Flushing the toilet was literally money down the drain for the city of Fayetteville, so the city developed a program to turn that wastewater into cash while improving the environment at the same time.
The moves have earned Fayetteville recognition as a 2012 Arkansas Business City of Distinction for Green / Energy Conservation Initiatives.
The northwest Arkansas city uses two plants to treat wastewater before releasing the cleaner water back into the environment, said Duyen Tran, CH2M Hill project manager for the Fayetteville Wastewater Treatment Facility. CH2M Hill of Englewood, Colo., operates the facility.
“The treatment plants clean the wastewater using a mostly biological process that feeds the incoming wastewater to a population of microbial bugs,” Tran said. “The bugs are colonies of bacteria and other microorganisms that feed on waste.”
Eventually, though, those microorganisms multiply and have to be removed from the wastewater stream and that creates biosolids.
“The biosolids generated create a significant volume of wet-solid waste that must be disposed of in an environmentally responsible manner,” Tran said.
In 2003, CH2M Hill started hauling biosolids to landfills in Arkansas and neighboring states. On a typical day, however, 100,000 wet pounds of biosolids required more than two trips to landfills, which cost nearly $1 million annually in fuel, labor, landfill fees and equipment costs.
“The city of Fayetteville puts great emphasis on sustainability and, consequently, knew that other options needed to be considered for biosolids disposal,” Tran said. “After considering a variety of options, the city and CH2M determined that a combination of solar and thermal drying of the wet biosolids would be the best course of action.”
Drying the biosolids would reduce the trips to landfills and dried biosolids could be sold for fertilizer.
The city invested $9 million in equipment to dry the biosolids by using solar energy and natural gas, Tran said. In the middle of 2011, the city opened six solar drying houses built next to the Paul R. Noland Wastewater Treatment Plant.
“The solar houses are essentially greenhouses that use solar energy … to remove a majority of the water from the wet biosolids,” Tran said.
The city now spends less money on hauling wet biosolids to landfills. In the first six months of 2010, 499 semitrailer loads filled with 1,906 tons of wet biosolids were shipped to landfills, Tran said.
“With the dryers, that number dropped by more than 50 percent in the first half of 2012,” saving the city $336,000 since May 2011, he said.
Drying the biosolids also reduces space in landfills, Tran said.
“Across the United States, landfill capacity is diminishing and alternative disposal methods are becoming much more important,” he said. “Fayetteville is ahead of the curve.”
Since the dried biosolids have been approved by the Arkansas State Plant Board to be used as fertilizer, the city has been selling it to farmers and residents.
In March, approximately 250 tons of biosolids, at approximately $15 a ton, were sold to the public, Tran said. He said there is a waiting list of people wanting to buy the fertilizer, which is another benefit to the environment.
The biosolids help improve soil nutrients and enhance the soil.
“Enriched soil may provide better yields and reduce the need for chemical fertilizers,” Tran said.
Tran said other Arkansas cities could follow Fayetteville’s blueprint, but they could save money by not installing both solar and thermal dryers or by reducing the number of dryers installed.
“Every city has wastewater that needs to be treated,” Tran said. “By drying the biosolids, cities can provide a benefit product to their communities while also reducing their operational costs and helping the environment.”