Impact of methanogenic pre-treatment on the performance of an aerobic MBR system

Abstract

The combination of anaerobic treatment with an aerobic MBR as a polishing step is an alternative to treat some industrial wastewater and/or urban wastewaters generated in warm climate countries. In this work a pilot-scale UASB reactor and an aerobic MBR as a polishing step was operated. The impact of the methanogenic stage on membrane fouling was studied. Operating fluxes of 11–18 L m−2 h−1 and permeabilities of 100–250 L m−2 h−1 bar−1 were reported. It was demonstrated that the recirculation of aerobic biomass to the anaerobic stage provoked a release of biopolymers due to the hydrolysis of aerobic biomass in these conditions. Depending on biomass concentration in membrane chamber, the presence of biopolymers worsened membrane performance. Fouling rate was three times higher when biomass concentration decreased from 8 to 2 g L−1, with similar concentrations of biopolymers present. Moreover, the presence of plastic support in the aerobic stage was shown to improve membrane performance, decreasing the concentrations of the studied fouling indicators.Carbohydrate fraction of soluble microbial products, biopolymer clusters (BPC) and transparent exopolymer particles (TEP) concentrations were studied as possible fouling indicators for this system. A strong correlation between both colloidal fraction of BPC (cBPC) and TEP with membrane fouling rate was observed.