You’ve heard of harvesting rainwater and recycling greywater, the used water from laundry, dishwashing and bathing, for watering your garden or refilling your toilet. But what about treating and reusing blackwater – the wastewater you flush down the toilet?
The thought of recycling sewage water may turn your stomach, but that’s exactly what will be happening at this year’s Olympics Games: Wastewater from London’s sewers will be sanitized and used to fill toilets and irrigate landscaping at Olympic Park and Village, as well as provide cooling water for the energy center that powers the Olympic venues.
This innovative blackwater recycling program, along with other water saving measures like using efficient fixtures, will help the summer games reduce its use of potable – or drinking quality – water by 58 percent – exceeding its initial target of 40 percent.
This initiative is the first community-scale wastewater reclamation project to directly reuse non-drinking water in the U.K., according to the U.K. Olympic Delivery Authority (ODA), the organization responsible for constructing the games’ venues. The agency hopes that the program can become a model for other cities in the U.K. and across the globe.
Why choose blackwater?
Because London and the rest of southeastern England experience regular droughts, the ODA recognized that the new facilities had to conserve as much water as possible – not just during the summer games, but also in their future uses.
At first, the ODA focused on making the buildings as water efficient as possible, finding they were able to reduce water consumption by 30–50 percent just by installing efficient fixtures. But these savings were soon canceled out by a few Olympic venues that consumed huge amounts of water and did not benefit from simple efficiency measures. These facilities, including the energy center that uses water for process cooling, slashed the games’ overall water savings down to 18 percent.
It became clear that the ODA needed another source of water to keep up with the Olympic venues’ current and future demands. The organization quickly ruled out using local groundwater due to its energy-intensive treatment; it would also deplete one of London’s important contingency water sources during droughts.
The ODA also decided against using greywater as an alternative water source because of the new infrastructure that would be required to collect and pump this separate wastewater stream. A plan to harvest rainwater was also rejected due to similar concerns, although the ODA has set up several small-scale rainwater capture systems throughout Olympic Park.
With all of these ideas struck down, the ODA began researching reusing sewage water and, surprisingly, found it to be a viable option for Olympic Park. Unlike rainwater and greywater, there was a steady, predictable supply of sewage, and no new pipe and pumping networks would have to be built. In addition, sanitizing the blackwater for reuse would actually use less energy than treating groundwater and produce a higher quality water.
To set up the new program, the ODA constructed a water recycling plant within close proximity to both Olympic Stadium and the main sewer for northeast London – the plant’s water source. Because the only suitable location for the facility was in an ecologically sensitive area, the architects designing the recycling plant incorporated a living roof, pond and nature trail into the site plan to attract local wildlife.