Ch. 24 - Hygiene and Water Disinfection Flashcards
What cause Water Borne Illnesses?
Microorganisms in the water such as: bacteria, protozoa, viruses, and parasitic worms. All cause diarrhea.
What are some diseases that commonly spread through contaminated water?
typhoid, cholera, campylobacteriosis, giardiasis, and hepatitis A.
What is Giardia?
It is a microscopic protozoan. Two-stage lifecycle as cyst and trophozoite. The cyst is excreted through animal feces and can survive 2-3 months in near-freezing water. If swallowed, the cyst will turn into the trophozoite and attach to the lining of the small intestine.
True or False. Most Giardia infections are asymptomatic?
True. Most infections are without symptoms and people unwittingly spread the illness.
For Giardia, how long is the incubation period from ingestion to the onset of symptoms?
1-3 weeks.
What are the symptoms of Giardia?
Recurrent, persistent, malodorous stools and flatus, abdominal cramping, bloating, sulfur burps, and indigestion. Serious infections produce explosive, watery diarrhea, with cramps, foul flatus, fever, and malaise.
What is Cryptosporidium ?
Another microscopic protozoan. It is spread by contaminated water, raw/undercooked food, or from fecal matter.
What are symptoms of Cryptosporidium infection?
Some people may be asymptomatic. Illness onset occurs 2-10 days after infection. Watery diarrhea, headache, abdominal cramps, nausea, vomiting and low grade fever.
Can become life-threatening to those with compromised immune systems.
What is the difference between purifying water, sterilizing water and disinfecting water?
Purifying = eliminates odors, colors, tastes, debris. Sterilizing = Kills all life-forms Disinfecting = Removes or destroys disease causing micro-organisms.
People often say they are purifying water, when really they are disinfecting it.
What are the four main methods of water disinfection?
Heat; Chemical Treatment; Filtration; UV Light.
How do you properly use heat to disinfect water?
The boiling point for water decreases with an increase in altitude. From 212 F at sea level to 178 F at 19,000ft. However, Giardia/Entamoeba die after 2-3 minutes at 140 F.
Cryptosporidium dies within minutes at 150 F.
By the time water boils, it is safe to drink, regardless of altitude.
How do you properly use a chemical treatment to disinfect water?
Introduce Halogens to the water. These are either IODINE, CHLORINE, or CHLORINE DIOXIDE.
DO NOT work on cryptosporidium!
The concentration of the chemical and the contact time with the water determine the degree of disinfection. If water is very cold, it will slow the reaction of halogens or chlorine dioxide.
Allow for 30 minutes in warm water (86 F).
Allow 60 minutes in cold water (59 F).
True or False. We must filter the water before using a chemical treatment to disinfect?
True. When the chemicals bind with organic and inorganic particles floating in the water, it reduces the effectiveness. Reduce debris before chemical treatment. Improvise a strainer, or wait for the debris to sink to the bottom of the container and take off the top.
What are cases in which Iodine should NOT be used to disinfect water?
Anyone with thyroid disease, know iodine allergy, or might be pregnant.
How do you improve the aftertaste of Iodine and Chlorine after using to disinfect?
You can add flavoring after disinfecting. Don’t add packet of sport drink to it before disinfection because halogens will bind to the sugars in the drink. It is fine to add the flavoring post disinfection.
A vitamin C tablet (ascorbic acid) can reduce iodine to iodide and chlorine to chloride which makes it taste better.
