Color removal from Churchill River water using ozonation, sand filtration and carbon adsorption

Abstract

A water treatment process composed of an ozone reactor, a rapid sand filter and a granular activated carbon filter, was employed to reduce the color of Churchill's drinking water supply. Bench scale treatment tests were performed monthly over a 1 year period, while operating parameters such as ozone dosages and residence times were varied. In order to compare treatment efficiencies and to simulate conditions at the treatment facility in Churchill, testing was conducted at 25oC and at 4oC. Using the results from this study and an extensive literature review, it was concluded that ozone and a granular activated carbon filter reduce color to a greater degree than a carbon filter by itself. A reduction in temperature from 25oC to 4oC or a reduction in empty bed contact times from 20 minutes to 10 minutes in the filter were each shown to decrease the quality of the treatment effluent. This treatment train reduced the apparent color of the raw Churchill River water to below Canada's aesthetic objective limit of 15 color units, in all months except May.