Drinking Water Part 2 Flashcards
What health effects are associated with microbes in drinking water?
gastroenteritis, death in immunocompromised
What contaminants are regulated under the EPA Safe Water Act?
Microbes, radionuclides, inorganics, volatile organics, synthetic organics, disinfectants, disinfection by products
What standard exists for microbes in drinking water?
No standard, instead specifies a treatment technique (e.g., removal of 99.99% of microbe)
What are the three groups of biological pollutants in drinking water?
bacteria, parasites, viruses
List 6 examples of viruses.
rotavirus, human caliciviruses, hepatitis A virus, adenovirus 40 & 41, astrovirus, enteroviruses
List 6 types of bacteria.
Escherichia, Salmonella, Yersinia, Campylocabacter, Vibrio, Clostridium
What are 5 examples of parasites?
Giardia, Cryptosporidium, Microsporidia, Cyclospora, Toxplasma gondii
What is an example of a radionuclide and why are they bad?
Radon; increases cancer risk
What are examples of inorganic chemicals?
Arsenic, cadmium, lead, nitrate/nitrite
What are examples of synthetic organics?
Dioxin, pesticides, Di(2-ethylhexyl) phthalate (DEHP)
What are examples of volatile organics?
Benzene, toluene, trichloroethylene
What are disinfectants?
Water additives used to control microbes
Why do disinfectants have maximum residual levels?
They can be harmful (eye/nose irritation, stomach discomfort, anemia)
What are Disinfection Byproducts (DBPs)?
DBPs are formed when disinfectants used in H2O treatment plants react with bromide and/or natural organic matter present in the source water
What are 3 examples of DBPs?
trihalomethanes, haloacetic acids, bromate
Why are pharmaceuticals/personal care products a concern for drinking water?
They are ending up in the water supply and are not always removed (see video on Potomac River)
What are the four stages of water treatment?
coagulation, floccuation/sedimentation, filtration, disinfection
What is coagulation?
chemicals are added to water to create a coagulant
What is flocculation?
further agglomeration of particles achieved by rapid mixing (particles removed, dissolved contaminants remain)
What is sedimentation?
the water is allowed to undergo a period of quiescence, allowing the floc to settle to the bottom of the settling tank for removal and disposal
What is filtration?
Settled water is further treated by filtration (rapid and filtration is common, also any backwash to clear filters must be discharged into sewage)
What is disinfection?
removal of infectious material to a level such that disease cannot be detected, i.e. elimination of a pathogen that causes waterborne disease
What factors affect disinfection?
disinfectant concentration, contact time, temperature, pH, encapsulation
List the 3 biological contaminants in order of most to least resistant to disinfection.
Parasites, viruses, bacteria
Describe the kinetics of disinfection.
- gradual process that involves a series of physical-chemical and biochemical steps
- effectiveness is (C X t), c= disinfectant concentration, t=time required to inactivate certain % of population under set conditions
- lower Ct value= more effective disinfectant
What are the three types of water disinfectants?
Chlorine, ozone, and UV radiation
What are the pros and cons of chlorine as a disinfectant?
Pros: cheap, good disinfectant, provides residual
Cons: relatively unstable, forms DBPs that are possibly carcinogenic
What are the pros and cons of ozone as a disinfectant?
pros: good disinfectant, limited DBP formation
cons: no residual, expensive
What are the pros and cons of UV radiation?
pros: effective on cryptosporidium, no DBPs, no storage problems
cons: no residual, interference by solids and turbidity
Why is a strong residual good for drinking water?
Provides protection from contamination later in the water distribution system
What causes DBP formation?
DBPs are formed when Cl reacts with naturally occurring dissolved organic material in water
What are the potential adverse health effects of DBPs?
adverse pregnancy outcomes (stillbirths, neonatal deaths), possible increased risk of birth defects, cancer
Why is fluoride added to drinking water?
To reduce tooth decay/cavities
Why is fluoridation controversial?
Young children with excessive fluoride intake can develop mottled tooth enamel, excessive consumption over a lifetime can increase skeletal fractures or cause skeletal fluorosis
Which agency is responsible for regulating bottled water?
FDA
What types of bottled water are available?
Artesian, fluoridated, ground, mineral, purified, sparkling, spring, sterile, well
What is artesian well water?
from well that taps an aquifer; often more pure due to natural filtration
What is mineral water?
water from underground source w/ at least 250 ppm dissolved solids from the source of the water (can’t be added later)
What is spring water?
drawn from underground formation from which water flows naturally to the earth’s surface
What is well water?
water from a hole bored or drilled into the ground, which taps into an aquifer
Can bottled water be drawn from municipal sources (the tap)?
YES. It may undergo distillation, reverse osmosis, absolute 1 micron filtration, or ozoanation
What is the environmental impact of bottled water?
producing the bottle uses 17 million barrels of oil a year, produces 2.5 million tons of CO2, it takes 3L of H2O to make 1L of bottled H2O, only 20% of plastic bottles are recycled
