Point of Use Semi-Batch Reverse Osmosis Desalination Prototype Experimental Validation

Abstract

Water scarcity is undoubtedly a growing problem worldwide. Desalination provides a potential solution to water scarcity by providing water from typically unusable sources (saline brackish aquifers, seawater, or saline surface water), especially to regions that previously did not have reliable access to treated piped water. A range of desalination systems exists, from large seawater distillation plants in Kuwait to home-scale point-of-use (POU) reverse osmosis (RO) purifiers in India. However, current home-use systems produce significant amounts of wastewater, achieve a recovery of 20-30% of the input feed as drinking water, and consume significant energy. Through previous testing and analysis of a POU RO system, it was identified that recirculating brine within a semi-batch configuration with a brine flushing mechanism can potentially achieve 75% or higher recovery ratios. A prototype made from off-the-shelf parts was engineered by a group of graduate students associated with the Global Engineering and Research (GEAR) lab. In the preliminary testing that they performed the prototype demonstrated recovery rates of 75% without affecting production rate and quality.

This work aims to design and integrate engineering a data acquisition board with voltage and current sensors, pressure sensors, and flow meters to facilitate autonomous operation; where this is characterized by automated switches between batch production and flush system states to dispose of an empirically derived flush volume based on a derived threshold system operating pressure. This project experimentally defines the conductivity saturation limits for a semi-batch POU RO system prototype and observes the change in recovery ratio as the prototype continuously operates to perform a long-term, lifetime test of an RO membrane.