he Naked Scientists report that a team at Murdoch University Algae R&D Centre, in Perth, Western Australia, led by Navid Moheimani and Parisa Bahri, has developed a unique process that uses algae to treat effluent.
The process involves first passing the effluent through an anaerobic digester, which converts the organic material in the waste into biogas (methane). This can be used to generate electricity. The remaining liquid and suspended material produced by the digester is then fed to the algae.
This material is very high in ammonium, toxic to most organisms, and only specific algae can grow under these conditions. As the algae multiply, consuming the organic material, nutrients and minerals, they also remove a significant amount of carbon dioxide. The result is algal biomass with a very high protein content, and clean water.
So far, the team has successfully treated piggery effluent using this process. The biomass generated can be used as animal feed, fertilizer or an aquaculture feed. They have shown that the biomass can be safely used as a feed for juvenile marron and as a sustainable organic fertilizer. The biomass can also be digested by pigs. They’ve also started to investigate using their technique to clean up abattoir effluent, and further work with domestic and dairy effluents are also underway.
This project requires a good understanding of biological and engineering systems and processes. While algal cultivation depends upon understanding the biology of algae, there are many aspects of engineering that also need to be integrated into the process. Their approach will only work if they successfully integrate the biology and engineering.
The researchers see this approach is an example of a circular economy: the process not only cleans the wastewater and reduces the carbon footprint, but it also generates revenue through the generated biomass. A preliminary economic analysis indicates that, overall, the cost of biomass is around $2 for each kilogram they produce.
At this rate, the process seems to be generating positive cash flow, especially if the carbon credit and clean water value is added to the overall revenue. On the socio-economic side, they also significantly reduce the water way contaminations as algae concentrate most of them in their biomass.