Development and characterisation of a photovoltaic hybrid membrane system

In isolated communities where potable water sources as well as energy grids are limited or nonexistent, treating brackish groundwater aquifers with small-scale desalination systems is an interesting and sometimes viable alternative to existing water infrastructures. With regards to the performance of intermittently operated desalination systems only very limited experience exists, both with regards to efficiency as well as water quality. Therefore, these experiments were conducted with a constant power source as a step towards defining a safe operating window, and provide a basis for interpreting future data obtained with a renewable energy source. Field trials were performed on a brackish (5300 mg/L TDS; 8290 μS/cm) bore in Central Australia with a photovoltaic-powered membrane filtration (PV-membrane) system. Four nanofiltration and reverse osmosis membranes (BW30, ESPA4, NF90, TFC-S) and a number of operation parameter combinations (transmembrane pressure, feed flow, membrane choice) were investigated to find the best operating conditions for maximum drinking water production and minimum specific energy consumption (SEC). The ESPA4 membrane performed best for this brackish source, producing 250 L/h of good drinking water (257mg/L TDS; 400 μS/cm) at an SEC of 1.2 kWh/m. The issue of brine disposal or reuse is also discussed and the article compares the salinity of the produced brine with livestock water. Since the feed water is disinfected physically, the brine is free from bacteria and most viruses and hence can be seen more as a reusable product stream than a waste stream with a disposal problem.