Example preset
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Inputs
Results
| Total load (g) | Calculated after input |
|---|---|
| Load rate (g/s) | Calculated after input |
| Daily load (kg/day) | Calculated after input |
| Target load (kg) | Calculated after input |
|---|---|
| Target load (g) | Calculated after input |
| Detail | Calculated after input |
| Detail | Calculated after input |
Formula details appear after calculation.
Sensitivity graph
Sensitivity graph appears after calculation.
Assumptions and calculation formula
Nutrient load and pollutant load formula
With concentration C (mg/L), flow rate Q (L/s), and period t (s), total load is M = C × Q × t.
Inputs are converted internally to mg/L, L/s, and seconds, then results are shown as kg, g, g/s, and kg/day. Nitrogen load, phosphorus load, suspended solids, and other constituents use the same mass-loading equation when units are consistent.
How reverse solve mode works
- Required concentration:
C = M / (Q × t) - Required flow rate:
Q = M / (C × t) - Required period:
t = M / (C × Q)
A reverse-solve result is the mathematical requirement for the target load. It does not prove that the value is feasible, compliant, or acceptable for a permit. Reverse solve is unavailable when a denominator becomes zero.
Frequently asked questions
How is nutrient load or pollutant load calculated?
The calculator converts concentration, flow, and time to common units, then applies M = C × Q × t. For total nitrogen (TN) or total phosphorus (TP), the result is a first-pass nitrogen or phosphorus load over the selected period.
What does the average concentration and average flow assumption mean?
The entered concentration and flow are treated as representative averages for the whole period. If storm events, daily cycles, treatment changes, or sampling timing matter, split the period and calculate each segment separately.
Why do mg/L, µg/L, and flow units matter so much?
µg/L is one thousandth of mg/L. Flow units such as m³/s, m³/day, L/s, and L/min also have different conversion factors, so a unit mismatch can change the load by orders of magnitude.
Can I use labels other than TN and TP?
Yes. NO3-N, NH4-N, PO4-P, SS, and custom constituents use the same calculation when concentration is expressed as mass per volume and the flow and time units are consistent. The label only changes the displayed context.
Can I use the result for regulatory or permit decisions?
No. This is a learning and screening calculator. Compliance work usually requires prescribed sampling methods, averaging periods, rounding rules, local definitions, and official standards that this page does not model.
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