Raina Pang
Jan 31, 2012

All tapped out? New methods for improving drinking water

Created at Jan 31, 2012, 1:52am PST

As someone who grew up with instant water from the tap, it’s easy to forget that water is a limited resource. Constant accessibility to clean water allows many people, myself included, to take uncontaminated water on demand for granted. Clean water, however, is not an unlimited resource. Some may falsely believe that the crisis over clean water pertains only to those living in developing nations, but increasing droughts and contamination of drinking water with heavy metals and radioactive material means that lack of access to clean water affects everyone. This makes finding solutions to decontaminate water of the utmost importance and scientists have been working hard to address this growing concern.

In developing countries, over one billion people consume water contaminated with pathogenic bacteria, viruses, protozoa, parasites and sediment. Lack or limited access to clean water has widespread effects on disease burden, economics, food supply, education, and gender equality. One innovative solution may be the Moringa oleifera tree. Seeds from Moringa oleifera, often called the ‘miracle tree,’ have been shown to kill microorganisms as well as remove dyes, detergents, arsenic, cadmium and color agents in water. The use of this seed to decontaminate water, however, has been limited by excess organic matter remnants that feed new bacterial growth in the water, reducing the time it can be stored post-treatment. The antimicrobial properties of the Moringa oleifera seed are attributed to the presence of a natural cationic protein called MOCP. MOCP contains a hydrophobic proline surrounded by a positively charged section. Negatively charged particles such as bacteria are electrostatically drawn to the positively charged MOCP. Recently, Stephanie B. Volegol and colleagues at Pennsylvania State University added isolated MOCP to negatively charged sand, creating functionalized sand. This functionalized sand killed microorganisms without leaving behind organic sediments; thus, this technique could provide a local and sustainable way to create storable drinking water.

Lack of sanitation is not the sole cause of disease related to water. Arsenic in drinking water affects over 60 million people. While it has long been known that high doses of arsenic can easily kill a person, recent investigations suggest that long-term consumption of low doses of arsenic also poses significant health risks. Removal of arsenic, however, is possible both on a large and individualized scale.

Subterranean arsenic removal (SAR) appears to be a promising approach to remove of arsenic in a sustainable way that requires minimal costs to operate and maintain. This technique has been implemented in six plants in West Bengal and is being tested in the US, Cambodia and Vietnam. The working principle behind SAR is adsorption, which eliminates the need for chemicals and filters. Controlled oxidation converts arsenite to a less mobile arsenate, ferrous iron to ferric iron, and manganese II to manganese III. Arsenate is adsorbed by manganese III and ferric iron, reducing arsenic levels. Major limitations to this approach are the requirement of the presence of high iron levels and the need for electricity to power the pump, so this approach is not feasible in all locales.

In addition to SAR, nanomateriels have also been offered as an inexpensive, easy solution for arsenic detection and removal that can be applied at an individual level. Sherif A. El-Safty at the National Institute for Materials Science created a high order mesoporous (HOM) structure, which contains a functional group that removes even trace amounts of arsenic. During the adsorption phase, the nanomaterials change colors signifying the removal of arsenic.

Even less technologically advanced solutions have been offered for arsenic removal. Tsanangurayi Tongesayi at Monmouth University showed that plastic bottle pieces coated with cysteine, an amino acid found in dietary supplements and foods, can remove arsenic. This approach is advantageous as it uses locally available, cheap products -- regular plastic bottles -- and a technically easy approach. Application of cysteine to the plastic bottle piece is an easy procedure and then the piece is simply stirred in water. The cysteine binds to arsenic and the plastic bottle pieces with the bound arsenic are removed.  

Joel Pawlak and colleagues at North Carolina State University have found a potential multipurpose water decontaminate. They coated wood fibers with a solid foam formed from the combination of hemicellulose, a byproduct of forest materials, and chitosan, crustacean shells crushed into a powder. This creates a spongelike materiel that can remove a variety of water contaminants including radioactive iodide, heavy metals and salt. Because this is a filtering method it requires no electricity, which could be particularly useful in disaster situations where electricity is unavailable.

Access to clean drinking water is a necessity for water-based life such as ourselves. The importance of access to clean water has gained attention from celebrities and the scientific community, and rightly so. Research like these studies is bringing us closer to widely implementable, inexpensive solutions to provide clean drinking water.