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Safe water: Water that does
not contain harmful bacteria, toxic materials, or chemicals, and is considered
safe for drinking.
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Safe yield: The annual amount
of water that can be taken from a source of supply over a period of years without
depleting that source beyond its ability to be naturally refilled.
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Saline water: Water that contains
more than 1,000 milligrams per liter of dissolved solids.
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Salinity: Amount of dissolved
salts in a given volume of water.
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Saltwater
intrusion: The
invasion of fresh surface water or groundwater by saltwater.
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Sand filtration: Sand filtration
is a frequently used and very robust method to remove suspended solids from
water. The filtration medium consists of a multiple layer of sand with a variety
in size and specific gravity. Sand filters can be supplied in different sizes
and materials both hand operated and fully automatically.
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Sanitary
landfill: Landfill
that is lined with plastic or concrete or located in clay-rich soils to prevent
hazardous substances from leaking into the environment.
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Sanitary
sewers: Underground
pipes that carry off only domestic or industrial waste, not storm water.
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Saturated
zone: The area
below the water table where all open spaces are filled with water.
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Saturation: The condition
of a liquid when it has taken into solution the maximum possible quantity of
a given substance at a given temperature and pressure.
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Scale: The precipitate
that forms on surfaces in contact with water as the result of a physical or
chemical change.
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Screening: Use of screens
to remove coarse floating and suspended solids from sewage.
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Seal: The impermeable
material, such as cement grout bentonite, or puddling clay placed in the annular
space between the borehole wall and the casing of a water well to prevent the
downhole movement of surface water or the vertical mixing of artestian waters.
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Seasonal
rate structure:
Rate structure that bills
all water consumed during the summer or peak season at a higher rate than during
the other seasons.
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Secondary
treatment: Second
step in most waste treatment systems, in which bacteria break down the organic
parts of sewage wastes; usually accomplished by bringing the sewage and bacteria
together in trickling filters or in the activated sludge process. Compare primary
treatment, tertiary treatment. Compare primary treatment, tertiary treatment.
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Secondary
wastewater treatment plant:
A facility that reduces
pollutants and suspended solids to a greater level than that achieved by a primary
treatment plant; the water goes through additional treatment processes, producing
"cleaner" wastewater.
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Sediment: Fragmented organic
or inorganic material derived from the weathering of soil, alluvial, and rock
materials; removed by erosion and transported by water, wind, ice, and gravity.
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Sedimentary
cycle: Biogeochemical
cycle in which materials primarily are moved from land to sea and back again.
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Sedimentation: The deposition
of sediment from a state of suspension in water or air.
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Sediments: Soil, sand, and
minerals washed from land into water, usually after rain.
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Seep: A spot where
water contained in the ground oozes slowly to the surface and often forms a
pool; a small spring.
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Seiche: A periodic oscillation,
or standing wave, in an enclosed water body the physical dimensions of which
determine how frequently the water level changes.
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Self-supplied
water: Water
withdrawn from a surface- or ground-water source by a user rather than being
obtained from a public supply.
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Semi-confined
aquifer: An aquifer
partially confined by soil layers of low permeability through which recharge
and discharge can still occur.
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Semipermeable: A medium that
allows water to pass through, but rejects dissolved solids, so that it can be
used to separate solids from water.
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Separate
sewer: A sewer
system that carries only sanitary sewage, not stormwater runoff. When a sewer
is constructed this way, wastewater treatment plants can be sized to treat sanitary
wastes only and all of the water entering the plant receives complete treatment
at all times. Compare combined sewer.
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Separation: The isolation
of the various compounds in a mixture.
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Septic tank: Tank used to
hold domestic wastes when a sewer line is not available to carry them to a treatment
plant; part of a rural on-site sewage treatment system.
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Settleable
solids: In sewage,
suspended solids that will settle when the sewage is brought to a quiet state
for a reasonable length of time, usually two hours.
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Settling: The process of
sinking of a substance sinking in water. This occurs when the substance does
not dissolve in water and its density is larger than that of water.
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Settling
pond: A holding
pond for wastewater where heavier particles sink to the bottom for removal and
disposal.
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Sewage: The waste and
wastewater produced by residential and commercial establishments and discharged
into sewers.
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Sewage contamination: The introduction
of untreated sewage into a water body.
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Sewage sludge: Sludge produced
in a public sewer.
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Sewage system: Pipelines or
conduits, pumping stations, force mains, and all other structures, devices,
and facilities used for collecting or conducting wastes to a point for treatment
or disposal.
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Sewer: A channel or
conduit that carries wastewater and storm water runoff from the source to a
treatment plant or receiving stream.
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Sewerage: The entire system
of sewage collection, treatment, and disposal.
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Silt: Fine particles
of sand or rock that can be picked up by the air or water and deposited as sediment.
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Siltation: The deposition
of finely divided soil and rock particles upon the bottom of stream and river
beds and reservoirs.
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Sleet: Precipitation
which is a mixture of rain and ice.
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Slickensides: A smooth striated
polished surface produced on rock by movement along a fault.
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Sludge: A semi-solid
residue from any of a number of air or water treatment processes.
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Snow: Precipitation
in the form of branched hexagonal crystals, often mixed with simple ice crystals,
which fall more or less continuously from a solid cloud sheet. These crystals
may fall either separately or in cohesive clusters forming snowflakes.
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Soft water: Any water that
does not contain large concentrations of the dissolved minerals calcium or magnesium.
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Softening: The removal of
calcium and magnesium from water to reduce hardness.
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Soil erosion: The processes
by which soil is removed from one place by forces such as wind, water, waves,
glaciers, and construction activity and eventually deposited at some new place.
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Solidification: Removal of wastewater
from a waste or changing it chemically to make it less permeable and susceptible
to transport by water.
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Solubility: The amount of
mass of a compound that will dissolve in a unit volume of water.
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Solute: Any substance
derived from the atmosphere, vegetation, soil, or rock that is dissolved in
water.
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Solvent: Substances (usually
liquid) capable of dissolving or dispersing one or more other substances.
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Source protection: Protection of
a water source by a small utility, ranging from simple sanitary surveys of a
watershed to the development and implementation of complex land use controls,
in an effort to avoid water contamination.
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Sparger: A device that
introduces compressed air into a liquid.
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Sparging: Injection of
air below the water table to strip dissolved volatile organic compounds and
to facilitate aerobic biodegradation of organic compounds.
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Specific
conductance:
A measure of the ability of a water to conduct an electrical current. Specific
conductance is related to the type and concentration of ions in solution and
can be used for approximating the dissolved solids concentration in water. In
general, for the san antonio river basin, conductivity *.6 approximates tds.
People monitoring water quality can measure electrical conductivity quickly
in the field and estimate tds without doing any lab tests at all. See tds.
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Specific
heat: The amount
of heat required to raise the temperature of a kilogram of a substance (water)
by 1 degree Celsius.
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Spillway: The channel or
passageway around or over a dam through which excess water is diverted.
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Spoils: Dirt or rock
that has been removed from its original location, destroying the composition
of the soil in the process, as with strip-mining or dredging.
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Spray irrigation: Application of
finely divided water droplets to crops using artificial means.
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Spring: An area where
groundwater flows naturally onto the land surface.
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Sprinkler
irrigation: A
pressurized irrigation system where water is distributed through pipes to the
field and applied through a variety of sprinkler heads or nozzles. Pressure
is used to spread water droplets above the crop canopy to simulate a rainfall.
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Standard
industrial classification (SIC) codes:
Four- digit codes established
by the Office of Management and Budget and used in the classification of establishments
by type of activity in which they are engaged.
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Standard
solution: Any
solution in which the concentration is known.
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Stoke's
Law: A method
to calculate the rate of fall of particles through a fluid, based on density,
viscosity and particle size.
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Storm sewer: A system of pipes
(separate from sanitary sewers) that carry only water runoff from building and
land surfaces.
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Stormwater
discharge: Precipitation
that does not infiltrate into the ground or evaporate due to impervious land
surfaces but instead flows onto adjacent land or water areas and is routed into
drain/sewer systems.
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Stream: Any body of running
water moving under gravity flow through clearly defined natural channels to
progressively lower levels.
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Stream segment: Refers to the
surface waters of an approved planning area exhibiting common biological, chemical,
hydrological, natural, and physical characteristics and processes. Segments
will normally exhibit common reactions to external stress such as discharge
or pollutants.
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Streamflow: The discharge
that occurs in a natural channel. Although the term "discharge" can be applied
to the flow of a canal, the word "streamflow" uniquely describes the discharge
in a surface stream. The term "streamflow" is more general than the term "runoff",
as streamflow may be applied to discharge whether or not it is affected by diversion
or regulation.
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Sublimation: The transition
of water directly from the solid state to the gaseous state, without passing
through the liquid state; or vice versa. Compare condensation, evaporation.
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Submetering: Use of separate
meters to indicate individual water use in apartments, condominiums, and trailer
homes, while the entire complex of units continues to be metered by the main
supplier.
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Subsidence: Sinking down
of part of the earth's crust due to underground excavation, such as removal
groundwater.
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Supply: A schedule that
shows the various quantities of things offered for sale at various prices at
a point in time. Compare demand.
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Surface
impoundment:
An indented area in the land's surface, such a pit, pond, or lagoon.
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Surface
irrigation: Application
of water by means other than spraying such that contact between the edible portion
of any food crop and the irrigation water is prevented.
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Surface
tension: The
elastic-like force in a body, especially a liquid, tending to minimize, or constrict,
the area of the surface.
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Surface
water: All water
naturally open to the atmosphere (rivers, lakes, reservoirs, streams, impoundments,
seas, estuaries, etc.); also refers to springs, wells, or other collectors that
are directly influenced by surface water.
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Surface-water
disposal: Refers
to the release of reclaimed water or treated effluent directly into a surface
water body (including marshes or wetlands). This does not include water discharged
into ponds for holding or percolation purposes.
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Surge irrigation: The intermittent
application of water to irrigation pathways. This method pulses water down the
furrow and creates more uniform irrigation.
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Suspended
solids (SS):
Defined in waste management, these are small particles of solid pollutants that
resist separation by conventional methods. Suspended solids (along with biological
oxygen demand) are a measurement of water quality and an indicator of treatment
plant efficiency.
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Sustainable
development:
Development that ensures that the use of resources and the environment today
does not restrict their use by future generations.
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Sustainable
management: Method
of exploiting a resource that can be carried on indefinitely. Removal of water
from an aquifer in excess of recharge is, in the long term, not a sustainable
management method.
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Sustained
overdraft: Long
term withdrawal from the aquifer of more water than is being recharged.
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Swamp: A type of wetland
that is dominated by woody vegetation and does not accumulate appreciable peat
deposits. Swamps may be fresh water or saltwater and tidal or nontidal.
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Synergism: The combined
action of several chemicals, which produces a total effect greater than the
effects of the chemicals separately.
