Development of Best Management Practices for Turbidity Control During Rainfall Events at Highway Construction Sites using Polyacrylamide

The motivation for this project stemmed from AHTD’s need to develop a treatment process for turbid water collected onsite in sedimentation basins at highway construction sites. These waters may have high turbidity that does not decrease appreciably with time, due to high particle stability and slow particle settling times. Through a series of lab-­‐ and field-­‐scale experiments, the Project Team determined that PAM infused floc logs – acquired from Applied Polymer Systems (APS), Inc. – can be used in onsite sedimentation basins to reduce the turbidity of runoff waters by 95-­‐99%. However, inline treatment (i.e., turbid water flowing over floc logs) was found to be ineffective, likely due to a lack of sufficient mixing between particles and the PAM. The selection of the particular type of floc log can be made based on results from standardized jar tests with soil samples from the active field sites. However, if jar tests are impractical in a given situation, multiple floc log types (i.e., APS 703d, 703#d, and 706) can be used in a single basin. An individual floc log ($70-­‐$80 USD in 2016) is capable of treating at least 16,000 L (565 ft³) of turbid water under the following conditions, which include (1) Floc log must be pre-­‐soaked in water for 15 minutes prior to use in the sedimentation basin, (2) the floc log is submerged into the sedimentation basin containing the turbid water and rapidly mixed using a submersible pump of at least 15 minutes; one pump should be used for every 2,000 L (71 ft³) of turbid water to generate adequate contact between the floc log and the particles causing the turbidity; mixing times should be increased proportionally for large water volumes, (3) following the rapid mixing period, the floc log is removed and turbid water is allowed to settle for at least 5 minutes without any mixing, (4) following the settling period, the low turbidity basin water can be released (or pumped) offsite into streams, ponds, or drainage ditches. The floc logs can be reused following cleaning to remove caked-­‐on particles. This cleaning can be as simple as scraping and/or rinsing the floc logs and need not remove all particles. No limit to floc log reuse was found in this study.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Figures; Photos; References; Tables;
  • Pagination: 72p

Subject/Index Terms

Filing Info

  • Accession Number: 01732530
  • Record Type: Publication
  • Report/Paper Numbers: AHTD TRC 1403, TRC1403
  • Contract Numbers: TRC1403
  • Files: TRIS, ATRI, STATEDOT
  • Created Date: Feb 28 2020 5:12PM