Page 168 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

WATER TREATMENT AND PURIFICATION

4.4 CHAPTER FOUR

SUSPENDED MATTER (PARTICULATES)

Turbidity

Turbidity is a general term used to describe the optical opacity of water containing any form of
insoluble matter, or suspended solids, suspended in water. Color is often used to describe turbid-
ity and may be used when referring to water containing decaying vegetation. However, turbidity
is used most often when referring to mineral particulates, such as silt, that are usually the most
plentiful substances in the water. Other commonly occurring impurities are liquids, such as oil,
and the residue caused by decaying vegetation. Coarse particles that settle rapidly when water is
standing are referred to as sediment; fine particles that remain in suspension are called silt.

Microorganisms
Microorganisms are bacteria and viruses. They are living forms of particulate matter. Their
unusual physiology allows them to grow and multiply in water containing only trace levels
of nutrients. The presence of these nutrients in untreated water is an indicator of the pres-
ence of microorganisms (if the temperature is favorable for their growth). Although micro-
organisms are suspended solids, the treatment required for their removal or neutralization
puts them in a separate category.
Pyrogens cause fever, and pathogenic organisms (such as Legionella) cause diseases of
any kind. Endotoxins, which are fragments derived from the cell walls of Gram-negative
bacteria, are considered the most important and widely occurring group of pyrogens. Other
organic growths include algae (a primitive form of plant life), fungi (plants that lack the
chlorophyll required for photosynthesis), and bacteria that exhibit both plant and animal
characteristics. Bacteria are further subdivided into slime bacteria, which secrete slime;
iron bacteria, which thrive on iron; sulfate-reducing bacteria, which live by consuming sul-
fate and converting it to hydrogen sulfide gas; and nitrifying bacteria, which use ammonia
and whose byproduct results in the formation of nitric acid.
Several methods of measurement are used, including viable count assays, direct count
epifluorescent microscopy, scanning electron microscopy, and biochemical techniques.
The most common means of measuring bacterial contamination is the viable count method,
in which the water being measured is passed through a sterile nutrient medium, and the
number of colonies appearing on the medium is counted after a period of time is allowed
for growth. These are called colony forming units or CFUs. Endotoxins are measured in
endotoxin units per milliliter (EU/mL). A popular form of measurement for endotoxins is
the limulus amoebocyte lysate (LAL) test, in which a blood extract of the horseshoe crab
becomes turbid in the presence of bacterial endotoxins. This detection technique uses opti-
cal density (turbidity level) measured over a period of time.
Other Organisms

This form of impurity is also applied to larger living things such as clams, mussels, and their
larvae. They tend to clog water inlets of salt- and freshwater and may also find their way into the
piping system of a facility. See the section on nonpotable water systems for further discussion.

DISSOLVED MINERALS AND
ORGANIC SUBSTANCES

Organic Substances
Dissolved organic substances typically found in water include both manmade and natural
substances. Manmade impurities include herbicides, pesticides, trihalomethanes, surfactants,

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