Polyacrylamide Blocks for Turbidity Control on Construction Sites

摘要

While polyacrylamide (PAM) has been proven effective in flocculating suspended sediment, practical methods for introducing it into stormwater to reduce turbidity have limited its use for this purpose. One approach has been to formulate PAM into a solid block, which is then placed in water conveyances where the passing flow dissolves the PAM and creates mixing and contact for flocculation to occur. Commercial PAM blocks were tested under simulated stormwater conditions to determine if this approach isviable. The blocks were placed in a 30 cm pipe into which different flows and sediment loads were introduced. The flow was then directed into sediment basins of various configurations. The PAM blocks reduced turbidity by 50-80% under most conditions. Basin configuration (baffles, outlet type) had relatively minor effects compared to the PAM effect. Turbidity was much higher and more difficult to reduce under cold water conditions, probably due to increased viscosity and reduced PAM reaction to suspended materials. Blocks which were allowed to dry between events were much less effective, at least for the 20-30 minutes of these tests. These results suggest that PAM blocks could be one method for reducing turbidity in stormwater runoff, but further testing under actual use will be needed.