bacteriological analysis of water & chlorination of boreholes/wells
TRANSCRIPT
Bacteriological Analysis of Water & Chlorination of Boreholes/Wells - Practical Training
6-8 July, 2016 Gutu, Zimbabwe
12-14 July, 2016 Matobo, Zimbabwe
Oxfam
Zimbabwe National Water Authority
Ministry of Health and Child Care
Sections to Be Covered in this Training
Section 1 – Types and importance of “indicator bacteria”
Section 2 – Collection of bacteria samples in the field
Section 3 – Using DelAqua kits for bacteria analysis of water
Section 4 – Compartment Bag Tests for bacteria analysis
Section 5 – Chlorination of boreholes/wells
Section 6 – Field testing - chlorine residual, pH and turbdity
Section 7 – Links for DelAqua training videos online
Types of Indicator Bacteria
• Thermotolerant (Fecal) Coliform Bacteria are an indicator of contamination by feces (“fecal”) from humans and/or animals
• “Total Coliform” include both non-fecal coliform bacteria (from plants, etc.) and fecal coliform bacteria
The More Fecal (or E. coli) Bacteria in Drinking Water the Higher the Risk of Cholera, Typhoid, etc.
Poster at Gutu District Laboratory
High Risk Groups – Waterborne Disease
While all ages are at risk from cholera, certain groups are at significantly higher risk of waterborne disease/diarrhea/mortality. Higher risk groups include:
• Children less than 5 years old (especially less than 2)
• People living with HIV/AIDS
• Pregnant women
• Malnourished children
• Elderly
• People who drink water from a surface water source
Important to Identify Sample Location, Time and Date of Collection and Sample Number on Whirl-Pak & in Notebook
For Group Discussion
• Assuming a limited budget, what locations/water sources should be a priority for bacterial analysis?
• How many/how often are bacteria samples are currently being taken in your work area?
• What are the current problems in collecting and analyzing an adequate number of samples?
Oxfam-DelAqua Water Testing Kit
• DelAqua bacteria testing kit was developed by Oxfam to be able to be used in areas without reliable electricity
• It uses a membrane filtration approach to analyze “thermotolerant” coliform bacteria which are also called “fecal coliform” bacteria and also “total coliform” bacteria the higher risk of disease (e.g. typhoid, cholera, etc.)
Sterilising Petri Dishes and the Media
Possible methods to use to strerilise petri dishes and media:
1. Autoclave
2. Pressure cooker
Methanol Warning
• Methanol must be stored safely away from children (in a lab or office). It can be deadly if it is drinken. It should be used in well ventilated areas.
• For general lab cleanup ethanol is less toxic and would be better.
• It should not be used to wash hands.
Using the Absorbent Pad Dispenser, Place One Pad Into Each Petri Dish
Petri-dish
Absorbent pad dispenser
Tip - If absorbent pad dispenser is broken, tweezers (sterilised with lighter) can be used
Lower The Membrane Filter onto an Absorbent Pad (that already has had medium poured in it)
Starting at the edge of the petri dish, use a rolling motion to place the membrane filter on top of the absorbent pad (with medium). This will prevent air being trapped between the pad and the membrane filter.
Incubation of Samples
• All 16 petri dishes must be placed in the Incubator regardless of how many have samples
• To ensure proper and even heating of the samples
• Samples must be in the incubator for 16 to 18 hours for DelAqua and 18 hours for Wagtech Potatest
• Thermotolerant (faecal) coliform samples set at 44 degrees C and Total Coliform at 37 degrees C
Sample on the right = 0 CFU/100 but how many thermotolerantcoliform bacteria you think are on the sample on the left?
Sample on Right is “Diluted” 10 to 1 by Only Filtering 10 mL of Sample Instead of 100 mL (Why?)
Results on right must be multiplied by 10 to get bacteria/ 100 mL since only 10 mL was used for test?
For discussion:How many bacteria/100 mL (dots) would you report for the sample on the right?
For Group Discussion
•What does it mean to dilute the sample for bacteria analysis?
•When do you want to dilute (use a smaller volume of water) samples?
For Group Discussion
• What steps should be taken if the fecal (“thermotolerant”) coliform bacteria in the drinking water sample tested are greater than 5 and/or greater than 10 CFU/100 ml?
• Who should take the steps?
Dewatering Boreholes/Wells after Chlorinating
• For boreholes, the volume of water to be dewatered is not that large so can be dewater by pumping to waste using the hand pump (test chlorine residual to know if enough water was wasted)
• For “deep wells” (dug wells) the volume of water is much larger so hand pumping to waste is not adequate. Generally a submersible pump and generator would be needed.
High Turbidity in Wells
• High turbidity after a rehabilitated well has stabilized can be a sign of poor protection at the top of the well allowing surface water contamination (usually during the wet season)
• During the dry season it is usually caused by inadequate cleaning of the well as part of rehabilitation/installation
• High turbidity (> 20 NTU) can interfere with chlorination of wells
Use of Turbidity Tube from DelAqua Kit
For discussion: Why and when should we measure turbidity?
Gutu, Zimbabwe (7-7-2016) Photos by T. Mahin
Examples of Chlorine Residual Field Testing Equipment
• Comparator (“pool tester”)
• Chlorine test strips
For Discussion: Why Is it important to check the chlorine residual before doing bacteria analysis after rehabilitating boreholes/wells?
•What will be the impact on bacteria analysis if the water being tested has chlorine in it?
•What could the source of chlorine be for boreholes or deep wells?
•How can sample be collected to prevent having chlorine in the sample?
To Check Chlorine Residual Fill the Comparator Cells with Sample Water
• For a tap sample let the water run for at least 1 minute
• For a sample from a hand pump, pump some water to bucket or waste prior to collecting sample
DelAqua Training Videos Online (web sites checked on 7-3-2016)
Media preparation training video (4 min, 1 sec.):
https://youtu.be/ls1pA7f_6ho
Sterelising petri dishes and media training video:
https://youtu.be/9agCi4IfZlU
Sterelising the filtration apparatus training video:
https://youtu.be/0eILlwRpsjY
• Counting colonies training video:
https://youtu.be/5vgrJ2UYzM0
User Manuals
• For the DelAqua Manualhttp://www.oxfam.org.uk/equipment/catalogue/resources-included-available/water-and-sanitation/water-treatment-and-testing/Delagua%20english_manual_2000-1.pdf
• For the Wagtech Potatest Manualhttp://www.palintest.com/application/files/9514/5546/6923/Potatest_User_Manual_EN_LR.pdf
Information Source Credit
• Many of the pictures of the Oxfam-DelAqua equipment and instructions on its use has been copied from either the Oxfam-DelAqua users manual and/or the DelAqua training videos.
Thank you for your participation!
For questions about this presentation you can email Tom Mahin at: [email protected]