Fun at INESAD Serious fun at work
A combination of insatiable curiosity and healthy skepticism led a group of INESAD researchers to conduct a very unusual experiment for economists: Following a carefully devised protocol developed by Susana, we took water samples from our kitchen taps on Monday the 14th of September in several different neighborhoods in La Paz and El Alto, and arranged an afternoon in UMSA’s Environmental Quality Lab to test the quality of the water samples.
For comparison, we also tested a bottle of Agua Vital and a bottle of CocaCola (both from the CocaCola Company).
We were welcomed and most kindly and patiently assisted by the Director, Jaime Chincheros and two other professionals from the lab: Nohelia Rendon, and Marcelo Colpari.
The first two basic tests we conducted measured the level of acidity and conductivity of the liquids. All water samples were slightly alkaline, ranging between 7.18 and 7.78 in pH value (on a scale from 0 to 14, where 7 marks neutral). All tap and bottled waters sampled were thus in the most healthy range (6.5-8), whereas CocaCola is outrageously acidic, with a pH value of only 2.54 (see Table below).
Conductivity says something about the quantity of dissolved salts and minerals in the water. Ultrapure (de-ionized) water has a conductivity of about 0.055 µS/cm (microSiemens per centimeter), while seawater has about 50,000 µS/cm. Neither extreme is good for the human body. Drinking seawater will dehydrate and eventually kill you, while ultrapure water will dissolve and pull out minerals and salts from your cells. Typical drinking water in the United States is in the 50-500 µS/cm range, but in Bolivia the upper limit has been set at 1500 µS/cm, thus accepting even CocaCola as drinkable on this measure.
Another very important water quality check is for the presence of heavy metals. We were advised not to do this test (too expensive), but the Lab assured us that they have done it hundreds of times, and the levels of heavy metals in potable water in La Paz were always found to be minimal, even for Achachicala, which is supplied with water contaminated by mining activities.
The next test we did was for bacteria, which is what usually worries people and makes them boil and/or filter their tap water before drinking it. This test takes longer to perform, as the bacteria has to multiply in their favorite growth medium for about 36 hours at a temperature of 36.5°C. We prepared 5 samples from El Alto and 5 samples from Miraflores, as these neighborhoods supposedly receive the lowest quality water.
We checked specifically for E-coli, which are the most dangerous, but also for total coliforms. We came back to the lab Wednesday morning to check on the cultures, but found them to be completely clear and bacteria-free. For comparison, Nohelia showed us a culture with un-treated water from a well, and that had plenty of bacteria (see photo below).
Having established that tap water in La Paz is perfectly safe, we wanted to make a final taste test. So we gathered the staff of INESAD for a blind water tasting experiment to see if they could distinguish between tap water and bottled water and to see which water samples had the best taste. A total of 15 water samples from bottles and taps all over La Paz were evaluated for appearance, smell and taste.
While tap water across the city is safe to drink, the taste of water varies a lot across the city. The two bottled water samples got both the highest ranking (Vital) and the lowest (Wiscachani) with all tap water samples being in between. The most appreciated water samples were Agua Vital bottled water, tap water from Alto Obrajes, and tap water from Achumani. The least liked samples in the blind taste test were Wiscachani bottled water, and tap water from Bella Vista and Mallasilla.
So, our conclusion of last week’s water experiments is that, contrary to popular perception, tap water in La Paz is of high quality and perfectly safe to drink. It is slightly alkaline, which is good, has a healthy level of minerals and salts, but no heavy metals, and no dangerous bacteria.
We ought to pay a bit more to our public water company, Epsas, to make sure it can keep supplying us with abundant, healthy water in the future. And we ought to cut down on the expensive and highly contaminating habit of buying bottled water.
More details coming up on the INESAD blog “Desarrollo sobre la Mesa” later this week.
