Socio-Technical and Economic Analysis of Small Scale Reverse Osmosis Desalination in Coastal Bangladesh: Insights from Field Audits, Water Quality Assessment, and Behavioral Modeling

Coastal Bangladesh faces severe drinking water scarcity due to salinity intrusion. To address this challenge, the study assesses the socio-technical and economic factors shaping the performance of small-scale reverse osmosis (RO) desalination plants through field audits, household surveys, stakeholder interviews, and water quality analysis. Community acceptance was evaluated using the Theory of Planned Behavior (TPB). Feedwater was highly contaminated, with average TDS 3732.63 mg/L, hardness 636.36 mg/L, iron (Fe) 3.23 mg/L, and turbidity 14.63 NTU. Despite this, RO systems demonstrated strong performance, achieving removal efficiencies of 95.15% for salts, 95.95% for hardness, and 91.67% for alkalinity, with an average recovery rate of 37.25% (range: 20–60%). Treated water met WHO and Bangladesh standards, with mean concentrations of TDS (195.54 mg/L), Fe (0.21 mg/L), arsenic (0.0085 mg/L), and turbidity (1.09 NTU). However, inadequate operator training and a lack of maintenance threaten sustainability. Energy consumption increased by 0.1 kWh/m3 per 1000 mg/L rise in salinity, while financial constraints hinder membrane replacement. TPB analysis revealed positive attitudes and perceived behavioral control as key adoption drivers. Untreated brine discharge (mean TDS 12,900 mg/L) posed significant environmental risks. This study provides micro-level insights to inform policy and strengthen the sustainability of decentralized RO systems in climate-vulnerable coastal regions.