Can This 'Supermolecule' Solve The PPCP Problem?

Pharmaceutical and personal care products (PPCPs) have for years appeared to be an intractable problem for wastewater and drinking water treatment operations.

When washed down drains and flushed down toilets, these chemical agents enter our wastewater streams, where their trace presence (usually so small that they are measured in parts per billion or parts per trillion) escapes regulation, thwarts treatment technology, and finds its way into source water and from there, eventually, drinking water. PPCPs in source water bodies and drinking water have been thought to cause negative reactions in wildlife and consumers.

As noted above, the trace nature of PPCPs means that their presence is not yet regulated and solutions to treat for them are scarce. But a new discovery might provide a potent weapon for treatment operations.

An academic from the United Kingdom’s University of Surrey, Danil de Namor, has discovered a “supermolecule” known as calix[4] that can seek out and remove certain pharmaceuticals from water. It’s the culmination of nearly a lifetime of work.

“We have been working in the field of supramolecular chemistry for about four decades and on calix[4] compounds for the last three decades, as these are among the latest incomers in the field,” said Namor. “We discovered the selectivity of these receptors for guests from thermodynamics using calorimetry[1]. This technique gives quantitative information regarding the ability of the receptor for the targeted contaminant.”

Namor believes that his team of researchers can now design receptors on calix[4] molecules that will selectively attract and bind with water pollutants. That will allow treatment operations to identify the presence of these pollutants and to more easily remove them.

“This study allows us to visualize the specific receptor-drug interactions leading to the selective behavior of the receptor,” Dr. Brendan Howlin, a co-investigator at the University of Surrey, said, per a release from the school. “As well as the health benefits of this research, molecular simulation is a powerful technique that is applicable to a wide range of materials.”

The research was inspired by the insidious nature of PPCPs in water supplies. Though limited to small concentrations, Namor believes any amount of pharmaceuticals being ingested through water poses a threat.

“Between 30 and 90 percent of pharmaceuticals taken into the body pass through into the water supply,” he said. “Clearly this is then diluted by volume… Targeted investigations in the United Kingdom, the U.S.A., and Australia found that pharmaceuticals are largely present in drinking water at concentrations several orders of magnitude below the minimum therapeutic dose.”

The researchers see calix[4] as a potential tool to monitor and eliminate PPCPs at treatment plants around the world. After publishing a paper on the subject, the team has been lecturing throughout Europe. The next step will be to take the laboratory work and turn it into a pilot plant process, which will likely require some industry partners. Despite the fact that there is much work still to be done, the supermolecule appears easy to incorporate into applicable technology.

“The material can be incorporated into cheap and simple columns that can be used to filter water supplies,” said Namor.

Though more stringent regulation may be needed to truly motivate treatment operations to focus on PPCPs, technological solutions such as this are more than welcome.