Most of us don’t think about what happens to the water that we use in our homes and businesses once it goes down the drain, but it doesn’t just disappear. It is reclaimed. Reclaimed water is cleaned at special treatment facilities. In 2018, the city of Franklin broke ground on a new reclamation facility, the largest capital expenditure investment they have ever made. It is coming down to the final year of construction, scheduled to open in 2022.
There are three stages to producing reclaimed water. Water is first put into large concrete tanks where heavier solids sink to the bottom and lighter materials float to the top. Screens catch the debris. Waste water and dissolved organic matter goes into aeration tanks for the next step. Here oxygen is run through the water to awaken microorganisms that then fall to the bottom of the tank. Lastly, the water is filtered.
According to renergy.com, “once the water passes through these filters, it’s disinfected and considered safe for irrigation, cooling systems and, in some cases, even drinking water.”
Waste water is reclaimed because potable water is scarce. In Franklin, once the new reclamation facility is completed, the city will be allowed to discharge 16 million gallons a day into the Harpeth River. Currently, that quantity is much less. They also sell the water to golf courses, home owner associations, and even the pond at Westhaven.
“The new plant will allow the city to catapult water treatment to a higher level of treatment,” said Michelle Hatcher, Director of Water Management for the city of Franklin. “It will allow us to increase the amount of water treated, remove more of the nutrients that cause algae in the river, and add a new storage tank that will allow 10 million gallons of waste water to be stored during a wet weather event.”
With new technologies, the processes in the plant will be more efficient, saving energy and also increasing the amount of water treated. When it is completed, it will be cleaner than what is currently in the Harpeth.
The project includes construction of a new equalization tank with mixing capabilities, construction of an upgraded headworks facility, addition of both biological and chemical phosphorus removal capability, construction of a new UV disinfection facility, upgrades to the reclaimed water pump station, upgrades to the facility-wide odor control, significant electrical improvements, implementation of a new SCADA system, construction of a new solids processing building, construction of a new thermal hydrolysis process skid, and construction of three new anaerobic digesters.
Monthly updates on the construction can be found on the City of Franklin website. According to July’s updates, “the new equalization tank and headworks structure are finished and crews are working through factory testing of all of the equipment housed inside them. From start-up observations, the headworks is more efficient and removes more debris and grit from the incoming wastewater flow, protecting downstream equipment from the wear and tear of the objects found in wastewater… [In another building,] digesters will stabilize the solids per EPA recommendations. Gas that is produced from the digesters will [be]…turned… into energy and be used back in the facilities grid to offset power costs.”
According to Hatcher, “Historically, water reclamation treatment plants have the highest consumption of electricity because they run 24/7. This will reduce electrical consumption from the grid.”
The last updates to the water reclamation facilities were made 20 years ago, and technology has made large strides since then. This update was planned to take into account the growth of Franklin.
The total project, which will take close to four years to complete, will have a total cost of $132,890,000. It is located on Claude Yates Drive near the Harpeth River. It will be completed by Kiewit Infrastructure South Company.