Studied by 9 people
APES 2024
Biochemical oxygen demand (BOD)
The amount of oxygen a quantity of water uses over a period of time at specific temperatures
Dead zone
In a body of water, an area with extremely low oxygen concentration and very little life
• Caused by increased nutrient pollution
Low oxygen concentration can be deadly to many organisms such as
fish, plants and shellfish
Positive feedback loop
as more organisms die, more microbes come in
and use up more oxygen
BOD of a natural water is usually around
5 to 20 mg of oxygen and wastewater could be 200 mg of oxygen
Biological Oxygen Demand
When organic matter enters a body of water microbes that are decomposers feed on it
• The microbes require oxygen to decompose the waste
• The decomposition leads to more waste and more microbes
Safe Drinking Water Act (SDWA)
federal law that protects public drinking water supplies throughout the nation
Under the SDWA, EPA sets standards for
drinking water quality and with its partners implements various technical and financial programs to ensure drinking water safety
Clean Water Act
started pollution control programs such as setting
wastewater standards for industry
Due to the clean water act the EPA devoloped
national water quality criteria recommendations for
pollutants in surface waters
The clean water act made it unlawful to
discharge any pollutant from a point source into
navigable waters, unless a permit was obtained
Treating wastewater properly reduces the risk of
waterborne pathogens
Two common ways to handle human wastewater
Septic systems
Sewage treatment plants
Septic system
A relatively small and simple sewage treatment system, made up of a septic tank and a leach field, often used for homes in rural areas
Septic tank
A large container that receives wastewater from a house as part of a septic system
Sludge
Solid waste material from wastewater
Septage
A layer of fairly clear water found in the middle of a septic tank
Leach field
A component of a septic system, made up of underground pipes laid out below the surface of the ground
Primary treatment
physical removal of large objects, often through the use of screens and grates followed by the settling of solid waste in the bottom of a tank
Secondary treatment
biological process in which bacteria break down organic matter into carbon dioxide and inorganic sludge which settles in the bottom of the tank
During secondary treatment the tank is aerated to increase
the rate at which the bacteria break down organic matter
Tertiary treatment
use of ecological or chemical processes to remove any pollutants left after primary and secondary treatment
During tertiary treatment before water is discharged, the treated water is exposed to
one or more disinfectants (usually chlorine, ozone, or UV light) to kill bacteria
Note 
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