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Do you need consistent and reliable data for nutrient concentrations released by point-source dischargers? The USGS has developed a new approach for developing typical pollutant concentrations (TPCs) in the absence of measured total nitrogen (TN) or total phosphorus (TP) concentration data and a new tool, the Point-Source Load Estimation Tool (PSLoadEsT), for estimating TN and TP loads.

Try PSLoadEsT, a user-friendly interface for point-source dischargers that generates reproducible calculations of nutrient loads to streams.

PSLoadEsT, using TPCs developed by the new approach, was used to estimate point-source nutrient loads to streams of the conterminous United States for 2012. Annual total nitrogen (TN) and total phosphorus (TP) loads were estimated for all major point-source facilities (which comprise major wastewater treatment facilities (WWTFs) and some industrial facilities) and for minor WWTFs that discharged to streams in the conterminous United States during 2012. Although there are almost 3 times as many minor WWTFs as major WWTFs, the TN load contributed by major WWTFs to streams is about 15 times larger than that contributed by minor WWTFs. Similarly, major WWTFs contribute about 13 times more TP to streams than minor WWTFs.

A reliable method to estimate TPCs is critical. Of 16,967 point-source facilities analyzed for the estimate of 2012 point-source loads to streams, only 20 percent of TN values and 37 percent of TP values were measured concentrations. The TPC, which is estimated based on the type of treatment process, effluent, and industrial category, can be used to calculate nutrient loads from facilities that lack effluent nutrient concentration data.

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