Nanofiltration is assessed as an integrated process to fertiliser drawn forward osmosis (FDFO) desalination, to reduce the nutrient concentrations in the final product water. This would allow direct use of the product water for fertigation – the application of fertilisers via irrigation – without further dilution.
The concept of fertiliser drawn forward osmosis (FDFO) desalination lies in the premise that fertilisers that serve as draw solutions add value to the FDFO product water for fertigation, i.e. the application of fertilisers via irrigation.
However, because FDFO desalination is concentration based, the process cannot continue beyond the concentration equilibrium – one of the major limitations of the forward osmosis process.
This results in final FDFO product water that, unless substantially diluted with fresh water, exceeds the acceptable nutrient concentrations for direct fertigation.
In this study, researchers in Australia, Korea and the US assess nanofiltration (NF) as an integrated process to FDFO desalination – either as a pre-treatment or post-treatment – to reduce the nutrient concentrations in the final product water. This would allow direct use of the product water for fertigation without further dilution.
Nanofiltration as pre-treatment or post-treatment was found to be effective in reducing the nutrient concentrations using brackish groundwater (BGW) sources with relatively low total dissolved solid (TDS).
However, when using BGW sources with higher TDS, the product water still required further dilution or post-treatment before fertigation.
NF as post-treatment was found to be more advantageous, both in terms of reduced nutrient concentrations in the final product water and energy consumption.
