Sewage
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How is bacteria used in sewage treatment?
Produce a harmless product that can be safely returned to rivers and seas
What happens to raw sewage?
Stirred and aerated, adds oxygen to promote the growth of many types of bacteria
What does bacteria do?
Feeds on the sewage and breaks it down
What does a grit chamber do?
Removes grit from sewage
How does the grit chamber work?
Grit sinks to the bottom and can be removed
What does a screen do?
Removes large pieces of debris, (I.e paper)
How does the screen work?
Acts like a sieve
What is the sedimentation tank’s job?
Removing large particles from the sewage
How does the sedimentation tank work?
Particles settle at the bottom of the tank
What does the digestion tank do?
Sewage is broken down
How does the digestion tank work?
Sewage is digested by bacteria
What does the spray do
Water part of the sewage sprayed across the filter bed
How does the spray work?
Spreads watery sewage across the filter bed, allowing bacteria in the filter to break it down easier
What does the filter bed do?
Removes fine particles from the sewage
How does the filter bed work?
Fine particles trapped between the stones and gravel and is digested by the bacteria
What is bioremediation?
Technique using special micro-organisms to break up toxic waste into less/ non-toxic substances
Give examples of bioremediation (3)
Genetically modified bacteria to break down mercury and toluene, toxic chemicals found in nuclear waste Specific strains of fungus to break down nerve gases, VX & Darin Sewage treatment