Microalgal bacterial floc properties are improved by a balanced inorganic/organic carbon ratio.
Microalgal 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-KHCO(3) 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.
Department of Industrial Engineering and Technology, University College West Flanders, Kortrijk, Belgium.
Sofie
S
Van Den Hende
Han
H
Vervaeren
Hans
H
Saveyn
Guy
G
Maes
Nico
N
Boon
D001419:Bacteria / Q000254:growth & development* / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology; D002244:Carbon / Q000032:analysis* / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry*; D007287:Inorganic Chemicals / Q000032:analysis / Q000378:metabolism; D058086:Microalgae / Q000254:growth & development* / Q000378:metabolism; D009930:Organic Chemicals / Q000032:analysis / Q000378:metabolism; D014867:Water / Q000737:chemistry*; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*
D003470:Culture Media; D007287:Inorganic Chemicals; D009930:Organic Chemicals; D014867:Water; D002244:Carbon