PIQUA — Almost a year into a nearly three-year construction project, several settling tanks and buildings are beginning to appear at the Wastewater Treatment Plant where quarry field was located a year ago.
In eight months of construction, the plant is seeing the building of three final settling clarifier tanks that are 125 feet in diameter by 16 feet deep. The plant is also seeing the beginnings of the extended aeration oxidation ditches and a head works building start to form.
The installation of a 42-inch pipeline that will be 42 feet underground is also under way, Wastewater Treatment Plant Superintendent Chris Melvin explained. The pipeline will attach the plant’s existing wet well and run to the new wet well and the head works building, which will also include an electrical room, switchgear for the new 1500KW standalone generator, a control room, and a heated dumpster area.
From the head works building, the flow will proceed to both of the new extended aeration oxidation ditches, Melvin said. The extended aeration oxidation ditches have a serpentine flow pattern and modulation zones for biological nutrient removal, including phosphorus and nitrogen that can contribute to harmful algae blooms.
The oxidation ditches also qualified the city to be eligible for a zero percent interest loan for a portion of the project due to it removing biological nutrients.
“We’re going to save $21 million in interest,” Melvin said.
From the oxidation ditches, the flow will go into the final clarifiers, which are settling tanks for the continued removal of solids.
Between these final clarifiers will be a new secondary control building, the basement of which will consist of four return-activated sludge pumps and two waste-activated sludge pumps, Melvin explained. The return pumps can either pump directly from an individual clarifier tank or draw from all the clarifier tanks at once. The waste-activated sludge flows are going to be pumped to a repurposed sludge storage tank, where a new aerated grid and new blowers are being placed, according to Melvin.
Effluent flow from the final clarifiers will travel to a modified chlorine contact and post aeration system, and these tanks are being converted to a new UV disinfection station, Melvin said. UV light requires more energy, but it is a safer way to disinfect the flow than with chlorine and sulphur dioxide.
The head works structure, oxidation ditches, final clarifiers, and secondary control building are all being built on abandoned quarry land that Piqua Materials Inc. donated to the city of Piqua.
The project was mandated to eliminate the city’s sanitary sewer overflow (SSO), or untreated wastewater that overflows into the Great Miami River. The renovations will allow the plant to accommodate 8.7 million gallons of wastewater flow per day (MGD) and a new peak hourly flow of 22.5 MGD. Design flow is nearly twice that of existing and new peak flow is nearly triple the current peak flow, according to Melvin.
Peterson Construction Company is completing the construction of the upgrades and expansion of the $40 million project. The project is being funded through a loan from the Ohio EPA Department of Environmental Financial Assistance (DEFA) for the project. Construction is scheduled to be complete in the summer of 2020.
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