Effect Of Coagulant On Performance Of Ultrafiltration Membrane In Dyeing Wastewater Treatment And Reutilization

This paper studied the effect of ferrous sulfate coagulant on the ultrafiltration membrane performance in dyeing wastewater treatment and reutilization. Three kinds of membranes including polysulfone (PS), polyether sulfone (PES) and polyacrylonitrile (PAN) membrane with MWCO 30000 Da were used. The optimal coagulation condition and the influence of coagulant on different membrane were explored. The mechanism of membrane fouling and the difference between supernatant ultrafiltration and on-line ultrafiltration operation were mainly focused on.It was found that the residual coagulant should be thought as one of the most important parameters during the coagulation. The flux and resistance of PS and PES membrane decreased when the concentration of ferrous sulfate increased. However, the ferrous sulfate did not affect the flux and resistance of PAN until the concentration up to 100 mg·L-1. PAN membrane exhibited excellent performance of anti-fouling in the tests. Both supernatant ultrafiltration and in-line ultrafiltration could mitigate membrane fouling, while the mechanism was different. The results of particle size distribution and scanning electronic microscope (SEM) tests indicated that the particle size of the pollutants got larger after coagulation which was supposed to the primary reason of alleviating membrane fouling. And the reduction of the residual coagulation was helpful to mitigate the membrane fouling. The suspended residual coagulant can be removed by ultrafiltration, while the ionic coagulant can be removed by nanofiltration, and the residual coagulant did not affect the permeability of nano-membrane. In addition, the dyeing wastewater can be reused after the treatment of the coagulation-ultrafiltration-nanofiltration.