Treatment of Waste Water (Sewage)

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   aerated      denitrification      filtration      Nitrogen      organic      phosphates      screen      sediments      water   
Primary treatment involves filtering out as much of the solid waste as possible through a .
The water is then let then sit in a number of ponds or pools where the in the water can settle to the bottom.
About half of the solid waste, bacteria and material can be removed in this way.
In the secondary stage of treatment, use is made of tanks where bacteria can consume much of the remaining organic matter and nutrients in the water.
By now, about 90 percent of the waste in the has been removed.
Tertiary treatment removes nitrates and .
Aluminium sulfate is added which causes the phosphates to precipitate out, and they are then removed by .
Nitrogen is removed by , the reduction of nitrate to nitrogen gas.
gas is released to the atmosphere and thus removed from the water.