Sewage treatment

Raw sewage

Gray, fowl smelling, syrupy liquid that made of total ,I tire collected from all drains
99.9% water

Debris/grits

Any non organic matter floating
Sand/gravel

Particulate organic matter

Fecal matter, food waste, toilet paper

Colloidal and dissolved organic matter

Not visible
Ex: urine, bacteria

Dissolved inorganic matter

Phosphate/nitrates

Preliminary treatment

Debris is removed
Raw sewage moves through bar screens

Primary treatment

30-50% clean
Water from grit chamber flows through large tank

secondary treatment

70-90% clean
BOD
Bacteria decompose organic matter into CO2 and sludge with aeration.

oxygen systems

trickling filter system
activated sludge system

trickling filter system

uses a bed of crushed stone
primary treatment wastewater is sprayed over it to increase dissolved oxygen

activated sludge system

a portion of the sludge is cycled back to where waste water begins secondary treatment
(complex to operate and high power consumption)

Final Cleansing and Disinfection

use of Clorox (sodium hypochlorite) to kill any remaining pathogenic organisms.
You can also use UV light

byproduct of Anaerobic digestion of sludge

treated sludge = solid organic material that's been removed from sewage and treated so its non hazardous

Biochemical Oxygen Demand (BOD)

amount of oxygen that'll be absorbed as wastes are being digest by decomposers/detritus