Water quality and public health Flashcards
Water
The most important potential common source of infectious diseases
-ensuring water purity for public health
What schemes use microorganisms to identify, remove, degrade
Treatment and purfication
Water can be sampled for the presence of
specific indicator mircoorganisms
Coliform group includes
Enterobacter, e.coli, klebsiella pneumonia
what is used for indicator for contamination in water?
ooliform microbes
What reduces incidence of water borne diseases and when did it take placfe
water treatment
twntieth century
what methods were used and adapted in 1905?
What was treatment limited to?
in 1910, what was used as a disinfectant in water
coliform-counting methods
treatment limited to filtration
chlorine
Name steps of purification
sedimentation- remove particles
coagulation and flocculation- form aggregates to settle out
filtration- remove parasites, charcoal to remove taste, odor, chemicals
disinfection- residual
understand drinking treatment plan
Coagulants such as anionic polymers and alum are added
Many of microbes and cysts removed during this process
Filtration removes rest of protozoan cysts
Chemical/UV disinfection kills viruses and unfiltered bacteria
? historically most common drinking water disinfectant
chlornation
Chlorine gas or sodium hypochlorite (bleach)▪Kills bacterial and viral pathogens
▪Ineffective against Cryptosporidium, not very effective against Giardia
▪Oxidizes taste and smell compounds
▪Must leave residual, after it has reacted with organic matter (0.6 ppm)▪
Can produce disinfection by products
? used in some places, does not leave residual
UV
It is effective against Cryptosporidium and Giardiacysts (text is wrong)
▪Being promoted for lack of disinfection by-products and chemical addition
▪Requires highly clear water for maximum effectiveness
▪Suspended solids quickly reduce effectiveness
▪Pretty
Ozone
also used in some places, does not leave residual
▪Works as an oxidizer, gasgenerated on site
Wastewater treatment is a
multistep operation employing both physical and biological processes
Major goal of wastewater treatment is to
reduce nutrients or biochemical oxygen demand
Primary, secondary, and sometimes tertiary treatments are used explain primary
Uses physical separation methods to separate solid and particulate organic and inorganic materials from wastewater
▪Still many pathogens and high nutrient load
Primary methods remove much of suspended solids
Secondary Methods
degrade or remove “food” (organics) and more suspended solids
Goal is to break down solid and dissolved organic matter, reduce organic nutrient load –Biological processes
▪(Reduce BOD, N and P nutrients)
▪Most treatment plants chlorinate the effluent after secondary treatment to further reduce the possibility of pathogen contamination
Tertiary Treatment or AKA
Advanced Wastewater Treatment
Tertiary Treatment
Any physiochemical or biological process employing bioreactors, precipitation, filtration, or chlorination procedures similar to those used for purification of drinking water▪Reduces the levels of inorganic nutrients further (e.g., phosphate, nitrate, nitrite)▪Most complete method of treating sewage but it has not been widely adopted due to costs
Sterilization
The killing or removal of all viable organisms within a growth medium
Inhibition
Effectively limiting microbial growth
Decontamination
The treatment of an object to make it safe to handle
Disinfection
Directly targets the removal of all pathogens, not necessarily all microbes or endospores
Heat sterilization
is the most widely used method of controlling microbial growth
High temperatures
denature macromolecules
decimal reduction time
Amount of time required to reduce viability tenfold is called the
Can survive heat that would rapidly kill vegetative cells
ednospores
▪Pasteurization
s the process of using precisely controlled heat to reducethe microbial load in heat-sensitive liquids: heat, then rapidly cool▪Doesn’t kill all organisms so it is different than sterilization
autoclave is a sealed heating device that uses
steam under pressure
▪Allows temperature of water to get above 100°C
▪Not the pressure in an autoclave that kills things, but the high temperature
? can all reduce microbial growth
Microwaves, UV, X-rays, gamma rays, and electrons
UV
has sufficient energy to cause modifications and breaks in DNA▪UV is useful in decontamination of surfaces▪Cannot penetrate solid, opaque, or light-absorbing surfaces
Ionizing Radiation
Electromagnetic radiation of sufficient energy to produce ions and other reactive molecular species▪Generates electrons, hydroxyl radicals, and hydride radicals
Some microbes are
more resistant to radiation than others
Microbes tend to be more
tend to be moreorganisms
Sources of radiation include
cathode ray tubes, X-rays, and radioactive nuclides
Radiation
is used for sterilization in the medical field and food industry
Radiation is approved by the WHO and is
Used in the USA for decontamination of foods particularly susceptible to microbial contamination
Susceptibility to food spoilage is based in large part on
moisture content
Perishable foods have higher
moisture content than nonperishable foods
Fresh foods are spoiled by both
bacteria and fungi
Spoilage organisms are those that can gain access to the food and use available nutrients▪May or may not be pathogenic (usually not)▪Carried on raw foods (vegetables, etc) or introduced by consumer, or during processing, etc.
Cold food
Slows microbial growth rate and delays spoilage
▪Psychrotolerant bacteria and fungi can grow at refrigerator temperatures
▪Freezing allows for longer storage, but isn’t suitable for all foods
Pickling and acidic foods
pH is an important factor in microbial growth▪Most foods are neutral or acidic
▪At pH less than 5 most spoilage organisms are inhibited
▪During pickling process acetic acid is added to a solution with sugar or salt
▪Pickled foods include pickles, fish, peppers and fruits
Drying and Dehydration
Moisture content (water activity) is critical for microbial metabolic processes ▪Sugar and salt reduce the availability of water for microbial growth (in effect, dehydrating it)
▪I.e., jams, jellies, meats, fish
▪Lyophilization(freeze-drying) is the physical removal of frozen water under vacuum▪Very expensive, but very effective
Heating/ canning
Used to reduce the bacterial load (i.e., pasteurization) of a product or to actually sterilize it (i.e., canning)▪Canning isn’t always 100% effective▪Results in swollen cans (DO NOT EAT!)
What significantly extends shelf life of finished?
Chemical Preservation
▪Various added chemicals may be used to control microbial growth▪I.e., sodium propionate, sodium benzoate, nitrites, etc.
▪Some, such as nitrites, are controversial because studies show they may be harmful to human health (cancer?)
Many commons foods are
preserved, produced, or enhanced by the actions of microbes
Fermentation is the anaerobic catabolism of organic compounds (generally carbohydrates), without
external electron acceptor
Important bacteria in the fermented food industry are
lactic acid bacteria, propionic acid bacteria, and acetic acid bacteria
Fermentation becomes ? when pH drops
self-limiting
Filtration avoids
he use of heat for sterilization of sensitive liquids and gasses
pore filtrs
Pores of filter are too small for organisms to pass through
▪Pores are large enough to allow liquid or gas to pass through
HEPA filters
are depth filters
Membrane Filters
Function more like a sieve
▪(i.e., Nucleopore filters)
Antimicrobial agents can be classified as
bacteriostatic, bacteriocidal, and bacteriolytic
Minimum inhibitory concentration (MIC)
is the smallest amount of an agent needed to inhibit growth of a microbe
Disk diffusion assay
Zone of inhibition: diameter depends on conc., solubility, diffusion into cell, and effectiveness of agent
These antimicrobial agents can be divided into two categories
Products used to control microorganisms in commercial and industrial applications, largely to prevent fouling or spoilage▪E.g., air-conditioning cooling towers, textile and paper products, fuel tanks
▪Products designed to prevent growth of human pathogens in inanimate environments and on external body surfaces▪Sterilants, disinfectants, sanitizers,and antiseptics
Sterilant:
destroys all forms of microbial life (sterilizes)▪Gases →ethylene oxide, formaldehyde, H2O2; liquid like sodium hypochlorite
Disinfectant
kill microorganisms, maybe not spores
▪Ethanol, detergents; used for decontamination of surfaces
Sanitizer:
Reduce microbial numbers; detergents, Lysol, ethanol
Antiseptic:
non-toxic enough to use on tissue; ethanol, triclosan, listerine, benzalkonium chloride, hydrogen peroxide dilute solution
▪Handwashing, wounds, oral care, etc. ▪Triclosan issues, phasing out for benzalkonium chloride instead
Paul Ehrlich initially began studying
selective toxicityin the early 1900s
Selective toxicity is
the ability to inhabit or kill a pathogen without harming the host, or with limited side effects
Salvarsan
one of the first effective antimicrobial drugs; a dye containing arsenic, used against syphilis
Growth factor analogs:
structurally similar to growth factors but don’t function in cell
▪Analogs known for many important biomolecules i.e. vitamins, amino acids, etc.
Sulfanilamide
Inhibits folic acid synthesis
Sulfa drugs:
Gerhard Domagk in the 1930s
Nucleic acid base analogs:
used against viral and fungal infections.
Nucleic acid base analogs formed by
Formed by the addition of bromine or fluorine
