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Sand filter
separates suspended solids and associated BOD/COD from liquids by passing the liquid
through a bed of sand
Screens
equipment that separates solid material from liquid by allowing the liquid to
pass through constrictions (the screen) of chosen size
Septic tank
container that receives untreated sewage, holds back floating scum and retains
and digests heavy solids but allows clarified liquor to proceed forward for
further treatment or discharge
Settlement tank
container that allows sufficient retention time for the separation of organic
and inorganic solids from liquid and produces sludge and clarified liquor both
of which may receive further treatment
Sewage
liquid effluent from domestic and industrial activity
Sludge
the wet solids that can be settled from an untreated liquid effluent (primary
sludge); or from aerobically treated effluent (secondary sludge)
Slurry
mixture of urine, faeces and wash water from cattle or pig rearing
Soil washing
water-based volume reduction process in which contaminated soil or dredgings are
separated into a small contaminated fraction, for further treatment or disposal,
and a larger cleaned fraction
Special waste
waste that contains substances considered to be dangerous to life as listed in
the Control of Pollution (Special Waste) Regulations 1980; applies within the UK
Static tubular aerator
a system in which air is blown into vertical tubes submerged in a liquid,
promoting mixing and oxygen transfer
Submerged aerated filter
a device in which highly aerated effluent flows through inert media that is
completely submerged; fixed microbial film reduces the BOD and ammoniacal
content of the effluent
Submerged biological contactor
an aerobic treatment system in which plastic media that is largely submerged in
effluent is rotated by rising air, the fixed microbial film on the media
reducing the BOD value
Submicron particles
particles of less than 1µm in size, present in smoke and fumes
Sulphur dioxide (SO2)Sulphur dioxide (SO2)
toxic gas produced during the combustion of sulphur compounds in fossil fuels;
component of acid rain
Surface aerator
equipment in which blades or vanes rotate about a vertical or horizontal shaft
and entrain air to mix and aerate wastewater
Suspended solids
solids of organic and inorganic origin present in liquid effluents;
concentration in (mg/l) measured by filtration followed by drying at 105 -C
Thermal oxidation
high temperature incineration of pollutants such as VOCs and odours in gas
streams
Trickling filter
a bed of gravel or pebble media through which clarified effluent percolates and
microbial activity removes BOD, suspended solids and ammoniacal nitrogen
Turbidity
a measure of the cloudiness of a liquid that is caused by the presence of fine
suspended solids
Ultrafiltration
the separation from a liquid of particles of 0·005-0·1 µm in size by pumping
the liquid through a synthetic membrane at high pressure
Ultrapure water
water from which most other materials have been removed, producing a resistivity
of at least 18 M-cm, and making it sufficiently pure for the most exacting
microelectronic, pharmaceutical and medical uses
Ultraviolet light system
a disinfection system in which light of 254 nm, produced by mercury lamps,
damages microorganisms by disrupting their genetic material
UV ozone
a powerful wastewater treatment process employing ozone in solution and
ultraviolet light; oxidises COD and toxic substances, removes colour and
disinfects
Vapour extraction
a technique that makes use of a partial vacuum to remove volatile and
semi-volatile contamination, such as hydrocarbons, from soils
Venturi aerator
a submerged jet aeration device in which the liquid to be aerated is pumped
through a nozzle within a larger diameter tube, causing air entrainment and
vigorous liquid mixing
Venturi scrubber
a device that removes submicron particles and reactive trace gases from gas
streams by passing the gas at high velocity through the scrubbing liquor
ensuring vigorous mixing
Volatile organic compounds (VOCs)
substances such as solvents that are liquid at room temperature, but vaporise
significantly and take part in the generation of ozone pollution in the lower
atmosphere
Waste minimisation
the analysis and revision of the use of materials, processes, equipment and
procedures in order to reduce the unnecessary use of energy and resources, to
reduce the generation of effluents and wastes and to recycle where practical
Waste incineration
incineration of waste at high temperatures in two stages to promote efficient
combustion to an ash and carbon dioxide
Wet air oxidation
a process that treats waste water containing high strength or hazardous organic
chemicals by a combination of high temperature and pressure that creates highly
reactive hydroxyl radicals
