Low-Cost Bacterial Water Tests

Simple, Accessible, Affordable Tests to Assess Microbial Water Quality and Safety in the Developing and Developed World

“My hope is that these tests would be transformational. Just like cell phones transformed access to telecommunications for people in developing countries, these could transform access to reliable information about drinking water quality”

—Mark Sobsey, PhD, Environmental Health Microbiologist

Mark Sobsey from Geologie on Vimeo.


Worldwide, an estimated 1.6 million people die every year from diarrheal diseases attributable to unsafe drinking water, lack of sanitation, and poor hygiene; 90% of these are children under 5. In many developing countries, is common practice to dump untreated sewage into the same lakes, rivers, and streams that people use for drinking, washing, and bathing. Not surprisingly, fecal contamination is responsible for some 80 percent of all infectious diseases in the world. While long-term solutions to these problems will eventually require interventions to improve water quality and enhance sanitation infrastructure, much could be gained now through more frequent and widespread water testing.

The Problem

In developing countries and other resource limited settings (such as after natural disasters), drinking and other water is almost never tested to estimate its risks of causing infectious diarrhea, enteric fever, cholera, and other life-threatening waterborne diseases. This is because there do not exist any simple, accessible, affordable, laboratory-independent methods to detect and quantify fecal bacteria in water used for drinking or other beneficial purposes. The portable tests that are available either do not give quantitative results, are not designed for populations to self-test, and/or are priced beyond what people can afford. (Even a test that costs $10, which may seem economically feasible for someone in the developed world, is cost-prohibitive for someone living below the poverty line.) As a result, the majority of people on the planet are drinking water about which they know nothing in terms of its fecal contamination, and millions continue to get sick and die unnecessarily from unsafe water.

The Innovation

While microbiologists have long thought about the idea of working on a simple, low-cost, accessible test for detecting fecal contamination in water, only recently has attention focused on developing such a test for remote communities and resource-poor settings.

“The development and deployment of an every-person’s test—simple, self-contained, portable, stable, and devised to not need electricity, refrigeration, or freezing—to determine water safety could be key for catalyzing global efforts to curb preventable illness and death due to waterborne fecal pathogens”

—Mark Sobsey, PhD, Environmental Health Microbiologist

Dr. Sobsey has developed three versions of a simple, low-cost test for quantifying fecal contamination in water. Each variation involves a plastic bag into which is placed a water sample and a bacteriological medium that does not need to be boiled or autoclaved, and that can be incubated at temperatures 25–45 degrees Celsius—a range encompassing the environments of nearly all tropical and subtropical countries. The bag incubates overnight (on a shelf in someone’s home, for example) to give time for the bacteria to grow. The sample is then examined for evidence of bacterial growth. In one version, the plastic bag is divided into compartments that mimic test tubes, and bacterial density is estimated by the number of chambers that show characteristic color change and cloudiness. In the other two test versions, distinct bacteria colonies appear in a gelled medium or on an absorbent pad and can be counted directly. For each test, the estimated bacterial density can be compared to WHO Guidelines for safe drinking water. If bacteria are present at unsafe levels, users can determine whether to treat the contaminated water or find an alternative water source.

The Vision

The strategic and rapid deployment of water testing could be a powerful tool for identifying safe water sources, directing water treatment efforts to high-risk communities, as well as for protecting populations from unsafe sources during natural disasters and emergencies. Dr. Sobsey envisions a future where water-related illness is substantially reduced by the widespread availability of a simple, low-cost water test.

“Household-level diagnostic testing is already done for tuberculosis, HIV/AIDS, malaria, intestinal parasites, diabetes, etc. There’s no reason why a simple, low-cost water test couldn’t be added for something as fundamental as safe water. In fact, new WHO guidelines for drinking water quality really encourage that water be tested on a regular basis for water management and for verifying quality.”

—Mark Sobsey, PhD, Environmental Health Microbiologist


The next steps in the development of these tests are to finalize the design of the plastic bags with input from industrial designers and materials scientists, finalize the formulation of the bacteriological medium, and find companies that can produce these at very low cost. The current cost for the prototype, using materials purchased at U.S. retail prices, is between $1.25 and $2.25, depending which fecal bacteria are being detected. Dr. Sobsey believes the final cost will be well under $1, and possibly even as low as 10 cents.

“The current situation of no suitable tests for fecal bacteria in water is both intolerable and unnecessary. The small price to pay for knowing the safety of drinking water could reap enormous benefits in terms of improved health, increased productivity, and better quality of life.”

—Mark Sobsey, PhD, Environmental Health Microbiologist

Source: launch.org

Many of us take it for granted that our tap water is safe to drink.  Water quality testing is something that many people are unaware of and/or don’t know how to go about.  Even in First World Countries, laboratory testing for microbial water contamination is not necessarily inexpensive or accessible. A widely available, inexpensive testing kit as described above, would be welcomed by people across all classes.  In South Africa, some local municipalities are supplying towns and cities with water of questionable quality (there have been cases of E. coli contamination in municipal drinking water).  Some people believe that borehole water is guaranteed ‘safe’ to drink but this is a fallacy.  Groundwater contamination is a growing problem in South Africa and worldwide. All drinking water should be tested regularly and preferably filtered.  A cost effective solution to contaminated water is the Bio Sand water filter system which can be made from freely available, inexpensive materials.  Knowing the origin and quality of one’s drinking water is a good case for rainwater harvesting (rainwater should still be filtered if used for drinking). Water tanks, either for rainwater storage or for municipal/borehole water storage, are a good way to gain more control of your household water quality.  Testing the water before flows to your house is advantageous and appropriate filtration measures can be taken.  Water Rhapsody’s water systems included rainwater harvesting systems, grey water reuse systems, water saving devices and water tanks (we are official JoJo water tank dealers).  We supply and install all our systems that are covered by a guarantee and lifetime after sales service.  Contact us for a free quote!

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