Hygienic water production in an innovative air lift bioreactor followed by high antifouling ultrafiltration membranes modified by layer-by-layer assembly

The possibility of continuous hygienic water production from wastewater in a combined system comprising an innovative air lift bioreactor and a membrane module was investigated. To improve the performance of a commercial poly acrylonitrile ultra-filtration membrane, layer by layer method was used. The effect of bilayer number (1, 3 and 5) and the type of polyanions on the membrane surface characteristics was investigated. Poly (4-styrenesulfonic acid-co-maleic acid) and poly (methacrylic acid) with different molecular weights were considered as polyanions and poly diallyl dimethyl ammonium as a polycation was used for surface modification. The polyelectrolyte multilayer fabrication was verified via attenuated total reflection, scanning electron microscope, atomic force microscopy, and contact angle characterization. According to the results, poly (4-styrenesulfonic acid-co-maleic acid) with higher molecular weight and charge density showed a better performance in terms of antifouling performance and flux recovery ratio compared to poly (methacrylic acid). An increase in bilayer numbers caused an increase in hydrophilicity and antifouling property. A membrane with 5 bilayers of Poly (4-styrenesulfonic acid-co-maleic acid) and poly diallyl dimethyl ammonium presented the highest hydrophilicity (the lowest contact angle) and flux recovery ratio (100%), and showed a gel-like layer on the surface. The production of hygienic water was confirmed by microbial test results.