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Opportunities and Challenges for Managing Nitrogen in Urban Stormwater: A Review and Synthesis
Citation:
Collins, K. A., T. J. Lawrence, E. K. Stander, R. J. Jontos, S. S. Kaushal, T. A. Newcomer, N. B. Grimm, AND M. L. Ekberg. Opportunities and Challenges for Managing Nitrogen in Urban Stormwater: A Review and Synthesis . doi:10.1016/j.ecoleng.2010 (ed.), ECOLOGICAL ENGINEERING. Elsevier Science Ltd, New York, NY, 36(11):1507-1519, (2010).
Impact/Purpose:
To inform the public.
Description:
Although nitrogen (N) is prevalent in urban storm water, regulation of this pollutant has occurred only more recently. In this paper the concerns over N in urban storm water, mechanisms and design enhancements for N uptake and denitrification through various storm water control measures (SCMs), are reviewed and opportunities presented to integrate this current knowledge into the regulatory framework. A survey of personnel directly involved in various aspects of US state and territory NPDES programs revealed that the top three pollutants of concern were total suspended solids (TSS), pathogens and bacteria, and total phosphorous (TP). Surprisingly, nitrate (NO3-) was of little concern among the survey respondents, with 3.9% giving it the highest level of concern, 2.0% ranking it second, and 6.0% ranking it third. When asked which management strategies were currently used in their geographic area for storm water management, the most common results were wet ponds and dry ponds. At the same time, wet ponds and dry ponds were recognized as less effective practices to manage storm water. A review of current literature reveals that several alternative SCMs, such as bioretention, filters, and wetlands, show greater promise in their ability to remove N from storm water than more conventional practices such as dry ponds and wet ponds. Enhanced N removal via denitrification and plant uptake is often observed under the combination of aerobic followed by sustained anoxic conditions, the presence of a carbon source (organic material), and the presence of mature, dense vegetation. Given the lack of concern or awareness by local officials on N loading from urban storm water, and variation in the efficacy of various SCMs, it is not surprising that regulators remain focused on conventional dry pond and wet pond control measures. More needs to be done to quantify the impact of urban sources of N on water quality and aquatic ecosystems. In addition, greater focus needs to be placed on development of design criteria for SCMs, such as bioretention, filters, and constructed wetlands, which show more promise for N removal.
