Book 1 Ch 3 - Coagulation and Flocculation Practice Quiz Flashcards

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What is the proper range of microsand concentration for a ballasted flocculation process unit?

2 to 6 g/L


Very small, finely divided solids that do not settle due to their small size and similar electrical charge are called what?

Colloidal solids


A tank or zone where the water is gently mixed, allowing small particles to bump into each other forming larger particles is called what?

Flocculation tank


Changes to the source water that will require chemical adjustments of the coagulation process are increases or decreases in what water characteristics?

Color or alkalinity


Which of the following is considered a coagulant aid?

Bentonite clay


What is the cloudy appearance of a source water that is caused by the presence of suspended and colloidal matter known as?



The operator observes the floc as it enters the flocculation basins from the flash mixing zone. The floc is small and well dispersed throughout the flow entering the basin. This observation indicates:

Everything is just right


Why should the operator avoid adding microsand immediately near the
basin mixer?

Deflection and stress to the mixer impeller and shaft could damage mixer assembly


How often should jar tests be run?

Jar tests should be run at least daily and more often when the quality of the raw water changes


The operator observes the floc as it enters the flocculation basins from the flash mixing zone. The water has a milky appearance with a slight blueish tint. This observation indicates:

The alum dosage is too high


What is a process that uses microsand added to the flocculation stage to encourage floc settling called?

Ballasted flocculation


If an increase in turbidity or in the color of the raw water being fed to a ballasted flocculation unit occurs during normal operation, the operator should ensure that the microsand concentration is:

At the high end of the operating range


What test is performed by the water plant operators and plant engineers to determine which coagulant will work best for their water and what dosage of that chemical will produce the lowest turbidity and clearest water?

Jar test


With regard to a water's natural alkalinity, what condition could exist that would lead to incomplete precipitation of the aluminum sulfate (alum)?

Insufficient alkalinity leads to poor precipitation