Formation of dynamic membrane in an anaerobic membrane bioreactor for municipal wastewater treatment

Abstract

An anaerobic dynamic membrane bioreactor with a high flux of 65 L/(m 2 h) was used to treat municipal wastewater. Particle size distribution, scanning electron microscopy, gel filtration chromatography (GFC), and three-dimensional excitation–emission matrix (EEM) were used to investigate the components of the cake layer formed on the membrane surface and the interception effect of the dynamic membrane. Test results showed that the dynamic membrane was formed by suspended solids (SS) in the settling zone and the soluble contents such as soluble microbial products (SMP) and extracellular polymeric substances (EPS). According to the index of SS/cake volume, the formation of dynamic membrane can be divided into three stages, i.e., the formation of separation layer, the stable growth stage, and the fouling stage. The accumulation rates of SS, SMP and EPS were of some differences at each stage. The secondary membrane was not entirely formed until the 7th day, and the dynamic membrane demonstrated a weak interception effect of dissolved organic matters after the 20th day. From EEM and GFC analyses of SMP in the cake layer, it was found that the fluorescence intensity ratio of Peak B/Peak A in the EEM fluorescence spectra had a similar changing tendency with large molecules of MW > 5000 kDa. They both increased with operation time before the 20th day, probably due to the soluble by-products secreted by the microorganism in the cake layer.