Sampling The process of obtaining a representative portion of the material of
concern.
Sand and gravel dredging It is an extremely common industry worldwide. Sand
and gravel dredged from rivers or landlocked mines provide aggregate materials
for building, construction, and infrastructure projects.
Sandfloat It is combined circular dissolved air flotation and filtration (DAFF)
clarifier designed by the Lenox Institute of Water Technology (LIWT) and
manufactured by Krofta Engineering Corporation (KEC).
Sanitary landfill Burying sludge or solid wastes to minimize nuisance conditions
or public health problem is called sanitary landfill. Sludge and solid wastes are
buried in layers, which are covered with fill material excavated at the site.
Landfills must be located where nearby wells and groundwater supplies will not
be contaminated by leachate from the landfill operation. Sludge landfills are
generally separate from refuse landfills.
Sanitation The development and application of measures for the sake of cleanliness
and protecting health, especially the disposal of excreta and solid waste.
Scale, map It is the ratio or relationship between a distance or area on a map and the
corresponding distance or area on the ground.
Scenarios A plausible and often simplified description of how the future may
develop based on a coherent and internally consistent set of assumptions about
driving forces and key relationships.
Screen A device used to retain or remove suspended or floating objects in wastewater. The screen has openings that are generally uniform in size. It retains or
removes objects larger than the openings. A screen may consist of bars, rods,
wires, gratings, wire mesh, or perforated plates.
Sea surface temperature The temperature in the top several feet of the ocean,
measured by ships, buoys, and drifters.
Secondary effluent The effluent from a secondary treatment step, which may be
either (a) biological treatment, such as activated sludge aeration or equivalent
plus secondary clarification, or (b) physicochemical treatment, such as chemical
precipitation/coagulation plus secondary clarification. Secondary treatment step
removes most of dissolved organic/inorganic pollutants from primary effluent.
Since secondary clarification (either secondary sedimentation clarification or
secondary flotation clarification) is the final step of secondary treatment, the
secondary effluent is also the secondary clarification effluent.
Secondary flotation clarification It is a unit process or unit operation for removal
of the bio-oxidation process generated activated sludge, and/or the chemical
precipitation/coagulation process generated chemical sludge using a secondary
flotation clarifier.
Secondary flotation clarifier A dissolved air flotation (DAF) reactor is used to
float biological sludge (activated sludge) from biologically oxidized wastewater
(such as aeration tank effluent) and/or chemical sludge from chemically coagulated /flocculated wastewater (such as flocculator effluent) by decreasing the
sludge’s apparent density. DAF consists of saturating a portion or all of the
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479
concern.
Sand and gravel dredging It is an extremely common industry worldwide. Sand
and gravel dredged from rivers or landlocked mines provide aggregate materials
for building, construction, and infrastructure projects.
Sandfloat It is combined circular dissolved air flotation and filtration (DAFF)
clarifier designed by the Lenox Institute of Water Technology (LIWT) and
manufactured by Krofta Engineering Corporation (KEC).
Sanitary landfill Burying sludge or solid wastes to minimize nuisance conditions
or public health problem is called sanitary landfill. Sludge and solid wastes are
buried in layers, which are covered with fill material excavated at the site.
Landfills must be located where nearby wells and groundwater supplies will not
be contaminated by leachate from the landfill operation. Sludge landfills are
generally separate from refuse landfills.
Sanitation The development and application of measures for the sake of cleanliness
and protecting health, especially the disposal of excreta and solid waste.
Scale, map It is the ratio or relationship between a distance or area on a map and the
corresponding distance or area on the ground.
Scenarios A plausible and often simplified description of how the future may
develop based on a coherent and internally consistent set of assumptions about
driving forces and key relationships.
Screen A device used to retain or remove suspended or floating objects in wastewater. The screen has openings that are generally uniform in size. It retains or
removes objects larger than the openings. A screen may consist of bars, rods,
wires, gratings, wire mesh, or perforated plates.
Sea surface temperature The temperature in the top several feet of the ocean,
measured by ships, buoys, and drifters.
Secondary effluent The effluent from a secondary treatment step, which may be
either (a) biological treatment, such as activated sludge aeration or equivalent
plus secondary clarification, or (b) physicochemical treatment, such as chemical
precipitation/coagulation plus secondary clarification. Secondary treatment step
removes most of dissolved organic/inorganic pollutants from primary effluent.
Since secondary clarification (either secondary sedimentation clarification or
secondary flotation clarification) is the final step of secondary treatment, the
secondary effluent is also the secondary clarification effluent.
Secondary flotation clarification It is a unit process or unit operation for removal
of the bio-oxidation process generated activated sludge, and/or the chemical
precipitation/coagulation process generated chemical sludge using a secondary
flotation clarifier.
Secondary flotation clarifier A dissolved air flotation (DAF) reactor is used to
float biological sludge (activated sludge) from biologically oxidized wastewater
(such as aeration tank effluent) and/or chemical sludge from chemically coagulated /flocculated wastewater (such as flocculator effluent) by decreasing the
sludge’s apparent density. DAF consists of saturating a portion or all of the
12 Glossary of Natural Resources and Environmental Pollution Control
479