Water Quality Analysis in Emergency Situations

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Water quality analysis is required in emergency situations to determine whether water is safe to drink. People who are traumatised by an emergency event and in poor health are particularly vulnerable to water related diseases including those which are spread through the drinking of poor quality water. In the initial phases of an emergency it should be assumed that all water sources are contaminated microbiologically and when water is supplied to people in camp situations, chlorination and the testing of chlorine residual should always be undertaken. For water with a low turbidity, chlorination is reasonably simple, but for water with a high turbidity, a pre-treatment process will be required to reduce the turbidity levels to
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  OXFAM – TB3 (V1) Water quality analysis in emergency situations Water quality analysis is required in emergency situations to determine whether water is safe to drink. People who are traumatised by an emergency event and in poor health are particularly vulnerable to water related diseases including those which are spread through the drinking of poor quality water. In the initial phases of an emergency it should be assumed that all water sources are contaminated microbiologically and when water is supplied to people in camp situations, chlorination and the testing of chlorine residual should always be undertaken. For water with a low turbidity, chlorination is reasonably simple, but for water with a high turbidity, a pre-treatment process will be required to reduce the turbidity levels to <5TU prior to chlorination. After the initial phase of the emergency is over, investigation can then be undertaken into the microbiological, and where appropriate, the chemical constituents of the water. This Technical Brief outlines the usual testing regime as recommended for use by OXFAM staff in emergency situations. It focuses on what is realistic during the various stages of an emergency, whilst also ensuring that water is safe for the affected populations. It looks at microbiological, physical and chemical testing parameters. It does not replace the water testing kit instruction materials but is complementary and they should be read together. The purpose of water quality analysis Pathogens such as bacteria, virus’, ova and cysts, can be ingested through drinking water. Water which looks clear may still be microbiologically contaminated or have chemical contaminants which are dangerous to health, such as arsenic or high levels of nitrates or nitrites. The biggest risk to life in an emergency situation is microbiological contamination as diarrhoeal diseases can spread rapidly in environments where large numbers of people are living in poor conditions and in close proximity. In the initial stages of an emergency, focus should be on providing an adequate quantity of water and then on good quality water microbiologically. In the initial stages of an emergency, it should be assumed that all water is contaminated and will require chlorination, particularly for piped supplies. After the initial stage is over, it is then appropriate to test the water microbiologically and also to look at other parameters of health significance or which could cause problems due to adverse colour, taste, or staining, if it is felt that they may be a significant problem. Focus on quantity and microbiological contaminants WHO (2004, p109) notes that ‘Many chemicals in drinking-water are of concern only after extended periods of exposure. Thus, to reduce the risk of outbreaks of waterborne and water-washed e.g. trachoma, scabies, skin infections) disease, it is preferable to supply water in an emergency, even if it significantly exceeds the guideline values for some chemical parameters, rather than restrict access to water, provided water can be treated to kill pathogens and can be supplied rapidly to the affected population’  . Which parameters need testing in an emergency and when? Initial phase of emergency Post initial emergency phase Faecal coliform Not unless there is a diarrhoea outbreak – assume all water is contaminated and chlorinate all supplies provided through a tap. Chlorinate open wells.  Yes, test initially after 1 month. Then test monthly. Only if there are outbreaks of diarrhoeal disease will there be a need to re-test at other times to identify if the water is the problem, or to eliminate water quality as the cause. Turbidity  Yes if chlorinating – should be <5TU  Yes if chlorinating – should be <5TU pH  Yes if chlorinating, if pH >8.0 then the retention time for contact before supply should be increased  Yes if chlorinating, if pH >8.0 then the retention time for contact before supply should be increased Chlorine residual  Yes when chlorinating  Yes when chlorinating Chemical parameters, such as arsenic, fluoride, chloride, TDS/conductivity, iron, manganese, nitrate, nitrite, aluminium or zinc, would usually only be tested after the initial phase of an emergency and then only when a specific problem is suspected through local knowledge, catchment mapping, or sanitary survey. Sanitary survey which identifies the contamination risks should be one of the key tools for determining if water quality analysis is required during the intermediary periods.   OXFAM Technical Brief – Water quality analysis in emergency situations 1  OXFAM – TB3 (V1) Minimum frequency of sampling and analysis of small community water supplies – under non-epidemic conditions (WHO Fact Sheet 2.29) Source / supply Bateriological Physical / chemical Open wells Once monthly Once monthly Covered dug wells tubewells with handpumps Twice yearly Twice yearly Springs and piped sources Twice yearly Twice yearly Rainwater collection systems Once yearly Once yearly Classification vs degree of health concern  (Wisner & Adams, 2002) 0 E.coli   / 100ml Guideline compliant 1-10 Tolerable 10-100 Requires treatment >100 Unsuitable without proper treatment Microbiological testing The degree of microbiological contamination of water is usually measured by identifying the quantity of faecal (or thermotolerant) coliform in 100ml of water. Faecal coliform live in human or animal intestines and hence when identified provide an indication that there may be pathogens present in the water. The most common of the faecal coliforms which is tested for using the membrane filtration method is the E.coli  . Most common broth types for use with the Membrane Filtration method 1. Membrane Lauryl Sulphate Broth – thermotolerant / faecal coliforms produce a colour change from red to yellow on formation of the colonies. When using the MLSB broth, the larger yellow colonies are usually E.coli  . 2. MFC broth comes in 2ml pre-packaged ampoules –– these must  be kept in a refrigerator – faecal coliform produce blue colonies. Delagua water testing kit Testing of faecal coliform in water which has been treated with chlorine If a water supply has been treated with chlorine, after a contact time of 30 minutes (for a pH<8), a turbidity of <5TU and the residual free chlorine is greater than 0.2mg/l, then it is highly unlikely that the sample will contain thermotolerant (faecal) coliform bacteria and hence analysis is usually not necessary. However on occasions it may be appropriate to test the chlorinated supply, for example to dispel concerns over the effectiveness of the treatment process by the users, or when the results are not within the above limits. When testing water that has been chlorinated, the following apply: 1. It is essential that the sample cup is totally sterile as the numbers of resultant bacteria may be very low. 2. ‘Resuscitation time is particularly important for chlorinated waters or marine water where the thermotolerant (faecal) coliform bacteria are ‘stressed’ due to environmental exposure. For these types of waters it is beneficial to leave processed membranes for 4 hours after the last sample has been processed before switching on the incubator’   (OXFAM Delagua Users Manual, 1993). OXFAM Technical Brief – Water quality analysis in emergency situations 2  OXFAM – TB3 (V1) Preparing for microbiological testing in the field Purchasing the remaining items of equipment: Even if the team has brought a full Delagua kit and associated consumables with them to the field, there will still be a need for a few items to be purchased locally. As soon as the logistics team are up and running ask them to procure: 1. 100ml of methanol – usually this will be found in a hospital laboratory if it is not possible to procure it in local chemist shops. Methanol cannot be carried in an aircraft unless it is specially packaged as it is flammable, so this poses problems for travel with a full kit in-country when flights are required. 2. A small pressure cooker. 3. A box of 2ml and 5ml syringes (without the needles if possible) – these are useful items to have available for dilutions, preparing the media and also for undertaking jar tests if chemical coagulation is needed. 4. A permanent marker pen, masking tape (if autoclave tape is not available), sealable plastic bags and a packet of tissues or antiseptic wipes. Other preparations: 1. Make sure that the instruction manual is available. 2. Check the function of the charging unit and charge the Delagua kit up to full charge. 3. Check the temperature of the incubator using the thermometer and adjust as necessary. 4. Sterilise the equipment and media – see below. Field tips for sterilisation using the Delagua kit Sterilisation of Petri dishes: The metal Petri dishes can be sterilised in the field in the following ways: 1. Use a pressure cooker – these can usually be purchased locally in most big cities and towns. 2. Boil the metal dishes in a saucepan of water. Care must be taken when removing them from the water and storing them for use. Use sterilised tweezers and place the Petri dishes on a sterilised surface before putting into a sealable bag and taping with masking tape to ensure they remain sealed until use. Sterilising the MFC broth: 1. Prepare the broth and sterilise the bottles at full pressure for about 15 mins. The bottles should not touch the bottom of the pressure cooker and should be supported vertically throughout. The lids should only be loosely tightened. 2. If no pressure cooker is available then place the bottles of medium in a cooking pan of boiling water, making sure that they do not come into contact with the bottom of the pan and remain vertical throughout, and boil for 20 minutes. Preparing the sample cup and filter funnel: 1. Follow the instructions for sterilising the sample cup and filter funnel by lighting methanol and inverting the filter funnel into the sample cup and leaving for 15 minutes. 2. If methanol is not available then immerse the filtration apparatus and sample cup in boiling water for 5 minutes. 3. If methanol is not available, or there is not enough time to leave between samples to use the methods of sterilisation, then subsequent samples can be tested if the filter funnel and the sample cup are thoroughly washed in the water of the new sample, several times. The first sample must be the sample which is expected to have the least amount of contamination and the subsequent samples expected to have increasing levels of contamination. This method should be used only as a last resort. Microbiological testing – alternative kits The OXFAM Delagua Kit as designed by the Robens Institute at the University of Surrey which uses the membrane filtration method, is still the most widely used equipment and method, but still has a number of constraints. There are also a number of alternative methods currently on the market, but none have so far have exceeded the membrane filtration method in terms of the provision of useful results. Three of the currently available alternative methodologies are identified in the table below and compared against the membrane filtration methodology. Samples are also shown in the photo below. Humanitarian and development organisations are still waiting for a simple kit to be developed, which would identify the degree of faecal pollution with a simple, cheap and easy to learn methodology. (l-r) Colilert test tubes and fluorescent light; H 2 S strips; Dipslides OXFAM Technical Brief – Water quality analysis in emergency situations 3  OXFAM – TB3 (V1) Table - Comparison of microbiological test kit types Kit type Positive attributes Negative attributes Membrane filtration (Uses E.coli   / thermotolerant / faecal coliform as an indicator) Can be used to determine the actual number of faecal coliform per 100ml E.coli   is currently considered the ‘most suitable indicator of faecal pollution’. In most circumstances thermotolerant coliform are mostly comprised of E.coli and hence [thermotolerant coliform] is considered a less reliable but acceptable index of faecal pollution’ (WHO, 2004). Can test either faecal coliforms (at 44 o C) or total coliform (at 37 o C) Lengthy process to prepare MLSB media (pre-prepared MFC media in tubes is simpler, but needs to be stored at a specified temperature) Equipment needs to be sterilised - many risks to contaminate the equipment and sample It is not a suitable test for turbid water Training and practice are required to undertake the test and interpret the results Requires an incubator and hence a power source E.coli   / thermotolerant bacteria are less resistant to chlorine than pathogenic virus’ and protozoal cysts and oocysts and ‘there is some evidence that coliforms, possibly including E.coli, can proliferate in tropical and sub-tropical waters’   (Sobsey and Pfaender, no date). H 2 S strips (Uses the production of Hydrogen Sulphide by enteric bacteria as an indicator) Small and cheap Simple to undertake and does not need much training Sterilisation is not necessary P/A testing ‘is appropriate only in a system where the majority of tests for indicators [faecal coliform] provide negative results’ (WHO, 2004, p72) It is a presence / absence test and provides only positive or negative results  – even 1 faecal coliform will provide a positive result Reasonable quality water (< 10 faecal coliform) may be rejected inappropriately Can also provide a positive result from non-faecal bacteria and from sulphides already present in ground water - the problem is the risk of more positive results than more negative, but this can lead to water being rejected inappropriately ‘There remain too many uncertainties about the reliability, specificity and sensitivity of the test for detecting faecal contamination of drinking water and its sources’ (Sobsey and Pfaender, no date). They recommend however that it can be used when the alternative is no testing at all if it is used with caution and for educational and motivational purposes. Colilert tubes and fluorescent light (Uses Coliphages as an indicator, which are Bacteriophages or virus’ which use bacteria as hosts for replication, in this case E.coli  ) Can be incubated at 37 o C Simple to undertake and does not need much training Sterilisation is not necessary, although sterile water is required for determining quantities of E.coli >16 / 100ml Coliphages model the behaviour of enteric virus’ in water and in response to disinfection better than E.coli and hence are a better indicator of their presence (WHO, 2004). Uses the ‘Most Probable Number’ method – it is expensive as large numbers of consumable needed Requires an incubator and hence a power source (except if incubated against the body)  ‘White powder’ in tubes – may cause problems for international travellers  A 5 tube test will only indicate up to >16 per 100ml - to determine higher levels, dilution is required with sterile water The absence of Coliphages does not confirm the absence of enteric virus’ or protozoa (WHO, 2004). WHO (2004, p291) notes that due to some conflicting data, that at this present time they are ‘not suitable for operational or verification (including surveillance) monitoring’.   Dipslides (Uses E.coli   / thermotolerant / faecal coliform as an indicator) Easy to use with limited risks to contamination Simple to undertake and does not need much training Sterilisation is not necessary Can test either faecal coliforms (at 44 o C) or total coliform (at 37 o C) Expensive - high number of consumables Only one ml tested at a time, so if 1 faecal coliform is found this will indicate 100 / 100ml, and intermediary figures (between 0 to 100 / 100ml) are not possible to determine Requires an incubator and hence a power source Dipslides need to be stored in a refrigerator (0-2 o C) OXFAM Technical Brief – Water quality analysis in emergency situations 4
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