Modelling of microbial populations in biofilm reactors for nitrogen removal from wastewater

Subtitle:Modelleren van microbiële populaties in biofilmreactoren voor stikstof-verwijdering uit afvalwater

The removal of nitrogen from wastewater is essential to prevent algae blooms and fish death in aquatic systems. Conventional biological nitrogen removal is based on nitrification, i.e., the conversion of ammonium to nitrite by ammonia-oxidizing bacteria (nitritation) and nitrite to nitrate by nitrite-oxidizing bacteria (nitratation). Biofilm reactors, in which the bacteria grow in a microbial layer attached to a carrier, are typically applied to prevent the slow-growing nitrifying bacteria from being washed out of the reactor. In this doctoral research, the influence of microbial competition and coexistence, besides operational conditions, on biological nitrogen removal in biofilm reactors was studied through mathematical modelling and simulation. Microbial diversity and competition were incorporated in dynamic biofilm models considering spatial gradients perpendicular to the carrier. Insights were gained on the influence of (1) microbial diversity on steady state and dynamic behaviour of nitrifying biofilms and (2) microbial characteristics, process conditions, and biofilm characteristics on microbial competition. It was demonstrated that species performing the same function typified by a trade-off between their growth rate and affinity were able to coexist in the biofilm at steady state due to the diffusional substrate gradients creating different niches in the biofilm.

ISBN:9789059898424

Publication year:2015

Accessibility:Open