Topic 1: Coagulation and Jar Testing

June 3, 2017

Jar testing is a great way to introduce students to coagulation theory and also for students to get comfortable in the research lab. This is also an opportunity for students to get familiar with standard instruments used in water treatment such as pipettes, pH meters, turbidimeters, and of course the jar tester. At this point, the students are given an experimental plan and simply follow a step-by-step procedure.

 

The primary objective of this experiment was to 1) to identify optimum aluminum sulfate coagulation conditions for a synthetic water using a jar tester and 2) identify distinct zones for the two primary mechanisms of coagulation, i.e. charge neutralization (CN) and sweep flocculation (SF). The alum dose typically ranges from 0 to 100 mg/L as alum while the target coagulation pH is varied from 5.5 to 8.0 in 0.5 unit increments.  A standardized jar test procedure was followed which included a rapid mix stage, 3 flocculation stages, and a settling period. The students collect raw water and settled water turbidity samples and use the percent reduction of turbidity to compare the results of a given coagulant condition, i.e. dose and coagulated pH.  Below is an example of the results obtained by the students:

 

Spring 2016 Results

 

 

 

 

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