Cost and Greenhouse Gas Emissions for a 220 mgd Facility to Attain 2 mg/L TN and 0.16 mg/L TP

Abstract

The Colorado Department of Public Health and Environment (CDPHE) recently proposed longterm nutrient quality goals of 2.0 milligrams of nitrogen per liter (mg-N/L) for total nitrogen (TN) and 0.16 milligrams of phosphorus per liter (mg-P/L) for total phosphorus (TP) for warm water streams in Colorado. The proposed regulatory initiatives will be considered by the Colorado Water Quality Control Commission at an upcoming rule-making hearing. To support testimony that the Metro Wastewater Reclamation District (Metro District) will present at that hearing, a Nutrient Quality Impact Report was prepared to quantify the cost and greenhouse gas (GHG) emissions associated with upgrading the Robert W. Hite Treatment Facility (RWHTF) to provide four levels of TP and three levels of TN reduction. The costs and GHG emissions associated with treatment to 2 mg/L TN are disproportionately high. Even if economic costs are not considered, it can be argued the power and chemical consumption, and resulting GHG emissions, are excessive for the marginal benefits that may be gained, and could result in a negative net environmental impact.