Optimizing the processing conditions of ballasted flocculation of actual turbid river water

Ballasted flocculation is effective for fast turbidity removal in water treatment processes. However, there is a lack of specific information for setting the conditions for ballasted flocculation. To enhance the settling velocity and removal efficiency of ballasted flocculation of actual river water, the process parameters were examined at three turbidity levels. The optimum pH and dosages for ballasted flocculation were investigated based on the relationship between the water turbidity and the floc settling velocity at the three turbidity levels. A nonionic polymer flocculant was the most suitable for floc formation and achieved the lowest turbidity and highest settling velocity. Under the optimum processing conditions at the three turbidity levels, the treated water turbidity was ˂2 turbidity units (TU) and the floc settling velocity was ˃0.7 cm/s, which was 30 times that of conventional coagulation–sedimentation, reducing the floc settling time by 97% of those used in existing water treatment plants.