Autotrophic growth competition between ammonia-oxidizing archaea and ammonia-oxidizing bacteria in biological activated carbon filter with nitrification potential

Biological activated carbon (BAC) filtration combined with preceding ozone oxidation has been established as a major advanced drinking water purification process. One of the most important functions of BAC is the biological oxidation of ammonia, which can serve as a precursor for odourous trichloramine. The activity of ammonia-oxidizing microorganisms in the BAC filter is related to the nitrification performance of BAC. In the present study, autotrophic growth competitions between ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) associated with BAC were evaluated by DNA stable isotope probing. When low levels of ammonium (0.14 mg N/L) were continuously supplied to BAC collected from a full-scale drinking water purification plant in Tokyo, AOA rather than AOB demonstrated higher autotrophic growth activity following 7 days of incubation. After 28 days, both AOA and AOB showed autotrophic growth. These results indicate that AOA outcompete AOB for the oxidation of low levels of ammonium in BAC filters.