Biological Water Quality Testing

1
Biological Water Quality Testing

• Membrane Filter Test
• (Practical)

2
The DELAGUA Test Kit
3
Filtration Apparatus
4
Pre-field

• Sterilize equipment
• Prepare media
• Check field kit (checklist in back of manual)

Consumables Culture medium Membrane
filters Absorbant pads and dispenser DPD No 1
tablets DPD No 3 tablets Phenol
Red Methanol Daily reports and marker, pens Paper
towels/clean cloth Clean water

• Equipment
• Filtration apparatus
• sample cup cable
• vaccuum cup
• petri dishes
• Turbidity Tubes
• Chlorine/pH comparator
• Tweezers
• Spares box
• Lighter

5
Sample Collection
From tap - let water run 1 min - use sterile
sample cup or rinse 3x
From flowing water - collect sample against
current

• From surface water source
• collect sample from
• 30 cm below surface

Where necessary . . . - lower sample cup into
water using 2m cable
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Field tests

• Turbidity
• Chlorine
• pH

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Prepare Workspace

• sterile conditions
• Clean surfaces
• Wash hands
• Work near flame
• Alternate sterilization methods
• Etc

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Prepare petri dish
Dispense broth pad onto petri dish
Pour media (2ml) onto pad
Cover petri dish
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Filter Sample (1)
Flame tips of tweezers
Place where they will not come in contact with
non-sterile items
Assemble filtration apparatus
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Filter Sample (2)
Mark sample and remove membrane from packet
Place membrane on filter support (grid-side up)
Fit the filter funnel and plastic collar
Note 3 positions - free - loose - fully tightened
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Filter Sample (3)
Pour sample into filtration funnel (note 100 ml
mark)
Attach vaccuum pump and draw sample through the
filter
Remove Filter membrane
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Filter Sample (4)
Open petri dish and carefully place membrane onto
broth pad
Replace cover and label
Stack petri dishes and place in incubator
to resuscitate (min 1 hour)
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(Re-)sterilize Apparatus /prepare for next sample
Dry sample cup
Add 20 drops (1ml) methanol
Ignite
close
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Incubate

• Resuscitate allow minimum 60 minutes before
  turning incubator on
• 44 C, 16-18 hours ? thermotolerant (e.coli)
  bacteria
• 37 C ? total coliforms (must adjust incubator)

15
Count Colonies

• Count yellow (thermotolerant)
• colonies 1-3mm diameter
• If two colonies merge, count as 2
• If many colonies, use grid to divide plate and
  multiply
• gt 100 colonies, test is only an estimate
• Lawn implies too numerous to count
• ?colonies ?size due to competition for food

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Cleanup/Disposal

• Sterilize absorbent pad and filter (burn)
• Wash petri dishes with soap and water before
  storing sterilize before next use
• Wipe inside of incubator with alcohol

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Questions / Comments
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Your turn!
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Practical MF Test
2. Filter
1. Feed
3. Incubate
4. Sterilize
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Practical Count Colonies