SR9070 - Removal Efficiency of Representative Bacterial and Protozoan Pathogens from Cattle and Pig Farm Wastewater Using Wetland Technologies

Lead researchers

Drs. Robin Slawson and Barry G. Warner, University of Wateroo

Objectives

To characterize the spatial distribution and year round temporal variability of pathogenic enteric bacteria (E. coli, Salmonella, Campylobacter) and protozoa (Crytosporidium) on soil particles, in the soil water and on the plant roots (rhizophere).

Expected benefits

1. The data will aid in our understanding of the removal efficiency of pathogens by wetland technologies that will assist in the refinement and parameterization of improved wetland designs in the future.
2. Will have considerable economic benefit by contributing to effective low-cost wastewater treatment alternatives to current BMP's and for watershed and source water protection for farmers and rural residents.

Results

A buffer strip treatment wetland system was assessed for its ability to remove microbial contaminants from agricultural effluent. The wetland system, consisting of three wetland cells laid out in sequence, was situated between the cattle barn runoff point and a small tributary within the Grand River watershed.

Abundance data were collected for pathogen indicator organisms over two field seasons. Attempts to monitor pathogens directly using traditional methodologies were less successful due to insufficient water volumes. When conditions favoured attempts to monitor the specific pathogens, Cryptosporidium spp., Campylobacter spp., and Salmonella, results were negative.

Indicator E. coli were monitored for several months each season and 100% removal of the organisms occurred within the second of three consecutive cells. Throughout the monitoring period, a range of 2 to 4 log removal of the monitored E. coli occurred on average from the influent to the strip and the stream edge. Data suggested slightly longer viability of the E. coli during the warmer months.

Similar results were obtained using faecal coliforms as the monitored indicator group. A four log removal of influent concentrations were observed throughout the buffer strip with almost 100% removal occurring by the midpoint of the second cell. In addition, nitrate levels were similarly reduced throughout the wetland buffer strip system.

Detection of the specific pathogen, E. coli O157:H7 was attempted using culture-based procedures, but results were negative. Advanced methodologies using quantitative real-time polymerase chain reaction procedures were initiated, but environmental samples are complex and further development was beyond the scope of this project.

This study supported the fact that a buffer strip treatment design is an effective option in the remediation of waste effluent from barnyard runoff waters. Both surface and shallow subsurface samples demonstrated consistent and high removal efficiencies (>95%), with most of the removal taking place within the first wetland cell.

The following specific recommendations have been generated from this study:

• optimization of buffer strip design to increase robustness during very dry periods
• development and improvement of non-culture based procedures for detection and quantification of specific pathogens for environmental samples
• perform further testing of a similar nature with different wetland designs;
• enhance the understanding of specific factors which may influence pathogen removal beyond physical processes in order to further optimize design parameters

Related information

• Other projects funded through the New Directions Research Program in 2001