Solar Disinfection of Drinking Water and Oral Rehydration Solutions

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Foreword
Oral Rehydration Therapy: The Revolution for Children
Oral Rehydration Therapy: The Four Simple Technologies
Global Rehydration Therapy: Global Diarrhoeal Diseases Control Programmes
Oral Rehydration Therapy: Causes, Transmission, and Control of Childhood Diarrhoea
Oral Rehydration Solutions: The Practical Issues
Oral Rehydration Solutions: Domestic Formulations
Oral Rehydration Solutions: Disinfection by Boiling
Solar Energy: Fundamental Considerations
Solar Energy: From Sun to Earth
Solar Energy: World Distribution
Solar Energy: A Competitor
Solar Energy: Some Practical Hints
Solar Disinfection Studies: Drinking Water
Solar Disinfection Studies: Oral Rehydration Solutions
Appendix: Source of Information on Diarrhoeal Diseases

Oral Rehydration Solutions

Domestic Formulations

Sugar and Salt Solution

In areas with endemic diarrhoeal diseases, it is essential to produce and distribute to the communities at risk sufficient quantities of prepackaged ORS for early home use. Community-based ORT programmes are likely to meet with failure if this is not assured, either through local production, or from supplies distributed by UNICEF. In most of the developing countries where childhood diarrhoea is rampant, and supplies of ORS packets are insufficient for use in every home because of limited resource, the only feasible alternative would be to promote the preparation of sugar and salt solution at the household level. These can serve a useful purpose under such conditions as they have been shown to be quite effective in controlling diarrhoeal dehydration, and are easy to prepare at reasonable costs from locally available materials.

Based on the standard ORS formulation developed by WHO, homemade preparations should actually consist of 40 grammes of sugar and 3.5 grammes of common salt dissolved in one litre of clean, safe water.

Improvised Measuring Aids

Measurement of salt and sugar by weight, and of water by volume, using scales and volumetric measures was recognized to be an impractical requirement for household preparation of ORS solutions in village settings throughout the developing world. Where ORS packets are made available to families, the problem arises when the contents are mixed with the correct amount of water specified. These difficulties are not usually encountered in most ORT centres as they are expected to be furnished with the necessary measuring devices. Thus the need for improvised measuring aids led to field testing of a variety of techniques and devices for accuracy and acceptability.

The methods generally used for measuring salt and sugar are essentially based on hand or finger measures (finger pinch) and spoons (household or special plastic spoons). The instructions for the preparation of sugar-salt solutions vary accordingly. The pinch and scoop method is based on estimating the amount of salt with a three-finger pinch, and of sugar by a four-finger scoop, the measured amounts being added to a cup of water. With household spoons, a basic recipe uses eight level 5 ml teaspoonfuls of sugar and one level 5 ml teaspoonful of sugar and a three-finger pinch of salt for about 250 ml of clean water. The addition of two teaspoonfuls of sugar and a pinch of salt to a glass or mug of boiled and cooled water constitutes yet another variety of formulas. In a field trial, it was required to dissolve one level teaspoon of salt and four heaped teaspoons of sugar in a litre of water.

Field assessments of the methods described have indicated that marked variations exist in the quantities measured by mothers in different parts of the world. A refinement pioneered in Indonesia with encouraging results depends on the use of a special double-ended spoon made of plastic. One end is for measuring one level scoop of sugar, and the other is for measuring one level scoop of salt to be dissolved in one cup (200 ml) or glass (250 ml) of water. Instructions are printed on the spoons in five languages. Because too much salt may be hazardous, mothers are advised to discard any preparations that taste more salty than tears. These spoons can be obtained from TALC (Teaching Aids at Low Cost, 30 Guilford Street, London, WC1N 1EH, U.K.).

Different methods for measuring the required volume of water have been tried with varying degrees of success, including locally used cups, mugs, bowls, glasses, bottles, tin cans, coconut shells, and even the dried shells of bottle gourd (Lagenaria siceraria). The difficulty of finding a suitable measuring aid available in the majority of homes was resolved in the Philippines by adopting local beer bottles of uniform size. Subsequently, the glass container for a popular coffee brand was found to be more practical. In Gambia, a novel technique developed by the local health authorities based on the use of a local soft drink (Julpearl) bottle and cap as aids for correct measurements. For the preparation of one litre of home-made solution, eight caps of sugar and one cap of salt are to be added to three Julpearl bottles of water. A similar technique was recently adopted in Zimbabwe using a local soft drink (Mazoe) bottle and cap.

Plastic bags marked at the desired volume deserve consideration by local manufacturers as they are not expected to add substantially to ORT programme costs. These can also serve as kangaroo packets to hold the sugar and small packet of salt. Such a double function could significantly reduce the overall costs.

Issues to be Resolved

Each of the previously described techniques for the preparation of sugar-salt solutions at home have advantages and disadvantages. They all serve a useful purpose pending the development of more accurate measuring techniques. In any case, much of the success or failure of any of these techniques depends on proper training of health workers, meticulous instructions given to mothers, and monitoring of the home-made solutions. Mistakes in preparing the solutions may offset some of their beneficial effects.

Some of the major issues arising from the preparation and use of home-made solutions relate to the quality and availability of the ingredients, accuracy in preparing them, and their effectiveness and safety.

In some areas sugar and salt are scarce commodities. Sugar may be adulterated with water to increase its selling weight. Crude salt, with its deliquescent property and impurities, is the kind most likely to be used by virtue of its availability and low cost. It is such factors that could augment the errors committed in measuring the desired quantities of ingredients, and add to the difficulties in promoting and implementing home-based programmes.

The varied composition of the home-made solutions, together with the lack of bicarbonate and potassium, raise the question as to their effectiveness and safety. Field experience has repeatedly validated the effectiveness of these solutions for rehydration purposes even in the absence of bicarbonate. Development of acidosis from lack of bicarbonate does not constitute a significant problem. Because potassium losses in diarrhoea are relatively high, it needs to be replaced during rehydration of undernourished children who have suffered repeated diarrhoeal episodes. There are many locally available sources of potassium that can be added to the sugar-salt solutions. These include coconut water, fresh lemon and orange juices, raw tomato, banana, plantain, and papaya. A home preparation of sugar and salt solution with lemon juice called Super Limonada has been successfully tried in Nicaragua.

The addition of slightly more sugar than necessary, which can happen in some cases, would not lead to any serious problem. However, the final concentration of salt is fairly critical. Very low concentrations may render the sugar-salt solutions ineffective. The unintentional addition of too much salt is a much more likely possibility, in which case hypernatraemia could occur. This can be avoided by instructing mothers to measure the salt as carefully as possible, and to check the prepared solutions by tasting their saltiness. Any solution that tastes saltier than tears should be discarded�a somewhat arbitrary decision.

Other areas of concern relate to the inaccuracy in volumetric measurements, quantities to be prepared, storage of solutions, and quality of the water used.

Variations in the composition of oral rehydration solutions, whether prepared from UNICEF packets or from household formulations, are partly dependent on the degree of purity and accuracy in measurement of the ingredients. Volumetric measurement of the fluid is another contributing factor. With the measuring aids available to rural communities, a wide margin of error in the concentration of the ingredients is expected. The issue arising from this is whether the variations in concentration fall within the tolerance limit for the more critical ingredients, like sodium and potassium. It is unfortunate that this issue has not yet been resolved.

It is recommended by WHO that solutions be prepared fresh daily, and that mothers should be instructed to discard any unused portions after 24 hours to avoid the risk of growth and multiplication of microorganisms. This also applies to concentrated stock solutions prepared at dispensaries for distribution to families. This requirement is necessary even when solutions are prepared with boiled water. Solutions containing sugar and water could support the growth, at least for some time, of such microorganisms as bacteria, viruses, molds and yeasts. These contaminants might originate from the ingredients, water, containers and utensils, or through handling. The importance of some of the microbial contaminants relates to the spoilage and storage limitation of the prepared solutions. Contamination with pathogenic organisms, whether from the water or other sources, arouses concern regarding possible detrimental health effects on children undergoing oral rehydration therapy. In any case, mothers should, be instructed to prepare solutions with clean water, vessels, and utensils, and to keep them in covered utensils until needed for use.