Sidestream Centrate treatment using High Purity Oxygen Membrane Bioreactors (HPO– MBR) – Pilot studies

The increasing regulatory demands to achieve greater nutrient removal have led to the development of several innovative biological nitrogen removal processes. This paper presents a novel approach based on the combination of membrane technology with the use of High Purity Oxygen (HPO) for the treatment of high strength centrate streams. The study is based on the results from a lab scale MBR pilot plant fed with centrate produced in a municipal WWTP with an anaerobic digestion process. The tests were run under a wide range of operational conditions of DO level, Temperature, HRT and pH. An intensive experimental campaign has been carried out including analytical measurements, online instrumentation, real-time estimations of OUR, a set of AUR batch tests, microbiological analysis and the application of modeling tools. The results indicate that the process can reliably provide up to 95% oxidation of ammonia with a notable effect of the DO level and Temperature on the Ammonia uptake rate. No inhibitions have been found that prevent the robust oxidation of ammonia in centrate streams and the microbiological analysis demonstrate that the use of HPO generates a robust and specialized nitrifier biomass community.