Membrane processes for water reuse from the effluent of industrial park wastewater treatment plant: a study on flux and fouling of membrane

Both the relationship between the flux and the fouling mechanism of ultrafiltration (UF) membrane and the effects of pretreatment before reverse osmosis (RO) process on the treatment of the effluent of industrial park wastewater treatment plant (IPWTP) were investigated to examine the application of membrane processes on the water reuse treatment. For the former, the flux data was first fitted to the Hermia model to give the implication of the fouling mechanism. Then, the fouling mechanism was further identified with the aid of the SEM morphology of membrane surfaces. For the latter, the changes of both water characteristics (turbidity, TOC, conductivity, particle size distribution, and organic solute molecular weight) and membrane properties (surface zeta potential and surface morphology) before and after the treatment of membrane processes were measured. It was found that the major blocking mechanisms of UF membrane process at initial and final stage were standard blocking of pore (causing from colloid materials) and cake blocking of pore (causing from suspended particles), respectively. On the other hand, it was concluded that the permeate from 1 μm/UF/RO process was suitable for the reuse of cooling water and low pressure boiler water.

The water quality of different permeates obtained from different RO processes are analyzed. The results are listed in Table 2. As shown Membrane filtration processes are successively applied to the reuse in many industrial wastewater. Until now, a main obstacle to membrane processes applications is the permeate flux decline caused by particle blocking, concentration polarization and fouling over a continuous longterms operation. This work utilizes the innovative analytical technologies to elucidate both the relationship between the flux and the fouling mechanism of UF membrane and the effects of pretreatment before RO process on the treatment of the effluent of IPWTP. It was found that the major blocking mechanisms of UF membrane process for initial and final stage are standard blocking of pore (causing from colloid materials) and cake blocking of pore (causing from suspended particles), respectively. On the pretreatment effect on RO permeate flux decline, UF membrane can remove more colloid materials and organic substance than 1 μm filter. Moreover, the initial flux of 1 μm/UF/RO unit will be greater than that of 1 μm/RO unit and the flux decline of 1 μm/UF/RO has no significant change after 120 min filtration, but 1 μm/RO unit still has a slight drop until 240 min. It was concluded that the permeate from 1 μm/UF/RO process was suitable for the reuse of cooling water and low pressure boiler water. Acknowledgment We thank the National Central University and Industrial Technology Research Institute for funding this work under Contract No. NCUITRI 930301.