Work out oxygen requirement for aeration instantly with clear inputs, formula shown and shareable results.
Oxygen demand is about 1.1 kg per kg of BOD removed plus 4.57 kg per kg of ammonia nitrogen oxidised — nitrification often accounts for a third or more of total demand. Field requirement divides by the alpha factor for wastewater's poorer transfer, and air volume follows from oxygen content and transfer efficiency.
Oxygen demand
O2 = 1.1 x BOD removed + 4.57 x ammonia N oxidised
Air requirement
Air (kg) = field O2 / (transfer efficiency x 0.232 oxygen mass fraction)
Surfactants and dissolved organics reduce oxygen transfer compared with clean water, typically to 0.4-0.7 of the standard rate. Blower sizing on clean-water performance alone under-sizes the system badly.
Oxidising ammonia to nitrate needs two moles of oxygen per mole of nitrogen, which is 4.57 kg per kg of nitrogen. Aeration for nitrification is often the largest single energy consumer at a works.