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Current IssueSeptember 03, 2015
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Ask The Expert: Drinking water filtration system for a community of 10K
Question: Q: We work in a town in southern Mexico called Mitla in the state of Oaxaca. There are about 10,000 people in that town and we've helped a local fellow get started in a drinking water delivery service. Currently, he gets the water in 5-gallon jugs trucked to Mitla from Oaxaca city over an hour away. This adds to the cost of the water, which is about US$1.25 per five gallons. But the larger concern is that they're unreliable.

Since we have a low volume spring on the property of a friend of ours that we've made a contract with, we thought it would be wisest to bring equipment from the USA to install down there so that we could provide water that was safe and good tasting to the community for a lower cost.

We're there serving as missionaries. I make digital recordings with native Indian language speakers of Bible messages, readings and songs. But we're also concerned for their physical needs. So please help us to find the most efficient and inexpensive way to provide safe and good tasting water for the majority of the community. Thank you!

John & Minky Black
Faith By Hearing
Wenatchee, Washington, EE.UU.

Editor's Note: We received a variety of answers from our Technical Review Committee and a couple others that were forwarded your request for information. Normally, we would compile them into a single answer for you, but felt the breadth of information provided warranted including them all individually. Thank you for your interest in Agua Latinoamérica.  

Answer: A: The spring you were talking about may be an acceptable drinking water source. You'll need, however, to have the water analyzed to determine what, if any, contaminants need to be removed. If we could see a complete water analysis, we would be in a position to recommend the most cost-effective treatment to ensure the potability of the water.

Peter S. Cartwright, P.E., CWS-VI
Cartwright Consulting Co.
Minneapolis, Minnesota, EE.UU.

A: It's difficult to answer your question at this distance without more information. Here are a few thoughts. It certainly should be possible to produce water from your spring for much less than $1.25 for 5 gallons. The first question is has the water been tested for bacterial and other contamination and is it safe? If not, that should be done. There are basic treatments that could be applied to assure microbiological safety if necessary (e.g., filtering and/or disinfection with chlorine). These can be done inexpensively or with purchased technology, or even homemade solutions (e.g., adding a few drops of a household bleach solution); it depends if there's a specific contaminant problem and how much knowledge you have on water treatment. Once you have safe water, then it's essential that you have a way to bottle it safely so the containers are clean and uncontaminated. I don't know what the situation is in your area (e.g., how many people, how much water you need per day, will it be bottled, will people bring their own containers for filling?). I suggest you contact someone from the local public health office agency, a water technology person from a nearby university, or a knowledgable water treatment person from the Inter-American Association of Sanitary and Environmental Engineers (AIDIS)—the Mexican chapter is known as the Federación Mexicana de Ing. Sanitaria y Ciencias Ambientales, A.C. (FEMISCA). I have also sent your email to Cindy Yablonski at the International Bottled Water Association, and Joe Harrison at the Water Quality Association. They might be helpful, but I suspect they'll be more focused on commercial practices and equipment that may be more elaborate and expensive than you need.

Joseph A. Cotruvo
Cotruvo & Associates
Washington, D.C., EE.UU.

A: I received your inquiry about a safe and reliable water supply for the town of Mitla in the state of Oaxaca, Mexico. There are, of course, numerous Water Quality Association member companies that can provide water treatment assistance and equipment to make this supply safe. But perhaps the best first step I could suggest is to use the WQA website (www.wqa.org) "Member Finder" service to locate a dealer of water treatment services in your area that you find comfortable for you to work with. The Member Finder button is located at the bottom of the home page, but you'll have to scroll down a bit. On the Member Finder webpage, look for "International Members" and, from the drop-down box, you can select Mexico, which will provide you with the entire list of WQA members there. These experts can then best diagnose the most appropriate water treatment scheme to apply in your particular situation, and also help find manufacturing sources of needed equipment products.

Another organization you may want to contact is Water For People. Based in Denver, Colorado, EE.UU., it can be reached at (303) 734-3495 or www.waterforpeople.org. WFP is a charitable organization that assists those in developing countries throughout the world to organize and implement drinking water sanitation projects that improve the health and welfare of the local populations. It has operations currently in Guatemala, Honduras and Bolivia in Latin America.

Joseph F. Harrison, P.E., CWS-VI
Technical Director
Water Quality Association
Lisle, Illinois, EE.UU.

A: Ms. Linda Wurts Martinez is based in Mexico City, and she knows who's who amongst the manufacturers of equipment there. Fortunately, she's an educator and journalist (contributing editor to Agua Latinoamérica), not a salesperson per se, so she can give unbiased advice. And her family has been in the bottling business for a number of years. Unfortunately, she'll be moving to Buenos Aires in August so it would be good to contact her soon.

Amongst Water Quality Association members in Mexico: Instapura (based in Cuernavaca) makes UV disinfection systems; Junghanns (based in Puebla) makes treatment systems but also used to be one of the largest water bottlers in Mexico before selling the operation last year. Industrias Mass (based in Tlalnepantla, DF, but with several offices throughout Mexico) makes UV disinfection systems—as well as provides a variety of other equipment, including bottling systems. [In addition, Water Tec International is based in Tucson, but has offices also in Guadalajara and Mexico City—it makes a variety of water treatment equipment and is a major distributor there; Ozono Polaris is based in Puebla and provides ozone systems, particularly for bottled water applications; Water Technologies de Mexico is based in Monterrey and makes and distributes a variety of water treatment equipment, and Inova S.A. de C.V. in Monterrey is a diversified water treatment solutions provider.

Since the town is small and short on resources, you might want to consider a vending system where people walk up and fill their own bottles. This is a good option when prices need to be low and the supplier doesn't want to be concerned with what people do (i.e., how sanitary they are) with their bottles. [A poster of proper care and sanitation procedures for containers would be helpful to post at the filling station for users.] The Phillipines has seen this type of system become a "craze" over the past few years and I think conditions in both places are similar (recent volcanic soil high in silica making groundwater treatment problematic).

Regardless of what they do, getting a detailed water analysis of the spring is critical. As happens many times in Mexico, the water quality may change during the transition from dry to rainy season and equipment designed using an analysis during one season may become totally ineffective during the other. I hope Mitla is close to a lab that can measure coliform bacteria contamination, as remote areas sometimes have a hard time getting accurate results when transport of the sample to the lab is slow. A good lab will instruct the residents how to take samples so the best results come back. This is a problem in Mexico, since labs frequently don't advise how to keep samples uncontaminated by air or by human hands.

I hope this helps.

Andrew Warnes, Director
World Assembly Division
Water Quality Association
Lisle, Illinois, EE.UU.

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