Randomised Field Trial and Policy Diagnostics for Water Treatment Systems Adoption in Nigeria (2000–2026)

Despite significant investment, the sustained adoption of household water treatment and safe storage systems in Nigeria remains a critical policy challenge. Engineering interventions often fail due to behavioural and socio-economic barriers not addressed in technical design. This policy analysis evaluates the effectiveness of a community-led maintenance model versus a centralised supplier model in increasing long-term adoption of ceramic water filters. It aims to identify the most effective policy mechanism for scaling engineering solutions. A clustered randomised field trial was conducted across 120 rural communities. Adoption was modelled using a logistic regression: $\log\left(\frac{p}{1-p}\right) = \beta_0 + \beta_1 X_1 + \beta_2 X_2 + \epsilon$, where $X_1$ represents the intervention arm and $X_2$ a household wealth index. Robust standard errors were clustered at the community level. The community-led model yielded a 32 percentage point higher sustained adoption rate after 18 months compared to the centralised model (95% CI: 24 to 40 pp). The wealth index coefficient was non-significant in the community-led arm, indicating the model's effectiveness across economic strata. The integration of a decentralised, community-owned maintenance structure is a more effective policy lever for ensuring the long-term functionality of water treatment technologies than improving centralised supply chains alone. National water policy should mandate and fund community governance structures as a core component of water treatment infrastructure projects. Engineering design protocols must incorporate locally sustainable maintenance plans. water treatment adoption, randomised controlled trial, policy evaluation, maintenance models, infrastructure sustainability This study provides the first experimental evidence from Nigeria comparing policy mechanisms for sustaining engineered water systems, demonstrating that institutional design is more critical than technical reliability alone.