An explanation of terminology concerning water related
issues
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FAQ's
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.
Acid aerosol
Very small liquid or solid particles that are acidic and are small enough
to become airborne.
Acid neutralizing capacity
Measure of the buffering capacity of water; the ability of water to
resist changes in pH.
Rain that has a flamboyantly low pH, due to contact with atmospheric
pollutants such as sulphuric oxides.
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 coal
This is the most commonly used adsorption medium, produced by heating
carbonaceous substances or cellulose bases in the absence of air. It has
a very porous structure and is commonly used to remove organic matter
and dissolved gases from water. Its appearance is similar to coal or peat.
Available in granular, powder or block form; in powder form it has the
highest adsorption capacity.
Activated sludge
Oxygen dependent biological
process that serves to convert soluble organic matter to solid biomass,
that is removable by gravity or filtration.
Active groups
Really fixed ions bolted on to the matrix of an ion exchanger. Each
active group must always have a counter-ion of opposite charge near itself.
Adsorption
Separation of liquids, gases, colloids or suspended matter from a medium
by adherence to the surface or pores of a solid.
More info on adsorption
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)
More info on advanced oxidation
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
such as 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.
Aeration
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.
More info on aeration
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.
Aerosol
Very small liquid or solid particles dispersed in air.
Affinity
The keenness with which an ion exchanger takes up and holds on to a counter-ion.
Affinities are very much affected by the concentration of the electrolyte
surrounding the ion exchanger.
Agglomeration
A process of bringing smaller particles together to form a larger mass.
Aggressive water
Water that is soft and acidic and can corrode plumbing, pipes and appliances.
Algae
Single- or multi-celled organisms that are commonly found in surface
water, such as duckweed. They produce their own food through photosynthesis.
The algae population is divided up into green algae and blue algae, of
which the blue algae are very damageable to human health. Excessive algae
growth may cause the water to have undesirable odours or tastes. Decay
of algae diminishes oxygen
supplies in the water.
Algal blooms
Periods of enlarged algal growths that affect water quality. Algal blooms
indicate potentially hazardous changes in the chemistry of water.
Aliquot
A measured portion of a sample taken for analysis. One or more aliquots
make up a sample.
Alkalinity
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.
Alluvium
Sediments deposited by erosion processes, usually by streams.
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.
Aquatic
Growing in water, living in water, or frequenting water.
Aqueous
Something made up of water.
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.
Assimilation
The ability of water to purify itself of pollutants.
Assimilative Capacity
The capacity of natural water to receive wastewaters or toxic materials
without negative effects and without damage to aquatic life or humans
who consume the water.
Atom
The smallest unit of matter that is unique to a particular element.
They are the ultimate building blocks for all matter.
Atomic number
A specific number that differs for each element, equal to the number
of protons in the nucleus of each of its atoms.
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.
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.
Back siphonage
Reverse seepage of water in a distribution system.
Backwashing
Reversing the flow of water back through the filter media to remove
entrapped solids.
Bacteria
Microscopically small single-cell organisms, that reproduce by fission
of spores.
The introduction of unwanted bacteria into a water body.
Base
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.
Benthic zone
The lower region of a body of water including the bottom.
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.
Bioaccumulantion
The increase in concentration of a substance in living organisms, as
they take in contaminated air, water, or food, due to slow metabolization
and excretion.
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.
More info on BOD and waste water treatment
Biocide
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.
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, 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.
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.
Solid dewatered residue on a filter media after filtration.
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.
Catch basin
A sedimentation area designed to remove pollutants from runoff before
being discharged into a stream or pond.
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.
Centrifugation
A separation process, which uses the action of centrifugal force to
promote accelerated settling of particles in a solid-liquid mixture.
More info on centrifugation
CFU
Colony Forming Units. This is a measure that indicates the number of
microrganisms in water.
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.
Chemical weathering
Dissolving of rock by exposure to rainwater, surface water, oxygen,
and other gases in the atmosphere, and compounds secreted by organisms.
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.
Chlorinated hydrocarbons
Hydrocarbons that contain chlorine. These include a class of persistent
insecticides that accumulate in the aquatic food chain. Among them are
DDT, aldrin, dieldrin, heptachlor, chlordane, lindane, endrin, Mirex,
hexachloride, and toxaphene.
Chlorinated solvent
An organic solvent containing chlorine atoms that is often used as aerosol
spray container, in highway paint, and dry cleaning fluids.
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.
Chlorine-contact chamber
The part of a water treatment plant where effluent is disinfected by
chlorine.
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.
Condensate
Water obtained by condensation of water vapour.
Condensation
The change of state from a gas to a liquid.
The amount of electricity the water can conduct. It is expressed in
a chemical magnitude. Please use also our information about TDS
and conductivity.
Conduit
A natural or artificial channel through which fluids may be transported.
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.
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.
Conveyance loss
Water loss in pipes and channels by leakage or evaporation.
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.
Corrosivity
Ability of water to dissolve or break down certain substances, particularly
metals.
Cross flow filtration
A process that uses opposite flows across a membrane surface to minimize
particle build-up.
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.
Cultural eutrophication
Decline of the oxygen
rate in water, which has serious consequences for aquatic life, caused
by humans.
Current
The portion of a stream or body of water, which is moving much faster
than the rest of the water. The progress of the water is principally concentrated
in the current.
Cycle
The length of time a filter can be used before it needs cleaning, usually
including cleaning time.
Any process that serves to reduce the alkalinity of water.
Decarbonation
The process of removing carbon
dioxide from water, using contact towers or air scrubbers.
Decant
To draw off the upper layer of liquid after the heaviest material (a
solid or another liquid) has settled.
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 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.
Degasification
The process of removing dissolved gasses from water, using vacuum 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.
Demiwater
Demineralised water. Water that is treated to be contaminant-, mineral-
and salt free.
Denitrification
Removal of nitrate and nitrate product from water to produce a quality
that answeres common water standards.
The weight of a certain amount of water. It is usually expressed in
kilograms per cubic metre.
Depression storage
The storage of water in low areas, such as ponds, and wetlands.
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.
Desorption
The opposite of adsorption; the release of matter from the adsorption
medium, usually to recover material.
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.
Detergent
A water-soluble cleansing agent, other than soap.
Dewater
The separation of water from sludge, to produce a solid cake.
Diffuser
A component of the ozone contacting system in an ozone generator that
allows diffusion of an ozone containing gas.
Diffusion
The movement of gas molecules or aerosols into liquids, caused by a concentration
gradient.
Digester
A closed tank for wastewater treatment, in which bacterial action is
induced to break down organic matter.
Diluting water
Distilled water that has been stabilized, buffered, and aerated. It is
often applied in the BOD tests.
Direct run-off
Water that flows from the ground surface directly into streams, rivers,
and lakes.
Discharge
Flow of surface water in a stream or canal.
Disinfectants
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.
More info on disinfection
Dissolve
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.
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.
Dredging
Cleaning, deepening, or widening of a waterway, using a machine (dredge)
that removes materials by means of a scoop or a suction device.
Drought
Term applied to periods of less than average precipitation over a certain
period of time.
Duplicates
Two separate samples with separate containers taken at the same time
and at the same place.
Dystrophic lakes
Acidic bodies of water that contain many plants but few fish, due to
the presence of great amounts of organic matter.
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.
Ejector
A device used to inject a chemical solution into wastewater during water
treatment.
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.
Elutriation
Freeing sludge of its mother liquor by washing it with water.
Emulsifier
A chemical that helps suspending one liquid in another.
Emulsion
Dispersion of one liquid in another liquid, occurs when a liquid in insoluble.
End-of-pipe techniques
Techniques for water purification that serve the reduction pollutants
after they have formed.
Enrichment
When the addition of nutrients, such as
nitrogen and phosphorus,
from sewage effluent or agricultural runoff to surface water, greatly
increases algal growth.
Erosion
The wearing away of the land surface by wind, water, ice or other geological
agents. Erosion occurs naturally from weather or runoff but is often intensified
by human land use practices.
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.
Eutrophic
Referring to water that is rich in nutrients such as nitrogen and phosphorous.
Eutrophication
Enrichment of water, which causes excessive growth of aquatic plants
and increasing activity of anaerobic microrganisms. As a result the
oxygen levels in the water quickly decline and the water chokes, making
life impossible for aerobic water organisms.
Evaporation
The process of the passage of water from liquid to vapour.
Evaporation ponds
Areas where sewage sludge is dumped and dried.
Evapotranspiration
The loss of water from the soil through vaporizing, both by direct evaporation
and by transpiration from plants.
Bacteria that can live under aerobic or anaerobic conditions.
Fermentation
The conversion of organic matter to methane,
carbon dioxide and other molecules by anaerobic bacteria.
Filter medium
The permeable material that separates solids from liquids passing through
it.
Filtrate
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.
First draw
The water that comes out when a tap is first opened. It is likely that
is has the highest level of lead contamination from weathering of pipelines.
Fission
Reproduction of microrganisms by means of cell division.
Floc
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.
Flocculation
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.
More info on flocculation
Floodplain
The flat or nearly flat land along a river or stream that is covered
by water during a flood.
Flotation
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.
Flow
The discharge rate of a resource, expressed in volume during a certain
period of time.
Flow augmentation
The addition of water to meet flow needs.
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.
Fragmentation
The subdivision of a solid in fragments. The fragments will then adhere
to the nearest surface.
Freezing
The change of a liquid into a solid as temperature decreases. For water,
the freezing point is 0 degrees Celsius.
Freshwater
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.
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.
Groundwater discharge
Ground water entering coastal waters, which has been contaminated by
land-fill leachates, deep well injection of hazardous wastes and septic
tanks.
Groundwater hydrology
The branch of hydrology that deals with the occurrence, movements, replenishment
and depletion, properties and methods of investigation and utilisation
of groundwater.
Gully
A deeply eroded channel created by the concentrated flow of water.
The time required for a pollutant to lose one-half of its original concentraton.
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.
More info on heavy metals
Heavy water
Water in which all the hydrogen
atoms have been replaced by deuterium.
Henry's Law
A way of calculating the solubility of a gas in a liquid, based on temperature
and partial pressure, by means of constants.
Holding Pond
A pond or reservoir, usually made of earth, built to store polluted
runoff.
Homeowner water system
A water system that supplies piped water to a single residence.
Humidification
The addition of water vapour to air.
Hydraulic conductivity
The rate at which water can move through a permeable medium.
Hydraulic gradient
In general, the direction of groundwater flow due to changes in the
depth of the water table.
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.
Hydrogeology
The science of chemistry and movement of groundwater.
Hydrograph
A chart that measures the amount of water flowing past a point as a function
of time.
Hydrolysis
The decomposition of organic compounds by interaction with water.
Hydrologic cycle
The natural cycle of water passing through the environment, including
evaporation, condensation, retention and run-off.
Hydrophilic
Having an affinity for water.
Hydrophobic
Having an aversion for 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.
Hypoxic waters
Waters with dissolved oxygen
concentrations of less than 2 mg/L, the level generally accepted as the
minimum required for life and reproduction of aquatic organisms.
The solid form of water.
Imhoff cone
A clear, cone-shaped container used to measure the volume of settle
able solids in a specific volume of water.
Immiscibility
The inability of two or more solids or liquids to readily dissolve into
one another.
Impermeable
Not easily penetrated by water.
Impurities
Particles or other objects that cause water to be unclear.
Indicator
Any biological entity or process, or community whose characteristics
show the presence of specific environmental conditions or pollutants.
Indicator organisms
Microrganisms, such as coliforms, whose presence is indicative for pollution
or for the presence more harmful microrganisms.
Indicator tests
Tests for a specific contaminant, group of contaminants, or constituent
which signals the presence of something else.
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.
Infiltration
Penetration of water into a medium, for instance the soil.
Influent
The stream of water that enters any system or treatment unit.
Inhibitor
chemical that interferes with a chemical reaction, such as precipitation.
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.
More info on ion exchange
Inorganic chemicals
Chemical substances of mineral origin, not of basically
carbon structure.
Irrigation
Applying water or wastewater to land areas to supply the water and nutrient
needs of plants.
A laboratory test procedure with differing chemical doses, mix speeds,
and settling times, to estimate the minimum or ideal coagulant dose required
to achieve water quality goals.
Energy possessed by moving water.
Kinetic rate coefficient
A number that describes the rate at which a water constituent such as
a biochemical oxygen demand
or dissolved oxygen rises
or falls.
Purified water used in the laboratory as a basis to create solutions
or making dilutions. It contains no interfering substances.
Lagoon
A shallow pond where sunlight, bacterial action, and
oxygen work to purify wastewater.
Lake
An inland body of water, usually fresh water, formed by glaciers, river
drainage, etc. It is usually larger than a pool or pond.
Laminar flow
A flow in which rapid fluctuations are absent.
Land Application
Discharge of wastewater onto the ground for treatment or reuse.
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.
Large water system
A water system that services more than 50,000 customers.
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.
The maximum level of a contaminant allowed in water by federal law. 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.
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.
Media
Materials that form a barrier to the passage of certain suspended solids
or dissolved liquids in filters.
Medium-size water system
A water system that serves 3,300 to 50,000 customers.
Melting
The change of a solid into a liquid.
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.
Mesotrophic
Reservoirs and lakes which contain moderate quantities of nutrients
and are moderately productive in terms of aquatic animal and plant life.
Metabolise
Conversion of food, for instance soluble organic matter, to cellular
matter and gaseous by-products through a biological process.
MFS
Micro Filtration System, it serves full automatic solid/ liquid separation.
More info on MFS
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.
Miscibility
The ability of two liquids to mix.
Mist
Liquid particles measuring 40 to 500 micrometers, are formed by condensation
of vapour. By comparison, fog particles are smaller than 40 micrometers.
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.
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.
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.
Nitrification
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.
Non-point sources
Diffuse water pollution sources without a specific point of origin.
The pollutants are generally carried off the land by storm water. Common
non-point sources are agriculture and atmospheric disposal.
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.
Nutrient Pollution
Contamination of water resources by excessive inputs of nutrients. In
surface waters, excess algal production is a major concern.
Deep clear lakes with few nutrients, little organic matter and a high
dissolved-oxygen level.
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.
Outfall
The place where a wastewater treatment plant discharges treated water
into the environment.
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.
Oxidation
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.
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.
More info on ozone and ozone generators
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.
Partial pressure
That pressure of a gas in a liquid, which is in equilibrium with the
solution. In a mixture of gases, the partial pressure of any one gas is
the total pressure times the fraction of the gas in the mixture (by volume
or number of molecules).
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.
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.
Percolating water
Water that passes through rocks or soil under the force of gravity.
Periodic chart
Arrangement of elements in order of increasing atomic numbers, created
by a scientist called Mendelejef.
Permeability
The ability of a medium to pass a fluid under pressure.
Persistence
Refers to the length of time a compound stays in the environment, once
introduced.
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.
Phase
A state of matter. This can be solid, liquid or gaseous.
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.
Physical weathering
Breaking down of rock into bits and pieces by exposure to temperature
and changes and the physical action of moving ice and water, growing roots,
and human activities such as farming and construction.
Phytoplankton
Free-floating, mostly microscopic aquatic plants.
Pilot tests
The testing of a cleanup technology under actual site conditions in
a laboratory in order to identify potential problems before implementation.
POE-treatment
Point-Of-Entry treatment. Total water treatment at the inlet to an entire
building or facility.
Pore
An opening in a membrane or medium that allows water to pass through.
Point source
A stationary location from which pollutants are discharged. It is a
single identifiable source of pollution, such as a pipeline or a factory.
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.
POP's
Persistent Organic Pollutants, complex compounds that are very persistent
and difficultly biologically degradable.
Potable water
Water that is safe for drinking and cooking.
Potentiation
The ability of one chemical to increase the effect of another chemical.
Potentiometric surface
The surface to which water in an aquifer can rise by hydrostatic pressure.
POU-treatment
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.
Pressure sewers
A system of pipes in which water, wastewater, or other liquid is pumped
to a higher elevation.
Pre-treatment
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
Water that serves in any level of the manufacturing process of certain
products.
Product water
Water that has passed through a water treatment plant and is ready to
be delivered to consumers.
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.
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.
Quicksilver water
A solution of mercury nitrate used in gilding.
Having the property of releasing radiation.
Raw sewage
Untreated wastewater and its contents.
Raw water
Intake water before any treatment or use.
Reaeration
Renewing air supplies in the lower layers of a reservoir in order to
raise oxygen levels.
Recarbonization
Process in which carbon
dioxide is bubbled into treatment water in order to lower the pH.
Receiving waters
A river, lake, ocean, stream or other watercourse into which wastewater
or treated effluent is discharged.
Recharge Area
An area where rainwater soaks through the ground to reach an aquifer.
Recirculation
Recycling water after it is used. Often it has to pass a wastewater
purification system before it can be reused.
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.
Reserve Capacity
Extra treatment capacity built into wastewater treatment plants and
sewers to be able to catch up with future flow increases due to population
growth.
Reservoir
A natural or artificial holding area used to store water.
Residue
The dry solids remaining after the evaporation of a sample of water
or sludge.
Resolution
The breaking of an emulsion into its individual components.
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.
More info on reversed osmosis
Run-Off
The part of precipitation water that runs off the land into streams
or other surfacewater.
Water that does not contain harmful bacteria, toxic materials, or chemicals,
and is considered safe for drinking.
Safe yield
The annual amount of water that can be taken from a source of supply
over a period of years without depleting that source beyond its ability
to be naturally refilled.
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. Sand filters
can be supplied in different sizes and materials both hand operated and
fully automatically.
More info on sand filtration
Saturated zone
The area below the water table where all open spaces are filled with
water.
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.
Screening
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
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.
Semi-confined aquifer
An aquifer partially confined by soil layers of low permeability through
which recharge and discharge can still occur.
Semipermeable
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.
Separation
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.
Settling
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.
Sewage
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.
Sewerage
The entire system of sewage collection, treatment, and disposal.
Sludge
A semi-solid residue, containing microoroganisms and their products,
from any water treatment process.
Softening
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.
Solidification
Removal of wastewater from a waste or changing it chemically to make
it less permeable and susceptible to transport by water.
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.
Sparger
A device that introduces compressed air into a liquid.
Sparging
Injection of air below the water table to strip dissolved volatile organic
compounds and to facilitate aerobic biodegradation of organic compounds.
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.
Stoke's Law
A method to calculate the rate of fall of particles through a fluid,
based on density, viscosity and particle size.
Sublimation
The transitions of water directly from the solid state to the gaseous
state, without passing through the liquid state.
Surface tension
The elastic-like force in a body, especially a liquid, tending to minimize,
or constrict, the area of the 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.
Synergism
The combined action of several chemicals, which produces a total effect
greater than the effects of the chemicals separately.
Advanced cleaning of wastewater that goes beyond the secondary or biological
stage, removing nutrients such as phosphorus,
nitrogen, and most BOD and
suspended solids.
Thermal pollution
Discharge of heated water from industrial processes in receiving surface
water, causing death or injury of aquatic organisms.
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.
Total solids
All the solids in wastewater or sewage water, including suspended solids
and filterable solids.
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.
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.
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.
Tube settler
Device using bundles of tubes to let solids in water settle to the bottom
for removal by sludge.
Turbidity
A measure of non-transparency of water due to the presence of suspended
matter.
Turbulent flow
A flow that contains may rapid fluctuations.
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.
Unsaturated Zone
The area above the water table where soil pores are not fully saturated
with water.
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.
More info on UP-water
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.
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.
The spent or used water from a home, community, farm, or industry that
contains dissolved or suspended matter.
Wastewater infrastructure
The plan or network for the collection, treatment, and disposal of sewage
in a community.
Water monitoring
The process of constant control of a body of water by means of sampling
and analyses.
The presence in water of enough harmful or objectionable material to
damage water quality.
The condition of water with respect to the amount of impurities in it.
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.
Weir
A spill over device used to measure or control water flows.
Well
A deep hole with the purpose to reach underground water supplies.
Wetland
An area that is saturated by surface water or groundwater, with vegetation
adapted for life under those soil conditions.
Wettability
The relative degree to which a fluid will spread into solid surface in
the presence of other immiscible fluids.
Any biological substance, displaced from its normal habitat; a chemical
foreign to a biological system.
The rate of production of cake from a dewatering device.
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.
An electrokinetic measurement which can be used for the control of coagulation
processes.
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.
Zooplankton
Tiny aquatic animals eaten by fish.
Zwitter ions
Act as cations or as anions according to the environment in which they
find themselves. In water technology they are usually organic macromolecules.
For more definitions related to aquatic
pollution check this definition list
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