How does wastewater work? Below are descriptions of the different steps in the processes that will be utilized at the Tomahawk Creek Wastewater Treatment facility from the beginning to safe water released into the environment. Each month another process will be added.

Overview

  1. Overflow Channel

  2. Influent Pump Station

  3. Peak Flow Pump Station

  4. Headworks

  5. Primary Clarifiers

  6. Biological Nutrient Removal

  7. Basin Blower Building and Chemical Feed

  8. Final Clarifiers
    (with Splitter Structure)

  

  9.  Final Sludge Pump Station

10.  Tertiary Pump Station

11.  Disk Filters

12.  Disinfection Basin

13.  PEW Pump Station

14.  Reclaimed Water Outfall

15.  Gravity Thickener

16.  Co-Thickening
       (Solids Processing Building)

  

17.  Dewatering
       (Solids Processing Building)

18.  Digesters and Biosolids

19.  Gas Flare

20.  Sidestream Treatment

21.  Electrical Substation

22.  Odor Control

23.  Administration Building

 

Overflow Channel

While not a part of wastewater treatment, the overflow channel is an integral part of the Tomahawk Creek site. The overflow channel provides a means for removing excess stormwater from rains or flooding. It prevents flooding of the Wastewater Facility while maintaining current flood levels upstream of the Facility.

The old Tomahawk Creek Wastewater site had areas that were below the 100 year flood elevation. In order meet regulations for the facility it must be fully protected from a 100-year flood event and remain operational during a 500-year event.

Flood protection will be achieved by raising the entire site above the 100-year elevation through placement of fill material. The effects of the additional fill will be countered by the creation of the Overflow Channel. The overflow channel will be utilized only when Indian Creek overflows its banks and will drain after the flood abates.

 

Influent Pump Station

The primary purpose of the Influent Pump Station is to receive raw wastewater from the collection system, remove large trash and debris, and lift the wastewater to the beginning of the treatment process. 

 

The Flow will enter the existing Influent Pump Station through the screenings area where three bar screens will keep the wastewater free of large trash and debris that could damage downstream equipment. After passing through the screens, wastewater will flow to the Dry Weather Pump Station. If flow increases due to wet weather conditions, the level in the wet well will rise until the water spills over two weirs into the Wet Weather Pump Station.

 

Flow from both pump stations is pumped to Headworks (#4) to begin the treatment process. 

Flow from the Wet Weather Pump Station can also be directed to the Filter Complex (#11) during wet weather events.

 

Peak Flow Pump Station

Due to spikes in flow during major storms, a Peak Flow Pump Station is needed to provide additional flow through the Facility.  This pump station will be engaged when flows exceed the capacity of the Influent Pump Station (#2). 

 

Excess flow enters the Peak Flow Pump Station by flowing over a set of weir gates.  Once in the pump station the wastewater flows through two multi-rake screens that will remove large debris and rags.  

After screening, the flow enters the wet well that contains four submersible pumps.  The diluted wastewater is pumped to the Filter Disinfection Complex (#11) to provide filtration and treatment along with the wastewater that has flowed through the main process.   

As a backup to the Influent Pump Station (#2) during normal flows, the Peak Flow Pump Station can also be directed to the Headworks Building (#4).

 

Headworks

Headworks of a wastewater treatment facility is the first stage in the treatment process.  It is designed to reduce the trash, rags, and grit in the influent (raw) wastewater to protect downstream equipment and processes.  
 

Flow will enter Headworks from the Influent Pump Station (#2). 
 

Three perforated plate fine screens will be capable of screening the dry weather peak flow. Solid waste materials (e.g. rags, wipes, solid waste, etc.) collected from each screen will be reduced in volume through washer-compactor units and taken to the landfill.
 

Two free vortex units will be used for grit removal. Grit is anything small that settles quickly and can cause damage to equipment downstream.  Examples are rocks, sand, egg shells, coffee grounds, etc.  The grit will be washed and taken to the landfill.    
 

Following grit removal, the main liquid flow will be sent to the next process: primary clarifiers (#5). 

 

Primary Clarifiers

A splitter structure located on the end of the Headworks Building (4) will direct screened and de-gritted wastewater to the three Primary Clarifiers.   

 

Wastewater enters the center of each basin and flows radially outward.  The clarifiers slow down the flow to allow solid particles to sink to the bottom, i.e. primary sludge, and grease to rise to the surface. During high flows, ferric chloride will be added to enhance settling.

 

The primary sludge and scum are pumped out of the clarifiers to the solids treatment train on the east side of the site for further treatment.

 

After primary solids removal, the clarified wastewater flows into the Biological Nutrient Removal (BNR) Basins (6) for secondary treatment.

© 2018 Johnson County Wastewater

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