A Bayesian Hierarchical Model for Evaluating Water Treatment System Adoption in Tanzania, 2000–2026

"background": "Universal access to safe drinking water remains a critical engineering challenge in sub-Saharan Africa. Understanding the dynamics and drivers of water treatment technology adoption is essential for infrastructure planning and investment, yet robust predictive models are lacking. ", "purpose and objectives": "This study aimed to develop and validate a novel Bayesian hierarchical model to evaluate the adoption rates of different water treatment systems, and to project future adoption trajectories under varying policy scenarios. ", "methodology": "We developed a Bayesian hierarchical model where the log-odds of adoption ij = ({ij1-p{ij}) for technology i in region j is modelled as ij = + Xj + ui + vj, with ui N (0, ²) and vj N (0, ᵥ²). The model was fitted using Markov Chain Monte Carlo methods to national survey and infrastructure audit data. ", "findings": "The model identified a strong positive association between household education levels and the adoption of point-of-use filters, with a posterior mean odds ratio of 1. 85 (95% credible interval: 1. 62 to 2. 11). Projections indicate community-scale chlorination systems will remain the most prevalent technology, but adoption growth is highest for household-level solutions. ", "conclusion": "The Bayesian hierarchical framework provides a robust tool for quantifying adoption heterogeneity and uncertainty, revealing that socio-economic factors are more influential than geographical ones in technology uptake. ", "recommendations": "Infrastructure policy should prioritise targeted educational programmes alongside technology deployment. Future engineering research should integrate similar probabilistic models into lifecycle cost-benefit analyses for water systems. ", "key words": "Bayesian statistics, hierarchical model, water treatment, technology adoption, infrastructure planning, probabilistic projection", "contribution statement": "This paper presents a novel probabilistic modelling framework that explicitly quantifies uncertainty in technology adoption forecasts, providing a superior