Using chlorine dioxide to remove the fouling of ultrafiltration membrane and its affection on DBPs control

• Main Authors: Chia-yu Tsai, 蔡佳妤
• Other Authors: Shu -Hai You
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/82500649441610736674

碩士 === 國立聯合大學 === 環境與安全衛生工程學系碩士班 === 97 === Ultrafiltration (UF) can remove the natural organic matter (NOM) effectively, but it may be rapidly blocked by a variety of fouling from the surface water. Besides, chlorine dioxide (ClO2), an oxidative agent, has been the substitutable disinfectant since it forms less disinfection by-products (DBPs) with NOM. Therefore, the combination of ClO2 and UF may upgrade or improve the conventional purification process. The feed water containing humic acid with 4.07 mg/L as TOC was dosed directly with various amounts of ClO2 before the 5K or 30K ultrafiltration membrane (PES material) in the study. The water pressure was fixed at 3 kg/cm2 and the water temperature was maintained at 25oC. It was observed that the permeate flux was about 60% after 150 minutes with feed water containing 0 mg/L ClO2. It was also observed that the permeate fluxes with feed water containing above 5 mg/L ClO2 were less than with feed water containing 0 mg/L ClO2. Comparing the cake thickness among the membranes by SEM observation, it is probable that the ClO2 had changed the larger organic fouling on the membrane to smaller organic molecules that have been adsorbed onto the inner pore fibers. On the contrary, It was discovered that 2 mg/L ClO2 had good effect on permeate flux (about 80%); probably it was insufficient for destroying the organic matter to smaller organic molecules. Furthermore, the organic fouling on the UF membrane looked loosen by the SEM observation, it may be flushed away more easily by the cross flow. Although UF could remove the humic acid very effectively as TOC had been removed completely and had good effect on permeate flux with 2 mg/L ClO2 dosage, but there was not any residual ClO2 or Cl2 in the permeate. It was also observed that the concentration of ClO2- and the total trihalomethanes (TTHMs) were below the Maximum Contaminant Level (MCL).