(506b) Advanced Oxidation Pre-Treatment of Benzalkonium Chlorides Prior to Biological Treatment

Advanced oxidation pre-treatment of
benzalkonium chlorides prior to biological treatment.

Adnan Hossain Khan^a, Jing Wan^a,
Mark Sumarah^b, Sheila M. Macfie^c, Madhumita B. Ray^a,*.

^aDepartment of
Chemical and Biochemical Engineering, University of Western Ontario, London,
ON, N6A 5B9, Canada.

^bAgriculture and
Agri-Food Canada, London, ON, N5V 4T3, Canada.

^cDepartment of
Biology, University of Western Ontario, London, ON, N6A 5B7, Canada.

Abstract:

Benzalkonium chlorides
are a common group of antibacterial cationic surfactants that are found in
wastewater effluents and biosolids. Widely used benzyl dimethyl
dodecyl ammonium chloride (BDDA) and benzyl dimethyl
tetradecyl ammonium chloride (BDTA) are biodegradable but their mixtures are
persistent to biodegradation. The research evaluated an advanced oxidation
treatment (AOT) as a pre-treatment to enhance the biodegradability of a BDDA
and BDTA mixture and to reduce toxicity for further biological treatment of
mixtures. Chemical oxidation using ozone and hydrogen peroxide at different pH
was tested and the experimental conditions were optimized using a central
composite design (CCD). Preliminary experiments showed that pH played an
important role for the removal of the BDDA and BDTA mixture at initial
concentrations of 50:25 mg L^?1 in presence of ozone and hydrogen
peroxide (Fig. 1). A synergistic effect of increased removal rate was observed
by adding hydrogen peroxide to ozone, although hydrogen peroxide by itself did
not degrade BDDA but partially degraded BDTA (≤ 25%) during the same
treatment time. Optimization of AOT using CCD showed greater than 90% removal of
the initial BDDA and BDTA mixture at pH 10 or above with 150 mg L^?1 hydrogen
peroxide and 0.8 mg L^?1 ozone. Intermediates formed during AOT are
being analyzed by HPLC-MS. To evaluate AOT as a pre-treatment prior to
biological treatment, the biodegradability of the pre-treated effluent, in
which 90% of the parent BDDA: BDTA mixture was removed, is being determined
using the ratio of biological oxygen demand to chemical oxygen demand and a toxicity
test is being performed using fresh water algae species.

Keywords: Advanced oxidation treatment;
benzalkonium chloride; cationic surfactants; benzyl
dimethyl dodecyl ammonium chloride; benzyl dimethyl
tetradecyl ammonium chloride.

Fig.1. Percentage removal of benzalkonium chlorides
over time. The AOTs were conducted at different pH, temperature (°C), O₃
concentration in liquid phase (mg L^?1) and H₂O₂
concentration in mg L^?1; (a) BDDA and (b) BDTA.