An evaluation of DAF clarification laboratory test methods

Jar testing is commonly used to predict the clarification performance of process additives. Test results are usually given in terms of supernatant turbidity or total suspended solids (TSS). The level of precision for both measurements was established by extensive experiments with a variety of recycled-fiber process filtrates. The data demonstrate that manipulation of independent jar-test variables (shear rate, mixing time, settling time, temperature, and polymer dose) has a profound impact on the predicted performance of polymeric treatment systems. Experiments in a laboratory dissolved-air-flotation (DAF) tester were performed to compare the predictive capabilities of laboratory DAF testing and conventional jar tests. Laboratory DAF testing provided unique predictive capabilities not present in jar-test results. Nevertheless, jar testing remains a valuable primary tool for determining relative treatment performances. Application : the information will help research and technical personnel to perform more meaningful laboratory tests when screening additives for water clarification.