PEFT: Clever thinking creates cleaner water

Oct 25, 2012
Ironing out water quality problems: University of Waikato researchers Dr Hilary Nath (left) and Associate Professor Alana Langdon with their PEFT cell.

Two chemists from the University of Waikato have come up with an innovative method for treating bore water on Waikato farms.

They're currently trialling the system on a Waikato farm and may have hit upon a low-cost solution for developing countries, where many people have limited access to clean and affordable water.

Using electrochemistry

Associate Professor Alan Langdon and post-doctoral researcher Dr Hilary Nath decided to try using electrochemistry to remove the iron and manganese prevalent in bore water from Waikato's peaty soils.

The residues give the water its typical browny-orange colour, and generally make it undrinkable without expensive treatment using aerators, filters, ion exchangers and tanks.

The researchers came up with a simple system that uses electric current passing between two perforated titanium electrodes to turn naturally occurring in the water into chlorine.

The chlorine then oxidises and precipitates out the metal contaminants, and also disinfects the water passing through the system, making it safe to drink.

Best of all, the whole system can be powered by a car battery.

"By bringing the electrodes closer together than anyone else has been able to we can reduce and consume less power," says Dr Nath. "And because the flow path through the cell is very short, we can achieve good water flow at modest pressure."

PEFT System

The system is known as PEFT – perforated electric flow through – and is patented in New Zealand with international patents filed. A prototype will be on show at the University of Waikato stand at Equidays next month; the university is a strategic partner of Equidays which runs from 2-4 November.

Drs Langdon and Nath are now testing the prototype, and getting good results – they've seen total oxidation of iron during their trial.

"The initial focus will be disinfection of harvested , disinfection of water supplies derived from surface water and bore water contaminated with iron – we need to be very sure our technology is robust before contemplating overseas markets, particularly in developing nations."

The researchers noticed that the closer together the two electrodes were positioned, the higher the electric field generated between them. And the higher the electric field, the more potent the chlorine being produced.

Clever technology

The two together were so powerful they could kill bugs in the water at much lower chlorine levels than normally required – the electric field was able to puncture the membrane of a bug making it 100 times more susceptible to the disinfecting effect of the chlorine.

At slightly higher applied voltages the PEFT cell can also disinfect water by the alone, with no need to produce any chlorine.

"It's low technology, but it's very clever nevertheless," says Dr Langdon.

Explore further: Measuring the height of the world's forests

add to favorites email to friend print save as pdf

Related Stories

Salt Water System Could Generate Hydrogen

Mar 18, 2009

(PhysOrg.com) -- The idea of generating hydrogen from salt water has often been claimed to work effectively. However, the systems proposed so far generally require a much greater energy input than the energy ...

In wake of flooding, disinfect contaminated wells

Sep 16, 2011

The central and eastern parts of the state were saturated by frequent heavy rains in early August before being drenched by Hurricane Irene and then inundated by the remnants of Tropical Storm Lee. The resulting ...

Desalinating seawater with minimal energy use

Jul 12, 2011

At a pilot facility in Singapore, Siemens has cut the energy needed to desalinate seawater by more than 50 percent. The plant processes 50 cubic meters of water per day, consuming only 1.5 kilowatt-hours of ...

Recommended for you

Measuring the height of the world's forests

1 hour ago

If we know the height of the world's forests, then we can estimate how much carbon they store. That will improve our understanding of how forests interact with the atmosphere and their role in mitigating ...

Scientists probe leak risk from seabed CO2 stores

1 hour ago

A UK-led international research team has carried out the first experiment to recreate what would happen if CO2 started leaking after being stored deep under the sea floor. Their findings add weight to the ide ...

User comments : 0