Arsenic is a major toxic pollutant of concern for the human health. Biological treatment of arsenic contaminated water is an alternative strategy to the prevalent conventional treatments. The biological treatment involves a pre-oxidation step transforming the most toxic form of arsenic, As (III), to the least toxic form, As (V), respectively. This intermediate process improves the overall efficiency of total arsenic removal from the contaminated water. As (III) oxidation by the chemoautotrophic bacterium Thiomonas arsenivorans strain b6 was investigated in a fixed-film reactor under variable influent As (III) concentrations (500-4000mg/L) and hydraulic residence times (HRTs) (0.2-1day) for a duration of 137days. During the entire operation, seven steady-state conditions were obtained with As (III) oxidation efficiency ranging from 48.2% to 99.3%. The strong resilience of the culture was exhibited by the recovery of the bioreactor from an As (III) overloading of 5300±400mg As (III)/Lday operated at a HRT of 0.2day. An arsenic mass balance revealed that As (III) was mainly oxidized to As (V) with unaccounted arsenic (≤4%) well within the analytical error of measurement. A modified Monod flux expression was used to determine the biokinetic parameters by fitting the model against the observed steady-state flux data obtained from operating the bioreactor under a range of HRTs (0.2-1day) and a constant influent As (III) concentration of 500mg/L. Model parameters, k=0.71±0.1mg As (III)/mg cellsh, and Ks=13.2±2.8mg As (III)/L were obtained using a non-linear estimation routine and employing the Marquardt-Levenberg algorithm. Sensitivity analysis revealed k to be more sensitive to model simulations of As (III) oxidation under steady-state conditions than parameter Ks.
|Number of pages||9|
|Journal||Science of the Total Environment|
|State||Published - Aug 15 2012|
Bibliographical noteFunding Information:
The research work was supported by the Kentucky Science Engineering Foundation through a R&D Excellence grant awarded to Yi-Tin Wang under agreement no. KSEF 148-502-03-71 . The authors would also like to thank the Department of Civil Engineer at the University of Kentucky for additional financial support in the form of Teaching Assistanceship during the course of the research work.
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- Waste Management and Disposal