Effects of Al3 + and hydraulic characteristics on the removal and behaviour of particles in dissolved air flotation

Abstract

The removal efficiency of the dissolved air flotation (DAF) process to separate particles from water and wastewater depends on the size and zeta potential of bubbles and particles, the solution and operating conditions, hydraulic characteristics, etc. The effects of aluminium ions and turbulent flow-produced when air-saturated water was spouted into the reactor in the DAF process, on removal and, particle behaviour were on investigated. When bubble size was similar to particle size (10–50 μm), the maximum removal efficiency was 92% in a Kaolin solution of 10−3 M Al3 + without pre-treatment for flocculation process, and, as time passed, the floc size was observed to increase at a pH of 8, which was the condition of high removal efficiency as seen through image analysis. When the air-saturated water was spouted into the reactor, the size of particle at p.z.c. (point of zero charge) seemed to increase to form a floc due to collision effects caused by turbulent flow. Consequently, floc formation by turbulent flow in the reactor seemed to positively affect removal efficiency.