Downriver turns on effluent sprinklers

Class A treated wastewater is being sprinkled on a small section of Downriver Golf Course in a pilot project designed to find an alternate use for effluent water coming from Spokane’s sewage-treatment plant.

The “purple pipe” irrigation system, which includes a high-tech filter, began operating Aug. 29 after being installed earlier this year south of the clubhouse along Riverview Drive on Spokane’s North Side.

Last week, wastewater officials held a briefing at the site to kick off the new system.

“It’s a small pilot, but it’s got a lot of pieces,” said Lars Hendron, city wastewater engineer for the project.

Eventually, the city could have as many as seven locations using class A wastewater for irrigation through small satellite treatment facilities.

The city’s four golf courses use about 2 million gallons of water a day for irrigation during the summer. The small facility at Downriver delivers only about 5,000 gallons a day to a special irrigation system at the tee for the sixth hole and the fairway for the seventh hole. But it has the capacity to deliver up to 20,000 gallons.

The system uses purple pipe to distinguish it from potable water. Filtration occurs inside a Tuff shed along the bluff below Riverview Drive.

The system uses effluent water from the city’s wastewater-treatment plant to reduce suspended particles and phosphorus in the Spokane River. The water is considered safe for human contact but not sufficiently clean to drink.

The idea is to reduce the amount of phosphorus going into the river from the wastewater-treatment plant each day.

Reusing the water also reduces the amount of water being taken from the Spokane Valley-Rathdrum Prairie Aquifer, the region’s source of drinking water.

Downriver is the first such project in Spokane – and possibly Eastern Washington – although the technology has existed for 20 years, said Dale Arnold, wastewater director.

The cost of the pilot project is $1.2 million and will include installation of a similar filter system at the Creek at Qualchan Golf Course next year.

Wastewater for both golf courses is being delivered from the sewage-treatment plant by truck.

Separately, the city is purchasing and installing six test units to study what type of filtration system would work best in Spokane as part of a larger upgrade of sewage treatment to meet Clean Water Act standards.

Eventually, those units could be redeployed to other locations for other satellite irrigation projects. They could be configured to tap into sewage flow above the treatment plant and eliminate the costly effort to truck water to the sites, Arnold said.