A scale-up investigation of ultraviolet disinfection as an alternative to chlorination for sewage effluents

Secondary effluents from treatment facilities in southern Ontario were circulated through two systems (of 20 and 40 imperial gallons capacities) simulating weirs in secondary clarifiers. The depth of flow over the weirs was less than 0.5 cm. The effluent was irradiated with 254 nm UV light from mercury arc lamps equipped with reflectors. Six weeks of continuous operation proved that fouling of the lamps was not a problem. A dose of 6 x 10-8 einsteins/ml killed 99% of the indicator organisms. The treated effluent was not toxic to trout, unlike similar effluent treated with chlorine. Cost estimates are given for a 1 M.G.D. plant. (E.C.B.)