Riparian Attenuation of Faecal Microbes

Disclaimer While every effort has been made to ensure the information in this publication is accurate, the Ministry of Agriculture and Forestry does not accept any responsibility or liability for error or fact omission, interpretation or opinion which may be present, nor for the consequences of any decisions based on this information. Any view or opinions expressed to not necessarily represent the official view of the Ministry of Agriculture and Forestry. The information in this report and any accompanying documentation is accurate to the best of the knowledge and belief of the Consultant acting on behalf of MAF Policy. While the Consultant has exercised all reasonable skill and care in the preparation of information in this report, neither the Consultant nor MAF Policy accept any liability in contract, tort or otherwise for any loss, damage, injury, or expense, whether direct, indirect or consequential, arising out of the provision of information in this report. A field study has been undertaken to determine the ability of riparian buffer strips to trap Campylobacter and E. coli. Sloping grass plots (length 5 or 1 m, width 2 m) were irrigated with clean water to generate steady surface runoff. 20 litres of farm dairy effluent, artificially contaminated with C. jejuni, was then applied to the surface, at the top of the plots, over 2-3 minutes. Irrigation with clean water was continued for 40-60 minutes. The outflow at the lower end of the plots was sampled for microbial analysis. Irrigation then ceased for 5-12 days. The plots were then irrigated again with clean water and sampled to investigate whether microbes remaining after the first trial were remobilised. It is important to note that surface runoff generated during these experiments was comparable with that during heavy and prolonged rainfall. The experiments, therefore, represent a 'worse-case' (minimum trapping) scenario. The results indicate that: 1. When liquid farm dairy wastes were injected over 2-3 minutes onto saturated pasture soils, irrigated to generate surface runoff, there was a rapid 'first flush' of high Campylobacter and E. coli concentrations downslope for at least 5 m.