43    EVALUATION OF THE REMOVAL OF AROMATIC AND
HALOGENATED UNSATURATED HYDROCARBONS
FROM SYNTHETIC WASTEWATER BY ENZYME
CATALYZED POLYMERIZATION
L. Al-Kassim, Research Associate
Department of Chemistry and Biochemistry
K.E. Taylor, Associate Professor
Department of Chemistry and Biochemistry
J.K. Bewtra and N. Biswas, Professors
Department of Civil and Environmental Engineering
University of Windsor
Windsor, Ontario, Canada
INTRODUCTION
Arthromyces ramosus peroxidase (ARP), like many other peroxidases, catalyzes the oxidation of a
wide variety of aromatic compounds by reduction of hydrogen peroxide. A system representative of
the common mode of peroxidase action is depicted by the following mechanism:
E-Fe (III) + H202 - Compound I + H20 (1)
Compound I + AH2 -» Compound II + AH" (2)
Compound II + AH2 - E-Fe (III) + AH* + H20 (3)
The peroxide (and certain other peroxidic agents) and the resting state of the enzyme, E-Fe (III),
together form "Compound I," [Fe (V).O], which is oxidized two electrons above E-Fe (III) and carries
the peroxidic oxygen. This Compound I is then reduced in a one-electron step to "Compound II," [Fe
(IV)], which cycles back to the resting E- Fe (III) by accepting another electron.1 The two donor
molecules AH2 are released as radicals (AH"). In general the donor specificity of the peroxidase is low
and free radicals formed will diffuse from the active center of the enzyme into solution where they
combine to form higher oligomers. At peroxide concentrations of several millimolar "Compound III"
is formed. It has the structure [Fe(II).02 or Fe(III).02~] and is peroxidatically inactive. The polymers
formed tend to be less soluble in water than their monomeric precursors and can be precipitated from
solution. Klibanov et al.2 and Maloney et al.3 and more recently Nicell4 demonstrated the effectiveness of this approach as a water treatment strategy for the polymerization and precipitation of
substituted phenols and aromatic amines from wastewater and drinking water using horseradish
peroxidase (HRP). In the presence of additives such as polyethylene glycol Wu et al.5 demonstrated
that the amount of HRP required was reduced by at least 30-fold for the working range of 1.0-10 mM
usually found in industrial wastewater.
The potential advantages of an enzyme-based treatment over conventional biological treatment
include: application to a broad range of compounds including those which are biorefractory; operation over wide temperature; pH and salinity ranges; reduction in sludge volume (no biomass); no
shock loading or delays associated with shutdown/startup; and a better defined system with simple
process control. Potential advantages of an enzyme-based treatment over chemical/physical processes
are: operation under milder, less corrosive conditions; operation in a catalytic manner with reduced
consumption of oxidants; and reduced amounts of adsorbed materials, such as charcoal for disposal.
Based on the foregoing, it might, for certain industrial waste sources, be possible to replace conventional biological treatment with the enzyme-based process. Alternatively, the latter might be used in
conjunction with the conventional method as a primary treatment at the source to reduce the burden
on the biological treatment system or as a tertiary treatment to deal with biorefractory compounds.
48th Purdue Industrial Waste Conference Proceedings, 1993 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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