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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 m 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 1-10m 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.

2006 Oasis Environmental Ltd