The micron rating of a filter. It indicates that any particle larger than a specific size will be trapped within the filter.


When a solid takes up molecules into its structure.


The quantitative capacity of water to neutralize a base, expressed in ppm or mg/L calcium carbonate equivalent. The number of hydrogen atoms that are present determines this. It is usually measured by titration with a standard solution of sodium hydroxide.

Activated sludge

Oxygen dependent biological process that serves to convert soluble organic matter to solid biomass, that is removable by gravity or filtration.


Separation of liquids, gases, colloids or suspended matter from a medium by adherence to the surface or pores of a solid.

Advanced oxidation process

One of several combination oxidation processes. Advanced chemical oxidation processes use (chemical) oxidants to reduce COD/BOD levels, and to remove both organic and oxidisable inorganic components. The processes can completely oxidise organic materials to carbon dioxide and water, although it is often not necessary to operate the processes to this level of treatment.

A wide variety of advanced oxidation processes are available:

– Chemical oxidation process using hydrogen peroxide, ozone, combined ozone & peroxide, hypochlorite, Fenton’s reagent, etc.

– Ultra-violet (UV) enhanced oxidation such as UV/ ozone, UV/ hydrogen, UV/air

– Wet air oxidation and catalytic wet air oxidation (where air is used as the oxidant)

Advanced water treatment

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

Advanced Wastewater Treatment

Any treatment of sewage water that includes the removal of nutrients suchas phosphorus and nitrogen and a high percentage of suspended solids.

Aerated lagoon

A water treatment pond that speeds up biological decomposition of organic waste by stimulating the growth and activity of bacteria, which are responsible for the degradation.


Technique that is used with water treatment that demands oxygen supply, commonly known as aerobic biological water purification. Either water is brought into contact with water droplets by spraying or air is brought into contact with water by means of aeration facilities. Air is pressed through a body of water by bubbling and the water is supplied with oxygen.

Aeration tank

A tank that is used to inject air into water.


A process that takes place in the presence of oxygen, such as the digestion of organic matter by bacteria in an oxidation pond.


Alkalinity means the buffering capacity of water; the capacity of the water to neutralize itself. It prevents the water pH levels from becoming too basic or acid. It also adds carbon to water. Alkalinity stabilizes water at pH levels around 7. However, when the acidity is high in water the alkalinity decreases, which can cause harmful conditions for aquatic life.

In water chemistry alkalinity is expressed in ppm or mg/L of equivalent calcium carbonate. Total alkalinity of water is the sum of all three sorts of alkalinity; carbonate, bicarbonate and hydroxide alkalinity.


A process that takes place in the absence of oxygen, such as the digestion of organic matter by bacteria in a UASB-reactor.


A negatively charged ion that results from the dissociation of salts, acids or alkali’s in solution.


A site in electrolysis where metal goes into solution as a cation leaving behind an equivalent of electrons to be transferred to an opposite electrode, called a cathode.


The action of one particle rubbing against the other in a filter media or ion exchange bed that can in time cause breakdown of the particles.

Available chlorine

A measure of the amount of chlorine available in chlorinated lime, hypochlorite compounds, and other materials.



The flow of water in a medium in a direction opposite to normal flow. Flow is often returned into the system by backflow, if the wastewater in a purification system is severely contaminated.

Back Pressure

Pressure that can cause water to backflow into the water supply when a user’s waste water system is at a higher pressure than the public system.


Reversing the flow of water back through the filter media to remove entrapped solids.


Microscopically small single-cell organisms, that reproduce by fission of spores.

Bacterial water contamination

The introduction of unwanted bacteria into a water body.


An alkaline substance that has a pH that exceeds 7,5.

Bed Load

Sediment particles resting on or near the channel bottom that are pushed or rolled along by the flow of water.


Salts containing the anion HCO3-. When acid is added, this ion breaks into H2O and CO2, and acts as a buffer.

Biochemical Oxygen Demand (BOD)

The amount of oxygen (measured in mg/L) that is required for the decomposition of organic matter by single-cell organisms, under test conditions. It is used to measure the amount of organic pollution in wastewater.


A chemical that is toxic to microrganisms. Biocides are often used to eliminate bacteria and other single-cell organisms from water.

Biodegradable pollutants

Pollutants that are capable of decomposing under natural conditions.


Population of various microrganisms, trapped in a layer of slime and excretion products, attached to a surface.

Biological contaminants

Living organisms such as viruses, bacteria, fungi, and mammal and bird antigens that can cause harmful health effects to humans.

Biologically activated carbon

Activated carbon that supports active microbial growth, in order to aid in the degradation of organics that have been absorbed on its surface and in its pores.

Biological oxidation

Decomposition of complex organic materials by microrganisms through oxidation.


Biological Oxygen Demand or Biochemical Oxygen Demand is a procedure, used in water quality management, for determining how fast biological organisms use up oxygen in a body of water.


The reverse flow of water, through a filter or filtration media, used for removing solids accumulated during the filtration process.

By-Pass valve

A valve used to control an alternative flow path.

Brackish water

Brackish water is water with a level of salinity between freshwater and seawater.

Brackish water contains between 0.5 and 30 grams of salt per liter.


Water that contains waste of humans, animals or food.


The amount of dissolved oxygen consumed in five days by bacteria that perform biological degradation of organic matter.

Bottled water

Water that is sold in plastic containers for drinking water and/ or domestic use.

Brackish water

Water that is neither falls in the category of salt water, nor in the category of fresh water. It holds the middle between either one of the categories.


Highly salty and heavily mineralised water, containing heavy metal and organic contaminants.


A substance that reacts with hydrogen or hydroxyl ions in a solution, in order to prevent a change in pH.



Solid dewatered residue on a filter media after filtration.


Chemical compounds related to carbon dioxide.

Carbonate hardness

Hardness of water caused by carbonate and bicarbonate by-products of calcium and magnesium.


A site in electrolysis where cations in solution are neutralized by electrons that plate out on the surface or produce a secondary reaction with water.


A negatively charged ion, resulting from dissociation of molecules in solution.


Colony Forming Units. This is a measure that indicates the number of microrganisms in water.

Chemical Oxygen Demand (COD)

The amount of oxygen (measured in mg/L) that is consumed in the oxidation of organic and oxidasable inorganic matter, under test conditions. It is used to measure the total amount of organic and inorganic pollution in wastewater. Contrary to BOD, with COD practically all compounds are fully oxidized.


A chemical complex that consists of chlorine and ammonia. It serves as a water disinfectant in public water supplies in place of chlorine because chlorine can combine with organics to form dangerous reaction products. In which forms chloramines exist depends on the physical/ chemical properties of the water source.


A water purification process in which chlorine is added to water for disinfection, for the control of present microrganisms. It is also used in the oxidation of compound impurities in water.

Chlorine-contact chamber

The part of a water treatment plant where effluent is disinfected by chlorine.


The clearness of a liquid.


Destabilisation of colloid particles by addition of a reactive chemical, called a coagulant. This happens through neutralization of the charges.

Coliform bacteria

Bacteria that serve as indicators of pollution and pathogens when found in water. These are usually found in the intestinal tract of humans and other warm-blooded animals.

Coliform index

A rating of the purity of water based on a count of coliform bacteria.


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

Combined sewer

A sewer system that carries both sewage and rain water runoff.


The amount of electricity the water can conduct. It is expressed in a chemical magnitude. Please use also our information about TDS and conductivity.

Contact time

The length of time a substance is in contact with a liquid, before it is removed by filtration or the occurrence of a chemical change.


Any foreign component in a substance, for example in water.

Conventional sewer systems

Systems that were traditionally used to collect municipal wastewater in gravity sewers and convey it to a central primary or secondary treatment plant, before discharge on receiving surface waters.

Cooling tower

Large tower used to transfer the heat in cooling water from a power or industrial plant to the atmosphere either by direct evaporation or by convection and conduction.

Cross flow filtration

A process that uses opposite flows across a membrane surface to minimize particle build-up.


A microorganism in water that causes gastrointestinal illness in humans. It is commonly found in untreated surface water and can be removed by filtration. It is resistant to disinfectants such as chlorine.


The accumulations of solids on a filter media that block it resist the water flow through the filter and increase the differential pressure.


Chemical Oxygen Demand – A water quality test that indirectly measures the amount of organic compounds in water (expressed in milligrams per liter).



The break down of organic matter by bacteria and fungi, to change the chemical structure and physical appearance of matter.


The removal of fluoride from drinking water to prevent teeth damage.

De-foaming agents

Chemicals that are added to wastewater discharges to prevent the water from foaming when it is discharged into a receiving water body.


The process of removing dissolved gasses from water, using vacuum or heat.


Process that serves to remove all ionised substances from a solution. Most commonly is the exchange process where cations and anions are removed independently of each other.


Processes to remove minerals from water, usually the term is restricted to ion exchange processes.


Demineralised water.Water that is treated to be contaminant-, mineral- and salt free.


Removal of nitrate and nitrate product from water to produce a quality that answeres common water standards.

Depth filtration

Treatment process in which the entire filter bed is used to trap insoluble and suspended particles in its voids as water flows through it.


The removal of salt from seawater or brackish water to produce drinking water, using various techniques.

Detention time

The actual time that a small amount of water is in a settling basin or flocculating basin. In storage reservoirs, it means the length of time water will be stored.


A component of the ozone contacting system in an ozone generator that allows diffusion of an ozone containing gas.


The movement of gas molecules or aerosols into liquids, caused by a concentration gradient.


A closed tank for wastewater treatment, in which bacterial action is induced to break down organic matter.


Fluids or gasses to disinfect filters, pipelines, systems, etc.


The decontamination of fluids and surfaces. To disinfect a fluid or surface a variety of techniques are used, such as ozone disinfection. Often disinfection means eliminating the present microrganisms with a biocide.


The process during which solid particles mix molecule by molecule with a liquid and appear to become part of the liquid.

Dissolved air flotation (DAF)

A procedure of induced flotation with very fine air bubbles or ‘micro bubbles’,

of 40 to 70 microns.

Dissolved oxygen

The amount of oxygen dissolved in water at a certain time, expressed in ppm mg/L.

Dissolved solids

Solids material that totally dissolves in water and can be removed by means of filtration.


Water treatment method where water is boiled to steam and condensed in a separate reservoir. Contaminants with higher boiling points than water do not vaporize and remain in the boiling flask.


Organic and inorganic suspended solids collected on the filter element. Quantity of debris is usually expressed in PPM. Size of it usually expressed in micron.


Density of a body is the ratio of its mass to its volume – A measure of how tightly the matter within the body is packed together.

Depth filtration

Removing and retaining suspended solids by means of their interception and adhering to grains or fibers (filtration media).

Differential Pressure

Defined as the difference in pressure between upstream (inlet side of the filter) and downstream (outlet side of the filter).


The German Institute for Standardization (DeutschesInstitut fur Normunge.V.); this institute establishes standards for testing and classifying filters.



The outlet or outflow of any system that deals with water flows, for an oxidation pond for biological water purification. It is the product water of the given system.


Substance that dissociates into ions when it dissolves in water.


Effective Filtration Area

The Total Area of the Filter Medium which is exposed to flow and is usable for the filtration process.


The filtered liquid leaving the filter


The device that performs the actual process of filtration


A process that uses electrical currents, applied to permeable membranes, to remove minerals from water.


Process where electrical energy will change in chemical energy. The process happens in an electrolyte, a watery solution or a salt melting which gives the ions a possibility to transfer between two electrodes. The electrolyte is the connection between the two electrodes, which are also connected to a direct current. If you apply an electrical current, the positive ions migrate to the cathode while the negative ions will migrate to the anode. At the electrodes, the cations will be reduced and the anions will be oxidated.

Eschericha coli (E. coli)

Coliform bacterium that is often associated with human and animal waste and is found in the intestinal court. It is used by health departments and private laboratories t measure the purity of water.


The process of the passage of water from liquid to vapour.

Evaporation ponds

Areas where sewage sludge is dumped and dried.


The loss of water from the soil through vaporizing, both by direct evaporation and by transpiration from plants.


Facultative bacteria

Bacteria that can live under aerobic or anaerobic conditions.

Filter medium

The permeable material that separates solids from liquids passing through it.


A liquid that has passed through the filter medium.


Separation of a solid and a liquid by using a porous substance that only lets the liquid pass through.


A flocculent mass that is formed in the accumulation of suspended particles. It can occur naturally, but is usually induced in order to be able to remove certain particles from wastewater.


The accumulation of destabilized particles and micro flakes, and subsequently the formation of sizeable flakes. One must ad another chemical called flocculent in order to facilitate the formation of flakes called flocs.


A device which removes particles from water by means of a physical barrier, chemical process and/or biological process

Filter area

The total area of a filter element, usually expressed in square inches or square centimeters

Filter Cake

The debris collected on the filter element, block it, resist the water flow through the filter and increase the differential pressure.


The process of removing solid particles from liquid or gas by forcing them through a porous medium

Filtration Degree

Size of pores in filtration medium (mm or microns)

Filtration Element

The active component of the filter, it determines the type of filter and the filtration level.

Filtration Velocity

Flow Rate / Cross Section Area [m/hr]


A flat metal ring with a hole in its center, through which a pipe passes, and with a number of smaller holes drilled circumferentially, destined for the connecting bolts.

Flow rate

Volume of water per unit of time


A solids-liquid or liquid-liquid separation procedure, which is applied to particles of which the density is lower than that of the liquid they are in. there are three types: natural, aided and induces flotation.


The rate at which a Reverse Osmosis Membrane allows water to pass through it.


The deposition of organic matter on the membrane surface, which causes inefficiencies.


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



A unit that is now almost entirely out of date. It is equivalent to 3.785 litres.


A microrganism that is commonly found in untreated surface water and can be removed by filtration. It is resistant to disinfectants such as chlorine.

Granular activated carbon

The heating of carbon to encourage active sites to absorb pollutants.

Grey Water

Domestic wastewater composed of wash water from kitchen, bathroom, and laundry sinks and from tubs, and washers.


Water that can be found in the saturated zone of the soil; a zone that consists merely of water. It slowly moves from places with high elevation and pressure to places with low elevation and pressure, such as rivers and lakes.

Groundwater discharge

Ground water entering coastal waters, which has been contaminated by land-fill leachates, deep well injection of hazardous wastes and septic tanks.


Gallons per minute


Hard water

Water that contains a great number of positive ions. The hardness is determined by the number of calcium and magnesium atoms present. Soap usually dissolves badly in hard water.

More info on hard water

Heat exchanger

A component that is utilized to remove heat from or ad heat to a liquid.

Heavy metals

Metals that have a density of 5.0 or higher and a high elemental weight. Most are toxic to humans, even in low concentrations.

Hydraulic gradient

In general, the direction of groundwater flow due to changes in the depth of the water table.

Hypo chlorite

An anion that forms products such as calcium and sodium hypo chlorite. These products are often used for disinfection and bleaching.


Indirect discharge

Introduction of pollutants from a non-domestic source into a publicly owned wastewater treatment system. Indirect dischargers can be commercial or industrial facilities whose wastes enter local sewers.


Penetration of water into a medium, for instance the soil.


The stream of water that enters any system or treatment unit.

In-line filter

A filter assembly in which the inlet, outlet and filter element axes are in a straight line.


An atom in a solution that is charged, either positively (cations) or negatively (anions).

Ion exchange

The replacement of undesirable ions with a certain charge by desirable ions of the same charge in a solution, by an ion-permeable absorbent.

Inorganic chemicals

Chemical substances of mineral origin, not of basically carbon structure.


Laboratory water

Purified water used in the laboratory as a basis to create solutions or making dilutions. It contains no interfering substances.


A shallow pond where sunlight, bacterial action, and oxygen work to purify wastewater.

Langelier Index (LI)

An index reflecting the equilibrium pH of a water with respect to calcium and alkalinity; used in stabilizing water to control both corrosion and scale deposition.


Water that contains solute substances, so that it contains certain substances in solution after percolation through a filter or soil.


The process by which soluble constituents are dissolved and filtered through the soil by a percolating fluid.


Common water treatment chemical. Lime can be deposed on walls of showers and bathrooms, after lime has reacted with calcium to form limestone.


Media filtration (depth filtration)

A thick layer of graded particles such as sand, gravel or other granular materials found inside filter housing and perform the filtration of water. The filtration rate depends on the effective size of the bedding and the water velocity through the filter.


The number of wires in a linear inch of a screen element

Mechanical aeration

Use of mechanical energy to inject air into water to cause a waste stream to absorb oxygen.

Mechanical flotation

A term used in the mineral industry to describe the use of dispersed air to produce bubbles that measure 0.2 to 2 mm in diameter.


Materials that form a barrier to the passage of certain suspended solids or dissolved liquids in filters.


A thin barrier that allows some compounds or liquids to pass through, and troubles others. It is a semi-permeable skin of which the pass-through is determined by size or special nature of the particles. Membranes are commonly used to separate substances.


Conversion of food, for instance soluble organic matter, to cellular matter and gaseous by-products through a biological process.


Microbial growth

The multiplication of microrganisms such as bacteria, algae, diatoms, plankton, and fungi.


A unit to discribe a measure of length, equal to one millionth of a metre.


Organisms that are so small that they can only be observed through a microscope, for instance bacteria, fungi or yeasts.

Municipal discharge

Discharge of effluent from wastewater treatment plants, which receive wastewater from households, commercial establishments, and industries in the coastal drainage basin.

Municipal sewage

Liquid wastes, originating from a community. They may have been composed of domestic wastewaters or industrial discharges.

Municipal Sludge

Semi liquid residue that remains from the treatment of municipal water and wastewater.


One millionth of a meter; known as a micrometer

Particles size is usually described in microns.

Multi-layer screen

A combination of selected ratios of weave type screens creating a mechanical strength



The addition of substances to neutralize water, so that it is neither acid, nor basic. Neutralization does not specifically mean a pH of 7.0, it just means the equivalent point of an acid-base reaction.


A biological process, during which nitrifying bacteria convert toxic ammonia to less harmful nitrate. It is commonly used to remove nitrogen substances from wastewater, but in lakes and ponds it occurs naturally.


Any substance that promotes growth with living organisms. The term is generally applied to nitrogen and phosphorus in wastewater, but is also applied to other essential and trace elements.

Nutrient Pollution

Contamination of water resources by excessive inputs of nutrients. In surface waters, excess algal production is a major concern.


Organic matter

Substances of (dead) plant or animal matter, with a carbon-hydrogen structure.


Water molecules passing through membranes naturally, to the side with the highest concentration of dissolved impurities.

Overflow rate

One of the guidelines for design of the settling tanks and clarifiers in a treatment plant to determine if tanks and clarifiers are used enough.


A chemical reaction in which ions are transferring electrons, to increase positive valence.

Oxidation pond

A man-made body of water in which waste is consumed by bacteria.

Oxidation-reduction potential

The electric potential required to transfer electrons from the oxidant to the reductant, used as a qualitative measure of the state of oxidation in water treatment systems.

Oxygen depletion

The reduction of the dissolved oxygen level in a water body.


An unstable oxidizing agent, that consists of three oxygen atoms and can be found in the ozone layer in the atmosphere. It is produced by electrical discharge through oxygen or by specifically designed UV-lamps.


Particle size

The sizes of a particle, determined by the smallest dimension, for instance a diameter. It is usually expressed in micron measurements.

Parts per billion

Expressed as ppb; a unit of concentration equivalent to the µg/l.

Parts per million

Expressed as ppm; a measure of concentration. One ppm is one unit weight of solute per million unit weights of solution. In water analysis the ppm is equivalent to mg/l.

Percolating water

Water that passes through rocks or soil under the force of gravity.


The ability of a medium to pass a fluid under pressure.


The value that determines if a substance is acid, neutral or basic, calculated from the number of hydrogen ions present. It is measured on a scale from 0 to 14, on which 7 means the substance is neutral. pH values below 7 indicate that a substance is acidic and pH values above 7 indicate that it is basic.

Physical and chemical treatment

Processes generally used in wastewater treatment facilities. Physical processes are for instance filtration. Chemical treatment can be coagulation, chlorination, or ozon treatment.


A contaminant at a concentration high enough to endanger the life of organisms.

Potable water

Water that is safe for drinking and cooking.


Point-Of-Use treatment.Water treatment at a limited number of outlets in a building, for less than the whole building.


An insoluble reaction product in an aqueous chemical reaction.

Particle Size Distribution

Defines which part of the TSS (Total Suspended Solids) is relevant to the desired filtration degree; Number Density or Volume Density.


Parts per million


Pounds per square inch – a pressure measurement unit


Removal of coarse particles or large debris prior to a finer filtration process


The preliminary treatment in the process of filtration (chemical of physical)


Measure of alkalinity or acidity


A channel or opening in a filter medium which allows passage of fluid


The ratio of pore volume to total volume of a filter medium expressed as a percentage.

Potable water

Water which is fit for consumption by humans and animals; it is also called drinking water. Water may be naturally potable or it may need to be treated in order to be safe.


The force over an area applied to an object in a direction perpendicular to the surface; usually expressed in pounds per square inch (PSI) or bar.


Pump (water pump)

A device which converts mechanical force and motion into hydraulic fluid power

Precipitation process

The altering of dissolved compounds to insoluble or badly soluble compounds, in order to be able to remove the compounds by means of filtration.


Processes used to reduce or eliminate wastewater pollutants from before they are discharged.

Primary wastewater treatment

The removal of suspended, floating and precipitated solids from untreated wastewater.

Click here for an overview of the wastewater treatment process

Process water

Water that serves in any level of the manufacturing process of certain products.



Putting the desired counter-ion back on the ion exchanger, by displacing an ion of higher affinity with one of lower affinity.

Reverse Osmosis process

The Reversed Osmosis (RO) process uses a semi-permeable membrane to separate and remove dissolved solids, organics, pyrogens, submicron colloidal matter, viruses, and bacteria from water. The process is called ‘reverse’ osmosis since it requires pressure to force pure water across a membrane, leaving the impurities behind.

Raw Water

Intake water prior to any treatment or use


Any natural or artificial holding area used to store, regulate, or control water.



The presence of soluble minerals in water.

Sand filtration

Sand filtration is a frequently used and very robust method to remove suspended solids from water. The filtration medium consists of a multiple layer of sand with a variety in size and specific gravity. Sand filters can be supplied in different sizes and materials both hand operated and fully automatically.


The precipitate that forms on surfaces in contact with water as the result of a physical or chemical change.


Use of screens to remove coarse floating and suspended solids from sewage.

Secondary treatment

The removal or reduction of contaminants and BOD of effluent from primary wastewater treatment.

Click here for an overview of the wastewater treatment process


Settling of solid particles in a liquid system due to gravity.


Soil, sand, and minerals washed from land into water, usually after rain.


A medium that allows water to pass through, but rejects dissolved solids, so that it can be used to separate solids from water.

Separate sewer

A sewer system that carries only sanitary sewage; no storm-water runoff. When a sewer is constructed this way, wastewater treatment plants can be sized to treat sanitary wastes only and all of the water entering the plant receives complete treatment at all times.


The isolation of the various compounds in a mixture.

Septic tank

An underground storage tank for wastes from homes not connected to a sewer line. Waste goes directly from the home to the tank.

Settleable solids

Those suspended solids in wastewater that will settle over a certain period of time and are removed in that way.


The process of sinking of a substance sinking in water. This occurs when the substance does not dissolve in water and its density is larger than that of water.


Waste fluid in a sewer system.

Sewage contamination

The introduction of untreated sewage into a water body.

Sewage sludge

Sludge produced in a public sewer.


The entire system of sewage collection, treatment, and disposal.


A semi-solid residue, containing microoroganisms and their products, from any water treatment process.


The removal of calcium and magnesium from water to reduce hardness.

Soft water

Any water that does not contain large concentrations of the dissolved minerals calcium or magnesium.


Removal of wastewater from a waste or changing it chemically to make it less permeable and susceptible to transport by water.

Screen (filter screen)

Perforated cylindrical body made of metal or plastic wedge-wire or woven-wire elements housed in a plastic or steel body.

Screen filtration

Mechanical filtration using a screen to remove particles out of water

Secondary treatment

The removal of organic matter from waste water in a sewage treatment plant using aerobic biological processes


Solid particles in water that settles out over time


The residual semi-solid material left from the filtration process.

Suction-scanning (Also known as focused back-flush)

Suction force that is created by reversing flow through a small section of the screen element into a nozzle at the tip of a rotating scanning element.

Surface Water

All water naturally opened to the atmosphere (rivers, lakes, reservoirs, ponds, streams, impoundments, seas, estuaries, etc.)


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


Matter dissolved in a liquid, such as water.

Surface water

All water naturally open to the atmosphere, concerning rivers, lakes, reservoirs, ponds, streams, impoundments, seas, estuaries and wetlands.

Suspended solids

Solid organic or inorganic particles that are held in suspension in a solution.


Tertiary treatment

Advanced cleaning of wastewater that goes beyond the secondary or biological stage, removing nutrients such as phosphorus, nitrogen, and most BOD and suspended solids.


An analytical technique to determine how much of a substance is present in a water sample by adding another substance and measuring how much of that substance must be added to produce a reaction.


Total Dissolved Solids.The weight per unit volume of water of suspended solids in a filter media after filtration or evaporation. Please use also our information about TDS and conductivity.


Total Hardness. The sum of calcium and magnesium hardness, expressed as a calcium carbonate equivalent.


Total Solids.The weight of all present solids per unit volume of water. It is usually determined by evaporation. The total weight concerns both dissolved and suspended organic and inorganic matter.

Tertiary Treatment

Advanced cleaning of wastewater that goes beyond the secondary or biological stage, removing nutrients such as phosphorus, nitrogen, and most BOD and suspended solids

TDS – Total Dissolved Solids

An expression for the substances contained in a liquid which are present in a molecular, ionized or micro-granular suspended form. The operational definition is that the solids must be small enough to pass through a two microns filter. The term is used as an indirect reflection of water salinity. The term is also known as total filterable residue.


The cloudiness or haziness of a fluid caused by suspended solids particles that are generally invisible to the naked eye, similar to smoke in air.

The measurement of turbidity is a key test of water quality and it is measured by the amount of Light transmission through a water sample.

Total Suspended Solids – TSS (in water filtration)

The total Concentration of Dirt Load in water; measured in milligrams per liter or PPM (parts per million).

Treatment Plant

A structure built to treat wastewater before discharging it into the environment.

Total solids

All the solids in wastewater or sewage water, including suspended solids and filterable solids.

Treatment plant

A structure built to treat wastewater before discharging it into the environment.

Trickling filter

A wastewater treatment unit that contains medium material with bacteria. The stream of wastewater is trickled over the medium and the bacteria break down the organic wastes. Bacteria are collected on the filter medium.

Tube settler

Device using bundles of tubes to let solids in water settle to the bottom for removal by sludge.


A measure of non-transparency of water due to the presence of suspended matter.

Turbulent flow

A flow that contains may rapid fluctuations.


Ultra-violet oxidation

A process using extremely short wave-length light that can kill micro-organisms (disinfection) or cleave organic molecules (photo oxidation) rendering them polarized or ionized and thus more easily removed from the water.


Ultra Violet.Radiation that has a wavelength shorter than visible light. It is often used to kill bacteria and destroy ozone.



Volatile Organic Compound.Synthetic organic compounds which easily vaporize and are often carcinogenic.

Vapor Pressure

The pressure at which water evaporates at a given temperature; the temperature at which the vapor pressure is equal to the atmospheric pressure is called the boiling point


The resistance of a fluid to flow, caused by internal friction between the fluid molecules and by intermolecular forces (M2/sec)



The spent or used water from a home, community, farm, or industry that contains dissolved or suspended matter.

Water pollution

The presence in water of enough harmful or objectionable material to damage water quality.


A spill over device used to measure or control water flows.

Wastewater The spent or used water from a home, community, farm, or industry that contains dissolved or suspended matter.


Zero discharge water (ZLD)

The principle of “zero discharge” is recycling of all industrial wastewater. This means that wastewater will be treated and used again in the process. Because of the water reuse wastewater will not be released on the sewer system or surface water.


STP – Sewage Treatment Plant

WWTP (Wastewater Treatment Plant)

LWT (Laundry Water Treatment Plant)

GWT (Grey Water Treatment Plant)

BWT (Black Water Treatment Plant)

WTP (Water Treatment Plant)

RO Plant (Reverse Osmosis Plant)

DM Plant (Demineralization Plant)

SOF (Water Softener)

MBBR (Moving Bed Bioreactor)

SAFF (Submerged aerated fixed film Reactor)

MBR (Membrane Bioreactor)

FAB (fluidize Aerobic bioreactor)

FMR (Fluidize Media Reactor)

SBR (Sequential Batch Reactor)

Resin (ion exchange molecule for water treatment)

Media filter

PSF (Pressure Sand Filter)

DMF (Dual media filter)

MGF (Multi Grade Filter)

SSF (Side Stream Filter)

ETP (Effluent Treatment Plant)

RSF (Rapid Sand Filter)