Wetox strikes gold in sludge

Wetox goes panning for phosphates and comes up with $1 million.

WetoxWetox goes panning for phosphates and comes up with $1 million. 

Has it come to this? Grubbing around in our own sewage for resources? Well, yes it has, and quite right, too.

Flushing stuff away with water is a really effective way of keeping our homes and workplaces tidy and hygienic, but it’s also a great way of losing valuable resources down the plughole, which then become a major waste disposal and pollution problem.

Wellington-based Wetox is one of a number of innovative Kiwi companies donning the nose pegs to see what can be usefully done with the resulting mess. It is owned by Victoria Link Limited, the intellectual property commercialising company owned by Victoria University, and led by chief executive officer Dr Kevin McKay at Wellington City Council’s Creative HQ business incubator.

After six months of negotiations it’s just scored government backing for a $1 million pilot scheme at Palmerston North’s wastewater treatment plant. A neat choice, as the plant recently got some very dirty looks from water regulators for highly polluted wastewater discharges into the Manawatu River.

Wetox adds special chemicals to sewage sludge and uses extreme heat to break the organic matter down into its various components. This reduces the volume of sludge by more than 90 percent. Once it cools, it leaves behind carboxylic acid, which is used in all sorts of products from food to perfume.

Crucially, other minerals and metals are also recovered. Wetox’s unique focus is on the recovery of valuable phosphates, most of which have to be imported into the country and can cause problems like freshwater pollution and algal bloom if allowed to flow unchecked into our rivers and lakes.

The company also hopes to develop the technology so that the steam produced can be harnessed by turbines to create energy, although it’s not part of the current pilot.

McKay has been wading around in dirty water in one way or another since doing his PhD in the field back in the early 1980s.

“Phosphate is essential to crop growth,” McKay says. “The world production of rock phosphate used to make fertilisers may have peaked and appears to be in decline, with a corresponding increase in cost.

“The lack of fertilisers will be a significant barrier to increased agricultural production needed to satisfy an increasing population.”

The company reckons New Zealand could do with about 50 Wetox systems, and there’s space for more than 10,000 worldwide. This stacks up to a possible $50 billion market, even without looking at the enormous potential in the sludge mountains of India and China. The company is already sniffing about in the UK and Europe, and is on the hunt for financial backers and partners to take things further.

“The idea kicked around the bottom drawer for a long time,” says McKay.

“The point came when we either had to use it or lose it. As we talked to potential customers, we realised that this technology would solve a significant and growing problem not only in New Zealand but worldwide.”

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