Managing and Mitigating Microbial Contamination of Natural Waters

Good quality water is highly valued by New Zealanders and it forms an intrinsic part of New Zealand’s clean, green image. However, the quality of New Zealand’s natural waters is being compromised as land use and urbanisation intensifies.

Lester Sinton, Senior Scientist, leads ESR’s water microbiology research team in Christchurch. The team is at the forefront of research that underpins the issue of contamination of natural surface- and ground- waters in New Zealand by faecal microbes, from sources such as septic tank systems, effluent discharges and grazed farmland.

This research complements that undertaken by the groundwater research team, and includes the investigation of transport and attenuation processes of bacterial and viral indicators and pathogens in surface- and ground- waters, and the development of molecular methods for quantifying gastrointestinal viruses.

This work is characteristic of the way research is carried out at ESR, in that scientifically robust data are generated to provide the knowledge and solutions to issues that consequently benefit New Zealand.

The research carried out by ESR's water microbiology research team is of key significance to regional councils, the dairy industry, the Ministry of Health and the Ministry for the Environment. As a key outcome of this scientific expertise, some of the findings from this research have been included in the most recent update of the Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas.

Current research projects

Survival characteristics and sources of indicator and pathogen microbes in sunlight-exposed sea water and river water: Initially, the aim of this research was to determine whether the United States Environmental Protection Agency (EPA) recommendations on the use of enterococci bacteria as indicators on marine bathing water quality could be applied to New Zealand's marine bathing waters. As it turned out, the research showed that enterococci are the wrong indicators to use in water polluted by waste stabilisation ponds (WSPs), which are commonly used to treat effluent in New Zealand. The scope of this work has since been broadened into comparisons of the survival of indicator and pathogenic microbes in surface waters.

Microbial contamination from animal sources: The aim of this research is to develop 'animal faecal microbe reservoir' models for the key indicator and pathogenic enteric microbes from grazing animals and waterfowl in New Zealand. The scientists are investigating the seasonal survival times of these microbes in cow pats. These models will assist water managers in their estimations of microbial inputs to natural waters from animals such as cows, sheep and ducks, and the likely effects of changes in land use on microbial water quality. This will help water managers to manage and mitigate animal pollution of natural waters in New Zealand.

Microbial contamination and transport in groundwater systems: The aim of this research is to obtain reliable data on the movement of enteric microbes into and through groundwater systems, and to utilise and validate models to characterise their transport and attenuation.  The team is conducting two main projects: (1) Characterising the relative transport and attenuation of different enteric bacterial and viruses in alluvial gravels, using field sites and a 5 m vertical column at Lincoln University, in collaboration with Lincoln Ventures; (2) Determining rates of transport and attenuation of bacteria and viruses in pumice and sand aquifers in the Central North Island, using field sites and laboratory columns.