The Effectiveness of Polyacrylamide in Reducing Turbidity Caused by High Clay Sediment: A Study of the Impacts of Blends, Mixing, and Sediment Concentrations

Polyacrylamide was studied for its efficacy in reducing turbidity. The purpose of this research was to determine optimum conditions for 10 blends of PAM to reduce turbidity from construction site runoff. The research was based on 10 different PAM blends, researching concentrations (0, 1, 5, 10 ppm), PAM forms (dry granular or solution), mixing powers (80 and 150 rpm), and mixing times (1 and 2 minutes). The research was conducted in a laboratory setting using a PB-700TM Standard Jar Tester (Phipps and Bird, Richmond, Virginia) with a clay texture sediment source. The claytextured sediment source was researched under two sediment-water concentrations of 2,000 and 10,000 parts per million (ppm). For non-polymer control, each sediment concentration was mixed for five minutes to ensure complete mixing. One minute after the cessation of mixing, turbidity measurements were taken on time intervals of 0.5, 2, 5, and 10 minutes. Using these same samples, polyacrylamide was then added to the sediment-water solution. Three replicates of the various treatment conditions, and similar turbidity measurements were then taken.

The data showed the most key aspects, on the average at reducing turbidity the greatest, were the dry forms of PAM for the 2,000 ppm sediment-water concentration and the solution forms of PAM for the 10,000 ppm sediment-water concentrations. Turbidity reductions were not as dramatic with the dry from of PAM, at the lower mixing power, with the shorter mixing time, at low PAM concentrations.

The data also provided evidence that all PAM blends demonstrate different turbidity reduction under different treatment combinations. This information shows the important issue that PAM is not exactly 100% PAM and each PAM product (blend) are very soil dependent. This key issue needs to be considered when a PAM product is applied in any form or fashion.