%. The water quality of reclaimed water was favorable after the application while the operation cost could be saved.