Jar Test

A qualitative method used extensively in the water treatment industry is the jar test. In this test, environmental en-

O INORGANIC COAGULANT DOSE

FIG. 7.34.7 The effect of the liquid-solids separation technique on the coagulant dose required for efficient suspended colloidal material removal.

O INORGANIC COAGULANT DOSE

FIG. 7.34.7 The effect of the liquid-solids separation technique on the coagulant dose required for efficient suspended colloidal material removal.

gineers add different coagulant doses to several rapidly mixing samples of wastewater (usually ^1.5 l) and continue mixing for about 1 min. The sample is then slowly mixed (to simulate flocculation) for 10 to 30 min and allowed to settle quiescently for an additional 10 to 30 min. Environmental engineers then make qualitative observations such as time for visible floc formation, floc size, and floc settling rates.

They also make a direct or indirect measurement of the supernatant SS concentration. They approximate the coagulant dose requirement based on their judgement of these observations. The effective use of jar test information is an art and does not represent a true model of prototype operations.

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