The Effect Of Nano SiO₂ On Nom Removing In Coagulationultrafiltration Process

The advanced water treatment has become an important research direction because of the water pollution and requirements of drinking water. The pollution of the water environment become worse because of the development of nanotechnology. This study researched the effect of nano silicon dioxide and dissolved organic matter in same coagulation process with different condition of water sample, which were prepared nano silicon dioxide water sample with Xiaoqing River and Yellow River, and it even showed that the effect of nano silicon dioxide to different organic matter in coagulation – ultrafiltration process and membrane fouling.The main research contents and results are as flollows:1. The dosage of coagulatant（PAC） and the p H of the water sample was tested in coagulation process, and the optimum dosage were 12 mg/L and 8 mg/L in Xiaoqing River and Yellow River, respectively. And the best p H of the water was 6 in both water samples. The removal efficiency of DOC in optimum dosage of Xiaoqing River and Yellow River were 31% and 25.5% when B=2.0, and the p H=6 was regulated, the efficiency was up to 38% and 28%, respectively.2. By comparing the effect of coagulation process with different silica adding in the raw water, the result showed that both of 50 nm and 2 μm Si O₂ increased the residue turbidity and DOC, and the removal efficiency was decreased 10²0%, while the removal efficiency of UV254 had changed little in Xiaoqing River. However,the Yellow River showed different phenomena with Xiaoqing River in coagulated process, silicon dioxide increased the removal efficiency of DOC andUV254 about 10%, and decreased the removalefficiency of turbidity.3. The floc properties were monitored in the coagulation process, the experiment showed that when the nano Si O₂ adding into the water sample, the d50 was smller, and Df was smaller in Xiaoqing River,and larger in Yellow River,and the structure of the flocs were compaction. However the different water sample had different floc properties, which in the codition of optimal dosage and p H, the Xiaoqing River had larger d50 with Yellow River, and the Df was larger in Yellow River, the floc had compact structure.4. Nano silicon dioxide had different removal efficiency of different organic matter properties. The nano silicon dioxide increased the removal efficiency of carboxyl functional groups,and even promoted different molecular weight of organic matter,especially the low molecular weight NOM. EEM peak of the solubility of microbial metabolites showed up in Coagulation water samples.II and IV area occupies a proportion of the total fluorescence intensity decreases, and the III and V was contrary with them with Nano silicon dioxide adding in, and the intensity of the total accumulated increased.5. The main membrane resistance was extra membrane resistance, and the main membrane fouling was strong cake layer, the membrane resistance was reduced 98% with the coagulation pretreatment, and nano Si O₂ increace the strong cake layer and irreversible intramembrane resistance in Xiaoqing River; the Yellow River was just like Xiaoqing River, however, the the membrane resistance was loosely cake layer with the pretreatment, and the extra membrane resistance was increased by adding the Si O₂, and the nanoparticles changed the loosely cake layer.