Recently completed improvements should extend the life of the south Davis sewage treatment plants 20 to 25 more years, the district plant manager told Centerville's city council Tuesday.

And, if the state grants permission, the treated effluent from the two plants could add 15,000 acre-feet of irrigation water annually to the county's water reserves.Plant manager Dal Wayment told the council the district is asking the state for permission to add additional treatment steps to its process and eventually sell the effluent as secondary water, to be used for irrigation and watering.

North Salt Lake has already expressed an interest in the water for a golf course it is proposing the build and Centerville city officials, also considering building a course, likewise expressed interest.

Wayment said with additional treatment, including chlorination and perhaps ultraviolet exposure, the effluent would be of similar or better quality than irrigation water supplied by the Weber Basin Water District.

The two plants operated by the district, one in West Bountiful and one west of North Salt Lake on the Jordan River, currently dump their effluent into the Great Salt Lake.

The effluent, under federal environmental rules, is already of a higher quality than the lake water, Wayment said.

"It kind of hurts to produce a product as pure as we do, then dump it into the Great Salt Lake, where it doesn't do anyone any good," Wayment said. "It's gratifying that we may have further use for it as irrigation water."

Wayment said the West Bountiful plant produces about 5,000 acre-feet of effluent annually during the irrigation season and the smaller south plant another 2,200 acre-feet.

If storage or holding ponds could be built to impound the effluent produced during the winter or non-irrigation season, the amount available annually could be doubled, Wayment said.

District board member Vernon Carr told the council that improvements made to the West Bountiful plant are 99 percent completed and cost $6.8 million, or $1.2 million less than engineering estimates.

The improvements increased the plant's capacity from 10 million to 15 million gallons, Carr said, which using current population projections should provide the district with sewage treatment capacity for the next 20 to 25 years.

One of the improvements added is the installation of a power plant that runs on methane gas, a byproduct of sewage treatment. Instead of flaring off the gas, the plant now uses it to produce power, making it about 50 percent energy independent, Carr said.

Depending on implementation of new federal environmental regulations, the plant may not need significant upgrading or expansion over the next two to three decades, Wayment told the council.

But if currently proposed regulations are imposed, the district may face expensive additional treatment steps, he said.

And sludge disposal could also become a problem. The new proposed regulations are 700 pages thick and could require the plant to find a new way to dispose of its sludge, either hauling it to the county's garbage-burning plant or building its own single-use landfill.

The district currently spreads out the sludge, drying it for a year and then giving it away to turf farmers, landscapers and homeowners.