A Randomised Field Trial Methodology for Cost-Effectiveness Diagnostics of Water Treatment Systems in Tanzania

{ "background": "Evaluating the cost-effectiveness of water treatment systems in sub-Saharan Africa is critical for sustainable development, yet robust field methodologies for engineering diagnostics are lacking. Current assessments often rely on modelled data or controlled pilot studies, which fail to capture real-world operational variability and long-term economic performance.", "purpose and objectives": "This article presents a novel methodological framework for conducting randomised field trials (RFTs) to diagnose the cost-effectiveness of decentralised water treatment systems. The primary objective is to provide a replicable protocol for generating comparative, empirical data on both technical performance and lifecycle costs under actual operating conditions.", "methodology": "The proposed RFT methodology involves the random assignment of functionally similar community water points to different treatment technology cohorts. Data collection is longitudinal, capturing key parameters: water quality (e.g., faecal coliform log-reduction), volumetric output, energy consumption, maintenance frequency, and detailed capital and operational expenditures. Cost-effectiveness is analysed using a generalised linear model: ij = \β0 + \β1Tij + \β2Xij + \εij, where ij is the cost per cubic metre of compliant water for system i in cluster j, Tij denotes the technology assignment, and Xij a vector of covariates. Inference is based on cluster-robust standard errors.", "findings": "As a methodology article, this paper presents no empirical trial results. Instead, the findings detail the developed framework, including a validated sample size calculation indicating that a minimum of 30 clusters per technology arm is required to detect a 20% difference in unit cost with 80% power. The protocol explicitly addresses common field challenges such as attrition and confounding environmental factors.", "conclusion": "The structured RFT framework provides a rigorous, transparent, and standardised approach for the field-based diagnostic evaluation of water treatment technologies. It moves beyond technical efficiency to integrate