Seasonal Variation and Correlation of Escherichia coli and Salmonellae in a Full-Scale Constructed Wetland for Wastewater Treatment in China

Constructed wetlands (CWs) have proven to be a promising treatment alternative for developing countries. Recently attention has been focused on the ability of CWs to reduce human pathogens in wastewater. In this study, indicator microorganisms (Escherichia coli) and pathogens (Salmonellae) were analyzed from a full-scale surface flow constructed wetland situated in China. The results showed that for E. coli the maximum removal efficiency of this system was achieved in spring at (85.3±14.3) %, and minimum in autumn at (68.1±31.3) %; for Salmonellae the maximum was achieved in summer at (54.1±13.7) % and minimum in autumn at (35.3±61.7) %. In most cases, the concentration of Salmonellae in influent and effluent was markedly higher than that of E. coli. There was no significant correlation between the concentration of E. coli and Salmonellae. The behavior difference between indicator and pathogenic microorganisms in constructed wetlands indicates that the classic indicators may not provide an adequate prediction of the presence of pathogens.