The organic nitrogen split, total nitrogen, and — the part that actually matters — the oxygen and alkalinity your nitrifiers will demand once the organic fraction hydrolyses inside your plant.
Organic nitrogen hydrolyses to ammonia inside your process. It arrives as protein and leaves the primary clarifier as ammonia demand you didn't count at the headworks.
So the oxygen your blowers have to supply, and the alkalinity your process will consume, are driven by TKN — not by influent ammonia. A plant sizing aeration or chemical alkalinity addition off ammonia alone runs short on high-organic-nitrogen days: heavy septage receipt, an industrial protein load, high solids.
| Per mg/L of nitrogen | Value |
|---|---|
| Oxygen consumed, nitrification | 4.57 mg/L |
| Alkalinity destroyed, nitrification | 7.14 mg/L as CaCO₃ |
| Alkalinity recovered, denitrification | 3.57 mg/L as CaCO₃ |
| Minimum effluent alkalinity to hold | 50 mg/L as CaCO₃ |
| Pattern | Suggests |
|---|---|
| High ammonia fraction | Fresh domestic wastewater, short collection system, or significant sidestream return. Nitrogen is already in the form your nitrifiers use. |
| High organic fraction | Longer collection time not yet hydrolysed, industrial protein load, high solids, or septage receipt. That nitrogen becomes ammonia demand on a delay. |
| Sudden shift toward organic | Investigate — a slug of protein-rich waste or septage arrived. |
What the test captures and what EPA says it misses, the four methods and their ranges, the preservation trap, the sidestream problem, and why soluble non-biodegradable organic nitrogen sets a floor on total nitrogen removal.
Read the GuideFree · No signup