Working to Achieve NALs: A Pilot Study Evaluating Use of Flocculant to Reduce Total Suspended Solids and Total Iron Concentrations at a Southern California Landfill
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Strategic approaches to industrial stormwater compliance and innovative treatment are one way to protect our waterways from the summit to the sea. Landfilling operations present a unique challenge to industrial stormwater practitioners in that the continual exposure and movement of soil more closely mimics activities and pollutants more commonly associated with construction sites.

Specifically, due to the nature of their operations, many landfills struggle to reduce total suspended solids (TSS) and total metals (especially naturally occurring iron) concentrations to below numeric action levels (NALs) in their stormwater discharges. At an active landfill in Southern California a pilot test was conducted to investigate the effectiveness of dosing stormwater runoff with flocculant prior to detention in an existing 2.5‐million gallon concrete‐lined basin as part of the facility’s ERA Level 2 Action Plan. The pilot study aimed to answer the question: Can flocculant application reduce the current minimum detention basin holding time required to achieve NALs for TSS and total iron at the compliance sampling point? After several failures and many lessons learned, the pilot test was successfully implemented and stormwater runoff was dosed according to the manufacturer recommended specification in March 2018. Preliminary results from the pilot test showed that TSS was reduced to below the annual NAL (100mg/L) within 18‐hours of application, while total iron concentrations were reduced by approximately 80% (from 22 mg/L to 4.1 mg/L) but remained above the NAL in the same period. Following nearly three weeks of settling, total iron concentrations remained slightly elevated (1.9 mg/L) compared to the NAL (1.0 mg/L).

Publication Summary

  • Geosyntec Authors: Julie Riggio
  • Title: California Stormwater Quality Association (CASQA)
  • Event or Publication: Event
  • Practice Areas: Stormwater and Integrated Water Resource Management
  • Citation: Riverside Convention Center
  • Date: October 15-17, 2018
  • Location: Riverside, California