An engineering firm hired Clear Water Services to evaluate the efficacy of Chitosan Enhanced Sand Filtration (CESF) in treating stormwater runoff at a recycling facility in Washington State in order to reduce constituents to below NPDES permit benchmarks. Clear Water drafted a pilot-scale stormwater treatment plan detailing the system design, testing methods, and schedule. After sign-off, a 250 gpm CESF pilot system was mobilized and operated by Clear Water over a period of three months.

A third party collected water quality samples upstream and downstream throughout the testing process. The results showed that CESF treatment was successful in reducing turbidity, as well as copper, lead, and zinc to below the permit benchmarks. 96% of the particulate-borne metals and 55% of the dissolved metals were reduced through treatment. Turbidity was reduced to below 2.0 NTU on average.

Based on the demonstration of efficacy, Clear Water designed, manufactured, and mobilized a full-scale 400gpm CESF treatment system to meet the performance criteria of the pilot project along with stormwater conveyance upgrades at the site. Clear Water also provided a facility-specific Operations and Maintenance (O&M) manual and performed operations and maintenance for several years. After the first year of operations and ongoing testing, Clear Water was able to easily fine-tune the system to meet changing site conditions. The system has successfully treated and discharged over 50 million gallons of water and meets all benchmarks.