drinking water

As of 2006, waterborne diseases are estimated to cause 1.8 million deaths each year while about 1.1 billion people lack proper drinking water.^[32]

Water generally needs treatment before use, depending on the source and the intended use (with high standards required for drinking water). The quality of water from household connections and community water points in low-income countries is not reliably safe for direct human consumption. Water extracted directly from surface waters and open hand-dug shallow wells nearly always requires treatment.

Appropriate technology options in water treatment include both community-scale and household-scale point-of-use (POU) designs.

The most reliable way to kill microbial pathogenic agents is to heat water to a rolling boil.^[33] Other techniques, such as varying forms of filtration, chemical disinfection, and exposure to ultraviolet radiation (including solar UV) have been demonstrated in an array of randomized control trials to significantly reduce levels of waterborne disease among users in low-income countries.

Over the past decade, an increasing number of field-based studies have been undertaken to determine the success of POU measures in reducing waterborne disease. The ability of POU options to reduce disease is a function of both their ability to remove microbial pathogens if properly applied and such social factors as ease of use and cultural appropriateness. Technologies may generate more (or less) health benefit than their lab-based microbial removal performance would suggest.

The current priority of the proponents of POU treatment is to reach large numbers of low-income households on a sustainable basis. Few POU measures have reached significant scale thus far, but efforts to promote and commercially distribute these products to the world's poor have only been under way for a few years.

On the other hand, small-scale water treatment is reaching increasing fractions of the population in low-income countries, particularly in South and Southeast Asia, in the form of water treatment kiosks (also known as water refill stations or packaged water producers). While quality control and quality assurance in such locations may be variable, sophisticated technology (such as multi-stage particle filtration, UV irradiation, ozonation, and membrane filtration) is applied with increasing frequency. Such microenterprises are able to vend water at extremely low prices, with increasing government regulation. Initial assessments of vended water quality are encouraging.

Whether applied at the household or community level, some examples of specific treatment processes include:

• Porous ceramic filtration, using either clay or diatomaceous earth, and oriented as either cylinder, pot, or disk, with gravity-fed or siphon-driven delivery systems. Silver is frequently added to provide antimicrobial enhancement
• Intermittently operated slow-sand filtration, also known as biosand filtration
• Chlorine disinfection, employing calcium hypochlorite powder, sodium hypochlorite solution, or sodium dichloroisocyanurate (NaDCC) tablets
• Chemical flocculation, using either commercially produced iron or aluminum salts or the crushed seeds of certain plants, such as Moringa oleifera. Recent work has shown even table salt (NaCl) is effective at removing high-activity clays for solar water disinfection.^[34]
• Irradiation with ultraviolet light, whether using electric-powered lamps or direct solar exposure such as with the SODIS method
• Mixed flocculation/disinfection using commercially produced powdered mixtures
• membrane filtration, employing ultrafiltration or reverse osmosis filter elements preceded by pretreatment

Some appropriate technology water supply measures include:

• Deep wells with submersible pumps in areas where the groundwater (aquifers) are located at depths >10 m.
• Shallow wells with lined walls and covers.
• rainwater harvesting systems with an appropriate method of storage, especially in areas with significant dry seasons.
• Fog collection, which is suitable for areas which experience fog even when there is little rain.
• Air well, a structure or device designed to promote the condensation of atmospheric moisture.
• Handpumps and treadle pumps are generally only an option in areas is located at a relatively shallow depth (e.g. 10 m). The Flexi-Pipe Pump is a notable exception to this (up to 25 meter). For deeper aquifers (<10 m), submersible pumps placed inside a well are used. Treadle pumps for household irrigation are now being distributed on a widespread basis in developing countries. The principle of Village Level Operation and Maintenance is important with handpumps, but may be difficult in application.
• Condensation bags and condensation pits can be an appropriate technology to get water, yet yields are low and are (for the amount of water obtained), labour-intensive. Still, it may be a good (very cheap) solution for certain desperate communities.
• The hippo water roller and Q-drum allow more water to be carried, with less effort and could thus be a good alternative for ethnic communities who do not wish to give up water gathering from remote locations, assuming low topographic relief.
• The roundabout playpump, developed and used in southern Africa, harnesses the energy of children at play to pump water.

As of 2006, waterborne diseases are estimated to cause 1.8 million deaths each year, marking the importance of proper sanitation systems. It is clear that the developing world is heavily lacking in proper public sanitation and that solutions as sewerages (or alternatively small-scale treatment systems) need to be provided.^[35]