Background and context

Cochabamba, Bolivia, is facing water scarcity, growing demand for irrigation, and poor sanitation management, making safe wastewater management a critical need. Inefficient treatment practices have led to environmental degradation, while low soil productivity and low incomes of rural farmers highlight the need for sustainable agricultural solutions. To address these challenges, decentralized wastewater treatment and reuse initiatives have been implemented, improving water efficiency and agricultural resilience.

Approach

The project employs upflow anaerobic sludge mantle reactors (UASBs) and anaerobic baffle reactors (ABRs) for wastewater treatment, complemented by horizontal and vertical gravel biofilters to improve water quality. The wastewater treated is reused for agricultural irrigation, providing a nutrient-rich water source and reducing reliance on scarce groundwater. Among the actors involved are the Aguatuya Foundation, the municipal governments of Cliza, Tolata and Punata, the Swedish International Development Cooperation Agency (SIDA) and rural farmers' associations. 

The implementation involved the construction of decentralized wastewater treatment plants (WWTPs) and the integration of anaerobic and biofiltration technologies. A flexible management model was established, assigning roles to an infrastructure owner (municipality, community or utility company), a service provider and an operator to ensure long-term sustainability. In addition, municipal staff and local communities were trained in the operation, maintenance and monitoring of the plant. A cost-recovery model was developed that incorporated municipal funding and tariff structures to support sustainable management, and wastewater reuse was integrated into agriculture with clear guidelines on crop selection and irrigation methods.

Outcomes and impacts

The project has enabled the annual reuse of 296,022 cubic meters of treated wastewater, irrigating 120 hectares of agricultural land. Environmental benefits include a 97% reduction in organic matter and suspended solids discharged into water bodies, significantly improving local water quality. In addition, the initiative has improved urban water sustainability, boosted agricultural productivity through the reuse of nutrient-rich wastewater, and reduced reliance on groundwater sources, contributing to long-term resilience in the region.

Lessons learned

The initiative demonstrated that decentralized wastewater treatment models can be successfully implemented, taking advantage of low-cost natural treatment processes. The close collaboration between municipalities and international organizations was a key factor for its viability. However, challenges remain, such as ensuring the long-term financial sustainability of treatment plants, developing a regulatory framework for wastewater reuse, and encouraging continued community engagement along with capacity building. This model, with high potential for replication in other water-scarce regions, offers a scalable solution for sustainable wastewater management. However, its long-term success and widespread adoption depend on strong political and financial backing.