Study On Treatment Of Carbon Tetrachloride Contaminated Groundwater With Aeration Constructed Wetland

Carbon tetrachloride pollution is a typical volatile organic pollution in groundwater,so how to removal it from groundwater is always highly valued.At present,the constructed wetland treatment technology is widely applied and promising to solve this pollution.This paper studies the effect on the removal of carbon tetrachloride from aeration constructed wetlands combined with pH,DO,redox potential,microbial populations and diversity,by building non-aeration SSFCWs and aeration SSFCWs,and considering the effects of three influencing factors of plants,microorganisms and substrates.Main conclusions were followed:（1）Aeration constructed wetland system has a significant effect on the removal of CCl₄ in groundwater.The effect is best when plants combines with microorganisms in aeration constructed wetland system.Considering the situation that the lost of contaminant is 50%before it flows into the wetland,the removal rate of CCl₄ can be increased by 15.97%by aeration,when the removal rate of CCl₄ is 94.15%in the best constructed wetland system which evaluated by Agilent 6890N GC.The horizontal removal rate of CCl₄ meets the reaction kinetic equation y==12.67523e^-0.26462x0.26462x and R2=0.9747.It shows a good correlation.The experiment results show that the best choice for the treatment of carbon tetrachloride is the aeration constructed wetland with synergistic action of reed and microorganisms.（2）The physical and chemical indicators are related to the removal rate of CCl₄in the wetland.The pH is stably maintained between 7.7 and 8.6 in six constructed wetlands and the pH is slightly increased by about 0.5 in the aeration constructed wetlands.Besides,the pH in 5#wetland is slight higher than other wetlands on the effect of Benzalkonium Bromide.The DO of the non-aeration wetland systems is clearly layered,but the DO of the aeration wetland systems is maintained between 6.0and 8.0,and the DO content of each layer is relatively close and stable because aeration can significantly increase the DO content in the wetland.DO is negatively correlated with the concentration of CCl₄,and the correlation coefficient was-0.749,so the correlation is good.There is a close relationship between redox potential and the DO.The DO content increases in the state of aeration,which enlarges the oxidative environment of the wetland.Therefore,the ORP is relatively high and the layer is weakened,and the value tends to be stable,which is consistent with the change of the DO.（3）The aeration system can increase the quantity of microorganisms in the wetland and promote the growth of bacteria and fungi.The number of bacteria in the aeration constructed wetland is twice that of the non-aeration constructed wetland,and the number of fungi in the aeration constructed wetland is 1.68 times that of the non-aeration constructed wetland in mid-September temperature.By using high-throughput Illumina Miseq sequencing,the result is that the abundance and diversity of bacteria is higher than that of fungi in the 6#constructed wetland system.Besides,there is the quantity up to 50%of the bacteria and fungi’s category that needs to be further determined.