LAUREN HAMILL | Scroll Photography

LAUREN HAMILL | Scroll Photography

Due to the continuing use of landfills, Rexburg’s Wastewater Treatment Plant plans to upgrade its facility in summer 2015, Keith Davidson, a professional engineer of Rexburg, Idaho, said.

Mayor Richard Woodland of Rexburg said the purpose is to produce Class A biosolids and cleaner water.

Biosolids are residual solid material from a city’s wastewater, according to

“Wastewater is used water,” according to the USGS Water Science School website.  “It includes substances such as human waste, food scraps, oils, soaps and chemicals.”

Woodland said wastewater comes in from Rexburg, Sugar City and Teton City.

“It’s pretty interesting where it all comes from,” Woodland said.

Davidson said the treatment plant currently uses aerobic digestion.

Aerobic digestion is a natural waste breakdown and purifying process aided by bacteria in an oxygen-rich environment, according to the Water/Wastewater Distance Learning website.

Donna Archibald, foreman of the Wastewater Treatment Plant, said the biosolids are aerated with 5000 pounds per square inch of oxygen in a bio-tower.

Davidson said the bio-tower runs on 370 horsepower during aerobic digestion.

He said that after aeration in the bio-tower, the substance goes into a clarifier where the solids are separated from the liquids.

Davidson said the liquid from the wastewater goes to an ultraviolet light tank for sanitation.

“It’s cleaner than the river,” Woodland said.  “You could drink it.”

The treated water is tested daily for quality then released into the Teton River, according to the City of Rexburg Public Works website.

Davidson said the solids go from the clarifier to a gravity belt thickener, then to a screw press where liquid polymer is added to thicken them from 1 percent solid to 16 percent solid.

This process produces Class B biosolids, which contain low, detectable levels of pathogens. These low levels are not a threat to human health or the environment if exposure is prevented after disposal of biosolids, according to the United States Environmental Protection Agency.

The new anaerobic process is a different natural breakdown of waste.  The organisms at work do not need oxygen to live, according to the Water/Wastewater Distance Learning Website.

This process produces Class A biosolids, which contain undetectable levels of pathogens or bacteria, according to the United States Environmental Protection Agency.

Davidson said biosolids are heated and sterilized during anaerobic digestion.

Davidson said they produce methane gas during this process.

“Eventually, if you have enough methane gas production, you can create energy,” Davidson said.

Woodland said the Rexburg community and BYU-Idaho campus will not feel the effects of the methane energy because it will be used at the plant.

Davidson said the new process will allow the facility to hold a larger capacity of wastewater, so the city’s capacity for population will increase.

According to the Rexburg city council minutes from January 7, Justin Logan, a professional engineer of AQUA Engineering, said the methane gas produced is captured and used to heat the product for the next batch of biosolids in the anaerobic digestion process.

Davidson said the methane gas will be used to heat the wastewater for pasteurization and as further radiant floor heating to help the biosolids dry during winter.

Logan said the process will be cost-effective and self-sustaining, according to the city council minutes.

Woodland said the Class A biosolids can be disposed of anywhere and  can be used as fertilizer and potting mix for gardens and farms.

“It’s fibrous and holds quite a bit of water,” Woodland said.

The treatment plant currently produces Class B biosolids, which cannot be used as fertilizer, Davidson said.

Woodland said the Class B biosolids are taken to a landfill in Jefferson County, and the cost of transport is 60 dollars per ton.

“We want Class A, so we can sell it instead of paying people to take it,” Woodland said.