Thesis (M.S. in chemical engineering)--Washington State University, August 2006. / Includes bibliographical references (p. 69-74).

Thesis (M. Sc.)--University of Hong Kong, 2005.

The identification and subsequent treatment of contaminated land and groundwater is currently being regulated by the Environment Agency. The closure of gasworks sites during the late 1960s left areas of land contaminated with undesirable residues of the manufactured gas process, which were left to cause further pollution by leaching into surface and groundwater. The techniques available to remediate these contaminated media are numerous, but most tend to suffer from at least one major disadvantage, usually time or cost.

Mercury -contaminated sediments often act as a sink of mercury and produce methyl-mercury, an acute neurotoxin which readily bio accumulates, due to the presence of bacterial communities hosted by the sediment. One common remediation approach to manage methyl-mercury is to amend the sediment by capping or directly mixing with a sorbent. This thesis aims to assess the capabilities of some calcium-based sorbent to act in that capacity. Laboratory experiments were implemented to simulate mercury fate and behavior in geochemical conditions that capping would likely create. Well-mixed slurries showed that gypsum materials were disparate and their behavior was similar from sand to organocaly. Mercury sorption capacities of these gypsums were poor with a sorption coefficient approximately equal to 300 L/kg. Reduction of methylmercury was minimal and even increased in two of the three materials. Therefore, the three gypsums, which tend to be more cohesive when wetted, doesn’t constitute a viable material for sediment capping. / text

As more sites containing contaminated sediments are remedied with sediment caps, so grows the interest among site managers and engineers in the benefits afforded by active capping. While traditional sediment caps can effectively manage strongly solid-associated contaminants in many situations, under certain conditions active caps or amendments may be needed to effectively reduce risk to an acceptable level. This research assessed the predicted and observed breakthrough of dissolved organic contaminants in two newly developed geotextiles; one designed to sorb non-aqueous–phase liquids (NAPLs), the other dissolved-phase contaminants. The performance of the geotextiles was then compared to that of another remediation technology that has been deployed in the field for two years. All active materials were then evaluated based on their sorption capacity and their predicted life under field conditions. The sorbent containing geotextiles designed for active capping applications were tested in columns to simulate field conditions, where upwelling groundwater would be contaminated by impacted sediments, thereby transporting contaminants to the water column. The contaminants of interest in these studies were three polycyclic aromatic hydrocarbons (PAHs) of varying hydrophobicity. Breakthrough curves for the materials vii of interest were constructed for the three PAHs and were fit to an advection-dispersion model to predict the mass of contaminants sorbed onto them. This mass was then compared and verified to be similar to values found in literature. The performance of the geotextiles was compared to that of organoclay deployed in Portland, OR, at the McCormick & Baxter Creosoting Company Superfund Site. In 2004, over 22 acres of sediment at the site were remedied with both passive and active caps to mitigate the effects of decades worth of contamination. In certain portions of the site, a 12 inch thick layer of organoclay was employed, while at other portions of the site, conventional sand or a thin reactive core mat with the equivalent of approximately 1 cm of organoclay were employed. The continued effectiveness of these sediment caps was evaluated using a variety of laboratory techniques, including measuring samples’ hexane extractable material, which is a proxy for NAPL contamination, as well as their PAH bulk concentrations. These analyses performed on core samples allowed for the generation of vertical profiles critical to cap evaluation. Despite possessing a significantly greater specific sorption capacity, the geotextiles could not offer the same protection for the extended period of time that the bulk organoclay could. The greater mass of organoclay deployed in bulk at the McCormick & Baxter site allowed a much greater sorption capacity to be placed. It would take over sixty stacked layers of the one of the geotextiles evaluated in these studies to achieve the same capacity for dissolved-phase contaminants as the 1 ft organoclay cap. However, no significant penetration of NAPL into the bulk organoclay has been noted, and thus even the thin layer within a geotextile might have been sufficient at the site, despite its significantly lower overall capacity. The data generated provides information as to the expected capacity of the various sorbent placement approaches and can help guide decisions at other sites. / text

Sediments serve as the ultimate sink for many hydrophobic organic compounds and thus present a residual environmental risk many years after sources of contamination are eliminated. Monitored natural attenuation and ex situ treatment processes are often ineffective for treatment; as such in situ remediation technologies (i.e., capping) are under review. A conventional in situ remediation technology for refractory sediment contaminants is placement of a clean layer of material as a cap. A series of design models was developed to predict the performance of caps composed of the traditional material, sand. A passive sampling method using polydimethylsiloxane (PDMS) fibers for evaluating the performance of caps was developed and tested in the laboratory. The results of the laboratory analysis showed the ability to measure pore water concentration profiles in caps, the consistency of profiles with design model predictions, and correlation of PDMS-derived concentrations with contaminant uptake in test organisms. Potentially more effective caps composed of permeable adsorptive materials (to retard contaminant migration) and impermeable materials (to divert groundwater flow) were placed along with a conventional sand cap in the Anacostia River in Washington DC in 2004. Field tests of this site showed the ability to measure in situ pore water concentration profiles in caps using a field-deployable version of the PDMS passive sampling device and demonstrated the necessity of pore water-based approaches for analyzing caps. A model for assessing the uptake rates of HOCs within PDMS fibers was developed and shown to predict the kinetics of HOC sorption into fibers. The model is based on external-mass transport processes, which through a series of analyses were shown to be more significant than internal diffusion in PDMS fibers. Using the PDMS approach, field bioaccumulation tests at the Anacostia site as well as at San Diego Bay and Hunters Point Naval Shipyard showed stronger correlation of PDMS-based pore water concentrations than solid-phase concentrations with observations of bioaccumulation in the field. The overall conclusions suggest that pore water concentrations can often be a better indicator of risk than bulk solid concentrations. / text

No description available.

Oil spills are a universal threat impacting local, national and world communities alike. Bioremediation that is natural, efficient, economical and safe is the best solution for protecting the environment from oil related damages. In this study, motor oil degrading bacteria were isolated from oil-contaminated soil samples from a suburban Atlanta, Georgia community. Mineral salt broth containing 1 Ow-40 motor oil as the sole carbon source was used to isolate motor oil degrading bacteria. Motor oil tolerant and metabolizing bacteria were identified using morphological and biochemical tests. Two bacterial isolates were then tested for their tolerance varying concentrations of diesel and kerosene oils for comparison with motor oil consumption. Observed results suggest that the isolated bacteria from oil contaminated soil possess abilities to metabolize motor oil, kerosene and diesel. Knowledge of the tolerance ranges of the isolated bacteria can indicate their potential to be of use in the remediation of terrestrial petroleum oil spills in a manner that is natural, economical, quick and efficient.

In the development of a non-aqueous bitumen extraction process, a major obstacle is solvent loss due to hydrocarbon attachment to the reject sand grains. A proposed solution to this problem is to wash (i.e. remediate) the oil-contaminated sand grains with water and surfactants. This research is focused on developing a protocol to evaluate the performance of particular surfactant types and water chemistry; emphasis was placed on using minimal amounts of water to recover the residual oil. To start, a series of jar tests were conducted (using heptane and hexadecane as solvents)to study the phase behaviours of oil-water-surfactant ternary systems. This was followed by the development of a new washing protocol for the purpose of evaluating remediation performance. Finally, the correlation between overall remediation performance and the oil-water interfacial tension was discussed.

Abstract The purpose of this study was to evaluate the efficiency of biosparging for in situ remediation of groundwater at a site contaminated by petrochemicals. To this end, laboratory-scale (lab-scale for short) and pilot-scale tests were carried out. In the lab-scale study, three possible ways (i.e., by injecting air, by adding hydrogen peroxide, and by adding magnesium peroxide) of increasing the dissolved oxygen content in the groundwater were evaluated in terms of the resulting total bacterial count. Under the conditions used in this work, air injection was found to the most effective one. By injecting compressed air into the mixture of petrochemicals-contaminated soil and groundwater at a flow rate of 175mL/min for five minutes, the total bacterial count of the aerobic bacteria was increased greatly from 102CFU/mL to 107CFU/mL. The concentrations of benzene, toluene, ethyl benzene, and xylenes (BTEX) also were reduced to lower than 0.5£gg/L. Based on the findings obtained from the lab-scale study, air injection was adopted for the enhancement of pilot-scale in situ bioremediation of petrochemicals-contaminated groundwater at a selected site in a petrochemical plant. To evaluate the treatment efficiency of biosparging for the removal of BTEX and naphthalene, in addition to an upstream groundwater well, six one-meter-apart monitoring wells were installed in at the test site the flow direction of groundwater. In the center of the test site, one air injection well and ten soil gas monitoring points also were installed to determining the radius of influence of the air injection well. It was found that an air injection rate of 40L/min was capable of providing sufficient air to all of the monitoring wells of groundwater and increasing the total bacterial count of aerobic bacteria from the order of 102CFU/mL to 106CFU/mL. For a test period of 99 days, the concentrations of all target contaminants in each groundwater monitoring well were decreased markedly. More specifically, the total organic carbon was reduced from 12.7-43.4 mg/L to 3.5-14.9 mg/L; biochemical oxygen demand, from 124-526 mg/L to 43-153 mg/L; benzene; toluene, from 29.88-62.34 mg/L to 11.72-12.82 mg/L ; ethyl benzene, from 0.92-5.30 mg/L to 0.86 mg/L-< 0.5£gg/L; xylenes, from 9.31-47.58 mg/L to 4.07 mg/L -< 0.5£gg/L; and naphthalene, from15.31-0.92 mg/L to < 0.5 £gg/L. Additionally, pH, temperature, and concentrations of various cations determined for the groundwater as well. During the 99-day test period, the following were found: pH varied in the range of 6.75-7.45; temperature, 30-32¢J; Ca2+, 45-65 mg/L; Mg 2+, 16-24 mg/L; Na+, 35-60 mg/L; K+, 8-14 mg/L; and total iron, 2.0-4.0 mg/L. Thus, under the conditions used in this work, the biosparging technology employed was found to have an overall treatment efficiency of over 60% for BTEX and 100% for naphthalene. To increase the overall treatment efficiency, a prolonged air injection is needed at this test site. Keywords: biosparging, groundwater, contaminated site, petrochemicals