Aerobic and On-Site Wastewater Treatment System Terms
If you are researching information about aerobic treatment systems, you may come across some unusual terms. This page was created to provide some definitions and descriptions for various on-site aerobic treatment system terms.
Terms Used to Describe A Treatment System
Some of these terms are used to describe all on-site systems including aerobic and septic.
Aerobic Septic System: This is actually an incorrect term since septic systems are not aerobic and aerobic systems are not septic. This term is used to describe a small scale on-site system similar to a septic tank except it uses an aerobic process versus an anaerobic process.
ATS: An acronym for “Aerobic Treatment System”
ATU: An acronym for “Aerobic Treatment Unit”
OSSF: An acronym for “On-site Sewage Facility”
OWTS: An acronym for “On-site Wastewater Treatment System”
Aerobic Treatment System Terms
Activated Carbon Filter: A filter that uses a bag of activated carbon to filter and remove odors from the air and gasses that emanate from the treatment process.
Aeration: The process of adding air to wastewater in order to increase the dissolved oxygen (DO) levels.
Aeration Chamber: The portion of the treatment system where air is added to the wastewater and the bugs consume the pollutants. The aeration chamber is located downstream of the pretreatment chamber and upstream of the clarifier chamber.
Aeration System: All of the equipment that is used to perform aeration in the treatment system including the air compressor units, air tubing/pipe and diffuser assemblies.
Air Compressor: The equipment above the ground that draws air in and delivers it to the diffusers through the tubes and pipes.
Baffle: A wall in a chamber that diverts or inhibits the flow or water in a particular direction.
Bugs: The microbes and bacteria that consume the pollutants in the raw wastewater or sewage. A septic treatment system uses anaerobic bugs. An aerobic treatment system uses aerobic bugs.
Bulkhead: A divider wall in the treatment tank that separates one chamber from the next.
Clarifier Chamber: The final chamber of the treatment tank where solids are settled out of the wastewater prior to exiting the treatment tank.
Clarification: The process of settling solids out of the wastewater. This is typically accomplished in a specially designed chamber or basin where the water’s flow velocity is slowed and no mixing is provided.
Crossover: Pipe that conveys water from one chamber or tank to another.
Diffuser: A fitting that allows compressed air to escape through small holes or slits. By forcing the air through the holes, the size of the bubbles is smaller and allows for more contact with the water. More contact with the water increases the amount of oxygen transferred to the water which increases dissolved oxygen.
Disinfection: Applying a chemical (chlorine) or using Ultraviolet radiation (UV) to kill pathogens in the effluent that comes out of the main treatment tank of a wastewater treatment system. In order to fully disinfect the effluent, there must be the proper dosage of chemical or UV and a long enough contact time for the disinfectant to kill all of the pathogens.
Effluent: The clear, treated water that exits the main treatment tank. Effluent is also used as a term to describe the water that exits a chamber.
Freeboard: The space between the waterline and the top of a chamber, basin or lagoon expressed in a linear measurement.
Influent: The raw sewage or wastewater that enters the main treatment tank. influent is also used as a term to describe the water that enters a chamber.
Inlet: The pipe that conveys water into a chamber or tank.
Laminar Flow: The natural mixing action created by the rising column of air above a diffuser. The water above the diffuser is pushed upward to the surface and then out to the side of the tank and then in a spinning motion under the surface. Laminar flow provides superior mixing at all depths in a chamber or basin.
Microbes: The bacteria that consume the pollutants in the raw wastewater or sewage. A septic treatment system uses anaerobic microbes. An aerobic treatment system uses aerobic microbes. Also called “Bugs”.
Mixing: The process of churning the contents of a chamber or basin. Mixing ensures that solids stay in suspension and the contents of the chamber or basin are uniform in dissolved oxygen, waste-strength and microbes.
NSF: An acronym for the National Standards Federation. NSF provides standards and evaluation for a variety of equipment and products, so consumers can be assured of their quality and performance.
Outlet: The pipe that conveys water out of a chamber or tank.
Pretreatment Chamber: A portion of the treatment system that separates solids from the raw wastewater prior to biological treatment.
Scum: The solids that float on the surface of the water or wastewater.
Setback: The distance from the opening of the treatment system to an adjacent property or structure. Most areas have minimum setback requirements from nearby structures and property.
Settling: The separation of solids from the wastewater using gravity.
Sludge or Activated Sludge: The solids produced by the natural biological treatment process. Activated sludge has an abundance of beneficial microbes (“bugs”) and is used to bolster the aerobic treatment process.
Solids: Anything that isn’t liquid that enters the treatment system. Solids can be trash or sludge.
V-Notch: A v-shaped opening usually found on one side of a weir. The v-notch provides a means of controlling flow into the weir and separating solids from the final effluent.
Waterline: The level of the surface of the water in a chamber or basin.
If you want an overview of what aerobic treatment systems are all about, see our On-site Aerobic Treatment Systems (ATS) page for more information.
To learn about our aerobic treatment system, the CWE-1500A, see our Onsite Aerobic Treatment System CWE-1500A page and our Onsite Aerobic Treatment System CWE-1500A Features page.