Located at Nicholson Road, Ferndale, the $1 million plant has doubled the capacity to provide oxygen relief upstream of the Kent Street Weir.
Environment Minister Albert Jacob said the new plant would ensure an extra 2.2km of the river could have adequate oxygen levels at all times.
When oxygen levels are low, it can harm aquatic life.
Summer and autumn is when oxygen levels mostly fall because of the decomposition of excess organic matter and nutrient.
Adequate oxygen levels help provide a refuge for fish, improve nutrient cycling, speed up the breakdown of organic matter and prevent offensive odours.
Mr Jacob said the Government had also invested $1.4 million to upgrade the two older oxygenation plants upstream of the Kent Street Weir.
They service 2.3km of the Canning River.
‘The two older plants, which are now 15 years old, will be upgraded using the latest technology once the performance of the new Nicholson Road plant has been confirmed,’ Mr Jacob said.
He said the oxygenation program was one component of the State Government’s catchment-to-coast approach to protect and improve the health of the Swan and Canning rivers.
The oxygenation program began in 1998.
There are two plants on the Swan River and three on the Canning River.