Using wood to get a cleaner drink of water | WHAT REALLY HAPPENED

Using wood to get a cleaner drink of water

Following a major quake, Wellingtonians may have a local student to thank for a giardia-free drink of water.

Wadestown School student Jacqui Ormsby won last week's Wellington Regional Science and Technology Fair with her discovery native woods like totara could filter out the stomach illness-causing parasite. "The tree does it naturally. It goes up through the roots and it filters out the bugs and the dirt, while taking it to the branches."

The system the 13-year-old designed used gravity to drive it: a 2L water bottle is connected to a plastic hose fitted with a 15mm piece of bark-stripped wood, held in place by plumber's tape. Jacqui wanted a set-up any household could make in a situation like the aftermath of a major disaster.

"I wanted to focus on emergencies because of all the earthquakes that happen in New Zealand."

Of the six woods tested, some like pohutakawa, filtered out very little, she said. Totara showed good filtration of a dye the same size as giardia parasites, while moving through the 2L of water a lot faster than others such as Radiata pine.

However, Jacqui still estimated the average person might need to set up five filtration systems running constantly to supply themselves with their daily drinking water supply. She was also disappointed to discover water filtered through totara still contained some E. coli bacteria, other smaller organisms that can cause intestinal upsets.

She was inspired by an experiment she had read about American native woods being used as water filters. "They did it with wood you can't find here very often, white pine. I thought, hey, why can't I do this in New Zealand with wood you can find here?"

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