Recovery and reuse of alginate in an immobilized algae reactor

ABSTRACT

The use of microalgae for nutrients removal from wastewater has attracted more attention in recent years. More specifically, immobilized systems where algae cells are entrapped in beads in a matrix of a polysaccharide such as alginate have shown a great potential for nutrients removal from wastewater to low levels with reduced retention times and hence smaller footprint. However, a significant operational cost in the up-scaling of alginate-immobilized algae reactors will be the gelling agent alginate. To reduce expenditure of this consumable a proof-of-concept is given for an alginate recycling method using sodium citrate as a dissolving agent. Using algae beads made from virgin and recycled alginate yielded comparable removal rates for both phosphorus and nitrogen compounds from wastewater. At labscale, an alginate recovery of approximately 70% can be achieved which would result in a net operational cost reduction of about 60%.

GRAPHICAL ABSTRACT

KEYWORDS:

• Alginate
• immobilized algae
• phosphorus removal
• recovery
• recycle

Acknowledgements

The authors gratefully acknowledge the facilities, and the scientific and technical assistance, of the Australian Microscopy & Microanalysis Research Facility at the RMIT Microscopy & Microanalysis Facility, the facilities and technical support by Nadia Zakhartchouk at the Separation Science and Mass Spectrometry Facility, the facilities and the technical support by Muthu Pannirselvam at the Rheology and Materials Characterisation Laboratory and finally the facilities of the Food Research and Innovation Centre at RMIT University.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Rachel Whitton http://orcid.org/0000-0001-9378-0859

Bruce Jefferson http://orcid.org/0000-0003-4320-628X

Marc Pidou http://orcid.org/0000-0003-3031-9584

Additional information

Funding

Funding for this study was gratefully received by Severn Trent Water and the Royal Society of Chemistry Water Science group in form of the Alan Tetlow Memorial Bursary.