A tertiary treatment plant and an ultraviolet disinfection chamber were installed following an activated sludge plant at the municipal sewage treatment plant in St. Michaels, Maryland. The multiple-tube fermentation technique was used to determine the total coliform MPN Index after varying exposures to ultraviolet radiation. Batch tests were sampled at various intervals under constant radiation and flow-through tests were sampled before and after undergoing radiation. The standard to be met was an MPN of not more than 70 per 100 ml. In flow-through tests this was usually achieved with a flow not in excess of 40,000 gallons per day, with a turbidity of less than 11 JTU, using sixteen germicidal 36 watt ultraviolet lamps, an energy application of .035 KWH/1000 gallons. The absorption of ultraviolet radiation, as measured by the absorption coefficient, was much more dependent on COD than on turbidity, indicating the appearance of the effluent is not the best criterion for estimating the rate of U.V. treatment unit.