Florence Casssassuce explains to me that the main difference between tap water in the United States and tap water in Mexico is that the city only has enough plumbing pressure to provide water for a couple hours a day to one particular neighborhood at a time. People take advantage of this pumping to store water in a personal, 200-gallon rooftop tank. The issue with drinking tap water in Mexico is storage contamination. Even though the tap water may be relatively clean and chlorinated, storage tanks may be full of algae, and you can’t reach inside to clean them.
Flor is the director of Instituto EOZ de Technologias Rurale, a company she recently started after developing a point-of-use ultra violet light disinfection system for drinking water. During the past five years, she’s worked on this technology and on distributing it to rural communities of Baja.
There is one more significant problem with Baja water, and that is salt. “We have the same problem as Australia or the same as most arid land with volcanic rock,” Flor explains. “There is very high salinity – won’t pass US EPA drinking standards – from aquifer intrusion.” There are health problems associated with drinking water containing too much salt. Many people drinking salty water in Baja, especially in the rural communities that don’t have reverse osmosis purificadoras, develop kidney stones over several years that require surgery.
For this reason, Flor chooses to buy 5-gallon jugs of water from a family-run purificadora in La Paz for her drinking water at home and in the office. Her tap water, from a 200-gallon rooftop tank, she uses for washing dishes, showering, and other household chores. She places a bucket under her kitchen sink to capture used water and recycles this water for her plants.
Adrian Schalkwijk, an industrial designer from Mexico City who is now working in La Paz to develop Flor’s next UV system prototype, lives on a ranch outside La Paz city limits. In his house, Adrian explains, water is delivered by truck to his cistern, which he then pumps to a rooftop tank and flows through his tap. He doesn’t drink water directly from his tap – he filters it through a Primag filter, a home system containing sand, clay, and colloidal silver. At his office, water is from the 5-gallon blue jugs.
David Vasquez, Adrian’s former student and current product-design colleague, says he has no water filter at home, so he drinks only from the 5-gallon jugs.
Great post!
ReplyDeleteI'm wondering a few things:
what are the consequences of consuming water that contains algae? If the problem with the water is just algae and not bacteria than would a simple(r) filtration system be sufficient (and perhaps cheaper and easier to use) or is the UV really necessary?
Here's a big, lengthy response. :)
ReplyDeleteAlgae is a huge term. It’s a name given to a wide variety of organisms spanning several phyla. Most are photosynthetic, but some are chemoheterotrophs. Algae is identified mainly by its rRNA, but many are grouped into the obvious classifications of green, red, and brown. Brown algae (kelp), red algae (plate agar as well as thickening agent in ice cream and evaporated milk) and green algae (most plant-like). Then there are the diatoms, dinoflagellates (planktons), and water molds. Most kinds of algae live in salt water.
Diatoms have been known to cause neurological disease from domoic acid. This acid can become concentrated in, say, mussels, which humans then eat. The fatality rate has been reported below 4%, but the symptoms can be severe. Symptoms include diarrhea and memory loss. Some dinoflagellates also produce neurotoxins. Some cause fish to stop breathing. The dinoflagellate Alexandrium releases saxitoxins that cause paralytic shellfish poisoning, which affects humans; this is the phyla behind red tide. The dinoflagellate Pfiesteria is toxic to humans and may be inhaled. Generally, algal blooms are a problem when toxic forms proliferate and bioaccumulate in animals that are eaten by humans and fish. Again, this is mostly true for salt water environments.
Water molds are the decomposers generally found in freshwater. These are the bane of the border control agents, as they are frequently carried on agricultural products and introduced to new lands. Water molds can be devastating to agricultural crops. (Everything from the great potato blight of the mid-1800s to California’s sudden oak death was caused by water molds.) Indirectly, I suppose, water molds that cause massive famines kill humans, but I don't know the consequences of directly ingesting small amounts of water mold.
The real problem with algal growth in a water tank, however, is the possibility of biofilm formation. All manner of microorganisms can attach to biofilms, and once these formations develop, they are usually incredibly difficult to kill.
Two other things to consider: 1) rooftop tap water is variably salty 2) rooftop tanks may be filled by water delivered from a truck
Boiling water (close to boiling) is an effective way to kill water-borne pathogens, but boiling water increases salt concentration.
A sand biofilm filter (this is a positive use of predatory and glue-like biofilms) is an effective way to remove most pathogens from drinking water. In some areas, clay pot filtration is also used.
Some of this just comes down to preference.
UV disinfection systems can cost only slightly more than biofilm sand filters and clay filtration, and usually these are subsidized by agencies or non-profit organizations for people living in rural areas with low incomes. True, $30 is very expensive in some areas and even a subsidized $12 cost may be unreachable for some families. The Baja organization Niparaja has given many of these UV bucket systems away for free. UV systems (unless they are solar powered--more expensive--or battery operated--need changing) run on electricity. Flor's UV bucket can be run off intermittent grid electricity or can be hooked up to a car or truck battery.