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.
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
(Solids Processing Building)
(Solids Processing Building)
18. Digesters and Biosolids
19. Gas Flare
20. Sidestream Treatment
21. Electrical Substation
22. Odor Control
23. Administration Building
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 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).
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.
Biological Nutrient Removal (BNR)
Biological Nutrient Removal (BNR) is a secondary treatment technique that uses bacteria to break down and reduce the biological components of wastewater. BNR reduces the concentrations of organic matter, ammonia, nitrogen, and phosphorus.
The BNR basins provide the right conditions for the bacteria. The basins are split into different zones that will vary in oxygen concentration, nutrients, and recycle flows to provide the desired responses from the bacteria.
There are four BNR basin trains that include mixers, recycle pumps, and air diffusers. The BNR basins work together with the Final Clarifiers (8) to provide secondary treatment.
Basin Blower Building (BBB) and Chemical Feed
The Basin Blower Building (BBB) houses five blowers that supply air to the Biological Nutrient Removal (BNR) basins (6).
Air is extremely important to the BNR process. The bacteria in the oxic zones need air to reduce organic pollutants and convert ammonia into nitrate.
Blowers typically account for 40%-60% of the energy demand at a WWTF. These blowers are high efficiency gearless turbo blowers and will help control electricity costs.
Carbon supplement chemical tanks are also located at the BBB. Carbon supplement may be fed at each anaerobic zone and post-anoxic zone in the BNR to help stabilize nutrient removal.