An easy to use A to Z of some of the most commonly used terms used throughout the water industry.
| A | B | C | D | E | F | G | H | I | J | K | L | M |
| N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
screenings
The gross solids, including rags and plastics, in sewage are intercepted by screens and removed manually or by raking mechanisms.
security of supply
The extent to which water supplies to customers are reliable and not subject to possible restrictions because of a lack of rainfall over a period of time.
security of supply index (SoSI)
This assesses a water company’s ability to supply customers in drier years without imposing demand restrictions such as hosepipe bans. Companies with higher SoSI scores are better able to meet demand in dry periods.
sedimentation
The process by which settleable solids are removed from sewage by passing it through a tank at a rate that allows the solids to gravitate to the floor to form sludge.
sensitive areas
A water body or area where more than secondary treatment is required for wastewaters discharged under EC directive 91/271/EEC.
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.
service reservoir
A reservoir where treated water is stored.
serviceability
The quality of service provided to customers by an asset irrespective of its physical condition.
sewage (or wastewater)
Water-borne wastes from domestic uses of water, derived from households or similar uses in trade and industry. Storm sewage is that flowing to a treatment works in wet weather or discharged from storm overflows, when the sewage is diluted to a greater or lesser extent with rainwater.
sewage sludge (also known as 'biosolids' or 'sludge')
A by-product arising from the treatment of sewage or from septic tanks or similar installations. (See Article II of EC directive 86/278/EEC for full definition.)
sewage (treatment) works (STW)
A term for the structures, plant and equipment used for 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.
sludge cake
Sludge that has been dewatered to the extent that it can be handled as a solid, usually containing more than 15 per cent dry solids, depending on the type of sludge and method of dewatering.
soft water
Water which forms an immediate lather with soap and has a total hardness which is typically less than 60 milligrams per litre (as CaC03).
source station
A pumping station and/or treatment works which supplies treated drinking water from a specific water supply source.
statutory water company
A company authorised immediately before the passing of the Water Act 1973 by any local statutory provision to supply water, or a company in whom the assets of any company so authorised have subsequently become vested.
statutory water quality objective (SWQO)
Water quality objective set down in legislation.
storage reservoir
A reservoir for storing untreated water.
storm sewage overflow
A device to prevent overloading of the sewerage system during storm events.
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.
supply/demand balance
The extent to which the demand for water and the water resources available are in balance, taking variability of supply and demand into account.
supply pipe
That portion of pipe which conveys water from the main to the customer's house and which is on the customer's property.
surface water
The run-off from paved and unpaved roads, buildings and land.
suspended solids
In sewage analysis, those solids retained after filtration.
sustainable urban drainage systems (SUDS)
SUDS offer an alternative approach to drainage in developed areas, that keeps water on site longer, prevents pollution and allows storage and use of the water.
SUDS include one or more of the following: inlet structures, outlet structures, swales, constructed wetlands, ponds, filter trenches, attenuation tanks and detention basins (together with any associated pipes and equipment).
