BOD Removal Efficiency
Also known as percent BOD removal
Worked example: 220 mg/L in, 18 mg/L out → 91.8% removal — press Try an example to run it live, then adjust anything.
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UniversityProcess & Water Chemistry
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BOD Removal Efficiency explained
Percent removal is the number on the discharge permit and on the front page of every monthly operating report. A plant taking 220 mg/L of BOD down to 18 mg/L is removing 202/220 = 91.8%, and US secondary treatment standards demand at least 85% removal of both BOD and TSS along with a 30 mg/L monthly average. Primary settling on its own is worth 25–35% of BOD and 50–65% of TSS; conventional activated sludge adds the rest.
The formula has a blind spot that regulators had to legislate around: percent removal is a ratio, so a community with dilute wastewater — heavy infiltration, a lot of groundwater in leaky sewers — can produce a beautifully low effluent and still fail the 85% test, while a strong-waste town can pass the percentage while discharging more pounds than its neighbour. That is why permits carry both a concentration limit and a percent-removal limit, and why the pounds-per-day loading is the honest measure of what reaches the river. Use concentrations from flow-proportional composite samples; a grab sample at 10 a.m. on a Tuesday flatters or damns a plant depending only on when the town takes its showers.
BOD Removal Efficiency formula
- = Removal efficiency (%)
- = Influent concentration (%)
- = Effluent concentration (%)
Missing one of these? Work it out first, then come back
- Removal efficiency — Boiler or Furnace Output from Input, Three-Phase Motor Full-Load Current
- Influent concentration — Volumetric Organic Loading Rate, Food-to-Microorganism (F/M) Ratio
- Effluent concentration — BOD Mass Loading, Flow-Weighted Blending Concentration