Anaerobic degradation of pyrrolidine and piperidine coupled with nitrate reduction

Biodegradability of secondary amines (pyrrolidine, piperidine, piperazine, morpholine, and thiomorpholine) under anaerobic conditions was examined in microbial consortia from six different environmental sites. The consortia degraded pyrrolidine and piperidine under denitrifying conditions. Enrichment cultures were established by repeatedly sub-culturing the consortia on pyrrolidine or piperidine in the presence of nitrate. The enrichments strictly required nitrate for the anaerobic degradation and utilized pyrrolidine or piperidine as a carbon, nitrogen, and energy source for their anaerobic growths. The anaerobic degradation of pyrrolidine and piperidine reduced nitrate to nitrogen gas, indicating that these anaerobic degradations were coupled with a respiratory nitrate reduction.     

Effect of soil layering on NAPL removal behavior in soil-heated vapor extraction

Soil heating has been proposed as a method to enhance the vapor extraction of NAPLs from contaminated soils. Three-dimensional fluid flow and heat transfer simulations have been performed for soil-heated vapor extraction to determine the transient system performance for a hypothetical configuration. Soil layering has been considered in evaluation of the initial non-aqueous phase liquid (NAPL) distribution and in evaporation and transport to the vapor extraction location. Results from this layered model are compared with results for a homogeneous system with an initially uniform NAPL, indicating the influence of layering, the initial NAPL distribution, the type of NAPL, and the possibility of enhanced vapor diffusion. Not only is the NAPL removal time reduced significantly with the addition of heat, but the uncertainty in the removal time owing to a number of difficult to characterize in situ factors, such as layering and the initial NAPL distribution, is much less than for standard soil vapor extraction without heating, owing to the rise in temperature and increase in NAPL vapor pressure with time.     

Dioxins and furans in emissions from medical waste incinerators

Dioxins and furans were detected in emissions from eight medical waste incinerators tested in California. Total uncontrolled emissions ranged from 363 to 11, 811 nanograms per dry standard cubic meter. The most effective of three wet scrubbers achieved an emissions control efficiency of 95 percent for total PCDD and PCDF. A baghouse was less than 30 percent efficient in removing PCDD and PCDF from the incinerator emissions.     

Modular containers for microcosm and process model studies on the fate and effects of aquatic contaminants

Container modules are described for the laboratory simulation of selected processes and ecosystems that are representative of lentic environments. Emphasis is placed on design features permitting mass balance accountability of contaminant residues and procedural cautions required for the proper use of the described systems in environmental simulations. Experiments on the efficiency of container modules for microbial mineralization studies were conducted using ¹⁴CNaHCO₃, and acidification resulted in a ¹⁴CCO₂ recovery of $\text{97.3 ± 4.7\% (}\text{x}\text{?}\text{± SD}\text{)}$. The trapping efficiency of pesticides volatilized from water and glass surfaces was investigated using the same module and the mean recoveries of ¹⁴C-fonofos and ¹⁴C-trifluralin were 114.2 ± 3.2% and 95.2 ± 3.5%, respectively. The mass balance capabilities of the system was also demonstrated for extended microcosm exposures to ¹⁴C-trifluralin.     

Exposure to polychlorinated biphenyls from an overheated transformer

A Polychlorinated Biphenyl (PCB) containing transformer released approximately 50 gallons of askarel oil. No polychlorinated dibenzofurans (PCDF) or polychlorinated dibenzodioxins (PCDD) were detected in a sample of the askarel (analytical limit of detection of 40 parts per billion per isomer group). Skin irritation, unusual tiredness, and headaches occurred in approximately 20% of the individuals at the scene of the incident. Serum PCB levels, and mean values for blood and urine tests were within normal ranges.     

Environmentally friendly production of thiobencarb (Bolero)

S-Alkyl thiocarbamates are commercially available and widely used for their herbicidal properties. Despite the numerous methods for synthesizing these compounds, most employ toxic reagents that are harmful to the environment. Within we report a novel efficient one-pot process for the formation of thiobencarb employing readily available reagents. This method makes use of a trichloroacetyl chloride adduct and requires no complex starting materials. Furthermore, this process is efficient, proceeds in high yields, and utilizes several recyclable reagents.     

Comparative assessment of municipal wastewater disposal methods in southeast Florida.

A comparative assessment of the risks of three effluent disposal alternatives currently available to wastewater utilities in Southeast Florida is presented in this paper. The alternatives are: deep well injection and ocean outfalls following secondary treatment, and surface water (canal) discharges following secondary wastewater treatment, filtration and nutrient removal. Water quality data, relative to disposal of wastewater treatment plant effluent were gathered, along with water quality data on the receiving waters, from utilities. Comparisons and conclusions regarding potential health concerns associated with the three disposal alternatives are presented. The results indicated that health risks associated with deep wells were generally lower than those of the other two alternatives. The proximity of injection wells to aquifer storage and recovery wells was a determining factor relative to injection well risk. Urban ecological risks were also indicated to be lower, though impacts of urban water use/reuse to the Everglades were not studied. Additional data collection and analysis were recommended to understand the effects of wastewater management on the cycling of water, nutrients and other constituents on southeast Florida. In particular, it was recommended that monitoring of effluents for nitrosamines and pharmaceutically active substances be implemented on a broad scale.     

Prediction of polychlorinated dibenzofuran congener distribution from gas-phase phenol condensation pathways

A model for predicting the distribution of dibenzofuran and polychlorinated dibenzofuran (PCDF) congeners from a distribution of phenols was developed. The model is based on a simplified chemical mechanism. Relative rate constants and reaction order with respect to phenol precursors were derived from experimental results using single phenols and equal molar mixtures of up to four phenols. For validation, experiments were performed at three temperatures using a distribution of phenol and 19 chlorinated phenols as measured in municipal waste incinerator exhaust gas. Comparison of experimental measurements and model predictions for PCDF isomer distributions and homologue pattern shows agreement within measurement uncertainty. The R-squared correlation coefficient exceeds 0.9 for all PCDF isomer distributions and the distribution of PCDF homologues. These results demonstrate that the distribution of dibenzofuran and the 135 PCDF congeners from gas-phase condensation of phenol and chlorinated phenols can be predicted from measurement of the distribution of phenol and the 19 chlorinated phenol congeners.     

Non-aqueous phase liquid spreading during soil vapor extraction

Many non-aqueous phase liquids (NAPLs) are expected to spread at the air-water interface, particularly under non-equilibrium conditions. In the vadose zone, this spreading should increase the surface area for mass transfer and the efficiency of volatile NAPL recovery by soil vapor extraction (SVE). Observations of spreading on water wet surfaces led to a conceptual model of oil spreading vertically above a NAPL pool in the vadose zone. Analysis of this model predicts that spreading can enhance the SVE contaminant recovery compared to conditions where the liquid does not spread. Experiments were conducted with spreading volatile oils hexane and heptane in wet porous media and capillary tubes, where spreading was observed at the scale of centimeters. Within porous medium columns up to a meter in height containing stagnant gas, spreading was less than ten centimeters and did not contribute significantly to hexane volatilization. Water film thinning and oil film pinning may have prevented significant oil film spreading, and thus did not enhance SVE at the scale of a meter. The experiments performed indicate that volatile oil spreading at the field scale is unlikely to contribute significantly to the efficiency of SVE.