Water Quality Flashcards
what can most water borne pathogens classified as
viruses, bacteria, protozoa
what do pathogens cause
intestinal diseases - leaving the host in fecal material, contaminating the water supply, entering the recipient by ingestion
pathogens survival period in water varies widely. What factors influence it
salinity, temperature
rank bacteria survival length, shortest to longest -> cellular viruses, bacteria, protozoa
bacteria, cellular viruses, protozoa
how does protozoa extend their survival time
encystation -> formation of cysts of hard crust around amoeba in response to unfavourable conditions
what three enteric viruses are of practical concern as water-borne viruses
infections hepatitis A, poliovirus, viral gastoenteritis
how long does enteric viruses survive generally
less than three months in the environment, but have been reported surviving up to five months in sewage
what is the largest group of water-borne pathogens
bacteria
whats the minimum infectious dose to cause bacteriological infection
several hundred to several thousand organisms
what prolongs bacterias survival
low temperatures, sediment adsorption, and anoxic conditions
what is the cause of dysentery, strictly a human affliction
shigella sp
what is the cause of gastointestinal diseases while one variety, which is strictly a human pathogen, causes typhoid
salmonellosis sp
what is a highly contagious disease causing dramatic and fatal loss of water and electrolytes. Healthy carriers may make up 1-9% or even up to 25% of the population
Cholera
how does protozoans enter the host body
by ingestion usually in cyst form
what are the protozoans of major concern as water borne pathogens
giardia, cryptosporidium, entamoeba
what is the concept of an indicator organism
indicate possible presence of disease-causing constituents
what should an indicator organism behave like
- be applicable to all water
- be present when pathogens are
- have no aftergrowth in water
- be absent when pathogens are
- have constant characteristics
- persist longer than pathogens
- be harmless to humans
- correlate quantitatively with pathogens
- be present in greater numbers than pathogens
- be easily, accurately and quickly detected
what coliform group nearly fulfills the criteria of an indicator organism
Escherichia coli (E. coli)
what are the positives of protozoans and viruses as a reliable indicator of bacterial pathogens
they usually survive longer than E. coli and may also survive disinfection which is otherwise adequate for bacteria.
what is successful in extracting protozoans and viruses
filtration
what is total coliforms an indicator of
drinking water only
where are fecal coliforms present
textile and pump and paper mill wastes
what is E. coli used for
EPA recommended best indicator for recreational waters
what are the typical water quality standards for drinking water
no coliforms contamination acceptable
