The biological wastewater treatment step is the largest energy consumer of all process steps at a municipal wastewater treatment plant. The treatment is a complex interaction, which can be very sensitive to change of pH, oxygen concentration in the water, and temperature. Process experts at a European wastewater treatment plant wanted to improve their maintenance schedule for the aeration elements of biological wastewater treatment. Because the aeration elements suffer from fouling, they need to be cleaned regularly. Oxygen concentration decreases when aeration elements are fouled, and the treatment no longer works efficiently. The goal was to transition to maintenance planning from a time-based schedule. However, the high variance of variables made it difficult to have a clear indicator.
In the biological reactor, the pressurized aeration system delivers oxygen for the bacteria. A low concentration of Oxygen is one factor which can lead to a high concentration of nitrite.