Sustainable pressure-driven membrane facility controlled by a smartphone application for groundwater desalination in the dry zone of Sri Lanka

Abstract

Presently over three million people, mostly living in the dry zone of Sri Lanka, experiencing acute water stress due to excess salinity which results in palatability problems. In many parts of the world, reverse osmosis (RO) and nanofiltration (NF) technologies are successfully used for water desalination. However, in Sri Lanka, these methods show limited success due to inappropriate or over technologies adapted. The selection of the membranes depends on the source water salinity variations. We judiciously selected a groundwater source that requires desalination. The geochemical evolution of the groundwater source was determined by the 1D inverse modelling method. The source water salinity is ascribed to the incongruent dissolution of silicate minerals into montmorillonite followed by an ion-exchange process. The transition of geochemical facies from (non-dominant cation) NDC-HCO₃^- (discharge zone) to Ca-HCO₃ (recharge zone) water type is observed along subsurface flow paths. After regulating the water turbidity (below 0.1 NTU), appropriate RO and NF membrane configuration was chosen for desalination. No external chemicals were added to maintain electrolytes balance in the treated water. The wastewater generated by the membrane treatment is blended appropriately for other community water needs. The chemical quality of treated water was optimized by a homogeneous diffusion-solution modelling method. The laboratory water plant is automated enabling remote operation and user-end maintenance via a mobile phone application. This step is vital to minimize community participation in plant maintenance. By our method, over 95% of the feed water was utilized for community use in compliance with the UNESCO Water, Sanitation and Hygiene (WASH) program.

Keywords

• unsdg 6
• inverse modelling
• reverse osmosis
• nanofiltration
• mobile app