Field and laboratory studies concerning the detection of enteric viruses in either settled or disinfected secondary sewage
Churn, C. Calvert
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The demand for potable water may be culminating in a compromise on what constitutes a "safe" drinking water due to the rapidly approaching need to utilize recycled waters. The elimination of viruses pathogenic to humans from recycled waters will depend on the removal efficiencies of treatment processes and the sensitivity of detection methodologies. Enteric viruses can survive current wastewater treatment practices, and some even persist for long periods of time in natural waters. The objectives of this investigation were threefold: first, to construct a virus concentrator suitable for sampling secondary sewage treatment plant effluents; second, to sample the effluent of trickling filter sewage treatment plants prior to chlorination to determine the remaining amount of enteric viruses; third, to determine the virus removal efficiencies of a final settling and chlorination operation by using bench-scale simulations of the two units. Viruses were not detected in any of the secondary effluents of three trickling filter plants samples. However, these results may have been obtained because the level of viruses was below the minimum detection limits of the virus concentrator that was constructed. Also, if viruses were present, the high pH elution process may have been deleterious, or the BGM host cell was incompatible. Detention times in the model system studies of a final sedimentation basin and chlorine contact chamber were based on Rhodamine WT dye studies of plant-scale units. These studies suggested that 98.5 to 100 percent of the enteric viruses contained in the actual plant effluent would be removed or inactivated by the combination of final settling and chlorination.
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