Gwinnett County Commissioners on Tuesday approved a $16.5 million add-on facility to the Wayne Hill water treatment plant that will allow county water and sewer department officials to mine phosphorus that builds up inside of the plant’s pipes and sell it as fertilizer.

It will be only the seventh plant in North America to use the process.

The project, set to break ground early next year, will be funded by rate payers but will pay for itself in about 13 years through savings on maintenance, chemicals and the revenue from fertilizer sales, said Tyler Richards, deputy director of engineering and technical services for the department. The county is expecting to save about $750,000 annually on maintenance and chemical costs; and earn about $500,000 in fertilizer sales.

“We’re turning a problem into a benefit,” Richards said.

The Wayne Hill plant opened in 2001 and processes about 30 million gallons of waste water daily. It discharges the treated water into Lake Lanier, a major source of recreation and drinking water. Because of that, the county has stringent requirements for the phosphorus levels in the discharge because it causes algae blooms that foul the water.

Richards said the plant has no problem stripping the waste water of phosphorus. But as a result of those processes, the phosphorus coats the inside of pipes and hardens when it mixes with other chemicals. Workers then have to chip it out.

“It comes out in slabs,” and is sent to a landfill, Richards said. “It’s very expensive and inefficient because we have to take equipment down.”

The new facility will use a chemical process to convert the byproduct in pellets that can be sold as fertilizer. The county’s contract with Ostara USA, which developed the process, calls for the company to buy the pellets. The county will use Ostara’s equipment in its new building.

Commissioners approved the new facility without questions or discussion. It must also be approved by the county’s Water and Sewer Authority. The facility is expected to be operational by the end of next year.

Gwinnett County Commission Chairwoman Charlotte Nash said she is convinced its a wise investment “that will pay off in savings over the long run.

“I am comfortable with our decision to proceed with this project,” Nash said. “Despite there being a relatively small number of similar operations in North America, there is a track record for this approach, both here and in other parts of the world.”