Microalgae-activated sludge treatment of molasses wastewater in sequencing batch photo-bioreactor

ABSTRACT

The aim of this work was the examination of the treatment potential of molasses wastewater, by the utilization of activated sludge and microalgae. The systems used included a sequencing batch bioreactor and a similar photo-bioreactor, favoring microalgae growth. The microalgae treatment of molasses wastewater mixture resulted in a considerable reduction in the total nitrogen content. A reduction in the ammonium and nitrate content was observed in the photo-bioreactor, while the effluent’s total nitrogen consisted mainly of 50% organic nitrogen. The transformation of the nitrogen forms in the photo-bioreactor was attributed to microalgae activity, resulting in the production of a better quality effluent. Lower COD removal was observed for the photo-bioreactor than the control, which however increased, by the replacement of the anoxic phase by a long aeration period. The mechanism of nitrogen removal included both the denitrification process during the anoxic stage and the microalgae activities, as the replacement of the anoxic stage resulted in low total nitrogen removal capacities. A decrease in the photobioreactor performance was observed after 35 days of operation due to biofilm formation on the light tube surface, while the operation at higher temperature accelerated microalgae growth, resulting thus in the early failure of the photoreactor.

KEYWORDS:

• Molasses wastewater
• activated sludge
• microalgae
• sequencing batch photo-bioreactor

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Costas Tsioptsias is a Dr Chemical Engineer, postdoc researcher at the Laboratory of Water Technology at TEI Thessaloniki, with expertise on green chemistry processes and biological wastewater treatment techniques. He has been involved in 8 research projects and has contributed to the publication of more than 22 papers in scientific journals.

Gesthimani Lionta was an MSc Chemical Engineer, working at the Laboratory of Water Technology at TEI Thessaloniki. She had been employed by several private enterprises for quality systems design, operation and auditing. Since 2012, she was working at a research project related to molasses wastewater treatment processes.

Petros Samaras is Dr Chemical Engineer, professor at the Laboratory of Water Technology of the Department of Food Technology at TEI Thessaloniki. He has participated in more than 50 research projects funded by national and EU sources. He is the main author and co-author in more than 100 papers, with an h-index of 28. His expertise is on water and wastewater treatment technologies with emphasis on food industries wastewater.

Additional information

Funding

This research has been co-financed by the European Union (European Social Fund – ESF) and Greek national funds through the Operational Program ‘Education and Lifelong Learning’ of the National Strategic Reference Framework (NSRF) – Research Funding Program: ARCHIMEDES III. Investing in knowledge society through the European Social Fund.