DelAgua Portable Water Testing Kit User Manual

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The DelAgua Kit Components 1

DELAGUA PORTABLE

WATER TESTING KIT

USER MANUAL VERSION 5.1

DELAGUA PORTABLE

WATER TESTING KIT

USER MANUAL VERSION 5.1

DelAgua Portable Water Testing Kit User Manual

Revised May, 2017

This equipment was designed to test for the critical parameters specied in World Health Organization (WHO) Guidelines for Drinking Water Quality, Second Edition, Volume III.

The equipment should only be used by trained personnel familiar with those guidelines.

For more information about the kit and for technical help and guidance, please contact DelAgua Water Testing Ltd.

DelAgua Water Testing Ltd,

The Old Dairy, Lower Fyeld,

Marlborough, Wiltshire, SN8 1PY

Tel: +44 1672 861 198 Fax: +44 1672 861 724 Email: info@delagua.org Website: www.delagua.org Facebook: www.facebook.com/delaguawater Twitter: www.twitter.com/del_agua

Copies of this manual are available in several languages. Please consult our website for current availability. Abridged versions of the manual are available to download.

If you regularly use the DelAgua water testing kit and have translated the manual into another language, please send us the translation. Under these circumstances, we normally organise printing and give free copies to the programme which provided the translation.

We are continually trying to improve the DelAgua water testing kit and because of this, some components may be different from those which appear in the manual. We also welcome suggestions from users about ways for improving the kit to meet their own particular needs.

Note: Text with this symbol draws your attention to additional information.

Caution: Text with this symbol contain

information on health and safety. They enforce best practice methods and protect users and others against accidents, injury or hazardous contamination when using the kit.

Video Link: Headings with this symbol

indicate that there are video sequences

which accompany the manual instructions. These videos can be found on our website

www.delagua.org .

Step No. Numbers in a blue circle

indicate the incremental steps of

a procedure which should be followed in numerical order.

 Indicates the section continues on the next

page.

 Signies the end of the section.

Note: The main sections of this manual describe the use and maintenance of the single incubator water testing kit. The additional procedures for the operation of the dual

incubator kit are described in Appendix J.

Training

Manual Icon Key

Purchasers of the kit are entitled to participate in a one-day course at DelAgua. We can also carry out training via webinar if this is more convenient. The course is free of charge.

Alternatively, you can nd step-by-step videos of all the key processes on our website

www.delagua.org. 

Please contact us at info@delagua.org for more information.

1. The DelAgua Kit Components

1.1 The DelAgua Kit

1.2 Filtration Apparatus and Components

1.3 Contents of the Spares Case

1.4 Additional Materials Needed for Testing

2. Sampling Programmes

2.1 Selection of Sites and Frequency of Sampling on a Network Supply

3. Preparation of the Kit

3.1 Sterilisation of the Filtration Apparatus

3.2 Preparation of Culture Medium in the Laboratory

3.3 Preparation of Culture Medium in the Field

3.4 Storage of Culture Medium

3.5 Sterilising the Petri Dishes

3.6 Disposal of Contaminated Material

3.7 Absorbent Pads and Dispenser

3.8 Methanol Dispenser

4. Sampling Methods

4.1 Sampling from a Tap

4.2 Sampling from a Lake, Reservoir or other Surface Water Sources

4.3 Sampling from an Open Well or Storage Tank

5. Processing of Samples Using the Kit

5.1 Introduction

5.2 Analysis of Free and Total Chlorine Residual and pH

5.3 Turbidity Analysis

5.4 Bacteriological Analysis of Water

6. Care and Maintenance of the Kit

6.1 The Battery

6.2 Electrical Components and The Incubator

6.3 Filtration Apparatus

6.4 Chlorine/pH Comparator and Turbidity Tubes

6.5 Kit Case

6.6 Maintenance

8 9

14 16

19 20 20

22 23 24

26 27 29

42 43 43 43 43

Contents

46 48

56 58

63 64 66 67 68

7. Evaluation and Repair of the Kit

7.1 Troubleshooting Guide for the DelAgua Kit

7.2 Checking and Recalibrating the Incubator

Appendices

APPENDIX A APPENDIX B APPENDIX C

APPENDIX D APPENDIX E APPENDIX F APPENDIX G APPENDIX H APPENDIX I APPENDIX J APPENDIX K APPENDIX L APPENDIX M

Spares List Field Checklist Alternative Types of Media that can be used with the DelAgua Kit for the Isolation of Coliform Bacteria Appropriate Sample Volumes for Coliform Analysis Assembly of the Filtration Manifold Daily Report Sheet Alternative Sources of Water for Media Preparation Safety Guidelines General Hygiene in the Field Additional Instructions for Operating the Dual Incubator Kit Three Power Sources for the Incubator

Counting Colonies

Incubator Electronic Circuit Diagram

8 DelAgua Water Testing Kit Manual | Version 5.1

1. Portable Incubator

2. 2 Part Turbidity Tube

3. 48 Petri Dishes in Strap Housing

(3 × stacks of 16)

4. Empty Methanol Dispenser

5. Electronic Timer

6. Kit Manual

7. Empty Media Bottles × 10

8. Thermometer

9. Calibration Lid

10. Incubator Lid

11. Filtration Manifold

12. Vacuum Pump

13. Sample Collection Cup

14. 10 Disposable Pipettes

15. Chlorine/pH Comparator Block

16. Phenol Red Tablets (250 Tablets)

17. DPD1 Tablets (250 Tablets)

18. DPD3 Tablets (250 Tablets)

19. Membrane Lauryl Sulphate Broth – 38.1g

20. Membrane Filters

21. Sterile Pads

22. Pad Dispenser

1.1 The DelAgua Kit

The DelAgua Kit Components 9

1. Vacuum Cup

2. Vacuum Pump

3. Vacuum Pump Connector

4. Vacuum Pump Connection

5. Black Rubber O-Ring

1.2 Filtration Apparatus and Components

6. Aluminium Gasket

7. Silicone Rings (Pair)

8. Bronze Disc

9. Funnel (marked 10ml, 50ml, 100ml)

10. Plastic Collar

10 DelAgua Water Testing Kit Manual | Version 5.1

1. Box

2. External Battery Connection Cable

3. Trimmer Tool

4. Tweezers

5. Elastic Strap

6. Steel Sampling Cable

7. Handheld Magnier

8. Lubrication Grease

9. Fuse

10. Bronze Disc

11. Silicone Rings (Pair)

12. Black Rubber O-Ring

1.3 Contents of the Spares Case

The DelAgua Kit Components 11

Note: It is recommended that you fully recharge the battery in all new DelAgua kits

(Section 6.1) and check the operating temperature of the incubator on receipt

(Section 7.2).

To use the DelAgua water testing kit, the following materials are also required:

For preparation of culture medium:

1. Pressure cooker, portable steriliser or autoclave.

2. Electric heating element, gas burner, stove or similar to heat the portable steriliser or pressure cooker.

3. Distilled water (for alternatives see Appendix G).

4. Means of measuring distilled water e.g. measuring cylinder or graduated beaker.

For using the kit in the eld:

1. Methanol (for alternatives see Section 3.1).

2. Paper towels or clean cloths.

3. Wax pencil or marker pen.

4. Report sheets (see Appendix F).

5. Lighter, matches or other sources of ame.

1.4 Additional Materials Needed for Testing

12 DelAgua Water Testing Kit Manual | Version 5.1

• Samples should be taken from locations that are representative of the water distribution network and household connections.

• Where there are several sources and a mixed distribution system, it is necessary to take account of the variation that may exist in the system and incorporate this into the sampling programme.

• Where there is a branched distribution system, samples should be taken at random points evenly spread throughout the system.

• Where there are main branches and a remote periphery (as shown), attention should be devoted to both the main branches and remote points in the network.

2.1 Selection of Sites and Frequency of Sampling on a Network

Supply

Minimum Frequency of Sampling and Analysis of Piped Water Supplies:

POPULATION SERVED MINIMUM FREQUENCY OF SAMPLING

Less than 5,000 One sample per month

5,000 to 100,000 One sample per 5,000 population per month

More than 100,000 20 samples monthly plus one extra sample per 10,000 population

2. Sampling Programmes



Sampling Programmes 13

Recommended Minimum Frequency of Sampling and Analysis of Unpiped/ Point Water Supplies:

Source: Adapted from WHO Guidelines for Drinking-Water Quality Volume III. Second Edition, Geneva,

1985.

* For a full, comprehensive description of sanitary protection measures, please refer to the referenced WHO guidelines (above).

SOURCE & MODE OF SUPPLY

BACTERIOLOGICAL PHYSICAL/

CHEMICAL

REMARKS

Open well Sanitary protection

measures * and testing

only if situation

demands

Once initially for community wells

Pollution usually

expected to occur

Covered well. Shallow tube well with handpump

Sanitary protection

measures * and testing

only if situation

demands

Once initially.

Thereafter as situation demands

Testing needed when environmental conditions change or when an

outbreak or increase in waterborne disease

occurs

Deep tube well with handpump

Once initially.

Thereafter as situation demands

Once initially.

Thereafter as situation demands

Testing needed when environmental conditions change or when an

outbreak or increase in waterborne disease

occurs

Springs and piped supplies

Once initially.

Thereafter as situation demands

Test periodically for

residual chlorine if water is chlorinated

Testing needed when environmental conditions change or when an

outbreak or increase in waterborne disease

occurs

Community rain water collection systems

Sanitary protection

measures * and testing

only if situation

demands

Not needed

Note: We would recommend that you refer to the WHO website (www.who.int) for the latest advice regarding sampling and analysis of water supplies. 

14 DelAgua Water Testing Kit Manual | Version 5.1

Take the plastic collar and secure the ltration funnel in the loose but not free

position (see Section 5.4.3 [pg. 35]) which will allow the formaldehyde gas to penetrate all areas of the lter head. 

The vacuum cup and the ltration apparatus (below) must be sterilised before use and re-sterilised between samples when analysing water from two different sources.

Sterilising equipment in the eld presents some practical difculties. The simplest method is with methanol, which is described below. When methanol is burnt in a low oxygen atmosphere — for example, in the closed vacuum cup — formaldehyde gas is produced as a by-product of combustion. Formaldehyde gas is a very effective disinfectant.

Note: Methanol is expensive to

freight and requires special

transport conditions. We would recommend that you try to obtain methanol in-country from a pharmaceutical supplier, a local hospital or university laboratory. If necessary, however, methanol can be supplied by DelAgua on request. If methanol is not available, the ltration apparatus and vacuum cup can be sterilised by immersion in boiling water

for 10 minutes.

Methanol is the only alcohol suitable

for sterilising the ltration apparatus;

there is no substitute.

3.1 Sterilisation of the Filtration Apparatus

3. Preparation of the Kit

Preparation of the Kit 15

Pour about 10–15 drops of methanol into the vacuum cup.

Ignite the methanol in the vacuum cup

using a cigarette lighter. Place the cup on a at surface which will not be damaged by heat.

Caution: Keep the sample cup

turned away from your face and tilted slightly to prevent methanol running onto your hand. Methanol is

extremely ammable when in contact

with a naked ame.

Caution: Filtration apparatus will

be hot. Be careful when handling

Allow the methanol to burn for several

seconds and, when almost completely burned up (i.e. as the ames are dying down), place the ltration head over the vacuum cup and push rmly into place to form a good seal.

Keep the ltration apparatus sealed for at least 15 minutes before use. 

2 3

16 DelAgua Water Testing Kit Manual | Version 5.1

The culture medium will be a bright red colour when dissolved. (Below) 

Wash the plastic polypropylene bottles in clean, warm water before use. If necessary, use

a little detergent and then rinse well with clean

water to remove all traces of the detergent.

Measure out 500ml of distilled water

using the measuring cylinder or graduated ask. Decant approximately 400ml of the water into the clean ask or beaker.

Add the 38.1g of MLSB powder to the

distilled water in the clean ask or beaker and stir until the powder has dissolved. Gentle heat can be applied if the powder is slow to dissolve. Use the remaining 100ml of water to rinse out the MLSB pot, then add this to the beaker. Stir to thoroughly mix the broth.

3.2 Preparation of Culture Medium in the Laboratory

You will need the following items:

1. 38.1g of Membrane Lauryl Sulphate Broth (MLSB) *

2. Distilled water. ** Check that the pH of the water is between 7.0 and 7.8 using the

comparator and phenol red tablets (Section 5.2)

3. Ten polypropylene bottles (60ml)

4. Measuring cylinder or graduated ask

5. Clean ask, approximately 1 litre capacity

6. Pressure cooker, portable steriliser or autoclave ***

7. Heating element, stove or burner if using a pressure cooker or portable steriliser

* The medium is available in 38.1g, pre-weighed amounts from DelAgua ** See Appendix G for suggested alternative sources of water *** A portable steriliser kit is available from DelAgua

Note: Sterilise the ltration apparatus immediately after each analysis. In this way, the ltration apparatus is always ready for use. 

Method

Preparation of the Kit 17

If you DO NOT have access to an

autoclave, then a household pressure cooker or portable steriliser may be used. Place the bottles in a rack inside the cooker (they may melt if placed directly on the base of the cooker), replace the lid and heat to full pressure (about 1 bar or 15psi).

Once the cooker has reached full pressure,

allow steam to release from the valve for 5 minutes, then time the 15 minutes sterilisation

cycle using a stopwatch or clock. At the end of the 15 minutes, switch off the heat and allow the cooker to cool until it is comfortable to touch. Remove the media bottles and tighten the caps.

Label the bottles to indicate sterilised

contents and the date and batch of medium. 

Pour approximately 50ml (no less than 40ml) of culture medium into each of

the 10 polypropylene bottles. This provides sufcient medium in each bottle to carry out 16 tests; the maximum that can be performed in one day using the DelAgua kit.

Replace the screw caps on the polypropylene bottles. Ensure the caps

are secure but DO NOT tighten. Leaving the caps slightly loose prevents the bottles from collapsing during sterilisation.

If an autoclave is available (above), sterilise the bottles at 121°C (equivalent

to 1 bar, or 15psi steam pressure) for 15 minutes. Tighten the caps carefully once the medium has cooled.

Caution: MLSB is a ne, but

non-hazardous powder; avoid

creating excess dust which may irritate the nose or upper respiratory tract if inhaled. Spillages can be cleaned up using water and an absorbent cloth.

18 DelAgua Water Testing Kit Manual | Version 5.1

3.3 Preparation of Culture Medium in the Field

You will need the following items:

1. 38.1g of Membrane Lauryl Sulphate Broth (MLSB) *

2. Distilled, or clean water **

3. Ten polypropylene (60ml)

4. Measuring cylinder or graduated beaker

5. Portable steriliser *** or pressure cooker or cooking pot or pan

6. Heating element, stove or burner

* The medium is available in 38.1g, pre-weighed amounts from DelAgua ** See Appendix G for suggested alternative sources of water *** A portable steriliser kit is available from DelAgua

Method

Wash the plastic polypropylene bottles in clean, warm water before use. If

necessary, use a little detergent and then rinse

well with clean water to remove all traces of

the detergent.

Use distilled water if possible. If this is not available obtain the cleanest water

possible. DO NOT use water that has been treated with chlorine or any other chemical disinfectant.

Use the comparator and phenol red tablets in the kit to check that the pH of

the water is between 7.0 and 7.8. If it is not, it will be necessary to nd an alternative source of water.

Measure out 500ml of clean water in a beaker.

Add 38.1g of the MLSB powder to the 500ml of water in the beaker. Mix to

dissolve the powder completely. Apply gentle heat if the powder is slow to dissolve.

The culture medium will be clear with a bright red colour when dissolved.

Pour a suitable volume of culture

medium (approximately 50ml, but no less than 40ml) into each of the 10 polypropylene bottles. This is sufcient medium in each bottle to carry out 16 tests; the maximum that can be performed in one day using the DelAgua kit.

Replace the screw caps on the

polypropylene bottles. Ensure the caps are secure but DO NOT tighten. Leaving the caps slightly loose prevents the bottles from collapsing during sterilisation.

If a pressure cooker is available, sterilise

the culture medium as described in

Section 3.2 [4–6].

If a pressure cooker or portable steriliser

is NOT available, the medium can be sterilised using a process called Tyndallisation.

Tyndallisation procedure on following page. 

Preparation of the Kit 19

Tyndallisation: This procedure takes 3 days.

1. Place the bottles of culture medium into a cooking pot or pan of boiling water, taking care to ensure that the bottles do not come into contact with the base of the pan (use a rack or stand) or become submerged.

2. Boil for 20 minutes.

3. Leave the medium to stand for 24 hours at room temperature (20–30°C) in the dark.

4. On the following day heat the medium in boiling water for a further 20 minutes and, once again, leave to stand for 24 hours.

5. On the third day repeat the heat treatment.

6. The medium should now be sterile. 

• Sterile MLSB will be stable for up to 6 months if stored in a refrigerator (between 4 and 6°C).

• Alternatively, the medium can be stored for up to 3 months in a cool, dark place.

• If the medium has been stored for several days below 6°C a deposit may form which

dissolves when the medium is warmed and

gently shaken. The deposit is caused by the lauryl sulphate coming out of solution.

• If signs of deterioration are observed, e.g. cloudiness or yellow colouration (as shown in the image to the right), the contents of the bottle must be discarded. 

• Wash the dishes in a solution of mild detergent, rinse thoroughly with clean water and dry.

• Assemble the dishes into batches of 16 in the straps. 

3.4 Storage of Culture Medium

3.5 Sterilising the Petri Dishes

20 DelAgua Water Testing Kit Manual | Version 5.1

Options for Sterilising:

• Sterilise the petri dishes in an autoclave, steam steriliser or pressure cooker at 121°C for 15 minutes (see Section 3.2 [5 & 6]). OR

• Place the dishes in a conventional oven at 180°C for 30 minutes. OR

• Plunge the bases and lids of the dishes into boiling water for 10 minutes. Pour away the

water and assemble the dishes as they dry, but while they are still hot. OR

• Add a few drops of methanol (or ethanol) to a clean cloth and wipe the inside of the lid and the base of each petri dish. Assemble the petri dishes and allow the alcohol to evaporate before use.

Whenever possible, always use one of the above methods. If this is not possible, then the following method can be applied: ame the bases and lids of the dishes with a lighter or gas burner using the tweezers to hold the bases and lids. Assemble while still hot. 

Caution: To minimise the risk of infection from contaminated materials,

take care not to touch contaminated membranes directly with your hands. DO NOT eat, drink or smoke while handling contaminated materials. Wash your hands immediately after you have touched any contaminated material and after you have nished your work.

3.6 Disposal of Contaminated Material

Contaminated material must be disposed of safely. DO NOT discard contaminated membranes and pads into the environment. After you have completed analysis place the pads and membranes in a biohazard bag and destroy by incineration. Wash the petri dishes with detergent after use, rinse with clean water and dry prior to sterilisation. 

The pads are supplied sterile in packs of 100 units. A pad dispenser is also supplied with the kit. NEVER leave the dispenser without a pack of pads attached as it will increase the possibility of contamination. If the dispenser is lost or damaged, pads may be dispensed in the eld using the sterile tweezers (see Section

5.4.3 [4] for sterilisation methods). 

3.7 Absorbent Pads and Dispenser

Preparation of the Kit 21

3.8 Methanol Dispenser

The methanol dispenser is supplied with

a plastic cap and dispensing nozzle. The dispenser should be half-lled with methanol using a small funnel, pipette or syringe to avoid spillage. DO NOT overll the methanol dispenser as it may leak in hot weather.

To dispense methanol, lever the dispensing

nozzle into the upright position with the tip of

the ame sterilised tweezers. Be sure to close the dispensing nozzle after using the kit as the methanol will evaporate.

Caution: Methanol is highly ammable. Keep methanol away

from naked ames. 

Push the tube of pads onto the dispenser.

Turn over, as shown. Hold over the petri

dish and slowly pull the plastic slider towards yourself to release a pad. Carefully drop onto the petri dish. 

1 2

22 DelAgua Water Testing Kit Manual | Version 5.1

Remove any attachments from the tap; e.g. nozzles, pipes, etc. and wipe around

the tap with a clean cloth.

Open the tap and leave water running for at least one minute before taking

a sample. DO NOT adjust the ow of water during this time. This ensures that any deposits

in the pipes are washed out and the water sample is representative of the water in the

supply pipes.

Take a water sample with the non-sterile

sample cup (as shown in the image to

the right). Rinse the cup twice with the sample water before taking the sample. Analyse the sample for chlorine residual and turbidity using

the methods in Sections 5.2

and 5.3 respectively.

If the chlorine residual and turbidity results suggest that there is a risk

of microbiological contamination (see

Section 5.1), then take a second sample for

bacteriological analysis. 

4.1 Sampling from a Tap

4. Sampling Methods

Sampling Methods 23

If it is dangerous or inconvenient to take

a sample by hand, the sample cup can be lowered into the water from a rm area of riverbank or river crossing by fastening the 2m sample cable to the hole in the lip of the sample cup (as shown above). 

Where there is safe and adequate access to the source it may be possible to

take samples by hand.

Grasp the sample cup rmly, keeping your ngers clear of the top of the cup to avoid contamination, and dip the open mouth of the cup into the water. Rinse the cup twice with

the sample water before taking the sample.

Submerge the cup about 30cm below the

surface of the water and scoop up the

water sample (as shown in the top right image).

This scooping action ensures that no external

contamination enters the sample cup.

In areas where there is a current ow, e.g. rivers and streams, the sample should be taken against the current ow.

4.2 Sampling from a Lake, Reservoir or Other Surface Water Sources

Note: It is important that you

obtain a sample which is representative of the main body of water. For example, when sampling from a river, DO NOT sample the quiet or stagnant areas near the bank, as these do not represent the main body of water. Furthermore, it is vital not to

introduce external contamination into

the sample. For this reason it is often better to sample with the help of the cable supplied with the kit.

24 DelAgua Water Testing Kit Manual | Version 5.1

4.3 Sampling from an Open Well or Storage Tank

iii

To fasten the sampling cable to the cup,

feed the looped end of the cable through the hole in the side of the cup. Pass the other end of the cable through the loop and pull rmly. Alternatively, the clip on the end of the cable can be fastened to the hole.

If necessary, increase then length of the cable by attaching a rope or string to the

sample cable.

Lower the sample cup into the well or

tank, taking care not to allow the cup to touch the walls of the structure where it may pick up dirt. Submerge the cup to a depth of 30cm. 

Equipment

Alongside the DelAgua Kit we offer a wide

range of products from suppliers such as Hach, Hanna Instruments & Lovibond Tintometer.

Training Videos

Our step-by-step videos work alongside the manual to show the key processes.

Headings with the video link symbol (shown above) indicate there are video sequences online to accompany the manual instructions.

Case Studies

See examples of the DelAgua Kit in use all over the world. To work with us on your own case study please get in touch at marketing@

delagua.org.

Library

Our online library provides a wealth of information on water, sanitation and other environmental topics.

There are over 4,000 products to view on our website.

WWW.DELAGUA.ORG

VISIT THE DELAGUA WEBSITE

26 DelAgua Water Testing Kit Manual | Version 5.1

5.1 Introduction

Chlorine pH Turbidity

IF the results of the analysis are as follows:

Free chlorine residual

>0.2mg/litre (0.2ppm)

Turbidity <5 NTU.

It is unlikely that the sample will contain thermotolerant (faecal) coliform bacteria and therefore it MAY NOT be necessary to carry out thermotolerant coliform analysis.

If the results DO NOT meet these criteria, it will be necessary to carry out thermotolerant coliform analysis. (see Section 5.4) 

• The rst tests that should be carried

out on a drinking water sample are the determination of chlorine residual, pH and turbidity.

• The results from these tests will indicate

whether or not the water sample is likely to

contain living microorganisms and whether

it is necessary to carry out analysis for thermotolerant coliform bacteria.

• The sample must be taken in a clean, but not necessarily sterile cup, e.g. the sample cup. Rinse the cup several times with the water that is to be analysed before taking a sample for analysis (see Section 4).

5. Processing of Samples Using the Kit

Processing of Samples Using the Kit 27

Replace the lid of the comparator and

push down rmly to seal. Invert the comparator several times until the 2 tablets have dissolved completely. If the tablets are

slow to dissolve use the plastic paddle from

inside the box of tablets to crush and mix the tablets in the sample water.

DO NOT shake the comparator as this will introduce air bubbles.

Immediately read the free chlorine residual (mg/litre) and pH by holding

the comparator up to daylight and matching

the colour in the cells with the standard colour

scales. If the colour falls between two standard colours, then it will be necessary to estimate the concentration.

Record the result on the daily report sheet (see

Appendix F for an example). 

Wash the comparator cells three times

with the water that is to be analysed and then ll both cells with the sample.

Drop one DPD No.1 tablet into the right

hand cell (Cl2) and one Phenol Red tablet

into the left hand cell (pH).

5.2 Analysis of Free & Total Chlorine Residual and pH

1 2

3 4

Phenol Red DPD No.1

28 DelAgua Water Testing Kit Manual | Version 5.1

To test for total chlorine residual,

DO NOT discard the liquid in the

comparator. Remove the lid and add one DPD No.3 tablet to the right hand cell (Cl2).

Again, invert the comparator several times to dissolve the tablet. Leave the

colour to develop for 10 minutes. Read the total chlorine residual (mg/litre) by matching

the colour in the cells with the standard colour

scale (as shown in the image below).

Subtract the free chlorine result from the total chlorine result to obtain the

combined chlorine concentration:

SUMMARY

Phenol = pH

DPD No.1 = Free chlorine residual

DPD No.1 plus DPD No.3 = Total chlorine residual

Total - Free Chlorine = Combined chlorine

5 6



Processing of Samples Using the Kit 29

Hold the tube vertically and slowly pour

the water sample into the tube until the marker disappears when viewed from the top of the tube. Avoid creating bubbles, as this may cause false readings.

DO NOT strain to see the black circle as this can sometimes cause biased results. 

Look through the open end of the tube

at the black circle printed on the yellow base of the tube; this is the marker. Ensure that there is good illumination available. If possible, hold the turbidity tube over a white surface, this makes visibility of the black circle clearer.

Carefully remove the 2 halves of the

turbidity tube from their clips in the lid of the case. Push the upper tube (open at both ends) squarely into the lower tube and align the graduation marks up the side.

Note: The turbidity tube covers the range 5 to 2,000 NTU

5.3 Turbidity Analysis

30 DelAgua Water Testing Kit Manual | Version 5.1

Alternatively, the procedure can be

carried out in reverse by filling the tube with the sample and then slowly pouring out the water. Keep pouring until the black marker is visible.

Hold the tube vertically and read the

turbidity using the graduations on the side of the tube (as shown in the image to the left). The result is the value of the line nearest the water level.

Note: The graduations follow a logarithmic scale with the most

critical values marked on the side of the tube, allowing a reasonable estimation. Alternatively, you can judge the distance of the water level from the 2 nearest graduation marks to calculate a more accurate value. 

Processing of Samples Using the Kit 31

Caution: Microbiological analysis presents some risks to the health and safety of yourself and others. It is vitally important that safety guidelines are adhered to when

carrying out analysis. (See Appendix H for more safety information.)

5.4 Bacteriological Analysis of Water

Analysing water samples for thermotolerant coliforms:

• A measured quantity of water is passed through a sterile lter.

• Any bacteria present in the water are caught on the lter.

• The lter is placed on a pad soaked in liquid growth medium which feeds coliform

bacteria and inhibits the growth of other bacteria.

• They are incubated at 44°C; this ensures only thermotolerant bacteria grow.

• During this time coliform bacteria, if present, multiply many times to form colonies that can be seen with the naked eye.

• Thermotolerant coliforms are recognised

by their ability to produce a colour change (from red to yellow) in the culture medium.

• Results are expressed as colony-forming units per 100ml of water (CFU/100ml).

5.4.1 Introduction

Thermotolerant coliforms are of sanitary signicance when present in drinking water supplies. Users should refer to country specic water quality standards or guidelines, or to the latest edition of the World Health Organization Guidelines for Drinking Water Quality (available online at www.who.int) to decide when action should be taken to improve contaminated water supplies.

Some users may need to analyse for total coliform bacteria, which, although of less sanitary signicance than thermotolerant coliforms, can be used to indicate hygiene problems in large distribution networks. Total coliform analysis is carried out using the same procedure, the only difference being that the lters are incubated at 37 °C.

The DelAgua incubator can be recalibrated to 37°C by following the recalibration procedure in Section 7.2. However, this is not convenient when carrying out both thermotolerant coliform and total coliform analysis on a regular basis. A dual incubator kit (see Appendix J) is available from DelAgua which allows both tests to be carried out simultaneously. 

32 DelAgua Water Testing Kit Manual | Version 5.1

The most appropriate volume to process is that which allows the most accurate count of

the bacterial colonies. It is generally agreed that 100 colonies is the maximum that can be counted reliably on a 47mm membrane. Counts above 100 are considered an estimate.

If a large number of colonies develops on the membrane you can either divide the plate into sections, count the colonies in one section and multiply the count by the number of sections,

5.4.2 Selection of Appropriate Sample Volumes for Coliform Analysis

5.4.3 Sample Processing for Thermotolerant (Faecal) Coliform Analysis

or repeat the analysis with a smaller volume of the sample and then adjust the result to give a count per 100ml of the original sample.

The selection of the most appropriate sample

volume for a given source, treatment plant or distribution system is normally best made in the light of previous experience. For sites

where this information does not exist see

Appendix D for guidance on sample volumes. 

Allow the medium to warm to ambient

temperature before use. Pipette enough culture medium onto the absorbent pad in the petri dish to soak the pad and leave a slight excess (approximately 2.5ml), this prevents the pad drying out during incubation.

Note: During sampling, processing components of the kit

should be kept free from dirt and contamination (see Appendix I). 

Using the absorbent pad dispenser,

place one pad into each petri dish (this

operation may be done at base before leaving for the field).

*If the dispenser is damaged, the pads can be

dispensed using the sterilised tweezers (see

page 33).

Processing of Samples Using the Kit 33

If bubbles appear on the pad use the

pipette to suck these away. Bubbles (as shown in the image to the right) can cause inaccurate results.

To sterilise the tweezers, flame the

tips with a lighter for approximately 5 seconds and leave to cool.

Note: Once the bottle of culture medium has been opened, it is

recommended that the contents are

used within one day. It is not advisable to use the medium in one bottle over several days since this can lead to contamination.

Place the heel of the tweezers into the

test kit case (as shown in the image to the right). This ensures that the tips are kept away from all sources of contamination whilst analyses are in progress. 

34 DelAgua Water Testing Kit Manual | Version 5.1

Using the sterile tweezers, carefully

remove a sterile membrane filter from the packet. Hold the membrane only by the edge and do not let the membrane filter touch anything while it is being transferred to the filtration apparatus. 

Remove the sterile vacuum cup from the

filtration apparatus. Push the filtration apparatus firmly onto the vacuum cup (see

Appendix E for assembling the filtration

manifold). Place the assembly in an upright position in a convenient place in the kit.

DO NOT place the apparatus on the ground

where it may become soiled.

Unscrew the plastic collar and filtration funnel in order that these may be easily

removed. DO NOT place these on any surface other than the filtration base.

Processing of Samples Using the Kit 35

Screw the plastic collar down tightly to provide a watertight seal between the

filter membrane and the filter funnel. 

With one hand, lift the filtration funnel and plastic collar above the filtration

base.

With the tweezers in your other hand, place the membrane filter (grid side facing upwards) onto the bronze disc filter support. Replace the filter funnel and collar immediately, without allowing them to come into contact with any external objects. Hold the funnel between the thumb

and forefinger to ensure that the collar will not slip off and that the fingers do not come into

contact with the interior surface of the funnel.

Note: The plastic collar has 3 adjustment positions:

1. Completely free – the apparatus can

be dismantled when in this position.

2. Loose but NOT free – all interior

surfaces are exposed to the

atmosphere. This is the position used when sterilising the apparatus.

3. Fully tightened – the funnel forms

a tight seal between the membrane support and the membrane lter. This is the position for ltration.

36 DelAgua Water Testing Kit Manual | Version 5.1

Pour the sample into the filtration funnel

up to the appropriate mark (10, 50 or 100ml) engraved on the internal surface of the funnel (as shown in the image to the right). To avoid damaging the membrane, tilt the filtration apparatus and carefully pour the first

few millilitres of water down the inside of the

filter funnel. Return the filtration apparatus to

the upright position and continue adding the

sample.

Rinse the sample cup once with the

water before taking the sample. Take

care not to allow external contamination

(e.g. dirt and debris) to enter the sample cup.

Insert the plastic connector of the

vacuum pump into the vacuum

connection on the filtration base. Squeeze the pump bulb several times to draw a vacuum,

then squeeze as required to draw all the water

through the membrane filter.

When all the water has passed through the filter, disconnect the pump from the filtration apparatus. DO NOT allow excess air to be

drawn down through the filter once all the

water has gone through. 

Processing of Samples Using the Kit 37

Replace the lid of the petri dish and

mark the lid with sample information e.g. volume filtered, source, time and date; or a code which relates to details on the daily report sheet. A wax pencil or marker pen is suitable for this purpose (the writing needs to be easily removed after the tests are complete). 

Unscrew the collar and remove the

funnel and collar with one hand. Using the sterilised tweezers in the other hand, lift the membrane carefully from the filtration base. Hold the membrane by the edge only.

Remove the lid of a prepared petri dish

and place the membrane, grid side up, onto the absorbent pad soaked in culture medium. Start at one edge (it is easier to use

the one at a greater distance from the wall of

the petri dish) and lower the membrane on to the pad by ‘rolling’ so as to avoid trapping air bubbles under the membrane.

14 15

38 DelAgua Water Testing Kit Manual | Version 5.1

Resterilise the filtration apparatus (Section 3.1). 

Place the petri dishes into the carrier

with the blank sample at the top, followed by the negative (see below for more information on blank and negative samples). Return the carrier to the pre-heated incubator pot.

Note: Each site of testing should have 3 dishes dedicated to it. This includes a negative and two actual samples (duplicates). One “stack blank” plate should be

included for each bottle of media used.

The reasons for this stack format are as follows:

Blank plate – One pad soaked in media in a petri dish. This demonstrates effective sterility of the plates and media, which ensures that any positive results are NOT originating from contaminated plates and/or media.

Sample Negative – Filter clean water (this does not need to be deionised water, but MUST be free from contamination and chlorine) through a membrane following the above process. After incubation this should show no colonies, this demonstrates effective sterility of the ltration manifold at each sample point.

Duplicates – This process ensures that erroneous results due to human error or other means are likely to be picked up due to the chances of exact error repetition being lower.

Note: All 16 petri dishes must be

in the rack during incubation. This allows for an even distribution of heat during the incubation cycle.

Processing of Samples Using the Kit 39

Note: It is not possible to close

the kit lid if you are using the dual incubator kit or if you are powering the kit using the charger or another external power source.

• Once the last sample of the day has been

taken, wait for a minimum of 60 minutes before switching on the incubator (resuscitation time).

• Try to plan the day so that the time between processing the rst and last sample is NO MORE than 3 hours. This restricts the resuscitation time to a maximum of 4 hours. In cold weather resuscitation can be achieved by keeping the samples close to the body (e.g. in hands or upright in a pocket but take care to avoid media leaking from the petri dishes).

5.4.4 Resuscitation of Bacteria

5.4.5 Sample Incubation

• Resuscitation time is particularly important for chlorinated waters or marine water

where the thermotolerant coliform bacteria are ‘stressed’ due to environmental exposure.

• For these types of waters it is benecial to leave processed membranes for 4 hours after the last sample has been processed before switching on the incubator. 

• Incubate the samples for 16 to 18 hours.

Only put the stack of petri dishes in the incubator when it reaches temperature. The incubator is designed to maintain a temperature of 44°C +/- 0.5°C. When the incubator is switched on both lights should turn on ('power' & 'heating'). When the 'heating' light turns off the incubator has reached temperature.

• Always incubate the petri dishes with the incubator lid (without hole) and case lid closed to reduce heat loss and save battery power.

There are 3 power source options for the incubator:

1. Mains electricity supply via the

charger unit

2. Internal battery

3. External 12v battery (or your vehicle battery) 

• Place the kit on a chair or table to prevent heat loss through the oor and avoid incubating samples outdoors during cold weather. In order to maximise battery life, DO NOT leave the incubator on for more than the incubation period, i.e. 16 to 18 hours.

40 DelAgua Water Testing Kit Manual | Version 5.1

Note: It is important that counting is completed as soon as possible after the petri dishes have been removed from the incubator (certainly within 15 minutes) as the

positive colonies will change colour on cooling and standing.

5.4.6 Counting Colonies and Recording Results

Once the incubation period is complete,

remove the petri dishes and their holder

from the incubator. Carefully lay the plates out, in sample order, on a table to allow effective results comparison.

Check the stack blank first. The result of

this particular plate will dictate if ANY of

the other plates can even be considered. If the stack blank is positive then either the media or the plates could be contaminated. A negative

Squares 3mm × 3mm

Yellow colonies

Note: It is recommended that the mains supply option be used wherever possible. When used in this way, the charger unit will operate the incubator and at the same

time charge the battery. If the mains electricity fails the internal battery will operate the incubator. (See Appendix K for more information). 

stack blank will appear the same colour as the original media, possibly with slight lightening due to a temperature/pH change. A positive stack blank will likely be a yellow colour. The indicator in the media (phenol red) will change its colour from red to yellow as the pH drops due to biological activity. In the event of a yellow stack blank, all other samples should be discarded and the process repeated. 

Processing of Samples Using the Kit 41

Once the stack blank is considered as negative, assess the samples one at

a time. First assess the sample negative; a

positive result will demonstrate ineffective

manifold sterility at that site only. If the negative shows positive growth and/or a

change in the colour of the media then discard

the samples for that site as they cannot be assessed as valid. A negative result for a negative control will have a pink membrane with zero “spots” or “dots” of any colour.

Next check the duplicate samples for

the site of the negative control. The first observation should be of the colour and condition of the membrane and any liquid remaining in the dish. If the sample appears as per the negative control, this indicates a negative result for that sample site. If the dish is quite dry and the membrane appears dry then it is likely there was insufficient media in the dish at point of processing. This would

Count all the yellow colonies (as shown) which have a diameter of between

1mm and 3mm. If necessary use the hand lens provided (See Appendix L for more information on counting colonies).

Convert the count into number of thermotolerant coliforms per 100ml

and record the result on the daily report sheet (see Appendix F). The calculation is made as follows:

mean that any growth from that sample could be compromised and it would be good practice to repeat the process for that site. If the dish shows yellowing of the membrane and

media then that indicates positive presence

of coliforms. If the media and membrane still appears red, but there are spots and bumps on the surface of the membrane, this also indicates a positive result for coliforms in that sample.

VOLUME FILTERED THERMOTOLERANT COLIFORMS PER 100ml

100ml Number of colonies × 1

50ml Number of colonies × 2

10ml Number of colonies × 10

1ml Number of colonies × 100

5.4.7 Disposal

Caution: All contaminated materials should be sterilised before disposal to avoid creating a risk to the public. DO NOT discard contaminated membranes and lter

pads into the environment. Refer to Section 3.6 for recommended procedures to sterilise contaminated materials. 

42 DelAgua Water Testing Kit Manual | Version 5.1

6.1 The Battery

To Recharge the Battery:

• Connect the charger to the left hand side of

the incubator.

• Plug the 3-pin plug from the charger unit into the mains electricity supply and switch on. Check that the incubator is switched off unless it is in use.

• The LED on the charger will be an orange/

amber colour which will eventually turn

green. Once it has turned green the battery

will be usable but will not run for the ve full incubation cycles. Ensure the battery is charged for 72 hours after the LED turns green, to be able to run the incubator for ve full cycles.

• When the battery is completely charged, switch off the charger, disconnect the charger from the mains electricity supply and the incubator and store in a safe place.

Note: When using the kit in low

temperature environments, e.g. less than 10°C, the maximum number of 18 hour incubation cycles on one battery charge SHOULD NOT

exceed 3. 

6. Care and Maintenance of the Kit

DOs DON’Ts

P ALWAYS incubate samples with the

incubator lid rmly in place and the kit lid closed.

P ALWAYS operate the incubator in a

vehicle or indoors, on a chair or table to prevent heat loss through a cold oor if possible.

P ALWAYS Recharge the internal battery

at the end of a period of work in the eld.

P ALWAYS Leave the battery in a charged

state when the kit is out of use or in storage. During storage, recharge monthly.

Ï NEVER allow the internal battery to

discharge completely. The useful life of the battery will be maximised if the battery is always kept in a well-charged state. If the kit is in storage, recharge the battery once a month.

Ï NEVER operate in cold weather.

Ï NEVER leave the incubator switched on

for more than 18 consecutive hours.

Care and Maintenance of the Kit 43

6.2 Electronic Components and the Incubator

6.3 Filtration Apparatus

6.4 Chlorine/pH Comparator and Turbidity Tubes

6.5 Kit Case

• DO NOT allow water to enter the base of

the kit.

• The electronic components are sealed during construction and this allows a certain

tolerance of moisture. However, always immediately dry any spillage of water or other liquids inside the kit.

• The temperature of the incubator should be checked periodically, e.g. every month. For

additional information (see section 7.2.1) 

• At the end of each day, it is good practice to

carefully dry all components of the ltration apparatus, including the vacuum and sample cups, and to sterilise the apparatus.

• Avoid scratching the comparator and

turbidity tubes. They rely on an adequate transmission of light for accurate results.

• Keep the surfaces clean and dry and free of residues that may prove difcult to remove once dry. After use, always wash in clean water.

• This practice prevents corrosion of the

metal components. 

• Approximately once a month wash the comparator and turbidity tubes in a dilute

solution of mild detergent and rinse

thoroughly with clean water. 

• The outer case is robust and can withstand a certain amount of harsh treatment. However, try to avoid abrasion and hard impacts. Periodically clean the case with warm water and mild detergent.

• NEVER use acids or organic solvents. 

44 DelAgua Water Testing Kit Manual | Version 5.1

6.6 Maintenance

WEEKLY MONTHLY

1. Wash, rinse and dry the ltration

apparatus

2. Apply a smear of silicone grease to the black rubber O-ring

3. Charge the internal battery fully at the end of each week

1. Check the incubator temperature and recalibrate if necessary

2. Clean all components of the kit,

including the case

3. Check all components for damage that may affect the operation of the kit 

Don't forget to restock your consumables

The availability of consumables is a key factor in ensuring the ongoing utility of a kit in the field. These packs allow for forward planning of testing programmes and high volume testing as required.

Bacteriological Consumables Pack (200 Plates)

Includes: 200 Pads, 200 0.45µ Filters, 38.1g MLSB Tub and Pad

Dispenser

Consumables Pack with Non-rapid Tablets (200 Plates)

Includes: 200 Pads, 200 0.45µ Filters, 38.1g MLSB Tub, Pad Dispenser, 250pk DPD No1 Tablets (non-rapid), 250pk DPD No3 Tablets (non-rapid) and 250pk Phenol Red Tablets (non-rapid).

Consumables Pack with Rapid Tablets (200 Plates)

Includes: 200 Pads, 200 0.45µ Filters, 38.1g MLSB Tub, Pad Dispenser, 250pk DPD No1 Tablets (rapid), 250pk DPD No3 Tablets (rapid) and 250pk Phenol Red Tablets (rapid).

Consumables Expansion Pack (2400 Plates)

Includes: 2,400 Pads, 2,400 0.45µ Filters , 500g MLSB Tub, 1 Set of Portable Scales (3 decimal points), 13 Weigh Boats, 10 60ml Media Bottles and 3 Media Mixing Bottles.

For pricing and availability contact us at sales@delagua.org

DELAGUA CONSUMABLES

46 DelAgua Water Testing Kit Manual | Version 5.1

7. Evaluation and Repair of the Kit

7.1 Troubleshooting Guide for the DelAgua Kit

7.1.1 Problems with Charging the Internal Battery.

7.1.2 Attempting to Calibrate the Incubator, but the Incubator is not

Reaching or Maintaining the Desired Temperature.

Connect the charger to the incubator and plug into the mains. Switch the mains on. The LED on the charger should be an orange/amber colour which will eventually turn green. Once it has turned green the battery will be usable but will not run for the full ve incubation cycles. Ensure the battery is charged for 72 hours after the LED turns green, to be able to run the incubator for ve full cycles.

If the two lights on top of the incubator DO

NOT illuminate at all when connected to the

mains, the main fuse may have blown. Ensure

the charger unit is disconnected from the

If the battery has been charged and the lights are illuminated, but the incubator is

not reaching or maintaining a temperature

between 43.5 and 44.5°C the incubator is damaged. A repair kit is available from DelAgua. Contact an electronics technician to carry out repairs or contact DelAgua.

If the lights DO NOT illuminate, connect the incubator to the charging unit and connect to mains. If the incubator then reaches and

maintains temperature this means there

is a fault with the battery and will require replacement.

Note: Between each cycle, leave the incubator to cool for

at least 8 hours.

mains and replace the fuse. Reconnect to the incubator and plug into the mains, if the lights still do not come on then there could be two

reasons for this; either the charger is damaged

or the battery is completely dead. Replacement chargers and/or batteries are available through DelAgua.

If the LED on the charger DOES NOT turn

green, this is an indication that the charger

is damaged and will require a replacement. Replacement chargers are available from DelAgua. 

The incubator should be able to maintain a temperature of between 43.5 and 44.5°C for ve incubation cycles of 18 hours each, without needing to recharge the battery.

If this is not the case, the battery is damaged or worn out. Battery replacement should be carried out only by qualied electronic technicians. A battery replacement kit is available from DelAgua. 

Evaluation and Repair of the Kit 47

Disconnect the battery charger from the incubator and connect the incubator to a well charged 12v battery using the lead with crocodile clips supplied with the kit. Switch on the incubator unit. If the lights still do not illuminate then the incubator is damaged. A repair kit is available from DelAgua. Contact an electronics technician to carry out repairs or contact DelAgua.

If the lights do illuminate, there could be a fault with the charger. If the charger is tted with a 3pin UK style plug, the main fuse may have

7.1.3 The Charger Unit is Connected to the Incubator and the Mains

Electricity is Turned On, but the Lights do not Illuminate.

Note: For any technical

assistance relating to the

DelAgua Kit please contact us on

(+44) 1672 861 198. 

blown. Ensure the charger unit is disconnected from the mains and replace the fuse. Reconnect to the incubator and plug into the mains, if the

lights still do not come on then the charger is

damaged and must be replaced or a repair can be carried out through DelAgua. 

48 DelAgua Water Testing Kit Manual | Version 5.1

7.2.1 Procedure for Checking the Incubator Temperature

Note: Carry out the following procedure at an ambient

temperature of between 15 and 25°C.

Remove ALL contents from the kit

and wipe clean the internal surfaces

with a clean, damp cloth or paper towel. Pour approximately 50ml of clean water into the incubator pot (giving a depth of approximately 20mm).

Push the thermometer through the hole in the testing lid.

Replace the incubator lid with

the calibration lid (with hole) and thermometer assembly. The bulb of the thermometer should be completely immersed in the water, but be careful not to crack the bulb.

Ensure that the internal battery is

completely charged, or that the kit is operating from a mains electricity supply or well-charged external 12v battery. Switch on the incubator.

Check the temperature of the incubator

and observe over a period of 30 minutes to make sure that it has stabilised. The incubator normally takes no more than 3 hours to reach a stable temperature, depending on the ambient temperature.

Once the incubator has stabilised, if

the temperature is between 43.5 and

44.5°C, then recalibration is not necessary and the water may be removed with tissue or a cloth. If the temperature is not within these limits, follow the recalibration procedure. 

7.2 Checking & Recalibrating the Incubator

Note: It is recommended that the temperature of the incubator is checked once every month. 

The equipment supplied for checking and recalibrating the incubator includes the following items:

1. Testing incubator lid with centre hole

2. Thermometer

3. Trimmer tool (similar to a small screwdriver)

Evaluation and Repair of the Kit 49

7.2.2 Procedure for Recalibrating the Incubator

Leave the testing lid and thermometer assembly in place and keep the incubator

switched on.

Insert the trimmer tool into the hole on

the side of the unit and locate the tool in

the calibration screw (blue trim).

To increase the temperature, turn

the adjustment screw clockwise. To decrease the temperature, turn the adjustment screw anti-clockwise. Make the adjustments in stages, a ¼ turn at a time. After each adjustment, leave the incubator to stabilise for at least 30 minutes. The complete recalibration procedure may take several hours.

Once the incubator has been

recalibrated to read between 43.5 and

44.5°C, leave it switched on for at least 3 hours. Take note of the temperature at 30 minute

intervals to ensure that the temperature is

stable.

The following day, switch on the

incubator and allow it to reach a stable temperature. If the temperature is not within the correct limit, repeat the recalibration process detailed in STEPS 1 to 4.

Dismantle the temperature checking

equipment and store in a safe place. Empty the water out of the incubator and dry the inner surfaces.

Switch off the incubator and leave to cool. DO NOT disconnect the incubator

from the mains electricity supply.

Note: The above procedure

guarantees an average incubator temperature of 44°C +/- 0.5°C. After reaching the set temperature, the temperature in the incubator may vary within +/- 0.5°C during incubation. 

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APPENDIX A

APPENDIX B

APPENDIX C

APPENDIX D

APPENDIX E

APPENDIX F

APPENDIX G

APPENDIX H

APPENDIX I

APPENDIX J

APPENDIX K

APPENDIX L

APPENDIX M

Spares List

Field Checklist

Alternative Types of Media that can be used with the DelAgua Kit for the Isolation of Coliform Bacteria

Appropriate Sample Volumes for Coliform Analysis

Assembly of the Filtration Manifold

Daily Report Sheet

Alternative Sources of Water for Media Preparation

Safety Guidelines

General Hygiene in the Field

Additional Instructions for Operating the Dual Incubator Kit

Three Power Sources for the Incubator

Counting Colonies

Incubator Electronic Circuit Diagram

Appendices

52 DelAgua Water Testing Kit Manual | Version 5.1

APPENDIX A - Spares List

Kit Components:

Optional Extras:

All of the listed spares and consumables are available from DelAgua. Please contact us for a current price list.

• Portable conductivity meter

• Portable steriliser kit

Other items of equipment for the analysis of a range of chemical parameters can be supplied upon request. DelAgua also offer expansion consumables packs allowing for forward planning of testing programmes and high volume analysis.

Battery replacement kit containing:

• Battery 12v 9.5Ah

• Silicone sealant

Temperature check kit containing:

• Incubator calibration lid with hole

• Thermometer

• Adjuster/trimmer tool

Electrical repair kit containing:

• Electrical circuit

• Temperature chip

• Sealant

• Foam compound

• Adhesives

Other Spares:

• Filtration apparatus (complete)

• Spares box (specify empty or complete)

• Filter funnel with plastic collar

• Tweezers

• Aluminium Gasket

• Chlorine/pH comparator

• Vacuum cup

• Vacuum pump

• External battery cable

• Sample cup

• Battery charger

• Silicone grease (2g or 100g)

• Sample cable

• Polypropylene bottles 60ml

• Bronze disc

• Plastic methanol dispenser

• Black rubber O-ring

• Petri dishes

• Turbidity tube

• Thermometer

Appendices 53

Consumables:

Membrane lters and absorbent pads

• Pad dispenser

• Culture medium: 38.1g tub for 500ml of growth medium (sufcient for 200 plates)

• Culture medium: 500g tub for 6.5 litres of growth medium (sufcient for 2,600 plates)

• DPD No.1 Tablets

• DPD No.3 Tablets

• Phenol Red Tablets

Alternatively, visit our website at www.delagua.org for more information.

54 DelAgua Water Testing Kit Manual | Version 5.1

APPENDIX B - Field Checklist

Kit

DelAgua incubator in pelican

case

Filtration apparatus

Sample cup

Sample cable

Turbidity tubes (pair)

Chlorine/pH comparator

Tweezers

Petri dishes in strapped housing

Spares box (complete)

Incubator lids

Thermometer

Other Items

Culture medium (one bottle per

day and a spare)

Membrane lters

Absorbent pads and dispenser

DPD No.1 tablets

DPD No.3 tablets

Phenol red tablets

Methanol in dispenser

Daily report sheets (Appendix F)

Paper towels or clean cloth

Some clean water to rinse the

equipment after use

A wax pencil or marker pen

Lighter/matches

Gloves

Pasteur pipettes

Instruction manual

Before leaving for the eld, check that you have the following items:

Appendices 55

APPENDIX C - Alternative Types of Media that can be Used with the DelAgua Kit for the Isolation of Coliform Bacteria.

MEDIUM USES INCUBATION TEMPERATURE CHARACTERISTICS OF

POSITIVE COLONIES

CHARACTERISTICS OF

NEGATIVE COLONIES

Membrane Lauryl Sulphate (MLSB)

Total & Thermotolerant

Coliforms

37°C - Total Coliforms

44°C - Thermotolerant Coliforms

Incubation Time - 18hrs

Yellow colonies. Colour density

may vary

Red, pink, colourless,

occasionally blue-grey

m Endo Broth Total Coliforms 35°C for 24 hours Red to red-black colonies with a

golden-green metallic sheen

Light red or colourless

M-F C Medium Thermotolerant

Coliforms

44.5°C for 24 hours Blue colonies Generally pale brown, cream,

colourless

m-ColiBlue 24 Broth Total Coliforms & E.Coli 35°C for 24 hours Coliforms produce red colonies,

E.Coli produces blue colonies

Possible range of colours but

not red or blue

MI Broth (You will need a UV light)

Total Coliforms & E.Coli 35°C for 24 hours Coliforms produce colourless,

cream or pale yellow colonies and

uoresce under UV light

Colonies do not uoresce

under UV light

Teepol NutriDisk (Available as

membrane pad impregnated with the

medium. Not readily available in any

other form)

Total & Thermotolerant

Coliforms

37°C - Total Coliforms

44°C - Thermotolerant Coliforms

Incubation Time - 24hrs

Yellow colonies. Colour density

may vary

Red, pink, colourless,

occasionally blue-grey

Tergitol - TTC (Available as membrane

pad impregnated with the medium. The

powered agar medium is not suitable

for use with the kit)

Total & Thermotolerant

Coliforms

37°C - Total Coliforms

44°C - Thermotolerant Coliforms

Incubation Time - 24hrs

Yellow-orange colonies with a

yellow-orange halo under the

colony.

Colourless, pink or red.

Note: The list is not exhaustive, but includes the most readily available culture media that may be used with the DelAgua kit.

New media are being developed all the time and some may be suitable for use with the kit. The important characteristics to

look for in a medium are that it should be a broth (liquid) medium that can be used with the membrane ltration technique. Some

broth media are intended for use with the multiple tube method of analysis (most probable number) and will not work with the

membrane ltration technique. Check the instructions on the product information sheets. Agar-based (solid) media also are not

appropriate for use with the kit due to the shallow design of the petri dishes. Some media require the use of supplements to improve

the yield of the target organism, check the instruction sheet carefully. Always read the safety data sheets for the medium before use

and check the colony characteristics for the target organism.

56 DelAgua Water Testing Kit Manual | Version 5.1

APPENDIX D - Appropriate Sample Volumes for Coliform Analysis

Treated Water and Water in Piped Distribution Systems

Recommended sample volumes for each source are shown below.

Suggested sample volumes for thermotolerant coliform analysis by the membrane ltration

technique (alternative volumes are shown in brackets).

SOURCE SAMPLE VOLUME

Waters in treatment plants after partial treatment 50ml (100ml or 10ml)

Waters in treatment plants after full treatment 100ml

Reservoirs, distribution networks and household taps 100ml

SOURCE SAMPLE VOLUME

Lakes, ponds and other surface waters 10ml (1ml*)

Protected groundwater, e.g. wells and springs 100ml (50ml or 10ml)

Unprotected groundwater, e.g. open dug wells and

springs

50ml (10ml or 1ml*)

*Note: This volume will require the use of sterile pipettes and distilled or dechlorinated water.

Historically, the microbiological quality of drinking water has been assessed using the number of bacteria present in a standard volume of 100ml. Treated water and water in a piped distribution network are unlikely to contain large numbers of thermotolerant coliform bacteria. For these waters we would recommend using a 100ml sample.

Suggested sample volumes for thermotolerant coliform analysis by the membrane ltration

technique (alternative volumes are shown in brackets).

Other Water Sources

Appendices 57

Note: These volumes are only a guide. They DO NOT represent absolute

recommendations to be applied to sampling programmes. It may be useful to analyse different volumes of the same sample in order to decide the best range in which to count the bacteria. It is not necessary to sterilise the ltration apparatus and sample cup between two analyses of the same sample provided that the smaller volume is processed rst.

58 DelAgua Water Testing Kit Manual | Version 5.1

Push the bronze disc into the middle.

The large ring acts a platform for the disc

to be placed onto. The disc should be smooth side up.

Place the large silicone ring into the circular space in the gasket.

Then place the smaller silicone ring on

top.

APPENDIX E - Assembly of the Filtration Manifold

Aluminium Gasket Silicone Rings (pair) Bronze Disc

Screw the plastic collar and filter funnel down tightly.

1 2

3 4

Appendices 59

Push the filtration apparatus firmly

onto the vacuum cup. If this is difficult, lubricate the black rubber O-ring with silicone grease.

Note: When storing the ltration manifold it is advisable to lubricate the black O-ring with silicone grease.

60 DelAgua Water Testing Kit Manual | Version 5.1

APPENDIX F - Daily Report Sheet

Source of

sample

Time Colour Odour Turbidity

(NTU)

Chlorine (mg/L) pH Thermotolerant Coliforms (TTC)

Free (DPD

No.1)

Total (DPD

No.3)

Combined

(total-

free)

Vol.

filtered

(ml)

No. of

colonies

TTC per

100ml

Health Region:

Date: / /

Province:

Community:

Comments:

Authority:

Code:

District:

Analyst:

Appendices 61

APPENDIX G - Alternative Sources of Water for Media Preparation

Note: We would strongly recommend that you try to nd a source of distilled water to prepare the medium, with a pH between 7.0 and 7.8. However, we appreciate that

this may not always be possible and would suggest the following as suitable alternatives:

• A high quality bottled water that has not been treated with chlorine or any other disinfectant that has a residual activity.

• Rainwater. Collect a sufcient volume of rainwater in a clean container and leave it to stand overnight to allow any suspended matter to settle out. Carefully pour off the water into a separate clean container. Alternatively, the rainwater can be claried by ltration through a membrane lter or, more quickly, through one of the membrane pads.

• Water from a well-protected groundwater source. Groundwater from a well-protected source is usually suitable for preparing the medium. However, check the pH of the water before use to be sure that it is not too acidic or alkaline.

• Sodium Thiosulphate tablets can be used as a dechlorinating agent. Add two tablets to 500ml water that may contain chlorine and shake until they are completely dissolved. The water will then be suitable to use for medium preparation. These tablets are available from DelAgua.

• De-ionisation packs can be used in situations where distilled or de-ionised water is not readily available. DelAgua are able to supply a portable de-ionisation pack. This is simply lled with around 500ml of clean water, and shaken for approximately 5 minutes. Each pack will produce approximately 4-5L of de-ionised water before being depleted and responsibly discarded. This is indicated by a simple colour change of the beads in the pack, from Blue to Yellow/White.

62 DelAgua Water Testing Kit Manual | Version 5.1

APPENDIX H - Safety Guidelines

It is vitally important that you take great care when handling potentially contaminated

materials, such as the petri dishes, membranes and pads that have been used for the growth of microorganisms. Although most of the bacteria that will grow on the membrane are relatively harmless, some of the colonies may contain pathogenic bacteria.

High standards of hygiene should be applied at all times:

Ï NEVER eat, drink or smoke when carrying out microbiological tests.

Ï DO NOT touch colonies with your ngers or with everyday objects such as pens and

pencils that you may use again for other purposes.

Ï DO NOT carry out microbiological tests in food preparation areas.

Ï DO NOT dispose of contaminated materials into the environment.

P ALWAYS wash your hands thoroughly after handling contaminated or potentially

contaminated materials.

P ALWAYS cover wounds with a waterproof dressing.

P ALWAYS keep all non-essential personnel, particularly children, away from the work

area when handling contaminated materials.

P ALWAYS keep your work area clean and tidy.

P ALWAYS clean and disinfect (methanol, ethanol or a weak solution of domestic bleach

can be used for this purpose) the work surfaces after you have nished the analysis.

Appendices 63

APPENDIX I - General Hygiene in the Field

Although all components of the kit should be kept free from dirt and other contamination, there are some parts of the kit which must always be kept clean and

sterile.

These are as follows:

• All those areas in direct contact with the water sample, e.g. the internal surface of the vacuum cup, the internal surface of the lter funnel, the upper part of the ltration base and the surface of the bronze disc.

• Surfaces in contact with the culture medium, e.g. the internal surface of the petri dishes and the absorbent pads.

• Parts in contact with the membrane lters, e.g. the ltration apparatus, the absorbent pads and the tweezers.

Under NO circumstances should any of these components be allowed to come into contact with dirt, dust or external objects which may contaminate them and interfere with the bacterial count.

64 DelAgua Water Testing Kit Manual | Version 5.1

APPENDIX J - Additional Instructions for Operating the Dual Incubator Kit

Note: You must leave the lid of

the kit open when the battery pack is connected to avoid damaging the battery lead.

The dual incubator kit allows you to double the number of tests carried out at one temperature or test the same sample at 2 temperatures, typically:

• 37°C – Total coliform count (TC).

• 44°C – Thermotolerant coliform count (TTC).

The analytical procedures for TC and TTC using MLSB are identical except for the incubation temperature. Similarly, the colony characteristics of TC are the same as TTC, although you may nd a more varied colony size and differences in the intensity of the yellow colour.

Many water samples, particularly untreated water samples, will contain bacteria other than coliform bacteria that can grow on MLSB at 37°C. The colony characteristics of these background organisms will vary: only the coliform bacteria will produce yellow colonies. However, be prepared for high background counts when performing TC analysis.

There are two additional procedures that you should be aware of when operating the dual incubator kit:

The dual incubator kit is powered by an external 12V battery that is contained inside the separate battery pack. Inside the battery pack, there are two connections; one lead connects to the dual incubator and the other connects to the 2-step charger. This in turn ends in a 3-pin plug to connect the whole system into the mains supply.

• To charge the battery, connect the battery charger to the 3-pin socket and plug into the mains supply. Switch on to charge (For

charging times see Section 6.1).

• The battery pack can be connected to the

battery charger and to the kit at the same time.

Charging and Connecting the Battery

Appendices 65

Note: Each incubator has a temperature label located above it. The temperature adjuster screws are located to the side of the incubator (as shown above) and are also

labelled.

The procedure for checking and calibrating the temperature of the two incubators is the same as described in Section 7.2 for the single incubator kit. However, the corresponding temperature adjuster screws are located underneath the labels showing the incubator temperatures.

44°C

37°C

Temperature Calibration

66 DelAgua Water Testing Kit Manual | Version 5.1

APPENDIX K - Three Power Sources for the Incubator

Using Mains Electricity or Generator via the Charger Unit

When using mains electricity, the incubator can be operated and the internal battery charged simultaneously. If the power fails for any reason, the internal battery continues the incubation cycle.

When operating from mains electricity, connect the 3-pin plug to the socket in the left hand side of the incubator console. Plug the battery charger into the mains electricity socket using an appropriate plug and switch on the mains. Switch on the incubator and leave until the incubation cycle is complete.

Internal Battery

It is possible to obtain up to ve incubation cycles from the internal battery. The number of cycles will reduce as the battery ages. When using the internal battery in this way, DO NOT use the incubator for more than ve cycles without recharging the battery or run the incubator for more than 18 hours during any cycle. Always recharge the battery fully at every opportunity using mains electricity.

External 12v Battery

If you are planning to work in the eld for more than ve days, or to work in remote areas, it is possible to operate the incubator using an external 12v battery, e.g. vehicle battery, using the connection lead provided in the spares case.

To operate connect the crocodile clips on the external battery lead to the correct terminals on the external battery (Red to Positive or ‘+’, and Black to Negative or ‘−’) and connect to the left hand side of the incubator console.

Switch on the incubator and check that the ‘Power On’ indicator is lit. An external battery cannot be used to recharge the internal battery, only to operate the incubator. Very little current is drawn during incubation and it is usually safe to operate from a vehicle battery for one incubation cycle without risk of discharging the vehicle battery excessively. Only run from a car battery if the vehicle IS being driven regularly.

Note: A poorly maintained external battery may cause the internal battery to discharge.

Appendices 67

APPENDIX L - Counting Colonies

• Frequently, 2 or more colonies will merge together. It is usually clear how many have merged, count each of these.

• DO NOT count colonies that are transparent, red/pink or blue /grey. These are bacteria which do not ferment lactose and cannot be identied without further study. They are not thermotolerant coliforms.

• Colonies may vary considerably in size.

• Generally, when the membrane contains a large number of colonies, the colonies are smaller in

diameter.

• When colonies are fewer, they tend to be larger. This is because the colonies compete for nutrients and will grow larger where there is no competition.

• If there are large numbers of yellow colonies, count methodically using the horizontal grid lines.

• In this way it is possible to count up to 100 colonies on a membrane.

• If there are more than 100 colonies on the membrane, the number can be estimated by dividing

the membrane into sections and counting the number of colonies in one section.

• Multiply the result by the number of sections to obtain an estimate of the total number of colonies on the membrane.

68 DelAgua Water Testing Kit Manual | Version 5.1

APPENDIX M - Incubator Electronic Circuit Diagram

+8V

4.7K

78L08

100uF

0.1uF

1 3

BATTERY

12V

ON/OFF

SW1

R1 2.2K

123

LED1

RED LED

LED 2

R2 2.2K

DIODE D6

IN5401

DC JACK

TEMPERATURE SENSOR

THERMOSTAT NORMALLY CLOSED

LM35

HEATER

R10

4.7K

R11

560R

BC337

IN4148

U2A

LM2904

10KR833K

18K

CAP

LM385

10K

BC337

U2B

LM2904

R5AR5R4

68R

0.1uF

10K 10M 10M

2SD882

+8V

HELE-

HELE+

IN OUT

GND

OUT

VDD

GND

+12V

TSTAT

SEN IP

SEN-

SEN+

VRA

VR+

VR-

LGND

H LD+

H LD-

P LED

HEAD OFFICE

The Old Dairy, Lower Fyeld, Marlborough

SN8 1PY, United Kingdom

Tel : +44 (0) 1672 861 198 Fax: +44 (0) 1672 861 724

INFO@DELAGUA.ORG

WWW.DELAGUA.ORG

DelAgua Portable Water Testing Kit User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual