Comparison of ultrafiltration and self-forming dynamic membranes in membrane bioreactors for municipal wastewater treatment

Membrane bioreactor (MBR) was used to be a solution of the drawbacks of the conventional activated sludge which are related with area limitation and high quality of effluent requirements. However, the cost of membrane modules and fouling control are still problems which facing the operation of MBRs. Dynamic membrane (DM) technology can be a promising solution to mitigate the previous drawbacks. DM is a secondary layer, organic or/and inorganic compounds, formed on a low-cost support porous material such as mesh. This layer is responsible for solids retention and improvement of permeate quality of the support material. The main aim of this thesis was to investigate the applicability of using tubular hollow fiber self-forming dynamic membrane as a low-cost alternative for ultrafiltration (UF) membrane for municipal wastewater treatment. A hollow fiber polyester fabric was used as a support material to form DM (cake) layer. Besides, a hollow fiber polyvinylidene fluoride UF membrane was used in parallel under the same operating conditions. Treatment and filtration performances of the DM and UF membrane were comparatively evaluated in order to determine the advantages and disadvantages of each system. The system was operated for 85 days at ambient temperature. Both membranes were operated at flux around 5 L/m2 /h. By the end of the experiment, morphological analysis had been done for UF membrane and DM surfaces, including environmental scanning electron microscopy, energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), and Confocal Lase Scanning Microscopy analyses. High COD removal efficiency, high SS rejection and low turbidity were achieved in DM permeate which were comparable with UF membrane performance. Significantly higher TMP values were achieved during the operation of DM comparing with UF membrane, which was related with the formation of cake layer in DM technology. The DM layer played an important role in rejection of small particle, showing higher performance than the UF membrane. According to the FTIR and EDX analyses results, the DM layer was formed by both organic and inorganic materials.