Particle reduction study of flocculation mixing by means of grids

A flocculation study was completed by means of a vertically oscillating gri d mixing device. Five types of single grids with different solidity ratios were vertically oscillated inside a 2 L jar to promote flee aggregation. Ka olin was used as the simulated turbid particles and alum was applied as the chemical coagulant. The method of measurement was completed based on the p article reduction represented by the settled water turbidity. It was found that low turbidity readings could be achieved at a wide range of average vo lume velocity gradient (G) over bar, especially in the case of high solidit y ratio types of grids. This indicates that the grid mixing had a stable pe rformance and was not greatly affected by mixing variations in the vessel. The flee aggregation and erosion rate coefficient analysis showed that the grid mixing produced particle contacts with low break-up rate. A general re lationship among (G) over bar, flocculation performance parameters, and gri d physical characteristics was found, indicating that the flocculation perf ormance was easily controlled. This study has shown the potential of grids as a mixing device to produce an excellent mixing environment for flee aggr egation.