Ammonia oxidizing bacteria community in activated sludge monitored by denaturing gradient gel electrophoresis (DGGE)

Abstract

Biological treatment based on activated sludge is efficient in municipal wastewater treatment. The removal of nitrogen compounds is crucial for sewage purification. Due to the fact that ammonia is toxic for a water environment and causes eutrophication, ammonia oxidation is of the utmost importance in wastewater treatment. Observing the changeability of ammonia oxidizing bacteria (AOB) and identifying their most abundant species can be helpful in the optimization of wastewater treatment. In this study we used denaturing gradient gel electrophoresis (DGGE), combined with cloning and sequencing of 16S rRNA and AmoA gene fragments in order to estimate AOB biodiversity and temporal community changes. Activated sludge samples were collected from the municipal WWTP in Gliwice (Poland) at 2-week intervals. Ammonia concentration in the influent during the experiment was 30.2-57.6 mg N-NH₄⁺/L. The research revealed a high diversity of uncultured bacteria. It is suspected that these bacteria could be involved in the nitrification, which points to the fact that these bacteria might be efficient in the process. However such a situation is not confirmed and it requires further research. The appearance of Ferribacterium-like bacteria together with Nitrosomonas sp. as the most abundant bacteria was found.