Which treatment process uses jar test results to optimize chemical dosages?

• A. Sedimentation
• B. Coagulation/Flocculation
• C. Chlorination
• D. Filtration

Answer: (B)

The main idea is using small-scale trials to pick the right amount of coagulant so particles clump together effectively. In a jar test, you run several identical samples with different coagulant doses, then simulate rapid mixing to destabilize particles and slow mixing to encourage floc formation. You watch which dose produces the clearest supernatant and the strongest, settleable flocs without wasting chemical. The dose that gives good clarity and rapid settling at the lowest chemical use is your target for full-scale treatment. This step is all about coagulation and flocculation because it directly determines how much chemical is needed to bridge and aggregate the suspended solids. Other processes—sedimentation, disinfection by chlorination, and filtration—don’t use jar tests to set chemical dosages; they rely on physical settling, microbial killing, or filtration performance, respectively, after the coagulant-flocculation stage.