A plant-wide modelling comparison between membrane bioreactors and conventional activated sludge

Abstract

A comprehensive plant-wide mathematical modelling comparison between conventional activated sludge (CAS) and Membrane bioreactor (MBR) systems is presented. The main aim of this study is to highlight the key features of CAS and MBR in order to provide a guide for an effective plant operation. A scenario analysis was performed to investigate the influence on direct and indirect greenhouse gas (GHG) emissions and operating costs of (i) the composition of inflow wastewater (scenario 1), (ii) operating conditions (scenario 2) and (iii) oxygen transfer efficiency (scenario 3). Scenarios show higher indirect GHG emissions for MBR than CAS, which result is related to the higher energy consumption in MBR. The simultaneous variation of the investigated factors (scenario 4) exacerbates direct and indirect GHG emissions for both CAS and MBR. Indeed, during scenario 4 a maximum direct GHG emissions of 0.94 kgCO2eq m-3 and 1.56 kgCO2eq m-3 for CAS and MBR, respectively, was obtained.