VIRUSES AND WATER - PROBLEMS, DETECTION, AND CONTROL

Secondary effluent of wastewater treatment plants contains a high numb er of viruses and other pathogens, which pose a health risk to the pop ulation, especially when receiving waters are used for bathing and swi mming, or for growing shellfish. In areas with a high density of popul ation, where drinking water supply is dependent on surface waters and contaminated rivers are the primary source of drinking water, failure of the filtration or of the disinfection step, or of any other ''barri ers'' supposed to warrant safe potable water, will increase the risk o f health hazard for the consumer. We have compared the efficiency of v iral elimination in secondary effluent by flocculation, uv irradiation and membrane filtration taking naturally occurring, or additionally s eeded f2 phages, as indicator for viruses. Flocculation decreased the number of phages present in secondary effluent by more than two logs. If combined with uv irradiation, the elimination reached five addition al logs. Membrane filtration eliminated essentially all naturally occu rring phages. Improvement of the quality of surface waters calls for a refinement of detection methods for viruses. We have found that the p olymerase chain reaction (PCR) might be used for detecting viruses in surface waters.