Sewage Treatment

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Traditional Aboriginal Knowledge

Sewage Treatment

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Methods of treating sewage
Sources of Household sewage
Composition of Household Wastewater
Septic Tank System

adapted to HTML from lecture notes of Prof. Stephen A. Nelson Tulane University

Methods of treating sewage

Household sewage is comes from a variety of sources.

Sources of Household sewage

Toilets 40%
Bathing 30%
Laundry 15%
Kitchen 10%
Miscellaneous 5%

Excluding about 1% solids, household sewage is 99.9% water.

Composition of Household Wastewater

Constituent Materials Concentrations (ppm)
Dissolved Solids 500
Suspended Solids 200
Settleable Solids (1%)
Biochemical Oxygen Demand
(BOD) material
Chemical Oxygen Demand
(COD) material
Nitrogen 40
Organic 15
Free Amonia 25
Nitrite 0
Nitrate 0
Phophorus 10
Organic 3
Inorganic 7
Chloride 50
Alkalines 100
Grease 100

Septic Tank System

In many areas the main type of sewage disposal is a septic tank system.


In the diagram, sewage travels to a leaching field after it goes through the septic tank. This is needed in places where they do not have good drainage.
Sandy sediments are necessary in order to oxidize the sewage water, and filter out the bacteria from it.
Ammonium that travels through the unsaturated zone is oxidized and converted to nitrate by the time it reaches the water table. Thus, areas with high populations that rely on septic tank systems have to be concerned about the possibility of the groundwater achieving high nitrate concentrations.