Microalgal bacterial floc properties are improved by a balanced inorganic/organic carbon ratio

• DOI: 10.1002/bit.22985
• Publication Date: 2010-10-29T07:38:24Z
• Authors: Sofie Van Den Hende; Han Vervaeren; Hans Saveyn; Guy Maes; Nico Boon
• Keywords: Bacteria; Water; 01 natural sciences; Carbon; 6. Clean water; Culture Media; Water Purification; 12. Responsible consumption; Bioreactors; Inorganic Chemicals; 13. Climate action; Microalgae; Organic Chemicals; Water Microbiology; 0105 earth and related environmental sciences

AbstractMicroalgal bacterial floc (MaB‐floc) reactors have been suggested as a more sustainable secondary wastewater treatment. We investigated whether MaB‐flocs could be used as tertiary treatment. Tertiary influent has a high inorganic/organic carbon ratio, depending on the efficiency of the secondary treatment. In this study, the effect of this inorganic/organic carbon ratio on the MaB‐flocs performance was determined, using three sequencing batch photobioreactors. The MaB‐flocs were fed with synthetic wastewater containing 84, 42, and 0 mg L−1 C‐KHCO3 supplemented with 0, 42, 84 mg L−1 C‐sucrose, respectively, representing inorganic versus organic carbon. Bicarbonate significantly decreased the autotrophic index of the MaB‐flocs and resulted in poorly settling flocs. Moreover, sole bicarbonate addition led to a high pH of 9.5 and significant lower nitrogen removal efficiencies. Sucrose without bicarbonate resulted in good settling MaB‐flocs, high nitrogen removal efficiencies and neutral pH levels. Despite the lower chlorophyll a content of the biomass and the lower in situ oxygen concentration, 92–96% of the soluble COD‐sucrose was removed. This study shows that the inorganic/organic carbon ratio of the wastewater is of major importance and that organic carbon is requisite to guarantee a good performance of the MaB‐flocs for wastewater treatment. Biotechnol. Bioeng. 2011; 108:549–558. © 2010 Wiley Periodicals, Inc.