Could a Piece of Wood Provide Safe Drinking Water?


CAMBRIDGE, Massachusetts–Poor nutrition has a hand in more than half of all child deaths. No infectious disease has affected children more than malnutrition, with the exception of the Black Death. Intimately linked to the environment, nutrition reform requires political and scientific action.

Many assume inadequate intake drives malnutrition to epidemic proportions. Yet according the World Bank, poor sanitation stands as the most severe threat to child nutrition. Unsafe drinking water leads to diarrheal diseases, leading to a continuous loss of nutrients. Mothers, for instance, use water-based formulas instead of exclusively breast-feeding. These infants face the constant threat of disease as a result.

At the Massachusetts Institute of Technology, a scientist believes he engineered a solution to this contamination. Removing bacteria from drinking water could protect children from this threat of disease. Technologies exist, but cost too much for widespread use.

Rohit Karnik of MIT proposes a simple solution, using membranes to filter bacteria from the water. Typically, these membranes cost too must to reproduce.

In recent years, however, he researched a more affordable method. Testing the utility of plant membranes, he discovered the effectiveness of xylem tissue. Xylem transports water from the roots to leaves, in the form of sap.

Evaporation moves water from the leaves, according to Karnik. NPR analogizes this process to placing a straw in a glass of liquid, noting “evaporation from the leaves has the same effect as sucking on the straw.”

As the water travels from the roots to the leaves, air bubbles grow. This problem, referred to as cavitation, slows water travel in plants but spurs technical innovation.

Karnik claims xylem can remove these bubbles. “The xylem has membranes with pores and other mechanisms by which bubbles are prevented from easily spreading and flowing in the xylem tissue,” he notes.

These same xylem pores that filter air bubbles could filter the disease-causing bacteria in water. His research indicates a simple piece of wood could protect millions from poor sanitation. In his lab, he peeled bark from a pine branch and remove the sapwood beneath it. He placed this wood containing xylem into a tube, releasing a stream of water through the tube onto the wood.

“We also flowed in bacteria and showed we could filter out bacteria using the xylem,” reports Karnik. The xylem removes an estimated 99.9% of the bacteria in water.

This simple approach contrasts sharply with previous technologies. Wood stands as one of the most affordable methods for water filtration. He hopes to expand development to overcome “technical hurdles.”

Yet Robert Jackson of Stanford University hesitates at the assurance of 99% effectiveness. Hundreds of thousands of bacteria occupy a single drip of water. This use of wood, though innovative, fails to stem the danger of this bacteria. For Jackson, this invention serves as a “short-term solution.”

Nearly one billion live without access to safe drinking water. The urgency of this reflects a need for short-term and long-term solutions. To secure the success of nutrition interventions, researchers must continue the development of these filtration technologies.

Ellery Spahr

Sources: NPR, World Bank
Photo: Lighting Essentials


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