Nitrogen pollution of coastal waters is a significant concern in many areas of the northeast. As a result, many communities are receiving regulatory mandates to reduce man-made sources of nitrogen. To effectively control coastal nitrogen pollution, a holistic watershed approach is required.

Point and non-point nitrogen control

While much of the initial regulatory focus has been on requiring wastewater treatment plant upgrades to remove nitrogen, the nitrogen problem can be much bigger than the treatment plant discharges alone. The majority of the nitrogen pollution often comes from non-point sources such as septic systems, lawn and agricultural fertilizers, pets and farm animals, and air pollution from burning fossil fuels. To reach the desired water quality goals, a meaningful reduction in non-point sources of nitrogen will be required in many of the areas with nitrogen impairment.

Define the problem before attempting to solve it

An integrated watershed approach to nitrogen control requires:

  • A quantification of all the sources nitrogen inputs to the entire watershed;
  • An understanding of the fraction of each of the inputs that is removed as it travels through the watershed and of the total mass load of nitrogen that escapes to coastal waters; and
  • An understanding of the allowable nitrogen load to achieve the water quality goals.

Once this information is understood, the nitrogen removal requirements can be estimated and various nitrogen reduction strategies can be evaluated and prioritized based on cost effectiveness.

Nitrogen control strategies

The two broad nitrogen reduction strategies include reducing nitrogen inputs to the watershed and maximizing nitrogen storage and removal mechanisms to minimize the mass of nitrogen exported to the sensitive coastal waters. The are many strategies to reducing the amount of nitrogen exported from a watershed.

Optimum solutions are watershed specific

There can be a wide variation in the cost per pound of nitrogen removed by each of these strategies and these costs are watershed specific. To be successful in achieving non-point source nitrogen reduction goals, you need to be proactive in identifying cost effective solutions and in engaging the public and other watershed communities.

Ultimately, the optimum nitrogen control strategy is very watershed specific and is based on professional judgment that will need to be continuously refined based on observed water quality improvements via an adaptive management strategy.

Wright-Pierce has been at the forefront of integrated watershed planning for nitrogen control and is ready to assist your community to address this important environmental issue.