Wastewater Treatment Facility Tour
Construction of a new liquid processing train for the City of Buffalo Wastewater Treatment Facility (WWTF) directly adjacent to the existing wastewater treatment facility was initiated in March of 1997. Operation of the new facility began in November of the same year. New construction included a preliminary treatment building, two oxidation ditches, one clarifier, a return activated sludge building, effluentaeration, and standby power facilities.
The selected liquid treatment process was extended aeration activated sludge utilizing oxidation ditches. Oxidation ditches are very stable, requiring relatively little operation and maintenance resources, while providing advanced biological treatment. Effluent aeration and ultraviolet light (UV) disinfection follow the oxidation ditches and final clarifiers. Effluent aeration, accomplished by the use of a man made cascade waterfall, was used as a substitute for effluent filtration. Providing aeration, in lieu of filtration, saved the City of Buffalo over one million dollars in construction cost, in addition to saving in annual operation and maintenance costs. The additional saving in annual operation and maintenance costs made effluent aeration the treatment process of choice. The new facilities will serve a population equivalent of approximately 25,000 people.
Solids produced by the extended aeration process are inherently stable, providing several unique solids processing and disposal opportunities. A combination of aerated sludge holding and reed drying bed technology will be constructed in the future for sludge processing to reduce initial capital expenditures and annual operation and maintenance costs.
Raw wastewater arrives at pumping stations in town and is conveyed through a forcemain to the wastewater treatment facility. The incoming flow is metered by a Parshall flume. The wastewater then flows through preliminary treatment, consisting of bar screens, where rags, sticks, plastics, and similar materials are removed. These “screenings” are collected in a dumpster and hauled to a sanitary landfill. The wastewater then flows through a vortex grit chamber, where inorganic materials, such as pebbles and sand are removed.
Wastewater from the preliminary treatment system then flows by gravity to the oxidation ditches where microorganisms consume the organic matter that is suspended and dissolved in the wastewater. Mixing and oxygen, provided by Surface Aeration Rotors, are required for the microorganisms to grow and multiply.
The oxidation ditch effluent flows by gravity to a combination of a new 75 foot diameter clarifier and three existing smaller clarifiers. The clarifiers provide quiescent settling zones for the mass of microorganisms leaving the oxidation ditches. Microorganisms settle to the bottom of the clarifiers, referred to as “activated sludge”, is either returned to the oxidation ditches to maintain treatment efficiency, or is “wasted” to the digester to maintain a proper treatment environment.
Clear effluent, which flows off the top of the clarifiers, flows to a cascade waterfall. Turbulence created by the cascade aerates the wastewater, increasing the amount of dissolved oxygen. Additional oxygen in the treated effluent helps protect aquatic life in the receiving stream. Treated effluent flows to the existing disinfection channel where ultraviolet light kills harmful bacteria. From the disinfection channel the sparkling clear effluent flows to the North fork of the Crow River.
Current processing of the sludge wasted from the bottom of the clarifiers consists of aerobic digestion. Aerobically stabilized sludge, known as “biosolids”, are collected and beneficially land applied to provide nutrients to area farm land.
Future expansion of the City of Buffalo WWTF solids processing train will include a combination reed drying bed and aerated sludge holding system. Aerated sludge will be pumped the the reed drying beds for further stabilization, dewatering, and storage. The stabilized sludge, or “biosolids”, will act as a soil conditioner and fertilizer.