440disease. Protozoa must be removed from drinking water by filtration, because they cannot be
effectively killed by chlorine.
PUBLIC NOTIFICATION: An advisory that EPA requires a water system to distribute to affected
consumers when the system has violated MCLs or other regulations. The notice advises
consumers what precautions, if any, they should take to protect their health.
PUBLIC WATER SYSTEM (PWS): Any water system which provides water to at least 25 people
for at least 60 days annually. There are more than 170,000 PWSs providing water from wells,
rivers and other sources to about 250 million Americans. The others drink water from private
wells. There are differing standards for PWSs of different sizes and types.
PWS: 3 types of public water systems. Community water system, non-transient non-community
water system, transient non-community water system.
Q
QUANTA: It is the minimum amount of bundle of energy.
QUANTUM MECHANICS: The study of how atoms, molecules, subatomic particles, etc. behave
and are structured.
QUARKS: Elementary particle and a fundamental constituent of matter.
R
RADIATION: Energy in the form of waves or subatomic particles when there is a change from
high energy to low energy states.
RADIOACTIVE DECAY: The process of an unstable atomic nucleus losing energy by emitting
radiation.
RADIOCHEMICALS: (Or radioactive chemicals) Occur in natural waters. Naturally radioactive
ores are particularly common in the Southwestern United States, and some streams and wells
can have dangerously high levels of radioactivity. Total alpha and beta radioactivity and isotopes
of radium and strontium are the major tests performed for radiochemicals. The federal drinking
water standard for gross alpha radioactivity is set at 5 picocuries per liter.
RAW TURBIDITY: The turbidity of the water coming to the treatment plant from the raw water
source.
RAW WATER: Water that has not been treated in any way; it is generally considered to be unsafe
to drink.
REAGENT: A substance used in a chemical reaction to measure, detect, examine, or produce
other substances.
RECHARGE: The infiltration component of the hydrologic cycle. Often used in the context of
referring to: The infiltration of water back into an aquifer, resulting in the restoration of lost storage
and water levels which had been decreased due to pumping and/or natural discharges from the
aquifer.
RECORDER, FLOW: A flow recorder that measures flow is most likely to be located anywhere
in the plant where a flow must be measured and in a central location.
RED WATER AND SLIME: Iron bacteria are undesirable in a water distribution system because
of red water and slime complaints.
REDOX POTENTIAL: Reduction potential (also known as redox potential, oxidation / reduction
potential or ORP) is the tendency of a chemical species to acquire electrons and thereby be
reduced. Each species has its own intrinsic reduction potential; the more positive the potential,
the greater the species' affinity for electrons and tendency to be reduced. In aqueous solutions,
the reduction potential is the tendency of the solution to either gain or lose electrons when it is
subject to change by introduction of a new species. A solution with a higher (more positive)
reduction potential than the new species will have a tendency to gain electrons from the new
species (i.e. to be reduced by oxidizing the new species) and a solution with a lower (more
negative) reduction potential will have a tendency to lose electrons to the new species (i.e. to be
oxidized by reducing the new species).
RELAY LOGIC: The name of a popular method of automatically controlling a pump, valve,
chemical feeder, and other devices.
RESERVOIR: An impoundment used to store water.