Research On A Hybrid Process With Polytetrafluoethlene(PTFE) Hollow Fiber Membrane For Purification Of Micro-polluted Water

The safety of drinking water in Pearl River region was subject to the impact ofseasonal pollution seriously. Conventional treatment was adopted in most drinkingwater treatment plants. Treated water in times of water pollution cannot fully meet thenew drinking water standards （GB5749-2006）. A hybrid process withpolytetrafluoroethylene （PTFE） hollow fiber membrane water was studied forpurification of micro-polluted. Raw water was from Dongjiang River. The tested PTFEmembrane has a pore size of0.12μm, out-diameter of2.3mm and inner diameter of1mm. It is of strong oxidation resistance and mechanical strength.Integration of coagulation and membrane was evaluated. Four oxidants includingozone, chlorine dioxide, potassium permanganate, sodium hypochlorite were comparedin small scale. The results showed that the optimal PACl coagulant dosage was10mg/L,the average removal efficiencies of COD_Mn, UV₂₅₄were33%,32%respectively,turbidity of effluent was under0.05NTU, particle number was below20CNT/ml;2³kDa molecular weight （MW） organic matter and small particles were identified asmajor membrane foulants, organic matter and small particles were accounted for60.3%and25.1%of total membrane fouling respectively. When the dosage of O₃、ClO2、KMnO4、NaClO were2.5,2.5,1.0,3.0mg/L, the removal efficiencies of DOC anddisinfection by-product formation potentials （DBPFPs） were44.7%,37.8%,35.1%,33.2%and60.4%,34.5%,28.8%,25.5%respectively. Membrane fouling was mostsignificantly reduced by ozone in comparison of other oxidants.An integration of coagulation/ozone/membrane with biological activated carbonwas studied in both small and pilot scale. Ozone and membrane were integratedfollowed by biological activated carbon. The membrane fluxes were60L/（m²·h） in smallscale and41.67L/（m²·h） in pilot scale of5m³/h. It is showed that ammonia removal loadwas3.19⁴.31mg/L, COD_Mnand UV₂₅₄removal efficiencies were70%⁹4%,73%⁸7%respectively, turbidity of effluent was under0.2NTU, particle number wasbelow50CNT/ml. THMs, HAAs, bromate, formaldehyde were below standard limits,total bacterial counts and coliform counts were not detected. It can be concluded thataddition of ozone （O₃/TOC=0.6⁰.8） is helpful in control of membrane fouling, the running time can be doubled,7⁹mg O₃/L was significant to eliminate membranefouling in situ gradually, thus decreasing chemical cleaning frequencies. The hybridprocess was suitable for purification of micro-polluted water source in the region ofPearl River downstream.