Author(s)

T. G. Ellis, X. Huang & S. K. Kaiser

Abstract

The fate and biodegradation of two xenobiotic compounds, linear alkylbenzene sulfonate (LAS) and alkyl sulfate (AS), were investigated in laboratory and field activated sludge systems. Two 1-L porous pot (65 µ stainless steel mesh) reactors were fed synthetic wastewater (200 mg COD/L including 2 mg/L LAS and 1 mg/L alkyl sulfate) to evaluate the influence of specific operating conditions (i.e. hydraulic retention time, HRT, and solids retention time, SRT) on the measured rate of biodegradation. The reactors were operated in parallel under a constant SRT of 10 d, and HRTs of 2, 4, 6, and 12 h. Subsequently, the reactors were operated under a constant HRT of 6 h, and SRTs of 3, 6, 10, and 15 d. The extant kinetic parameters obtained from respirometric experiments suggest that the HRT had little impact on the measured kinetic parameters ( µ ˆ = 0.14 ± 0.06 h-1, KS = 0.4 ± 0.3 mg COD/L, Y = 0.67 ± 0.02 mg biomass COD formed/mg LAS COD utilized and µ ˆ = 0.0.25 ± 0.01 h-1, KS = 0.35 ± 0.07 mg COD/L, and yield = 065 ± 0.02 mg biomass COD formed/mg AS COD utilized) at a constant SRT of 10 d. The SRT had a more noticeable effect on the measured biodegradation kinetics (e.g., Y increased from 0.50 ± 0.08 to 0.66 ± 0.05 mg/mg and 0.49 ± 0.07 to 0.61 ± 0.07 when the SRT increased from 3 to 10 d at a constant HRT of 6 h for LAS and AS, respectively). Extant kinetics for LAS biodegradation were measured in the field at three activated sludge wastewater treatment plants operated at different conditions. The field results were similar to the results from laboratory systems operated to simulate the field conditions. Using the COD fraction to calculate the competent biomass concentration, the field measured extant kinetic parameters were used to accurately predict effluent concentrations within 2% on average at one plant and within 4 µg/L at two other plants. Day to day predictions were not as accurate, possibly due to the non-steady-state nature of the field systems. Keywords: linear alkylbenzene sulfonate, alkyl sulphate, biodegradation, kinetics, competent biomass, respirometry, activated sludge.

Keywords

linear alkylbenzene sulfonate, alkyl sulphate, biodegradation, kinetics, competent biomass, respirometry, activated sludge.