Drinking Water Decontamination with Immobilized Enzymes

Nerve agent-degrading enzymes Organophosphorus Acid Anhydrolase (OPAA) and Organophosphorus Hydrolase (OPH) covalently-coupled to solid supports were examined as drinking water system nerve agent decontaminants. Enzymes were bound to azlactone polyacrylamide, glyoxal agarose and glyoxal-aminopropyl controlled-pore glass and tested for stability in unbuffered tap water. Kinetic analyses showed that both enzymes lost activity after covalent immobilization, but the degree of activity loss varied with immobilization method and enzyme type. Superior activity against paraoxon and p-nitrophenyl Soman was seen with OPH-polyacrylamide and OPAA-agarose, respectively, after 5 days tap water storage at room temperature. The azlactone-polyacrylamide coupling method gave the best activity stabilization for both enzymes. Inclusion of immobilized enzyme as a catalytic filter in a circulating, unbuffered, tap water loop system (24 hour hydraulic residence time HRT) demonstrated >99% paraoxon catalysis over a 5 day treatment. This compares to ~6% paraoxon hydrolysis in a control column. These results indicate that immobilized OPH and OPAA can be used successfully to treat contaminated water supplies.