Evaluation of an Integrated Tertiary Treatment System for Ultra-Low Level Phosphorus Removal in Hayden, Idaho

The Hayden Wastewater Treatment Plant process consists of a headworks, equalization, enhanced biological nutrient removal, oxidation ditches, and secondary clarifiers. The facility produces typical effluent total phosphorus (TP) concentrations in the range of <1.0 mg/L as P. However, during upset conditions, these effluent concentrations can often increase to values upward of 5 mg/L TP. In 2022, the WWTP will be subject to a more stringent NPDES permit standard, which correlates to a new target effluent value of 0.035 mg/L TP. Various physico-chemical based unit processes were considered for their ability to consistently meet these requirements, and the selected Integrated Tertiary Treatment (ITT) System process includes solids contact clarification (SCC) and ultrafiltration (UF). The ITT System and a unique collaborative design approach was selected following evaluation of existing infrastructure and current plant conditions. An 18 week pilot was used to verify phosphorus removal by SCC and UF under a wide range of influent phosphorus conditions. Additional scenarios were also tested to evaluate the impact of pretreatment on UF system operation, as well as overall phosphorus reduction. These included SCC upset conditions, UF without SCC pretreatment, and varied doses of coagulant. Notably, this pilot demonstrated that the targeted effluent phosphorus concentration of 0.035 mg/L as P was achievable under all feed conditions, including total phosphorus as high as 8.44 mg/L as P. Final average filtrate phosphorus values were achieved with and without SCC pretreatment as 0.016 mg/L TP and 0.024 mg/L TP, respectively.

This presentation is available to AMTA Members only.