The original sewers in Marysville were installed in 1913. At that time, the system was comprised of about 13 miles of six or eight inch clay gravity lines and a small pond. In 1932, the first anaerobic digester was built and the Imhoff tanks and the treatment pond were enlarged. In the 1950s, two aeration tanks with agitating aerators were added along with final clarifiers and sludge-drying beds.
The first large expansion was in 1964, This included the addition of another larger primary anaerobic digester, conversion of the Imhoff tanks to primary clarifiers, grit-removal system, one additional aeration tank, a blower building and blowers to provide aeration, an additional final clarifier, and disinfection facilities.
In 1982, construction began on an upgraded treatment plant. The facility was a two-stage activated sludge plant with tertiary filters. The facility included pretreatment, primary clarifiers, additional aeration tanks, intermediate clarifiers, second-stage aeration tanks and blower building, final clarifiers, effluent pumping, tertiary sand filters, chlorine and chemical feed systems, an equalization basin, administration building with a laboratory, a secondary anaerobic digester, and new sludge-drying beds. This expansion brought the total design capacity to 2.3 mgd.
In 1989, work began on a 1.7 mgd Orbal oxidation ditch and an additional final clarifier. This expansion was added as a second flow train and ran parallel with the 1982 plant. A small pump station was also built to split the flow before pretreatment with approximately 58% of the flow directed to the existing two-stage facility and 42% to the Orbal facility. This brought the total design capacity to 4.0 mgd.
Two belt filter presses were installed in 1995 to dewater digested solids. The first anaerobic digester built in the 1930's was converted to a lime-holding tank to store used lime from the City Water Treatment Plant to be dewatered along with wastewater biosolids.
In 2000, a new headworks building with influent pumps, grit removal, fine screens, and flow diversion structure was constructed. This facility replaced the pretreatment building constructed in the early 1980's.
In 2003, the anaerobic digester was converted to an aerobic digester. The digester was modified and placed in operation in 2005.
In 2004, the city completed its Wastewater Master Study. The study recommended that a new water reclamation facility be constructed to replace the existing facility, which was nearing the end of its useful life and was in dire need of upgrade/expansion. In 2009, a new facility was strategically located on Beecher-Gamble Road so that it could serve existing customers as well as potential future high-growth areas. It was designed to meet more stringent current and future regulations and to be readily expandable in 2-mgd modules in order to meet future needs cost-effectively and expeditiously.
Wastewater Conveyance System
The wastewater conveyance system was designed to eliminate numerous lift stations throughout the existing collection system and minimize the number of future pump stations in order to increase reliability and reduce maintenance costs