Wastewater Treatment Glossary: A Comprehensive Guide to Terms

Wastewater Treatment Glossary: A Comprehensive Guide to Terms

Posted on 15 Jul 2022 by Lise Helluy

Wastewater treatment is the process of removing contaminants from wastewater, which is any water that has been used or contaminated in some way. The wastewater may come from homes, businesses, industries, or municipalities. In order to ensure that wastewater is treated properly and does not cause harm to people or the environment, it is important to understand the terminology associated with this process. In this blog post, we will define key wastewater treatment terms and explain their meanings.


Activated sludge process: This uses biological purification in the treatment of wastewater. It is a method of purification by free cultures.

Aerobic: An organism that grows in the air.

Anaerobic: An organism growing in a place without oxygen.

Approved system: A system is said to be approved when it is certified by the Ministry of the Environment and Health. 


Blackwater: Water containing fecal matter, fibrous residues, and particles.

BOD5 (Biochemical Oxygen Demand over 5 days): This is the quantity of oxygen consumed by the micro-organisms living in the water to degrade the organic matter (and only the organic matter) that remains in this water. This is measured over 5 days at a temperature of 20°C.


Collective sanitation: Collective sewerage network of the city. If it passes through the street, the connection is compulsory.


Decantation: Separation of suspended solids in water.

Domestic wastewater: Greywater + blackwater.


Effluent: Refers to a fluid that flows from a source, that leaves a device, an installation.

Emptying: Action of emptying and cleaning dirty bodies from a container (a septic tank, a grease trap).

Engineering office: Its role is to evaluate the capacity of the soil to treat and infiltrate the wastewater from the house. The EO will prepare the file on behalf of the owner so that it can be presented to the local authority.


Individual sanitation: If there is no collective network, the sanitation is said to be individual. In this case, the water is treated autonomously by a primary tank.


Greywater: Fat-free water containing fibrous material.

Groundwater: Underground water table that must be protected and preserved in case of land application.


Main sewer: When all the water from the sewerage network is evacuated to the sewer (collective network).

Manhole: Designed in plastic or concrete, the manhole is access that allows control and maintenance of the individual sewerage system.

Micro-station: The micro-station consists of a single tank divided into several compartments and an air generator. It uses aerobic bacteria (with oxygen) to destroy the polluting components of the water.


P.E. (Population Equivalent): The sizing of an individual sanitation system is done according to the capacity of the house. It is not measured in terms of the number of people who live there, but in terms of the number of main rooms, so 1 main room = 1 inhabitant equivalent.

Phyto-treatment: An alternative technical solution that uses aquatic plants to purify water. It is a very efficient process that can be considered when there is no sewerage system. The system must be mentioned in the building permit.

Primary tank: The primary tank allows the pre-treatment of all types of water, unlike the septic tank which can only hold black water.

Pumping chamber: Installation allowing the lifting of fluids with the help of a motor when the sewerage system is higher than the building.


Septic tank: A tank that allows the pre-treatment of black water from a dwelling when the sewage system is not collective.

Sewage treatment plant: A plant where all the water from the sewers is conveyed and treated in its entirety.

Spreading: Installation allowing the filtering of pre-treated water from a septic tank into the ground.


Traditional system: A sanitation system consisting of a septic tank followed by any type of landfill.


This blog post has provided definitions for some of the most important wastewater treatment terms. By understanding these terms, you can better understand how wastewater treatment works and why it is so important. Tell us in the comments if you are in doubt about a word that is not in the list above!

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