434there is no consensus, some studies have even suggested that lime softening is effective at
removal of Giardia. Hard water is a common condition responsible for numerous problems.
Users often recognize hard water because it prevents their soap from lathering properly.
However, it can also cause buildup (“scale”) in hot water heaters, boilers, and hot water pipes.
Because of these inconveniences, many treatment facilities use lime softening to soften hard
water for consumer use. Before lime softening can be used, managers must determine the
softening chemistry required. This is a relatively easy task for groundwater sources, which remain
more constant in their composition. Surface waters, however, fluctuate widely in quality and may
require frequent changes to the softening chemical mix. In lime softening, lime and sometimes
sodium carbonate are added to the water as it enters a combination solids contact clarifier. This
raises the pH (i.e., increases alkalinity) and leads to the precipitation of calcium carbonate. Later,
the pH of the effluent from the clarifier is reduced again, and the water is then filtered through a
granular media filter. The water chemistry requirements of these systems require knowledgeable
operators, which may make lime softening an economic challenge for some very small systems.
LIME: Is a chemical that may be added to water to reduce the corrosivity. When an operator
adds lime to water, Calcium and magnesium become less soluble.
LIQUID: A state of matter which takes the shape of its container.
LONDON DISERSION FORCES: A weak intermolecular force.
LSI = pH - pHs
M
M.S.D.S.: Material Safety Data Sheet, now S.D.S. (Safety Data Sheet). A safety document must
an employer provide to an operator upon request.
MAGNESIUM HARDNESS: Measure of the magnesium salts dissolved in water – it is not a
factor in water balance.
MARBLE AND LANGELIER TESTS: Are used to measure or determine the corrosiveness of a
water source.
MAXIMUM CONTAMINANT LEVEL (MCLs): The maximum allowable level of a contaminant that
federal or state regulations allow in a public water system. If the MCL is exceeded, the water
system must treat the water so that it meets the MCL.
MAXIMUM CONTAMINANT LEVEL GOAL (MCLG): The level of a contaminant at which there
would be no risk to human health. This goal is not always economically or technologically
feasible, and the goal is not legally enforceable.
MCL for TURBIDITY: Turbidity is undesirable because it causes health hazards. An MCL for
turbidity was established by the EPA because turbidity does not allow for proper disinfection.
MEASURE CORROSION DAMAGE: A coupon such as a strip of metal and is placed to measure
corrosion damage in the distribution system in a water main.
MEDIUM WATER SYSTEM: More than 3,300 persons and 50,000 or fewer persons.
MELTING: The phase change from a solid to a liquid.
M-ENDO BROTH: The coliform group is used as indicators of fecal pollution in water, for
assessing the effectiveness of water treatment and disinfection, and for monitoring water quality.
m-Endo Broth is used for selectively isolating coliform bacteria from water and other specimens
using the membrane filtration technique. m-Endo Broth is prepared according to the formula of
Fifield and Schaufus.1 It is recommended by the American Public Health Association in standard
total coliform membrane filtration procedure for testing water, wastewater, and foods.2,3 The US
EPA specifies using m-Endo Broth in the total coliform methods for testing water using single-
step, two-step, and delayed incubation membrane filtration methods.: The media shall be brought
to the boiling point when preparing M-Endo broth to be used in the membrane filter test for total
coliform.
METAL: Chemical element that is a good conductor of both electricity and heat and forms cations
and ionic bonds with non-metals.
METALIMNION: Thermocline, middle layer of a thermally stratified lake which is characterized by
a rapid decrease in temperature in proportion to depth.
METALLOID: Metalloid is a term used in chemistry when classifying the chemical elements. On
the basis of their general physical and chemical properties, nearly every element in the periodic