C
Cadium
a toxic heavy metal to which the most stringent descharge standards apply; a prescribed red list compound with an environmental quality standard (EQS) of 5 - g/l
Catalyst
a substance in 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 seperates solid material, sludges or oil from liquid effluents by rapid rotation
Chemical oxygen demand (COD)
the amount of oxygen (in mg) required for the complete chemical oxidation 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 in 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 hear produced during the generation of electricity; can be coupled to the incineration of solid waste
Condenser
Removed high concentrations of solvent vapours from gas steams by cooling, allowig both the liquid solvent fraction and the gas to be recycled or otherwise treated
Contact stabilsation
An activated sludge process that produces less surplus sludge; seperated 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 in 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
D
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 biodegration, produced when organic material is incinerated at low temperatures
Dissolved air flotation (DAF)
A method of dissolving pressurised air into a liquid 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
E
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 oxideses 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 or sterilising water by introduction of precise amounts of copper and silver; suitable for cooling towers (Legionella control), potable water, swimming pool and effluents
Electostatic precipitator
Equipment in which particles in gas streams are passed through ionisers and become charged, facilitating their subsequent removal
Eutrophication
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?
