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Wastewater – Its Journey to Treatment and Return to the Environment

Wastewater – Its Journey to Treatment and Return to the Environment . ESI. When you flush the toilet where does the contents go?. Where does it all go!. Where does the water from the washer go?. By gravity flow, the waste is on its way to your local wastewater treatment plant!.

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Wastewater – Its Journey to Treatment and Return to the Environment

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  1. Wastewater –Its Journey to Treatment and Return to the Environment ESI

  2. When you flush the toilet where does the contents go? Where does it all go! Where does the water from the washer go? By gravity flow, the waste is on its way to your local wastewater treatment plant!

  3. Why treat wastewater? • Causes a demand for dissolved oxygen (lower DO levels of streams) • Adds nutrients (nitrate and phosphate) to cause excessive growth • Increases suspended solids or sediments in streams (turbidity increase)

  4. Parkway WWTP Sewagesheds - an area where sewage is collected and delivered to a WWPT Bowie WWTP Western Branch WWTP Blue Plains WWTP Marlboro Meadows WWTP Piscataway WWTP Mattawoman WWTP approximate boundaries

  5. A B C D Where do you locate the WWTP in the watershed? Consider the four possible sites.

  6. The volume of wastewater PGC 1992 Comprehensive Ten Year Water and Sewerage Plan

  7. Levels of Treatment Primary • removal by physical separation of grit and large objects (material to landfill for disposal) Secondary • aerobic microbiological process (sludge) organic matter + O2 CO2 + NH3 + H2O NH3 NO3- • lowers suspended solids content (into sludge) Mostly dead microbes aquatic nutrient

  8. Secondary process To tertiary process From primary process Settling collects sludge on bottom air diffuser • Aeration and rapid mixing

  9. Levels of Treatment continued Tertiary (advanced) • anaerobic microbiological process with a different microbe where O2 is toxic (more sludge) NO3-  N2 (escapes to atmosphere) • PO4-3 if not removed in sludge in secondary process PO4-3 + Al+3 AlPO4 (s) (into sludge) - aeration to strip N2 and re-oxygenate (add DO)

  10. Tertiary process From secondary process add methanol as food source Effluent Settling collects sludge on bottom • Slow mixing • to keep suspended and O2 out

  11. When the treatment is done… • Effluent back to stream after • a final carbon filtration and • chlorination/dechlorination • Sludge – very nutrient rich • applied directly to land as fertilizer • incinerated (good fuel after drying) • composted (Compro® from WSSC) Note – Leafgro® is composted leaves and grass from MES

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