Flux decline study for textile wastewater treatment by membrane processes

Membrane methods, including MF, UF and NF, belong to high-efficiency processes which can be competitive with traditional methods of water treatment. However, their efficiency can be affected by some parameters such as rejection and permeate flux. In this work, three membrane processes (MF, UF and NF) were used for the treatment of textile effluent sample and factors influencing the flux decline of the used membranes were investigated. MF and UF processes were studied in order to be investigated as pretreatment for the NF process in the case of textile effluent treatment. Linearized forms of cake formation equations were used according to Wiesner and Aptel equations and the various filtration resistances were determined using the resistance-in-series model. Experiments demonstrated that more than 90% of colour, turbidity and TDS were removed from the treated water accompanied with a reduction of COD. Experimental results concluded that concentration polarization was the principal cause of flux decline for UF membrane. On the other hand, fouling was observed to make an important contribution to flux decline for NF membrane. We concluded also that rapid cake formation occurred during initial filtration and caused an initial sharp decrease in permeate flux for MF and UF processes. In the case of NF process, the cake formation took place progressively and increased in the second state of filtration.