$100m to make sewage drinkable

Construction of a plant to turn treated sewage into drinking water could begin within two years after the Barnett Government allocated more than $100 million to the project in this week's Budget.

In the clearest sign yet the Government wants to use recycled wastewater to prop up supplies, Thursday's Budget delivered $108 million over four years for "groundwater replenishment".

The decision paves the way for the full-scale expansion of a trial in which highly treated sewage is pumped into underground aquifers at Beenyup in Perth's north before being extracted years later.

With the landmark $50 million trial due to finish by the end of the year, most of the money has been slated for spending in the Budget's final two out years in 2014-15 and 2015-16.

The Government committed $2.5 million in 2012-13 for "preliminary design and investigation works".

Environment Minister Bill Marmion said the rest of the money had been provisionally set aside because it was important the Water Corporation could expand the trial if it proved successful.

Mr Marmion said construction of the first phase of the upgrade, which would produce up to seven billion litres of water a year, could start by 2014 and be completed by the end of 2015.

Subsequent stages would be added separately and be expected to cost significantly less.

However, any expansion would depend on whether the trial was given the green light by the Health Department and was supported by the broader community. "We put the money in the forward estimates, that means we're fair dinkum," Mr Marmion said.

The move will come as a relief to the Water Corporation, which has come under mounting pressure in recent years over its reliance on the stressed Gnangara groundwater system.

As part of its 10-year blueprint, the State-owned utility identified "aquifer recharge" as a central plank of its plans for Perth.

Shadow water spokesman Fran Logan said the commitment to recycling in the Budget was a "step in the right direction" but fell woefully short of was needed.