Despite decades of regulations governing point of use dischargers, U.S. streams and rivers are still polluted by nitrogen and phosphorus. In fact, a recent study by the U.S. Geological Survey found that the amount of nitrogen and phosphorus have remained the same or increased in many streams and aquifers across the United States since the early 1990s.
According to the U.S. Environmental Protection Agency, nutrient pollution has consistently ranked as one of the top three causes of degradation in U.S. streams and rivers for decades.
USGS findings show that nitrogen and phosphorus remain two to 10 times greater than levels recommended by the EPA in many areas across the country. Most often, elevated levels were found in agricultural and urban streams.
The study also found that nitrate is a continuing human-health concern in many shallow aquifers across the nation that are sources of drinking water. In agricultural areas, more than one in five shallow, private wells contained nitrate at levels above the EPA drinking water standard. The quality and safety of water from private wells -- which are a source of drinking water for about 40 million people -- are not regulated by the Federal Safe Drinking Water Act and are the responsibility of the homeowner.
Because nitrate can persist in groundwater for years and even decades, nitrate concentrations are likely to increase in aquifers used for public drinking-water supplies during at least the next decade, as shallow groundwater with high nutrient concentrations moves downward into deeper aquifers.
USGS findings show that nutrient sources and resulting concentrations vary across the nation. For example, concentrations of nitrogen generally are highest in agricultural streams in the Northeast, Midwest, and the Northwest. Concentrations of nitrogen in streams draining parts of the agricultural Midwest are higher because of artificial subsurface tile drains used to promote rapid dewatering of poorly drained soils.
A variety of sources can contribute nutrients in surface and groundwater, including municipal wastewater and industrial discharges, fertilizer and manure applications to agricultural land, runoff from urban areas, and atmospheric sources.
The USGS assessment clearly demonstrates the need for improved land management strategies and water resource management. The water industry and regulators have talked for years about focusing on watershed management, but there is much work to be done on so many levels.
Farming practices are a major culprit and that industry is virtually untouchable because of a strong lobbying arm. I don't see significant action in that arena happening in my lifetime. Obviously homeowners and their use of fertilizer to keep lawns green are a culprit, as are CSOs and SSOs. Treatment of stormwater in urban areas might help, but the cost is scary to even contemplate. Stricter discharge limits for POTWs could help to some degree, but again cost is a major issue. New technologies that capture phosphorus for beneficial reuse offer promise, but are still in the early stages of acceptance.
In the end, massive project funding, changes in farming practices and an informed public motivated to change are all required to counter this issue. Unfortunately, none of that seems likely in the foreseeable future.
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