Wastewater Treatment Glossary

Arvia’s water treatment glossary details every term you need to know about the water and wastewater treatment industry.

The micron rating of a filter which indicates that any particle larger than a specified size will not pass through the filter.

The largest particle size that can pass through a specific filtration unit.

The adhesion of ions, molecules or atoms from a gas, liquid or dissolved solid to a surface.

Liquid or solid particles which are acidic and small enough to become airborne.

The ability of water to resist changes in pH.

Carbon process to have small, low-volume pores that increase the surface area made available for adsorption or alternative chemical reactions.

The most common adsorption medium, produced by heating carbonaceous substances or cellulose bases in the absence of air. Commonly used to remove organic matter and dissolved gases from water.

A biological treatment process for domestic or industrial wastewater which converts soluble, organic matter to solid biomass.

An advanced oxidation process (AOP) is one that uses the hydroxyl radical to achieve oxidation. There are several different process that generate hydroxyl radicals.

The process of increasing oxygen saturation by introducing air. This is commonly used in secondary wastewater treatment during the activated sludge process.

A tank used in the aeration process to inject air into the water.

An environment that contains sufficient oxygen for the micro-organisms to use for the oxidation of pollutants.

The keenness with which an ion exchanger holds onto a counter-ion.

A measured portion of a water sample taken for analysis.

The capability of water to neutralise acid, preventing water pH levels from becoming too basic or acidic.

An environment where there is an absence of oxygen and no oxidised species (for example nitrates, sulphates etc).

A negative charged ion that results from the disassociation of salts, acids or alkalis in a solution. Anionic polymers are used in the clarification process during water treatment.

Negatively charged flocculant which is used in water treatment to aid the separation of solids and liquids.

An environment without oxygen (typically defined as less than 0.5 mg/l). Anoxic processes are used in wastewater treatment to remove nitrogen from wastewater.

The maximum concentration of a chemical that dissolves in a given amount of water.

The capacity of natural water to receive wastewater or toxic materials without negative effects to aquatic life or humans consuming the water.

The process of reversing the flow of liquids in filtration systems in water treatment plants which helps with filter media recovery.

Filter systems which remove soluble inorganic contaminants and sediment from wastewater.

Contamination of water with unwanted bacteria.

A disposable sediment filter designed to be used as a barrier or sift method for removing particulates from water.

An alkaline substance with a pH of greater than 7.5.

Sediment particles resting on the bottom of a water channel which are pushed along by the flow of water.

The ratio of the number of particles entering and exiting the filtration unit of a particular size. Higher beta ratios indicate a more efficient filter.

A measure of the amount of dissolved oxygen (measured in mg/L) required for the decomposition of organic matter by micro-organisms. BOD is most frequently used as a test method to gauge the effectiveness of water treatment processes. This is usually specified as a BOD5 which is the oxygen required to oxidise the biodegradable organics in 5 days.

A chemical which kills microorganisms found in water and is often used to eliminate bacteria and other single-cell organisms from wastewater.

Pollutants that can decompose naturally.

Living organisms that can have negative health effects on humans.

Systems that support biological processes under controlled conditions. Activated sludge bioreactors are commonly used in water treatment.

The biological treatment of wastewater and sludge by inducing the breakdown of organics and hydrocarbons to carbon dioxide and water.

Highly salty, heavily mineralised water.

A substance used to prevent a change in pH in a solution.

Thin membranes used for Reverse Osmosis, nanofiltration, ultrafiltration and microfiltration.

Chemical compounds containing a carbonate ion (CO32-).

A compound that is cancer causing.

Disposable, easily replaceable sediment filters used to remove particulates from water or other liquid.

A sedimentation area which removes pollutants from runoff.

Pumps that transport fluids by converting rotational kinetic energy to the hydrodynamic energy of the fluid flow, providing very high flow rates.

A measure which indicates the number of microorganisms in a body of water.

A measure of the organic pollutants in water. Measure in mg/L or ppm.

The introduction of chemical contaminants into a body of water.

Applying chemicals to water to aid in the removal of contaminants and make it suitable for intended use.

The application of chlorine to water to disinfect and control microorganisms.

Coagulation is a chemical process which neutralises the charge on particles. This is often achieved through the addition of ferric or aluminium salts. Coagulation is often used together with flocculation.

When found in water, coliform bacteria serve as indicators of pollution and pathogens in the water. They are typically found in the intestinal tract of humans and other warm-blooded animals.

A rating of the purity of a body of water based on the amount of coliform bacteria contained within.

Matter of extremely small particle size, in the range of 10-5 to 10-7 cm in diameter.

A series of water samples taken over a set period of time and weighted by flow rate.

The amount of material left behind following the reverse osmosis filtration process.

Any foreign component present in water.

A test solution used for the assessment of the performance of an analytical procedure.

A microorganism commonly found in untreated surface water which causes gastrointestinal illnesses in humans.

An electronic device used to record data signals. Typically used in water treatment for hydrographic recording and water quality monitoring, amongst other things.

Any process which serves to reduce the alkalinity of a body of water.

The process of drawing off the top layer of liquid after the heaviest material has settled.

Removing carbon dioxide from water.

A method used to dispose of wastewater and other fluid wastes by injecting them into rock formations such as limestone or sandstone which are deep underground.

Removing fluoride from water.

Chemicals added to wastewater discharges to prevent the water from foaming when discharged into another body of water.

The process of removing ions from water.

The process of removing minerals from water.

Water that has all the minerals and salts removed.

A chemical additive that removes the emulsifying characteristics of water and is commonly used to separate emulsified oil in water.

The removal of nitrate product from water to meet common water standards.

The process of removing dissolved salts and minerals from water.

The release of matter from the adsorption medium, typically done to recover material.

The separation of water from sludge.

A closed tank for wastewater treatment in which bacterial action is used to remove or break down organic materials.

Distilled water that has been aerated, buffered and stabilised. Often applied in BOD tests.

Surface water that flows directly into rivers and lakes.

The flow of surface water in a stream or canal.

The removal or inactivation of pathogens in a body of water.

Inducing flotation of substances with very fine air bubbles of 40 to 70 microns.

The concentration of oxygen in water at a specific time, expressed as ppm or mg/L.

Solid material that dissolved in water and can’t be removed by filtration (although it can be removed by reverse osmosis).

The process of selective boiling and condensation for purifying water or other liquids.

The removal of surface of sub-surface water from a particular area.

Removing materials from below the surface of water using a scoop or suction device.

The treatment of water to make it fit for human consumption.

Wastewater discharged from an industrial facility, sewer or treatment plant.

A device used to inject chemicals into wastewater.

A water purification process which uses electricity, ion exchange membranes and resins to remove ions from water into a concentrate stream.

Water that is rich in nutrients such as nitrogen and phosphorous.

A key part of the early stage of a project in which the complexity and cost of the project is analysed before deciding on how to proceed.

Sampling and analysing water in the environment, such as analysing river water at the point of the river. Typically used in conjunction with lab analysis.

A layer of sand or gravel in a tank or reservoir used to filter solids from large volumes of water.

Using a porous substance to separate solids from liquids.

The filtration of particles 5 microns or larger.

The filtration of particles 0.1 to 10 microns in diameter.

The filtration of particles ranging from 0.1 to 0.001 microns in size.

Physical process for bonding together small, lightweight particles into larger, heavier groups which can then be clarified or filtered, helping the removal of suspended solids. Often used in association with coagulation.

An additive which causes smaller particles to clump together for the process of flocculation. These are often organic polymers.

The discharge rate of a resource.

Water containing less than 1mg/L of dissolved solids of any type.

Heated carbon designed to encourage active sites to absorb pollutants.

Water held underground in the soil or pores and crevices in a rock.

The time required for a pollutant to lose one half of its original concentration.

Water that contains a large amount of calcium and magnesium.

Metals which have a density of 5.0 or higher and a high elemental weight. The majority of these are toxic to humans in even the smallest doses.

Highly treated water designed to meet stringent specifications which is commonly used in the biotechnology and pharmaceutical industries.

The rate water is able to move through a permeable medium.

Microorganisms or other objects in water which reduce the purity level.

Microorganisms whose presence indicates pollution and the potential presence of more harmful microorganisms.

Tests for indicator organisms which could signal the need for further tests on a body of water.

The introduction of pollutants from commercial or industrial facilities into a publicly-owned wastewater treatment system.

Wastewater generated by commercial activities such as: manufacturing, agriculture or mining. Industrial wastewater typically contains more contaminants than domestic wastewater and requires further treatment.

Any water entering a manufacturing facility, treatment system or other body of water.

A chemical the helps to stop other chemical reactions.

Chemicals of mineral origin, rather than being of a carbon structure.

An atom in a solution that is charged either positively or negatively.

The process of replacing undesirable ions in a solution with desirable ions. Typically, these will have the same charge and improve adsorption.

A procedure performed in a laboratory which test a sample of water with differing chemical doses, mix speeds and settling times to get a best estimate of how to achieve your required water quality.

Any testing performed in a controlled, laboratory setting. Typically done to perform an in-depth analysis of a sample across a wide range of parameters.

Purified water used in a laboratory to create solutions or dilute samples.

Discharging wastewater onto the ground for treatment or reuse.

A process in which raw water is treated with lime (calcium hydroxide) to raise the pH.

The maximum level of contaminants allowed in water by law.

A thin, semi-permeable skin which allows water some particles to pass through but not others.

A combination of biological treatment processes and membrane filtration processes for wastewater treatment.

Separating dissolved and suspended solids in a wastewater solution by using a membrane.

The separation of particles ranging from 0.1 microns to 10 microns in size.

Mobile mounted water treatment typically in trailers, allowing you to move it between sites as required.

Wastewater collected from residential, commercial and industrial sources within a public area.

A measurement of the clarity of a liquid.

Substances are added to neutralise water, so that the water it is neither acid, nor basic. Neutralisation does not exactly result in a pH of 7.0, it just means the balance point of an acid-base reaction.

A water treatment process in which bacteria converts toxic ammonia to less harmful nitrate.

Carbon-hydrogen structured substances.

The process of water molecules passing through membranes to the part with the largest amount of dissolved impurities.

Where the water that is treated by the plant is released.

A chemical reaction involving the transfer of electron, specifically the loss of electrons. This is often achieved by the addition of oxygen to a chemical.

An oxidizing agent, that consists of three oxygen atoms (rather than two as is found with oxygen in the air) which can be found in the ozone layer. It is used as a disinfection method to treat water.

A device that creates ozone by sending a voltage through oxygen.

The mass of particulates per unit volume of water.

Elimination of microorganisms using heat.

Microorganisms that produce diseases.

The length of time that a compound can last in the environment once it is released.

pH is one of the measures of water quality and is calculated from the amount of hydrogen ions that are present. This is used to specify the acidity or alkalinity of a solution, it is measured on a scale from 0 to 14. A pH of less than 7 is considered acidic, a pH of 7 is neutral and pHs greater than 7 are alkaline.

Processes used in wastewater treatment. Physical treatment is used for instance, in filtration. Chemical treatment can involve chlorination, coagulation, or ozone treatment.

The testing of a technology under site conditions on-site in a small scale treatment plant in order to identify any potential problems before installation of the technology.

Point-Of-Entry treatment. Treatment at inlets of water in an entire facility.

An opening in something that allows water to enter.

A substance that carries an either positive or negative charge.

A contaminant that can cause danger to the life of organisms.

Water that has been treated to drinking water standard.

One chemical that has the ability of increasing the effect of another chemical.

Treatment when and where the water is required

An insoluble product that is produced in an aqueous chemical reaction.

The process of changing dissolved compounds to insoluble compounds, this results in the ability to remove the compounds by filtration.

Pipes under pressure that allows water and liquids to flow to a higher level.

Removal of solids in sewage through sedimentation/clarification

Water that is used in the manufacturing process of products.

Water that is contained within a consumer product.

Removal of chemicals, gases, and other substances from water.

Untreated wastewater and its contents.

Water that is taken from the environment before treatment.

The process where carbon dioxide is put into water to lower the pH.

Recycling water after it has been used. The water may have to pass through a wastewater treatment system before it can be reused.

A chemical reaction in which ions gain electrons to reduce their positivity.

The breaking of an emulsion into individual parts.

The Reversed Osmosis (RO) process uses a semi-permeable membrane to remove dissolved solids and molecules from water. The process requires pressure to overcome osmotic pressure and produce water safe for use. It also produces a concentrate stream containing all the dissolved.

The part of rain water that runs off the land into water.

The annual amount of water that can be taken from a source over a period of time without draining that source beyond its ability to be naturally refilled.

The presence of soluble minerals in water.

Sand filtration is a method to remove suspended solids from water. The filtration method consists of multiple layers of sand with a variety in size. Sand filters can be supplied in different sizes and can be both hand operated and fully automated.

The precipitate that forms in places with water as a result of a physical or chemical change.

Use of screens to remove floating substances and solids from sewage.

Biological treatment of contaminants from primary wastewater treatment.

Particles and substances being deposited in water due to a natural process, usually gravity.

Particles and substances washed from land into water that settle, usually after rain.

A sewer system that carries only sanitary sewage. This allows the treatment plants to treat sanitary wastes only.

The isolation of the compounds in a substance.

Solids in wastewater that will settle over a certain period of time.

The process of sinking a substance in water. This occurs when the substance aren’t dissolved in water.

Waste liquid in a sewer system.

When untreated sewage gets into a product/process.

The process of sewage collection, treatment, and disposal.

A residue, containing microorganisms and products.

The removal of calcium and magnesium from water to soften it.

Water that has been softened and/or has low concentrations of the dissolved minerals calcium or magnesium.

Removal of wastewater from waste or changing it chemically to make it less permeable.

The amount of mass in a compound that will dissolve in water.

A substance that has been dissolved in a liquid.

Substance capable of dissolving substances.

Ground water coming out of the earth where the water table is greater than the ground surface.

The transitions of water directly from the solid state to the gaseous state, without passing through the liquid state.

All the water that is naturally open to the atmosphere, all bodies of water.

Solid particles that are suspended in a solution.

The third level of wastewater treatment that is used to remove nutrients and completes advanced treatment or disinfection that is needed.

A process to determine how much of a substance is present in water by adding another substance and measuring how much of that substance must be added to produce a reaction.

The concentration of cations and anions in water.

The total of calcium and magnesium hardness.

The weight of solids per unit volume of water. The total weight involves both dissolved and suspended matter.

Harmful compounds that cause death, disease, or birth defects in organisms that ingest or absorb them.

Pipes that raw water moves through from its source to a water treatment plant.

A facility built to treat water wastewater before use or discharge into the environment.

A treatment unit that contains material with a bacteria film over which water is trickled. The bacteria breaks down the organic wastes.

Turbidity is a measure of the loss in transparency due to the presence of suspended matter.

A flow that contains many rapid fluctuations.

Membrane technology is used to remove matter and contaminants.

A process using short wave-length light that can kill microorganisms, resulting in them being polarised or ionised and more easily removed from water.

The upward flow of water.

The used water from a place that contains dissolved or suspended matter.

Facilities designed for the treatment of wastewater.

Material that has enough concentration in water to be harmful.

The amount of impurities water has and the condition that the water is in.

Using water again after it has been used, usually some form of treatment is applied.

The highest concentration of a chemical compound dissolved in water.

A place for liquid wastes to be stored before biochemical treatment.

The surface of groundwater in the soil.

A device that is used to control water flows.

A biological substance that is a chemical foreign to a biological system.

The rate of production.

The idea of recycling and reusing all of the water used in industry. This is so no water is wasted and released to the environment.

This is the charge that develops on a solid surface in contact with a liquid.

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