A Comprehensive Model to Drive Down Costs in Denver

Since 2008, the Robert W. Hite Treatment Facility in Denver, Colorado, has maintained compliance with a 7-day average nitrate plus nitrite (NOxN) limit of 8.68 mg/L, and with seasonal ammonia limits ranging from 9.7 to 15 mg/L. In 2015, the facility must comply with more stringent ammonia limits, requiring the District to replace its existing high purity oxygen facility with a second biological nutrient removal (BNR) facility as part of an 800 million capital improvements plan. With multiple construction activities underway, decisions have to be made whether to budget millions of dollars for temporary chemical addition. The District staff must also develop strategies and initiate operation of a new centrate treatment facility. To help operators face these new challenges and to minimize operating costs, the District invested over 1 million in a plant-wide dynamic model in which consultants and District staff collaboratively for design, operations and planning. This paper will discuss sampling, model calibration and validation efforts, model applications and lessons learned.