Simultaneous time-resolved inorganic haloamine measurements enable analysis of disinfectant degradation kinetics and by-product formation.

We demonstrate the application of proton transfer time-of-flight mass spectrometry (PTR-TOF-MS) in monitoring the kinetics of disinfectant decay in water with a sensitivity one to three orders of magnitude greater than other analytical methods. Chemical disinfection inactivates pathogens during water treatment and prevents regrowth as water is conveyed in distribution system pipes, but it also causes formation of toxic disinfection by-products. Analytical limits have hindered kinetic models, which aid in ensuring water quality and protecting public health by predicting disinfection by-products formation.

Apparent Reactivity of Bromine in Bromochloramine Depends on Synthesis Method: Implicating Bromine Chloride and Molecular Bromine as Important Bromine Species.

The chloramination of bromide containing waters results in the formation of bromine containing haloamines: monobromamine (NHBr), dibromamine (NHBr), and bromochloramine (NHBrCl). Many studies have directly shown that bromamines are more reactive than chloramines in oxidation and substitution reactions with organic water constituents because the bromine atom in oxidants is more labile than the chlorine atom. However, similar studies have not been performed with NHBrCl.

Role of Carbonate Species on General Acid Catalysis of Bromide Oxidation by Hypochlorous Acid (HOCl) and Oxidation by Molecular Chlorine (Cl).

Kinetic models for disinfectant decay and disinfection byproduct (DBP) formation are necessary for predicting water quality from the treatment plant to the tap. A kinetic model for conditions relevant to chloramine disinfection of drinking water (pH 6-9 and carbonate-buffered) was developed to simulate incomplete bromide (Br) oxidation during short prechlorination periods because it is the first step in a complex system of reactions that leads to disinfectant loss and DBP formation. Hypochlorous acid and molecular chlorine were the free chlorine species relevant to Br oxidation, and Cl hydrolysis and formation reactions were necessary to accurately simulate Cl concentrations instead of assuming equilibrium.

Bromamine Decomposition Revisited: A Holistic Approach for Analyzing Acid and Base Catalysis Kinetics.

Chloramine chemistry is complex, with a variety of reactions occurring in series and parallel and many that are acid or base catalyzed, resulting in numerous rate constants. Bromide presence increases system complexity even further with possible bromamine and bromochloramine formation. Therefore, techniques for parameter estimation must address this complexity through thoughtful experimental design and robust data analysis approaches.

Monochloramine Cometabolism by Mixed-Culture Nitrifiers under Drinking Water Conditions.

Chloramines are the second most used secondary disinfectant by United States water utilities. However, chloramination may promote nitrifying bacteria. Recently, monochloramine cometabolism by the pure culture ammonia-oxidizing bacteria, Nitrosomonas europaea, was shown to increase monochloramine demand.

Hydroxylamine addition impact to Nitrosomonas europaea activity in the presence of monochloramine.

In drinking water, monochloramine may promote ammonia–oxidizing bacteria (AOB) growth because of concurrent ammonia presence. AOB use (i) ammonia monooxygenase for biological ammonia oxidation to hydroxylamine and (ii) hydroxylamine oxidoreductase for biological hydroxylamine oxidation to nitrite. In addition, monochloramine and hydroxylamine abiotically react, providing AOB a potential benefit by removing the disinfectant (monochloramine) and releasing growth substrate (ammonia).

A proposed abiotic reaction scheme for hydroxylamine and monochloramine under chloramination relevant drinking water conditions.

Drinking water monochloramine (NH2Cl) use may promote ammonia-oxidizing bacteria (AOB). AOB use (i) ammonia monooxygenase for biological ammonia (NH3) oxidation to hydroxylamine (NH2OH) and (ii) hydroxylamine oxidoreductase for NH2OH oxidation to nitrite. NH2Cl and NH2OH may react, providing AOB potential benefits and detriments.

A coupled sensor-spectrophotometric device for continuous measurement of formaldehyde in indoor environments.

Despite long-standing awareness of adverse health effects associated with chronic human exposure to formaldehyde, this hazardous air pollutant remains a challenge to measure in indoor environments. Traditional analytical techniques evaluate formaldehyde concentrations over several hours to several days in a single location in a residence, making it difficult to characterize daily temporal and spatial variation in human exposure to formaldehyde. There is a need for portable, easy-to-use devices that are specific and sensitive to gas-phase formaldehyde over short sampling periods so that dynamic processes governing formaldehyde fate, transport, and potential remediation in indoor environments may be studied more effectively.

Monochloramine cometabolism by Nitrosomonas europaea under drinking water conditions.

Chloramine is widely used in United States drinking water systems as a secondary disinfectant, which may promote the growth of nitrifying bacteria because ammonia is present. At the onset of nitrification, both nitrifying bacteria and their products exert a monochloramine demand, decreasing the residual disinfectant concentration in water distribution systems. This work investigated another potentially significant mechanism for residual disinfectant loss: monochloramine cometabolism by ammonia-oxidizing bacteria (AOB).

Relative importance of nitrite oxidation by hypochlorous acid under chloramination conditions.

Nitrification can occur in water distribution systems where chloramines are used as the disinfectant. The resulting product, nitrite, can be oxidized by monochloramine and hypochlorous acid (HOCl), potentially leading to rapid monochloramine loss. This research characterizes the importance of the HOCl reaction, which has typically been ignored because of HOCl's low concentration.

Autohydrogenotrophic perchlorate reduction kinetics of a microbial consortium in the presence and absence of nitrate.

This is the first study to model the effects of nitrate on autohydrogenotrophic perchlorate biokinetics. Batch experiments demonstrated that the presence of nitrate significantly inhibited perchlorate degradation by a hydrogen-oxidizing, perchlorate-reducing microbial consortium. However, the consortium was capable of significant perchlorate reduction while the bulk of the nitrate was still present.

Gas-phase formaldehyde adsorption isotherm studies on activated carbon: correlations of adsorption capacity to surface functional group density.

Formaldehyde (HCHO) adsorption isotherms were developed for the first time on three activated carbons representing one activated carbon fiber (ACF) cloth, one all-purpose granular activated carbon (GAC), and one GAC commercially promoted for gas-phase HCHO removal. The three activated carbons were evaluated for HCHO removal in the low-ppm(v) range and for water vapor adsorption from relative pressures of 0.1-0.

Ammonia-oxidizing bacteria in biofilters removing trihalomethanes are related to Nitrosomonas oligotropha.

Ammonia-oxidizing bacteria (AOB) in nitrifying biofilters degrading four regulated trihalomethanes-trichloromethane, bromodichloromethane, dibromochloromethane, and tribromomethane-were related to Nitrosomonas oligotropha. N. oligotropha is associated with chloraminated drinking water systems, and its presence in the biofilters might indicate that trihalomethane tolerance is another reason that this bacterium is dominant in chloraminated systems.

Performance and biofilm activity of nitrifying biofilters removing trihalomethanes.

Nitrifying biofilters seeded with three different mixed-culture sources removed trichloromethane (TCM) and dibromochloromethane (DBCM) with removals reaching 18% for TCM and 75% for DBCM. In addition, resuspended biofilm removed TCM, bromodichloromethane (BDCM), DBCM, and tribromomethane (TBM) in backwash batch kinetic tests, demonstrating that the biofilters contained organisms capable of biotransforming the four regulated trihalomethanes (THMs) commonly found in treated drinking water. Upon the initial and subsequent increased TCM addition, total ammonia nitrogen (TOTNH(3)) removal decreased and then reestablished, indicating an adjustment by the biofilm bacteria.

Effect of softening precipitate composition and surface characteristics on natural organic matter adsorption.

Natural organic matter (NOM) removal during water softening is thought to occur through adsorption onto or coprecipitation with calcium and magnesium solids. However, details of precipitate composition and surface chemistry and subsequent interactions with NOM are relatively unknown. In this study, zeta potentiometry analyses of precipitates formed from inorganic solutions under varying conditions (e.

Modeling of trihalomethane cometabolism in nitrifying biofilters.

The computer program AQUASIM was used to model biofilter experiments seeded with Lake Austin, Texas mixed-culture nitrifiers. These biofilters degraded four trihalomethanes (THMs) (trichloromethane (TCM) or chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), tribromomethane (TBM) or bromoform) commonly found in treated drinking water. Apparent steady-state data from the biofilter experiments and supporting batch experiments were used to estimate kinetic parameters for TCM, DBCM and ammonia degradation.

Cometabolism of trihalomethanes by mixed culture nitrifiers.

Three mixed-culture nitrifier sources degraded low concentrations (25-450 microg/L) of four trihalomethanes (THMs) (trichloromethane (TCM) or chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), tribromomethane (TBM) or bromoform) commonly found in treated drinking water. Individual THM rate constants (k1THM) increased with increasing THM bromine-substitution with TBM>DBCM>BDCM>TCM and were comparable to previous studies with the pure culture nitrifier, Nitrosomonas europaea. A decrease in temperature resulted in a decrease in both ammonia and THM degradation rates with ammonia rates affected to a greater extent than THM degradation rates.

Impact of natural organic matter on monochloramine reduction by granular activated carbon: the role of porosity and electrostatic surface properties.

Steady-state monochloramine reduction in fixed-bed reactors (FBRs) was quantified on five types of granular activated carbon (GAC) using two background waters-one natural source water (LAW) containing 2.5-3.5 mg/L organic carbon and one synthetic organic-free water (NW).

Enhanced desorption of RDX from granular activated carbon.

Several methods (cosolvents, surfactants, and cyclodextrins) were compared for improving desorption of a high explosive, RDX, from granular activated carbon (GAC). In batch desorption tests, 3% of the adsorbed RDX (initially 71.1 mg RDX/g GAC) was desorbed by water over 11 days, compared to 92.

Dissolution kinetics of high explosives particles in a saturated sandy soil.

Solid phase high explosive (HE) residues from munitions detonation may be a persistent source of soil and groundwater contamination at military training ranges. Saturated soil column tests were conducted to observe the dissolution behavior of individual components (RDX, HMX, and TNT) from two HE formulations (Comp B and C4). HE particles dissolved readily, with higher velocities yielding higher dissolution rates, higher mass transfer coefficients, and lower effluent concentrations.

Cometabolism of trihalomethanes by Nitrosomonas europaea.

The ammonia-oxidizing bacterium Nitrosomonas europaea (ATCC 19718) was shown to degrade low concentrations (50 to 800 mug/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 (k1THM) increased with increasing THM bromine substitution, with TBM > DBCM > BDCM > TCM (0.23, 0.

Scale-up considerations for a hollow-fiber-membrane bioreactor treating trichloroethylene-contaminated water.

Scale-up of a hollow-fiber-membrane (HFM) bioreactor treating trichloroethylene- (TCE-) contaminated water via co-metabolism with the methanotroph Methylosinus trichosporium OB3b PP358 was investigated through cost comparisons, bioreactor experiments, and mathematical modeling. Cost comparisons, based on a hypothetical treatment scenario of 568-L/min (150-gpm) flowrate with an influent TCE concentration of 100 microg/L, resulted in a configuration of treatment trains with two HFM modules in series and an overall annual cost of US dollar 0.36/m3 treated.

Fate of biodegradable dissolved organic carbon produced by ozonation on biological activated carbon.

The adsorption and desorption characteristics of BDOC produced by ozonation and the replacement of BDOC by non-BDOC on BAC was studied. The fate of BDOC produced by ozonation in the BAC column was also evaluated by comparative experiment between the BAC supplied with the mixture of BDOC and non-BDOC and the BAC supplied only with non-BDOC. Fulvic acids extracted from two river sediments and one forest soil were used.