Study On The Removal Of Typical Chlorinated Hydrocarbons In Groundwater By Aeration And Adsorption

In recent decades,with the development of chemical industry,the production of artificial organic compounds is increased.They are widely used in pesticide,leather,medicine and chemical field.Unfortunately,because of the improper storage,organic compounds enter the groundwater by volatilization,disacharge and leakage.Some results show that chlorinated hydrocarbon is the main organic pollutant in groundwater in China,especially carbon tetrachloride?CT?,trichloroethylene?TCE?,tetrachloroethylene?PCE?and chloroform?CF?,and it is a great threat to groundwater quality.In this paper,we chose the typical chlorinated hydrocarbon mentioned above as the research objects,the four chlorinated hydrocarbons have a high Henry coefficient,which means they can be easily removed by aeration.Firstly,we found that temperature and gas water ratio are the most important factors affecting the efficiency of aeration.At14 degree centigrade,when the concentration of the typical chlorinated hydrocarbons is four times higher than Chinese drinking water standards,gas water ratio is recommended to be>40?5?12?7,and when the concentration of the typical chlorinated hydrocarbons is nine times higher than Chinese drinking water standards,gas water ratio is recommended to be>40?12?>20?14.In ordor to reduce gas water ratio,we designed a packing tower in our labrotory.We found the best filling ratio was 15%,and at 14 degree centigrade,when the concentration of the typical chlorinated hydrocarbons is four times higher than Chinese drinking water standards,gas water ratio of packing tower is recommended to be 15?4?7?4,and when the concentration of the typical chlorinated hydrocarbons is nine times higher than Chinese drinking water standards,gas water ratio of packing tower is recommended to be>20?10?14?10.We compared the results with empty tower,for different pollution concentrations of chlorinated hydrocarbon,different aeration methods were proposed.In this paper,we studied the adsorption kinetics and adsorption isotherm of these four chlorinated hydrocarbons,and we found that the kinetics of the adsorption of these four chlorinated hydrocarbons on activated carbon was in line with Lagrange's first-order kinetic equation,and the rank of activated carbon adsorption speed was tetrachloroethylene>trichloroethylene>carbon tetrachloride>chloroform.Adsorption isotherm was in compliance with the Freundlich and Langmuir isotherm,when effluent concentration of chloroform,carbon tetrachloride,trichloroethylene,tetrachloroethylene meet Chinese drinking water standard limit value,the corresponding equilibrium adsorption quantity is 0.52,1.93,8.33,16.27 mg/g.From the penetration curve,we could say that the penetration curve of chloroform is easier to be penetrated?12000 beds volume?,followed by carbon tetrachloride?16440 bed volume?,trichloroethylene?20010 beds volume?,tetrachloroethylene?22440 beds volume?.Moreover,through the penetration curve of four chlorinated hydrocarbons adsorbed by activated carbon adsorption column,it was found that when C_t/C₀ is less than 0.5,the adsorption capacity utilization is low.So when we use activated carbon column to adsorb the four chlorinated hydrocarbons,the column should be connected in series and we need to control the operating conditions.For example,the utilization rate of the adsorption capacity of activated carbon column is enhanced when the effluent from the first column in a high concentration.According to this study,aiming at the problem of excessive chlorinated hydrocarbons in drinking water plants,aeration as the main process and combined process of aeration-activated carbon column was proposed.Finally,the pilot experiment was carried out,and technical support was provided for demonstration project to further improve the drinking water safety guarantee capacity of our countr y and improve the drinking water quality of urban residents.