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Biological Water Quality Testing

Biological Water Quality Testing. Membrane Filter Test (Practical). The DELAGUA Test Kit. Filtration Apparatus. Pre-field. Sterilize equipment Prepare media Check field kit (checklist in back of manual). Consumables Culture medium Membrane filters Absorbant pads and dispenser

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Biological Water Quality Testing

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  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

  6. Field tests • Turbidity • Chlorine • pH

  7. Prepare Workspace • “sterile” conditions • Clean surfaces • Wash hands • Work near flame • Alternate sterilization methods • Etc

  8. Prepare petri dish Dispense broth pad onto petri dish Pour media (~2ml) onto pad Cover petri dish

  9. Filter Sample (1) Flame tips of tweezers Place where they will not come in contact with non-sterile items Assemble filtration apparatus

  10. 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

  11. Filter Sample (3) Pour sample into filtration funnel (note 100 ml mark) Attach vaccuum pump and draw sample through the filter Remove Filter membrane

  12. 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)

  13. (Re-)sterilize Apparatus /prepare for next sample Dry sample cup Add 20 drops (~1ml) methanol Ignite close

  14. 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 • > 100 colonies, test is only an estimate • “Lawn” implies too numerous to count • ↑colonies ↓size due to competition for food

  16. 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

  17. Questions / Comments

  18. Your turn!

  19. Practical – MF Test 2. Filter 1. Feed 3. Incubate 4. Sterilize

  20. Practical – Count Colonies

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