Decontamination Features and Mechanism Research of Copolymerization Dissolved Air Flotation Process

Abstract

In the traditional dissolved air flotation (DAF), micro bubbles generally cannot mesh and adhere to particles efficiently, and the adhesion between microbubbles and particles is not stable, either. In this paper, a self-developed copolymerization dissolved air flotation (Co-DAF) system was proposed to strengthen the copolymerization of condensation reaction during the adhesion of bubbles and flocs, by grading the refluxed dissolved air water, which could significantly enhance the adhesion efficiency and the stability of the bubble-flocs. On this basis, raw water of low turbidity, high algae and high organic contents from the Yellow River reservoir was used as the water supply to verify the effectiveness of the proposed system. The results showed that the average removal rate of turbidity was 95.2%, among, which 93.6% of the particles larger than 2 μm were removed effectively. Meanwhile, the removal rates of CODMn, UV254, DOC, SUVA and ammonia nitrogen were 43.2%, 48.5%, 38.2%, 20.5 and 77.3%, respectively, and those of organics with molecular weight between 3000–10000 Da and more than 3000 Da were 30.6% and 85%, respectively. However, for those organics with molecular weight less than 1000 Da, only a removal rate of 10% was achieved. During the test, DBPFP could be well controlled by the Co-DAF process, and the removal rates of CHCl 3, CHClBr2, CHCl 2Br and CHBr3 were 22.9%, 21.9%, 16.0% and 18.2%, respectively. It was deduced that the mechanisms of removing pollutants by the Co-DAF process mainly included the collision and adhesion effects between micro bubbles-floc particles, the copolymerization between microbubble-flocs and particles, and the adsorption bridging effects among bubble-flocs, microbubbles and particles.