3 research outputs found
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 â–¿
Various medium compositions (phosphate, 1 to 50 mM; ionic strength, 2.8 to 150 meq/liter) significantly affected Nitrosomonas europaea monochloramine disinfection kinetics, as determined by the Live/Dead BacLight (LD) and propidium monoazide quantitative PCR (PMA-qPCR) methods (lag coefficient, 37 to 490 [LD] and 91 to 490 [PMA-qPCR] mg·min/liter; Chick-Watson rate constant, 4.0 × 10−3 to 9.3 × 10−3 [LD] and 1.6 × 10−3 to 9.6 × 10−3 [PMA-qPCR] liter/mg·min). Two competing effects may account for the variation in disinfection kinetic parameters: (i) increasing kinetics (disinfection rate constant [k] increased, lag coefficient [b] decreased) with increasing phosphate concentration and (ii) decreasing kinetics (k decreased, b increased) with increasing ionic strength. The results support development of a standard medium for evaluating disinfection kinetics in drinking water
Biofilm Community Dynamics in Bench-Scale Annular Reactors Simulating Arrestment of Chloraminated Drinking Water Nitrification
Annular
reactors (ARs) were used to study biofilm community succession and
provide ecological insight during nitrification arrestment through
simultaneously increasing monochloramine (NH<sub>2</sub>Cl) and chlorine
to nitrogen mass ratios, resulting in four operational periods (I–IV).
Analysis of 16S rRNA-encoding gene sequence reads (454-pyrosequencing)
examined viable and total biofilm communities and found total samples
were representative of the underlying viable community. Bacterial
community structure showed dynamic changes corresponding with AR operational
parameters. Period I (complete nitrification and no NH<sub>2</sub>Cl residual) was dominated by <i>Bradyrhizobium</i> (total
cumulative distribution: 38%), while environmental <i>Legionella</i>-like phylotypes peaked (19%) during Period II (complete nitrification
and minimal NH<sub>2</sub>Cl residual). <i>Nitrospira moscoviensis</i> (nitrite-oxidizing bacteria) was detected in early periods (2%)
but decreased to <0.02% in later periods, corresponding to nitrite
accumulation. <i>Methylobacterium</i> (19%) and members
of <i>Nitrosomonadaceae</i> (42%) dominated Period III (complete
ammonia and partial nitrite oxidation and low NH<sub>2</sub>Cl residual).
An increase in <i>Afipia</i> (haloacetic acid-degrading
bacteria) relative abundance (<2% to 42%) occurred during Period
IV (minimal nitrification and moderate to high NH<sub>2</sub>Cl residual).
Microbial community and operational data provided no evidence of taxa-time
relationship, but rapid community transitions indicated that the system
had experienced ecological regime shifts to alternative stable states