Water Treatment Terms……….The Letter S

SAFE WATER: see potable water.

SALINE: Consisting of, or containing salt.

SALT WATER: The general term for all water over 1,000 ppm (mg/L) total dissolved solids.

SAND FILTER: The oldest and most basic filtration process, which generally uses two grades of sand (coarse and fine) for turbidity removal or as a first stage roughing filter or pre-filter in more complex processing systems.

SANITARY WASTEWATER (DOMESTIC): Wastewater, including toilet, sink, shower and kitchen flows, originating from human domestic activities.

SCALE: A coating or precipitate deposited on surfaces such as kettles, water pipes or steam boilers that are in contact with hard water. Waters that contain carbonates or bicarbonates of calcium or magnesium are especially likely to cause scale when heated.

SCAVANGER: (water treatment) A polymer matrix or ion exchanger that is used specifically to remove organic species from the feed water before the water is to pass through the deionization.

SCREEN SIZE: SEE mesh size.

SDI: Silt density index.

SECONDARY WASTEWATER TREATMENT: Biological removal or organics and solids from wastewater. Secondary wastewater effluent limits are generally 30mg/1 BOD5 and 30 mg/1 of TSS.

SELECTIVITY: The tendency of an ion exchanger to “prefer” (have more attraction for) certain kinds of ions over others, as if the resin were ranking the types of ions in order to be removed; most preferred ion, second most preferred, etc.

SEPTIC: Producing or characterized by bacterial decomposition.

SERIAL FILTRATION: The arrangement of two or more filtering steps, one following the other, in order to remove increasingly finer particles at each stage and provide for filtration of all sizes of suspended solids.

SERVICE FLOW: The rate in U.S. gallons per minute (gpm) or litres per minute (L/min) at which a given water processing system can deliver product water. The rating may be intermittent peak flow or constant flow.

SHALLOW WELL: A well sunk in easily penetrated ground to a point which is below the water table but usually less than about 30 feet in depth.

SILT DENSITY INDEX (SDI):  The silt density index (SDI) is a measure of the ability of water to foul a membrane or plug a filter.  SDI is measured using an apparatus which typically consists of an inlet pressure regulator and pressure gauge followed by a filter holder containing a 0.45 µm microporous membrane filter.  Commercial test kits, complete with instructions on how to calculate the index, are available.  Click Here for More Information on Silt Density Index Products!.

SINGLE STAGE SYSTEM: A filtering system that uses only a single filtering cartridge.

SLUDGE JUDGE: a clear tubular device used to measure sludge depth in clarifiers or other tanks.

SLUG: A temporary abnormally high concentration of an undesirable substance which shows up in the product water.

SLURRY: A thin watery mixture of a very fine insoluble substance.

SODA WATER: water which has impregnated with carbon dioxide (CO2)so that it will be effervescent when not under pressure. Same as seltzer water.

SODIUM: (Na+): A metallic element found abundantly in compounds in nature, but never existing alone.

SODIUM CHLORIDE (NaCl): The chemical name for common table salt.

SOFT WATER: Any water which normally contains less than 1.0 grain per gallon (17.1 mg/L or ppm) of total hardness expressed as calcium carbonate equivalent.

SOFTENED WATER: Any water which has been processed in some manner to reduce the total hardness to 17.1 mg/L or ppm (1.0 grain per gallon) or less expressed as calcium carbonate equivalent.

SOLIDS: The matter dissolved or suspended in water or wastewater.

SPIRAL WOUND: A very common construction configuration for one style of reverse osmosis membrane and cartridge filter element. In RO membranes, the membrane sheets are assembled in layers around a perforated mandrel product water tube with coarse mesh spacers screens between the layers, to form a complete module element. In cartridge filter elements, the filtration material such as fiber cord, is continually would around a perforated mandrel core tube.

SPORE: A small reproductive body, often single celled, capable of reproducing the organism under favorable conditions. The spore is sometimes considered the resting stage of the organism. Among the organisms that may produce spores are algae, bacteria and certain protozoan. In water, most spores resist adverse conditions which would readily destroy the parent organism.

SPRING: A place where ground water flows naturally from the soil or rock formation onto the land surface or into a body of surface water. A spring is sometimes used as a source of water for a shallow dug well.

STATIC: Fixed in a position, resting, without motion.

STERILIZATION:  See disinfection.

STORAGE CAPACITY: The maximum volume of water available for use from the water storage tank, e.g. the amount available from a RO or distiller water storage tank.

STORM WATER RUN-OFF (SRO): The pulse of surface water following a rainstorm. The water carries sediment, gas, oil, animal faeces, glass and other waste from the watershed to receiving waters creating a difficult urban/suburban wastewater problem.

STRING WOUND ELEMENT: A cartridge style element constructed by continuous spiral winding of natural or synthetic yarn around a pre-formed product water tube core and then building it up in layers to form a depth type filter.

SUBMICRON FILTER: A cartridge type membrane filter used in fine particle separation applications to remove particles of less than one micron in size.

SUBSURFACE FLOW WETLAND (SF): A type of constructed wetland in which primarily treated waste flows through deep gravel or other porous substrate planted with wetland vegetation. The water is not exposed to the air, avoiding problems with odour and direct contact.

SULPHUR (S): A yellowish solid chemical element. “Sulfur” is also often used to refer to sulfur water.

SULPHUR WATER: water containing objectionable amounts of hydrogen sulfide gas which causes an offensive “rotten egg” odor.

SURFACE FILTRATION: Filtration that occurs at the surface layer (as opposed to within the body depth) of the filter and is accomplished by passing the material to be filtered over a grating screen, sieve or membrane fabric with micro sized holes. The size of the holes in the filter determines what materials will pass through and what will filter out (held back).

SURFACE WATER: All of the water (fresh and salt) on the surface of the earth including streams, lakes oceans, rivers, glaciers and some shallow wells that can be fed by surface runoff water.

SURFACTANT: compounds that lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.

SYSTEM: A complete integrated series consisting of various components and perhaps multiple water treatment processes which can be tested, installed and operated as a single unit of equipment. For example, a single RO treatment system generally consists of two or more stages of media filtration plus cross flow membrane filtration and water storage.