(from LFUCG website, www.lfucg.com)
History of the Town Branch Wastewater Treatment Plant
The Town Branch Wastewater Treatment Plant began operation in 1919 and was one of the first sewage treatment plants in this section of the United States. The facility is located on Town Branch north of Old Frankfort Pike approximately 1/2 mile inside New Circle Road. The original plant consisted of Imhoff tanks, trickling filters and sludge drying beds. In 1935 sludge digesters and pretreatment screens were added and the plant had a capacity of approximately 6.0 mgd. In 1947 two additional sludge digesters were constructed. A major expansion was begun in 1960 and completed in 1963. This construction was comprised of facilities which converted the plant into a 12 mgd activated sludge plant utilizing the Kraus process. In 1971 another expansion to Town Branch was begun which increased the capacity to 18.0 mgd adding sludge disposal facilities which ultimately eliminated the use of sludge lagoon and drying beds at this site. Construction was completed in 1974.
In 1981 a Process Alternative Study selected a single stage aeration system with a capacity of 30.0 mgd to meet the future needs of the service area and to meet the more stringent effluent limits. The design was also required to add dechlorination to the facility unit processes. Due to the magnitude of the project the project was segmented both in design and construction. Design began in 1984 with design on the remaining phases starting in 1985 and completed in July, 1987. The plant is designed to treat wastewater generated from approximately 60 percent of Fayette County serving an eventual population of 130,000. Under normal operation, the treatment plant is expected to remove in excess of 90 percent of the incoming loads of total suspended solids, 5-day biochemical oxygen demand, and ammonia nitrogen. This advanced secondary treatment facility is designed for a flow of 30 MGD but the plant can hydraulically treat a maximum flow of 64 MGD.
BRIEF OVERVIEW OF THE PROCESSING
AT TOWN BRANCH
A network of pipes and pumps located within Lexington/Fayette County is used to collect untreated wastewater from the community and transport it to the Town Branch Wastewater Treatment Plant. At design conditions, almost 11 billion gallons of wastewater are treated on an annual basis.
The first treatment units at Town Branch are “preliminary treatment” processes where potentially equipment-damaging materials are removed. Large debris is removed as wastewater flows through trash racks. Next, finer materials are removed by mechanical fine screens. Screened flow is directed to grit chambers where abrasive materials such as sand are removed. “Primary treatment” follows the headworks where the velocity of the wastewater flow is slowed in primary clarifiers so that solids can be settled and lighter materials such as grease are floated out of the wastewater.
Biological treatment follows primary clarification where the aeration process converts remaining fine and dissolved organic pollutants into biological solids. Air is applied to the aeration tank contents which allows aerobic bacteria to assimilate pollutants contained in the wastewater. Ammonia is also removed in the aeration process. Final clarifiers follow the aeration process where the biological solids separate and settle from the wastewater as the velocity is decreased.
Flow leaving the final clarifiers is directed to the disinfection process. Chlorine is used to disinfect the plant effluent before it is discharged to the Town Branch. Sulfer dioxide is used to remove residual chlorine. Wastewater leaving the disinfection process flows over a cascade step aerator which adds oxygen to the effluent.
As wastewater is treated as described above, by-products are generated. Screenings and grit are dewatered and then delivered to a landfill. All sludges are thickened either by gravity thickeners or centrifuge and then are pumped to the anaerobic digesters. Anaerobic bacteria reduce solids in the sludge to a stable and dewaterable product. Water is removed from the digested sludge by mechanical belt filter presses and then the sludge is trucked to a landfill for ultimate disposal.