Tertiary Membrane Filtration: A How-To Guide on Operation and Expansion from Coeur d'Alene, Idaho

A dissolved oxygen TMDL wasteload allocation for dischargers to the Spokane River lead to a seasonal effluent phosphorous limit of 0.05 mg/L for the city of Coeur d’Alene, Idaho. The City operates a tertiary membrane filtration (TMF) process at their Advanced Wastewater Treatment Facility (AWTF) in order to achieve these stringent limits. A multi-year, incremental effort towards compliance involved persistent attention from operations staff through a 189,271 LPD (50,000 GPD) demonstration pilot, construction and operation of a 3.79 ML/d (1.0 mgd) facility, and then expansion of the facility to 18.93 ML/d (5.0 mgd). Sewer rates for the service area are only $35 per household, which is lower than many of the nearby municipalities with comparable effluent limits. The AWTF currently produces effluent total phosphorus less than 0.05 mg/L and ammonia concentrations less than 0.1 mg/L. Operators and engineers had to successfully navigate operational challenges in order to achieve these results.