Wastewater Glossary
  • A

  • Absorbent

    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

  • Adsorbent

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

  • Aeration

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

  • Aerator

    a mechanical device that transfers oxygen from air into solution

  • Aerobic

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

  • Aerosol

    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 5

  • Anaerobic

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

  • Anaerobic digester

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

  • Anoxic

    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

  • Autothermal

    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

  • B

  • 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)

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

  • Biocide

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

  • Biodegradable

    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

  • Biofilter

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

  • Biogas

    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

  • Biomass

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

  • Bioremediation

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

  • Biotower

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

  • Bund

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

  • C

  • 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