Once considered a source of pollution, waste water now has fresh potential, writes Sarah Murray
With global water stress an increasing worry to companies, governments and others, attention is focusing on how to conserve this precious natural resource. However, as materials scarcity becomes more evident, another question is now on the lips of corporate leaders and policymakers – what value can be extracted from waste water?
Of course, part of the challenge is to prevent water from being wasted in the first place. The oil industry, for example, generates large volumes of waste water.
“They separate the oil and water, and inject it back into a salt water disposal well a mile underground and it’s never used,” explains James Wood, chairman and chief executive of US-based ThermoEnergy. “That’s fine where you have enough water. But it’s not so good in west Texas, where they have very bad drought conditions.”
ThermoEnergy’s flash vacuum distillation technology is a physical-chemical process that uses temperature and reduced pressure to separate chemicals, metals and nutrients from waste water. This technology, argues Mr Wood, could be used to turn the waste water produced by the extractive industries into water that could be used by farmers, particularly in areas of drought.
However, waste water contains rich seams of chemicals and minerals, from nitrogen and phosphorus to propylene glycol and heavy metals. Once viewed merely as a costly or even toxic problem to be dealt with, waste water and the materials it contains are increasingly being viewed as a means of creating value.
Often the extraction of materials from water is driven by legislation primarily designed to conserve water, preserve clean water or safely dispose of waste water
Nitrogen and phosphorus, for example, can create purification and algae blooms in waterways. Yet they are also valuable materials in the manufacture of fertiliser.
For this reason, Vancouver-based Ostara Nutrient Recovery Technologies has developed a way of recovering phosphorus and nitrogen from municipal and industrial waste water, and transforms them into fertiliser.
“The technology is very much geared towards making a marketable product,” says Phillip Abrary, Ostara president and chief executive. “We’ve changed our mindset from seeing these things as a source of pollution to developing technologies that can take them out and turn them into something with the same or greater value.”
Many of Ostara’s clients are municipalities for whom the appeal is that they are able to tackle pollution on several fronts. While the technology enables the cleaning of waste water, the fertiliser Ostara produces with the recovered phosphorus and nitrogen is a slow-release product that, because it does not dissolve in water, prevents the run off of chemicals into surrounding rivers and waterways.
Often the extraction of materials from water is driven by legislation primarily designed to conserve water, preserve clean water or safely dispose of waste water.
ThermoEnergy, for instance, developed its waste water treatment technology in New England after the introduction of federal standards for drinking water. The legislation – the National Pollutant Discharge Elimination System – requires a disposal permit for any water being put into a sewerage system.
In New England, with a vibrant metal-plating industry, the legislation created demand for technology that could clean dissolved metals, such as chrome, nickel and zinc, from the water these companies use in the metal-plating process.
However, a second benefit of ThermoEnergy’s technology has emerged. “The metal-plating industry now uses this machine to recover metals they otherwise would have thrown away,” says Mr Wood.
Another use is in extracting glycol used in the de-icing fluid that is sprayed on to planes at airports during freezing weather. “You have this flow back of water, from which they look to recover the chemicals because they are valuable,” he says.
Another extremely valuable commodity that can be extracted from water is alginate. In the Netherlands, Delft University of Technology and a consortium of partners have developed Nereda, a low-energy technology that makes minimal use of chemicals to extract alginate from waste water.
The alginate is currently used in food and medical products, but could also potentially be used in industries such as agriculture, chemicals, paper production and textiles.
With demand for raw materials rising, along with the price of these commodities, more of these kinds of technologies are likely to emerge. “As a growing population around the world, we need more of the things that we’re consuming and discarding – that’s a continuous trend,” says Mr Abrary. “So a sustainable source of materials and basic elements is key.”