Photo Credit: Virginia Department of Health

The concentration of chemicals to be added in the flash mix chamber is determined through a jar test in the lab, as shown above.  Jar tests simulate the conditions which the water will face as it passes through the flash mix, flocculation/coagulation, and sedimentation chambers.  Samples of water to be treated are placed in six jars and various amounts of chemicals are added to each jar.  The water is stirred and then the floc is allowed to settle.  The amount of each chemical which results in satisfactory settling and removal of turbidity in the water determines the amount of the chemical to be added to the water in the flash mix chamber.