Pre-treatment by microfiltration followed by water hardness reduction then desalination using reverse osmosis
Near Chinchilla, Queensland
Challenge Huge volumes of groundwater can be extracted during the production of coal seam gas. Saline and containing sediments including coal particles, this water cannot be returned to the environment or reused without treatment. Evaporation dams commonly used to deal with this problem are both expensive and not suitable as a long term solution. Desalination by reverse osmosis is a viable option, however vastly varying water flow levels from any one well plus significant changes in salinity demand flexibility in plant design and sizing.
Solution Osmoflo's solution involved the provision of a treatment system that provides this flexibility at 80 - 90% recovery without impacting on plant performance. Designed to integrate with exisiting infrastructure, the plant draws on produced water stored in ponds. Salinity can vary from 1,500 mg/l Total Dissolved Solids (TDS) - three times more than Australian Standards for drinking water - to 10,000 mg/l TDS.
Following microfiltration to remove particles, the water passes through a hardness reduction unit which extracts magnesium and calcium facilitating the removal of commercially valuable salts, such as sodium. The next stage involves passage through reverse osmosis desalination membranes. Treated water, which has a salt content of less than 300 mg/l TDS is compliant with water dissposal regulations and can either be safely discharged to the environment or used for irrigation. The reject water is concentrated brine from which salts can be recovered following evaporation.
Operation is monitored from Osmoflo's 24 hour control centre at Burton SA, utilising proprietary PlantConnect technology.
Result QGC's reliance on large evaporation dams has been reduced and the company has confidence that discharges to the environment will be fully compliant with regulations. In future, recovery of commercially valuable salts may help to reduce overall operation costs.
QGC produces about 20% of Queensland's gas demand