Air-stripping And Reduction For The Simulated Treatment Of The Groundwater Polluted By Chlorinated Aliphatics Hydrocarbons At Contaminated Sites

Chlorinated aliphatics hydrocarbons (CAHs) as good organic solvent are widely used in industry. Now many groundwater pollution sites are badly polluted due to improper handling of chlorinated hydrocarbon solvents, which results in a serious threat to human health and ecological security. Due to soil and groundwater contamination in Brownfield, the redevelopment of contaminated Brownfield may often pose health risk to public. So it is particularly important to remove the chlorinated hydrocarbons in groundwater.Air stripping in sieve plate tower for the treatment of the water polluted by CAHs and researching on reduction effect of CAHs by Fe/C/Cu were studied, which have important theoretical significance to carry on the research of the Brownfields. The results are as follows:(1) The various air-stripping services such as graduated cylinder, bubble column (batch), bubble column (continuous) and sieve plate tower were choosen in the study. High removal efficiency in a graduated cylinder demonstrated that air-stripping is available for reduction of CAHs. The removal efficiency in sieve plate tower is the highest.(2) Air stripping in sieve plate tower for the treatment of the water polluted by CAHs such as perchloroethylene(PCE) and trichloroethylene(TCE) were studied.①After air stripping, PCE concentration declined from 25.68 mg/L to 0.62 mg/L, and removal rate amounted to 97.59%; Gas-liquid ratio affected PCE removal rate obviously and the optimum gas-liquid ratio was around 250; Initial concentration influenced the removal effect slightly; Waste water was better treated by 4 plates column; Experimental data followed one-order decay model very well.②CE concentration declined from 97.32 mg/L to 2.794 mg/L, and removal rate amounted to 97.13%; Gas-liquid ratio affected TCE removal rate obviously and the optimum gas-liquid ratio was around 230; Initial concentration influenced the removal effect slightly; Waste water was better treated by 6 plates column; Experimental data also followed one-order decay model very well.(3) The reductants such as Fe, Fe/Cu and Fe/C/Cu were compared in this study. The removal of CAHs was not obvious in the Fe and Fe/Cu systems, while the greatest reduction efficiency was achieved by Fe/Cu/C system, as a result of synergetic effect of microelectrode of Fe/Cu and Fe/C. Neutral condition was appropriate for CAHs degradation, and acidic system favored slightly CAHs dechlorination compared with alkaline system. Then we observed some transformation of CAHs in neutral system, as evidenced by the presence of reaction products.