Biotreatment of Surfactant Flush Wastewater from Wood Treatment Soil

The high cost of surfactant enhanced aquifer remediation (SEAR) could be reduced if contaminants in the extracted surfactant flushing water could be biodegraded, and the surfactant reinjected. To test this concept, ex situ biotreatment using immobilized bacteria was simulated in laboratory columns. Nonionic surfactant solutions of 1,000-5,000  mg/L Tergitol NP-10 (TNP10) were flushed through contaminated soil collected from a wood-treatment site. The highest TNP10 dose increased the effluent concentrations of tetrachlorophenol (TeCP) and tetrachlorohydroquinone (TCHQ) by about 3 and 16 times, respectively. These wash solutions were then treated by the aerobic bacterium Sphingomonas chlorophenolica RA2 immobilized in polyurethane foam. The immobilized bacteria were capable of degrading pentachlorophenol, TeCP and TCHQ in soil flushing wastewater containing up to 4,900  mg/L TNP10. Surfactant sorption to the biotreatment columns occurred, but these losses decreased over time as the sorption capacity of the foam was exhausted. The results suggest that SEAR wastewater could be biotreated, thus enabling reinjection of the surfactant.