Trees used in new wastewater treatment scheme

A new water reclamation project has been started in Missoula, US, which makes use of hybrid poplar trees. Thousands of trees have been planted on the 130-acre site, which will be watered with treated wastewater. Some of the chemicals in the water will help the trees' growth and in turn the trees will help to filter the wastewater. The project will stop the treated effluent from being released into the river.

So far 72,000 trees have been planted on the property, which has been leased by the Clouse family. The scheme has been 20 years in the making and will see the left over pollution from one in five gallons of wastewater created by the city of Missoula absorbed by the trees. While the trees are currently only saplings, they will grow quickly thanks to the contents of the wastewater.

Around half a million gallons of wastewater will be absorbed by the trees every day during the first 12 months of growth. After this, the irrigation levels will be increased to around 1.5 million gallons a day, which accounts for about 20 per cent of the Missoula Wastewater Treatment Plant's daily average. The plant usually releases around 7.5 million gallons a day into the Clark Fork River.

The lease on the land has been signed for 16 years, with a further 40 acres being planted on next year. In total, around 96,000 hybrid poplar trees will be planted on the site. In order to protect the trees, a wildlife-proof fence will be erected around the site, which will help to avoid damage caused by deer.

Around $2.1 million (£1.25 million) will be spent by the city over the next 15 years to develop the project. The trees will then be harvested in 2029, at which time around 2.8 million board-feet worth of sawlogs will be created, along with about 7,400 tonnes of biomass fuel.

Around 85 miles of irrigation pipe have been laid across the property to ensure that all trees receive the amount of water that is needed to ensure maximum growth and water treatment.