Method for low cost water disinfection

#The present invention relates in general to water disinfection for human consumption. More particularly, the invention relates to low cost water filtration and disinfection to provide drinking water in situations where resources are limited.

#In developing countries, drinking water is often difficult to obtain. Currently, every hour, more than four hundred children in the developing world die from water-borne diseases. Ordinarily, women and children haul water from open wells, rivers or lakes for daily use. They also are primarily responsible for gathering firewood. It is simply not feasible for them to gather enough wood to boil their drinking water, and chemical disinfection is cumbersome and often impractical in communities without a water system and without a supply chain of chemicals for disinfection. Diseases like cholera often spread through contaminated water. Vaccines are expensive and practically difficult to administer on a widespread basis. Furthermore, mutant strains of old diseases have made current vaccines ineffective. Similar concerns occur whenever people are camping, or in any post-disaster situations. Thus, the need for a portable, easy to use, but effective water disinfector exists around the world.

#A wide variety of water disinfection systems are currently available. Typical systems, however, are unsuitable for disinfecting drinking water in developing countries. Many systems, for example, are designed to treat industrial water use or large-scale (e.g., municipal) water supply. These systems tend to be impractically expensive and complex for small scale use, e.g., for use by less than a dozen persons. Other systems are developed for household use in industrial countries or for developing country populations with a pressurized tap water supply. In this case, the systems tend to operate under pressure from the municipal water supply, and therefore are unsuitable for use in places without running water. Furthermore, such systems tend not to address some of the pathogens commonly found in developing countries, especially in sub-tropical and tropical climates.

#These and other aspects of the invention will be readily apparent from the description below and from the appended drawings, which are meant to illustrate and not to limit the invention, and wherein:

#FIG. 1A is a schematic view of a water disinfector, constructed in accordance with a first preferred embodiment of the present invention;

#FIG. 1B is an enlarged cross-section, showing a ceramic candle in the upper tank of FIG. 1A;

#As noted in the Background section above, conventional water disinfection systems are unsuitable for use in remote locations, particularly in developing countries where resources are scarce. Many systems are designed for filtering already potable water, such as municipal water in developed locales, for improved taste, reduced mineral content, or as an additional barrier to biological contamination in already treated water. Others, designed for disinfecting raw water in developing countries, particularly in sub-tropical and tropical climates, tend to be complex, difficult to service and expensive to operate due to difficult operating conditions and potentially high pathogen loads in the available water.

#U.S. Pat. No. 5,780,860 to Gadgil et al. provides one solution to the need for inexpensive water disinfection in remote locations. The illustrated device employs a simple mechanism to guide water through a shallow tray beneath an air-suspended ultraviolet (UV) lamp. Under the force of gravity, water flows at a controlled rate beneath the UV lamp. The water path is carefully configured to produce a constant flow rate and even exposure of the flowing water to the disinfecting energy of the UV lamp. Despite the lack of pump means and using only 40 W of power for the UV lamp, commercial embodiments of the '860 patent can safely disinfect water with throughput as high as 15 L/min.

#Though less complicated and less expensive than conventional water disinfection systems, the device of the '860 patent still represents significant initial and operational costs. The housing and tray define a carefully arranged water flow path to ensure even exposure of gravity-fed water to UV disinfecting light as water flows through the device, and so must be manufactured with particular care. Additionally, the disclosed lamp alone utilizes considerable power (e.g., about 40 W), for which the electrical power equivalent of an incandescent table lamp is required. Such systems require special provision where electric service is lacking or inconsistent. Units configured for use by a family or a small community (of several hundred persons) can currently cost several hundred dollars.