Removal of THMs from Drinking Water Using an Induced Draft Stripping Tower

摘要

The control of disinfection byproducts in drinking water has become increasinglyrnimportant in recent years, especially the group that includes the trihalomethanes. Most ofrnthe control efforts have been directed toward preventing their formation, but this projectrnfocused on removing them after they are formed. Because trihalomethanes are extremelyrnvolatile, it was believed that air stripping would be a feasible method for reducing theirrnconcentration in treated drinking water. Therefore, this study investigated the cost-rneffectiveness of using an induced draft stripping tower to remove some of therntrihalomethanes from the treated water.rnThe results showed that air stripping using an induced draft packed column is indeed arnhighly effective method for removing THMs from water. At air-to-water ratios of 60 orrngreater, the percent removal of total trihalomethanes generally exceeded 90%.rnFurthermore, the stripping operation had no discernable effect on the residual chlorinernconcentration in the treated water.rnChloroform was the easiest THM to remove while bromoform was the most difficult.rnPercentage removals ranged from 69% to 96% for chloroform and 32% to 87% forrnbromoform.rnThe air-stripping operation appears to be very cost-effective, with the operating costrncalculated to range from 0.37 to 1.1 cents per thousand gallons of treated water for thernbest-case and worst-case scenarios, respectively. When the amortized capital costs arernadded in, the total costs range from 0.92 cents per thousand gallons to 4.6 cents perrnthousand gallons for the best and worst-case scenarios, respectively. A realistic total costrnestimate will lie somewhere between the two extremes values, but it is probably closer tornthe 0.92 cents per thousand gallon best-case value than it is to the worst-case one.