Saltworks Technologies Inc.

Ben Sparrow and Joshua Zoshi are the founders of Vancouver based Saltworks Technologies Inc. Sparrow and Zoshi met at Simon Fraser University in Vancouver while completing their MBAs. They see the same problems and issues that many parts of the world see and are forecasting - how to take salt out of seawater. There is a lot of water on the Plant - but 97% of it is salty and over half of the remainder is frozen at the poles or in glaciers. One answer is desalination - historically expensive mainly due to the energy needs.

Sparrow and Zoshi have a new idea and their test plant becomes operational in November. The firm estimates that they can produce 1,000 litres of drinking water with less than one kWh of electricity. Their process is fuelled by concentration gradients of salinity between different vessels of brine, These different salinities are brought about by evaporation.

By comparison, existing desalination plants work in one of two ways. Some distill seawater by heating it up to evaporate part of it. They then condense the vapor - a process that requires electricity. The other plants use reverse osmosis. This employs high-pressure pumps to force the water from brine through a membrane that is impermeable to salt. That, too, needs electricity. Even the best reverse-osmosis plants require 3.7 kWhs of energy to produce 1,000 litres of drinking water.

The Saltworks process begins by spraying seawater into a shallow, black-bottomed pond, where it absorbs heat from the atmosphere (sounds like San Diego as a U.S. test site to me). The resulting evaporation increases the concentration of salt in the water from its natural level of 3.5% to as much as 20%. Low-pressure pumps are then used to pipe this concentrated seawater, along with three other streams of untreated seawater, into a desalting unit. The process basically creates an electrical circuit. Instead of electrons carrying the current, though, it is carried by electrically charged atoms (ions).

Salt is made of two ions: positively charged sodium and negatively charged chloride. These flow in opposite directions around the circuit. Each of the four streams of water is connected to two neighbors by what are known as ion bridges. These are pathways made of polystyrene that has been treated so it will allow the passage of only one sort of ion - either sodium or chloride. Sodium and chloride ions pass out of the concentrated solution to the neighbouring weak ones by diffusion through these bridges (and chemical will diffuse from high to low concentration in this way). The trick is that as they do so, they make the low-concentration streams of water electrically charged. The one that is positive, because it has too much sodium, thus draws chloride ions from the stream that is to be purified. Meanwhile, the negative, chloride-rich stream draws in sodium ions. The result is that the fourth stream is stripped of its ions and emerges pure and fresh.

Clever engineering and a simple idea - www.saltworkstech.com