Glossary

Michigan Environmental Education Curriculum
Wastewater Treatment

Adsorption

The process where chemicals in a gas or liquid are attracted to a solid, such as activated carbon, and held in a thin layer at the surface of the solid.

Advanced Waste Treatment

Basic wastewater treatment consists of the primary (settling) and secondary (biological) steps followed by disinfection. Advanced waste treatment (AWT) is any of various processes which would achieve greater removal of organic matter, nutrients, or solids.

Aeration Tank

The tank which holds the wastewater and microorganisms in the activated sludge process (secondary or biological treatment). Air is pumped into the tank to meet the oxygen needs of the microorganisms.

Aerobic

Oxygen is present.

Alum

A chemical, aluminum sulfate, added to drinking water to neutralize negative charges on particles so that they will clump together and settle more rapidly; also added to wastewater to remove phosphorus by precipitation.

Anaerobic

Oxygen is absent.

Bacteria

A group of microscopic organisms, shaped like commas, rods, spheres or spirals found almost everywhere in air, water, soil and plants and animals. Some bacteria cause disease, but most do not.

Biodegradable

Materials that can be broken down to simpler forms by bacteria and other organisms.

Biosolids

Wastewater sludge that has been treated to be safe for land application. Here, safety refers to the reduction or elimination of disease-causing organisms.

Chlorine

A chemical added to drinking water and wastewater to kill disease-causing organisms.

Collecting Sewer

A pipe or sewer that collects wastewater from several houses before being sent on to larger sewers.

Combined Sewer

A pipe or sewer that carries both wastewater and rainwater.

Combined Sewer Overflow

An opening in a combined sewer where a mixture of wastewater and rainwater can flow out of the sewer into a river or lake. During rainstorms, increased flows can fill up a combined sewer causing the flooding of basements with the wastewater-rainwater mixture if an overflow is not provided.

Contaminant

Something that makes water, for example, impure or unsuitable for a particular use.

Dewatering

Removal of water; used here to describe the removal of water to make treated wastewater sludge easier to handle.

Digester

The tank in which digestion of wastewater sludge takes place.

Digestion

The process in which wastewater sludge is broken down making it more stable or intert. A stable sludge will not further decompose, creating foul odors or using up oxygen.

Discharges

As used here, water flowing from a wastewater treatment plant to a river or lake.

Domestic

Originating from homes.

Drain Field

An area of gravel, often with sand below, that receives the outflow or drainage from a septic tank.

Effluent

The outflow from a wastewater treatment plant; influent is the inflow.

Fecal

Waste matter discharged from the intestines.

Groundwater

Water present below the ground in the pores between soil particles and cracks of rocks.

Incineration

Burning.

Inert

A substance that will not react; as used here, inert refers to organic matter in sludge that will not further decompose, consuming oxygen and creating foul odors.

Infiltration

Water that leaks into sewers through cracks in the pipe, pipe joints and manhole covers.

Interceptor Sewer

Pipes that join collector sewers with the wastewater treatment plant.

Lagoon

As used here, a pond employed for treating wastewater.

Legislation

Laws.

Municipal

Having to do with a town or city.

Organic

Substances containing carbon; coming from living things.

Pathogens

Disease-causing organisms.

Perforated

Having holes.

Primary Clarifier

A settling tank which removes solids in primary treatment; the water is clarified in this process.

Primary Sludge

The wastewater solids which collect in the bottom of the primary clarifier.

Protozoa

One-celled, animal-like organisms, many of which are capable of movement.

Return Activated Sludge

Activated sludge solids, collected in the secondary clarifier, that are returned to the aeration tank to keep enough microorganisms present there to treat the waste; compare to waste activated sludge.

Sanitary Sewer

A sewer pipe carrying only wastewater.

Secondary Clarifier

A settling tank which removes solids in secondary treatment; the water is clarified in this process.

Separate Sewers

A sewer system where wastewater and rainwater are carried in separate pipes; compare to combined sewers.

Septic Tank

A plastic or concerete tank used for onite (home) treatment of wastewater; the septic tank collects solids while liquids move on to a drain field where they are treated.

Sludge Cake

Wastewater solids, after treatment to remove water.

Standards

Limits placed on contaminant levels in drinking water to protect consumers and in treated wastewater to protect the public health and environment.

Tertiary Treatment

Any process following secondary treatment that removes more pollutants; essentially the same as advanced waste treatment.

Toxic

Poisonous.

Tributary

A stream that flows into another stream or a lake; the Detroit River is a tributary to Lake Erie.

Turbid

Cloudy.

Ultraviolet Light

An invisible form of light which can cause sunburn and which is effective in killing microorganisms.

Waste Activated Sludge

Activated sludge solids, collected in the secondary clarifier, that are not returned to the aeration tank, but are sent on for further treatment; compare to return activated sludge.

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