City of Fairfield, Ohio
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City of Fairfield, Ohio
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The City of Fairfield's Wastewater Treatment Process

The City of Fairfield Wastewater Treatment Facility treats an average daily flow of 5.5 million gallons of raw sewage a day with a  permitted capacity to treat up to 10 million gallons a day. Raw sewage travels through the City's collection system consisting of over 175 miles of sewer pipe before reaching the treatment facility. Below is a simplified explanation of the treatment process.

 

After traveling though the City's collection system, raw sewage enters the facility's headworks. Pictured above is the facility's primary wet well #1. The incoming sewer pipe is 42 inches in diameter with an attached sluice gate which can be used to isolate the wet well.

 

After entering the headworks, raw sewage flows through the facility's Channel Grinder, eliminating the need of a manual bar screen. The grinder reduces debris into a particle size approximately 1/4 inch in diameter which is acceptable for the facility's raw sewage pumps. Check out how the JWC Channel Monster works.

 

Centrifugal pumps are used to lift the influent raw sewage 50 feet to the beginning of the treatment process.

 

The first step in the treatment process is screening, a process to remove inorganic material. The mechanical bar screen removes debris larger then 6mm in diameter. Debris captured by the screen is dropped into a hopper where a hydraulic press forces the material through a cylinder removing excess water. The dewatered material is extruded into a dumpster for removal to the local landfill.

  

After screening and before raw sewage can move on to Primary Sedimentation, it must go through grit removal. Grit consists of sand, gravel, cinder, eggshells, and other inorganic matter and must be removed to protect down stream equipment. The facility utilizes a chain and bucket style grit collector. In a 60X7 foot aerated channel the flow of raw wastewater is slowed down to a speed of 1.7 feet per second allowing the inorganic matter to settle. Buckets connected to chains scrape across the bottom of this channel collecting the grit and dumping it into a shoot where a screw conveyor deposits it in a dumpster. The dumpster contents are taken to a local landfill.

 

After grit removal, raw sewage is ready for Primary Sedimentation. The sedimentation tanks are designed to give the wastewater flow the proper detention time for organic solids to settle. Scrapers present in the tank move continuously along the floor of the tank to deposit the raw sludge in hoppers for removal. The scum which floats to the surface is skimmed by the scrapers to a collection bin for subsequent removal.

 

After Primary Sedimentation, Raw Sludge is pumped twice daily to the Anaerobic Digesters. For an overview of the Treatment Facility's Solids Handling process, click on this link.

 

The treatment facility utilizes the Activated Sludge process. A process where by a population of microorganisms, in an aerated aquatic environment, break down organic matter. The microorganisms are introduced to a food source (the plant's primary effluent), supplied with the proper dosage of dissolved oxygen, and given a detention time sufficient to complete the process, there by creating an acceptable quality effluent. The microorganisms reproduce during this process requiring a percentage of the biological population to be wasted on a daily basis in order to maintain a proper food to microorganism ratio. The wasted microorganisms are sent to the plant's solids handling process.

 

The facility's state of the art single-stage centrifugal blower supplies the proper dosage of dissolved oxygen (air) to the plant's activated sludge process. The unit was built in the Netherlands and is the most energy efficient blower on the market today.  

 

 

Secondary Clarifiers are used in the Activated Sludge process to create a quiescent environment. The microorganisms come together and form "flocs" which settle to the bottom of the clarifier releasing clean wastewater known as secondary effluent. This process is known as flocculation and sedimentation. 

 

Centrifugal pumps are used to return a population of microorganisms to the beginning of the activated sludge process, and "waste" the rest to the facility's solids handling process.

 

Before the secondary effluent can be discharged to the Great Miami River, it must be disinfected to protect the river from pathogenic organisms. The facility utilizes Ultraviolet Light Disinfection. Ultraviolet light disinfects secondary effluent by penetrating the cell wall of pathogenic organisms, affecting their DNA, and destroying their ability to reproduce. Each of the plant's two UV trains have the capability of producing the proper intensity with the correct contact time to treat 7.5 million gallons of secondary effluent a day.

 

After disinfection the primary effluent flows through the facility's outfall located adjacent to the Great Miami River. The outfall is permitted by the Ohio EPA under permit #1PD00003*PD

 

The City of Fairfield Wastewater Treatment Facility's primary effluent meets or exceeds all parameters set by the Ohio EPA and is discharged safely to the Great Miami River.