Below the City of Missoula, there is a system of underground pipes that collect the water we use in our daily existence. This used water comes from sinks, drains, and toilets throughout the City. It contains a variety of organic and inorganic pollutants. As it leaves our homes and businesses, it becomes known as wastewater, which is treated in the City of Missoula's Wastewater Treatment Facility. After treatment, it is returned to the Clark Fork River where it can safely be reused.
About the Missoula Wastewater Treatment Facility
The Facility utilizes physical, biological, and chemical treatment methods to treat 6-9 million gallons of wastewater each day prior to reintroducing it to the Clark Fork River.
Purpose of the Facility
The Facility's purpose is to make the water as clean as it can possibly be before it is released back into the environment. This means that essentially all of the pollution must be removed. Pollutants come in many shapes and sizes, including objects as large as a basketball and things which were dissolved or too small to be seen by the marked eye.
As we remove pollutants, we are able to produce at least three beneficial products or results, which are treated water, biosolids that are made into compost, and methane gas that is used as fuel.
Methods to Remove Pollutants
Primary / Physical Treatment
The natural sinking process is called sedimentation. This process allows solids to accumulate on the bottom of the clarifier tanks where they can be removed in a concentrated form. These solids are mostly organic and ultimately become usable as fuel gas and/or compost.
In secondary treatment, microorganisms convert the remaining dissolved and suspended pollutants into forms that are more easily removed from the wastewater. One of the two biological systems uses aerobic or air-breathing organisms. These organisms use free oxygen to help break down the pollutants.
The other use anaerobic or non-air-breathing organisms. Anaerobic digestion is used to stabilize the sludge which is removed from the wastewater. These organisms convert some solids to methane gas, which is then used as fuel at the Facility. The biological systems, whether aerobic or anaerobic, are truly alive and are highly susceptible to changes in their environment.
Finally, the treated wastewater is disinfected using chlorine to kill disease-causing organisms. Other harmless chemicals are also sometimes utilized to enhance treatment.
History of the Facility
The facility began treating wastewater in 1962 utilizing only physical or primary treatment. In 1974, secondary treatment utilizing a biological process called activated sludge was added to further improve the quality of the treated wastewater. In 1982, a new solids handling facility, a new digester, and a new headworks building were constructed to further improve the treatment process.
Although Missoula has a very reasonable wastewater user rate, the city has continued to make substantial wastewater treatment improvements to provide the highest levels of pollution abatement possible.