Field evaluation of a hand-powered reverse osmosis system for sustainable water purification in off-grid rural India

• HP-POU-RO at ultra-low pressure to produce fresh water. • Field test using off-grid water (India) during 6 months of continuous operation. • An 88.2–93.94 % TDS rejection. • Community Perception Survey on Water Quality and System Usability. This study shows the development and implementation of a novel Hand-Powered Point-Of-Use Reverse Osmosis (HP-POU-RO) purification unit designed to operate under extremely low-pressure conditions (≤0.2 MPa) in off-grid rural environments. The system was tested for six months in Namkhana (West Bengal), using water from a well, and Udaipur (Rajasthan), using water from a cement water reservoir tank. The raw water exhibited Total Dissolved Solids (TDS) levels ranging from 680 to 1080 mg L⁻¹, representative of moderately brackish conditions. The HP-POU-RO unit integrates a 3-inch RO module identified as HA002 and HA003, each made up of a new cellulose nanofiber composite membrane. These RO modules were coupled to a manual piston-driven mechanism that converts human effort into hydraulic pressure to drive the reverse osmosis process. Results showed TDS rejection rates of 88.2 % for HA002 and 93.94 % for HA003, with specific energy consumption (SEC) values ranging from 0.18 to 0.20 kWh m⁻³. In comparison, a commercial polyamide (PA) RO module (HA004) exhibited a slightly higher TDS rejection rate of 95.25 % but required significantly more SEC (0.38–0.40 kWh m⁻³). These findings confirm the high energy efficiency and operational stability of the HA002 and HA003 RO in prolongated manual operation. A community perception survey revealed strong social acceptance, reporting satisfaction with water taste, clarity, and perceived health benefits. Findings suggest that the HP-POU-RO unit is a sustainable technological solution for providing safe drinking water from off-grid systems, with potential for wider deployment in remote or infrastructure-limited regions.