Evaluation of a sustainable remediation option: beneficial reuse of petroleum-contaminated sediment as an energy source.

The characteristics of petroleum-contaminated sediment (PCS) have been evaluated to assess whether the practice of its beneficial reuse as a sole or supplemental energy source is sustainable relative to other sediment remediation options such as monitored natural recovery (MNR), capping, or off-site disposal. Some of these remediation options for PCS are energy-intensive and/or require land utilization. The energy and compositional analysis results indicate a low carbon content (15-17%(wt)) and corresponding low energy values of 5,200 kJ/kg (2,200 Btu/lb) to 5,600 kJ/kg (2,400 Btu/lb). However, given other decision-making criteria, the sediment may contain enough value to be added as a supplemental fuel given that it is normally considered a waste product and is readily available. The thermogravimetric profiles obtained under both combustion and pyrolytic conditions showed that the sulfur contents were comparable to typical low sulfur bituminous or lignite coals found in the United States, and most of the volatiles could be vaporized below 750 degrees C. The heavy metal concentrations determined before and after combustion of the PCS indicated that further engineering controls may be required for mercury, arsenic, and lead. Due to the potential for reduction of public health and environmental threats, potential economic savings, and conservation of natural resources (petroleum and land), removal of PCS by dredging and beneficial reuse as a supplemental fuel clearly has merit to be considered as a sustainable remediation option.

Nature of the interlayer environment in an organoclay optimized for the sequestration of dibenzo-p-dioxin.

A Na-smectite clay (Na-SWy-2) was exchanged with various amounts of dimethyldioctadecylammonium bromide (DODA-Br) up to twice the cation exchange capacity (CEC). The organoclay (DODA-SWy-2) with DODA-Br added at 2 × CEC exhibited a maximum 4.2 nm d-spacing and a 31.4% carbon content, which demonstrates DODA(+) intercalation. DODA-SWy-2 was evaluated as an archetype of commercial products used to sequester hydrophobic contaminants, and the nature of the primarily C18 alkylhydrocarbon-chain interlayer environment was emhasized. Shifts in ν(CH) and CH(2) rocking band positions in DODA-SWy-2-complex FTIR-spectra indicate that DODA C18 chains were more ordered as DODA surface coverage was increased. Differential scanning calorimetry analysis indicated a DODA-SWy-2 gel-to-liquid transition temperature much lower than the melting point of crystalline DODA-Br and similar to that of aqueous DODA-Br vesicles. This suggests that the transition was governed by C18 alkyl tail-tail interactions in the clay interlamellar region. Dibenzo-p-dioxin (DD) sorption from water by DODA-SWy-2 was compared to DD sorption by the geosorbents granular activated carbon (GAC), K-exchanged saponite, and a muck soil. The linear K(l) sorption coefficients (log K(l)) from a linear fit of the sorption isotherms were 4.37 for DODA-SWy-2, 5.55 for GAC, 3.19 for muck soil, and 2.46 for K-saponite. The DD-organic-matter-normalized sorption coefficient (K(om)) was ∼2.4 times the octanol-water partition coefficient (K(ow)). This indicates that DD has a higher affinity for the nonpolar interlayer DODA organic phase than for octanol. In contrast, the K(om) for muck soil DD sorption was ~10 times less than K(ow), which reflects the higher polarity of amorphous soil organic matter relative to octanol. Enhanced DD uptake by the DODA-derived lipophilic phase in the organoclay is attributed to the low polarity, "open" C18 alkyl structure due to the physical dimensions of "v-shaped" DODA(+) molecular, and low density of the interlamellar phase (~0.50 g/cm3) density of intercalated DODA(+).

Evaluation of bioaerosol components, generation factors, and airborne transport associated with lime treatment of contaminated sediment.

Lime treatment has been used in contaminated sediment management activities for many purposes such as dewatering, improvement of physical properties, and reducing contaminant mobility. Exothermic volatilization of volatile organic compounds from lime-treated sediment is well known, but potential aerosolization of bioaerosol components has not been evaluated. A physical model of a contaminated sediment treatment and airborne transport process and an experimental protocol were developed to identify specific bioaerosol components (bacteria, fungi, cell structural components, and particles) that may be aerosolized and transported. Key reaction variables (amount of lime addition, rate of lime addition, mixing energy supplied) that may affect the aerosolization of bioaerosol components were evaluated. Lime treatment of a sediment contaminated with heavy metals, petroleum-based organics, and microorganisms increased the sediment pH and solids content. Lime treatment reduced the number of water-extractable bacteria and fungi in the sediment from approximately 10(6) colony-forming units (CFU) x mL(-1) to less than the detection limit of 10(3) CFU x mL(-1). This reduction was seen immediately for bacteria and within 21 days for fungi. Lime treatment immediately reduced the amount of endotoxin in the sediment, but the effects of lime treatment on beta-D-glucan could not be determined. The temperature of the treated sediment was linearly related to the amount of lime added within the range of 0-25%. Bacteria were aerosolized during the treatment trials, but there was no culturable evidence of aerosolization of fungi, most likely because of either their particular growth stage or relatively larger particle size that reduced their aerosolization potential and their collection into the impingers. Nonbiological particles, endotoxin, and beta-D-glucan were not detected in air samples during the treatment trials. The amount of lime added to the reaction beaker and the relative amount of mixing energy supplied to the reaction significantly affected the aerosolization ratio of bacteria (amount of aerosolized bacteria divided by the amount of bacteria in untreated sediment) from the reaction beaker. The rate of lime addition did not significantly affect the aerosolization ratio of bacteria. The aerosolization results suggest that exposure to bacteria is possible with sediment treatment activities, but the hazard level could not be determined because speciation of the aerosolized bacteria for pathogen identification was not performed, and health and safety standards and criteria for bioaerosol components have not been developed. Quantitative scaling analysis and whether the system represents actual environmental conditions were not studied.

Evaluation of lead availability in amended soils monitored over a long-term time period.

Two different soil amendment processes were evaluated for reducing lead availability from a contaminated soil at a demonstration study site, to reduce potential public health and environmental concerns. A limited variety of in vitro laboratory "availability" tests (relative bioaccessible and environmental mobility) were performed to determine if the available lead in the contaminated soil would be less available after in situ soil amendment (chemical treatment). The relative bioaccessibility results were evaluated in both a short-term period (within 24 h after treatment) and over a long-term time period (quarterly basis for 5 years). Reduction in relative bioaccessibility was noted for one of the treatments immediately after treatment; however, both treatments indicated a significant upward trend in bioaccessibility values over a 5-year time period after treatment. The comparison between the treated units and the control units indicated that the long-term effectiveness of the treatment processes could not be demonstrated.

Preliminary assessment of worker and ambient air exposures during soil remediation technology demonstration.

Hazardous waste site remediation workers or neighboring residents may be exposed to particulates during the remediation of lead-contaminated soil sites. Industrial hygiene surveys and air monitoring programs for both lead and dust were performed during initial soil sampling activities and during pilot scale technology demonstration activities at two lead-contaminated soil sites to assess whether worker protection or temporary resident relocation would be suggested during any subsequent remediation technology activities. The concentrations of lead and dust in the air during pilot scale technology demonstration studies were within applicable exposure guidelines, including Occupational Health and Safety Administration permissible exposure limits, National Institute for Occupational Safety and Health recommended exposure limits, American Conference of Governmental Industrial Hygiene threshold limit values, and the United States Environmental Protection Agency's National Ambient Air Quality Standards program limits.