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Welcome to the Greater |
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Wastewater leaves residences and other buildings through 4-inch and 6-inch diameter building sewers. The building sewers are owned by the property owner to the point of connection with the publicly owned sewer. Maintenance and repair of the building sewer is the responsibility of the individual property owner. The Sanitary District does have drawings of the location of many of the building sewers throughout the District. You may contact the District's Engineering Department at (309)637-3511 ext. 4844 about the availability of a particular drawing. |
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Building sewers empty into 6-inch and larger collector sewers. These sewers collect wastewater from within subdivisions and commercial developments and empty the wastewater into trunk sewers. The trunk sewers are generally larger in diameter and collect the wastewater from several service areas with the Sanitary District. The collector sewers and trunk sewers are publicly owned, either by the Sanitary District or the City of Peoria. The sewers owned by the Sanitary District serve Bartonville, Bellevue, Peoria, Peoria Heights, West Peoria and portions of unincorporated Peoria County. |
| The collector sewers are cleaned regularly using modern equipment like the Combination Vacuum/Flusher truck shown here. | 
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Wastewater from the
trunk sewers empties into two interceptor sewers owned by the Sanitary
District.
The Riverfront Interceptor parallels the Illinois River
and collects wastewater from the east side of
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| The collection system is designed to carry wastewater by gravity following the natural drainage patterns of the land. When gravity drainage is not possible pump stations are used to push the wastewater uphill through force mains to a point where gravity flow can again be used. The collection system has a total of 17 pump stations, 16 owned by the Sanitary District and 1 owned by the City of Peoria . | 
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All of the wastewater collected by the two
interceptor sewers flows to the District’s wastewater treatment plant
located on |
| Untreated wastewater, commonly called raw sewage, enters the Sanitary District’s wastewater treatment plant at the pretreatment building. | 
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After entering the pretreatment building, the raw sewage passes through mechanically cleaned bar screens. The screens are parallel stainless steel bars that remove large objects such as paper goods, rags, and sticks. |
| After it has been screened the wastewater flows into grit removal tanks. In these tanks the velocity of the wastewater is slowed to settle out sand, gravel, and coarse non-organic matter. All material removed by the bar screens and grit removal tanks is placed in a dumpster and then hauled to a sanitary landfill for final disposal. |  |
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Following grit removal, the wastewater must be pumped to a level to allow it to flow through the next treatment processes. Pumping is accomplished with two Archimedes screw pumps. Each pump has a capacity of 60 million gallons per day (mgd). Additional pumps are available when flows exceed 60 mgd. |
| The next treatment step removes about 50% to 60% of the solids suspended in the wastewater. The primary clarifier shown here is one of four used to remove these “suspended solids” and begin the process of removing organic pollutants from the wastewater. A clarifier is simply a large quiet tank that allows the light solids to settle to the bottom of the tank. The clarified water flows over the top of the tank and on to the next treatment process. The solids that settle to the bottom are removed and pumped to solids treatment. | 
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After settling in the primary clarifiers, about 50% of the organic pollutants remain in the wastewater. These pollutants are solids that are dissolved in the water (much like when sugar is dissolved in water) and they cannot be removed without additional treatment. This additional treatment is provided in the secondary aeration tanks. The treatment plant has twelve aeration tanks in which the wastewater is mixed by forced air. |
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The air and the mixing provide oxygen to microorganisms that occur naturally in the wastewater causing them to multiply at a rapid rate. These microorganisms feed on the organic pollutants and turn them into solids that will clump together. The photo shows some of these microorganisms magnified 20 times by the District’s phase contrast microscope.
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The pollutants are no longer dissolved, but are now in clumps that will quickly settle if put in calm conditions. These calm conditions are provided by eight secondary clarifiers where solids settle to the bottom and are pumped to solids treatment.
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| At this point the treatment plant has removed over 90% of the organic pollutants. However, further treatment is needed to meet the requirements for the removal of ammonia. Ammonia is treated using eighty-four rotating biological contactors. |  |
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This process also produces solids that must be removed. The solids settle to the bottom of two tertiary clarifiers and are pumped to solids treatment. |
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Solids removed from the wastewater are thickened using Gravity Belt Thickeners. These GBTs remove water from the solids before they are sent to the anaerobic digesters. The digesters are explained with the next photo. |
| Solids have been removed from the wastewater as part of three treatment processes. These “bio-solids” must receive further treatment before final disposal. This treatment is provided by four anaerobic digesters. The digesters heat the bio-solids to 95°F for about one month to stabilize the organic material. | 
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Following anaerobic digestion the bio-solids are dried with a centrifuge. The centrifuge works much like the spin cycle on a washing machine to remove water. |
| Much of the dried bio-solids produced by the treatment plant are used beneficially as fertilizer on local corn fields. The remaining bio-solids are used by landfills for daily cover. |  |
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Following the tertiary clarifiers, the now clean water flows through a channel on its way to the river. However, before the water is discharged to the river, chlorine is added to disinfect the water. Once it has been disinfected, sodium bisulfite is added to remove the chlorine. At this point the clear and clean water is released to the river at the outfall of the treatment plant. The plant has removed almost 95% of the inorganic solids, organic pollutants, and ammonia. |
| All of the water that is cleaned and then discharged to the river must meet the requirements of the Environmental Protection Agency (EPA). In order to make sure the cleaned water meets these requirements, and to monitor the treatment process throughout the plant, the District operates a fully equipped laboratory. The lab also works with our Industrial Surveillance Division to monitor industries, and other commercial operations, that are served by the District. On an average day 150 to 200 tests are performed as part of the lab operations. |  |
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The Greater Peoria Sanitary District is proud to do
our part to protect one of
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