Florida Drinking Water Operator "B" Practice Test

What method can increase floc formation in the solids contact unit?

1. Reducing the flow rate of feed water

2. Recycling previously settled sludge

3. Adding more coagulants

4. Heating the water

The correct answer is: Recycling previously settled sludge

Recycling previously settled sludge in a solids contact unit is effective for increasing floc formation. When this settled sludge is reintroduced into the system, it provides a source of active microorganisms and floc particles that can enhance the coagulation and flocculation process. The presence of these already aggregated particles can promote additional particle interactions and agglomeration of incoming suspended solids, leading to improved overall floc formation. This method utilizes the natural microbial and chemical composition of the sludge that has already participated in the flocculation process, effectively amplifying the formation of larger and more stable flocs. This is crucial for enhancing sedimentation and improving the efficiency of the solids contact unit in water treatment processes. The other methods, while they may influence various aspects of treatment processes, do not directly enhance floc formation in the same way. Reducing the flow rate, for instance, might allow more time for flocculation, but it doesn't inherently add to the floc-forming agents already present. Adding more coagulants can sometimes lead to diminishing returns if not carefully managed, and heating the water could change the dynamics of particle interactions without specifically promoting floc formation. Thus, recycling settled sludge is uniquely advantageous for optimizing floc development.