The Ann Arbor Wastewater Treatment Plant (WWTP) receives and treats approximately 19.0 million gallons of wastewater per day from the City of Ann Arbor, Pittsfield, Scio, and Ann Arbor Townships.
The City of Ann Arbor authorized a study effort to evaluate the condition and performance of the City's WWTP facilities. Finalized in 2004, the results of the study revealed that the plant’s existing residuals handling facilities, which processes the residual solids in wastewater, needed to be replaced. The aging biosolids processing equipment was constructed in 1978 and has exceeded its useful operating life. As a result, operating efficiency has declined and maintenance has become increasingly more challenging and costly. Replacement of these equipment and systems is necessary for the WWTP to improve process reliability and meet current and future solids processing capacity requirements.
The City has developed a plan to replace equipment and improve the existing residuals handling facilities to provide for the continued efficient and cost-effective operation of the WWTP well into the future.
Greeley and Hansen, an engineering firm specializing in wastewater system design, has been retained by the City for design of the improvements. The following tasks were performed during the design effort:
· Visits to other wastewater treatment facilities to evaluate their application and use of more efficient biosolids thickening, dewatering, stabilization, and off-loading equipment.
· Surveys of other wastewater treatment facilities regarding actual equipment performance.
· On-site pilot testing of biosolids dewatering equipment and evaluation of performance results to determine if the equipment meets the City's design requirements.
· Plant-wide odor control study and preparation of a plant-wide odor control report.
· Public meetings with WWTP neighbors to discuss and address their concerns for odor and noise control.
· Design of new solids handling facilities, including new equipment and rehabilitation of existing facilities.
The Residuals Handling Improvements Project is included in the City’s Capital Improvements Plan for the WWTP and will take two and a half years to complete. The project includes a number of major elements that include:
Demolition of existing equipment including dewatering plate and frame presses and biosolids incinerator
· Installation of centrifuges for biosolids dewatering and gravity belt thickeners to separately thicken secondary biosolids
· Rehabilitation of an existing gravity thickener for thickening primary biosolids and conversion of two existing gravity thickeners to covered tanks for blending thickened primary and secondary biosolids
· Rehabilitation and modification of the Solids Handling Building to accommodate new equipment, meet current building code requirements and to install a building addition for loading trucks with processed biosolids and receiving chemical deliveries
· Installation of a new boiler to service all facilities within the WWTP
· Installation of odor control equipment to reduce WWTP staff exposure and off-site nuisance odors from residuals handling equipment and facilities
· Replacement of antiquated 4.8 kV electrical system with a more efficient and maintainable 13.2 kV system
WWTP staff solicited public bids for the project as specified in ITB No. 3972. Five bids were received on November 24, 2008, as follows:
· Sorensen Gross Construction Services, LLC $42,444,927
· DeMaria Building Company $44,269,579
· Walsh Construction $44,938,202
· Granger Construction $45,864,621
· Spence Brothers $45,938,496
The project was awarded to Sorensen Gross Construction Services, L.L.C. on January 5, 2009 and notice to proceed was issued on February 27, 2009.
Greeley and Hansen's resident engineer and resident project representative are on-site full-time to provide construction support on behalf of the City. THe Contractor has obtained the building, soil erosion and sedimentation control and various trades permits from the Ann Arbor Charter Township. Representatives from Ann Arbor Charter Township visit the construction site on a regular basis.
Key construction progress includes:
- Demolition of portions of the existing building structure and process equipment within the Solids Handling Building, along with various environmental abatement activities, are continuing.
- Demolition of process equipment and structures at the gravity thickening facilities are continuing.
- Excavation, piping installation and backfilling in the vicinity of the gravity thickening facilities are ongoing.
- Demolition of two of the three Gravity Thickener mechanisms has been completed.
- The following major equipment has been delivered, is currently being installed and will be started up and tested in the next three months:
Dewatering centrifuges
Dewatered cake storage hoppers
Dewatered cake conveyors
Dewatered cake lime addition equipment (pugmills)
Polymer dilution units
Permanent liquid sludge loading arms
Blend Tank mixing and aeration system
Gravity Thickener mechanism
Sludge Holding Tank mixer drives
- The 20 ton monorail has been installed, started up, tested and utilized to bring equipment into the rehabilitated space.
- The structural (concrete) portions of the new Truck Loading Facility addition have been completed. Masonry work is ongoing.
- Installation of new piping in the Gravity Thickening Building basement is ongoing.
- Inside the Solids Handling Building, installation of sludge, plant effluent water, heating hot water, chemical, natural gas, odor control and drain piping and electrical conduit and wiring is ongoing.
- The boilers and associated piping and equipment has been installed.
- Masonry work for the new offices, control rooms and boiler room has been completed. In the next three months, masonry work for the stairs will be completed.
- Power has been transferred to the new unit substation.
- Installation of odor and HVAC ductwork within the Solids Handling Building is ongoing.
- Installation of the Gravity Belt Thickeners and associated chemical feed equipment has been completed.
Monthly progress meetings are held at the wastewater treatment plant with the City, Contractor, subcontractors and Engineer to discuss on-going and upcoming construction activities.
This improvement project will provide the City with up-to-date residuals handling facilities. In addition, the project will help the City of Ann Arbor achieve its goals for enhancing efficiency, reducing maintenance, and extending the viability of the WWTP to provide continued reliable, cost-effective wastewater treatment service to the community for the next 25 years.
For more information on this project, please contact
Mike Amicangelo at MAmicangelo@A2gov.org