Enzymatic Approach to Waste Minimization in a Cattle Dipping Operation:  Economic Analysis

Cattle dipping liquid containing the pesticide coumaphos must be discarded when potasan, a dechlorination product of coumaphos, accumulates. An enzymatic strategy is examined in which the enzyme parathion hydrolase is used to selectively hydrolyze potasan relative to coumaphos, therefore permitting the extended use of the cattle dipping liquid and reducing the overall generation of waste from the cattle dipping operation. A large-scale experiment was performed to confirm that the observed rate of potasan hydrolysis is an order of magnitude larger than the rate of coumaphos hydrolysis. A mathematical model was adapted to permit an economic comparison of the enzymatic waste minimization approach to the alternative of dumping the potasan-containing dipping liquid and recharging the dip vat with fresh coumaphos. This analysis demonstrates that because the amount of enzyme required is small and the cost of the coumaphos pesticide is large, it is almost always economical to extend the lifetime of the dip vat by the addition of the enzyme.