New Zealand’s Lake Rotorua is a peaceful place with a violent past. It came into being some 200,000 years ago when a massive volcano blew up, collapsed and rain water filled its 10-mile wide caldera.
Today, Rotorua’s pellucid aquamarine water is a huge tourist magnet. But as the area developed, effluent from farms and nearby towns also fueled algae blooms that gobbled up oxygen and threatened to suffocate fish and other aquatic life in the lake.
Two years ago, local authorities brought in a nanotech weapon to fight the pesky microorganisms. They started using high-tech membranes riddled with tiny holes just 40 nanometers wide to filter out protozoa, bacteria, sediment, and unwanted nutrients like phosphorus and nitrogen.
GE, which developed the technology, calls it the ZeeWeed Membrane Bioreactor. As the name implies, the unique filtering membranes sway much like seaweed. They are coated with a special synthetic resin that gives them their undulating flexibility.
More than a million tourists come to Lake Rotorua and the surrounding area every year to dangle their feet in thermal streams, swim, fish and water-ski.
"The water being released by the previous treatment plant was still very high in nitrogen and phosphorus, and this was increasing the nutrient loads in the surrounding water courses,” says Chris Harpham, sales leader at GE Power & Water for the Asia Pacific region.
“We were able to retrofit the ZeeWeed membranes into the existing tanks on the treatment plant site,” Harpham says. “Now that it’s operating, it has led to a significant reduction in the nutrient load in the lake.”
In the middle of Lake Rotorua is the volcanic dome of Mt. Mokoia. Credit: James Dignam
Lake Rotorua is not the only big tourist destination ZeeWeed is helping to keep clean. Australia’s coastal cities of Cairns and Townsville, whose waterfront is just a few miles from the Great Barrier Reef, are using the technology to treat 50 million gallons of wastewater and agricultural runoff per day. Once again, Zee Weed is throwing a life preserver to aquatic life.
ZeeWeed is using seaweed-inspired membranes to filter out bacteria and algae nutrients.