THE INFLUENCE OF ORC? INJECTION ON IN SITU BTEX BIODEGRADATION AND ON ENDOGENOUS MICROORGANISMS

摘要

A demonstration pilot-scale study is being conducted at a BTEXcontaminated site to evaluate the use of ORC? (Regenesis) for enhanced bioremediation. More specifically, the influence of ORC?-injections on the chemical composition of the groundwater and on the endogenous micro-organisms at the tested site are being studied. Groundwater pollution was characterized by MIP-probing and chemical analyses on groundwater samples. Based on labscale feasibility tests it was found that an aerobic and micro-aerophilic microbial BTEX-degrading potential is present in the aquifer material of the site. A limited oxygen availability reduced the degradation rate, which suggests that an increase of the oxygen concentration can enhance the BTEX-degradation. The ORC? has been applied to the site in January 2003 and the evolution of chemical and microbial parameters is being monitored since. The monitoring plan foresees monitoring of the in situ parameters (pH, ORP, dissolved oxygen, temperature and conductivity) and of some chemical parameters (e.a BTEX, nutrients, Mg). The effect of the ORC?-injection on the endogenous microbial population present in the aquifer at the site, is followed by microbial (platings) and molecular techniques (PCR-DGGE using general eubacterial primers and BTEX-specific primers). For this purpose, in situ mesocosms have been developed and 16 of these mesocosms were installed in 4 different monitoring wells at the site. At the moment only preliminary monitoring results are available indicating (I) an increase of the dissolved oxygen concentration up tot 45 mg/L, (II) pH-increases up to pH 10.5 and (III) the presence of BTEX-degrading micro-organisms at the site.