Removal of Mixed BTEX and Heavy-Metals Pollution

摘要

At a site polluted with a mixture of BTEX and heavy metals, different remediation techniques were applied. In the source, the bulk of the BTEX contamination was removed by pump-and-treat (72% BTEX removed) and soil vapor extraction (52% BTEX compounds removed) from the saturated and unsaturated zone respectively. For remediation of the rest of the BTEX compounds and heavy metals in the plume, natural attenuation and phytoremediation were applied. It was investigated if the TEX degradation could be coupled to in situ bioprecipitation by sulfate-reducing bacteria of the heavy metals Zn and Ni for a part of the site with a high (GP66: 45000 ppb BTEX, 938 ppb Zn, 284 ppb Ni), medium (GP48: 16000 ppb BTEX, 60 ppb Zn, 49 ppb Ni) and low (GP59: 250 ppb BTEX, 1226 ppb Zn, 113 ppb Ni) concentration of BTEX and heavy metals. Therefore batch degradation tests with aquifer material and groundwater (containing in situ TEX concentrations) from the locations GP48, GP59 and GP66, sulfate as an electron-acceptor, and different carbon sources such as TEX (in the groundwater), lactate, HRC~R, and molasses were started. Neither TEX degradation nor removal of heavy metals was observed in the heavily polluted GP66 part of the site. For GP48 and GP59 a fast removal of Zn was observed in the presence of all the carbon sources. However, Ni was bioprecipitated only after the addition of lactate or TEX and not with the other carbon sources. It was also obvious that degradation of the TEX coincided with the bioprecipitation of the heavy metals. Although the other carbon sources clearly stimulated the bioprecipitation of the heavy metals, they inhibited the degradation of TEX.