saline water- Water containing an excessive amount of dissolved salts, usually over 5,000 mg/l.

salt- In chemistry, the term is applied to a class of chemical compounds which can be formed by the neutralization of an acid with a with a base; the common name for the specific chemical compound sodium chloride used in the regeneration of ion exchange water softeners.

salt splitting - The process in which neutral salts in water are converted to their corresponding acids or bases by ion exchange resins containing strongly acidic or strongly basic functional groups.

saponification - The process in which a fatty acid is neutralized with an alkali or base to form a soap.

scale - A deposit of mineral solids on the interior surfaces of water lines and containers, often formed when water containing the carbonates or bicarbonates of calcium and magnesium is heated.

sedimentation- The process in which solid suspended particles settle out of water, usually when the water has little or no movement. Also called "settling".

semipermeable membrane - Typically a thin, organic film which allows the passage of some ions or materials while preventing the passage of others. Some membranes will only allow the passage of cations. (See electrodialysis.) Some membranes reject most dissolved substances, but allow the passage of water. (See reverse osmosis.)

septic - A condition existing during the digestion of organic matter, such as in sewage, by anaerobic bacteria in the absence of air. A common process for the treatment of household sewage in septic tanks, and in municipal sewage treatment in specially designed digester.

sequestration - A chemical reaction in which certain ions are bound into a stable, water soluble compound, thus preventing undesirable action by the ions. (See chelate.)

sequestering agent- A chemical compound sometimes fed into water to tie up undesirable ions, keep them in solution, and eliminate or reduce the normal effects of the ions. For example, polyphosphate can sequester hardness and prevent reactions with soap. (See cheating agent.)

service run - That portion of the operating cycle of a water conditioning unit in which treated water is being delivered, as opposed to the period when the unit is being backwashed, recharged or regenerated.

service unit - A term sometimes applied to softeners or filters which are regenerated or backwashed at a central point, then transported to the point of use for connection to the water system. (See portable exchange.)

shielded - The separation of metallic parts by an electrical nonconductor; insulated by other than an air gap.

silica gel or siliceous gel - A synthetic hydrated sodium aluminosilicate with ion exchange properties, once widely used in ion exchange water softeners. (See zeolite, gel zeolite.)

sludge - The semi-fluid solid matter collected at the bottom of a system tank or watercourse, as a result of the sedimentation or settling of suspended solids or precipitates.

slug - An abnormally high concentration of an undesirable substance which passes through a water system, usually brief or intermittent in nature, and often related to an upset of a system. For example, a slug of iron may occur during high flow which disturbs and suspends previously deposited iron precipitates.

soap - One of a class of chemical compounds which possesses cleansing properties; formed by the reaction of a fatty acid with a base or alkali. Sodium and potassium soaps are soluble and useful, but can be converted to insoluble calcium and magnesium soaps (curd) by the presence of these hardness ions in water.

soda ash - the common name for sodium carbonate, Na₂CO₃, a chemical compound used as an alkalinity builder in some soap and detergent formulations to neutralize acid water, and in the lime-soda water treatment process.

sodium - An ion found in natural water supplies, and introduced to water in the ion exchange water softening process. Sodium compounds are highly soluble, and do not react with soaps or detergents.

sodium chloride - The chemical name for common salt, widely used in the regeneration of ion exchange water softeners.

sodium cycle - the cation exchange process in which sodium on the ion exchange resin is exchanged for hardness and other ions in water. Sodium chloride is the common regenerant used in this process.

soft water- Any water which contains less than 1.0 gpg (17.1 mg/l) of hardness minerals, expressed as calcium carbonate.

softened water- Any water that is treated to reduce hardness minerals to 1.0 gpg (17.1 mg/l) or less, expressed as calcium carbonate.

solute - The substance which is dissolved in and by a solvent. Dissolved solids, such as the minerals found in water, are solutes.

solution feeder - A device, such as a power driven pump or an eductor system, designed to feed a solution of a water treatment chemical into the water system, usually in proportion to flow. (See chemical feeder.)

solvent - The liquid, such as water, in which other materials (solutes) are dissolved. (See solute.)

specific conductance - The measure of the electrical conductance of water or a water solution at a specific temperature, usually 25^oC. (See resistance.)

specific gravity- The ratio of the weight of a specific volume of a substance compared to the weight of the same volume of pure water at 4^oC.

specific resistance - The measure of the electrical resistance of water or a water solution at a specific temperature, usually 25^oC. (See resistance.)

sphericity - A measure of the roundness and wholeness of an ion exchange resin bead.

spore - In general, specialized reproductive bodies or resting cells. In water bacterial "spores" resist adverse conditions which would readily destroy the parent organism.
stability index - See Langelier's Index.

Standard Methods - The abbreviation for the name of the reference book "Standard Methods for the Examination of Water and Wastewater", widely used in water and waste water testing and analysis.

static - Fixed in position, resting, or without motion, as opposed to dynamic or moving.

static system - A system or process in which the reactants are not flowing or moving. (See dynamic system.)

sterilization - A process in which all living organisms are destroyed. (See disinfection.)

strong base load factor z - Is the total exchangeable anions. Thus it is the sum of total anions (which equals the Y factor) plus silica, plus carbon dioxide (not carbonic acid formed). 35 gpg is considered upper limit for DI applications.

sulfate - In the range of 30 gpg, sulfate salts can cause laxative effects and medicinal taste. In high concentration with high calcium hardness, a white insoluble compound is formed that is difficult to remove.

sulfate-reducing bacteria - A group of bacteria which are capable of reducing sulfates in water to hydrogen sulfide gas, thus producing obnoxious tastes and odors. These bacteria have no sanitary significance, and are classed as nuisance organisms.

sulfonic acid- A specific acidic group (SO₃H) which gives certain cation exchange resins their ion exchange capability.

sulfur - A yellowish solid element. The term is also commonly used to refer to water containing hydrogen sulfide gas.

superchlorination - The addition of excess amounts of chlorine to a water supply to speed chemical reactions or insure disinfection with short contact time. The chlorine residual following superchlorination is high enough to be unpalatable, and thus dechlorination is commonly employed before the water is used.

supernatant - The clear liquid lying above a sediment or precipitate.

surface-active agent- The material in a soap or detergent formulation which promotes the penetration of the fabric by water, the loosening of the soil from surfaces, and the suspension of many soils; the actual cleaning agent in soap and detergent formulations.

surface tension - The result of attraction between molecules of a liquid which causes the surface of the liquid to act as a thin elastic film under tension. Surface tension causes water to form spherical drops, and to reduce penetration into fabrics. Soaps, detergents and wetting agents reduce surface tension and increase penetration by water.

surfactant - A contraction of the term "surface-active agent".

suspended solids - Solid particles in water which are not in solution.

swelling - In the water treatment context, the expansion of certain ion exchange resins when converted into specific ionic states.

syndet - A contraction of the term "synthetic detergent".

synthetic detergent - A synthetic cleaning agent, such as linear alkyl sulfonate and alkyl benzene sulfonate. Synthetic detergents react with water hardness, but the products are soluble.