DESIGN CONSIDERATIONS AND CONSTRAINTS IN APPLYING ON- FARM WASTEWATER TREATMENT FOR URBAN AGRICULTURE

In Accra, Ghana, one of ten SWITCH focus cities, the LA through the working group on water use for urban agriculture, initiated participatory action research activities on technological innovations to minimise risks associated with urban water reuse for agriculture within the context of integrated urban water management. The purpose was to demonstrate the potential of on-farm wastewater treatment to minimize health risks associated with urban water reuse for agriculture. The Demo focuses on further development of existing farmers ’ practice of on-farm water storage ponds, for improved irrigation water quality and volume. This study component of the demo addresses the problem in an integrated manner. It focused on farmers ’ constraints to propose sustainable and reproducible technical options. Research was held in Roman Ridge farming area, Accra, Ghana. Two different settings were investigated: 1) greywater derived from gutters in a ponds-trenches system; 2) individual ponds filled periodically with water pumped from a stream. Analyses show a natural faecal coliform removal of about 2 log units from the wastewater source to the last pond in the case of ponds-trenches system. As for individual ponds, a removal of 1-1.5 log units is observed in two days. Nutrients levels were very low, meaning that this water can’t be seen as a source of fertilizer