Apr 13, 2017

Green solution for industrial wastewater

Green solution for industrial wastewater

Algae is removing heavy metals from nickel refinery tailings water in a James Cook University research project.

JCU chemical engineering academic Dr. Madoc Sheehan, who is a chemical engineering sustainability expert, said there was a lot of potential for this type of nature-based technology.

“Eventually we’ll be able to clean mine waste water using algae, concentrate the heavy metals, sequester CO2 from the atmosphere and turn it all back into energy,” he said.

“Using nature in this way is a step toward more sustainable industry, with less impact on threatened ecosystems such as the Great Barrier Reef.”

Dr Sheehan said the microalgae biofilms generally grew on the surface of wet rocks and on the sides of boats and marine structures.

Researchers on site at the Queensland Nickel complex outside Townsville.

“It’s better known as biofouling and it’s an expensive and time-consuming problem for boat owners and marine operators,” he said.

“It grows by using energy from the sun while simultaneously consuming CO2, nutrients and dissolved metals, and it can absorb other metals that are dissolved in water.”

Dr Sheehan said the microalgae biofilm grown in Queensland Nickel tailings water was 40 per cent carbohydrate, making it suitable for converting into a biofuel such as ethanol.

“This means the energy obtained by turning the algae into biofuel could potentially be re-used to harvest and grow the algae in the first place, making the process cheap and effective,” he said

The Queensland Nickel site contains dissolved metals such as cobalt, nickel and manganese, yet the research team found they could grow algae at rates similar to commercial algae operations and clean the water at the same time.

Associate Professor Kirsten Heimann, an industrial algal biotechnologist and ecotoxicologist, said the water could be more easily re-used by industry once it was cleaned, and posed less of a danger to the reef.

“Algae grown in the tailings water reduced the nitrogen content and the heavy metal content of the water, lowering its pollution potential. It absorbed the dissolved metals as it grew, to the extent that when harvested at least 10 per cent of the algae’s dry weight was made up of pollutants,” she said.

Conservative estimates showed the growing area required to reduce the heavy metal concentration in the tailings water by 75 per cent would be less than twice that of a full-size football field.

The next step is for the scientists to take their laboratory results and test them out on a full-scale industry tailings dam.