Studies on the Growth of Anaerobic Ammonium Oxidizing Bacteria and the Start-Up of Moving Bed Biofilm Reactors

Abstract

The slow growth of anaerobic ammonium oxidization (anammox) bacteria remains a challenge for the implementation of anammox. The goal of this study is to optimize anammox growth parameters in order to achieve a good sludge retention in the anammox process. A growth assay was developed, calculated from the rate of nitrogen gas production according to the microbial growth equation. The optimal levels of trace elements, ammonium and bicarbonate were investigated. The results showed that trace elements with EDTA were necessary for the growth of anammox, while EDTA itself was harmful for anammox bacteria. Ammonium concentrations of 400 mg N•L-1 decreased the growth of anammox by 40%. Higher ammonium concentrations completely terminated the growth of the biomass. Bicarbonate concentration of 100 mg•L-1 was essential in order for anammox bacteria to grow well, and 500 mg•L-1 was optimal. However, higher concentration of bicarbonate had negative impacts, likely due to high salinity. The growth of anammox bacteria rather than anammox activity tended to be more sensitive to the stress of their environments, but further evidence is needed. Overall, growth parameter optimization is a promising approach for better implementation of anammox process.