Under the Clean Water Act, states and authorized tribes are responsible for establishing water quality standards that specify appropriate designated uses, establish criteria to protect those uses, and provide for the protection of downstream waters. Nutrient regulation has been discussed at the national and state level for many years, but the problem is more difficult to define and solve than most of the previous water quality standards. Unlike most other regulated compounds, neither nitrogen nor phosphorus is toxic in the aquatic environment and presence of these compounds in limited amounts is necessary to sustain ecosystems. In addition, the treatment of nitrogen and phosphorus is extremely expensive at point source locations and very difficult to control at non-point source locations.
The passage of CDPHE WQCD Regulations 31 (Reg. 31) and 85 (Reg. 85) is Colorado’s solution to nitrogen and phosphorus regulation. The two regulations were passed simultaneously in March of 2012 to both establish scientifically based nutrient regulations and allow point source dischargers time to develop plans to begin treating both nitrogen and phosphorus. Reg. 31 is the Water Quality Control Commission document that establishes statewide water quality regulations for surface waters. Reg. 85 establishes requirements for organizations holding a NPDES permit and with the potential to discharge either nitrogen or phosphorus to begin planning for nutrient treatment based on treatment technology and monitoring both effluents and streams for nitrogen and phosphorus. The data from these efforts is designed to better characterize nutrient sources, characterize nutrient conditions and effects around the state and to help inform future regulatory decisions regarding nutrients.
Nutrient pollution resulting from excess nitrogen (N) and phosporus (P) is a leading cause of degradation of U.S. water quality. Nitrogen and phosphorus together support the growth of algae and aquatic plants, which provide food and habitat for fish, shellfish and other organisms that live in water. Excess N and P in aquatic systems can stimulate production of plant and microbial biomass, which leads to depletion of dissolved oxygen, reduced transparency and changes in biotic community composition. This effect is called eutrophication. In estuaries and coastal waters, nitrogen and phosphorus loading can cause hypoxic zones which are areas of extremely low dissolved oxygen.
Hypoxic zones can have severe impacts on fisheries in areas such as the Gulf of Mexico. Nitrogen and phosphorus can come from many sources including: • Fertilizers from agriculture, golf courses and residential lawns • Erosion of soil full of nutrients • Discharges from point sources such as domestic wastewater treatment plants • Deposition of atmospheric nitrogen (nitrogen only). Eutrophication became a more serious problem following the industrial revolution when the first inorganic fertilizers were created.
A few major scientific discoveries in plant growth indicated that additions of nitrogen, phosphorus and potassium could promote plant growth. Many of these fertilizers are made to dissolve quickly in water which can stimulate plant growth in gardens and farmer’s fields, but can also promote eutrophication in our nation’s waterways. Excess nitrogen can also cause degradation of aesthetics of recreational waters by turning the water green, often with layers of floating green scum. Health can also be affected when excess nitrogen appears in drinking water wells. Levels above 10 mg/L of nitrate can cause Blue Baby Syndrome which can prevent babies and small children from being able to uptake and process sufficient amounts of oxygen.