Environmental Engineering Reference
In-Depth Information
liter (mg/L). For drinking water analyses, concentration in parts per
million and milligrams per liter can be considered to be equivalent.
A single PPM can be compared to a shot glass full of water inside a
swimming pool.
Pathogens —Types of microorganisms that can cause disease.
Physical treatment —Any process that does not produce a new substance
(e.g., screening, adsorption, aeration, sedimentation, filtration).
Polar covalent bond —Occurs when the shared pair of electrons between
two atoms are not shared equally; thus, one of the atoms becomes
slightly positively charged and the other atom becomes slightly neg-
atively charged.
Polar covalent molecule —One or more polar covalent bonds result in a
molecule that is polar covalent. Polar covalent molecules exhibit par-
tial positive and negative poles, causing them to behave like tiny
magnets; water is the most common polar covalent substance.
Pollutant— Any substance introduced into the environment that
adversely affects the usefulness of the resource.
Pollution— The presence of matter or energy whose nature, location,
or quantity produces undesired environmental effects. Under the
Clean Water Act, for example, the term is defined as a manmade or
human-induced alteration of the physical, biological, and radiologi-
cal integrity of water.
Pretreatment— Any physical, chemical, or mechanical process used
before the main water treatment processes. It can include screening,
presedimentation, and chemical addition.
Primary drinking water standards —Regulations on drinking water qual-
ity defined under the SDWA that are considered essential for the
preservation of public health.
Primary treatment —The first step of treatment at a municipal wastewa-
ter treatment plant. It typically involves screening and sedimenta-
tion to remove materials that float or settle.
Public water system (PWS) —As defined by the SDWA, any system, pub-
licly or privately owned, that serves at least 15 service connections
60 days out of the year or serves an average of 25 people at least 60
days out of the year.
Publicly owned treatment works (POTW) —A waste treatment works
owned by a state or local government unit or Indian tribe, usually
designed to treat domestic wastewaters.
Receiving waters —A river, lake, ocean, stream, or other water source
into which wastewater or treated effluent is discharged.
Recharge —The process by which water is added to a zone of saturation,
usually by percolation from the soil surface.
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