Characterization of communities in a microalgae-bacteria system treating domestic wastewater reveals dominance of phototrophic and pigmented bacteria
2021
Barreiro-Vescovo, Santiago | Gonzalez-Fernandez, Cristina | de Godos, Ignacio
The consortia formed by microalgae and bacteria developed during semi-continuous operation of photobioreactors treating domestic wastewater was characterized by means of flow cytometry and DGGE techniques. While microalgae population was dominated by the inoculated wild strain Chlorella sorokiniana, the bacterial community included as activated sludge was totally replaced by microbial groups exhibiting adaptations to illuminated environments. The quantification conducted by flow cytometry evidenced bacterial population displacement favoring pigmented and photoheterotrophic groups. This fact was correlated with DGGE analysis that showed the dominance of Rhodobacteraceae family during steady state conditions and disappearance of Rhizobiaceae family present in the inoculum. This particular bacterial community composition was related with the limited organic matter consumption detected in the experimental reactors, estimated in removal rates of 64.2 ± 4.8% of biodegradable chemical oxygen demand present in primary treated wastewater. In conclusion, the dominance of photoheterotroph and pigmented bacteria reduced the metabolic capability of the photobioreactor resulting in insufficient wastewater treatment with regard to discharge regulations.
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