Reactions of thiocarbamate, triazine and urea herbicides, RDX and benzenes on EPA Contaminant Candidate List with ozone and with hydroxyl radicals

Second-order rate constants of the direct ozone reactions (kO3,M) and the indirect OH radical reactions (kOH,M) for nine chemicals on the US EPA’s Drinking Water Contaminant Candidate List (CCL) were studied during the ozonation and ozone/hydrogen peroxide advanced oxidation process (O3/H2O2 AOP) using batch reactors. Except for the thiocarbamate herbicides (molinate and EPTC), all other CCL chemicals (linuron, diuron, prometon, RDX, 2,4-dinitrotoluene, 2,6-dinitrotoluene and nitrobenzene) show low reactivity toward ozone. The general magnitude of ozone reactivity of the CCL chemicals can be explained by their structures and the electrophilic nature of ozone reactions. The CCL chemicals (except RDX) are highly reactive toward OH radicals as demonstrated by their high kOH,M values. Ozonation at low pH, which involves mainly the direct ozone reaction, is only efficient for the removal of the thiocarbamates. Ozonation at high pH and O3/H2O2 AOP will be highly efficient for the treatment of all chemicals in this study except RDX, which shows the lowest OH radical reactivity. Removal of a contaminant does not mean complete mineralization and reaction byproducts may be a problem if they are recalcitrant and are likely to cause health concerns

Reactions of thiocarbamate, triazine and urea herbicides, RDX and benzenes on EPA Contaminant Candidate List with ozone and with hydroxyl radicals

Second-order rate constants of the direct ozone reactions (kO3,M) and the indirect OH radical reactions (kOH,M) for nine chemicals on the US EPA’s Drinking Water Contaminant Candidate List (CCL) were studied during the ozonation and ozone/hydrogen peroxide advanced oxidation process (O3/H2O2 AOP) using batch reactors. Except for the thiocarbamate herbicides (molinate and EPTC), all other CCL chemicals (linuron, diuron, prometon, RDX, 2,4-dinitrotoluene, 2,6-dinitrotoluene and nitrobenzene) show low reactivity toward ozone. The general magnitude of ozone reactivity of the CCL chemicals can be explained by their structures and the electrophilic nature of ozone reactions. The CCL chemicals (except RDX) are highly reactive toward OH radicals as demonstrated by their high kOH,M values. Ozonation at low pH, which involves mainly the direct ozone reaction, is only efficient for the removal of the thiocarbamates. Ozonation at high pH and O3/H2O2 AOP will be highly efficient for the treatment of all chemicals in this study except RDX, which shows the lowest OH radical reactivity. Removal of a contaminant does not mean complete mineralization and reaction byproducts may be a problem if they are recalcitrant and are likely to cause health concerns

Estimated Effects of Disinfection By-products on Birth Weight in a Population Served by a Single Water Utility

Research has suggested that trihalomethane exposures during pregnancy might impair fetal growth. Most epidemiologic studies, however, relied on relatively crude exposure assessment methods and did not examine racial/ethnic subgroups. During 1999–2001, vital records data were obtained for a large, racially diverse population residing in 27 Massachusetts communities that received drinking water from a single public utility. The water system was monitored weekly for trihalomethanes and, system-wide, it maintained geographically stable total trihalomethane levels during the study period. The authors examined the effects of trimester-specific and pregnancy average exposures to total trihalomethane in drinking water on term low birth weight in all singleton births. A high average total trihalomethane exposure (70 µg/liter) during the second trimester increased the risk of term low birth weight (odds ratio = 1.50, 95% confidence interval (CI): 1.07, 2.10). The estimated risk increase for Caucasians during the second trimester was 37% (95% CI: 0.80, 2.36), while for all minority women combined (i.e., African Americans, Hispanics, and Asians) it was 60% (95% CI: 1.03, 2.47). The study data suggest that high levels (70 µg/liter) of trihalomethanes experienced during the second trimester and pregnancy overall may affect fetal growth

The Use of the Odor Profile Method with an “Odor Patrol” Panel to Evaluate an Odor Impacted Site near a Landfill

A third-party-trained “Odor Patrol” program was conducted at a school that is about a one-mile distance from a landfill to clarify the odor nuisance problems from the landfill. Every 20 min from 6 to 9 a.m. on school days, the “Odor Profile Method” (OPM) was used with the landfill odor wheel to identify the odor type and intensity of each odor type. This study showed that an Odor Patrol using the OPM can accurately define odor nuisance changes over time and can be used as a method to confirm changes of odor nuisances in a field study. The Odor Patrol only found 13 data inputs of the 1000 data inputs (1.3%) for the 100-day odor monitoring with a landfill odor or trash odor that could cause odor complaints. The Odor Patrol data and the Odor Complaint data compared well. The OPM by an “Odor Patrol” could determine the contribution of the nuisance odors from 6 to 9 a.m. at the school site, about one mile away from the landfill. The study demonstrated a novel approach for odor monitoring by using the Odor Profile Method with an Odor Patrol. The OPM not only confirmed the mitigation of a landfill odor problem, but it also determined odor character, odor intensity, odor frequency and odor duration during this study period. “Landfill gas” was determined to be primarily a rotten vegetable odor with a secondary sewery/fecal odor of lower intensity, and “trash odors” were primarily a rancid and sweet odor with a secondary sewery/fecal and/or rotten vegetable odor of lower intensities generated from trash reaching the landfill. The order of intensity observed from high to low was: Trash odor (Rancid–Sweet) > Rotten vegetable > Sewery/Fecal > Rancid. Thus, trash odor is the major problematic odor from the landfill site. Quality assurance methods were used to remove local odors from the evaluation