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Lucas County Maumee River Wastewater Treatment Plant
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Lucas County Maumee River Wastewater Treatment Plant
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In June 1970, a contract was signed by the City of Maumee, Lucas County, and the Ohio Water Development Authority to finance, construct, and operate a regional wastewater treatment facility to service Maumee, Waterville, Holland, and other limited portions of unincorporated Lucas County. Construction was started on the new wastewater treatment plant in March 1971. The Maumee River Wastewater Treatment Plant (MRWWTP) was placed into service in early 1973 as a 5 MGD activated sludge treatment plant with a hydraulic capacity of 12.5 MGD.
This original plant, later referred to as Plant “A”, consisted of three influent communitors and an aerated grit chamber for preliminary treatment, chemical addition for phosphorus removal, six activated sludge basins, two final effluent clarifiers, and a chlorine contact tank. The solids treatment processes included sludge-thickening tanks, a Zimpro low-pressure wet air oxidizer for sludge conditioning, and a vacuum filter for sludge dewatering.
Shortly after the commissioning of the MRWWTP in 1973, Lucas County and the City of Sylvania signed an agreement, which permitted the City to connect its sewers to the County’s regional trunk sewer. Lucas County also negotiated a contract with the Johns-Manville Corporation to treat the wastewater from their Plant No. 1 located nearby in Monclova Township. Flow from the Johns-Manville plant began entering the facility in June 1974. Shortly thereafter, a small portion of Wood County southwest of Perrysburg was also connected to the Lucas County trunk sewer. In 1988, the Village of Whitehouse completed their connection to Lucas County’s collection system.
1978-1980 Plant Expansion
In April 1975, planning was completed for expansion of the MRWWTP treatment capacity. The plant expansion called for the construction of a second set of treatment facilities capable of processing 10 MGD. The second new plant, referred to as Plant “B,” consisted of an aerated grit tank, a raw sewage pumping station and head tower, chemical addition for phosphorus removal, eight (8) aeration tanks for activated sludge treatment, two final clarifiers, and a chlorine contact tank. Plant “B” began full operation in May 1980 with a 21.5 MGD hydraulic capacity. This raised the total design/hydraulic capacity of the MRWWTP to 15/34 MGD.
1984 Solids Treatment Improvements
In 1984, the MRWWTP underwent some process changes to improve dewatering process that also reduced the treatment capacity of the facility. These changes included removing the Zimpro wet air oxidization system and the vacuum filter, converting the Plant “A” aeration tanks to aerobic digestion tanks, and installing a new 2-meter belt filter press. These changes resulted in the loss of 5 MGD of treatment capacity and 12.5 MGD of hydraulic capacity, but greatly improved the efficiency of the solids treatment process.
1994-1996 Plant Improvements
In 1994, the Maumee River WWTP underwent construction to upgrade the “Plant B” portion of the wastewater plant and return its treatment capacity to 15 MGD. These improvements included replacing the original influent comminutors with filter screens, adding three primary clarifiers, a third final clarifier, effluent dechlorination, anaerobic digestion, and an electric cogeneration facility using digester gas. The cogeneration system is designed to use the digester gas (or natural gas) for fuel in two engine driven electrical generators. After these improvements were complete, the MRWWTP abandoned the sludge thickening tanks and the aerobic digesters.
2003-2005 Plant Expansion
In 2003-2004, the Maumee River WWTP was expanded again to increase the design/peak capacity by 7.5/17.3 MGD (Plant total is now 22.0/47.3 mgd). These improvements were constructed as a totally separate liquid treatment train called the “West” Plant. The former Plant “B” is now called the “East” Plant. The West Plant treatment includes influent screening and grit removal for preliminary treatment, a primary clarifier, chemical addition for phosphorus removal, two 2-pass aeration basins for activated sludge treatment, two final clarifiers, and an ultraviolet disinfection system. The new West Plant was constructed with the future capability to be expanded to a design/peak capacity of 15.0/34.5 MGD.
In addition to the construction of the new West Plant, the County also made several improvements to the East Plant, the Anaerobic Digesters, Sludge Storage Facilities, and the Administration Building. The improvements to the East Plant included replacing the old centrifugal blowers with new, energy-efficient single-vane centrifugal blowers; replacing the coarse bubble diffusers in the aeration tanks with fine bubble diffusers; replacing the old chlorination/dechlorination system with and Ultraviolet Disinfection system; and, installing bio-scrubbers for odor control at the aerated grit chamber and raw sewage pumping station. The other changes to the MRWWTP included increasing the Anaerobic Digester gas line sizes, adding an additional dewatered sludge storage pad, and adding new offices, conference rooms, and storage space in the Administration Building.
Current Plant Operations
Wastewater from the Lucas County collection system enters the MRWWTP by a 90-inch trunk sewer. Liquid ferrous chloride is injected into the raw influent sewage as an odor control and phosphorus removal aid. The influent wastewater is then split to the East and West Treatment Plants.
Both plants utilize filter screens to remove material greater than ¼” in size from the waste stream. The filtered influent then goes through grit removal in both plants. The East Plant utilizes an aerated grit chamber for grit removal while he West Plant has a vortex type grit removal unit. The screenings and grit removed from the plant influents are stored on the plant’s sand filter drying beds, and then transported to a local landfill for disposal.
Both the East & West Plant influent flows are measured via Parshall flumes following preliminary treatment. The influent wastewater is then pumped to the primary settling tanks. Primary sludge (including raw and waste activated sludge) is pumped from the primary clarifiers the anaerobic digesters using progressive cavity pumps.
The primary effluents then flow by gravity to the aeration basins. Ferrous chloride is added to the aeration basin influent for both plants as a phosphorus removal aid. The primary effluent then receives secondary treatment via the activated sludge process in the aeration basins. The mixed liquor from the aeration basins then flows to the final clarifiers for solids separation from the secondary effluent. The clarified effluent flow is then measured in each plant via a Parshall flume prior to ultraviolet disinfection. The East & West Plant effluents are then re-combined and then discharged to the Maumee River.
As previously mentioned, the primary sludge from both the East & West Plants are pumped to one of the MRWWWTP’s three primary anaerobic digesters for stabilization, and then transferred to the secondary digester. The methane gas that is produced in the digesters is used to run the generators that produce electric power and hot water for the Digester/Cogeneration Complex including digester heating. Digested sludge from the secondary digester is pumped to the belt filter press for dewatering. The dewater sludge is then placed on a sludge storage pad.
The dewatered sludge is land applied as Class B biosolids by a sludge hauling contractor.
Future Plans
Presently, the MRWWTP is in the planning stage for the selection, purchase, and installation of a new centrifuge for dewatering digested sludge. Lucas County is currently pursuing financing and grants for the installation of the new dewatering centrifuge, and will advertise the project for purchase & installation of the new equipment this summer. The estimated startup date of the new dewatering equipment is mid-2009.
The installation of the new centrifuge will be adjacent to the existing belt filter press, where it will use the existing truck loading conveyor. The belt filter press will be retained as backup dewatering equipment in the event the centrifuge is out of operation for service or repair. The long range plan for the facility is to purchase a second centrifuge and construct a new dewatering building adjacent to the sludge storage pads.
The wastewater flows for the Lucas County Sewer Service Area are projected to be met by the facility’s most recent 7.5 MGD plant expansion through the year 2020. An additional expansion will be needed to meet projected treatment needs beyond 2020. The groundwork for the next expansion was laid-out during the 2003-05 project when the West Plant was constructed with built-in expandability to 15/34.5 MGD. The projected treatment equipment needed for the future West Plant expansion include a third influent screen, a second vortex grit removal unit, additional raw sewage pumping, a second primary clarifier, another 2-pass aeration tank, a third final clarifier, additional RAS & WAS pumps, and four additional banks of UV bulbs.
Additional anaerobic digester capacity will also likely be required for the next expansion. The current long range plan calls for the construction of two additional primary digesters adjacent to the existing tankage on the south side.
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