Sewage Disposal and Viral Pollution of the Ottawa River

Abstract

Abstract The quality of water in the Ottawa River is being affected by the disposal of increased volumes of sewage into it. Some of the sewage disposal points are situated upstream of beaches and intake points for water purification plants. The aim of this study was to assess the impact of such waste disposal on the virological quality of recreational and drinking waters for the Ottawa area. A total of 132 weekly samples of raw sewage, chlorinated secondary effluents, raw and finished surface waters were examined for viruses from June to December 1977. In addition to these, ten samples of tap water, collected during the first two weeks of April 1978, were also included in this study. Virus concentration from these samples was carried out using the talc-Celite technique developed in the laboratory. Primary human embryonic kidney (HEK) cells and BS-C-1 cells were used for the detection and quantitation of viruses present in the sample concentrates. Virus isolates were identified by their cytopathology, examination under the electron microscope and serology. When 6 1. volumes were processed, nearly all the samples of raw sewage and 54% chlorinated effluent samples were found to be positive for virus. Approximately 50% of the surface water samples were also shown to contain virus using 40 1. sample volumes. Concentrates of some of the potable water samples showed virus-like degeneration in cell cultures. Although this degeneration was found to be transmissible, at this stage it is not possible to say if this effect was in fact due to a viral agent. The following major conclusions were drawn from this study: (a) All three major enteric virus groups were represented in the virus isolates. However, inherent limitations of sample concentration and virus isolation techniques may have resulted in the detection of only a small fraction of the viruses present in the samples. (b) There was no apparent correspondence between the numbers of indicator bacteria and the presence or absence of detectable virus in the samples. (c) Viruses detected in the recreational and raw water samples may be due to the presence of point sources of raw sewage discharge upstream. This could result in the dissemination of human pathogenic viruses through recreational and potable waters.