Wastewater

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Wastewater Its Journey to Treatment and Return
to the Environment

• ESI
• BY-Sanni Kumar Sinha
• B.Tech(c.s.) 1st year

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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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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)

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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
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Where do you locate the WWTP in the watershed?
Consider the four possible sites.
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The volume of wastewater
PGC 1992 Comprehensive Ten Year Water and
Sewerage Plan
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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
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Secondary process
To tertiary process
From primary process
Settling collects sludge on bottom
Aeration and rapid mixing
air diffuser
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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 Al3 ? AlPO4 (s) (into sludge)
• - aeration to strip N2 and re-oxygenate (add DO)

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