Study On The Processing Efficiency Of PCBs From Micro-polluted Water By Enhanced Coagulation

Based on the research of inorganic, organic coagulant and composite coagulant, as well as the use status of “ Enhanced Coagulation" process in the water treatment. In this paper,by reference a large number of domestic and foreign relevant information and studies, use the PolyAluminumChloride(PAC), PolyFerricSulfate(PFS), PolyDimethylDiallylPropy Ammoni-umlChloride(PDMDAAC), PolyAluminum SilicateSulfate(PASS), PAC-PDMDAAC and PFS-PDMDAAC as coagulants, selectthe Polychlorinated biphenyls(PCBs) astreatmentobject,researchthe elimination of turbidity and Polychlorinated Biphenyls (PCBs) in simulated water samples by enhanced coagulationtechnique. On the basis of previous studies, Solid Phase Extraction(SPE) is used topretreat the PCBsin water samples , the GC-3800 gas chromatgraph isusedtodetectthePCBs and to optimizathe detect method, including injection port temperature,column temperature, ECD detector temperature.The effects of dosage of coagulant, initial turbidity, pH, the time for slow stirring and compound coagulant aid on the elimination efficiency of turbidity and PCBs were tested and characterized by fractal dimension of flos and Zeta potentials to verify the result. The specific research contents and results are as follows:(1)PAC, PFS and PDMDAAC were used to dispose the target water samples(PCBs-kaolin simulated water samples) by enhanced coagulation process,the coagulation efficiency of the system was improved by using powdered activated carbon, unmodified attapulgite and hydrochloric acid modified attapulgite. The effects of common factors on the elimination efficiency were tested and characterized by fractal dimension of flos and Zeta potentials to verify the result. The results show that PAC and PFS apply to low turbidity water(62-92NTU) and the PFS has better effect on the removal rate of PCBs and turbidity than the PAC. Compared with the inorganic polymer coagulant, the PDMDAAC composite coagulant has better effect on the initial turbidity of 162-282NTU water. The removal rate of PCBs is better when the separately dosage of PAC and PFS is 14mg/L. The PDMDAAC has narrow optimal coagulant range suitable for use, when the dosage is higher or lower than the optimal dosage,the removal rate of PCBs and turbidity in water samples was significantly decreased.Meanwhile, the time for slow stirring is an important factor affecting the efficiency of enhanced coagulation, by adjusting the time for slow stirring can improve the treatment rate of PCBs in water samples can be increased. With the prolong of the time for slow stirring, the removal rate of PCBs by PAC, PFS and PDMDAAC coagulants decreased first and then decreased. The hydrolysis of PAC, PFS and PDMDAAC is different, which leads to the different range of the best pH value of them, the PAC and PFS are more suitable for acidic water. PDMDAAC has narrow optimum pH range, are more suitable for alkalescent water with pH is 7.5. The addition of coagulant aids can effectively improve the removal efficiency of PCBs and turbidity by PAC, PFS and PDMDAAC. Compared with powdered activated carbon and unmodified attapulgite, hydrochloric acid modified attapulgite is more effective in improving the coagulation effect,and it is convenient to use, the cost is low, have more broad application prospect.(2)The elimination of turbidity and PCBs in micro-polluted waterby enhanced coagulation was studied.The PASS was prepared by sodium silicate and aluminum sulfate.The polychlorinated biphenyls (PCBs) and turbidity were used in the micro-polluted water Removal effect was studied. The effects of dosage of coagulant, initial turbidity, pH, the time for slow stirring on the elimination efficiency of turbidity and PCBs were tested and characterized by fractal dimension of flos and Zeta potentials to verify the result. The results show that the removal rate of PCBs reach 77.39%-90.19% and the turbidity removal rate was the best when the dosage was 1.1mL/L and the time for slow stirring was 15 min. With the increased of initial turbidity, the removal rate of PCBs in the water is also increased which shows that the PASS apply to high turbidity water. Compared with the single coagulant, the PASS composite coagulant has wide pH range suitable for use, the removal rate of PCBs and turbidity reach the best in the acidulous water (the pH is 6.5). Based on the fractal dimension offlos and Zeta potential, the experimental results were accurate.(3)The enhanced coagulation of PCBs-kaolin simulated water samples by PAC-PDMDAAC and PFS-PDMDAAC of 0.8mg/mL solid content, which were separately prepared by PAC-PDMDAAC and PFS-PDMDAA. The results show that the coagulation efficiency of PAC/PFS-PDMDAAC was the best when the mass ratio of inorganic component and organic component was 5:1. PAC/PFS-PDMDAAC can effectively solve many problems,such as PAC, PFS have weak adsorption of electricity and adsorption bridging capacity, the unstable hydrolysis reaction, the large dosage, and the PDMDAAC has the narrow range of best dosage and pH when removal the PCBs in the micro-polluted water. Compared with the PASS, the PAC/PFS-PDMDAAC has low dosage and the removal rate of PCBs in the water sample is high and are more suitable in a highturbidity water sample (500-600NTU).