Micro-polluted Raw Water To Strengthen The Study Of Coagulation Kinetics

The effect of the flocculation of flocculants polyaluminium chloride (PAC), poly ferric chloride (PFC) and polyacrylamide (PAM) with the water of Changjiang River and the Zixia Lake was studied. The effect factors included the dosage of flocculants, temperature, the pH and the agitation speed. According to the study, for the Changjiang River water, the optimum ratio of PAC\PFC and PAM is 30:1, and the flocculation rate was enhanced by increasing temperature. The flocculation efficiency could maintain high lever when the pH value was between 6.5 and 7.5. Within the range of which, the flocculation efficiency could be as high as 90% with the treatment of all the flocculants except PAM. As far as the Zixia Lake water was concerned, the flocculation rate was enhanced by increasing the dosage. The optimum condition for PAM was below 15°C and the pH value 7.5. But for PAC and PFC, the temperature below 20°C and the pH value between 5.0-7.0 was the best condition.In this paper, the flocculation kinetics of three kinds of flocculent and their combination was also studied with the laser particle size analyzer. It showed that, the growth process offloc in the early stage of flocculation could be described with the flocculation kineticequationlnN/N₀=-kt. In this equation, k means the initial rate constant of flocculation, thehigher k value was, the faster flocculation was, and vice versa. In practice, the condition of flocculation could be adjusted according to the k value. According to the influence of dosage to the flocculation efficiency and the characteristic of the particle in Changjiang River, it could be concluded that the flocculation of the particles in Changjiang River with flocculant's used in this paper followed the bridging mechanism and electric-counteract mechanism.