Nutrient Aggregation


The Loading Tool provides the user with the option of calculating aggregated loads for nitrogen-containing parameters and phosphorus-containing parameters. This page describes the nutrient aggregation methodology and is an updated version of section 3.2.3 of the Technical Users Background Document.

Related Info

Nutrient aggregation approximates a Total Nitrogen and Total Phosphorus load by combining loads for various nitrogen and phosphorus species. Total nitrogen consists of organic nitrogen, ammonia, nitrate, and nitrite; or total Kjeldahl nitrogen (TKN), nitrate, and nitrite. Typically, organic nitrogen and TKN account for the majority of the total nitrogen load. As a result, if a facility is not required to report total nitrogen, TKN, or organic nitrogen; the loadings tool calculation will underestimate the aggregated nitrogen load. Phosphorus compounds may be reported as phosphorus or phosphate in ICIS-NPDES.

For nitrogen and phosphorus parameters, the Loading Tool calculates an aggregate nitrogen load and aggregate phosphorus load for each outfall and monitoring location at each facility using the following logic:

  • For Total Nitrogen (as N):
    • If Total Nitrogen is reported, use that load for total nitrogen;
    • If Total Nitrogen is not reported and TKN is > 0, then Total Nitrogen = TKN + Nitrate + Nitrite;
    • If TKN is not reported and Organic Nitrogen is > 0, then Total Nitrogen = Organic Nitrogen + Ammonia + Nitrate + Nitrite; and
    • If Organic Nitrogen is not reported, then Total Nitrogen = Ammonia + Nitrate + Nitrite
  • For Total Phosphorus (as P):
    • If Total Phosphorus is reported, then use that load for total phosphorus; and
    • If Total Phosphorus is not reported, then use the Phosphate load and convert to phosphorus

Table 3-10 presents the priorities that the Loading Tool uses to select nutrient parameters for inclusion in the total nitrogen calculation. Using these priorities, the Loading Tools selects one parameter to represent Total Nitrogen, TKN, Nitrate, Nitrite, Organic Nitrogen, and Ammonia.

Table 3-11 presents the priorities that the Loading Tool uses to select nutrient parameters for inclusion in the total phosphorus calculation.

 Table 3-10. Priorities for Nitrogen Aggregation
Parameter Code Parameter Description Conversion Factor Calculation Parameter Parameter Selection Priority
Equation 1: Total Nitrogen = TOTAL N
00600 Nitrogen, total (as N) 1 TOTAL N 1
51445 Nitrogen, Total 1 TOTAL N 2
51084 Nitrogen, total available (water) 1 TOTAL N 3
Equation 2: Total Nitrogen = TKN + NITRATE + NITRITE
00625 Nitrogen, Kjeldahl, total (as N) 1 TKN 1
51449 Nitrogen, Kjeldahl Total 1 TKN 2
51087 Nitrogen, Kjeldahl, total (TKN) (water) 1 TKN 3
82539 Nitrogen, Kjeldahl 1 TKN 4
49579 Nitrogen, total Kjeldahl 1 TKN 5
81639 Nitrogen Kjeldahl, total (TKN) 1 TKN 6
00623 Nitrogen, Kjeldahl, dissolved (as N) 1 TKN 7
00620 NITROGEN, NITRATE TOTAL (AS N) 1 NITRATE 1
71850 Nitrogen, nitrate total (as NO3) 0.225806452 NITRATE 2
51100 Nitrogen, total, as NO3, (water) 0.225806452 NITRATE 3
51086 Nitrogen, nitrate (NO3), (water) 0.225806452 NITRATE 4
00615 Nitrogen, nitrite total (as N) 1 NITRITE 1
51447 Nitrogen, Nitrite Total 1 NITRITE 2
00613 Nitrite, nitrogen, dissolved (as N) 1 NITRITE 3
71855 NITROGEN, NITRITE TOTAL (AS NO2) 0.304347826 NITRITE 4
Equation 3: Total Nitrogen = ORG N + AMMON + NITRATE + NITRITE
00605 Nitrogen, organic total (as N) 1 ORG N 1
00607 Nitrogen, organic, dissolved (as N) 1 ORG N 2
00610 Nitrogen, ammonia total(as N) 1 AMMON 1
51446 Nitrogen, Ammonia Total 1 AMMON 2
00609 Ammonia, nitrogen, total, (as N) 30 day 1 AMMON 3
00612 Nitrogen, ammonia, tot unionized (as N) 1 AMMON 4
34726 Nitrogen, ammonia, total (as NH3) 0.823529412 AMMON 5
51085 Nitrogen, ammonia, (NH3-N)(water) 0.823529412 AMMON 6
61574 Ammonia (as N) + unionized ammonia 0.823529412 AMMON 7
00619 Ammonia, unionized 0.823529412 AMMON 8
00608 Nitrogen, ammonia dissolved 0.823529412 AMMON 9
82230 Total Ammonia & Ammonium 0.823529415 AMMON 10
71845 Nitrogen, Ammonia Total (as NH4) 0.823529415 AMMON 11
00620 NITROGEN, NITRATE TOTAL (AS N) 1 NITRATE 1
71850 Nitrogen, nitrate total (as NO3) 0.225806452 NITRATE 2
51100 Nitrogen, total, as NO3, (water) 0.225806452 NITRATE 3
51086 Nitrogen, nitrate (NO3), (water) 0.225806452 NITRATE 4
00615 Nitrogen, nitrite total (as N) 1 NITRITE 1
51447 Nitrogen, Nitrite Total 1 NITRITE 2
00613 Nitrite nitrogen, dissolved (as N) 1 NITRITE 3
71855 NITROGEN, NITRITE TOTAL (AS NO2) 0.304347826 NITRITE 4
Equation 4: Total Nitrogen = AMMON + NITRATE + NITRITE
00610 Nitrogen, ammonia total (as N) 1 AMMON 1
51446 Nitrogen, Ammonia Total 1 AMMON 2
00609 Ammonia nitrogen, total, (as N) 30 day 1 AMMON 3
00612 Nitrogen, ammonia tot unionized (as N) 1 AMMON 4
34726 Nitrogen, ammonia total (as NH3) 0.823529412 AMMON 5
51085 Nitrogen, ammonia (NH3-N), (water) 0.823529412 AMMON 6
61574 Ammonia (as N) + unionized ammonia 0.823529412 AMMON 7
00619 Ammonia, unionized 0.823529412 AMMON 8
00608 Nitrogen, ammonia dissolved 0.823529412 AMMON 9
82230 Total Ammonia & Ammonium 0.776409915 AMMON 10
71845 Nitrogen, Ammonia Total (as NH4) 0.776409915 AMMON 11
00620 NITROGEN, NITRATE TOTAL (AS N) 1 NITRATE 1
71850 Nitrogen, nitrate total (as NO3) 0.225806452 NITRATE 2
51100 Nitrogen, total, as NO3, (water) 0.225806452 NITRATE 3
51086 Nitrogen, nitrate (NO3), (water) 0.225806452 NITRATE 4
00615 Nitrogen, nitrite total (as N) 1 NITRITE 1
51447 Nitrogen, Nitrite Total 1 NITRITE 2
00613 Nitrite nitrogen, dissolved (as N) 1 NITRITE 3
71855 NITROGEN, NITRITE TOTAL (AS NO2) 0.304347826 NITRITE 4

 

 Table 3-11. Priorities for Phosphorus Aggregation
Parameter Code Parameter Description Conversion Factor Calculation Parameter Parameter Selection Priority
Equation 1: Total Phosphorus = Phosphorus (PHOSP)
00665 Phosphorus, total (as P) 1 PHOSP 1
51451 Phosphorus, Total 1 PHOSP 2
70507 Phosphorus, in total orthophosphate 1 PHOSP 3
00670 Phosphorus, total organic (as P) 1 PHOSP 4
00662 Phosphorus, total recoverable 1 PHOSP 5
00666 Phosphorus, dissolved 1 PHOSP 6
Equation 2: Total Phosphorus = Phosphate (PO4)
00650 Phosphate, total (as PO4) 0.326315789 PO4 1
00660 Phosphate, ortho (as PO4) 0.326315789 PO4 2
00655 Phosphate, poly(as PO4) 0.326315789 PO4 3
71888 Phosphate, total soluble (as PO4) 0.326315789 PO4 4
70505 Phosphate, total, color method (as P) 0.326315789 PO4 5