c. Coagulation Dosage Test. The coagulation test enables the WPU operator
to determine the approximate dosage of ferric chloride for coagulation before starting
the erdlator operation, thus minimizing the number of adjustments during operation.
The test equipment includes four 200 ml jars with screw caps in a device that permits
inverting or shaking all jars together (see figure 5-14). The laboratory version of this
device includes several beakers with an electrically operated stirring device in each
beaker. The procedure is as follows:
All four jars to be tested are rinsed with water and filled to the 200 ml
Add one measuring spoonful (0.05 g) of pulverized limestone to each jar.
(3) Add 1 drop of FeCI3 solution (component of water quality control set) to
the first jar, 2 drops to the second jar, 3 drops to the third, and 4 drops to the fourth.
Cap all jars tightly and shake the entire unit vigorously for 15 seconds.
(5) Gently, agitate the solutions by inverting the entire unit for 5 minutes at
the rate of 7 to 10 inversions per minute.
(6) Allow the unit to stand for 5 minutes, observing the floc, its settling rate,
and the clarity of the water above the flocculent layer.
Figure 5-14. Coagulation dosage test equipment