Controlling nitrogen pollution

Posted on March 10, 2014

Because releases of nitrogen from farms and urban areas can lower water quality and oxygen levels in streams, several ways of reducing, intercepting and treating nitrogen pollution have been developed. Although these technologies are well-documented, there have been no attempts to synthesise information on their function, performance and costs for the benefit of environmental managers. A recent wide-ranging review remedies this deficiency and makes the point that the optimum nitrogen-control strategy for a given situation will depend on the nitrogen source, local hydrology, land use, land availability, and the project budget. If there is a single major nitrogen source, the most appropriate approaches are advanced septic systems (for example, to reduce nitrogen flows from housing developments to nearby waterways), bioretention cells, permeable reactive barriers (e.g., biowalls around farm silos) and treatment wetlands for industrial and urban effluent with low to moderate levels of suspended solids. If the potential sources of pollution are more diffuse, options for nitrogen removal include low impact designs such as green roofs and permeable pavements , treatment wetlands, managed riparian buffers (which offer cost and habitat benefits as well as high removal efficiencies), and stream restoration, where nitrogen removal is part of a broader design strategy. A combination of these techniques is likely to be more efficient than just one. The review makes four recommendations for future action, namely : (1) more interaction between engineers and scientists; (2) standardisation of indices used to assess costs and nitrogen removal efficiency; (3) more research on underlying processes; and (4) better economic and ecological assessment of environmental tradeoffs.

Reference: Passeport, E. et al. 2013. Ecological engineering practices for the reduction of excess nitrogen in human-influenced landscapes: a guide for watershed managers. Environmental Management 51,:392–413.