Reverse osmosis (RO) is the process of purifying water to the highest standard, using pressure to filter out any contaminants. Up to 70% of water supplied to RO plants is rejected. For example, 10L of mains water (water supplied by the public water system) produces 3L of RO water, with the remainder going down the drain.
The quality of rejected water is typically four times harder than tap water; there is an opportunity to capture, store and reuse this water to flush toilets. This project will be undertaken at the Lake Haven Community Health Centre located within the Central Coast Local Health District (CCLHD). The centre's existing RO plant reject water discharges to a floor waste gully and the existing RO pre-filtration plant currently discharges water to the nearby hand basin waste. The proposed project will reuse reject water for flushing toilets and will significantly reduce water wastage. Usage of potable water for flushing toilets will also reduce the energy use for supplying potable water to the site.
75,000 litres of water saved since project inception
CCLHD's capital works team developed the schematic design for storage and distribution of RO reject water to toilet cisterns throughout the centre. The engineering design was completed in 2022, with commissioning of the system completed in December 2023. Re-use of reject RO water has now been in place for more than seven months, supplying water to all toilets within the centre.
Since December 2023, this project has saved 75,000 litres (a forecast saving of 146,000 litres per year). There is the potential for a saving of 51kg CO2e and $730 on an annual basis. Scaling of the project to other larger facilities as a retrofit option is challenging due to complexities with existing infrastructure. However, new facilities could integrate this initiative into their design. Re-use of wasted water could also be considered in other areas such as sterilising departments.
