Algae build up in lakes slowing

Attempts to slow the rate of algae build-up in Rotorua lakes are looking promising but farmers leaking waste into waterways is an area which still needs to be addressed, according to a water treatment specialist.

Enviromex New Zealand owner and director Peter Browne spoke about his aluminium sulphate treatment of Lake Rotorua's phosphorus levels yesterday at New Zealand's biggest water conference in Rotorua.

The contracted scientist said the Rotorua District Council had a goal of reducing algae build-up by 10 tonnes a year in Lake Rotorua, a problem which mainly stems from farm waste being leaked into the waterways and lakes.

He said algae feed on high phosphorus levels and the aluminium sulphate, dispersed into waterways, was showing good signs of consuming the phosphorus.

However, the Auckland-based scientist said this was only one way of stopping algae build up in the Rotorua lakes, with the far bigger issue being farmers leaking waste into waterways.

"We currently have the ambulance at the bottom of the cliff but we still need to address what's happening at the top."

He said the council was working towards stopping farmers leaking waste into streams and lakes but said that was a big process.

Until that could be fully addressed the lowering of phosphorus levels could be the best and most economical way of preventing algae build-up in Rotorua lakes.

The Water New Zealand Annual Conference and Expo finishes today after attracting slightly fewer than 1000 people during the three-day event. The annual conference included networking opportunities, educational talks, forums and 165 exhibitors.

About 60 speakers discussed issues affecting the water industry.