• Used water should not bewasted. We must clean it upby removing pollutants.
• Cleaning water is necessary toprevent large number of water-related diseases and even deaths.• Cleaning of water is a process ofremoving pollutants before itenters a water body or is reused.
Waste water treatment or“Sewage treatment”• Sewage is waste water released byhomes, industries, hospitals, offices and otherusers.• Sewage is a liquid waste. It has impuritiescalled contaminants.• Some of the contaminants are Humanfaeces, animalwaste, oil, urine, pesticides, bacteria andother microbes.
Wastewater is passed through barscreens to remove large objects likerags,cans,plastic packets etc.
Water then goes to a grit and sandremoval tank.The speed of the incoming wastewater is decreasedto allow sand, pebbles and grit to settle down.
• The water is then allowed tosettle in large tank which issloped towards the middle. Solidslike faeces settle at the bottom.• A skimmer removes the floatablesolids like oil and grease. Waterso cleared is called clarifiedwater.
• Air is pumped into the clarifiedwater to help aerobic bacteria togrow.• After several hours, thesuspended microbes settle at thebottom of the tank as activatedsludge. The water is thenremoved from the tank.
• The activated sludge is about 97% of water.The water is removed by sand drying beds ormachines.• The treated water has a very low level oforganic material and suspended matter. It isdischarged into sea , river or in ground.• Nature cleans it up further. Sometimes it maybe necessary to disinfect water with chemicalslike chlorine and ozone before releasing it intothe distribution system.
Better housekeeping practices• Do not throw cooking oil and fats down thedrain. Throw in the dustbin.• Chemicals like paints, solvents , insecticideskill microbes that help purify water. Do notthrow them down the drain.• Throw wastes like cotton, soft toys etc. in thebin as they choke the drains.