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Have you ever wondered what happens to the water you use after it leaves your home?   Or what that piece of plastic or clay pipe sticking up out of your yard is? 

That is a  clean out.  The clean out is an inspection port attached to your (private) building sewer. The water enters your building sewer and then travels to the city sewer. This is where the wastewater treatment process begins.   

  City Sanitary and Combined sewer 
The Collection System
Your building sewer enters the city sewer known as the collection system. The collection system is an elaborate system of pipes and pumping stations which the city owns. Below are a few pictures of what the collection system looks like.

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The photo on the right is the North Street sewer.  The North Street sewer is more than a hundred years old and is the oldest sewer in Pontiac .  The photo to the left is the Henry Street inceptor sewer.  The Henry Street sewer handles the combined sewers for the entire south side of Pontiac . Another part of the collection system is the pumping stations.  We have 6 pump stations throughout the City of Pontiac.  The photos below are two of our pump stations.  The Fairway View pump station control building (below left) was recently constructed and upgraded to provide stand -by power and a new electrical control system.

  
The photo on the right shows the West View pump station which was also recently upgraded with new pumps, electrical controls and a force main.  We utilize pump stations because some parts of Pontiac are too low to allow the wastewater to flow by gravity to the wastewater plant.  So, after the wastewater travels through miles of pipes and 6 lift stations, it finally arrives at the wastewater treatment plant.  

  The Wastewater Treatment Plant 
 The purpose of the wastewater treatment plant is to utilize biological processes to recycle and treat water so it can be safely returned to the river.  The water that we recycle consists of residential, industrial and storm runoff. 

   
The reason we recycle the water is to protect public health and improve water quality.  Our plant was designed as a 3.5 MGD (million gallons per day) facility, which can process up to 10 MGD during peak storm events.

 
We use a very elaborate monitoring system to monitor the wastewater processes.  Chart recorders (below right) monitor pumping and other processes throughout the plant.  We also have a very strict permit from the Illinois EPA (Environmental Protection Agency). We have an environmental laboratory (above left) at the plant where operators perform many different analytical tests. Or NPDES (National Pollution Discharge Elimination System) permit regulates parameters the EPA has established for the Vermillion River watershed.  In addition to City of Pontiac laboratory we also perform laboratory analysis for 12 other treatment permitted systems.

  Primary Pumping
Now that the water has arrived at the wastewater treatment plant it enters our first process known as primary pumping.  The water flows into an influent wet well.  The wet well shown here on the left is wet well # 1 -  there are only two influent wet wells.  From here the water gets pumped into the various tanks throughout the plant.  We have many different types of pumps here at the plant.   

 Aerations
The aerations tanks are a part of the activated sludge process and it is a complex system of air, bacteria, return sludge, microorganisms and incoming wastewater from the trickling filters.  In this aeration process we use blowers with 100 horsepower motors that turn at 3500 RPM (below right) to add large amounts of air to a mixture of wastewater, bacteria and other microorganisms (below left). 

   
Oxygen in the air speeds the growth of helpful microorganisms, which consumes harmful organic matter in the wastewater.  The water now flows to the secondary sedimentation tanks.

 Secondary Sedimentation
Secondary Sedimentation is a process used to hold the water from the aerations for a period of time, during which the heavier solids settle to the bottom.  The solids that settle out are known as “activated sludge”.

 
These solids are vacuumed up and mixed with the incoming water from the trickling filters ahead of the aeration tanks. The crystal clear water that is separated from the solid matter flows over a weir (above right) and is sent to the junction chamber.

 Junction Chamber
A turbidity meter (below right) monitors and records the purity of the water as it is prepared for disinfection and chlorine removal and is moved along to the final phase of treatment.

 
Another thing that occurs at the junction chamber is, we allow some of the water to flow to a storage tank.  The water is so clean (above left), we use it to clean other tanks and even water trees.

 Disinfection
In the summer months the City is required to disinfect the water and then remove any residual amounts of chlorine. This is done because the chlorine is harmful to the fish that have to repopulate the Vermillion River downstream from the plant.

 If the river is at or near flood stage we have to pump the plant effluent over a flood wall that was constructed to protect the plant from floods.

Returning the water to the Vermillion River

The photos below show the plant effluent being returned to the beautiful Vermillion River.  Millions and billions of gallons of water have been processed over the past several years in a system that will be repeated many times between Pontiac and the Gulf of Mexico. Each day Illinois American Water Company withdraws water from above the Mill Street dam in Pontiac . They clean and treat the water to an award winning quality.

    
Some of this river water is not processed immediately but is pumped to large storage areas North of Pontiac. As needed the water is then cleaned and distributed to local residents, businesses and most importantly local industry. This water is then returned to the Pontiac treatment facility to be recycled and is returned to the river cleaner and better than before it was withdrawn from the river.