Fertiliser Drawn Forward Osmosis Desalination: Achieving Water Quality Requirements for Direct Fertigation by Integrating Nanofiltration

摘要

The prevailing desalination technologies are energy intensive and therefore uneconomical for large-scale applications such as irrigation. Forward osmosis (FO) has been recently recognised as an emerging technology for low energy desalination. In particular, FO process offers a promising scope for applications, when a draw solute is used that adds value to the extracted water. In the fertiliser drawn FO (FDFO) desalination process, a concentrated fertiliser is used as draw solution (DS) in which the final diluted fertiliser DS can be directly used for fertigation. However, because of the process limitations posed to the recovery rate by the osmotic equilibrium between the feed solution (FS) and the DS, the nutrient concentration in the final FDFO product water usually exceeds acceptable nutrient concentrations (NPK or nitrogen, phosphorous, potassium) requiring additional fresh water for dilution before fertigation. Such a situation is not preferable given the very purpose of desalination as a means to serve as alternate source of freshwater.