Process and Operations

The Wastewater Treatment Plant (WWTP) is located at 15 Ninth Street on the shore of Manistee Lake. The plant currently treats approximately 350 million gallons of wastewater each year from the City of Manistee and surrounding areas. Wastewater is conveyed to the plant by 13 lift stations and approximately 120 miles of sewer mains. The treated effluent ultimately discharges into Manistee Lake.

The WWTP is operated and maintained by four operators under the supervision of the Department of Public Works director. The operators are licensed with the Michigan Department of Environmental Quality for wastewater treatment.


Requests for service, including blockage evaluation and new service consultation, should be directed to the Sewer Service Department at (231) 723-7132.


Questions about your bill, transferring an account, establishing a new account, rental account information and payment options should be directed to the Utility Billing Department at (231) 723-2559.

We offer two ways to electronically process water and sewer payments. The most convenient is through the use of an auto-draft feature. You provide us with your financial information, and your monthly bill is automatically deducted from your account. No more missed payments! This is especially useful for seasonal residents and anyone else who wants one less thing to remember. To sign up, please return the auto debit enrollment form to City Hall.

The second method for paying is by credit card by using our online bill feature. Simply look up your bill online and make payment via credit card. Transaction and convenience fees apply. Make payments here.

About Our Treatment

Primary Treatment

Wastewater enters the treatment plant and is immediately screened through a mechanical bar-rake to remove large pieces of debris, then it travels through a Parshall Flume and flow-rate data is recorded. Water is then pumped up and through a Pista grit removal system where sand and other inorganic materials are removed. Wastewater then passes through two 100,000-gallon primary clarifiers where sludge settles to the bottom and is pumped to the anaerobic digesters. The water then travels to the Intermediate Pump Station.

Secondary Treatment

Wastewater is pumped through the Intermediate Pump Station up to an elevated tank. This first tank is designed to operate in an anaerobic environment. Wastewater then travels through a series of three aerated activated sludge tanks where biological treatment takes place. From the aeration tanks the water enters the secondary clarifiers where the activated sludge settles to the bottom and is returned via pumps to the anaerobic tank. The treated water then travels through the ultraviolet disinfection system and is discharged into Manistee Lake.

Biological Phosphorus Removal

The plant expansion in 2007 enabled new pathways for secondary treatment. One feature added was the ability to remove phosphorus biologically. When the wastewater enters the anaerobic zone in the treatment process it is mixed with the oxygen-depleted return-activated sludge. No oxygen is added in this zone, essentially starving the bacteria of oxygen. When the wastewater / activated sludge mixed-liquor travels to the second tank it is hit with a large supply of dissolved oxygen. In this zone a luxury uptake occurs, enabling the bacteria to store phosphorus and be wasted out of the system.



When wastewater enters the primary clarifiers the solids settle to the bottom. Those solids are then pumped to two heated and mixed anaerobic sludge digesters. As more sludge is pumped into the digesters the supernatant travels to a 500,000-gallon storage digester. The storage digester has a floating steel cover and floats on pressurized methane gas generated by the sludge digestion process. When the storage digester is full its supernatant is returned to the headworks of the treatment system and it runs back through the treatment cycle.

When the supernatant is no longer dilute enough to be treated, digested sludge is then pumped to a 250,000-gallon biosolids storage tank until it can be land applied. The Wastewater Treatment Plant (WWTP) contracts a residuals management company to haul and land apply sludge twice a year, once in the spring and once in the fall. The WWTP land applies approximately 1.2 million gallons of digested sludge each year.


The WWTP has an updated computerized SCADA (Supervisory Control and Data Acquisition) system that monitors and controls many of the plant processes. This system is also capable of monitoring lift stations throughout the city. Through use of a SCADA system the WWTP is able to monitor data and plant operations with limited personnel.

Lift Stations

The City of Manistee has 13 lift stations located throughout the city that convey wastewater through the sewer system to the treatment plant. The high-volume stations are equipped with equipment to remotely operate the system and convey data to the plant SCADA system.


The history for the treatment process began when the original wastewater treatment plant (WWTP) was constructed in 1938 as part of President Franklin D. Roosevelt’s Public Works Administration Program.

The primary treatment process was upgraded in 1988 (Phase I) by making improvements to the primary clarifiers and sludge digesters. Phase II and III were implemented in 1989 and 1990, upgrading the WWTP to a secondary treatment facility. During these phases an activated sludge process was added in addition to secondary settling and an anaerobic sludge storage digester. At this time the disinfection process was converted from chlorination to ultraviolet disinfection.


In 2007 the WWTP expanded once again. As part of this expansion, two 100,000-gallon elevated activated sludge aeration tanks, an intermediate pump station, a vehicle / generator garage and a 250,000-gallon biosolids tank were added. This expansion opened new pathways for flexible plant operation. The plant was then equipped to run in the following modes of secondary treatment: plug flow, step feed and extended aeration. The WWTP was also equipped with the capability to remove phosphorus biologically.

For more historical information about the City of Manistee WWTP visit:
Manistee County Historical Museum
425 River St.
Manistee, MI 49660

Useful Documents

After reviewing the Executive Summary, if you have further questions the entire document can be reviewed at City Hall, 70 Maple St. Manistee, MI  49660.

After reviewing the Executive Summary, if you have further questions the entire document can be reviewed at City Hall, 70 Maple St. Manistee, MI  49660.