Study Of Nitrate Removing In Drinking Water Source By The Iron-carbon Micro Electrolysis Method

China is facing severe pollution of drinking water sources, along with various abrupt water pollutions. Hence, the research on the key technology in combat of serious accidental water pollutions will lay a solid foundation for safeguarding the quality of drinking water. When dealing with high concentration of nitrate in the drinking water sources caused by area accidental water pollution, the current treatment process applied in the water supply plant is incapable of removing the nitrate. Thus, the methodology of applying iron carbon micro electrolytic has been chosen as the emergency plan. The iron carbon micro electrolytic method is to utilize the potential difference between zero-valent iron and activated carbon to form a large number of small batteries, thereby removing the nitrate reduction in the water through the electronic transfer. So the system of iron carbon micro electrolysis can start up very quickly, and to remove the nitrates in the water efficiently and effectively.Through single-factor testing and the experiment of continuous flow reaction column, the research studiesthe nitrate-removal effectof micro electrolysis method, to analyze its dynamic mechanism and the optimal conditions, and to conduct the economic benefit analysis, thereby providing technical support for the practical application of micro electrolysis method in water treatment. The results are as follows:(1) Single-factor experiment. To explore whether the iron carbon micro electrolytic method can effectively remove nitrate under neutral conditions,by changing the total iron carbon, iron/carbon ratio and the reaction time, etc. The laboratory water was used, with 100 ml water samples in a 250 ml conical flask, and then adding the iron carbon compounds for reaction. After that, pretreated the water samples and determined the nitrate concentration. The results showed that the pH value is neutral, the amount of iron carbon is 100 g/L, quality ratio of the iron carbon is 3:1, under the condition of 180min-reaction-time, and nitrate removal effect is the best. The initial nitrate concentration is 30 mg/L, and the effluent concentration is 11.60 mg/L. Different amounts of carbon and iron as well as various iron/carbon ratios of reaction system of reaction rate fits well with the curve, the relevance of the R2> 0.9, basic pseudo-first-order reaction kinetics equation.(2) Continuous flow experiment. In order to further study the actual effect of iron carbon micro electrolytic method in nitrate removal, continuous flow experiments were used. According to the results of single factor experiment and the transformation equations for nitrate under micro electrolytic method, the experiment changed water proportion of nitrate ions and hydrogen ions, iron/carbon ratio and the reaction conditions such as hydraulic retention time to experiment. Filled up the response column with iron carbon compounds and watered from above. The water flowed from the bottom under the natural gravity after staying for a certain period of time, and then calculated the nitrate concentration in the water. The results showed that the quality ratio of the iron carbon is 3:1, HRT=60 min, NO3-:H T=l:5, nitrate removal effect is the best. The initial nitrate concentration of 30 mg/L, while the figure turned to 2.60 mg/L in the stable phase.(3) The analysis of application prospect in treating drinking water. According to the result of continuous flow experiment, the iron carbon micro electrolytic method can be used as an emergency plan to prevent the nitrate concentration in drinking water. The application may influence the initial construction of the water supply plant, including its total investment, operation cost and the areas.Analyzing water supply plants with differing construction scales in different iron/carbon ratio and hydraulic retention time regarding economical benefit and land use, the experiment provides a reference for practical applications. The results showed that the hydraulic retention time for 30 min, under different iron/carbon ratio conditions, the initial construction cost increases per rate of about 500000 yuan/(m3/d), operating cost increase of 3.6～95000 yuan/(m3/d). When iron carbon ratio is 3:1, under the condition of different HRT, every 10 min increases, the construction scale of 100000 m3/d,300000 m3/d and 500000 m3/d increases the initial construction cost of 1.58 million yuan,1.58 million yuan and 7.9 million yuan respectively, operation cost increases of 310000 yuan,310000 yuan and 1.57 million yuan respectively. Under the same conditions, reaction pool area increases with the hydraulic retention time and the construction scale, the higher proportion of iron powder, the smaller reaction pool area, and the proportion of reaction pool area shall not exceed 43% of the whole land.