WATER MICROBIOLOGY

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WATER MICROBIOLOGY
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DEFINITIONS

• Potable Water Drinkable water free from
  pathogens, free from debris, taste and odor
• Safe Water Free from pathogens
• Polluted Water Possibility of pathogenic
  microorganisms
• Contaminated Water Known pathogens present or
  indicator organisms present

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• Indigenous Water Microorganisms Species of
  microorganisms that exist in water depend on the
  O2 gradient, nutritional environment, pH and
  temperature
•  
• Marine (97 of Earths water) phyto and
  zooplankton, fungi, ultramicrobacteria or
  nanomicrobacteria (Sphingomonas lt 0.2
  micrometers), virioplankton (mostly
  bacteriophages 10X the number of bacteria)
•  
• Marine microorganisms may be the source of new
  antibiotics
•  
• Freshwater cyanobacteria, anoxygenic
  phototrophic bacteria, algae

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SOURCES OF WATER

• Atmospheric Water rain water
• microbiological quality
•  
• Standing Water
• Surface Water lakes, rivers, reservoirs
• microbiological quality
•  
•  
• Underground Water aquifers, underground streams
• microbiological quality
•  

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PROBLEMS

• 1. Organisms resistant to chlorine or other
  methods of disinfection
• viruses, protozoan cysts, bacterial spores,
• organisms with extensive glycocalyx
• protection from biofilms
• clumps of bacteria
• antibiotic resistance associated with these
  organisms

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• EXAMPLES
• enteroviruses
• rotavirus
• Giardia
• Cryptosporidium
• Pseudomonas

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• 2. Low dosage organisms
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• EXAMPLES
• viruses enterovirus, rotavirus, Hepatitis
• Campylobacter
• Shigella
• Giardia lamblia
• Cryptosporidium
• Entamoeba histolytica
• Escherichia coli 0157H7

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Indicator organismsThe presence of these
organisms indicate contamination

• An Ideal Indicator
• 1. Should be associated with source of the
  pathogen
• 2. Be present when the pathogen is present at
  all times
• 3. Be absent when the pathogen is absent
• 4. Be easily detectable
• 5. Be present in greater quantities than the
  pathogen
• 6. Not multiply
• 7. Survive better than the pathogen does

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• Coliform most commonly used fecal indicator
  organism
• An anaerobic or facultatively anaerobic non
  spore forming Gram negative rod that ferments
  lactose with the production of gas in 24 - 48
  hrs. at 35 C or which creates a metallic green
  sheen or pink mucoid colonies with dark centers
  on ENDO or EMB agar
•  
• Fecal coliform same definition only at 44 C

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• Other indicator organisms
• Fecal streptococci - Enterococci
• Thermotolerant E. coli
• Coliphage

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• Tests for Water
•  
• Turbidity
• Free Residual Chlorine
• MPN Most probable number
•  

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MULTIPLE TUBE METHOD/MPN

•  Presumptive Test
• Inoculate a specified number of lactose broths
  with durham tubes with a specified amount of
  water
• Usually a total of 15 tubes
• 5 tubes with 10 ml
• 5 tubes with 1 ml
• 5 tubes with 0.1 ml
• Incubate at 35 C for 24 to 48 hrs

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Fig. 41.2
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• Confirmed Test
• Tubes with gas are inoculated into Brilliant
  Green Lactose Bile broth with durham tubes
• Incubated for 24 to 48 hrs
• OR
• Tubes with gas inoculated onto ENDO or EMB agar
  and incubated

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• Completed Test
• Tubes with gas are inoculated onto ENDO or EMB
  and incubated
• Colonies with metallic green sheen or pink
  mucoid colonies with dark centers are inoculated
  onto tryptic soy agar and in lactose broth

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CONTINUATION OF THE MPN

• Colonies are Gram stained
•  
• IMViC tests are done to determine if colonies are
  E. coli or other bacteria
•  
• Numbers of organisms are determined by taking the
  number of tubes in each category of water (10 ml,
  1 ml, and 0.1 ml) and using a statistical chart
•  
• Counts given in number of organisms per 100 ml
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MEMBRANE FILTRATION

• Filter water through 0.45 micrometer pore size
  membrane filter and incubate on ENDO agar

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INJURY RECOVERY TECHNIQUES

• use 2 layer agar
• use 2 incubation temperatures

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OTHER TESTS

• Presence-Absence Test (P-A Test)
• 100 ml. incubated in triple strength-broth
  containing lactose broth, lauryl tryptose broth,
  and bromcresol purple indicator
• positive result - production of acid (turns
  yellow)
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• Colilert
• 100 ml. incubated in medium containing ONPG and
  MUG as only nutrients
• If coliforms present the medium tuns yellow
  within 24 hrs.
• If E. coli is present the medium will become
  fluorescent under UV light
•  

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Fig. 41.3
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HETEROTROPHIC PLATE COUNT (HPC)

• plate water to get a total count of organisms per
  ml.
• does not determine if organisms are pathogens,
  but may help in determining if water treatment
  process is working or indicate other problems

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OTHER TESTS

• Psychrophiles
• plate count incubated below room temperature
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• Low nutrient
• plate count using low nutrient agar - R2A

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STANDARDS

• coliforms
• 1 found in lt 40 samples/month
• lt 5 positives found if gt 40 samples/month
•  
• no fecal coliforms, enterococci, viruses, Giardia
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WATER TREATMENT PROCESS

• 1. Sedimentation
• 2. Aeration
• 3. Chemical coagulation - use of a flocculating
  agent
• 4. Filtration
• 5. Method of Disinfecting (still have to add
  chlorine
• bec. of requirement for residual chlorine)
• Chlorination, Ozone, Other

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Fig. 41.1