Water Supply Vol 2 No 3 pp 23–28 © IWA Publishing 2002
Hygienic risk assessment by monitoring pathogens in municipal sewage
C.-H. von Bonsdorff*, L. Maunula**, R.M. Niemi***, R. Rimhanen-Finne****, M.-L. Hänninen***** and K. Lahti******
*Department of Virology, Haartman Institute, PO Box 21, FIN-00014 Helsinki University and HUCH Laboratory Diagnostics, Helsinki, Finland
**Department of Virology, Haartman Institute, PO Box 21, FIN-00014 Helsinki University and HUCH Laboratory Diagnostics, Helsinki, Finland
***Finnish Environment Institute, PO Box 140, FIN 00251 Helsinki, Finland
****Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, PO Box 57, FIN-00014 Helsinki University, Helsinki, Finland
*****Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, PO Box 57, FIN-00014 Helsinki University, Helsinki, Finland
******Finnish Environment Institute, PO Box 140, FIN 00251 Helsinki, Finland
ABSTRACT
The purpose of this study was to monitor the levels of human enteric viruses and enteric protozoa and to relate their presence to the microbes used as hygienic quality indicators in domestic sewage from a small community in Finland during a period of one year. Genome-based sensitive detection methods for the pathogens selected (astro- and Norwalk-like viruses, Giardia and Cryptosporidium) have become available only recently and thus no earlier data was available. The effluent sewage is delivered into a river that serves as raw water for a larger town and the pathogens therefore constitute a health risk. The results showed that all the monitored pathogens could be detected, and that enteric viruses were present at considerable concentrations in sewage. High concentrations of astrovirus in raw sewage were observed during a diarrhea epidemic in the local day-care centre. The presence of viruses did not correlate with the monitored bacterial indicators of faecal contamination (coliforms, E. coli and enterococci) or with bacteriophages (somatic coliphages, F-specific RNA phages and B. fragilis phages). Giardia cysts and Cryptosporidium oocysts were detected from one sample (1/10) each.
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