Membrane fouling behavior during filtration of sludge supernatant

Colloidal particles and soluble matter in sludge supernatant are major membrane foulants during the operation of membrane bioreactors in wastewater treatment. The article discusses membrane fouling mechanisms during membrane filtration of sludge supernatant liquor. The influence of supernatant turbidity transmembrane pressure, and crossflow velocity on membrane fouling was systematically investigated. The membrane fouling was characterized by Fourier transform infrared spectroscopy technique. The results showed that the high supernatant turbidity could result in severe membrane fouling because of the accumulation of colloidal particles and soluble matter on the membrane surfaces. High transmembrane pressure could lead to a high flux decline rate because of the formation of a dense cake layer. The crossflow velocity just had a slight influence on membrane fouling, as it was not larger than 0.12 m/s, However the membrane fouling decreased significantly as crossflow velocity increased to 0.24 m/s. The membrane fouling mechanisms of these operational conditions, including supernatant turbidity, transmembrane pressure, and crossflow velocity, were different from each other. Membrane fouling resistance can be predicted using a simple model based on supernatant turbidity, transmembrane pressure, and crossflow velocity. The major components of the foulants were proteins and polysaccharide materials. (c) 2007 American Institute of Chemical Engineers.