This case study aimed to determine if farmers, in low income countries, can safely reuse treated wastewater from an existing waste stabilization pond (WSP) system for irrigation, or are additional control measures or treatment processes required to reduce exposure to viral pathogens and meet a specified health target?
The study took place in a town, located in a culturally diverse region of the Caranavi province of Bolivia near the Alto Beni River, an important inland fishery system in the Amazon River basin. The local economy is driven by citrus fruit production for domestic sale and cacao beans for factories that manufacture chocolate. Many farmers chew coca leaves while working, resulting in frequent hand-to-mouth contact. Reclaimed wastewater can provide a local source of irrigation water that contains valuable nutrients and may be less carbon intensive than other sources. Like many areas of the world, most population growth will occur in small cities, such as the one studied here, that are closely linked to agricultural zones.
Figure 1. Community-operated waste stabilization pond (WSP) system with (a) a facultative pond and (b-c) two maturation ponds in series (left); case study site location (right; photo by M.E. Verbyla).
The wastewater treatment system serves 780 people and consists of flush toilets, a gravity-driven conveyance network, and three WSP in series. While it provided high removal of faecal coliforms, limited virus removal was measured. Treated effluent is discharged to a nearby surface water, but some farmers would like to use the effluent for irrigation. This sanitation system is managed and operated by a volunteer community water committee.
Minor additional control measures are needed to reduce the risk of virus exposure during farming and meet the specified health target for this study. It is better to use at least two of these measures in combination to create “multiple barriers” for pathogen control. If one barrier fails, others will still provide some protection.