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Waste Water Treatment Flow chart v2

wastewater-treatment-plant-icon The Missouri River Treatment Plant receives wastewater from many factories and packing plants in Omaha. Many plants use water for cooling processes and cleaning floors and equipment. Some industries use a lot of water to process food, chemicals, leather, and packaging. Industrial and domestic flows give the plant an equivalent population of 600,000 people.

rain-cloud-icon In some areas of the city, sewers not only carry wastewater, but also convey storm water. Water from lawns and washing cars is also carried in combined sewers to the treatment facility. The wastewater and stormwater flow by gravity in large pipes underground until they reach lift stations along the Missouri River. The wastewater is then pumped to the plant to receive treatment.

house-iconIt is estimated that the Missouri River Treatment Plant serves 125,000 people in Omaha. Sinks, toilets, tubs, showers, and swimming pools all drain into the sewer system.

screening-iconAt the treatment facility, wastewater is first treated with a physical process called SCREENING. The water passes through screens that remove large material from the flow stream. Some examples of screened material include aluminum cans, plastic sacks, Styrofoam and paper cups, hair, grease balls, and rags. The screenings are collected in a lugger, allowed to dewater, and then transported to the landfill for disposal.

grit-removal-iconThe wastewater next flows into GRIT BASINS. This physical treatment process slows the velocity of water down enough to let heavy material settle out of the flow stream. Examples of material removed in a Grit Basin include sand, gravel, ash, cinder, eggshells, and coffee grounds. The grit is collected in a lugger and is washed to retrieve the reusable sand and gravel. The rest of the material is then trucked to the landfill for disposal.

primary-clarifierAfter the wastewater leaves the Grit Basin, the waste stream flows into large holding basins. These sedimentation tanks are called PRIMARY CLARIFIERS. The object of this physical treatment process is to settle out solids by using long detention times. The wastewater remains in the Clarifier for 1 1/2 to 2 hours. This lets sludge settle out of the water so only dissolved or soluble material is left in the stream. The sludge is pumped off of the bottom of the clarifiers to Anaerobic Digesters.

trickling-filter-iconAfter the wastewater has gone through the physical treatment process in Primary Treatment, it enters Secondary Treatment. The sewage is pumped up over a biological process called a TRICKLING FILTER. This biological tower is filled with plastic media. Organisms attach to the media and grow by taking up the soluble nutrients in the wastewater. These organisms convert the nutrients into more cell material. A portion of this material is flushed off the media by the water that is trickling past. That material is then transported to the next treatment process.

final-clarifier-iconSince the soluble material from the primary effluent was converted to solid cellular material, it can now be settled out of the flow. This physical process takes place in a FINAL CLARIFIER. The Final Clarifiers are large sedimentation basins similar to the Primary Clarifiers. They operate at detention times around 2 to 3 hours during average flow periods. The light sludge from this process is pumped to the Dissolved Air Flotation Unit for thickening. The wastewater flows to the Chlorine Contact Basin for the final leg of the treatment process.

chlorine-contact-basin-iconThe CHLORINE CONTACT BASIN is the final step before the treated wastewater is released into the Missouri River. During Disinfection season from May through September, Sodium Hypochlorite is added to disinfect the flow stream. This chemical process kills bacteria and pathogens. After 30 to 45 minutes of contact time, Sodium Bisulfite is added to remove any residual disinfectant and the treated water flows into the Missouri River.

anaerobic-digester-iconSludge that is collected in the Primary Clarifiers is pumped into an ANAEROBIC DIGESTER for further treatment. Thickened Final Clarifier sludge from the Dissolved Air Flotation Unit is also added. Anaerobic Digestion is a biological process that takes place in an oxygen free environment. Anaerobic organisms called acid formers convert solid material to basic acids. Methane formers then convert the acid into methane, water, and carbon dioxide.

energy-recovery-iconThe methane gas and carbon dioxide formed in the digestion process are used as fuel for engines in the ENERGY RECOVERY Building. The plant generates nearly 67 % of its annual electrical needs in this process. The waste heat from this process heats plant buildings and the digesters.

Dissolved Air Flotation Thickening IconThe DISSOLVED AIR FLOTATION THICKENER receives Final Clarifier sludge and scum and Solids Dewatering Building filtrate. The sludge is contacted with recycled water that is full of dissolved air. The air then leaves the water and attaches to solid particles in the sludge. The air and sludge rises to the top of the thickener and the float is pumped to the Anaerobic Digester for further treatment.

solids-dewatering-building-iconThe SOLIDS DEWATERING BUILDING uses a combination of physical and chemical treatment to form Sludge Cake. A chemical called Polymer is added to digested sludge to aid in the formation of floc. The sludge is then distributed to a Filter Press where the filtrate is pressed from the sludge. The Sludge Cake is then conveyed to trucks and distributed to farms for use as fertilizer.