Biodegradation of the surfactant linear alkylbenzenesulfonate in sewage-contaminated groundwater: A comparison of column experiments and field tracertests

Transport and biodegradation of linear alkylbenzenesulfonate (LAS) in sewag e-contaminated groundwater were investigated for a range of dissolved oxyge n concentrations. Both laboratory column and an 80-day continuous injection tracer test field experiments were conducted. The rates of LAS biodegradat ion increased with increasing dissolved oxygen concentrations and indicated the preferential biodegradation of the longer alkyl chain LAS homologues ( i.e., C-12 and C-13) and external isomers (i.e., 2- and 3-phenyl). However, for similar dissolved oxygen concentrations, mass removal rates for LAS ge nerally were 2-3 times greater in laboratory column experiments than in the field tracer test. Under low oxygen conditions (<1 mg/L) only a fraction o f the LAS mixture biodegraded in both laboratory and field experiments. Bio degradation rate constants for the continuous injection field test (0.002-0 .08 day(-1)) were comparable to those estimated for a 3-h injection (pulsed ) tracer test conducted under similar biogeochemical conditions, indicating that increasing the exposure time of aquifer sediments to LAS did not incr ease biodegradation rates.