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Water Industry Terminology: Know Phrases, Terms, And Meanings Related to Water Treatment Processes

Updated: Dec 23, 2022

Water treatment is a process that improves the quality of water to make it fit for the specific end-use. The source water undergoes various processes and procedures to remove contaminants from it. The end use of the treated water may be for drinking, industrial water supply, recreation, irrigation, or for its safe return to the environment. Various methods of water treatment are widely used which include reverse osmosis, filtration, chemical dosing, and UV filtration. Also, because of the stress of depleting water resources, water recycling has increasingly become common.

Advanced Watertek has been a leading water treatment company in membrane-based technologies for water treatment since 1984. We have proven our experience in the sector with branches in different countries. We have state-of-the-art technology and minds who work towards constant upgradation.

In this blog, we aim to bring together and explain a list of technologies, procedures, mechanisms, and common water industry terminology related to treating water and wastewater. Read on to learn a glossary of words on water and wastewater treatment.

Acid Aerosol

Small liquid or solid particles that are acidic and suspended in the air.

Activated Carbon Filter (ACF)

It is a water treatment medium, found in block, granulated, or powdered form. It is produced by heating carbonaceous materials like coal, wood, or coconut shells. Activated Carbon filters are used to remove odor, color and chlorine from water.

Aerated Lagoon

A water treatment pond is used in wastewater treatment, which increases the speed of the biological decomposition of organic waste by stimulating the growth and activity of bacteria responsible for the degradation.

Aqueous Phase Oxidation (AOP)

AOP consists of highly reactive species used in the oxidative destruction of target pollutants. It creates more powerful and less selective secondary oxidants, hydroxyl radicals, in the water.

Activated Sludge Process (ASP)

It is a multi-chamber reactor unit used to remove nutrients from wastewater. It uses highly concentrated microorganisms to degrade organics and thus produce quality effluent.

Advanced Water Treatment

The level of water treatment that requires an 85-percent reduction in pollutant concentration. It is also known as tertiary treatment.

Advanced Wastewater Treatment

The treatment of sewage water includes the removal of nutrients like phosphorus, nitrogen, and a high percentage of suspended solids.

Biological Activated Carbon (BAC)

BAC filters are used to remove residual total organic carbon (TOC) from greywater after a membrane bioreactor. The two main TOC removal processes are adsorption to the granular activated carbon (GAC) and biological degradation.

Brackish Water

Water with the salinity of more than 1000 ppm (parts per million), but less than that of seawater.

Brackish Water Reverse Osmosis (BWRO)

BWRO is a separation process using pressure to force brackish water through a membrane that retains the solute on one side and lets the pure solvent pass to the other side.

Calcium hypochlorite

A chemical (Ca(OCl)2) is used for water disinfection, mostly in swimming pools or water purification plants.

Chemical Dosing System

A chemical dosing system is a machine or a series of machines that deliver a chemical substance at a controlled rate. The chemical dosing system is often connected to a water treatment or RO system.

Dissolved air flotation (DAF)

It is a water treatment process that clarifies wastewater by removing suspended matter like oil or solids. Air is dissolved in the water or wastewater under pressure and then released into the air at atmospheric pressure in a flotation tank basin.


The removal of excess or free chlorine from water by adsorption with activated carbon or by catalytic-type filter media.


Desalination is the process of removal of salt (sodium chloride) from salt water/ seawater.

Effluent Treatment Plant (ETP)

ETP is a type of wastewater treatment method designed to purify industrial wastewater. It is done so that the water can be released back into the environment.

Flash Distillation

Distillation in which hot water is introduced into a low-pressure chamber resulting in some of the water flashing or quickly turning to steam.

High Brackish Water

Water with salinity between 10,000 ppm and 15,000 ppm.

Hydrostatic Pressure

Hydrostatic pressure is the pressure exerted by water (or a liquid) when it is at rest, due to the force of gravity.

Industrial Wastewater (IWW)

It is the discard resulting from substances being dissolved or suspended in water during an industrial manufacturing process or cleaning activity.

Maximum Contaminant Level (MCL)

The maximum level of a contaminant allowed in water by federal law. It's based on health effects and available treatment methods.

Mixed Bed (MB)

Mixed bed resins are mainly used in the water purification industry. It is for polishing process water to achieve demineralized water quality.

Moving Bed Biofilm Reactor (MBBR)

It is a biological treatment process based on a combination of conventional activated sludge and biofilm media.

Membrane bioreactor (MBR)

It combines conventional biological treatment like microfiltration or ultrafiltration with membrane filtration to provide an advanced level of organic and suspended solids removal. It is widely used for municipal and industrial wastewater treatment.

Microfiltration (MF)

It is a separation process used in concentrating, purifying, or separating macromolecules, colloids, and suspended particles from solution.

Multimedia Filtration (MMF)

Multimedia filtration involves passing the feedwater through multiple layers of media (sand, gravel and pebbles) to reduce the level of suspended solids in incoming feedwater. Suspended solids may include small particles such as clay, grit, algae, and other microorganisms.

Nano Filtration (NF)

Nanofiltration is a filtration method using membranes with pore sizes from 1-10 nanometres. NF is an effective method as the pore sizes are smaller than in microfiltration and ultrafiltration, yet larger than in reverse osmosis. It removes divalent ions like calcium, magnesium, sulfates, etc.

Oxidation/ Reduction Potential (ORP)

ORP measures the ability of a lake or river to clean itself or break down waste products like contaminants, dead plants, and animals. If the ORP value is high, the oxygen level in the water is high, which means the bacteria that decompose dead tissue can work more efficiently. The higher the ORP value, the healthier the lake or river is.

Point of Entry (POE)

It is any device installed to treat the water entering a house or building for the treating water distributed throughout the houses.

Point-of-use (POU)

These are water filters designed to reduce or remove waterborne contaminants at the end of the water system, just before being used for drinking purposes. POU filter retains harmful pathogens, thus improving water quality.

Rotating Biological Contactor (RBC)

It is a biological fixed-film treatment process used in the secondary treatment of wastewater following primary treatment.

Reverse Osmosis (RO)

Reverse Osmosis is a technology used to remove contaminants from water by pushing the water under pressure through a semi-permeable membrane.

RO Membranes (Reverse Osmosis Membranes)

RO Membranes are the semi-permeable membrane filters used in an RO plant to filter out the salts from the seawater or brackish water.

Sand Filtration

It is a frequently used method to remove suspended solids from water. The filtration consists of multiple layers of sand with specific gravity. It can be supplied in different sizes and materials, both hand-operated and fully automatic.

RO Skid

The RO system is often built on a steel skid to protect the system and reduce the space it takes.

Submerged Aerated Fixed Film (SAFF)

The Submerged Aerated Filter (SAF) system utilizes a biological treatment process whereby highly aerated effluent flows through inert media that is completely submerged; fixed microbial film reduces the BOD and ammoniacal content of the effluent.

It's a cost-effective method of wastewater treatment primarily used in residential and commercial buildings. The three stages of this technology are: a. Primary Settlement b. Secondary Treatment c. Final Settlement / Clarification.

Strong Base Anion (SBA)

During the process, anions present in the water, i.e., Cl, SO4, HCO3, silica, etc., are exchanged with OH¯ ions in the resin, and the water is demineralized. Thus, water becomes demineralized resulting in pure water.

Sequencing Batch Reactor (SBR)

It is a fill-and-draw activated sludge system for wastewater treatment. Wastewater is added to a single batch reactor, treated to remove undesirable components, and then discharged.

Solids Retention Time (SRT)

It is the time the solid fraction of the wastewater spends in a treatment unit. The quantity of solids maintained in the reactor is divided by the number of solids coming out of the reactor each day.

Sewage Treatment Plant (STP)

A Sewage Treatment Plant is a wastewater treatment plant that aims to remove contaminants from sewage to produce water that is suitable to be discharged to the surrounding environment or for further treatment.

Sea Water Reverse Osmosis (SWRO)

SWRO is a water treatment system that can remove salt and other impurities from seawater using the process of reverse osmosis. Reverse Osmosis involves passing liquid through a semi-permeable membrane under excessive pressure.

Seawater Reverse Osmosis Plant / Seawater Reverse Osmosis System

Sea water Reverse Osmosis plant / system is the machine that desalinates salt water to remove the salts and generate clean water, using the reverse osmosis process.

Trickling Biofilter (TBF/TF)

It is a widely used aerobic biological treatment system. The downflow-packed bed type of reactor consists of a fixed bed made up of different inert materials. Biofilm grows on the surface of the inert bed.

Thin Film Composite (TFC)

Thin-film composite membranes are semipermeable membranes used in water purification or desalination systems.

Tertiary Treated Sewage Effluent (TSE)

Tertiary treatment is the wastewater treatment process after secondary treatment. Contaminants that secondary treatment was not able to clean up are cleaned out.

Up flow Anaerobic Sludge blanket (UASB)

It is a form of anaerobic digester used in wastewater treatment to remove organic pollutants from wastewater. Anaerobic microorganisms convert organic pollutants into 'biogas' which contains methane and carbon dioxide.

Ultra Filtration (UF)

Ultrafiltration is a variant of membrane-based technology where the systems remove a high percentage of microbes from the feed water. The treatment requires relatively little energy. Hence it offers a simple, chemical-free, and user-friendly method of treating water.

Ultraviolet (UV)

UV technology purifies water by using ultraviolet rays to kill the microorganisms in the water and prevent their reproduction by disrupting their DNA. UV rays do not lead to chemical changes in the water.

Wastewater Treatment Plant (WTP)

A wastewater treatment plant aims to remove contaminants from sewage to produce an effluent suitable for discharge to the environment or further treatment, thus preventing water pollution from raw sewage discharges.

Wastewater Treatment Facility (WWTF)

Wastewater treatment is a system or equipment/s used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle.

Wastewater Treatment Plant (WWTP)

Wastewater treatment plants remove pollutants from domestic and industrial waste. Wastewater travels through sewer pipes to treatment plants where it is treated and then returned to rivers and oceans, or in some cases, used for irrigation.

Monitoring Parameters, Metrics, and Units

Biochemical Oxygen Demand (BOD)

BOD is the amount of dissolved oxygen required by aerobic biological organisms to break down organic material present in a given water sample at a specific temperature over a time period. BOD value is expressed in milligrams of oxygen consumed per litre of the sample during five days of incubation at 20 °C. It is often used as a surrogate for water's degree of organic pollution.


CFCs are nontoxic chemicals containing atoms of carbon, chlorine, and fluorine. They are used to manufacture aerosol sprays, blowing agents for foams and packing materials, solvents, and refrigerants.

Cubic Meter Per Day (CMD)

The metric is used to measure the volume of water produced by a water treatment plant. The liters per day unit number 1,000.00 L/d converts to 1 m3/d, one cubic meter per day. It is the EQUAL flow rate value of 1 cubic meter per day but in the Liters per day flow rate unit alternative.

Cubic Meter Per Hour (CMH)

CMH is a unit of volumetric flow. The cubic meter unit per hour is the number of cubic meters of liquid flowing through the monitored place in one hour. One cubic meter per hour corresponds to 0.278 liters per second or 24 cubic meters per day.

Chemical Oxygen Demand (COD)

COD is a test that measures the amount of oxygen required to chemically oxidize the organic material and inorganic nutrients like Ammonia or Nitrate present in water.

Discharge Monitoring Report (DMR)

DMRs report with self-monitoring results for wastewater required by National Pollutant Discharge Elimination System (NPDES) permits and some Water Quality Management (WQM) permits.

Dissolved Oxygen (DO)

It is a measure of the oxygen dissolved in water. Dissolved oxygen is an important parameter in assessing water quality as it influences the organisms living within a body of water.

Dissolved Organic Carbon (DOC)

It is the fraction of organic carbon operationally defined as that which can pass through a filter with a pore size typically between 0.22 and 0.7 micrometers. The fraction remaining on the filter is called particulate organic carbon (POC).

Grains Per Gallon (GPG)

GPG is a unit of water hardness defined as 1 grain (64.8 milligrams) of calcium carbonate dissolved in 1 US gallon of water (3.785412 L). It translates into 1 part in about 58,000 parts of water or 17.1 parts per million (ppm).

Jackson Turbidity Unit (JTU)

JTU is a historical measurement done with the Jackson Candle Turbidimeter. Turbidity is commonly measured using a nephelometer which uses a light beam and a light detector set to one side of the source beam. The units from a calibrated nephelometer are called Nephelometric Turbidity Units (NTU). JTU is not a common method in today's times.

Kilolitres per day (KLD)

One kiloliter per day is a volume flow rate of one kiloliter per period of 86400 seconds. It measures the velocity at which air flows into the sample probe.

Meter Cube Per Hour (m³/Hr)

A cubic meter per hour is a unit of volumetric flow. The unit of cubic meter per hour is the number of cubic meters of liquid that will flow through the monitored place in one hour.

Meter Cube Per Second (m³/s)

A cubic metre per second is the unit of volumetric flow rate in the International System of Units (SI) equal to that of a stere or cube with sides of one metre (39.37 in) in length exchanged or moving each second.

Million gallons per day (MGD)

MGD refers to a flow rate expressed in millions of gallons per day.

Megalitres per day (MLD)

It's the volume flow rate of 1 megaliter per period of 86400 seconds.

Mixed liquor suspended solids (MLSS)

MLSS is the concentration of suspended solids in an aeration tank during the activated sludge process that happens during wastewater treatment. The unit MLSS is primarily measured in mg/L, but for activated sludge, it is mostly measured in g/L, which is equal to kg/m3.

Mixed liquor volatile suspended solids (MLVSS)

The amount (mg/L) of organic or volatile suspended solids in the mixed liquor of an aeration tank. This portion is used as a measure or indication of the microorganisms present.

Nominal Capacity (Nom. Cap.)

Nominal Capacity is the volume of the tank when filled to the brim.

Nephelometric Turbidity Unit (NTU)

NTU is the unit used to measure the turbidity of a fluid or the presence of suspended particles in water. When the concentration of suspended solids is high, the turbidity is high and it looks dirty.

The potential of Hydrogen (pH)

pH is the measure of acidity or alkalinity in any water-soluble substance. It represents potential hydrogen.

Parts Per Billion (PPB)

It is the number of units of mass of a contaminant per 1000 million units of the total mass.

Parts Per Million (PPM)

PPS measures the mass of a chemical or contaminant per unit volume of water.

Silt Density Index (SDI)

SDI is a measurement of the fouling potential of suspended solids. It estimates the rate at which colloidal and particle fouling will occur in water purification systems using reverse osmosis or Nanofiltration membranes.

Total Dissolved Solids (TDS)

TDS measures the dissolved combined content of all inorganic and organic substances present in a liquid in molecular, ionized, or micro-granular suspended form.

Total Kjeldahl Nitrogen (TKN)

TKN is used to measure organic nitrogen and ammonia in wastewater.

Total Maximum Daily Load (TMDL)

It is a regulation system that controls the number of pollutants discharged from each watershed across the nation to be within the scope of load allocation.

Total Organic Carbon (TOC)

TOC is the amount of carbon found in an organic compound. It is often used as a non-specific indicator of the water quality of pharmaceutical manufacturing equipment.

Total Suspended Solids (TSS)

TSS is the solids in water that can be trapped by a filter.

Total Trihalomethanes (TTHMs)

TTHMs reduce the germicidal activity of chlorine in alkaline water. It is the group of disinfection byproducts formed when chlorine compounds that are used to disinfect water react with other naturally occurring chemicals in the water.

US Gallons per day (US GL/Day)

1 Gallon per day equals approximately 4.381 263 638 888 x 10-8m3/s.

Volatile Organic Compounds (VOCs)

VOCs are often components of petroleum fuels, hydraulic fluids, paint thinners, and dry cleaning agents. They are common ground-water contaminants.

Volatile Suspended Solids (VSS)

VSS is a water quality measure obtained from the loss on ignition of the mass of measured total suspended solids. We hope this water terminology list helped you understand water terms and phrases commonly used in the industry.

There are various types of water treatment methods of which large-scale water treatment is required when the population needing water is large and surface water sources need to be used. Water treatment includes various steps which have their own significance that contributes towards clean water.


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