Monochloramine Disinfection Kinetics of Nitrosomonas europaea by Propidium Monoazide Quantitative PCR and Live/Dead BacLight Methods

Abstract

Monochloramine disinfection kinetics were determined for the pure-culture ammonia-oxidizing bacterium Nitrosomonas europaea (ATCC 19718) by two culture-independent methods, namely, Live/Dead BacLight (LD) and propidium monoazide quantitative PCR (PMA-qPCR). Both methods were first verified with mixtures of heat-killed (nonviable) and non-heat-killed (viable) cells before a series of batch disinfection experiments with stationary-phase cultures (batch grown for 7 days) at pH 8.0, 25°C, and 5, 10, and 20 mg Cl 2 /liter monochloramine. Two data sets were generated based on the viability method used, either (i) LD or (ii) PMA-qPCR. These two data sets were used to estimate kinetic parameters for the delayed Chick-Watson disinfection model through a Bayesian analysis implemented in WinBUGS. This analysis provided parameter estimates of 490 mg Cl 2 -min/liter for the lag coefficient (b) and 1.6 ؋ 10 ؊3 to 4.0 ؋ 10 ؊3 liter/mg Cl 2 -min for the Chick-Watson disinfection rate constant (k). While estimates of b were similar for both data sets, the LD data set resulted in a greater k estimate than that obtained with the PMA-qPCR data set, implying that the PMA-qPCR viability measure was more conservative than LD. For N. europaea, the lag phase was not previously reported for culture-independent methods and may have implications for nitrification in drinking water distribution systems. This is the first published application of a PMA-qPCR method for disinfection kinetic model parameter estimation as well as its application to N. europaea or monochloramine. Ultimately, this PMA-qPCR method will allow evaluation of monochloramine disinfection kinetics for mixed-culture bacteria in drinking water distribution systems.As a result of stage 1 and stage 2 disinfectant and disinfection by-product rules, chloramination for secondary disinfection in the United States is predicted to increase to 57% of all surface and 7% of all groundwater treatment systems (49). A recent survey reported that 30% of the respondents currently chloraminate to maintain distribution system residual, and other recent surveys suggest that between 8 and 12% of drinking water utilities are contemplating a future switch to chloramination (3, 43).Although chloramines are considered weaker disinfectants than chlorine for suspended bacteria, chloramines are perceived as more effective disinfectants for a biofilm (25, 53). As a result of their lower reactivity, chloramines are believed to penetrate a biofilm further and thereby to more effectively disinfect biofilm bacteria with depth than chlorine (53).Chloramination comes with the risk of distribution system nitrification (2, 21, 22). Based on utility surveys, 30 to 63% of utilities practicing chloramination for secondary disinfection experience nitrification episodes (3,21,43,54). Nitrification in drinking water distribution systems is undesirable and may result in water quality degradation (e.g., disinfectant depletion, coliform occurrences, or nitrite/nitrate formation) and subsequent noncompliance with exis...

Survival of Host-Associated Bacteroidales Cells and Their Relationship with Enterococcus spp., Campylobacter jejuni, Salmonella enterica Serovar Typhimurium, and Adenovirus in Freshwater Microcosms as Measured by Propidium Monoazide-Quantitative PCR

“…However, traditional fecal indicators to monitor recreational water quality are often not associated with health risks in ambient water where nonpoint sources are dominant fecal contributors, and these results suggest a need for alternative indicators of water quality (47). Furthermore, FIB are inadequate to identify the source of fecal pollution because they are observed in both warm-and cold-blooded animal feces (30,35).…”

Determination of the Effects of Medium Composition on the Monochloramine Disinfection Kinetics of Nitrosomonas europaea by the Propidium Monoazide Quantitative PCR and Live/Dead BacLight Methods

“…As a first step in exploring possible medium effects on disinfection kinetics, as determined using two culture-independent methods, Live/Dead BacLight (LD) and propidium monoazide quantitative PCR (PMA-qPCR), batch disinfection experiments were conducted with three different phosphate buffer media (PB) (1, 10, and 50 mM Na 2 HPO 4 , pH 8.0) to compare our results with previous research that used 10 mM phosphate-buffered saline (PBS) (10 mM Na 2 HPO 4 and 130 mM NaCl, pH 8) (27) and to serve as a baseline for future experiments with finished drinking water. Ten millimolar PB, 50 mM PB, and 10 mM PBS represent media commonly used in disinfection experiments (see, e.g., references 18, 20, and 22).…”

“…If the disinfection mechanism is general acid catalyzed or related to products from monochloramine disproportionation (e.g., dichloramine), the disinfection rate may also increase with increasing phosphate concentration. The experimental results were interpreted based on medium differences in ionic strength and phosphate concentration.Nitrosomonas europaea (ATCC 19718; ATCC, Manassas, VA) bacteria were batch grown (25 to 28°C) to stationary phase (7 days) and then harvested and washed in the same medium used in the batch disinfection experiments as described previously (27). N. europaea was studied because of its use in previous monochloramine disinfection research (27).…”

“…Nitrosomonas europaea (ATCC 19718; ATCC, Manassas, VA) bacteria were batch grown (25 to 28°C) to stationary phase (7 days) and then harvested and washed in the same medium used in the batch disinfection experiments as described previously (27). N. europaea was studied because of its use in previous monochloramine disinfection research (27).…”

The Effect of Biofilm Growth on Wall Shear Stress in Drinking Water PVC Pipes

“…If the flow becomes turbulent, microorganisms are transported by eddies in the flow. Studies have also shown that the type of disinfectant [1,[10][11][12][13], pipe material [10,[14][15][16], hydrodynamics [6,9,12,14,17], availability of nutrients [1,11,[18][19][20][21][22][23][24], and microbial manifestation in the WDS can lead to evident changes in microbial activities. Biofilm development is a result of pioneer attachment, subsequent attachment, and growth of EPS -an essential substance in keeping biofilm organisms together that provides protection against stress, predation, and exposure to a hostile environment.…”