Sewage effluent as a source of Campylobacter sp. in a surface water catchment.

Campylobacter sp. can regularly be found in wastewater-affected surface waters. The occurrence of Campylobacter sp. in rivers, treated sewage and combined sewer overflows was analysed in a catchment with sparse annual precipitation. During regular treatment the reduction efficacy for Campylobacter sp. varies between 1.75 and 3.5 log(10). However, Campylobacter sp. concentrations do not increase downstream in the river as more sewage treatment plants discharge into it. During rain events, the Campylobacter sp. concentration in the river upstream of any sewage plant rises and in the sewer overflow water it is more than 150-fold higher than the average concentration in the river water at the river mouth. The highest Campylobacter sp. loads and the highest risk of infection occur during summertime after heavy rainfall. Risk management strategies should focus on problems regarding water scarcity, reuse of sewage effluent and the impact of heavy rain events.