Wastewater Treatment Glossary

Absolute

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

Absolute filtration rating

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

Adsorption

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

Acid aerosol

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

Acid neutralising capacity

The ability of water to resist changes in pH.

Activated carbon

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

Activated coal

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.

Activated sludge

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

Advanced oxidation process

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

Aeration

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

Aeration tank

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

Aerobic

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

Affinity

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

Aliquot

A measured portion of a water sample taken for analysis.

Alkalinity

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

Anaerobic

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

Anion

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.

Anionic flocculant

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

Anoxic

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.

Aqueous solubility

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

Assimilative capacity

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

Backwash

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

Backwash filters

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

Bacterial water contamination

Contamination of water with unwanted bacteria.

Bag filter

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

Base

An alkaline substance with a pH of greater than 7.5.

Bed load

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

Beta ratio

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.

Biochemical (Biological) Oxygen Demand (BOD)

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.

Biocide

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

Biodegradable pollutants

Pollutants that can decompose naturally.

Biological contaminants

Living organisms that can have negative health effects on humans.

Bioreactors

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

Bioremediation

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

Brine

Highly salty, heavily mineralised water.

Buffer

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

Capillary membranes

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

Carbonates

Chemical compounds containing a carbonate ion (CO32-).

Carcinogen

A compound that is cancer causing.

Cartridge filter

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

Catch basin

A sedimentation area which removes pollutants from runoff.

Centrifugal pumps

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

Colony Forming Units (CFU)

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

Chemical Oxygen Demand (COD)

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

Chemical pollution

The introduction of chemical contaminants into a body of water.

Chemical treatment

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

Chlorination

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

Coagulation

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.

Coliform bacteria

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.

Coliform index

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

Colloids

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

Composite sample

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

Concentrate

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

Contaminant

Any foreign component present in water.

Control solution

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

Cryptosporidium

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

Data logger

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

Dealkanisation

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

Decant

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

Decarbonation

Removing carbon dioxide from water.

Deep well injection

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.

Defluoridation

Removing fluoride from water.

De-foaming agents

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

Deionisation

The process of removing ions from water.

Demineralisation

The process of removing minerals from water.

Demineralised water

Water that has all the minerals and salts removed.

Demulsifier

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

Denitrification

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

Desalination

The process of removing dissolved salts and minerals from water.

Desorption

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

Dewatering

The separation of water from sludge.

Digester

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

Diluting water

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

Direct run-off

Surface water that flows directly into rivers and lakes.

Discharge

The flow of surface water in a stream or canal.

Disinfection

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

Dissolved Air Flotation (DAF)

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

Dissolved oxygen

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

Dissolved solids

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

Distillation

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

Drainage

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

Dredging

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

Drinking water treatment

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

Effluent

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

Ejector

A device used to inject chemicals into wastewater.

Electro Deionisation (EDI)

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

Eutrophic

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

Feasibility analysis

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.

Field analysis

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.

Filter beds

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

Filtration

Using a porous substance to separate solids from liquids.

Macro filtration

The filtration of particles 5 microns or larger.

Micro filtration

The filtration of particles 0.1 to 10 microns in diameter.

Ultra filtration

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

Flocculation

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.

Flocculent

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

Flow

The discharge rate of a resource.

Freshwater

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

Granular activated carbon

Heated carbon designed to encourage active sites to absorb pollutants.

Groundwater

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

Half-life

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

Hard water

Water that contains a large amount of calcium and magnesium.

Heavy metals

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.

High purity water

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

Hydraulic conductivity

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

Impurities

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

Indicator organisms

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

Indicator tests

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

Indirect discharge

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

Industrial wastewater

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

Influent

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

Inhibitor

A chemical the helps to stop other chemical reactions.

Inorganic chemicals

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

Ion

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

Ion exchange

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

Jar test

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.

Lab testing

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.

Laboratory water

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

Land application

Discharging wastewater onto the ground for treatment or reuse.

Lime softening

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

Maximum Contaminant Level (MCL)

The maximum level of contaminants allowed in water by law.

Membrane

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

Membrane BioReactors (MBR)

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

Membrane filtration

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

Microfiltration

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

Mobile water treatment

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

Municipal wastewater

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

Nephelometer Turbidity Units (NTU)

A measurement of the clarity of a liquid.

Neutralisation

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.

Nitrification

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

Organic matter

Carbon-hydrogen structured substances.

Osmosis

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

Outfall

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

Oxidation

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.

Ozone

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.

Ozone generator

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

Particulate loading

The mass of particulates per unit volume of water.

Pasteurisation

Elimination of microorganisms using heat.

Pathogens

Microorganisms that produce diseases.

Persistence

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

pH

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.

Physical and chemical treatment

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

Pilot tests

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.

POE-treatment

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

Pore

An opening in something that allows water to enter.

Polar substance

A substance that carries an either positive or negative charge.

Pollutant

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

Potable water

Water that has been treated to drinking water standard.

Potentiation

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

Point-Of-Use (POU)-treatment

Treatment when and where the water is required

Precipitate

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

Precipitation process

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

Pressure sewers

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

Primary water treatment

Removal of solids in sewage through sedimentation/clarification

Process water

Water that is used in the manufacturing process of products.

Product water

Water that is contained within a consumer product.

Purification

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

Raw sewage

Untreated wastewater and its contents.

Raw water

Water that is taken from the environment before treatment.

Recarbonisation

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

Recirculation

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

Reduction

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

Resolution

The breaking of an emulsion into individual parts.

Reverse Osmosis process

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.

Run-Off

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

Safe yield

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.

Salinity

The presence of soluble minerals in water.

Sand filtration

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.

Scale

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

Screening

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

Secondary treatment

Biological treatment of contaminants from primary wastewater treatment.

Sedimentation

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

Sediments

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

Separate sewer

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

Separation

The isolation of the compounds in a substance.

Settleable solids

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

Settling

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

Sewage

Waste liquid in a sewer system.

Sewage contamination

When untreated sewage gets into a product/process.

Sewerage

The process of sewage collection, treatment, and disposal.

Sludge

A residue, containing microorganisms and products.

Softening

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

Soft water

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

Solidification

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

Solubility

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

Solute

A substance that has been dissolved in a liquid.

Solvent

Substance capable of dissolving substances.

Spring

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

Sublimation

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

Surface water

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

Suspended solids

Solid particles that are suspended in a solution.

Tertiary treatment

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

Titration

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.

Total dissolved solids

The concentration of cations and anions in water.

Total hardness

The total of calcium and magnesium hardness.

Total solids

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

Toxic water pollutants

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

Transmission lines

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

Treatment plant

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

Trickling filter

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

Turbidity

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

Turbulent flow

A flow that contains many rapid fluctuations.

Ultrafiltration

Membrane technology is used to remove matter and contaminants.

Ultra-violet (UV) oxidation

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

Up-flow

The upward flow of water.

Wastewater

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

Wastewater Treatment Plants

Facilities designed for the treatment of wastewater.

Water pollution

Material that has enough concentration in water to be harmful.

Water quality

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

Water recycling

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

Water solubility

The highest concentration of a chemical compound dissolved in water.

Water storage pond

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

Water table

The surface of groundwater in the soil.

Weir

A device that is used to control water flows.

Xenobiotic

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

Yield

The rate of production.

Zero discharge water

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.

Zeta potential

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