saline water--water that contains significant
amounts of dissolved solids.
Here are our parameters for saline water:
Fresh water - Less than 1,000 parts per million (ppm)
Slightly saline water - From 1,000 ppm to 3,000 ppm
Moderatly saline water - From 3,000 ppm to 10,000 ppm
Highly saline water - From 10,000 ppm to 35,000 ppm
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secondary wastewater treatment--treatment
(following primary wastewater treatment) involving the biological
process of reducing suspended, colloidal, and dissolved organic
matter in effluent from primary treatment systems and which
generally removes 80 to 95 percent of the Biochemical Oxygen Demand
(BOD) and suspended matter. Secondary wastewater treatment may be
accomplished by biological or chemical-physical methods. Activated
sludge and trickling filters are two of the most common means of
secondary treatment. It is accomplished by bringing together waste,
bacteria, and oxygen in trickling filters or in the activated sludge
process. This treatment removes floating and settleable solids and
about 90 percent of the oxygen-demanding substances and suspended
solids. Disinfection is the final stage of secondary treatment.
sediment--usually applied to material in
suspension in water or recently deposited from suspension. In the
plural the word is applied to all kinds of deposits from the waters
of streams, lakes, or seas.
sedimentary rock--rock formed of sediment, and
specifically: (1) sandstone and shale, formed of fragments of other
rock transported from their sources and deposited in water; and (2)
rocks formed by or from secretions of organisms, such as most
limestone. Many sedimentary rocks show distinct layering, which is
the result of different types of sediment being deposited in
succession.
sedimentation tanks--wastewater tanks in which
floating wastes are skimmed off and settled solids are removed for
disposal.
self-supplied water--water withdrawn from a
surface- or ground-water source by a user rather than being obtained
from a public supply. An example would be homeowners getting their
water from their own well.
seepage--(1) The slow movement of water through
small cracks, pores, Interstices, etc., of a material into or out of
a body of surface or subsurface water. (2) The loss of water by
infiltration into the soil from a canal, ditches, laterals,
watercourse, reservoir, storage facilities, or other body of water,
or from a field.
septic tanks--a tank used to detain domestic
wastes to allow the settling of solids prior to distribution to a
leach field for soil absorption. Septic tanks are used when a sewer
line is not available to carry them to a treatment plant. A settling
tank in which settled sludge is in immediate contact with sewage
flowing through the tank, and wherein solids are decomposed by
anaerobic bacterial action.
settling pond (water quality)--an open lagoon
into which wastewater contaminated with solid pollutants is placed
and allowed to stand. The solid pollutants suspended in the water
sink to the bottom of the lagoon and the liquid is allowed to
overflow out of the enclosure.
sewage treatment plant--a facility designed to
receive the wastewater from domestic sources and to remove materials
that damage water quality and threaten public health and safety when
discharged into receiving streams or bodies of water. The substances
removed are classified into four basic areas:
[1] greases and fats;
[2] solids from human waste and other sources;
[3] dissolved pollutants from human waste and decomposition
products; and
[4] dangerous microorganisms.
Most facilities employ a combination of mechanical removal steps and
bacterial decomposition to achieve the desired results. Chlorine is
often added to discharges from the plants to reduce the danger of
spreading disease by the release of pathogenic bacteria.
sewer--a system of underground pipes that
collect and deliver wastewater to treatment facilities or streams.
sinkhole--a depression in the Earth's surface caused by
dissolving of underlying limestone, salt, or gypsum. Drainage is
provided through underground channels that may be enlarged by the
collapse of a cavern roof.
solute--a substance that is dissolved in another
substance, thus forming a solution.
solution--a mixture of a solvent and a solute.
In some solutions, such as sugar water, the substances mix so
thoroughly that the solute cannot be seen. But in other solutions,
such as water mixed with dye, the solution is visibly changed.
solvent--a substance that dissolves other
substances, thus forming a solution. Water dissolves more substances
than any other, and is known as the "universal solvent".
specific conductance--a measure of the ability
of water to conduct an electrical current as measured using a 1-cm
cell and expressed in units of electrical conductance, i.e., Siemens
per centimeter at 25 degrees Celsius. Specific conductance can be
used for approximating the total dissolved solids content of water
by testing its capacity to carry an electrical current. In water
quality, specific conductance is used in ground water monitoring as
an indication of the presence of ions of chemical substances that
may have been released by a leaking landfill or other waste storage
or disposal facility. A higher specific conductance in water drawn
from downgradient wells when compared to upgradient wells indicates
possible contamination from the facility.
spray irrigation--an common irrigation method
where water is shot from high-pressure sprayers onto crops. Because
water is shot high into the air onto crops, some water is lost to
evaporation.
storm sewer--a sewer that carries only surface
runoff, street wash, and snow melt from the land. In a separate
sewer system, storm sewers are completely separate from those that
carry domestic and commercial wastewater (sanitary sewers).
stream--a general term for a body of flowing
water; natural water course containing water at least part of the
year. In hydrology, it is generally applied to the water flowing in
a natural channel as distinct from a canal.
streamflow--the water discharge that occurs in a
natural channel. A more general term than runoff, streamflow may be
applied to discharge whether or not it is affected by diversion or
regulation.
subsidence--a dropping of the land surface as a
result of ground water being pumped. Cracks and fissures can appear
in the land. Subsidence is virtually an irreversible process.
surface tension--the attraction of molecules to
each other on a liquid's surface. Thus, a barrier is created between
the air and the liquid.
surface water--water that is on the Earth's
surface, such as in a stream, river, lake, or reservoir.
suspended sediment--very fine soil particles
that remain in suspension in water for a considerable period of time
without contact with the bottom. Such material remains in suspension
due to the upward components of turbulence and currents and/or by
suspension.
suspended-sediment concentration--the ratio of
the mass of dry sediment in a water-sediment mixture to the mass of
the water-sediment mixture. Typically expressed in milligrams of dry
sediment per liter of water-sediment mixture.
suspended-sediment discharge--the quantity of
suspended sediment passing a point in a stream over a specified
period of time. When expressed in tons per day, it is computed by
multiplying water discharge (in cubic feet per second) by the
suspended-sediment concentration (in milligrams per liter) and by
the factor 0.0027.
suspended solids--solids that are not in true
solution and that can be removed by filtration. Such suspended
solids usually contribute directly to turbidity. Defined in waste
management, these are small particles of solid pollutants that
resist separation by conventional methods.
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