UV Bucket:::Niparajá

Sociedad de Historia Natural Niparajá, A.C.

Project

Project Definition

This project was based on the 2000 national census from the Mexican National Geographic Institute (INEGI), which reported 42,607 persons in 2,690 rural communities of B.C.S. The new data of the 2005 census published in 2007 report 56,944 persons in 2,436 rural communities of less than 1000 inhabitants. In 1995, several hundred people died of cholera in an epidemic in the state. During our 2005 study, interviews of rural villagers confirmed that diarrhea problems are continual and widespread in the majority of the rural communities. The rural schoolteachers also reported children’s classroom attendance suffered due to episodes of illness.

Based on these results, we estimate that between 8,000 and 12,000 UV Buckets will be needed to cover the entire rural population of B.C.S.

Origen of the contamination

Fecal contamination of the water is one of the main cause of gastro-intestinal diseases (diarrea, colera, tifoidea, hepatitis, amibas en el intestino) which affect the rural population of BCS. Our study identified several pathways for the contaminants to reach the water. Most of the wells are located directly in the arroyo (seasonally dry river).

Examples of wells used for drinking water in the rural communities of BCS, 2005

Grazing animal excrement present in the arroyo bed causes the contamination of the well water. In addition, many latrines and animal parks are located less than 20 meters away from the well, allowing bacteria in human and animal excrements to percolate to the well water.

site map

Finally, contamination occurs within the household since, firstly, receptacles for storing water are typically uncovered and, secondly, families dipping a cup to draw water causes bacteria from their hands to contaminate the water. Our study identified several cases where the well water was not contaminated but the water receptacle in the house was.

Typical water containers to store well water
in rural households of BCS, 2005

A recent effort to improve the situation was initiated by the government, after the 1995 cholera epidemic. In a few rural communities, a drip chlorination system was installed at the community well using solar panels to power the system. We identified a number of drawbacks of this system: water can get re-contaminated during its transport (leaking pipe laying in the soil) or in the household (storage in uncovered recipients for several days). Moreover some families declared not using the chlorinated water for drinking, because of its bad taste, described as “unhealthy.” These families instead obtain drinking water from other open-air wells (as far as 15 km away).

This unsuccessful project taught us important lessons:

· Though scientifically effective, a scheme might be culturally unviable.

· The introduction of technology must be designed as a participatory process.

· Education provided to the beneficiaries about the technology and its related issues is essential for its adoption.

· The local population must have the chance to appraise the technology before its implementation.

· A project is successful when the technology is adopted by the user population, rather than upon its installation.

TOP

Idea and Innovation

The proposed approach was conceived on the following basis:

1.There is no piped water in rural communities of BCS but every household has a 50W government-supplied solar panel providing the 12V current for the UV lamp (18W).

2.The device offers “point-of-use disinfection,” i.e. water is disinfected when and where the user serves him or herself. The device includes a water dispenser to avoid the change of containers or the use of unclean utensils to draw the water, which are factors of potential recontamination.

3. The simple design and functioning of the UV Bucket is easily understood by the users .

The UV Bucket is considered preferable to the following disinfection strategies:

Disinfection	Description
Chlorine	Positive: Can be used to disinfect not only water but also tools or surfaces, especially in the case of hospitals. If added correctly and with sufficient contact time, efficient at killing bacteria and viruses. New devices producing chlorine from table salt are convenient for developing countries and are low-cost. Negative: Short operational life requires frequent delivery, difficult to arrange reliably by governments. Rejection because of chlorine taste. Efficiency dependant on dose.
Sand filtration	Positive: Can be made by local population without the need for external materials. Inexpensive if built by local workforce. Large systems can be designed for an entire community. Maintenance requires only local labor, no parts. Efficient at removing turbidity from the water. Negative: Bulky system difficult to convey to rural communities. Clogging of sand pores. Requires frequent backwashing. Recontamination of water due to bacteria detachment. 90% bacteria removal, no virus removal. Typical flow rate for slow sand filtration in the order of 100L/hr/m2 of sand. For a typical household system, the flow rate would then be around 20L in 1 hour.
Ceramic filtration	Positive: Can be made locally by trained workers. Can create jobs for local entrepreneurs who already have kilns. Removes turbidity from the water, although at a very slow flow rate. Is inexpensive when kiln and abundant firewood are present. Does not require external materials. Negative: Very slow flow rate (2 liters per hour). Difficult fabrication in areas with scarce wood. High risk of breakage. Rapid clogging due to small pore size. 99.99% bacteria removal, less than 90% virus removal.

Based on this knowledge, the UV Bucket was developed with the following key advantages:

* High efficiency: above 99.9999% of bacteria removal, and above 99.9% virus removal

* For its efficiency, lowest cost among existing disinfection devices

* Rapid disinfection: 3 liters per minute

* Water container and dispenser integrated in the design

* Light and easy to transport

* Easily assembled locally

* Easily maintained with replacement parts available in rural stores

Disinfection

Description