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 plant’s existing treatment facilities. Finalized in 2004, the results of the study revealed that the plant’s existing residuals handling facilities, which process the residual solids from the wastewater, needed to be replaced. This aging equipment has exceeded its expected operating life and, as a result, operating efficiency is declining while operation and maintenance costs are increasing.
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 and water system design, has been retained by the City for the design of the improvements. The following tasks were performed during the design efforts:
- On-site visits to other WWTPs to evaluate their application and use of more efficient thickening, dewatering, stabilization, and off-loading equipment.
- Surveys of other WWTPs regarding actual equipment performance using a questionnaire as part of the on-site visits.
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On-site pilot testing of dewatering equipment at the Ann Arbor WWTP and evaluation of performance results to determine if the equipment meets design requirements.
- Plant-wide odor control study and preparation of a plant-wide odor control report. 
- Two public meetings with WWTP neighbors to discuss and address their concerns for odor and noise control.
- Design of new solids handling facilities including the addition of new equipment and rehabilitation of existing facilities.
The design of the Residuals Handling Improvements project includes the following major design elements:
- New odor control equipment to reduce off-site nuisance odors from the residuals handling equipment and facilities.
- Rehabilitation of an existing gravity thickener for thickening of primary sludge.
- New gravity belt thickeners to thicken waste activated sludge.
- Conversion of two existing gravity thickeners to Blend Tanks for blending of thickened primary and waste activated biosolids.
- New centrifuges for dewatering of biosolids.
- New lime stabilization equipment including two lime silos.
- Addition of a double truck bay to the existing Solids Handling Building to house the lime stabilization equipment, liquid biosolids truck loading equipment, dewatered cake storage and truck loading equipment and chemical unloading facilities.
- Rehabilitation and modification of existing Solids Handling Building to accommodate new equipment and meet current building code requirements.
- Removal of equipment to be replaced including the dewatering plate and frame presses and the incinerator.
The City is currently working with the Michigan Department of Environmental Quality and the Ann Arbor Charter Township to obtain necessary permits and approvals. Once all permits and approvals are obtained, the Residuals Handling Improvements project will be advertised for public bidding in the third quarter of 2008.
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 to 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