EVALUATION OF INORGANIC AND ORGANIC NUTRIENT SOURCE IMPACTS IN NUTRIENT TMDLS

There is a resurgence of interest in controlling the excessive fertilization (eutrophication) of surface waters in order to protect domestic water supplies and other beneficial uses of waters from impairment (pollution) by excessive growths of algae or other aquatic plants whose growth is stimulated by nitrogen and phosphorus. An area of particular concern is the nutrients added to waterbodies through the land application of inorganic fertilizers and management of domestic wastewater sludges (biosolids), animal manure, and compost that could lead to surface and ground water pollution. With the development of TMDLs to control excessive fertilization of waterbodies and the emphasis on protecting domestic water supply watersheds from pollution (source protection), the use of fertilizers as well as the regulation of the management of waste residues on land needs to be focused on controlling surface and ground water pollution. Those who fertilize lands as part of crop production as well those who dispose of waste residues (biosolids, animal manure, and compost) on land will be required as part of nutrient TMDLs to conduct comprehensive, reliable monitoring programs to ensure that the fertilizer nutrients and the constituents in the waste do not cause pollution – impairment of uses – of surface and ground waters associated with the waste management activities. The current federal and state regulatory agency guidance on management of biosolids needs to be amended to include a monitoring program to determine if nitrogen, phosphorus and, for that matter other constituents, in the biosolids cause surface or ground water pollution. It is important that the groundwater monitoring program be pro-active in detecting pollution before the groundwaters are polluted, such as through the use of unsaturated flow monitoring of the groundwater underlying the areas receiving the waste residues.This paper provides guidance on the use of the OECD eutrophication study results to evaluate the potential impacts of nutrient releases from agricultural lands and other sources on the eutrophication related water quality in many types of waterbodies. It also provides guidance on how to establish allowable nutrient loads to waterbodies to protect the eutrophication related designated beneficial uses. Particular attention is given to assessing the water quality significance of nitrogen and phosphorus present in stormwater runoff/irrigation return waters from the areas that receive land application of inorganic fertilizers and waste residues. It discusses monitoring programs needed to ensure that land application of inorganic fertilizers and waste residues do not cause or contribute to impairment of the beneficial uses of surface or ground waters for domestic water supply, for the propagation of aquatic life, and/or for recreational purposes.