Gamma rays vs the E. coli monster (and other tales)

Experiments were carried out on the use of a gammacell 220 for disinfection of sewage effluent at Burlington, Ontario. The design and operation of the irradiator are discussed. Monitoring of effluents was carried out for coliforms, streptococci, salmonellae, viruses, and bacteriophages. At a dosage of 50,000 rads coliforms were reduced 97.9 percent, fecal coliforms 83.9 percent, and fecal streptococci 46 percent. Inactivation of coliforms approached that level obtained with efficient chlorination but that for fecal coliforms and fecal streptococci was considerably lower. On the whole, results demonstrated that application of gamma radiation treatment on a practical scale has an advantage over chlorination practices, in that a consistent bacterial kill is obtained. A study of costs indicated that irradiation treatment is somewhat more expensive than chlorination