MOLECULAR MICROBIAL ECOLOGY OF NITRIFICATION IN AN ACTIVATED-SLUDGE PROCESS TREATING REFINERY WASTE-WATER

The diversity of autotrophic ammonia-oxidizing bacteria (AOB) of the b -subdivision of the-class Proteobacteria was investigated in a laborat ory-scale denitrification-nitrification bioreactor (DNB) treating a sy nthetic waste stream. 16S ribosomal RNA (rRNA) gene sequences were amp lified from DNA extracted from the oxic DNB sludge. Comparative analys is of the rRNA sequences revealed considerable diversity among the AOB -like sequences. The majority of sequences recovered were related to N itrosomonas spp. but a smaller number of Nitrosospira-like sequences w ere obtained. Since different AOB may have different kinetic propertie s the high diversity of AOB, even in a simple laboratory biotreater tr eating a simple waste stream, has important implications for the opera tion of nitrifying wastewater treatment processes. (C) 1998 IAWQ. Publ ished by Elsevier Science Ltd.