A Study On The Application Of UF For Wastewater Reuse

Polyacrylonitrile(PAN) and polyethersulfon(PES) UF membrane with 3×10⁴ and 7×10⁴ Da were used to treat the secondary effluent from Xi'an Bei Shi Qiao Sewage Purification center. The study investigated the characteristics of UF for permeate flux,membrane fouling the removal of turbidity,organic substances and bacteria. The performance of UF membrane processes and pretreatment processes, such as coagulation and using powdered activated carbon were discussed.The results of UF cell test show that the MWC of the membrane plays an important role in the transmembrane flux, the higher the MWC, the smaller the permeate flux. Comparing the PES and PAN membrane, the PAN membrane has the higher permeate flux than the PES membrane with the same MWC. The PAN membrane with 3 ×10⁴ Da can run a rather long time for water reuse.The pilot studies show that UF has high efficiency in the removal of turbidity and physical disinfection. It can achieve 90% removal of turbidity and 99.9% removal efficiency of bacteria and E.coli. Direct ultrafiltration without pretreatment achieved the lowest removal of UV₂₅₄, TOC and colour with the removal efficiency of 34.9%, 33.16% and 39.9% respectively, while ultrafiltration with pre-coagulation the highest removal of that with the removal efficiency of 52.7%, 66.3% and 81.5% respectively.Membrane fouling analysis show that the component of foulant is hardly affected by the material and the MWC of membrane. By the analysis of membrane fouling mathematic model, a conclusion can be drown that permeate flux decline is resulted mainly by membrane pore blocking and by cake formation.