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Cadmium
a toxic heavy metal to which the most stringent discharge standards apply; a
prescribed red list compound with an environmental quality standard (EQS) of 5
-g/l
Catalyst
a substance which increases the rate of a chemical reaction without being
consumed in the reaction
Catalytic incinerator
a device in which the use of catalysts allows the combustion of solvent vapours
and other VOCs to be carried out at relatively low temperatures
Centrifuge
a device that separates solid material, sludges or oil from liquid effluents by
rapid rotation
Chemical oxygen demand (COD)
MORE INFO
the amount of oxygen (in mg) required for the complete chemical oxidation of
organic and inorganic material in 1 litre of an effluent
Chlorinated hydrocarbons
organic compounds containing the elements carbon, hydrogen and chlorine,
implicated in low level ozone production and high level ozone destruction
Chromium
a toxic heavy metal that may contaminate groundwater; stringent environmental
discharge limits apply
Coagulation
a process that alters the surface charge on dispersed colloidal particles in a
liquid so that they are able to agglomerate; the first stage in floc formation
Combined heat and power (CHP)
system designed to use the heat produced during the generation of electricity;
can be coupled to the incineration of solid waste
Condenser
removes high concentrations of solvent vapours from gas streams by cooling,
allowing both the liquid solvent fraction and the gas to be recycled or
otherwise treated
Contact stabilisation
an activated sludge process that produces less surplus sludge; separated sludge
is aerated vigorously before it contacts and stabilises raw sewage
Cryptosporidium
a protozoan parasite causing diarrhoea in humans and other animals; the pathogen
is spread in water as spherical oocysts 5 µm diameter, resistant to chlorine
treatment
Cyanides
toxic inorganic chemical compounds containing cyanide (-CN) groups and classed
as special waste
Cyclone
a device in which a gas stream is spun and coarse grit and dust particles are
thrown outwards to the cyclone wall where they are guided into a hopper
Desorption
the removal of adsorbed gas or liquid molecules from the surface of a solid
Desulphurisation
the removal of sulphur compounds from flue gas in the form of solid sulphur or
as calcium sulphate (gypsum)
Digestion
the enzymatic breakdown of large insoluble organic molecules into small soluble
organic molecules which can be absorbed and used by either aerobic and anaerobic
microorganisms
Dioxins
a group of toxic organic substances, containing carbon, hydrogen, oxygen and
chlorine, resistant to biodegradation, produced when organic material is
incinerated at low temperatures.
Dissolved air flotation (DAF)
a method of dissolving pressurised air into a liquid to form small bubbles that
will float material to the surface
Drag-out bath
container of water in which metal plated objects are rinsed to remove excess
plating solution
Drainfield
consists
of long underground perforated pipes or tiles connected to a septic tank. The
network of pipes is laid in gravel-filled trenches (2-3 feet wide), or beds
(over 3 feet wide) in the soil. Liquid waste or effluent flows out of the tank
and is evenly distributed into the soil through the piping system. The soil
below the drainfield provides the final treatment and disposal of a septic tank
effluent. After the effluent has passed into the soil, most of it percolates
downward and outward, eventually entering the groundwater. A small percentage is
taken up by plants through their roots, or evaporates from the soil.
Dust
solid particles about 1-10µm in size
Effluent
(1) a flow containing polluting material; (2) liquid waste from sewage
treatment, industry, agriculture
Electrochemical cell
a device that removes metals from aqueous solutions by plating them as solid
metal on the cathode or oxidises organic pollutants at the anode
Electrokinetic decontamination
a method of removing metals and other inorganic pollutants from contaminated
soils using electrodes
Electrolysis
a chemical change brought about by the passage of an electric current through a
liquid; used in plating of metals, oxidation of cyanide
Electronic
Water Disinfection
a method of sterilising water by introduction of precise amounts of copper and
silver; suitable for cooling towers (Legionella control), potable water,
swimming pool and effluents
Electrostatic precipitator
equipment in which particles in gas streams are passed through ionisers and
become charged, facilitating their subsequent removal
Eutrophication (More
Info)
Eutrophication is a process taking place in natural waters. The process is
characterized by development of an environment rich in nutrients and consequent
proliferous plant production. Man-made eutrophication of inland water courses
and shallow coastal waters is caused by excessive discharge of nutrients,
especially phosphorus (P) and nitrogen (N) in the form of PO4 and
NO3.
