Kinetic characterization of microalgal-bacterial systems: Contributions of microalgae and heterotrophic bacteria to the oxygen balance in wastewater treatment

Metabolic activities of microalgae and heterotrophic bacteria were characterized in terms of dissolved O-2 uptake and production rates under dark and light conditions, assessing the contribution of both microbial groups to the O-2 balance during wastewater treatment. Up to 13 kinetic and stoichiometric parameters were determined, allowing a quantitative description of the O-2 production and uptake dynamics. Under dark conditions, the maximum specific O-2 uptake rates for microalgae and bacteria were 14.73 +/- 2.02 mgO(2) gVSS(-1) h(-1) and 2.37 +/- 1.52 mgO(2) gVSS(-1) h(-1), respectively. Microalgae were therefore the largest O-2 consumers under dark conditions, being responsible for up to 86 % of the total heterotrophic respiration. Under light conditions (photosynthetic metabolism for microalgae and heterotrophic metabolism for bacteria), microalgae supported a maximum specific O-2 production rate of 13.76 +/- 1.48 mgO(2) gVSS(-1) h(-1), while bacteria supported a maximum specific O-2 uptake of 2.37 +/- 1.52 mgO(2) gVSS(-1) h(-1). The oxygenation performance of the microalgal community was therefore superior to the O-2 respiration of heterotrophic bacteria under light conditions. The kinetic characterization performed provides critical information about the photosynthetic oxygenation potential, microbial growth and heterotrophic O-2 uptake, which is essential for design, optimization, and modeling of wastewater treatment processes.

Automated summary

Metabolic activities of microalgae and heterotrophic bacteria were analyzed in terms of O-2 uptake and production rates to assess their contribution to the O-2 balance during wastewater treatment. Results showed that microalgae were the main O-2 consumers in the dark, while their oxygenation performance was superior to that of bacteria under light conditions.