, designed by Gresham, Smith & Partners. Deicer runoff is passed through a bed of granular activated carbon, suspending and mixing the media. This allows microorganisms to grow on the entire outer surface of the carbon, which absorb the organic compounds from the deicer fluid and break them down. They convert the effluent to water, carbon dioxide, and methane, which then flow into a separator where gravity forces denser solids to the bottom, and lighter solids and water migrate to the top. The water is clarified and discharged.
After treatment, the system discharges the treated effluent to the Columbia River or to the sanitary system in compliance with permit requirements. On average, the new system will reduce discharge to the Columbia Slough by 89% and meet National Pollutant Discharge Elimination System permit requirements.
The entire process - storage, conveyance, treatment, and discharge - is remotely monitored using a Supervisory Control and Data Acquisition (SCADA) system. Specialized instruments monitor biochemical oxygen demand (BOD) to identify chemical concentration, flow rates, and permit limits. This real-time monitoring and automation helps plant operators determine and control the options for water storage, treatment, and release.