Sewage Treatment (College Board AP® Environmental Science): Flashcards
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Define sewage treatment.
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Cards in this collection (15)
Define sewage treatment.
Sewage treatment is the process of removing harmful substances from wastewater so it can be safely returned to the environment.
What is the purpose of primary sewage treatment?
Primary treatment removes large solid materials and some suspended solids.
During , large objects like sticks and plastic are filtered out of wastewater using metal bars.
During screening, large objects like sticks and plastic are filtered out of wastewater using metal bars.
What does a comminutor do in primary treatment?
A comminutor grinds up remaining large solids to prevent pipe blockages.
What forms sludge in the primary clarifier?
In the sedimentation tanks, smaller suspended solid particles settle at the bottom as sludge.
Which materials are removed by skimming?
Skimming removes floating materials such as grease and oil from the surface.
True or False?
Primary sewage treatment uses bacteria to remove dissolved pollutants.
False.
Primary treatment physically separates solid pollutants; it is secondary treatment that uses biological processes to remove dissolved pollutants.
Why is oxygen pumped into wastewater during secondary treatment?
Aeration encourages bacteria to break down organic pollutants such as human waste and food.
Define activated sludge.
Activated sludge is sludge containing aerobic bacteria that decompose organic matter; part of it is reused in the aeration tank.
What may water still contain after secondary treatment?
The water may still contain nutrients (such as nitrates and phosphates) and pathogens.
Why are nitrates and phosphates removed in tertiary treatment?
Nitrates and phosphates are removed because they can cause eutrophication if released into water bodies.
Tertiary treatment uses chemical to remove excess nitrogen and phosphorus.
Tertiary treatment uses chemical precipitation to remove excess nitrogen and phosphorus.
Name two materials used to filter water in tertiary treatment.
Water may be filtered through sand or activated carbon to remove final impurities.
Which disinfectants are used in final sewage treatment?
Chlorine, ozone, or ultraviolet (UV) light is used to kill any remaining bacteria.
True or False?
Disinfection is the first stage of sewage treatment.
False.
Disinfection is the final stage, carried out just before the treated water is discharged into rivers or lakes or reused.
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