By Alison Ecklund
Larson Newspapers
The city of Sedona’s wastewater treatment plant will be the benefactor of a $430,000 desig n for new drying beds to get rid of the sludge it produces daily.
On May 12, Sedona City Council agreed, 6-0, in its consent agenda to approve a $430,750 contract with Carollo Engineers to design air/solar biosolids drying beds.
Each day the city’s wastewater treatment plant takes in approximately 1.2 to 1.5 million gallons, Director of Public Works Charles Mosley said. The plant has the capacity to take in up to 2 million gallons, but the drying beds, for solids, cannot dispose of that amount.
“As more waste comes in, we need more capacity for disposal,” Mosley said. “We need to make sure that what we treat, we can get rid of.”
According to Mosley, 1.6 million gallons would be difficult to dispose of, so now is the time to start planning.
Solids are currently aerobically digested at the plant, before the sludge is laid out on the beds to dry under the sun, he explained.
The beds are made of concrete and have a sand underlay with pipes underneath. When water drains out of the sludge, the pipes pick up the water and take it back to the liquids, Mosley said. Once the water is out of it, the sludge is transported to Grey Wolf landfill.
The city’s current air-drying beds are deteriorating, Mosley said, and the capacity for sludge isn’t big enough for possible future intake.
Carollo’s design will be similar to the air-drying beds currently at the plant but in February, council directed the design to allow the new beds to be retrofitted in the future with a thermo-system solar drying unit.
In the future, the beds could be covered, to allow drying at higher temperatures, Mosley explained. Drying the sludge at high temperatures disinfects it, allowing it to be used as compost and put in soil instead of being thrown away.
Based on council’s direction, Carollo will come up with the design, specifications and a cost estimate to build, before the project goes to bid, he said. Mosley hopes the project will be ready to go out to bid by June 2010.
Fiscal year 2009-10 budget allows $1.5 million for final design and construction of the new drying beds. Construction of the beds is estimated to cost $900,000.
“We’re using $430,000 for the design so we have plenty of money left for construction,” Mosley said.
As the city continues to expand its sewer lines, the wastewater plant is also looking to increase its capacity to dispose its liquid effluent.
On Feb. 24, council awarded Carollo a $152,125 contract to begin seeking necessary permits for an aquifer recharge project to dispose of the plant’s effluent. The study will primarily focus on injection wells to get rid of the city’s liquid waste.
Mosley estimates each of the city’s dwellings generates 200 gallons of wastewater per day.
The alternative to expanding the capacity for disposal at the wastewater plant would be to stop expanding the sewer system, he said.
Alison Ecklund can be reached at 282-7795, ext. 125, or e-mail
aecklund@larsonnewspapers.com
