ASABE Technical Library - Abstract

Abstract. Significant turbidity reduction has been observed when applying granular polyacrylamide (PAM) to sediment tubes in both research and construction site settings. It has also been documented that when PAM gets wet and subsequently dries, this desiccation dramatically decreases turbidity reduction capacity. This physical process makes reapplication of PAM to sediment control practices necessary. However, there is a lack of research on the longevity of PAM in construction site environments. If PAM is re-applied to sediment tubes, how long can it remain viable on the tubes and still reduce turbidity when a runoff event occurs?

This question was explored through tests where simulated stormwater runoff was directed down a channel across four 50.8 cm excelsior wood sediment tubes. Tubes had an initial application of 100 grams of PAM to each tube before the first run for each test. PAM was reapplied after runoff events in order to investigate the effect on turbidity reduction of different time intervals between PAM reapplications and subsequent runoff events. Tests showed average effluent turbidities between 82 NTU and 477 NTU and reductions between 78% and 96%.

Results and statistical analysis from this study suggest that turbidity reduction capacity of PAM when first applied is no different than after a three-, five-, or ten-day waiting period between reapplication and a runoff event. Though not statistically different, two subsequent runs of the ten-day waiting period showed average effluent turbidities of 324 and 477 NTU, the highest observations for any treatment.