Influence of operating conditions on population dynamics in nitrifying biofilms

TURBO N(R) is a circulating-bed biofilm reactor that provides stable operat ion and high N removal for a wide range of N and BOD loadings. This paper d escribes the influence of operating conditions on biofilm composition and p opulation dynamics when the TURBO N(R) is operated to achieve tertiary nitr ification, simultaneous carbon and ammonia oxidation and total nitrogen rem oval when coupled with a pre denitrification fixed floating bed reactor. In situ specific nitrification rates and respiration tests showed that ammoni um and nitrite oxidizers became less active in the biofilm once oxidation o f influent BOD became important. Analyses of community structure with oligo nucleotide probes targeted to the 16S rRNA showed the same general trends f or nitrifiers, bur also suggested shifts in the makeup of the ammonium and nitrite oxidizers that could not be detected with respirometry or specific nitrification rates. (C) 1999 IAWQ Published by Elsevier Science Ltd. All r ights reserved.