Green approach to increase wastewater recycling in regional towns

Rising rural populations, drought and climate change are making water scarcity a problem in country townships — with more efficient handling of sewage system wastewater part of the solution. Pioneered by Flinders University environmental health experts, local councils in South Australia are operating sustainable energy-efficient sewage treatment operations with low-cost high-rate algal pond (HRAP) systems.

Now, new research led by Flinders University is investigating improved effluent treatment and biosolids removal with ‘sequencing batch reactors’ — or low-cost ‘SBR-HRAP’ technology field trials — installed at SA Water’s Angaston wastewater treatment plant in the Barossa Valley.

Flinders University researchers say that the newer systems under development can work better and faster without major capital expense, due to the latest research of new approaches to bio-processing inside them.

The SBR techniques under development involve a new kind of algae and improved removal of waste from the water, for better quality non-potable water for use in parks, gardens, sporting fields and other purposes.

“Supported by SA Water and the ARC Biofilm Research and Innovation Centre at Flinders, we are trialling selective enrichment of algal-bacterial combinations to produce higher quality treated effluent,” said Professor Howard Fallowfield from the College of Science and Engineering at Finders University. “Using wastewater from the Angaston community, our six pilot-scale HRAP tanks will compare the performance of these improved processes against the original HRAP operations.”

Large high-rate algal pond systems, which have been treating wastewater at local council-owned facilities near Kingston-on-Murray (since 2013) and Peterborough (since 2018) in South Australia, use low-energy paddlewheels to move township and business organic waste along shallow channels where harmless green microalgae and bacteria remove pathogens and contaminants.

PhD candidate Felipe Sabatté, who has used a native freshwater filamentous algal population to produce higher quality clarified treated effluent, says the latest developments will be scaled up in the Angaston field trials.

“While high-rate algal ponds are an accepted method of wastewater treatment, particularly for regional and rural communities, they utilise microalgae that are difficult to remove from the treated wastewater leading to unacceptably high suspended solids in the discharge,” he said. “These larger filamentous algae offer the prospect of easier separation from the treated wastewater, significantly improving treated effluent quality.”

“The outcome of this research provides a new operational strategy for wastewater HRAPs, particularly for the benefit of regional and rural communities challenged with water restrictions and to help meet UN SDG6 (clean water and sanitation) targets in the long run,” he added.

Also at the Angaston trial site, Flinders ARC Biofilm Research and Innovation Centre PhD researcher Sam Butterworth is investigating how to use this new technology to develop dense, algae-bacterial granules, which can be more readily removed from wastewater and to potentially reduce phosphorus levels.

“Algae-bacterial granule formation is a positive way for biofilms to form dense, fast-settling biomass and improve treated wastewater quality,” he said. “Using microalgae in high-rate algal ponds is increasingly seen as a better alternative to other wastewater treatment systems, such as activated sludge.”

Traditional wastewater treatment methods can use more energy and water and can be less sustainable due to higher greenhouse gas emissions.

An independent validation of the HRAP projects approved the treated wastewater to be used for non-food crop irrigation. For example, the Kingston-on-Murray ponds supply reuse water to irrigate a woodlot, and the ponds in Peterborough provide reuse water for a golf course and a sports field.

Image: Peterborough HRAP