BACKGROUND:Most photobioreactors used for wastewater treatment with anoxygenic photosynthetic bacteria (APB) are based
on suspended cultures because APB have poor biofilm-forming ability. In this study, a photo-rotating biological contactor
(PRBC) was applied for the culture of APB biofilm using azo wastewater, with a particular emphasis on the formation of APB
biofilm and its relationship to other microorganisms and exopolysaccharides (EPS).
RESULTS: The PRBC was successfully used for the cultivation of APB biofilm and in the removal of chemical oxygen demand
and color. In situ analysis showed that APB biofilm formation can be divided into two distinct stages: development and
differentiation. In the development stage, nonphotosynthetic filamentous microorganisms initially proliferated on a disc
surface and promoted the adherence of APB. In the differentiation stage, filamentous microorganisms and their EPS matrices
caged APB in the inner layer and stabilized the APB biofilm. During biofilm stratification, the biofilm biomass and APB numbers
reached 24.2 ± 0.63 g L−1 and 4.8 ± 0.6 × 108 CFU (g dry biofilm)−1, respectively. The dominant APB in the mature biofilm were
identified as Rhodopseudomonas, Rhodomicrobium, and Chlorobium.
BACKGROUND:Most photobioreactors used for wastewater treatment with anoxygenic photosynthetic bacteria (APB) are basedon suspended cultures because APB have poor biofilm-forming ability. In this study, a photo-rotating biological contactor(PRBC) was applied for the culture of APB biofilm using azo wastewater, with a particular emphasis on the formation of APBbiofilm and its relationship to other microorganisms and exopolysaccharides (EPS).RESULTS: The PRBC was successfully used for the cultivation of APB biofilm and in the removal of chemical oxygen demandand color. In situ analysis showed that APB biofilm formation can be divided into two distinct stages: development anddifferentiation. In the development stage, nonphotosynthetic filamentous microorganisms initially proliferated on a discsurface and promoted the adherence of APB. In the differentiation stage, filamentous microorganisms and their EPS matricescaged APB in the inner layer and stabilized the APB biofilm. During biofilm stratification, the biofilm biomass and APB numbersreached 24.2 ± 0.63 g L−1 and 4.8 ± 0.6 × 108 CFU (g dry biofilm)−1, respectively. The dominant APB in the mature biofilm wereidentified as Rhodopseudomonas, Rhodomicrobium, and Chlorobium.
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