Study of the setup and the optimization of lab-scale Membrane Aerated Bioreactor (MABR)

The growing environmental awareness, increasingly stringent environmental laws related to the discharge into surface waters, the need to reduce GHGs and energy consumption in wastewater treatment plants have led to the research for new and modern technology in this field. This master’s thesis focuses on the configuration, study and optimisation of a Membrane Aerated Bioreactor (MABR) - an innovative system that allows wastewater treatment with higher energy efficiency and much elevated nitrogen and COD removal rate, compared to the Conventional Activated Sludge reactor (CAS). The main principle of this reactor lies on the counter current supply of oxygen through a membrane, allowing a constant aeration for the biofilm which ensure the establishment of an aerobic zone for the nitrification and an anoxic zone for the denitrification, enabling the Simultaneous Nitrification and Denitrification (SND). The experimental analyses were carried out in the biological laboratory at DIATI department in Polytechnic of Turin and the experimentation is divided into three principal phases. The first phase consisted in the inoculation of the reactor for the effective development of a biofilm with a secondary activated sludge rich in microbial communities, fundamental for the growth of the attached biomass. The second phase, or intermediate phase, was inevitable due to issues with the reactor biomass and the holyday closure. Phase three determined the optimisation of MABR operational conditions, and the Oxygen Transfer Rate (OTR) and the Oxygen Transfer Efficiency (OTE) were monitored to determine the effectiveness of the aeration system. This phase was crucial for the improving of nitrification removal rate which increased to a maximum value of 8 ppm/d while the removal efficiency of organic carbon is higher than the 50%. The results demonstrate how the MABR reactor represents a more sustainable alternative to the conventional treatments thanks to its promising removal performances which can comply with the legislation. This thesis provides the basis for further and more precise experimentations necessary to determine and evaluate the full potential of the MABR.