Massachusetts Wastewater Practice Exam

What occurs to floc when the mixing speed is too high in wastewater treatment?

1. Floc pins

2. Floc settles well

3. Floc forms larger aggregates

4. Floc becomes too small

The correct answer is: Floc pins

When the mixing speed is too high in a wastewater treatment process, floc can become pinned or captured in the turbulent conditions created by excessive agitation. This phenomenon occurs because the high energy inputs disrupt the delicate balance needed for floc formation and growth. Instead of allowing floc particles to aggregate and settle effectively, the rapid movement can cause them to be suspended in the liquid, preventing them from combining into larger, denser structures that are necessary for efficient sedimentation. The ideal mixing speed promotes the collision and bonding of particles to form larger floc, which enhances the settling process. However, when mixing is too vigorous, instead of forming larger aggregates, the floc can become fragmented or remain suspended. This compromises the efficiency of the treatment process since the floc must be able to settle out of the water to facilitate proper removal of contaminants. This dynamic illustrates the importance of optimizing mixing speeds in wastewater treatment to ensure that the benefits of floc formation are realized effectively.