Ammonia- and Nitrite-Oxidizing Bacterial Communities in a Pilot-Scale Chloraminated Drinking Water Distribution System

Abstract

Nitrification in drinking water distribution systems is a common operational problem for many utilities that use chloramines for secondary disinfection. The diversity of ammonia-oxidizing bacteria (AOB) and nitriteoxidizing bacteria (NOB) in the distribution systems of a pilot-scale chloraminated drinking water treatment system was characterized using terminal restriction fragment length polymorphism (T-RFLP) analysis and 16S rRNA gene (ribosomal DNA [rDNA]) cloning and sequencing. For ammonia oxidizers, 16S rDNA-targeted T-RFLP indicated the presence of Nitrosomonas in each of the distribution systems, with a considerably smaller peak attributable to Nitrosospira-like AOB. Sequences of AOB amplification products aligned within the Nitrosomonas oligotropha cluster and were closely related to N. oligotropha and Nitrosomonas ureae. The nitriteoxidizing communities were comprised primarily of Nitrospira, although Nitrobacter was detected in some samples. These results suggest a possible selection of AOB related to N. oligotropha and N. ureae in chloraminated systems and demonstrate the presence of NOB, indicating a biological mechanism for nitrite loss that contributes to a reduction in nitrite-associated chloramine decay.Many drinking water utilities in the United States have implemented chloramination for secondary disinfection because chloramines are less reactive than free chlorine and have been demonstrated to produce lower concentrations of disinfection by-products, such as trihalomethanes and haloacetic acids (2,23,25). However, the addition of chloramines can lead to biological instability in a drinking water distribution system by promoting the growth of nitrifying bacteria, microorganisms that oxidize ammonia to nitrite and nitrate. Chloramination introduces ammonia to the distribution system both as excess ammonia from chloramine formation and released ammonia from chloramine decay. Ammonia-oxidizing bacteria (AOB) are able to grow on the residual and released ammonia in the presence of chloramines and produce nitrite and soluble organic compounds (29, 32). The AOB cell mass and the products of AOB activity deplete the residual disinfectant concentration by exerting a chloramine demand and may sustain the growth of nitrite-oxidizing bacteria (NOB) and heterotrophs. The resulting reduction in chloramine residual and development of a microbial community in the distribution system lead to water quality deterioration and violation of drinking water regulations (49, 50).Several studies have reported on the disinfection kinetics of AOB with chloramines (4, 18, 50; P. S. Oldenburg, J. M. Regan, G. W. Harrington, and D. R. Noguera, unpublished data). In general, the results of these investigations suggest that AOB should be inactivated effectively at typical chloramine exposure times and doses. Nonetheless, nitrification episodes are common in these systems, even in the presence of high chloramine residuals (4, 36). A survey of chloraminating utilities in the United States revealed that 63% of the utilities have...

Pyrosequencing analysis of eukaryotic and bacterial communities in faucet biofilms

“…Nitrite-oxidizer relatives were mainly closely related to Nitrospira moscoviensis. Members of the family Nitrosomonadaceae and the genus Nitrospira have been found in pilot-and full-scale DWDSs as the primary nitrifiers (Lipponen et al, 2004;Regan et al, 2002Regan et al, , 2003. The number of potential nitrifiers was higher at chlorine-containing sites (WSW and STZ).…”

“…Biofilms are generally recognized as the primary source of microorganisms in drinking water distribution systems (DWDSs), and can lead to various health issues, such as protecting and supporting pathogenic microorganisms (Buswell et al, 1998), bacterial regrowth (LeChevallier et al, 1991), and depletion of disinfection agents (Regan et al, 2002). In order to understand microbial ecology in DWDS biofilms, cultivation-based and independent molecular approaches have been used to reveal biofilm communities from different locations or pipe materials (e.g.…”

Biological nitrogen removal with nitrification and denitrification via nitrite pathway

“…The first step of nitrification is the oxidation of ammonia to nitrite over hydroxylamine (NH 2 OH), involving the membranebound ammonia mono-oxygenase (AMO) and the hydroxylamine oxidoreductase (HAO), and is carried out by ammonia-oxidizing bacteria (AOB); the second group, nitrite-oxidizing bacteria (NOB), further oxidizes nitrite to nitrate. To date, any one group of bacteria that can directly oxidize ammonia to nitrate has not been found (Radajewski et al 1994;Regan et al 2002;Lipponen et al 2004). Under normal conditions, the reaction of ammonia oxidation to nitrite is a velocity-limiting step; in contrast, nitrite is oxidized rapidly to nitrate, so nitrite is seldom accumulated in nitrifying reactors.…”

Molecular analysis of long-term biofilm formation on PVC and cast iron surfaces in drinking water distribution system

“…The occurrence of biofilm may cause many public health issues, such as protecting and supporting pathogenic microorganisms (Buswell et al, 1998), bacterial regrowth (LeChevallier et al, 1991), depletion of disinfection agents (Regan et al, 2002) and microbial corrosion (Holden et al, 1995;LeChevallier et al, 1993). Thus, the DS biofilm has received more concerns.…”