cpt, jhb
+27 21 852 7198

PET bottles and sunlight key to purifying water

PET bottles – those used to bottle many carbonated and sweetened cold drinks as well as water – are the key to purifying water in areas without access to regulated water reticulations systems, or those where the system is unreliable or disrupted by natural disasters such as floods, earthquakes and cyclones or conflict.

This is the clear message from WHO consultant Andy Hart in a documentary called ‘Drops of Sun’.

The technique has been tested and recommended by the WHO (World Health Organisation) as well as the CSIR, and used by South African National Bottled Water Association (SANBWA) Chairman, John Weaver, on his regular trips into areas where the tap is not a common sight.  

The technique is referred to as SODIS, or solar disinfection. The UV-A rays in sunlight kill germs such as viruses, bacteria and parasites (giardia and cryptosporidia). The method also works when air and water temperatures are low. People can use the SODIS method to treat their drinking water themselves. The method is very simple and its application is safe.

And yet, there are still those who believe that PET bottles leach chemicals or toxic components into water, especially when exposed to direct sunlight.

“Perhaps these misinformed people will take note of more recent research, coming from the Swiss Federal Laboratories for Materials Testing and Research,” suggested SANBWA Executive Director, Charlotte Metcalf. “This organisation examined the diffusion of adipates and phthalates (DEHA and DEHP) from new and reused PET-bottles in the water during solar exposure.”

According to Metcalf, the levels of concentrations found in the water after a solar exposure of 17 hours in 60°C (140 °F) water were far below WHO guidelines for drinking water and in the same magnitude as the concentrations of phthalate and adipate generally found in high-quality tap water.

“There’s also been concerns voiced recently about the use of PET-bottles in this manner following a report from researchers at the University of Heidelberg who had looked at the release of antimony from PET-bottles stored over several months in supermarkets.

“However, the antimony concentrations found in the bottles were orders of magnitude below WHO and national guidelines for antimony concentrations in drinking water. Using clear PET bottles and Africa’s abundant sunlight is a cheap, easy and effective way to make certain water is drinkable.

“Those who incorrectly malign PET’s chemical properties should rather focus their energy on convincing those who consume beverages from this packaging format to recycle, as that’s the more urgent concern,” she said.