Characterization of wastewater and biomass activity in a membrane bioreactor using respirometric techniques

Abstract

Over the last two decades, Membrane Bioreactors (MBRs) emerged even more for wastewater treatment, ensuring high removal efficiencies as well as very small footprint required. Indeed, in this kind of process, a modification in biomass activity and viability can exist compared to that of a conventional activated sludge (CAS) process. In this context, respirometric analysis represents a reliable tool in order to evaluate the actual biomass kinetic parameters, to insert in mathematical models in the design phase, as well as to monitor the biomass viability, especially when these processes are operated with high sludge retention time (SRT) values. The paper presents some results of respirometric techniques applied for the characterisation of wastewater and biomass activity in a pilot UCT-MBR plant for nutrient removal, operating with high SRT. In particular, the respirometric tests were specifically aimed at investigating heterotrophic and autotrophic bacterial activity. The pilot plant was built at the Acqua dei Corsari (Palermo) wastewater treatment plant and consisted of three reactors in the following order: anaerobic (mean volume 71.6 L), anoxic (mean volume 165 L) and aerobic (mean volume 327 L) tanks, followed by an aerobic compartment (mean volume 52 L) containing two submerged hollow fibre membrane modules (Zenon Zeeweed, ZW 10) with typical recycling lines