Development of a mobile groundwater desalination system for communities in rural India

The consumption of saline groundwater has contributed to a growing incidence of renal diseases, particularly in coastal communities of India. Although reverse osmosis (RO) is routinely used to remove salt from groundwater, conventional RO systems (i.e. centralized systems using spiral wound RO elements) have limited utility in these communities due to high capital and maintenances costs, and lack of infrastructure to distribute the water. Consequently, there is a need to develop an appropriate solution for groundwater treatment based on small-scale, mobile and community-led systems. In this work, we designed a mobile desalination system to provide a simple platform for water treatment and delivery of goods to rural communities. The system employs tubular RO membranes packed in a single, low-profile vessel which fits below the cargo space. The low-profile enables minimal intrusion on the space available for the transportation of goods. Pressure is delivered by a belt driven clutch pump, powered by the engine. Water is treated locally by connecting the intake to the village well while the vehicle idles. A combined numerical and experimental approach was used to optimise the module/system design, resulting in ∼20% permeate flux enhancement. Experimental results revealed that the system can produce 16 L per square meter of membrane area per hour (LMH) at a salinity level of 80 ppm from a ∼2000 ppm groundwater when it is feed at 1 m³/h at 8 bars. This indicates that a vehicle equipped with 12 m² of tubular RO membranes can deliver 1 m³ of drinkable water by using ∼0.9 L of diesel. Assuming eight such systems could be implemented in a community to fulfil the water demands for a village with 2000 residents, a social business study revealed that a payback time of 2.5 years is achievable, even if the sale price of the water is relatively low, USD 0.18 (Rs 12, which is half of the lowest market price) per 20 L, including providing a goods transportation service at price of USD 5.25 (Rs 350) per 100 km.