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

Absorption 
When a solid takes up molecules into its structure.

Acidic water 
Acid neutralizing capacity 
Measure of the buffering capacity of water; the ability of water to resist changes in pH.

Acidity 
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 Carbon 
is the primary material used in point of use/point of entry (POU/POE) water treatment devices for the control of chlorine, taste and odor. The advantage of activated carbon is its broad spectrum capacity to adsorb organic chemicals and promote catalytic/chemical reduction of chlorine disinfectants, both of which contribute to bad taste in potable water.

Adsorption
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)

Aeration
Technique that is used with water treatment that demands oxygen supply, commonly known as aerobic 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.

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

Aggressive water
Water that is soft and acidic and can corrode plumbing, pipes and appliances.

Algal blooms 
Periods of enlarged algal growths that affect water quality. Algal blooms indicate potentially hazardous changes in the chemistry of water.

Alkalinity 
Alkalinity means the buffering capacity of water or 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.

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.

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

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

Anode
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.

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

Aquifer
A layer in the soil that is capable of transporting a significant volume of groundwater.

Aromatics 
A type of hydrocarbon that contains a ring structure, such as benzene and toluene. They can be found for instance in gasoline.

Attenuation 
The process of reduction of a compound's concentration over time. This can be through absorption, adsorption, degradation, dilution or transformation.

Attrition
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.

Backflow 
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.

Backwashing
Reversing the flow of water back through the filter media to remove entrapped solids such in a water softener or backwashing iron filter.

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

Bacterial water contamination
The introduction of unwanted bacteria into a body of water.

Base
An alkaline substance that has a pH that exceeds 7.5.

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

Binder 
Chemicals that hold short fibres together in a cartridge filter.

Biocide
A chemical that is toxic to microrganisms. Biocides are often used to eliminate bacteria and other single-cell organisms from water. Examples... Chlorine, dioxide and Ozone.

Biofilm
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 and fungi 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.

Biomonitoring 
The use of living organisms to test the suitability of effluents for discharge into receiving waters and to test the quality of such waters downstream from the discharge.

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

Biota
All living organisms in a region or ecosystem.

Biotransformation 
Conversion of a substance into other compounds by organisms; including biodegradation.

Blackwater 
Water that contains waste of humans, animals or food.

Blind spots 
Any place on a filter medium where fluids cannot flow through.

Blinding
A build-up of particles in a filter medium, that prevents fluids from flowing through.

BOD5 
The amount of dissolved oxygen consumed in five days by bacteria that perform biological degradation of organic matter.

Boiling point
The temperature at which the vapour pressure of a liquid equals the pressure of its surface. The liquid will than vaporize If the pressure of the liquid varies, the actual boiling point varies. For water the boiling point is 100 degrees Celsius.

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.

Breakpoint chlorination
Addition of chlorine to water until there is enough chlorine present for disinfection of water.

Breakthrough
Crack or break in a filter bed that allows the passage of floc or particulate matter through a filter.

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

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

Cake 
Solid dewatered residue on a filter media after filtration.

Calcium hypo chlorite
A chemical that is widely used for water disinfection, for instance in swimming pools or water purification plants. It is especially useful because it is a stable dry powder and can be made into tablets.

Candle filter
A relatively coarse aperture filter, designed to retain a coat of filter medium on an extended surface.

Capillary action
Water that at some point rises higher than that portion of its surface, not in contact with the solid surface. This is due to adhesion, cohesion and surface tension where later touches a solid.

Cappilary membranes
Membranes about the thickness of a human hair, used for Reverse Osmosis, nanofiltration, ultrafiltration and microfiltrtion.

Capillary zone
Soil area above the water table where water can rise up slightly through the cohesive force of capillary action.

Carcinogen
Any dissolved pollutant that can induce cancer.

Cartridge filter
Disposable filter device that has a filter range of 0.1 micron to 100 microns.

More info on cartridge filters

Carbonates
Chemical compounds related to carbon dioxide.

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

Catalyses
Chemical that increases the rate of a reaction but does not take a direct part in the reaction, so that it is still intact after the reaction has taken place.

Cathode
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.

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

Check valve
A valve that allows water to stream in one direction and will then close to prevent development of a back-flow.

Chelating agents
Organic compounds that have the ability to draw ion from their water solutions into soluble complexes.

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.

Chemical pollution
Introduction of chemical contaminants into a water body.

Chloramines
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.

Chlorination
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.

Clarity
The clearness of a liquid.

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

More info on coagulation

Coalescence
Liquid particles in suspension that unite to create particles of a greater volume.

Coastal zone
Lands and waters near the coast, whose uses and ecology are affected by the sea.

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.

Collector sewers
Pipes to collect and carry wastewater from individual sources to an interceptor sewer that will carry it to a treatment facility.

Colloids
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.

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

Compounds
Two or more different elements held together in fixed proportions by attractive forces called chemical bonds.

Concentrate
The totality of different substances that are left behind in a filter medium after filtration.

Concentration
The amount of material dissolved in a unit of solution, expressed in mg/L.

Concentration process
The process of increasing the number of particles per unit volume of a solution, usually by evaporating the liquid.

Conductivity
The amount of electricity the water can conduct. It is expressed in a chemical magnitude.

Consumptive water use
Water removed from available supplies without return to a water resources system; water used in manufacturing, agriculture, and food preparation.

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.

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

Corrosivity
Ability of water to dissolve or break down certain substances, particularly metals.

Cryptosporidium
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.

Dealkalinisation 
Any process that serves to reduce the alkalinity of water.

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

Defluoridation
The removal of fluoride from drinking water.

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

Deionisation
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.

Demineralisation
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.

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.

Desalination
The removal of salt from seawater or brackish water to produce drinking water, using various techniques such as reverse osmosis.

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

Disinfection
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.

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

Dissolved oxygen
The amount of oxygen dissolved in water, expressed in ppm mg/L.

Dissolved solids
Solids material that totally dissolves in water and can be removed by means of filtration or reverse osmosis.

Distillation
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.

Electrical charge
The charge on an ion, declared by its number of electrons. A Cl- ion is in fact a Cl atom which has acquired an electron, and a Ca++ ion is a Ca atom, which has lost two electrons.

Electrolyte
Substance that dissociates into ions when it dissolves in water.

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

Electrolysis
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.

Electrons
Negatively charged building blocks of an atom that circle around the nucleus.

Elements
The distinctive building blocks of matter that make up every material substance.

Emulsifier
A chemical that helps suspending one liquid in another.

Emulsion
Dispersion of one liquid in another liquid, occurs when a liquid in insoluble.

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.

Estuary
Region of interaction between rivers and near-shore ocean waters, where tidal action and river flow mix fresh and salt water. Therefore estuaries mainly consist of brackish water.

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

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

Extruded activated carbon filters 
consist of virgin carbon powder, a thermoplastic binder, and speciality adsorbents such as zeolites or oxidizing filtration media. Carbon block filter cartridges are usually in the form of a thick-walled pipe where the water is forced to pass from the outside to the inside of the porous wall. During their passage through the wall of the device, the fluid contaminants are adsorbed, intercepted, or chemically reacted to provide a highly refined final fluid product.

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

Filtrate
A liquid that has passed through the filter medium.

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

Flow Rate
The discharge rate of a water, expressed in volume during a certain period of time. exp 10 Gallons per minute

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

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

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

Giardia
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.

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

Groundwater
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.

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 is does not dissolve easily in hard water.

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.

Hydrocarbon
Organic compounds that are built of carbon and hydrogen atoms and are often used in petroleum industries.

Hydroelectric power water use
The use of water in the generation of electricity at plants where the turbine generators are driven by falling water.

Hydrogen sulfide (H2S)
A gas emitted during organic decomposition by a select group of bacteria, which strongly smells like rotten eggs (sulfur water).

Hydrolysis
The decomposition of organic compounds by interaction with water.

Hydrosphere
Region that includes all the earth's liquid water, frozen water, floating ice, frozen upper layer of soil, and the small amounts of water vapour in the atmosphere.

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

Ice
The solid form of water.

Impermeable
Not easily penetrated by water.

Impurities
Particles or other objects that cause water to be unclear.

Injection
The introduction of a chemical or medium into the process water to alter its chemistry or filter specific compounds.

Ion
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.

Lake
An inland body of water, usually fresh water, formed by glaciers, river drainage, etc. It is usually larger than a pool or pond.

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

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

Leakage
A species of ions in the feed of an ion exchanger present in the effluent.

Light absorption
The amount of light a certain amount of water can absorb over time.

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

Limnology
The study of the physical, chemical, hydrological, and biological aspects of fresh water.

Liquid
A state of matter, neither gas nor solid, that flows and takes the shape of its container.

Maximum Contaminant Level (MCL)
The maximum level of a contaminant allowed in water by federallaw. Based on health effects and currently available treatment methods.

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

Media
Materials that form a barrier to the passage of certain suspended solids or dissolved liquids in filters. exp... melt blown polypropelene and activated carbon are filter medias 

Membrane
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. A reverse osmosis membrane is a semipermiable membrane.

Micro Filtration 
The principle of micro filtration is physical separation. The extent to which dissolved solids, turbidity and microrganisms are removed is determined by the size of the pores in the membranes. Substances that are larger than the pores in the membranes are fully removed. Substances that are smaller than the pores of the membranes are partially removed, depending on the construction of a refuse layer on the membrane. Micro filtration is a pressure-dependent processes, which remove dissolved solids and other substances from water to a lesser extend than nano filtration and Reverse Osmosis with a pore size of  0.1 – 10 µm.  
exp... 
Pretreatment of reverse osmosis water
Clearing of fruit juice, wines and beer
Solid liquid separation for pharmacies or food industries

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

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

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

Mineral Water
Contains large amounts of dissolved minerals such as calcium, sodium, magnesium, and iron. Some tap waters contain as many or more minerals than some commercial mineral waters. There is no scientific evidence that either high or low mineral content water is beneficial to humans.

Mixture
Various elements, compounds or both, that are mixed.

Molecules
Combinations of two or more atoms of the same or different elements held together by chemical bonds.

Neutralization 
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.

Neutrons
Uncharged building blocks of an atom that play a part in radio-activity. They can be found in the nucleus.

Non-potable
Water that is unsafe or unpalatable to drink because it contains pollutants, contaminants, minerals or infective agents.

Nucleus
The center of an atom, that contains protons and neutrons and carries a positive charge.

Nuisance Contaminant
Constituents in water, which are not normally harmful to health but may cause offensive taste, odor, color, corrosion, foaming, or staining.

Nutrient
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.

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

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

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

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

Ozone
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.

Ozone generator
A device that generates ozone by passing a voltage through a chamber that contains oxygen. It is often used as a disinfection system. Ozone has a much shorter required contact time than many othe disifectants.

Parameter
A variable, measurable property whose value is a determinant of the characteristics of a system such as water. Temperature, pressure, and density are examples of parameters.

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

Particulate loading
The mass of particulates per unit volume of water.

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.

Pasteurisation
The elimination of microrganisms by heat applies for a certain period of time.

Pathogens
Disease-producing microrganisms.

Percent saturation
The amount of a substance that is dissolved in a solution compared to the amount that could be dissolved in it.

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

pH
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.

Photosynthesis
The process of conversion of water and carbon dioxide to carbohydrates. It takes place in the presence of chlorophyll and is activated by sunlight. During the process oxygen is released. Only plants and a limited number of microrganisms can perform photosynthesis.

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.

POE-treatment
Point-Of-Entry treatment. Total water treatment at the inlet to an entire building or facility. A water softener or whole house filter would be an example of POE water treatment.

Pore
An opening in a membrane or medium that allows water to pass through.

Polar substance
A substance that carries a positive or negative charge, for instance water.

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

Potable water
Water that is safe for drinking and cooking.

Potentiation
The ability of one chemical to increase the effect of another chemical.

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

Precipitate
An insoluble reaction product in an aqueous chemical reaction.

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.

Product water
Water that has passed through a water treatment system and is ready to be used. exp... water that has been treated by a reverse osmosis membrane

Protons
Positively charged building blocks of an atom that are centered in the nucleus.

Protozoa
Large microrganisms, which consume bacteria.

Public water system
A system that provides piped water for human consumption to at least 15 service connections or regularly serves 25 individuals.

Putrefaction
Biological decomposition of organic matter; associated with anaerobic conditions.

Pyrogen
Substance that is produces by bacteria and it fairly stable. It causes fever in mammals.

Qualitative water assessment
Analyses of water used to discribe the visible or aestetic charcteristics of water.

Quantitative water assessment
Use of analyses of water properties and concentrations of compounds and contaminants in order to define water quality.

Raw water
Intake water before any treatment or use.

Recarbonization
Process in which carbon dioxide is bubbled into treatment water in order to lower the pH.

Redox
Shortened term for reduction/ oxidation reactions. Redox reactions are a series of reactions of substances in which electron transfer takes place. The substance that gains electrons is called oxidising agent.

Reduction
A chemical reaction in which ions gain electrons to reduce their positive valence.

Regeneration
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 Reverse 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.

Reverse Osmosis Membrane
A Semi-permeable membrane used in water treatment to separate dissolved solids, salts and minerals from water through pressure reversing the osmotic flow.  Used in reverse osmosis systems. 

Safe water
Water that does not contain harmful bacteria, toxic materials, or chemicals, and is considered safe for drinking.

Salinity
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.

Saturation
The condition of a liquid when it has taken into solution the maximum possible quantity of a given substance.

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

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

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

Semipermeable
A medium that allows water to pass through, but rejects dissolved solids, so that it can be used to separate solids from water.  A reverse osmosis membrane is semipermeable.

Separation
The isolation of the various compounds in a mixture.

Softening
The removal of calcium and magnesium from water to reduce hardness usually with a water softener.

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

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

Solute
Matter dissolved in a liquid, such as water.

Solvent
Substance (usually liquid) capable of dissolving one or more other substances.

Specific conductance
Method to estimate the dissolved solid content of a water supply by testing its conductivity.

Spring
Ground water seeping out of the earth where the water table exceeds the ground surface.

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.

Titration
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.

TDS
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.

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

TS
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.

Toxic water pollutants
Compounds that are not naturally found in water at the given concentrations and that cause death, disease, or birth defects in organisms that ingest or absorb them.

Transmission lines
Pipelines that transport raw water from its source to a water treatment plant.

Transmissivity
The ability of an aquifer to transmit water.

Transpiration
The process by which water vapour is released into the atmosphere after transpiring of living plants.

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

THM
Trihalomethanes. Toxic chemical substances that consist of a methane molecule and one of the halogen elements fluorine, bromine, chlorine and iodine attached to three positions of the molecule. They usually have carcinogenic properties.

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

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.

Unloading
The release of the contaminant that was captured by a filter medium.

Up-flow
An upward flow of water.

UP-water
Ultra pure water creation demands a specialised way of working. A number of techniques are used amongst others; membrane filtration, ion exchanges, sub micron filters, ultra violette and ozone systems. The produced water is extremely pure and contains none to very low concentrations of salts, organic/ pyrogene components, oxygen, suspended solids and bacteria.

Urban run-off
Water from city streets domestic properties that carries pollutants into the sewer systems and receiving waters.

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

Vapour
The gaseous phase of substances such as water.

Vaporize
Conversion of a liquid into vapour.

Venturi
A channel that serves the measurement of water flows.

Viruses
The smallest life forms known, that are not cellular in nature. They live inside the cells of animals, plants and bacteria and often cause disease. They are made up of a chromosome surrounded by a protein shell.

Viscosity
The syrupiness of water and it determines the mobility of the water. When the temperature rises, the viscosity degrades; this means that water will be more mobile at higher temperatures.

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

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

Water monitoring
The process of constant control of a body of water by means of sampling and analyses.

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

Water quality
The condition of water with respect to the amount of impurities in it.

Water recycling
Using water again for the same or another process step, after a small form of purification is applied.

Watershed
A land area from which water drains to a particular water body.

Water solubility
The maximum possible concentration of a chemical compound dissolved in water.

Water storage pond
An impound for liquid wastes designed to accomplish some degree of biochemical treatment.

Water supply system
The collection, treatment, storage, and distribution of water from source to consumer.

Water system
A river and all its branches.

Water table
The surface of groundwater in the soil.

Well
A deep hole with the purpose to reach underground water supplies.

Zero discharge water 
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.

Zone of saturation
The space in the soil below the water table in which all the pores are filled with water. The water in the zone of saturation is groundwater.