Study On Application Of Microfiltration Flat Membrane And Reverse Osmosis Membrane In Wastewater Treatment And Reuse

Membrane technology has a unique advantage in the field of environmental protection. The microfiltration flat membrane and reverse osmosis membrane have been wildly used in the wastewater treatment and reuse. There occur such emergency problems as how to reduce the cost of flat membrane and how to use the membrane technology together with other techniques to improve the overflow quality. In the light of the problems mentioned above, the application study of plat microfiltration membrane and reverse osmosis membrane has been carried out.The membrane filtration property of non-woven materials and polyvinylidene fluoride (PVDF) flat membranes was investigated by the comparative test under the same experimental conditions. After filtration, the removal percentages of COD and NH₄^--N were both over 90%, SS=0 mg/L and turbidity of filtrate<0.4 NTU. The effluent quality both reached the deadline of the town sewage treatment plant pollutant emission standards for the third. The changes of TMP revealed that the non-woven materials were better served as c in membrane bioreactor system. The filtration mechanism of non-woven module was attributed to the dynamic membrane filtration by the cake layer formed on the non-woven surface, which reinforced the interception of the membrane. The analysis of membrane resistance showed that the cake layer resistance predominated and amounted to 83.6% of the total resistance. 94 % of the original flux of membrane was restored after chemical washing. SEM images showed that contaminants were mainly concentrated on the surface of non-woven material, which contributed to the reversibility of fouling considering the result of the membrane resistance analysis. The chemical analysis and FT-IR analysis proved that the proteins were the main contaminants in EPS and its proportion was much higher than that of polysaccharide molecules in both cake layer and membrane.In order to improve the quality of effluent and extend the life of RO membrane, the PVDF membrane bioreactor and RO process were used together. The results showed that the removal percentage of COD and NH⁴⁺-N reached to 96.8% and 89.0% under the circumstance of the 500⁸00mg/L of COD_(infulent) and the 20-40 mg/L of NH₄⁺-N_(infulent). The effluent of SDI, turbidity, free chloride and SS all met the requirement of RO influent condition. The removal percentage of conductivity, hardness, alkalinity, calciumion and Cl^-1 were 95.8%, 99.9%, 91.1%, 99.9% and 96.5%, respectively. The effluent quality reached the quality standards of cooling water reuse water in China. Membrane flux recovered to the initial condition after cleaning with 0.2% HCl.The modified non-woven microfiltration flat membrane was used to treat the silicone wastewater from Mechanical Processing in semiconductor industry. The effect factor of filtration was investigated. The relationship between dynamic cake layer formation and filter resistance was revealed. The operation conditions for the long stable operation were optimized. After filtration, the conductivity of effluent was less than 20 us/cm, turbidity<0.1 NTU, SS=0 mg/L and soluble SiO₂<52 mg/L. The effluent could be reused and the silicone enriched.