What is the purpose of Jar Testing in water treatment?

• A. Determines optimum coagulant dose
• B. Measures pH levels
• C. Counts bacteria
• D. Tests chlorine residual

Answer: (A)

Jar testing is used to find the optimal coagulant dose for removing particles by simulating coagulation and flocculation on a small scale. In the test, you treat several water samples with different amounts of coagulant, mix them under controlled speeds, and then let them settle or be filtered to see how well the particles are removed. By comparing the clarity and settling of each dose, you pick the amount that gives the best turbidity reduction and stable floc without overdosing. This bench test helps predict how the full-scale plant will perform and can also explore how changes in mixing or pH affect performance. It’s not about measuring pH, bacteria counts, or chlorine residual, which are different tests.