Fabrication, characterization and treatment of polymeric membranes with submerged membrane bioreactor system: fruit juice industry wastewater

The aim of this study is to examine the effects of modification of polymeric polyacrylonitrile and polyetherimide membranes with a polymeric additive, namely polyvinylpyrrolidone, on membrane performance in a submerged membrane bioreactor under different operating conditions. For this purpose, the membrane filtrations were performed with raw and modified membranes after the activated sludge was acclimated in the submerged membrane bioreactor to two different sludge retention times and two different organic loading rates. While the performance of all membranes increases with an increase in sludge retention times, the increase in organic loading rates decreases soluble microbial products. The modification with polyvinylpyrrolidone provides higher total permeate volumes with the higher rejection of soluble microbial product fractions, especially in polyacrylonitrile membranes. The rejections of carbohydrate fraction of soluble microbial products increase by the modification of both membranes with polyvinylpyrrolidone. Membrane fouling is determined to be inversely proportional to the membrane pore size. Scanning electron microscope analyses confirm that membrane fouling increased at low sludge retention time and high organic loading rate. The carbohydrates and proteins are approved as the main foulants on the membrane surface with Fourier transform infrared spectroscopy. As a result, modification of polyacrylonitrile polymer with polyvinylpyrrolidone is determined as an appropriate approach in order to increase treatment efficiency and improve membrane lifetime in submerged membrane bioreactor operated at high sludge retention time.