RE-USE OF GREYWATER FOR IRRIGATION OF VEGETABLE CROPS: PRODUCTION AND HEALTH RISKS

摘要

The safe re-use of wastewater for agriculture is a desired goal in many arid zone countries. The potential of greywater as alternative irrigation source for vegetable crops was investigated. Tomato, pea and cantaloupe plants were drip irrigated with both fresh Nile water and greywater to access the impact on yield production and associated environmental and health risks. The biological properties of the two different sources of water clearly indicated that greywater was extremely higher in bacterial content compared with fresh Nile water. Pea plants showed significantly higher yield irrigated with fresh Nile water, however, tomato and cantaloupe plants gave significantly higher yield irrigated with greywater. Generally, the coliform populations in untreated greywater irrigated plants were higher than those irrigated with Nile water in all tested vegetables. The percentages of increasing in total coliform in untreated-irrigated greywater vegetables were 27.95, 34.55 and 41.4 for pea, tomato and cantaloupe (averaged over outer and inner fruit tissues), respectively. Unexpectedly, central part of fruits for pea and tomato had highest coliform counts when compared to the outer surface using both Nile and untreated greywater. Overall, irrigation with greywater increased soil bacterial content by 15 while fresh Nile water increased it by 13 at the end of the experiment. In addition, greywater elevated the content of soil total coliform by 52 where fresh Nile water increased it by 30. The results of this study indicated that untreated greywater should not consider as an alternative irrigation source for edible crops such as vegetables. In current investigation, the beneficial effects in tomato through giving significantly higher yield with greywater became worthless after the enormous fecal contamination that was detected in fruits. Several considerations must be adopted to minimize the health and environmental risks associated with greywater reuse in irrigation of vegetable crops.