Microbial Contamination of Vegetables Irrigated with Sewage Effluent by the Drip Method

Abstract

The effect of the drip irrigation method on microbial contamination of vegetables irrigated with wastewater was evaluated. The density of microbial contamination on surfaces of cucumbers and eggplants irrigated with sewage effluent was determined, using a controlled washing procedure. The fecal coliform count on vegetables irrigated with wastewater was 38-fold higher than on vegetables irrigated with fresh water. However, agrotechnical manipulations of the drip method, such as sub-irrigation or covering the soil and the drip lines with plastic sheets, reduced bacterial contamination considerably. Similarly, the bacterial contamination on vegetables which were irrigated with sewage effluent during the first stage of growth (up to flowering) and subsequently with fresh water was not different from the contamination on vegetables which were irrigated with fresh water. The viral contamination on 27 vegetable samples which were collected from sewage irrigated experimental plots was below the level of detection. It is proposed that the drip method may be considered for wastewater irrigation of crops in accordance with generally accepted public health criteria.