Jar Testing – A Case Study
Recently, FCT Water engineers performed a jar test for a cheese manufacturing facility to determine the effectiveness of the company’s current wastewater treatment program, and attempt to provide a more optimal program. Jar testing proved to be a valuable method of gathering useful data used to improve the client’s water significantly.
What is Jar Testing?
A jar test is a small scale, benchtop procedure used to evaluate various combinations and doses of coagulants and flocculants. The purpose of the procedure is to estimate the minimum product doses required to achieve the customer’s water quality goals. The process involves taking several equally-sized water samples (in this case, four 1000 ml beakers) and applying different dosages of coagulant/flocculant to them and observing the results. In this specific instance, one sample is treated with the client’s existing coagulant/polymer combination to act as a control sample with which to compare the results of the other tests samples. After each round of 4 jars are completed, the data is evaluated to influence product selection and dose range for the next round of jars, ultimately repeating the process until the optimal combination is achieved.
Jar testing is a practical way perform water testing that could lead to more desirable water conditions. Optimizing a wastewater treatment program through the performance of jar tests can reduce chemical costs, reducing sludge volume, and ensure compliance with the facility’s discharge compliance.
The Test
The coagulation and flocculation are two separate processes that are used in succession to overcome the forces stabilizing suspended particles/solids in solution. Coagulation neutralizes the charges on the particles, creating what is sometimes referred to as ‘pin floc.’ Once the pin floc is in solution, the flocculant is added, in this case a polymer, that enables the pin floc to bind together, creating large groups of solids that are more readily removed from solution. Each jar is agitated, and the results observed and recorded.
The goal of this test is to find the lowest volume combination for coagulate and flocculate that provides the best results. Too much coagulant can cause the charges on the suspended solids to flip and no longer attract one another, leaving them suspended and unable to be effectively removed.
The Results
Several rounds of 4 jar test each were performed at this client. The first jar acted as the control group, using the same combination of coagulant/flocculant as the client, while the other jars contained new combinations that were to be tested. Eventually the ideal combination and dose was identified and confirmed through repeat jars to ensure repeatability. The successful jar achieved the best results as indicated by floc quality and water turbidity.