Improvement of crossflow microfiltration performances for treatment of phosphorus-containing wastewater

In order to improve the removal efficiency of phosphate and mitigate membrane fouling, lime softening as a pretreatment for ceramic membrane microfiltration of phosphorus-containing wastewater was investigated. The effects of pretreatment on filtration flux, particle size, permeate quality, membrane fouling characteristic, and the recovery of membrane permeate flux after cleaning were studied. At the lime dosage of 680mg·L−1, the removal of phosphate increased from 11.0% without pretreatment to 99.7%, and the permeate flux was about 60% greater than that when lime was not used. The permeate obtained from softening and microfiltration met the National Discharge Standard and could be reused under very safe conditions. Pretreatment increased particle size, which mitigated membrane fouling by reducing the extent of pore plugging and forming a more porous cake on the membrane surface. The result was validated by ESEM micrographs. With the same cleaning method, the recuperation of permeate flux is approximately 18% greater with lime pretreatment than without pretreatment, which may be due to the differences in morphology of the deposited cake and the degree of irreversible fouling.