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Use of a lux‐modified bacterial biosensor to identify constraints to bioremediation of btex‐contaminated sites

Sediment and groundwater samples obtained from a benzene, toluene, ethylbenzene, and xylene (BTEX)‐contaminated site were screened, using a bioluminescence‐based (lux gene‐marked) bacterial biosensor, to identify constraints to site remediation. Through a series of sample manipulations and linked biosensor responses, constraints to BTEX remediation such as adverse pH, presence of nonvolatile organic contaminants, and the presence of heavy metals were investigated. Conventional chemical analysis (gas chromatography, inductively coupled plasma mass spectroscopy) was used to confirm the reliable performance of the biosensor and to identify its potential contribution to site management to ensure effective remediation. The toxicity results of the biosensor were expressed in % maximum bioluminescence calculated against a blank of double deionized water with pH adjusted to 5.5. Untreated samples caused reductions in percentage bioluminescence from 10 to 95%. Water sample W1, containing a total BTEX concentration of 30,595 μg/L caused the highest decrease in bioluminescence (5.78%). This toxicity was significantly reduced after elimination of volatile organic compounds (VOCs) (42.01%) and bioluminescence was further increased to 87.80% after removal of total organic matter. This suggested that VOCs were not the only toxic organopollutants present. Water samples giving high values of bioluminescence contained BTEX concentrations of 17 to 31 μg/L.