Science Collaboration Spells the End for Algal Bloom

29 May 2008

A volcanic mineral modified to enhance its ability to absorb phosphorus could provide the solution to reducing New Zealand’s summer-time plague of algal blooms in lakes and waterways.

The latest monitoring results from a product trial in Rotorua’s Lake Okaro, where water quality is perceived to be the poorest of all Rotorua lakes, has revealed a 40-60% reduction in the lake’s phosphorus levels since 112 tonnes of modified zeolite was applied in September 2007.

Additional toxicity testing in the lake has also confirmed that there have been no toxic effects from applying the product.

The modified zeolite was developed in collaboration between Crown Research Institute Scion and Matamata-based industrial minerals company Blue Pacific Minerals. The lake trial was commissioned and funded by Environment Bay of Plenty, and supported by researchers from the University of Waikato and NIWA.

Zeolite is a volcanic mineral traditionally used in absorbency markets, such as for chemical spill products, and in sports turf and cat litter.

Now modified by the scientists at Scion, the transformed product is able to act as a binding agent that targets phosphorus and other harmful nutrients.

Environment Bay of Plenty Rotorua Lakes Programme Manager Andy Bruere says the positive trial results are great news not only for Rotorua, but for all New Zealanders as water pollution caused by septic tanks, fertilisers and farm run-off is increasingly becoming a nationwide problem.

“Algal booms are formed as a direct result of the high levels of nutrients, such as phosphorus, in our lakes,” Andy says.

“Environment Bay of Plenty has invested in this full-scale lake trial as part of a wider lakes management strategy, including a proposed $25 million sediment capping project targeted at Lake Rotorua, so to see such positive results is a fantastic outcome for everyone.

“Given these most recent results, we hope to see a significant improvement in Lake Okaro water quality in the next two to three years, without the need for further intervention.”

Researchers will continue to monitor the lake over the 2008-2009 summer period, when the next algal bloom would normally occur, through until winter 2009.

Scion chief executive Tom Richardson says nutrient pollutants are a billion-dollar problem world-wide. He says the research institute has combined its experience in developing remediation technologies to protect New Zealand’s natural resources, with a product supplied locally in such a way that will have a significant payoff for the region and the environment.

“Typically, phosphorus from land run-off and point sources is carried into the lakes via our waterways. It then accumulates in sediments and if the deeper waters become devoid of oxygen, which can occur in degraded lakes during summer, the phosphorus is released back into the water. These high nutrient levels create the perfect conditions for algal blooms,” he says.

“The Lake Okaro trial has confirmed that when applied to the lake bed, the modified zeolite acts as a sediment cap, so instead of phosphorus being released from the sediment, it is absorbed by the product and effectively trapped.”

Following the success of the first ever full lake trial, Blue Pacific Minerals Managing Director Dave Hill says the company is exploring opportunities to commercialise the product.

“We think the modified product provides local and national governing bodies with another tool that will help them achieve their objective to clean up New Zealand’s waterways.

“Whilst clean-up plans differ depending on the nature of the pollution, the modified zeolite definitely supports goals to manage nutrients,” he says.

The New Zealand government recently announced it would meet about half the total $144.2 million cost to clean up Rotorua’s worst affected lakes, contaminated by nutrient run-off and suffering closures in the summer as a result of algal blooms.