Risks Associated with Urban Wastewater Irrigation and Production of Traditional African Vegetable (TAVs) Seeds in Nairobi, Kenya

Abstract

Globally farmers use wastewater to irrigate crops because it also supplies plant nutrients and ensures all year round food availability. A study was carried out in Nairobi with farmers who used wastewater to produce both food and fodder along the Ngong/Motoine River to obtain an understanding of the benefits and risks associated with wastewater farming and to identify mitigation strategies. Farmers cultivated plots below 0.5 acres where they grew vegetables for home consumption, sale for employment. Analysis of the wastewater samples showed that heavy metal contents were within acceptable limits. However, investigation done on plant samples taken from selected crops showed that there was bioaccumulation of cadmium, chromium and lead to levels that were several times higher than the recommended critical limits. Determination of biological contamination samples from these farms and from the wet markets showed that produce from the markets had higher loads of faecal colifoms and parasitic eggs than vegetables irrigated with untreated water. One strategy for mitigating health risks associated with consumption of the contaminated vegetables was to introduce an alternative farming activity to farmers which in this case was to introduce production of Traditional African Vegetables seeds. Eight farmers have for two seasons been able to produce 30 kg of assorted seeds valued at KShs 30000 or USD 400. This has increased both income and assets for farming households and availability of quality seed for rural and urban farmers.