Treated Wastewater Reuse under a Changing Climate: An ethnographic health risk assessment in the Chinchaya community in La Paz, Bolivia

Abstract

Treated wastewater reuse is increasingly promoted as a climate adaptation strategy for water–scarce agricultural settings, yet its health risks are often assessed through approaches that foreground pathogens, contaminants, and modelled exposure pathways while overlooking everyday social practices related to water. This thesis explores how local practices, understandings, and systemic drivers of water use shape potential health risks from a pilot treated wastewater reuse project in Chinchaya, a peri–urban agricultural community in La Paz, Bolivia. Drawing on social practice theory, the hydrosocial cycle, structural violence, and One Health, the study conceptualises health risk as a social and ecological phenomenon produced through situated practice rather than as a fixed property of treated water. Fieldwork was conducted between January and March 2026 and included a participatory risk–mapping workshop, field observations, and walking and semi–structured interviews with community members and project experts. Thematic analysis identified five main findings: cumulative and interchangeable use of multiple water sources; place–based water quality hierarchies; predominantly human–made drivers of water insecurity; contested community water governance; and overlapping water risks involving runoff, contamination, animal contact, and landslides. The findings show that treated wastewater will enter an already plural, fragile, and contested water landscape. Its health implications will therefore depend not only on its laboratory profile, but on how it is incorporated into existing practices, infrastructures, and governance arrangements. The thesis argues that safe reuse of treated wastewater requires health risk assessment and project implementation to engage with local practice landscapes, hydrosocial knowledge, structural inequalities, and human–animal–environment interactions.

Popular Abstract

Reusing Treated Wastewater for Agriculture: Why Local Water Practices Matter for Health Risk

Introduction
Treated wastewater reuse is often proposed as a climate adaptation strategy for water–scarce farming regions. This thesis shows that its health risks depend not only on the quality of the water itself, but on how communities already use, judge, and share water.

Main text
The health implications of treated wastewater reuse projects are usually assessed through laboratory measurements: what pathogens or contaminants are present, and at what concentration. This thesis asks a different question: how do people in a community actually use water, and what does that mean for the safety of a new water source introduced into an existing water landscape?
The study is based on fieldwork carried out between January and March 2026 in Chinchaya, a peri–urban farming community outside La Paz, Bolivia, where a wastewater treatment plant was recently built to supply treated wastewater for irrigation, especially during the summer dry season, which is becoming drier and drier due to climate change. Data were collected through a participatory risk–mapping workshop with community members, walking and semi–structured interviews with residents, and interviews with project staff.
Four findings stand out. First, households in Chinchaya do not use a single water source. They draw on tap water, streams, wells, rainwater, irrigation hydrants and ditches, often switching between them or mixing them, depending on the season or on practical circumstances. Second, residents apply a consistent, place–based logic to judge water quality – deep water is generally considered of higher quality than superficial water running across the community – based on smell, appearance, and years of experience, rather than on laboratory thinking. Third, most of the water insecurity reported in the community during the rainy season depends on human factors: maintenance failures, unequal access to infrastructure, and disputes over how the local irrigation system is governed. Fourth, water–related hazards in the community are multiple (water contamination, landslides, extreme weather events, extensive water runoff across cultivated plots) and significantly overlap and interact with each other, making single hazard assessments unfit to adequately describe the risk landscape in the area.
These findings matter for the wastewater reuse project specifically, and for similar projects elsewhere. If treated water enters a system where sources are already combined and judged by where they seem to come from, its actual laboratory profile may not be the main factor determining how the water will be used or trusted. In addition, since some water sources are shared between people, crops, and animals, and surface runoff moves across cultivated plots, contamination risks are unlikely to stay confined to a single, isolated pathway – a limitation shared by standard risk assessment methods, which typically model one pathogen and one exposure route at a time.
The thesis argues that health risk assessments and implementation plans for treated wastewater reuse should therefore account for existing water practices, local water–quality reasoning, and the social and infrastructural conditions of a community, rather than treating the safety of the water as a property of its laboratory profile alone. It also argues that these data are more reliably collected by establishing partnerships with local communities and inviting them to shape projects based on their expert knowledge of their own contexts.

• author: Zanni, Francesca
• supervisor: Mo Hamza
• organization: Division of Risk Management and Societal Safety
• course: VBRM15 20261
• year: 2026
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Treated wastewater, water, water security, water insecurity, WASH, water governance, agriculture, health, risk assessment, ethnography, climate change, Bolivia, South America
• language: English
• id: 9250500
• date added to LUP: 2026-09-11 15:06:45
• date last changed: 2026-09-11 15:06:45