There are reports of success from an innovative wastewater treatment project in WA, using tress to do much of the hard work.

The innovative trial has reduced phosphorus at the Waroona Wastewater Treatment Plant by more than 50 per cent.

The interesting part is the fact that treated supplies are used to irrigate a woodland area before going down an agricultural drain.

Trials of the 700-metre 'swale' drain have seen phosphorus levels drop by nearly 60 per cent and nitrogen by more 30 per cent.

Peel-Harvey Catchment Council Chief executive Jane O'Malley told the ABC that the results are good for wetlands and for the treatment plant.

“It's all about stopping nutrients going into our Ramsar-listed wetlands,” she said.

“Monitoring is showing us that the swale draining is reducing the total phosphorus and nitrogen in the treated wastewater.

“The swale system is a relatively cheap and transferable environmental tool.”