Quantification of Microbial Sources in Drinking-Water Catchments

A detailed literature review was undertaken of pathogen prevalence and concentration in fecal matrices and sewage effluent. Most of the reports described microbial prevalence rather than concentration and the majority of studies were from developed countries in Europe, the Americas, and Australasia. Prevalence varied from nondetected to up to 100% and reported values varied between studies for the same host and matrix. Juvenile animals typically had higher reported pathogen prevalence than adult animals. The reported prevalence of pathogens was usually higher in domestic animals than wildlife. Extensive variation in reported pathogen concentrations was observed covering up to four orders of magnitude for the same matrix. Similar to the trends in prevalence, the reported concentration of pathogens was higher among juvenile animals than among adults and generally higher in domestic animals than in wildlife. The source of variation was highest for reports of concentrations in feces and lowest for reports of the sewage effluent, presumably because the latter is effectively a pooled sample. Reported concentrations of pathogens in similarly treated sewage effluent were reasonably consistent between studies from different parts of the world, although it is noted that the countries !from which the reports originated had similar socioeconomic characteristics. The priorities for reducing pathogen presence in water-supply catchments are to adequately treat domestic sewage before discharge and to improve the management of domestic animals to reduce levels of infection.