Systems and processes for early detection of biological ammonia oxidation in water using fluorometry

This invention relates generally to a system and process for early detection of biological ammonia oxidation in water utilizing a fluorescence-based sensor and process. Various embodiments are configured to read increases in a fluorescence excitation-emission wavelength pair that is responsive to a period of time (days to weeks or even longer) prior to the onset of biological ammonia oxidation, which is considered to be a nitrification event. Fluorescence excitation/emission pairs that have proven to be reliable include a fluorescence excitation wavelength of about 230 nm and an emission wavelength of about 345 nm and an excitation wavelength of 325 and an emission wavelength of 470. The system and process enable drinking water utilities to improve management of its distribution systems and facilitate earlier corrective actions, resulting is less loss of treated water through flushing and other tangible benefits

Cometabolism of Trihalomethanes by Nitrosomonas europaea

The ammonia-oxidizing bacterium Nitrosomonas europaea (ATCC 19718) was shown to degrade low concentrations (50 to 800 μg/liter) of the four trihalomethanes (trichloromethane [TCM], or chloroform; bromodichloromethane [BDCM]; dibromochloromethane [DBCM]; and tribromomethane [TBM], or bromoform) commonly found in treated drinking water. Individual trihalomethane (THM) rate constants ([Formula: see text]) increased with increasing THM bromine substitution, with TBM > DBCM > BDCM > TCM (0.23, 0.20, 0.15, and 0.10 liters/mg/day, respectively). Degradation kinetics were best described by a reductant model that accounted for two limiting reactants, THMs and ammonia-nitrogen (NH(3)-N). A decrease in the temperature resulted in a decrease in both ammonia and THM degradation rates with ammonia rates affected to a greater extent than THM degradation rates. Similarly to the THM degradation rates, product toxicity, measured by transformation capacity (T(c)), increased with increasing THM bromine substitution. Because both the rate constants and product toxicities increase with increasing THM bromine substitution, a water's THM speciation will be an important consideration for process implementation during drinking water treatment. Even though a given water sample may be kinetically favored based on THM speciation, the resulting THM product toxicity may not allow stable treatment process performance

Three-Dimensional Free Chlorine And Monochloramine Biofilm Penetration: Correlating Penetration With Biofilm Activity And Viability

Disinfectant biofilm penetration and its effect on biofilm aerobic activity and viability are still unclear. In this study, free chlorine and monochloramine were applied until full biofilm penetration occurred, and their effects on biofilm aerobic activity and viability were investigated in three dimensions throughout the entire biofilm depth, extending previous work where viability analysis was limited to the upper biofilm (50 μm depth), free chlorine penetration did not reach completion, and only one-dimensional (depth) profiles were obtained. The free chlorine and monochloramine biofilm concentration profiles were correlated spatially and temporally with aerobic microbial activity and cell-membrane integrity based viability using a combination of (1) microelectrode measurements for disinfectant penetration and (2) LIVE/DEAD BacLight staining, cryo-cross-sectioning, and confocal micrographs analysis for viability measurements throughout the entire biofilm depth. Compared to monochloramine, free chlorine penetration (1) was slower, (2) led to a greater decrease in biofilm thickness from sloughing, and (3) corresponded directly with a viability decrease. In addition, biofilm heterogeneity led to minor differences in either disinfectant\u27s biofilm penetration, and prior biofilm exposure to monochloramine provided little impact to subsequent free chlorine biofilm penetration

Amperometric Carbon Fiber Nitrite Microsensor For In Situ Biofilm Monitoring

A highly selective needle type solid state amperometric nitrite microsensor based on direct nitrite oxidation on carbon fiber was developed using a simplified fabrication method. The microsensor\u27s tip diameter was approximately 7 μm (14 μm spatial resolution). At an applied potential of +1.2 V vs. Ag/AgCl, the microsensor exhibited a linear nitrite response from 0 to 25 mg N L-1, a 0.02 mg N L-1 (1.3 μM) limit of detection, and a fast response (\u3c5 s). There was minimal interference with less than 3% of electrode response changes from major chemicals of interest in drinking water and wastewater systems [oxygen, ammonium, monochloramine, nitrate, sodium bicarbonate (alkalinity), chloride, sulfate, and acetate]. Hydrogen ion (pH) affected nitrite measurement by shifting the baseline response, translating into an approximate change of 0.24 mg N L-1 nitrite per 1 pH unit change. Depending on the conditions (e.g., pH, alkalinity, nitrite concentration), pH may need to be taken into account during nitrite measurement. The developed carbon fiber nitrite microsensor successfully measured nitrite in a nitrifying biofilm and is applicable for in situ analysis in other micro-environments (e.g., microbial mats and sediments)

Monochloramine-Sensitive Amperometric Microelectrode: Optimization Of Gold, Platinum, And Carbon Fiber Sensing Materials For Removal Of Dissolved Oxygen Interference

Monochloramine electrochemical determination in an aqueous system using newly fabricated gold and platinum microelectrodes was investigated to optimize sensor operation and to eliminate dissolved oxygen (DO) interference during monochloramine measurements. Carbon fiber microelectrodes were also compared for reference purposes. Gold and platinum microelectrodes exhibited no oxygen interference during monochloramine measurement and provided a linear relationship when operated at +150 and +300 mV vs. Ag/AgCl over a wide concentration range (0–4.2 mg Cl2/L), respectively. The carbon fiber microelectrode with 7-μm tip diameter was not sufficiently sensitive to monochloramine concentrations for detailed study. The baseline signal of both gold and platinum microelectrodes (i.e., signal without monochloramine) was near zero. With the same geometric tip diameter (20-μm tip diameter), gold microelectrodes resulted in better amperometric electrode response to monochloramine than platinum microelectrodes; gold microelectrodes had a higher sensitivity (52 ± 0.7 vs. 18 ± 0.07 pA/[mg Cl2/L]) and lower detection limit (0.12 ± 0.013 vs. 0.33 ± 0.10 mg Cl2/L), resulting in gold as the preferred microelectrode material. The developed gold microelectrode will allow accurate in situ monochloramine determination in biofilm while eliminating the confounding effects of oxygen interference

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 ▿

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

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

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 Cl2/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 Cl2-min/liter for the lag coefficient (b) and 1.6 × 10−3 to 4.0 × 10−3 liter/mg Cl2-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

Three-Dimensional Free Chlorine and Monochloramine Biofilm Penetration: Correlating Penetration with Biofilm Activity and Viability

Disinfectant biofilm penetration and its effect on biofilm aerobic activity and viability are still unclear. In this study, free chlorine and monochloramine were applied until full biofilm penetration occurred, and their effects on biofilm aerobic activity and viability were investigated in three dimensions throughout the entire biofilm depth, extending previous work where viability analysis was limited to the upper biofilm (50 μm depth), free chlorine penetration did not reach completion, and only one-dimensional (depth) profiles were obtained. The free chlorine and monochloramine biofilm concentration profiles were correlated spatially and temporally with aerobic microbial activity and cell-membrane integrity based viability using a combination of (1) microelectrode measurements for disinfectant penetration and (2) LIVE/DEAD BacLight staining, cryo-cross-sectioning, and confocal micrographs analysis for viability measurements throughout the entire biofilm depth. Compared to monochloramine, free chlorine penetration (1) was slower, (2) led to a greater decrease in biofilm thickness from sloughing, and (3) corresponded directly with a viability decrease. In addition, biofilm heterogeneity led to minor differences in either disinfectant’s biofilm penetration, and prior biofilm exposure to monochloramine provided little impact to subsequent free chlorine biofilm penetration