Field Evaluation of The UV Tube in Baja California Sur, Mexico
Through an iterative design process, informed by rigorous laboratory tests and detailed user feedback, the University of California at Berkeley (UCB) developed the UV Tube, a low-cost drinking water treatment system that uses ultraviolet (UV) light to inactivate viruses, protozoa, and
bacteria. When operated at five liters per minute, the UV Tube delivers a germicidal dose of 900 J/m2, which is more than twice the US National Sanitation Foundation requirement for certification of point-of-use UV disinfection systems (Brownell 2008). The UV Tube consumes 20 watts
of electricity and can be powered with either AC or DC voltage sources; including solar panels, wind energy, and local grids. The UV Tube was designed to be a versatile system that can be constructed from a variety of materials and adapted to serve an ample scale of water disinfection needs,
ranging from a household unit to a community-shared kiosk (Reygadas 2007, Cohn 2002).
In 2006, UCB and Fundacion Cantaro Azuli launched a joint project to create a UV Tube household system for rural communities in Baja California Sur, Mexico. The new system, called Mesita Azul
(Little Blue Table), gets its name from the color of the table that supports the UV disinfection chamber and provides the dedicated space for a 20 liter safe-storage container. In contrast to previous table-top UV Tube designs, the Mesita Azul seeks to allow users to operate the system in
a streamlined and effortlessly manner, that is consistent with regional water use habits. Furthermore, its blue color and stylish design were chosen as an attempt to bolster the demand and sustained use of the system. As an integral part of the project, Fundacion Cantaro Azul developed a five
phase program to accompany the installation of the Mesitas Azules: 1) a Community Needs Assessment visit to analyze drinking water quality, assess the viability of the program, and plan implementation logistics; 2) a Community Meeting to present the water quality results, promote safe drinking
water practices, and introduce the Mesita Azul as an effective water treatment alternative; 3) the Installation of the Mesita Azul in participating households; 4) a Short Term Follow-Up visit to address any technical problems and strengthen the safe drinking water promotion messages; and 5)
a final Evaluation visit one year after the installation phase to measure the program's results, fix any problems, and obtain user feedback to improve future projects.
As Fundacion Cantaro Azul rolled out the Mesita Azul program in 100 households in Baja California Sur, a research
team from UCB documented the implementation activities and measured their impact among participating households. The program was implemented throughout a period of one year, but only required five months of full-time equivalent work from a Fundacion Cantaro Azul technical officer. The Mesitas
Azules installed as part of this project had a construction cost of US70 per unit. The most expensive elements were the wooden table US18, the G15T8 UV lamp US12, the stainless steel chamber US8, and the 12V electronic ballast US8. After accounting for construction costs, the technical officer's
salary and the fieldwork expenses increased the program costs to US120 per participating family. Out of 105 families that attended the Community Meetings, 100 signed up to participate in the Mesita Azul program. Out of the 5 families that declined participation, 3 mentioned that they already
had access to other safe drinking water alternatives and 2 stated that they had been drinking untreated water for decades without a problem. The families that decided to sign up to the program made a commitment with Fundacion Cantaro Azul to pay a US36 cost recovery fee. Approximately 60%
of the families paid the fee on time, 20% paid it late, and the remaining 20% only made a partial payment. An evaluation visit carried out one year after the Mesitas Azules had been installed showed that 80% of the families were using the system in a continuous basis to meet their drinking
needs. Families quoted the system's ease-of-use, the perceived reduction of gastrointestinal problems, and the ability to control their drinking water quality as the main reasons for keep using the Mesita Azul. Participating families shared these opinions with relatives and friends, which
greatly contributed to the creation of a growing demand for the Mesitas Azules in the region. An evaluation visit carried out two years following the installation phase showed that the sustained use of the Mesitas Azules had dropped from 80% to 60% among participating families. Such drop was
mainly attributed to the malfunctioning of an electric switch and a pump used to extract the water from the 20 liter safe-storage container. This result has motivated Fundacion Cantaro Azul to change some of the components used in the Mesita Azul, as well as to strengthen the maintenance element
of the program by training a larger percentage of community members on how to repair the disinfection systems and creating a more reliable distribution chain for replacement parts.
In 2009, UCB and Fundacion Cantaro Azul will expand the Mesita Azul program to 400 additional households.
This new phase of the project will include a field study that will rigorously measure the effectiveness of the Mesitas Azules through water quality and health indicators. Furthermore, the study will seek to clearly identify the main factors that affect the adoption and sustained use of the
More about this publication?