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Update on Jordan Lake Nutrient Management Strategy <br />September 17, 2004 <br />Page 3 of 5 <br />August 18, 2004 stakeholder meeting, when seiuor DWQ staff announced their intention <br />to recoimnend that the EMC pursue a phased or "adaptive management" approach to the <br />nutrient reduction goals. Rather thair immediately imposing more stringent TN and TP <br />limits for wastewater dischargers, it is DWQ's intent to phase in these limits by 2011. In <br />the meantime, additional monitoring, technical evaluation, potential nutrient "trading" <br />among sources, etc. could result in modified reduction goals, <br />Implications for OWASA <br />The most important issue for OWASA will continue to be the degree of TN and TP <br />removal required at the Mason Farm Wastewater Treatment Plant. Currently <br />programmed improvements and the capacity expansion to 14.5 million gallons per day <br />(mgd) have been designed in anticipation of this regulatory process, and will <br />satisfactorily achieve the level of TN and TP reductions that DWQ staff has proposed for <br />the Upper New Hope Arm, assuming plaint flows of up to 14.5 mgd. <br />Historically, wastewater discharges have been regulated on a concentration basis; e.g., <br />pounds (or milligrams) of pollutant per gallon (or liter) of effluent, A facility is deemed <br />in compliance if it meets these concentration limits, regardless of whether it produces a <br />large or small volume of wastewater. OWASA's new TN and TP limits for the Mason <br />Farm Plant - as well as the new TN and TP limits for Durham and Durham County's <br />wastewater treatment plants -are based on annual mass load, rather than concentration <br />limits. This means that the total mass of TN or TP discharged during a calendar year <br />cannot exceed a specified aznount. Daily loads (and concentrations) may vary - as long <br />as the total pounds of TN or TP do not exceed the specified limit at the end of the year. <br />Existing and proposed mass loads limits, along with the equivalent concentrations that <br />correspond to a range of existing and future wastewater flows, are presented below.. <br />Table 1. <br />Annual Mass Load Limits and Effective Concentrations <br />Under AWASA's Exiting NPDES Permit (NG0025241) <br />Permitted Total N itrogen Total Phos horns <br />Flow Mass Load Limit Concentration Mass Load Limit Concentration <br />(MGD) (Pounds) (mg/L) (Pounds) (mg/L) <br />12.0 409,448 11.21 11,030 0.30 <br />14.5 409,448 9.28 11,030 0.25 <br />18.5 409,448 7.27 11,030 0.20 <br />22.5 409,448 5.98 11,030 0.16 <br />q <br />