Batch study results may help utilities select appropriate chloramination conditions to limit DBP formation. Batch experiments were conducted on three diverse water sources to study the formation of dissolved organic halogen (DOX), trihalomethanes (THMs), haloacetic acids (HAAs), and cyanogen halides (CNX) during chloramination. The authors used preformed chloramines to examine the effect of pH, mass ratio of chlorine to ammonia–nitrogen (Cl2 to N), and bromide concentration on disinfection by‐product (DBP) formation. Formation of specific DBPs as well as the group parameter DOX was greatest at low pH and high Cl2‐to‐N ratios and followed the general trend of decreasing with increasing pH and decreasing Cl2‐to‐N ratio. Bromide addition increased the concentration of bromine‐substituted DBPs and DOX. These experiments demonstrated that because of dihaloacetic acid formation, HAA formation is more problematic during chloramination than THM formation. Because the specific DBPs measured in this research (THMs, six HAAs, and CNX) accounted for no more than 35 percent of the DOX concentration, utilities may want to consider both specific DBPs and DOX in selecting appropriate chloramination conditions.

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 0.1-0.9 at 26 °C where, according to the IUPAC isotherm classification system, the adsorption isotherms observed exhibited Type V behavior. A Type V adsorption isotherm model recently proposed by Qi and LeVan (Q-L) was selected to model the observed adsorption behavior because it reduces to a finite, nonzero limit at low partial pressures and it describes the entire range of adsorption considered in this study. The Q-L model was applied to a polar organic adsorbate to fit HCHO adsorption isotherms for the three activated carbons. The physical and chemical characteristics of the activated carbon surfaces were characterized using nitrogen adsorption isotherms, X-ray photoelectron spectroscopy (XPS), and Boehm titrations. At low concentrations, HCHO adsorption capacity was most strongly related to the density of basic surface functional groups (SFGs), while water vapor adsorption was most strongly influenced by the density of acidic SFGs.

Several areas of the Massachusetts Military Reservation (MMR) have soils with significant levels of high explosives (HE) contamination because of a long history of training and range activities (such as open burning, open detonation, disposal, and artillery and mortar firing). Site-specific transport and attenuation mechanisms were assessed in sandy soils for three contaminants of concern: the nitramine hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and the nitroaromatics 2,4-dinitrotolune (2,4-DNT) and 2,4,6-trinitrotoluene (TNT). For all three contaminants, linear distribution coefficients (K d ) were dependent on the fraction of organic carbon in soil. The nitroaromatics sorbed much more strongly than RDX in both soils. Over 120 hours, the desorption rate of RDX from field contaminated surface soil was much slower than its sorption rate, with the desorption K d (1.5 L/kg) much higher than K d for sorption (0.37 L/kg). Desorption of 2,4-DNT was negligible over 120 hours. Thus, applying sorption-derived K d values for transport modeling may significantly overestimate the flux of explosives from MMR soils. Based on multiple component column transport * Present address: 362 H. Yamamoto et al.tests, RDX will be the most mobile of these contaminants in MMR soils. In saturated columns packed with uncontaminated soil, RDX broke through rapidly, whereas the nitroaromatics were significantly attenuated by irreversible sorption or abiotic transformations.

Cultures of Methylosinus trichosporium OB3b grown in the presence of very low concentrations of copper synthesize a soluble methane monooxygenase (sMMO) that efficiently catalyzes the oxidation of trichloroethylene and other organic pollutants. Recently, we isolated five M. trichosporium OB3b mutants that express sMMO activity when grown in the presence of elevated copper concentrations (P. A. Phelps, S. K. Agarwal,

Butane-oxidizing Arthrobacter (ATCC 27778) bacteria were shown to degrade low concentrations of methyl t-butyl ether (MTBE; range, 100 to 800 g/liter) with an apparent half-saturation concentration (K s ) of 2.14 mg/liter and a maximum substrate utilization rate (k c ) of 0.43 mg/mg of total suspended solids per day. Arthrobacter bacteria demonstrated MTBE degradation activity when grown on butane but not when grown on glucose, butanol, or tryptose phosphate broth. The presence of butane, tert-butyl alcohol, or acetylene had a negative impact on the MTBE degradation rate. Neither Methylosinus trichosporium OB3b nor Streptomyces griseus was able to cometabolize MTBE.The prevalent use of methyl t-butyl ether (MTBE) for gasoline oxygenation has led to its introduction into groundwater from spills and leaky underground storage tanks. MTBE is poorly adsorbed, chemically and biologically stable, and very soluble in water, making it very mobile and persistent in the environment. The U.S. Environmental Protection Agency has recently proposed scaling back the use of MTBE in gasoline in light of the increasing frequency with which MTBE is found as a groundwater contaminant nationwide (16; http://www.epa.gov /swerust1/mtbe/browner.pdf). Concentrations of MTBE in groundwater have been reported to range from 0.5 g/liter to Ͼ10 mg/liter. At least 20 states have established MTBE groundwater cleanup levels ranging from 20 to 400 g/liter for groundwater for potable use (http://www.epa.gov/OUST/mtbe /sumtable.htm). The U.S. Environmental Protection Agency has established a health advisory level of 20 to 40 g/liter for MTBE in drinking water (19).Efforts to develop bioremediation processes to help combat MTBE contamination of groundwater have been hampered by the recalcitrance of MTBE. The highly branched nature of MTBE resists most bacterial enzymatic attacks. Only a few pure and mixed bacterial cultures that are able to biodegrade MTBE have been identified (4,6,7,8,17).One potential MTBE biodegradation pathway involves the demethylation of MTBE to form tert-butyl alcohol (TBA) and formaldehyde (11, 17; K. L. Hurt, J. T. Wilson, and J. S. Cho, 5th Int. In Situ On-Site Bioremediation Symp., 1999), although the formation of tert-butyl formate from MTBE has also been observed (8). tert-Butyl formate is then hydrolyzed into TBA. In general, TBA is the first stable metabolite of MTBE, regardless of the type of bacterial cultures used. Hyman et al. (8) presented evidence that TBA is degraded by the same enzyme that degrades MTBE, although a soil microcosm was identified that was able to biodegrade TBA but not MTBE (M. J. Zenker, R. C. Borden, and M. A. Barlaz, 5th Int. In Situ On-Site Bioremediation Symp., 1999). TBA is biodegraded at a slower rate than MTBE (8, 17); thus, it tends to build up over time. If TBA is indeed degraded by the same enzyme that degrades MTBE, then the accumulation of TBA can have a detrimental effect on the MTBE biodegradation rate as a result of enzyme competition. Consequently, the effects of TBA on MTBE b...