Flocculated sediment and runoff quality improved by polyacrylamide

Kang, J., King, S.E., McLaughlin, R.A., & J.D. Wiseman (2014) Flocculated sediment and runoff quality improved by polyacrylamide. American Society of Agricultural and Biological Engineers Vol. 57 No. 3 Pages 861-867

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Abstract

Increasing regulations on construction site runoff requires improved sediment and erosion control practices, including the application of polyacrylamide (PAM) to enhance turbidity reduction. We evaluated water quality improvement and particle size distribution of suspended sediments affected by various types of passive PAM dosing under simulated stormwater flows. Three straw wattles were installed in a 7% sloped channel, and six different treatments were tested individually: (1) wattle with no jute netting and no PAM, (2) solid block PAM (BPAM) after the wattle + no jute netting, (3) granular PAM (GPAM) on wattles + no jute netting, (4) wattle + jute netting with no PAM, (5) wattle + jute netting where GPAM was applied to the wattle, and (6) wattle + jute netting where GPAM was applied to the jute netting. For each treatment, three repeated turbid stormwater flows were run in the channel, and water samples were collected from the entrance (influent) and exit (effluent) of the channel. There was no turbidity reduction with wattles and/or jute netting unless PAM was introduced to the channel system. The use of GPAM reduced effluent turbidity by 58% to 67% relative to influent, with the best treatment being GPAM on jute netting. The addition of jute netting to the GPAM + wattle treatment did not improve sediment reduction but did reduce turbidity. Applying GPAM to jute netting shifted the mean particle size from 24 to 211 µm and the 10th percentile from 1.6 to 66 µm, indicating the greatly increased particle size distribution of the flocculated sediment. This study emphasizes that the passive treatment of stormwater runoff using GPAM is a very effective method of flocculating sediments in turbid water.