Glossary
Biosolids
The solid organic byproducts generated during sewage treatment, which can be processed and used as fertilizer.
Example:
Farmers sometimes use treated biosolids from wastewater treatment plants to enrich their soil, providing nutrients for crops.
Clean Water Act (CWA)
A federal law regulating pollutant discharge into U.S. surface waters, aiming to restore and maintain their chemical, physical, and biological integrity.
Example:
The Clean Water Act (CWA) mandates that industries obtain permits before discharging wastewater into rivers, helping to protect aquatic ecosystems.
Drainage field
An area of porous soil and gravel where effluent from a septic tank is discharged for further natural filtration and decomposition.
Example:
After leaving the septic tank, wastewater slowly percolates through the soil in the drainage field, where natural processes further purify it.
Effluent
The treated water that is discharged from a sewage treatment plant after undergoing various purification stages.
Example:
After tertiary treatment, the clear effluent from the wastewater plant was clean enough to be released into a local river without harming aquatic life.
Groundwater pollution
The contamination of underground water sources, such as aquifers, by pollutants making the water unsafe for use.
Example:
Leaking underground storage tanks can cause severe groundwater pollution, rendering nearby wells unusable for drinking.
Maximum Contaminant Levels (MCLs)
Legally enforceable standards set by the EPA under the Safe Drinking Water Act for the maximum amount of specific contaminants allowed in public drinking water.
Example:
If lead levels in drinking water exceed the established Maximum Contaminant Levels (MCLs), water utilities must take action to reduce exposure.
National Pollutant Discharge Elimination System (NPDES)
A permit program established by the Clean Water Act that regulates point sources of pollution by requiring permits for discharges into U.S. waters.
Example:
A factory must apply for an NPDES permit to legally discharge its treated wastewater into a local stream, ensuring compliance with environmental standards.
Nonpoint sources of pollution
Diffuse and widespread sources of pollution that are difficult to trace to a single origin, often resulting from runoff over a large area.
Example:
Agricultural runoff carrying fertilizers and pesticides into a nearby lake, spread across many farms, is a common nonpoint source of pollution.
Point sources of pollution
Identifiable and localized sources of pollution that discharge contaminants from a specific location, such as a pipe or ditch.
Example:
A factory's discharge pipe releasing wastewater directly into a river is a classic example of a point source of pollution.
Primary Treatment
The initial physical stage of sewage treatment that removes large objects and heavy particles from wastewater through screening and sedimentation.
Example:
During Primary Treatment, large debris like rags and plastic bottles are filtered out, and sand settles to the bottom of tanks.
Safe Drinking Water Act (SDWA)
A federal law protecting public health by regulating public drinking water supplies and setting national standards for drinking water quality.
Example:
Under the Safe Drinking Water Act (SDWA), municipal water providers must regularly test tap water for contaminants to ensure it meets safety standards.
Secondary Treatment
The biological stage of sewage treatment where microorganisms break down dissolved organic matter in aerated tanks.
Example:
In Secondary Treatment, beneficial bacteria consume organic pollutants, turning murky wastewater into clearer liquid.
Septic tank
An underground, on-site wastewater treatment system used for individual properties not connected to a central sewer system.
Example:
Many rural homes rely on a septic tank system to manage their household wastewater, separating solids and liquids underground.
Sewage treatment
The process of cleaning wastewater to remove pollutants and pathogens before it is returned to the environment or reused.
Example:
A large municipal sewage treatment plant processes millions of gallons of wastewater daily, transforming it from a health hazard into water safe for discharge.
Sludge
The solid waste that settles at the bottom of a septic tank or sedimentation tanks in a sewage treatment plant.
Example:
Regular pumping is necessary to remove the accumulated sludge from the bottom of a septic tank, preventing system backups.
Tertiary Treatment
The advanced final stage of sewage treatment that removes remaining pollutants, nutrients, and pathogens through processes like filtration and disinfection.
Example:
To make water suitable for irrigation or even indirect potable reuse, Tertiary Treatment often involves UV light disinfection.