L24

Question 1

define water microbiology

Answer 1

• study of microbial ecology under specialised aquatic conditions
• related to eutrophication (nutrient enrichment of a body of water), disease, biofilms

Question 2

where does anaerobic + aerobic decomposition occur in lakes

Answer 2

anaerobic- under surface of sediment (profundal zone)

aerobic- surface of organic debris

Question 3

explain eutrophication

Answer 3

• is excessive nutrient enrichment of a body of water
• caused by fertilisers + domestic sewage
• is bad, disrupts aquatic food chain: nitrates + phsophates can over fertilise water, excessive growth of phytoplanton, decline of benthic plants + O2 levels drop, fish die
• C:N:P ratio of algae is 101:16:1
• C:N:P ratio fo domestic sewage is 20:19:1, so 1/40 is phosphorus

Question 4

how to fight eutrophication

Answer 4

• inhibts algal growth with chemical (but will kill other organisms as well)
• artifically restore O2 levels (successful but impractical, eliminates fish kills and reduces phosphates)
• mechanically harvest biomass (successful on small scale)

**maximise sucess
- contorl input of nutrients (ban use of phosphate detergents)
- run off control (recycle farm wast, erosion contorl scheme, plant buffers, treat sewage/waste water)

Question 5

types of water related infections: water borne, contact, washed, aerosol, vector

Answer 5

-water borne (ingested, faecal oral)
-water contact
water-washed (human to human direct contact via water, e.g. if multiple people with chlymadia use same water)
water-aerosol (spray of water, legionella)
water vectors (water is part of a insect lifecycle, e.g. mosquitos)

Question 6

categories of water

Answer 6

domestic effluent
- primary source of pathogens
-untreated sewage, livestock waste, filter feeders

ground water
-some pathogens present

Question 7

water + chain of infection

Answer 7

• useful for contorlling infection
• source + resorvoir of microbes
  -route of spread (direct contact, inhalation, ingestion, vector borne)
  -host (susceptiability, age, health)

Question 8

guidelines for drinking water vs recreational water

Answer 8

drinking water
- should not contain any e.coli in 100ml

recreational water
-primary contact (direct contact with water, e.g. swimming, should contain less then 150 facal coliforms/100ml)

• secondary contact (less frequent body contact, e.g. boating/fishing, contain less then 1000faecal coliforms/100ml
• no contact, no microbial limits

note: no need to test if water less then 24 degrees, doesnt survive

Question 9

explain the disinfection of drinking water: chlorination

Answer 9

• aim is to destroy microbes which cause disease in humans

1) chlorination (inactives cell by reaction with hypochlorous acid causing undissociation, effective below ph 7-8)
- leaves a residual effect
- effective for enteric bacteria + viruses
- not effective- on protozoan cysts

Question 10

explain the disinfection of drinking water: ozones

Answer 10

• gives oxygen + free hydroxyl radicals
• generally effective
• no residual effect

Question 11

explain the disinfection of drinking water: coagulation + filtration

Answer 11

• for removal of protozoal cysts + nematode eggs
  -reduces viral conc.
  protozoan oocysts removed by special filters