BY MARK J. CRAWFORD
The completion of Starke’s new wastewater treatment plant is on the horizon, but there is one last-minute design change that could save on future operational costs.
Repurposing a failed investment could lower the city’s annual cost of sludge removal from the plant, according to Justin deMello, principal project manager with Woodward and Curran.
Woodward and Curran has already improved the ratio of solids in the sludge since taking over operation of the plant. Employees have been considering the usefulness of an existing screw press already on site to further dewater the sludge.
Since the city is charged by the gallon for what is removed from the plant, removing more water from the mix reduces disposal costs and opens up more disposal options.
The screw press is part of the “Neutralizer” the city acquired from BCR Environmental in the late 2000s. Then, too, the plan was to reduce or eliminate sludge hauling costs by removing the water and turning what was left into a high quality fertilizer. The system rarely worked as intended and its inoperability became a source of conflict between the city and the company.
DeMello told city commissioners the new plant was designed with dewatering boxes for the sludge instead of the digester currently used, but they’ve asked the contractor to hold off as they attempt to get approval from USDA to rehabilitate the screw press. USDA is funding the project, providing a partial grant, as well as a partial loan that the city must repay.
A standard 5% of the funding was set aside as contingency to cover any unforeseen costs, but the $23 million project has had only $156,000 in change orders, which deMello said is unheard of. It leaves room to fund rehabilitating the screw press, which has just been sitting there like a “paperweight,” he said. Additional costs for engineering and tying the press to the plant could be covered if USDA approves the project changes.
Savings could be significant. The city spends around $180,000 a year on sludge removal and disposal. That will go up as the hauler raises the price per gallon and as the city grows, deMello said. A larger volume of wastewater coming into the plant will lead to more solids removal on the back end. The less water in that sludge, the less the city will pay to haul it away.
It will also mean the city can get some return on its initial investment in BCR’s system, which was scheduled to be sold for scrap.
“We’ve always felt that was a shame. And then, since Woodward and Curran took over operations, our team is like, ‘Hey, this is great stuff. We can reutilize this. We can make it run again. We can make it sing.’,” he said.
According to deMello, the screw press has the potential to double the concentration of solids in the sludge. The estimated cost of the rehabilitation, engineering and other construction is $410,000, which is available in the project contingency funds. This additional investment would be paid back in a few years by the reduced disposal costs. DeMello said a conservative estimate of the savings was around $100,000 a year, even with the additional maintenance costs for the screw press. Part of the savings is the potential to dispose at a local landfill instead of a landfill north of Orlando where the hauler currently transports the sludge, and deMello mentioned the possibility that the city could one day take over transportation.
USDA wanted to see the city commission approve an amended agreement with Woodward and Curran before approving the project change, so the board unanimously approved a resolution to that effect.
