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Solar energy for wastewater treatment

by Geraldine Hinter

Dr. Bo JinAustralia's dwindling water resources means that improving the quality of treated wastewater from sewage treatment plants for re-use has become more important than ever.

Researchers at UniSA are developing a unique treatment for wastewater that guarantees improved water quality over existing treatments without relying on expensive chemicals.

The poor quality of treated wastewater has limited its use for agriculture and aquaculture, according to Dr Bo Jin, Director of UniSA’s Water Environment Biotechnology Laboratory.

“The last stage of any water treatment is to remove micro-organisms. Currently we use chlorine as the disinfectant but, even after treatment, the water still contains organic compounds. Chlorine removes the micro-organisms but reacts to the organic pollutants, producing disinfection by-products that are biologically undegradable and toxic and can’t be removed from the water. When transferred to the eco system, they can cause serious health consequences if used in agriculture and other industries. This growing problem is of particular concern to the United Nations, where close attention is being paid internationally to organic pollutants, which cannot be removed economically – but a solution is on the way,” he said.

UniSA researchers are developing a single stage treatment that can remove biological and chemical contaminants in the treated wastewater from sewage treatment plants.

The new solar nano-photocatalytic wastewater treatment process can replace a chlorination disinfection step as a tertiary treatment process to disinfect the micro-organisms and at the same time remove the organic compounds, making the wastewater suitable as a water resource.

“Normally micro-organisms are used to break down large organic compounds but, because these compounds are biologically undegradable, we have to use another form of energy to break them down. Our energy comes from UV sunlight in association with photocatalysts. Energy generated from the photocatalyst cell reaction can kill micro-organisms and break down the undegradable compounds, resulting in clean water that can be used for an extended range of agriculture and aquatic uses – and it won’t damage the eco system,” Dr Jin said.

“The other good news is that this treatment process will be very cost effective because the solar photocatalysts can be recovered and reused. They use cheap energy from the sun.”

Dr Jin recently won a Federal Government Australian Research Council Linkage Grant of $285,000, with additional financial commitment from industry partner Australian Water Quality Centre, to further develop this novel process, looking at water quality objectives of technical reliability and economic and environmental sustainability.