Study On Emergency Treatment Process For Chlorothalonil Pollution In Raw Water By PAC Adsorption And Enhanced Coagulation

China is a developing agricultural country,as well as a big country in the production and use of pesticide which has play an important role in Chinese economy. However, several water environment pollutions have emerged within the production and use of pesticide. At the same time, due to the potential problems such as sewage illegally disposal, chemicals leakage accident, contrived poisoning, traffic accident and so on, the risk of sudden pesticide pollution happened in the source water is increasing continuously.Through the analysis and comparison of the measures to the sudden pesticide pollution in water of the existing water-plant, PAC was an excellent adsorbent to adsorb organic pollutants with non-ionic, hydrophobic and benzene ring structures. And enhanced coagulation could improve the conventional treatment process on the removal of natural organic matter by increasing the dosage of coagulant or adjusting pH. Combining with chlorothalonil, which is one kind of widely-used organochlorine pesticides, the author of this thesis would make the further study on these two processes, to find the emergency treatment process based on the water purification process of the urban water-plant.According to the surface physical and chemical analysis of powder activated carbon (PAC), the adsorption ability of PAC A, which has more developed micropores, greater polarity, higher surface area and bigger pore volume, is better than PAC B. Through the result of PAC-Water separation experiment, it has showed that the material of the micro-filtration membrane could adsorb the chlorothalonil and make the detection results of chlorothalonil in water to become smaller. At the same time, filtration of quartzite medium column and high-speed centrifugation could not separate the PAC and water effectively. Therefore, for detecting concentration of chlorothalonil of water samples in this thesis, carbon-water separation was achieved by coagulation and sedimentation.About the remove efficiency of chlorothalonil by enhanced coagulation, we did some research on three main effect factors like coagulant types, dosages and pH. The result showed that poly aluminium chloride and Al₂(SO₄)₃·18H₂O had excellent removal effect but FeCl₃·6H₂O did not. After the enhanced coagulation, the turbidity of the water has some relevance with the removal efficiency of chlorothalonil. At the same time, pH has greater impact on removal of chlorothalonil. When the dosage coagulant is 10mg/L, the removal percentage of poly aluminium chloride (pH≥7) and Al₂(SO₄)₃·18H₂O (pH≥6) is over 70% and 65% respectively. The result also show that enhanced coagulation had excellent removal efficiency on different concentrations of chlorothalonil in the raw water, but water after the treatment can not meet the national standard if the concentrations of chlorothalonil were too high.According to the characteristics of physical and chemical properties of chlorothalonil, this thesis also did some further research on removal efficiency of chlorothalonil by PAC adsorption and enhanced coagulation combination process. The result of experiments did in the laboratory showed that when dosage concentration of PAC (both A and B), poly aluminium chloride and PAM are 100mg/L, 10mg/L and 0.1mg/L respectively, to ensure the water after the treatment of PAC adsorption and enhanced coagulation combination processes to meet the national standard, the maximum concentration of chlorothalonil in raw water is 1046.13μg/L. The result of pilot experiments showed that when dosage of PAC (both A and B), poly aluminium chloride and FeCl₃·6H₂O are 100mg/L, 1mg/L and 20mg/L respectively, to ensure the water after the treatment of PAC adsorption and enhanced coagulation combination process to meet the national standard, the maximum concentration of chlorothalonil in raw water are 500μg/L(PAC A) and 750μg/L(PAC B). The results mentioned below both showed that PAC adsorption-coagulation combination process had very high removal efficiency of cholorothalonil in water. Due to rapid purification speed, convenient operation and high security safeguard, it was a very effective emergency treatment process for the cholorothalonil pollution in raw water.