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Glossary A and B

a substance, a solid or a liquid, that allows another substance, a liquid or a gas, to permeate it

Activated carbon
a solid adsorbent material that is used to remove organic pollutants from liquid or gas streams

Activated sludge
(1) the flocculent mass of microorganisms, mainly bacteria, that develops when sewage or liquid effluent is aerated; (2) a continuous process in which a liquid effluent is aerated in a tank to reduce the BOD and ammoniacal nitrogen

a substance, usually porous, that allows the molecules of a gas or liquid to adhere to its large surface area

the introduction of air into a liquid so that gaseous oxygen dissolves into the liquid

a mechanical device that transfers oxygen from air into solution

(1) microorganisms that require oxygen for their respiratory processes; (2) an environment in which oxygen is available

very small liquid or solid particles dispersed in a gas or air, for example a mist or fume; may be formed by blowing liquid through a nozzle

Air flotation
the separation of solids and oils from liquid effluents by their attachment to very small air bubbles which float the material to the surface

Ammoniacal nitrogen
nitrogen combined with hydrogen in the form of ammonia (NH3) or the ammonium ion (NH4+); present in sewage, toxic to fish and restricted in discharges to about 50-100 mg/l

Anaerobic digester
a tank or vessel which excludes oxygen and in which a sludge or liquid is modified by the action of anaerobic bacteria

(1) microorganisms that do not require oxygen for their respiratory processes; (2) an environment in which oxygen is not available

describes a condition in which a liquid has become devoid of oxygen and in which certain microorganisms can obtain oxygen from nitrate or nitrite ions

Attrition scrubbing
a process that grinds soil particles together in the presence of a liquid to remove surface contamination

used to describe the combustion or digestion of a material of sufficient calorific value or with effective heat recovery so that little or no additional fuel is needed after the initiation stage



Bag filter
textile or sintered polymer filters used to remove dust and fume particles from gas streams. Used also on liquid waste to provide a final polish or remove floc particles

Balancing tank
provides sufficient storage volume to permit a non-uniform flow of waste water to be collected, mixed and pumped forward to a treatment system at a uniform rate

Belt press
a device in which waste sludge is compressed between two moving belts, thickening and dewatering it

Biochemical oxygen demand (BOD) MORE INFO
the amount of oxygen (in mg) required by aerobic bacteria to decompose the biodegradable organic material in 1 litre of an effluent

a chemical that is used to kill selected living organisms; for example pesticides, herbicides, fungicides

describes a substance that can be decomposed by microorganisms

Biofilm, biological film or microbial film
a thin slimy layer of microorganisms that develops on the surface of the media in trickling filters, biotowers and contactors and oxidises organic material from effluent

removes odours from gaseous emissions by passing the gas through layers of peat, heather or similar substrate on which microorganisms grow

a mixture of methane (CH4) and carbon dioxide (CO2), produced by the anaerobic digestion of sludges or organic material in landfill sites; can be used to generate heat or power

Biological filter
a packaged treatment system that removes BOD and suspended solids from relatively small flows of sewage or industrial wastewater by passing the effluent over plastic media on which aerobic biofilm develops

the amount of organic material of biological origin in a given area or volume

a treatment that enhances the ability of naturally occurring or cultured microorganisms to degrade organic pollutants in soil

an above ground structure containing plastic media covered in microbial film that reduces the BOD/COD/Ammonia of industrial liquid effluent flowing over it

an outer wall or tank designed to retain the contents of an inner tank in the event of leakage or spillage

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