ICL asked and IDEQ listened. In response to requests made by ICL, the Idaho Department of Environmental Quality has included more stringent nutrient standards in a permit seeking to apply treated municipal wastewater to 41 acres of forested land near Hope, ID.
The permit belongs to the Ellisport Bay Sewer District, which handles municipal wastewater from the communities of Hope and East Hope along the northeastern shores of Lake Pend Oreille. Ellisport’s treatment site is located next to Hope Elementary School, a school with a history of elevated nitrate concentrations in its well. Although the nitrate concentrations in the school’s well meet state regulations for drinking water, the cause of past elevated nitrate concentrations remains unclear.
Nonetheless, ICL was ardent that the most stringent limits be included in the permit, given the proximity of the wastewater treatment site to the school. IDEQ agreed with our request and has updated the permit to more stringently limit nitrogen and add a limit for phosphorus, which previously was excluded from the permit.
How Does the Wastewater Treatment Process Work?
Small municipalities often use land application of treated wastewater as the last step in a treatment process. Treated wastewater still contains high amounts of nutrients such as nitrogen and phosphorus. Irrigating agricultural or forested land with treated wastewater allows vegetation to absorb the nutrients and thus lower their concentration in the water. Balance is critical, though, to avoid overloading a vegetated area’s capacity to absorb nutrients from the wastewater.
What’s the Hazard?
Nutrients that are not absorbed by vegetation ultimately end up in our sources of drinking water, such as groundwater or a nearby surface water body. Excessive nutrients in drinking water can have a number of harmful side effects on humans, particularly for sensitive populations such as infants. Harmful algal blooms that are dangerous to human, plant and animal life can also occur if excess nutrients flow into a surface body of water. The best way to prevent these hazards is to reduce the amount of nutrients entering these precious resources in the first place.