Combining Ozonation With Ceramic Ultrafiltration For Treating Drinking Water From Micro-polluted Water Source

The treatment of drinking water from micro-polluted water source is one of the great challenges in the field of drinking water safety in China. The traditional treatment process train cannot efficiently remove micro-pollutants. While the frequently-used advanced treatment process train has some problems as long procedures, high investment and operation cost. This thesis investigated an innovative integrated process including coagulation, ozonation, ceramic ultrafiltration(UF) and biological activated carbon(BAC) filtration, combining the regular and advanced treatment process together, in which ceramic ultrafiltration was conducted with a new type of oxidation-durable flat sheet ceramic membrane with mean pore size of 60 nm. In result, the number of processing units was greatly reduced. This thesis conducted experimental tests at three levels including bench scale test, small field test and pilot scale test with a capacity of 120 m3/ d.The synergistic interaction between ozone and ceramic membrane was demonstrated in bench scale experiment, which provides theoretical and technical evidence for the integrated processs. The reaction rate constant of ozone decomposition in the ceramic membrane pores which was doped with MnO2/Al2O3 was 428 times of that outside the pores. The ozone decomposition inside the membrane pores was significantly affected by H2O2, pH, SO42-, NO3- and Ca2+. Ozonation speeded up the decomposition of nitrobenzene and atrazine inside the membrane pores. For the explanation of the reaction phenomena, the concept of “nanometer reactor” inside the membrane pore was proposed in this thesis, which is an innovative concept in the drinking water treatment field.The technical efficiency of the integrated process “half coagulation/ ozonation/ ceramic UF- BAC” was proved by the small field test. The stability, reliability, and economic performance of the continuous operation of the integrated process were demonstrated in the pilot scale experiment. The turbidity of the membrane permeate was less than 0.1 NTU, while the particles larger than 2 μm was less than 10 counts per milliliter. Microorganisms as total plate count, total coliform group, algae, et al,were not found in the membrane permeate. The removal ratios of UV254, CODMn and DOC by the integrated process were 85 %, 87 % and 73% respectively. The removal efficiencies of the formation potential of trihalomethanes, haloacetic acids and chloral were 77%, 76% and 83% respectively during the treatment by the integrated process, while the removal ratios of geosmin, 2-methylisoborneol, 8 endocrine disrupting compounds(EDCs) and 14 pharmaceutical and personal care products(PPCPs) were 96%, 88%, 98% and 98% respectively. The concentration of ammonia in the effluent of the process train was less than 0.1 mg/L while its concentration was 3.5 mg/L in the raw water. The operation cost of the pilot scale experiment was 0.423 RMB per ton drinking water.Ozone performed better than KMnO4, ClO2 and NaClO on the control of membrane fouling. In the pilot scale test with an ozone dosage of 2~5 mg/L, the membrane fouling can be constantly controlled. Kaolin particle, humic acid, sodium alginate and bovine serum albumin were used as typical membrane-fouling pollutants. The results showed that complex synergetic effects on membrane fouling were observed when multiple pollutants present in the water. The structural properties of the organic matter can be directly changed with enough ozone dosage. The adsorption of organic matter on the membrane surface could be reduced or the adsorbed organic matter could be removed from the membrane surface. In this way, the membrane fouling can be controlled in situ, which is significant for the stable operation of the integrated process.The integrated process was developed based on the synergistic effects between ozone and the ceramic membrane. The integrated process can replace the traditional and the advanced treatment process, it can be used to upgrade the traditional water treatment plant. It is believed that the integrated process in this paper has important theoretical and engineering significance.