Effect of Sewage-Contaminated Irrigation Water on the Bacterial Quality of Ready-To-Eat Fresh Vegetables; Watercress (Eruca sativa) and Lettuce (Lactuca sativa)

In Egypt, some people illegally dump untreated sewage into irrigation canals. Farmers use these polluted canals and the water from the Bahr El-Baqar drain to irrigate farmlands. The bacterial content of irrigation water, agricultural soil, and ready-to-eat vegetables gathered from farmlands was evaluated. Watercress (Eruca sativa) and lettuce (Lactuca sativa) were selected since they are major ready-to-eat vegetables in most Egyptian households and restaurants. A total of 80 samples (20 irrigation water, 20 farmland soil, 20 watercress, and 20 lettuce) were collected from four farmlands irrigated with partially treated sewage from the Bahr El-Baqar drain. Another 80 similar samples were collected from farmlands irrigated with canals polluted with illegally dumped untreated sewage. The efficacy of four different watercress and lettuce washing methods was also assessed. E. coli, E. coli O157:H7, and Salmonella sp. showed significant survival on watercress and lettuce for over 15 days. Regardless of the tested washing strategies, a vinegar-based washing strategy can reduce bacterial levels. In conclusion, using irrigation water polluted with untreated or partially treated sewage contaminated the ready-to-eat fresh vegetables with pathogenic bacteria, which is considered a high risk to human health.