Effect Of Tannic Acid Of Water On Enhanced Coagulation

The study mostly aimed at the effect of tannic acid on enhanced coagulation (EC).The effect of every water quality parameter on coagulation with simply PAC when there was tannic acid in water was studied. The results showed that PAC had its best dose range, 30 mg/L PAC was the best dose in this experiment, and PAC had better turbidity removal effect in neutrality and weak alkalinity and better organic matter removal effect in acidity; the increase of tannic acid was good for turbidity removal, and with the increase of tannic acid from 0 to 5 mg/L, turbidity of filtered water declined to 0.56 NTU, but the increase of tannic acid had no significant effect on organic matter removal; raw water quality had significant effect on removal efficiency of turbidity, but had no significant effect on removal efficiency of UV₂₅₄ and COD_Mn; raw water quality had no significant effect on residual turbidity, but had great effect on residual UV₂₅₄ and COD_Mn.The effect of tannic acid on preoxidation by potassium permanganate was studied. The results showed that preoxidation by potassium permanganate could enhance the removal efficiency of turbidity, UV₂₅₄ and COD_Mn, preoxidation by potassium permanganate could make UV₂₅₄ decline by 6～7% compared with PAC, and 30 mg/L PAC could make residual COD_Mn decline to 2.52 mg/L, but only 20 mg/L PAC could make residual COD_Mn decline to 2.48 mg/L in the condition of preoxidation by potassium permanganate, but the best dose of PAC didn't change; preoxidation by potassium permanganate had better effect in neutrality than in acidity and alkalinity; more tannic acid was good for turbidity removal when it was less than 2 mg/L, but too much tannic acid was bad for coagulation; the effect of raw water quality on coagulation in the condition of preoxidation by potassium permanganate was similar to coagulation with PAC: raw water quality had no significant effect on settled and filtered water turbidity, and residual UV₂₅₄ and COD_Mn increased distinctly with the increase of corresponding parameter of raw water, but removal efficiency had no significant change.The effect of tannic acid on prechlorination was studied. The results showed that prechlorination could enhance the removal efficiency of turbidity, UV₂₅₄ and...