Purification of ammonia-polluted water through biofilm augmentation: operating conditions and key microbial community

Abstract:

[Objective] We compared the effect of nutritional conditions and start-up method on the biofilm augmented purification performance of ammonia-polluted water and the microbial community structures. [Methods] The effect of ammonia removal was tested in three lab-scale reactors, including control reactor (Blank), biofilm reactor with the raw carrier (Raw) and biofilm reactor with the functional bacteria-immobilized carrier (PCC). The microbial community structures were assessed by terminal restriction fragment length polymorphism and the succession process of community was analyzed using the plot of nonmetric multidimensional scaling. [Results] When the C/N ratio was kept at 1:1 for 25 days, the ammonia removal efficiency was only 10%?20% for all the reactors, except for that the PCC showed a temporary high efficiency in the first 5 days. However, the ammonia removal efficiencies of both the Raw and PCC were higher than 95% when the C/N ratio was adjusted to 2:1. The NMDS results showed that the microbial structures of Raw and PCC had high similarity when the C/N was 2:1, and the dominant bacteria were composed of Gammaproteobacteria, Actinobacteria and Nitrospira. [Conclusion] The C/N ratio is not only a key factor impacting on the ammonia removal efficiencies of biofilm augmentation but also a driving force for the shifts of microbial community structures in the biofilm reactors.