Modelling microbial competition in nitrifying biofilm reactors

Abstract

A large variety of microbial parameter values for nitrifying microorganisms has been reported in literature and was revised in this study. Part of the variety was attributed to the variety of analysis methods applied; it also reflects the large biodiversity in nitrifying systems. This diversity is mostly neglected in conventional nitrifying biofilm models. In this contribution, a one-dimensional, multispecies nitrifying biofilm model was set up, taking into account the large variety of the maximum growth rate, the substrate affinity and the yield of nitrifiers reported in literature. Microbial diversity was implemented in the model by considering 60 species of ammonia-oxidizing bacteria (AOB) and 60 species of nitrite-oxidizing bacteria (NOB). A steady-state analysis showed that operational conditions such as the nitrogen loading rate and the bulk liquid oxygen concentration influence both the macroscopic output as well as the microbial composition of the biofilm through the prevailing concentration of substrates throughout the biofilm. Considering two limiting resources (nitrogen and oxygen), the coexistence of two species of the same functional guild (AOB or NOB) was possible at steady state. Their spatial distribution in the biofilm could be explained using the r- and K-selection theory.

Nitrifying biofilms deprived of organic carbon show higher functional resilience to increases in carbon supply

“…Nitrobacter were also identified as the dominant NOB at low C/N ratios (0-2.3) in a previous study 16 . However, other studies did not detect Nitrobacter in autotrophic biofilms 13,20,40 , suggesting that the initial microbial community composition may influence the steady-state community 55,56 . By contrast, Nitrospira was the dominant nitrifier in R1, present at a relative abundance as high as 20%.…”

Influence of process dynamics on the microbial diversity in a nitrifying biofilm reactor: Correlation analysis and simulation study

“…As the focus of this contribution is on the effect of process dynamics on the nitrifying community, no sensitivity analysis was performed but instead it was verified by trial and error whether the simplest possible model was able to simulate the overall reactor behavior (nitrite vs. nitrate accumulation, besides residual ammonium concentration) when only selected microbial parameters were calibrated. The selection of microbial parameters was based on the results of Vannecke and Volcke () (importance of maximum growth rate and affinity for electron donor and acceptor) and Vannecke et al () (importance of endogenous respiration, in the current contribution replaced by decay).…”

“…Microbial diversity is typically neglected in conventional models, which at most make a distinction between functional guilds, that is, AOB and NOB in case of nitrification processes. Nevertheless, multispecies models including microbial diversity are useful tools to investigate in which way microbial population dynamics are influenced, for example, by various microbial properties (Vannecke and Volcke, ) or biofilm characteristics (Brockmann et al, ). They are also essential to study the relation between macroscopic reactor behavior and microbial population dynamics.…”

Microbiological Diversity Demonstrates the Potential which Collaboratively Metabolize Nitrogen Oxides ( NOx) under Smog Environmental Stress

“…According to the recent paper, the highest denitrification rate can be over 90% [15][16][17][18][19][20][21]. The two types of bacteria can metabolize NOx under different conditions.…”