Nitrification of municipal wastewater in moving‐bed biofilm reactors

A moving‐bed biofilm reactor has been developed, where the biofilm grows on small, free‐floating plastic elements with a large surface area and a density slightly less than 1.0 g/cm 3 . Nitrification of preprecipitated wastewater in a once‐through system and raw wastewater in a recycled system with predenitrification has been studied in a pilot plant with an active, specific biofilm surface area of approximately 310 m 2 /m 3 . Maximum nitrification rates under comparable operating conditions were 20% to 25% higher with preprecipitated wastewater in the once‐through system than with raw wastewater in the recycled system. A temperature coefficient of θ = 1.09 was found. However, under oxygen‐limited conditions, the apparent temperature effect was insignificant in the temperature range from 7 to 18°C because of increased dissolved oxygen levels at low temperatures. At 10°C volumetric nitrification rates from 300 to 400 g NH 4 ‐N/m 3 ·d can be expected.