Disinfection of municipal secondary-tertiary effluents with ozone: five recent pilot plant studies

摘要

Economical large scale disinfection of wastewater by ozone is a rapidly approaching reality. Factors influencing the growing acceptance of ozone disinfection are related to the shortoomings of chlorine and the decreasing cost of ozonation. Chlorine has basic disadvantages as a disinfectant, especially with respect to inactivation of viruses, toxicity of chlorinated effluents and safety. Ozone overcomes these technical problems and at the same time is becoming economically competitive. Currently, commercial techniques for ozone generation have demonstrated major improvements over older technology. However, there was an apparent need for more economical methods of application and this is the area addressed. The development of a low cost, high efficiency, low maintenance, contacting technique for disinfection has been accomplished on a pilot scale. Disinfection studies were performed on secondary biologically treated effluents and on a tertiary treated effluent in 10 and 25 gpm pilot contactors with 2 to 5 mg/l ozone. Average fecal coliform counts always averaged less than 200/100 ml and in some cases approached zero. Contact time was less than 60 seconds and significant reductions in turbidity and color were observed. Work is continuing in defining the factors which limit ozone disinfection of wastewater and in scaling up the pilot plant to commercial levels.