Glossary of common sewage industry terms:
biochemical oxygen demand(BOD)
The quantity of dissolved oxygen in water (mg/l) consumed under
test conditions during a given period (5 days) through the microbiological
oxidation of biodegradable organic matter present in wastewaters.
One of the standard tests used to characterise effluent quality.
biological filtration
A process in which settled sewage uniformly trickles downward
through a bed of inert material such as slag, moulded plastics
or clinker, thus permitting contact with the biological film
with which the surfaces of the medium are coated so that oxidation
and clarification take place.
discharge consent/registered standards
An authorisation issued by an environmental regulator to allow
discharge of treated water. Consents are set to minimise pollution
of receiving waters. Consents specify the discharge location,
total volume of treated water permitted and the quality conditions
of the discharged water, such as the biochemical oxygen demand,
limits for suspended solids, ammonia, metals and toxic substances.
descriptive consent
A consent under which discharges are controlled by imposing
general rather than numerical standards.
coliform bacteria
A group of bacteria found in the intestine and faeces of most
animals. Coliforms can sometimes be found in untreated water.
The treatment process removes them and disinfection prevents
their reappearance in the distribution system. In water receiving
discharges, faecal coliform bacteria are used to indicate the
presence of sewage.
disinfection
The destruction of pathogens by physical or chemical means.
eutrophication
The enrichment of water by nutrients, especially compounds of
nitrogen and/or phosphorus, causing an accelerated growth of
algae and higher forms of plant life to produce disturbance
to the balance of organisms present in the water and to the
quality of the water concerned.
final effluent
Typically, the effluent discharged from a treatment plant after
completion of treatment of a domestic or industrial wastewater.
E. coli (Escherichia coli)
A bacterium taken as an indicator of faecal contamination.
groundwater
Water occurring in permeable underground strata, eg chalk and
sandstone.
industrial wastewater
Any wastewater which is discharged from trade or industrial
premises, other than domestic wastewater and run-off rainwater.
numeric consent
A consent in which numerical limits are set for the concentration
or load of substances discharged and also for the effluent flow.
outfall
The site of discharge of a liquid from a pipe. Applied particularly
to the point at which a sewer discharges to a treatment works
or receiving water, or the point at which a conduit discharges
the effluent from a treatment works into a receiving water.
pathogen
A organism which is capable of producing disease.
polluting load
The quantity of polluting matter entering a treatment plant
or in the effluent discharged into a receiving water during
a given period.
population equivalent
The unit of measure used to describe the size of a waste water
discharge. Population equivalent is the biodegradable load (matter)
in waste water having a 5-day biochemical oxygen demand (BOD)
of 60g of oxygen per day. Population equivalent doesn't necessarily
reflect the actual population of a community
private sewer
A sewer which is not a public sewer as defined in Section 20
of the Public Health Act 1936.
public sewer
A sewer vested in a water authority by virtue of the provisions
of Section 20 of the Public Health Act 1936, as amended by Section
40 and Paragraph 33 of the 8th schedule to the Water Act 1973.
screenings
The gross solids, including rags and plastics, in sewage are
intercepted by screens and removed manually or by raking mechanisms.
septic tank
A type of sedimentation tank in which the sludge is retained
sufficiently long for the organic content to undergo anaerobic
digestion. When sludge is eventually removed to a sewage treatment
works, some is left in the tank to act as a 'seed' to initiate
further digestion. Used for receiving the sewage from houses
and other premises which are too isolated for connection to
a foul sewer.
sewage
The water-borne wastes of a community
sewage sludge (also known as 'biosolids' or 'sludge')
A by-product arising from the treatment of sewage or from septic
tanks or similar installations.
sewage (treatment) works (STW)
A term for the structures, plant and equipment used for collecting
and treating sewage, normally with some sludge drying.
sewer
A pipe conveying wastewater or sewage discharged into it from
two or more house drains.
sewerage
A system of pipes and mechanical appliances for the collection
and transportation of domestic and industrial wastewaters.
storm sewage tank
A tank into which, in wet weather, is diverted all the sewage
and rainwater reaching a treatment works in excess of that which
is to receive biological treatment. Its purpose is to store
as much of the storm sewage as possible, for return to the works
inlet after the flow has returned to normal, and to remove settleable
solids from the remainder which overflows from the tank to a
receiving water.
streptococci
Bacterial indicator of faecal contamination of water.
surface water
The run-off from paved and unpaved roads, buildings and land.
suspended solids
In sewage analysis, those solids retained after filtration.
total dissolved solids (TDS)
The concentration of dissolved solids in a wastewater or effluent,
ie the residue after evaporation and drying, expressed in milligrams
per litre of sample.
trade effluent
Wastewater produced by trade and industry; not domestic sewage.
ultraviolet (UV) treatment
Treatment of drinking water or effluent with UV rays to neutralise
bacteria.
