Taking a shower is a refreshing way to start the day, but much of the energy used to heat the water is wasted as the warm water flows off of you and down the drain. Recirculating showers seem like a great idea. They take the waste water from the bottom of the shower and shoot it back onto the top of you. They been attempted before, but always suffer from one problem: who wants to shower in their own filth? Popular Science has more on an invention that might just solve this problem.
In 2004, Peter Brewin, an industrial-design student at the Royal College of Art in London, set about creating a more efficient shower that doesn’t require lower pressure. It couldn’t just capture and recirculate the water; most countries require shower water to meet potable-water standards. So instead he designed a miniature treatment plant that continuously captures, cleans, and recirculates 70 percent of the water used during a shower. Even with the energy the system consumes, it still uses 40 to 70 percent less power because the system doesn’t have to heat as much water. Over the course of a year, a typical household would use 20,000 to 32,000 fewer gallons of water with Brewin’s system. That, in turn, would save a local treatment plant upward of 200 kilowatt-hours of energy.
Because other water-treatment processes are too slow for real-time recirculation, Brewin decided to use pasteurization, the quick heating and cooling method for purifying milk. Shower water is already about 106°F when it hits the drain. A heat exchanger and a small electric heater raise the temperature the extra 56 degrees needed to reach the pasteurization point of 162°. To filter out dirt particles, Brewin constructed a funnel that spins the water that flows into it. Centrifugal force flings the heavy undissolved particles to the edges, where they are washed down the drain.