Florida Drinking Water Operator "B" Practice Test

If jar test results show 80% of the floc has settled within 1-2 minutes after mixing stops, what does this indicate?

1. The coagulant dose is too high

2. The coagulation process is optimal

3. The coagulant dose is too low

4. Flocculation is ineffective

The correct answer is: The coagulant dose is too high

When jar test results indicate that 80% of the floc has settled within 1-2 minutes after mixing stops, this typically means that the mixing and coagulation process has been effective, allowing the floc to form and settle rapidly. The quick settling of such a significant portion of the floc generally suggests that the coagulant dosage is effective and may actually be on the higher end of the necessary range. In this context, it showcases the ability of the coagulant to promote rapid aggregation of particles, but if the settling is too fast, it may imply that the coagulant dose could potentially be excessive. An optimal coagulation process usually allows for a balance where floc is formed effectively and settles at a moderate rate, ensuring thorough treatment of the water particles without wastage of coagulant or potential operational issues. Therefore, while the results show a successful coagulation process, they also raise a red flag for the possibility that the coagulant dose might be higher than required for the water quality conditions being treated. An adjustment could be needed to improve efficiency and cost-effectiveness while avoiding overuse of chemicals.