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The Water Quality Association (WQA)
Microbial and organic contaminants can't always be detected
through sight, smell or taste. You might go years before realizing a problem
exists.
Although some waterborne microbes can cause illness, many microbes
are harmless or even beneficial.
Very small levels of microbes are naturally present in many water
supplies, but some are more dangerous than others.
Some of the more dangerous microbial contaminants, such as E.
coli, Giardia, and Cryptosporidium, can cause
gastrointestinal problems and flu-like symptoms commonly attributed to
undercooked or improperly stored food. They include:
Bacteria: Single-celled organisms lacking well-defined nuclear
membranes and other specialized functional cell parts which reproduce by cell
division or spores.
Bacteria (along with fungi) are decomposers that break down the
wastes and bodies of dead organisms, making their components available for
reuse.
Bacterial cells range from about 1 to 10 microns in length and
from 0.2 to 1 micron in width. They exist almost everywhere on earth.
Some bacteria are helpful to humans, while others are harmful.
Viruses: Parasitic infectious microbes,
composed almost entirely of protein and nucleic acids, which can cause
disease(s) in humans.
Viruses can reproduce only within living cells. They are 0.004 to
0.1 microns in size, which is about 100 times smaller than bacteria.
Cysts: Capsules or protective sacs produced by many protozoans (as
well as some bacteria and algae) as preparation for entering a resting or a
specialized reproductive stage.
Similar to spores, cysts tend to be more resistant to destruction
by disinfection.
Fortunately, protozoan cysts are typically 2 to 50 microns in
diameter and can be removed from water by fine filtration.
There are both chemical and physical ways to disinfect water.
Chemical disinfection often uses halogens such as chlorine,
iodine, bromine, or ozone, while common physical choices are ultraviolet (UV)
light, ultrafiltration, and distillation.
These processes can eliminate 99.9 - 99.9999% of harmful
microorganisms.
Water treatment can address pathogenic microbiologicals through
the following techniques:
Chlorination
The treatment process in which chlorine gas or a chlorine solution
is added to water for disinfection and control of microorganisms.
Chlorination is also used in the oxidation of dissolved iron,
manganese, and hydrogen sulfide impurities.
This method of disinfection involves adding chlorine to water to
make it safer to drink.
It’s common, cost-effective, and quick, killing many pathogenic
microorganisms.
It can even oxidize or break down iron, manganese, and hydrogen
sulfide, which can result in water that is clearer and tastes better.
Some people find that chlorine gives water its own objectionable
chemical taste and odor.
It also can produce disinfection byproducts (which may cause
health issues) by reacting with other substances in water when stored.
These byproducts can often be filtered out with activated carbon.
Ultraviolet (UV) Light
The UV disinfection method, which does not involve chemicals, has
long been popular for commercial use, but is becoming more common in homes.
UV systems expose water to light at just the right wavelength for
killing microbes. It’s a way to kill bacteria, viruses, fungi, protozoans, and
cysts that may be present in the water.
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The effectiveness of UV treatment depends on the strength and intensity of the light, the amount of time the light shines through the water, and the quantity of particles present in the water.
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The effectiveness of UV treatment depends on the strength and intensity of the light, the amount of time the light shines through the water, and the quantity of particles present in the water.
The light source must be kept clean and the UV lamp replaced
periodically.
UV light treatment can’t remove gases, heavy metals, and
particulates; for that reason, higher-end systems may include additional
filtration such as activated carbon.
Ozone
Ozone is produced when oxygen is exposed to high-voltage
current.
The use of ozone in water treatment can destroy viruses,
bacteria, and other microorganisms, while also removing iron, sulfur and
manganese.
Ozone does its job quickly and then rapidly decomposes, cutting
down on the introduction of harmful disinfection byproducts and foul tastes or
odors associated with chlorination.
This process tends to be more costly and energy-consuming and is
typically used commercially or by large municipalities.
The
Water Quality Association (WQA) is a not-for-profit association for the residential
commercial, and industrial water treatment industry. WQA represents more
than 2,500 member companies around the globe. Our membership is comprised
of equipment manufacturers, suppliers, dealers and distributors of
water quality improvement products and services.
WQA
proudly serves as an educator of water treatment professionals, certifier of
water treatment products, public information resource and voice of the water
quality improvement industry.
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