Determining Labile and Recalcitrant Organic Nitrogen for TMDL Projections, 2006 Engineering, Pulping, and Environmental Conference

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As part of a Total Maximum Daily Load Analysis (TMDL) of the Pearl River downstream from the Georgia-Pacific Monticello, Mississippi Mill, time-series biochemical oxygen demand (BOD) tests were run for 120-days. Following the completion of the tests, the results were analyzed using the Georgia EPD program LTBOD for the breakdown of CBODu and NBOD. During the course of the 120-day test, samples were collected for the analysis of TKN, ammonia-nitrogen, and nitrite+nitrate at days 0, 20, 45, 60, 75, 90, and 120. For the purposes of this paper, analyses for nitrite+nitrate will be assumed to contain nitrate and will be further designated as nitrate. The organic nitrogen was determined by subtracting the ammonia-nitrogen from the TKN. The organic-nitrogen remaining in the sample following the completion of the 120-day test was considered recalcitrant. On average, the samples had approximately 50% of the original organic nitrogen remaining. The recalcitrant organic nitrogen is not available for ammonification to ammonia, which in turn is not available for the deoxygenation of the river during the nitrification process. These results were used to reduce the impacts of organic nitrogen being converted to ammonia and subsequently asserting a DO demand in the Pearl River wasteload allocation model. The paper will discuss analytical and laboratory methods for determining recalcitrant nitrogen and give examples of the measurements from the Pearl River TMDL analyses for determining recalcitrant nitrogen.