Unit 2: Sewage Treatment Flashcards
What happens during primary treatment?
Solid waste material settles into a sludge layer.
What happens during secondary treatment?
Bacteria break down 85-90% of organic matter into carbon dioxide and inorganic nutrients like nitrogen and phosphorus. Also adds oxygen.
What happens during tertiary treatment?
Water is disinfected to remove pathogens and extra nitrogen and phosphorus.
What happens prior to treatment?
Sludge is placed in a landfill, burned, or turned to fertilizer and water goes to a river or lake.
Why add oxygen during secondary treatment?
Causes less odor because aerobic bacteria smell better than anaerobic bacteria.
What is done to sludge before discharge?
It is exposed to bacteria that digests it to remove pathogens, then water is removed to decrease volume and weight.
What is water disinfected with?
Chlorine, ozone, or ultraviolet light.
What did wastewater treatment plants recently have to start removing to avoid abundance of them in bodies of water?
Nitrogen and phosphorus.
When there is an abundance of rain, wastewater treatment plants are allowed to do what?
They become overwhelmed with water, so they are allowed to pump raw sewage into bodies of water. Often only happens at older facilities.
