Enteric bacterial contamination and survival on produce during irrigation with dairy wastewater in the field

The goals of this study were to quantify enteric bacterial contamination and survival on several different types of produce during irrigation with wastewater from a dairy operation. Dairy wastewater was used to irrigate three different types of vegetable crops: lettuce, carrot, and bell pepper. This study was conducted over two consecutive growing seasons. Irrigation water and vegetable samples were examined for Escherichia coli and Clostridium perfringens. In the dairy wastewater, E. coli and C. perfringens concentrations averaged 8.2× 10⁷ MPN/100 mL and 5.0× 10⁴ CFU per 100 mL, respectively. Analysis of variance test results indicated that E. coli and C. perfringens concentrations detected on the three crops after irrigation were statistically different (p < 0.0001). The greatest contamination occurred on the carrots followed by lettuce and bell peppers. E. coli and C. perfringens were recovered from the carrots, bell peppers, and soil 49 days after wastewater irrigation of the plots had ceased. Moisture content of the soil was statistically significantly related to survival of the organisms in the soil.