Biodegradation of Sodium Alkylbenzenesulfonates by Soil Perfusion Method

Abstract

In order to investigate the decomposition of sodium alkylbenzenesulfonates(LAS) and other surfactants with soils, a soil perfusion method has been applied. The degree of degradation of the surfactants was evaluated by measuring the amount of ferroin-reagent-active substance(FRAS) and/or of total organic carbon(TOC) in the perfusion fluid.
The following results were obtained:
1) The biodegradation of the surfacta nts started after adsorption on soils. The biodegradation rate was in the order SDS>A0S>>LAS>ABS. This result was consistent with that determined by die-away tests.
2) At high LAS conce ntrations (50 and 100 m g/l), the biodegradation occurred after some induction period, but further added LAS was readily degraded without induction period.
3) The degradability of LAS was affected by its alkyl-chain length. Although the period of acclimation of C12 LAS was longer than that of C10-13 LAS, nearly the same rates of degradation were observed for both LAS's.
4) The period of disappearance o f FRAS was shorter than that of TOC: at 50 m e of LAS, total FRAS disappeared in 10 days, but TOC disappeared in about 50 days.
5) The disappearance of LAS in the soil perfusion was affected by the chemical and physical properties of soils. The amount of LAS adsorbed on the Koganei soil (clay loam)was larger than that on the Saku soil (sandy loam), and the biodegradation of LAS occured more readily in the former soil.