Nitrite-oxidizing bacteria guild ecology associated with nitrification failure in a continuous-flow reactor

Charles W. Knapp, David W. Graham

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

Nitrification is an important process for nitrogen removal in many wastewater treatment plants, which requires the mutualistic oxidation of ammonia to nitrate by ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). However, this process can be quite unpredictable because both guilds are conditionally sensitive to small changes in operating conditions. Here, dynamics are examined within the NOB guild in two parallel chemostats operated at low and high dilution rates (0.10 and 0.83 day(-1), respectively) during periods of varying nitrification performance. NOB and AOB guild abundances and nitrogen-oxidation efficiency were relatively constant over time in the 0.10 day(-1) reactor; however, the 0.83 day(-1) reactor had two major disturbance episodes that caused destabilization of the NOB guild, which ultimately led to nitrification failure. The first episode caused the extinction of Nitrospira spp. from the system, resulting in chronic incomplete ammonia oxidation and nitrite accumulation. The second episode caused complete loss of nitrification activity, likely resulting from metal toxicity and the previous extinction of Nitrospira spp. from the system. These results exemplify the types of changes that can occur within the NOB guild that result in process impairment or failure, and provide one possible explanation for why nitrification is often unstable at higher dilution rates.
Original languageEnglish
Pages (from-to)195-201
Number of pages6
JournalFEMS Microbiology Ecology
Volume62
Issue number2
Publication statusPublished - Nov 2007

Keywords

  • nitrospira
  • nitrobacter
  • nitrite oxidation
  • real-time PCR
  • bioreactor
  • nitrification

Cite this