Wastewater Treatment Plant

Function

The ultimate purpose for the existence of the Portland Wastewater Treatment Plant (WWTP) is to protect the public and the environment from the harmful effects of raw sewage generated by those living and working in the City of Portland.  

This is accomplished by treating the raw wastewater to a degree that minimizes any harmful effect to the Grand River and allows the treated solids to be used as a fertilizer and soil conditioner on farmland.  The City is committed to bringing together the various resources necessary to accomplish this mission.

Collection System

Sewer mains collect the wastewater from homes, businesses and industries.  The City of Portland has 22 miles of mains located underground and with the help of 3 lift station the wastewater is conveyed to the WWTP.  The 3 lift stations and all Plant equipment are monitored by city staff and attached to SCADA monitoring call-out system.   

Currently (2025) the City of Portland is working to have the existing River Crossing sanitary sewer lines replaced.   This involves boring 3-6” HDPE sanitary lines underneath the Looking Glass River and 3-8” sanitary lines underneath the Grand River.  Four new manhole structures were added for ease of maintenance and to allow the new system to transition to the existing sanitary sewer footprint.  Once the new system is operational and proven the existing sanitary syphon will be decommissioned.

History

Portland built its first WWTP in 1958.  Prior to that, the sanitary sewage produced by the city was dumped directly into the Grand and Looking Glass Rivers.  The original facility was a primary treatment plant that provided 40-60 percent solids removal but very little suspended organic matter removal.  

The WWTP has had three upgrades since the original plant was built.  The first upgrade was in 1973, which added secondary biological treatment to effectively remove the suspended organic matter and remaining dissolved solids.  In 2012 the plant was again upgraded with improvements and redesign of the existing aeration tanks, grit removal, sludge thickening and final clarifiers.  

In 2023 the WWTP underwent its latest upgrade, this included the conversion from a traditional activated sludge plant to a MBBR (Moving Bed Bio-film Reactor), this is an attached growth treatment process where the microorganisms attach to the media and break down the organic material flowing through the tank.  The two digesters on-site also underwent a transformation, converting from anaerobic digestion (without free oxygen) to Aerobic Digestion (Available free oxygen).   Also included was a 500,000-gallon storage tank, upgraded raw influent pumps, upgraded fine screen for rag removal and an upgraded sludge thickener used to thicken and dewater solids.  The facility also updated the chemical feed and storage building.   The 900 building allows us to store and contain 6000 gallons of Ferric Chloride used to precipitate phosphorus in the waste stream and allows for equipment storage for the make-up air equipment and WWTP vehicles.  The WWTP currently removes an average of 95% solids, organic matter and Phosphorus.

Current Information

The WWTP currently treats an average flow of 350,000 gallons of wastewater each day.  The treated wastewater is discharged to the Grand River.  Sixty to Seventy dry tons of solids are removed each year and applied to farmland as a fertilizer and soil conditioner.  

The WWTP Department is responsible for all operations and maintenance of the WWTP and collections system.  The WWTP operates and maintains its own lab.  The City is required to sample raw influent and final effluent 3 times weekly, laboratory analysis is run on Total Suspended Solids and removal, BODS’S (Bio-carbonaceous Oxygen demand), Fecal coliform, Phosphorus, PH and D.O. (Dissolved Oxygen) and ammonia.

The WWTP staff consist of two operators and a superintendent.  The City operates under the Authority of EGLE (Environment, Great Lakes and Energy).   Every five years, the city is required to renew its NPDES (National Pollutant Discharge Elimination System) permit