Chapter 14

Question 1

aquatic system

Answer 1

• The biological activity of an aquatic ecosystem depends, utlimately, on the activities of the primary producers (oxygenic photoautotrophs, phytoplankton; phyto=plant):
  
  1. Algae
  2. Cyanobacteria (also fix nitrogen)
  • These organisms serve as a food source for chemoheterotrophs: bacteria, protozoa (zooplankton, zoo=animal), fish, and other aquatic organisms
  • The activities and net numbers of phytoplankton depend on a variety of factors:
    1. Temperature
    2. Light received
    
    3. Availability of specific limiting nutrients such as nitrogen and phosphorous

Question 2

photic zone

Answer 2

• in clear water, light will penetrate to a max depth of 300m: photic zone
  Microorganisms must be able to harvest light that reaches them (accessory pigments)

Question 3

marine environment + open ocean

Answer 3

• High salinity (3%): organisms are halotolerant
  
  • 75% of the ocean is deeper than 1000m (deep sea, pelagic zone); at its deepest, 11 km below the water surface, pressure is about 110 atmospheres (environ 1 atm/10m)
• Below 100m the temperature is constant 2-3C

In the open ocean (pelagic zone), primary productivity is very low due to the lack of inorganic nutrients (nitrogen, phosphorous, iron) that are required by phyloplankton. The open ocean is OLIGOTROPHIC
- Tempé are cooler and more constant than areas closer to shore
In some regions, wind and ocean currnts cause an upwelling of water from the ocean floor bringing nutrients to the surface and promoting productivity

Question 4

open ocean

Answer 4

• Bulk of primary productivity comes from prochlorophytes (tiny phototrophs phylogenetically related to the cyanobacteria): prochlorococcus
  
  • General adaptations seen in pelagic (open ocean) microorganisms:
    1. Reduced size (high surface/volume ratio)
    2. High affinity transport systems
  • Trichodesmium:
    1. Filamentous cyanobacteria
    2. Contains phycobilins
    Nitrogen fixation

Question 5

coastal water

Answer 5

• Primary producers: algae, cyanobacteria
  
  • Productivity is usually higher due to the influx of nutrients from ivers and other polluted water sources (ex: agricultural runoff = excess nitrogen, phosphorus). EUTROPHIC
  • Can cause red tides (algal bloom, dinoflagellates, neurotoxins). Nitrogen is a limiting nutrient
• Higher level of primary productivity supports a higher concentration of zooplankton and aquatic animals

Question 6

deep sea

Answer 6

• Between 200 and 1000m, chemoheterotrophs degrade organic matter that falls from the photic sones. 2-3C, psychrophiles
  
  • Below 1000m, organic carbon is very scarce, oligotrophic, no light. Very few microorganisms (psychrophilic and barophilic or barotolerant)
  • Whale fall (1600m deep): a source of nutrients
    Ex of a large protist (xenophyophore) found on the deep sea flour (5000 deep), bar= 100um

Question 7

hydrothermal vent

Answer 7

• Source of heat, source of nutrients, electron donors, electron acceptors
  
  • Community of microorganisms, animals
    Tube worms: symbiosis with sulfur oxidizing chemoautotrophs. Tube worms trap and transport nutrients to the bacterial symbionts

Question 8

freshwater environment

Answer 8

• Highly variable (isolated system compared to ocean)
  
  • Microbial populations will depend on the availability of nutrients, oxygen and light. Limited by the availability of nitrogen and phosphorus
  • Lakes (poor mixing/aeration)
    Rivers (good mixing/aeration)

Question 9

oligotrophic lakes (N and P are limiting)

Answer 9

• Primary production is low, availability of organic matter is low
  
  • Growth of aerobic chemoheterotrophs is limited by nutrients supply; O2 concentrations remains high: rate of O2 dissolution is higher than the consumption rate
  • Lake remains aerobic even at depth and organic matter is degraded completely
  • Oxygen saturated
    Clear water (deep penetration light)

Question 10

eutrophic lake (nutrients rich)

Answer 10

• Primary production is high (algal bloom), availability of organic matter is high
  
  • Rapid growth of chemoheterotrophs, rapid depletion of dissolved O2
  • Low O2 concentration
  • Anaerobic zones are created
  • Poor light penetration
    Health risks: pathogens, bloom of cyanobacteria/algae (secrete toxins)

Question 11

eutrophic lake , presence of H2S

Answer 11

• Bottom sediments are anaerobic and contain organic matter (dead primary producers..) which support the growth of denitrifiers, methanogens and sulfate reducers (H2S)
  
  • Anaerobic photosynthesis uses H2S as electron donor and produces sulfate which is used by sulfate reducers
    Excessive production of H2S and the production of organic acis from fermentation can give the water a bad odoré the lack of O2 and/or presence of H2S may kill fish and other aerobic organisms

Question 12

lake in temperature climates

Answer 12

• Anaerobic zones may develop as a result of summer stratification. Lakes become thermally stratified.
  
  • As the temp. Increases, the surface water is warmed resulting in the formation of a warm upper layer- EPILIMNION- less dense, aerobic
  • The colder, bottom layer - HYPOLIMNION, denser anaerobic- is separated from the epilimnion by a zone of rapid temp. Change - THERMOCLINE
    Mixing in the spring and fall only. Brings nutrient back up the watre column

Question 13

rivers

Answer 13

• Rivers: good mixing/aeration ensures that organic matter, within limites, is degraded effectively (no fermentation, no H2S production)
  Excess organic matter may still result in anaerobic areas with consequences similar to those senn in eutrophic lakes

Question 14

pollution

Answer 14

• Pollution of freshwater: deliberate discharge of effluents into a waterway (major source is sewage)
  
  • Sewage is rich in organic matter and contains larger number of organisms (some may be pathogens)
  • Aerobic and facultative organisms oxidize organic matter using the dissolved wO2
    Biochemical oxygen demand (BOD) is high (used as a measure of the extent of pollution by organic matter). Water tends to become anaerobic, microbial metabolisms: fermentation, sulfate reduction, nitrate reduction…

Question 15

biofilms

Answer 15

• Biofilms: microbial cells embedded inside an extracellular matrix
  
  • Usually produced by a mixed population of species
  • Extracellular matric composed of proteins, polysaccharides, DNA
  • Cells inside the biofilm are more resistant ot stress than planktonic (free-living) cells
  • Biofilms are found in water systems (natural and man-made), on wet surfaces, growing on medical devices…
    4 steps
    1. Attachment: adhesion of a few motile cells to a suitablesolid surfaces
    2. Colonization: intercellular communication, growth and polyssacharides formation
    3. developmentL more growth and polysaccharides
    Active dispersal: triggere by environmental factors such as nutrient availability

Question 16

water-borne pathogens

Answer 16

• Most of these pathogens grow in the intestinal tract and transmission is mediated by fecal contamination of water supplies
  
  • Source of infection:
    1. Potable water (drinking and food preparation)
    Recreational water (swimming)

Question 17

water-borne bacteria pathogens and virus

Answer 17

1. salmonella typhi: typhoid fever in humans, systemic infection, healthy carriers
   
   2. Vibrio cholera: cholera, severe diarrhea (enterotoxin)
   3. Shigella spp.: shigellosis; bacterial dysentery (bloody diarrhea, inflammation of the intestinal mucosa)
   4. Salmonella spp. (other than typhi): salmonellosis, gastroenteritis
   5. Campylobacter spp.: gastroenteritis, most common cause of gastroenteritis in canada
   6. enterovirusL norovirus, rotavirus (children)
2. Hepatitis A virus

Question 18

water-brone pathogenic protozoa

Answer 18

• Entamoeba histolytica: amoebic dysentery
  
  • Giardia lamblia: giardiasis (backpacker’s disease/beaver fever), chronic diarrhea, often associated with drinking water in wilderness areas (beavers and muskrats are frequent carriers- source of contamination of streams)
    Cryptosporidium parvumL chronic and acute diarrhea, self limiting in healthy individuals, major problem in immunocompromised individuals, nor reliable tratment. Present in 90% sewage samples, 75% river waters (intracellular C. parvum)

Question 19

cysts of G. lamblia and C. parvum

Answer 19

• Both form cysts that are resistant to a number of disinfectants, including chlorine
  c. Parvum cysts are not effectively removed by filtration process in water plants (too small)

Question 20

water quality control

Answer 20

• Impossible to check for all pathogens. Most water-borne pathogens are associated with fecal material
  
  • Test the water for organisms that are present in large numbers in feces - these organisms are used as indicators of fecal pollution- if these organisms are present, there is a chance that the water may also contain pathogens
  • 2 indicators:
    1. coliformsL facultative aerobic, gram-negative, non spore-forming, rod-shaped bacteria that can ferment lactose with gas formation within 48 hours at 35C. Includes a variety of bacteria not all of intestinal origin.
    2. Fecal coliforms: coliforms derived from the intestines of warm-blooded animals (can grow at 44,5C, thermotolerant)
  • The presence of fecal coliforms, especially E.coli, indicate fecal contamination and that the water is unsafe for human consumption
    Absence of fecal foliforms does not ensure good water quality (cysts are more resistant than fecal coliforms)

Question 21

most probable number (MPN)

Answer 21

• Test for coliforms: samples are added to lactose broth. If gas production is detected, test is positive
  
  • Use statistical tables to estimate the MPN of coliforms in the original sample
    Presumptive tests, further testes needed for confirmation

Question 22

membrane filtration

Answer 22

• Coliforms and fecal coliforms
  
  • Test large volume of water (100ml)
  • Faster and easier than MPN
    Eosin-methylene blue medium is selctive and differential for lactose-fermenting bacteria

Question 23

water treatment

Answer 23

• Aims:
  
  1. Remove pathogens
  2. Improve clarity of water
  3. Removes compunds that give bad smell or taste
  4. Soften the water
     Extent of treatment needed depends on the quality of the source of water

Question 24

steps 1-3 water treatment

Answer 24

1) SEDIMENTATION:
- Water is left to stand in a reservoir (sedimentation bassin)
- Allow to large particle (sands) to settle

2) FLOCCULATION TREATMENT (chemical coagulation)
- A flocculating chemical (coagulant) is added
- Water is transferred to a flocculation basin and allowed to settle for 6h
- As the flocks (flaky precipitates) form, they trap fine particles (clay, bacteria, viruses, protists)
- Some organics chemicals are also absorbed by the flocs - 80% of bacteria, color and particluates are removed

3) FILTRATION
- The water is filtered through sand to remove remaining particles, even more bacteria and any remaining G. lamblia cysts
- After this stage, 98-99,5% of the bacteria have been removed Filter is backflushed regularly to prevent clogging

Question 25

step 4 of water treatment

Answer 25

4) DISINFECTION
- Chlorination:
1. Chlorine is very reactive in water, it forms stron oxidizing agents
2. Kills remaining microorganisms (some are resistant)
3. Neutralizes most of the chemicals that give water a bad smell/taste
- Residual chlorine: amount of chlorine that remains in the water leaving the treatment plant. Desired/required to protect the distributing system
- Ozone: more effective than chlorine (kills G. lamblia and C. parvum cysts) but very short half-life

- The water is now safe for human consumption
- Qaulity control (Mtl): less than 10 coliforms/100 ml ; less than 1 fecal coliform/100ml Walkerton tragedy (2300 of 5000 resdients fell ill, 7 died)

Question 26

wastewater (sewage) treatment

Answer 26

Aims:

1. Reduce BOD (remove/destroy organic matter)
2. Destroy pathogens

Steps: 
	1. Screening
	2. Sedimentation 
***(primary treatment)
	3. Anaerobic digestion (digested sludge: drying; incineration;use as fertilizer, or burial OR
	Aerobic oxidation (disefection = treated effluent to discharge)
	- Activated sludge/aeration
	- Trickling filter
** these two are secondary treatment!

Question 27

primary treatment

Answer 27

• Sedimentation tanks: 40-70% of suspended solids settle. Flocculating chemical can be added. Produces PRIMARY SLUDGE (dried and incinerated or secondary treatment)
  
  • Reduces the BOD of wastewater to 35-40% and the bacteria by 25-75%
    Wastewaers can be discharged to waterways or go through secondary treatment: use microorganisms to reduce the BOD and the concentration of bacteria further

Question 28

secondary treatment- liquid

Answer 28

1. Trickling filterL liquid from primary treatment is sprayed over a bed of rock or plastic honeycomb, microorganisms form biofilms, coating the surface and oxidize the organic matter present in the sewage. BOD reduced by 80-95%, bacteria by 90-95%
   Activated sludge: air is blown through the liquid from primary treatment. Slime-forming bacteria grow and clump together to form flocs (activated sludge) that oxdizes that organic matter. Then, the material passes to a settling tanl, sludge is removed for disposal or secondary treatment. BOD reduces by 85-95%, bacteria by 90-98%

Question 29

secondary treatment- sludge

Answer 29

• The primary and secondary sludge, containing cellulose and organic compunds, is subjected to microbial digestion under anaerobic conditions
  CH4 produced can be used to power the treatment plan. BOD reduced by 90%. Material that remains is incinerated or buried

Question 30

tertiary treatment- liquid

Answer 30

• Further reduces the BOD, bacteria and the concentration of N and P
  
  • May involve any or a combination of the followingL
    1. Biological treatment (ponds: algae)
    2. Flocculation
    3. Filtration
    4. Chlorination or ozonation
    The final liquid effluent that come from wastewater treatment plants that uses primary, secondary and tertiary treatments may be suitable for drinking (coliforms and fecal coliforms below limits)

Question 31

septic tank

Answer 31

• Minimal treatment of sewage
  
  • Within the tank: settling of the material and minimal sludge digestion (requires periodic emptying)
  • BOD of effluent reduced by 60%
  • Effluent flows to a leachinf field (tile field):
    1. Still contains more than 10,000 coliforms/ml
    2. Reduce amount of water in the tank
    Soils act as a filter and organisms decompose organic matter. Care has to be taken to prevent contamination of groundwater and nearby waterways