Sewage Treatment

Why is treating sewage important? What is eutrophication?

• prevents the spread of diseases

• eutrophication = too many nutrients dumped form sewage = algae grow out of control and consume all the oxygen, fishes die .

What happens during the primary treatment? What is sludge?

• getting rid of large solids

• Sludge = large stuff that settles

What happens during secondary treatment?

• Remove biological material

• Stater cultures of activated sludge are sued to start new tanks

• Bacteria aerobically consume most of the remaining BOD

What happens after secondary treatment? Is water ready to be released? 

• If released into water supply , chlorination only 

• If reused as drinking water, additional steps: 

  • membrane filter 

  • ozone treatment 

What is tertiary treatment? 

additional removal of BOD in man-made lagoons or wetlands. 

What is sludge digestion? Is it aerobic or anaerobic? What done with the final, treated sludge?

• sludge is collected in anaerobic sludge digesters

• methane gas produced

• stabilized sludge is disposed of in landfills

Describe what happens in a septic tank and in leaching fields.

• Septic tank: form the house wastewater goes in, solid settle to the bottom ,fats and oils rise to the top, and bacteria breaks down the waste

• Leaching fields: the water then leaves the tanks, spreads through the pips in the ground and into the soil where water will filter naturall.

Why is flushing bactericidal chemicals like bleach down the toilet a potentially bad idea?

• Because bleach can kill the helpful bacteria in the septic tank, which slows down waste breakdown and can cause clogs or system damage.