Groundwater Treatment System Research Articles

TRANGUCH GASOLINE SITE CASE HISTORY

ABSTRACT A team, consisting of the United States Environmental Protection Agency; Pennsylvania Department of Environmental Protection; Pennsylvania Department of Health; Agency for Toxic Substances and Disease Registry; United States Coast Guard and United States Army Corps of Engineers, has completed major steps to provide a safe and healthy environment for the residents of Laurel Gardens, Hazleton, PA. What started as a simple underground gasoline leak took on more serious dimensions when gasoline vapors were found in nearby homes. The investigation and mitigation expanded to include over 400 properties. The remediation consists of a ground water treatment system and a soil vapor extraction system. This paper and its presenters look at the critical aspects of this case as the investigation went from subsurface soil and ground water contamination impacting surface water to the contamination of indoor air. It examines the impact of preferential pathways that include sanitary and storm sewers as well as a 19th century abandoned coal mine. In addition to the technical aspects, this examination looks at the public health and community issues that have surrounded this case.

Capture-zone design in an aquifer influenced by cyclic fluctuations in hydraulic gradients

Design of a groundwater pumping and treatment system for a wood-treatment facility adjacent to the tidally influenced Fraser River estuary required the development of methodologies to account for cyclic variations in hydraulic gradients. Design of such systems must consider the effects of these cyclic fluctuations on the capture of dissolved-phase contaminants. When the period of the cyclic fluctuation is much less than the travel time of the dissolved contaminant from the source to the discharge point, the hydraulic-gradient variations resulting from these cycles can be ignored. Capture zones are then designed based on the average hydraulic gradient determined using filter techniques on continuous groundwater-level measurements. When the period of cyclic fluctuation in hydraulic gradient is near to or greater than the contaminant travel time, the resulting hydraulic-gradient variations cannot be ignored. In these instances, procedures are developed to account for these fluctuations in the capture-zone design. These include proper characterization of the groundwater regime, assessment of the average travel time and period of the cyclic fluctuations, and numerical techniques which allow accounting for the cyclic fluctuations in the design of the capture zone.

Evaluation of PCBs biodegradability in sludges by various microbial cultures

AbstractThe application of aerobic and anaerobic treatment for removal of PCBs in sludges generated from a groundwater treatment system was investigated. The sludge was characterized by PCB concentrations of > 520 ppm, with Aroclors 1254 and 1260 accounting for 26 and 74%, respectively, as well as total organic carbon (TOC), and oil and grease (O&G) concentrations of 108,500 and 18,600 mg/L, respectively. Four treatments were explored: three aerobic and one anaerobic. Two types of bacterial innocula were aerobically tested: sludge from a poultry processing wastewater treatment plant, and a commercial seed (Petrobio®). Petrobio was tested aerobically with and without a biosurfactant/enzymes product (BOD‐Balance™), and was also tested anaerobically. Over a period of 60 days, PCB concentrations on a volumetric and solids basis were reduced by 73.4 to 88.0% and 64.7 to 80%, respectively. Aroclors 1254 and 1260 concentrations decreased by about 76 to 89%, and 73 to 89%, respectively. TOC and O&G removal efficiencies ranged from 77 to 93%, and from 52 to 86%, respectively.Generally, sludge from the poultry processing facility achieved the best results and exhibited the most rapid biodegradation kinetics. Aerobic PCB biodegradation rates for Aroclors 1254 and 1260 were 13.5% and 23%, respectively, faster than the anaerobic biodegradation rates. Overall PCB biodegradation kinetics conformed to first‐order, with rate constants ranging from 0.017 d−1 under anaerobic conditions to 0.022 d−1 under aerobic conditions, while both TOC and O&G biodegradation kinetics followed first‐order kinetics, with rate coefficients in the ranges of 0.025–0.047 and 0.014 and 0.04 d−1, respectively.

Modeling preferential flow in reactive barriers: implications for performance and design.

Reactive barriers are passive and in situ ground water treatment systems. Heterogeneities in hydraulic conductivity (K) within the aquifer-reactive barrier system will result in higher flux rates, and reduced residence times, through portions of the barrier. These spatial variations in residence time will affect the treatment capacity of the barrier. A numerical flow model was used to evaluate the effects of spatial variations in K on preferential flow through barriers. The simulations indicate that the impact of heterogeneities in K will be a function of their location and distribution; the more localized the high K zone, the greater the preferential flow. The geometry of the reactive barrier will also strongly influence flow distribution. Aquifer heterogeneities will produce greater preferential flow in thinner barriers compared to thicker barriers. If the barrier K is heterogeneous, greater preferential flow will occur in thicker barriers. The K of the barrier will affect the flow distribution; decreasing the K of the barrier can result in more even distribution of flow. Results indicate that less variable flow will be attained utilizing thicker, homogeneous barriers. The addition of homogeneous zones to thinner barriers will be effective at redistributing flow only if installed immediately adjacent to both the up- and downgradient faces of the barrier.

In-Situ Destruction of Chlorinated Hydrocarbons in Groundwater Using Catalytic Reductive Dehalogenation in a Reactive Well: Testing and Operational Experiences

A groundwater treatment technology based on catalytic reductive dehalogenation has been developed to efficiently destroy chlorinated hydrocarbons in situ using a reactive well approach. The treatment process utilizes dissolved H2 as an electron donor, in the presence of a commercial palladium-on-alumina catalyst, to rapidly reduce common chlorinated aliphatics such as trichloroethylene and tetrachloroethylene into nonchlorinated hydrocarbons such as ethane. Rapid reaction rates permit the deployment of a treatment unit within a dual-screened well bore, allowing contaminated groundwater to be drawn from one water-bearing zone, treated within the well bore, and discharged to an adjacent zone with only one pass through the system. A demonstration groundwater treatment system based on this concept was evaluated in a chlorinated hydrocarbon contaminated aquifer at a major Superfund site. The system rapidly destroyed a variety of common contaminants such as TCE and PCE and maintained its performance for a test period of 1 year. Operation of the treatment system was optimized to maintain catalyst activity and to prevent formation of intermediate compounds.

Economical Control of Discharges from Petroleum Tank Farms

This article provides a state regulator's view of petroleum tank farm environmental management options. Experience is shared regarding recently constructed systems for storm-water collection, storage and treatment, spill containment, and ground-water remediation. The use of out-of-service tanks for storm-water equalization is stressed. This information is timely because oil companies are now required to treat collected storm water and process water to achieve very low effluent contaminant levels. They are often required to also install low permeability liners in their tank farm containment areas. Thus a far greater volume of storm water is collected and it must be treated to a far greater degree than in the past. By using existing out-of-service tanks for storm-water equalization, all storm water receives treatment because the added retention capacity eliminates overflow or bypass during storm events. Much smaller and cheaper treatment systems may be used as retention tank contents are discharged gradually. Tips are given regarding design of effective storm-water, process-water, and ground-water treatment systems.

Treatment of chlorinated ethenes in groundwater with ozone and hydrogen peroxide

AbstractA study was conducted to enhance the performance of an advanced oxidation process in treating chlorinated ethenes in groundwater at IBM's groundwater treatment system at its Essex Junction, Vermont facility. A model describing the reaction kinetics and mass transfer of a co‐current ozone injection process is presented. This model, in conjunction with experiments, demonstrates that the treatment performance of the ozone treatment process at a given ozone/air concentration and ozone mass flowrate cannot be improved by varying process operating parameters such as number of ozone injectors utilized, use of a static mixer, or variation of groundwater flowrate through each injector. This is because dissolved ozone reaches equilibrium with the injected ozone/air mixture within two seconds of initial contact. Also, the Venturi‐type ozone injection system presently in use destroys nearly half of the injected ozone.Injection of hydrogen peroxide in conjunction with ozone increases the overall tetrachloroethylene (PCE) treatment efficiency by a factor of four (in comparison to ozone alone) at a H2O2/O3 mass ratio of between 1 and 2. Treatment of trichloroethylene (TCE) is enhanced by a factor of two. This enhancement of the oxidative treatment process results in a reduction in solvent mass load to a granular activated carbon (GAC) adsorption system located downstream, thus potentially reducing the usage GAC and regeneration of spent GAC. However, residual hydrogen peroxide and/or hydroxyl free radicals from the oxidation process effluent may interact adversely with certain grades of GAC; the causes of this interaction and methods to attenuate it (i.e., the use of more resistant grades of GAC) are discussed. Overall O3/H2O2/GAC system operating costs can potentially be reduced significantly (up to $ 20K annually). An economic analysis and system operation/cost optimization study are presented.

Millville site multimedia remediation program

AbstractThe Millville Remediation Program recently received the 1995 Honor Award for national excellence in environmental engineering from the prestigious American Academy of Environmental Engineers (AAEE). This article discusses various aspects employed to investigate and remediate multimedia contamination at the site and the unique applications of technologies which were responsible for receiving the AAEE honor award. Unique aspects of the project included utilization of variable speed drives to set individual pumping rates for each groundwater recovery well, development of sophisticated remote monitoring and operation capabilities which minimized O&M labor costs, and development of a groundwater treatment system which has consistently achieved nondetect effluent discharges. The remote monitoring and operation capabilities enables O&M staff to monitor and change setpoints for the groundwater recovery, treatment, and recharge systems.

Environmental project management using fast‐track methods to save time and money

AbstractIn 1992, Eaton Corporation, a major manufacturer of vehicle components and electrical and electronic controls, implemented a fast‐track remediation method to expedite the installation of a groundwater recovery and treatment system to contain and mitigate a chlorinated solvent plume at an industrial site. This dual‐track method included fast‐track and turnkey project management techniques. Our goal was to expedite the containment and removal of identified contamination, which would protect the environment, minimize future liability, and significantly reduce remediation time and costs. This goal was in the best interests of all concerned—Eaton, the community, and the state regulatory agency. This strategy took the project from dual‐track concept approval by the regulatory agency to remediation system installation and start‐up in less than eight months, cutting over two years from the standard Remediation Investigation/Feasibility Study (RI/FS) approach, with consequent earlier contaminant containment. Total remediation costs were half of what they would have been under the standard RI/FS procedure for this site.

IN SITU BIOREMEDIATION OF PETROLEUM HYDROCARBON CONTAMINATED SOIL AND GROUND WATER

ABSTRACT OHM designed and installed an in situ bioremediation system with an above ground water treatment system at a petroleum hydrocarbon distribution and fuel facility. The remediation system consists of an infiltration trench system to deliver treated, amended ground water to the upper silty lens, and an injection well system to deliver water to the lower sand and gravel lens. A French drain is located downgradient of the groundwater injection systems to provide hydraulic control of the site. Recovered ground water is pumped to an on-site treatment system prior to re-injection.

Remediation of a VOC-contaminated superfund site using soil vapor extraction, groundwater extraction, and treatment: A case study

A case history of remedial action taken at the primary contaminant source area within the Verona Well Field Superfund Site in Battle Creek, Michigan. Included is a site description, a description of the soil and groundwater treatment systems, plus a summary of the lessons learned through six years of active remediation.

Metabolic diversity of aromatic hydrocarbon-degrading bacteria from a petroleum-contaminated aquifer.

We characterized bacteria from contaminated aquifers for their ability to utilize aromatic hydrocarbons under hypoxic (oxygen-limiting) conditions (initial dissolved oxygen concentration about 2 mg/l) with nitrate as an alternate electron acceptor. This is relevant to current intense efforts to establish favorable conditions for in situ bioremediation. Using samples of granular activated carbon slurries from an operating groundwater treatment system, we isolated bacteria that are able to use benzene, toluene, ethylbenzene, or p-xylene as their sole source of carbon under aerobic or hypoxic-denitrifying conditions. Direct isolation on solid medium incubated aerobically or hypoxically with the substrate supplied as vapor yielded 10(3) to 10(5) bacteria ml-1 of slurry supernatant, with numbers varying little with respect to isolation substrate or conditions. More than sixty bacterial isolates that varied in colony morphology were purified and characterized according to substrate utilization profiles and growth condition (i.e., aerobic vs. hypoxic) specificity. Strains with distinct characteristics were obtained using benzene compared with those isolated on toluene or ethylbenzene. In general, isolates obtained from direct selection on benzene minimal medium grew well under aerobic conditions but poorly under hypoxic conditions, whereas many ethylbenzene isolates grew well under both incubation conditions. We conclude that the conditions of isolation, rather than the substrate used, will influence the apparent characteristic substrate utilization range of the isolates obtained. Also, using an enrichment culture technique, we isolated a strain of Pseudomonas fluorescens, designated CFS215, which exhibited nitrate dependent degradation of aromatic hydrocarbons under hypoxic conditions.

Performance of soil flushing and groundwater extraction at the United Chrome Superfund site

In 1987, CH2M HILL, under contract with the U.S. EPA, undertook the cleanup of the United Chrome Superfund site in Corvallis, Oregon. Waste dis- posal practices and leaky plating tanks at this chrome plating facility had resulted in heavy contamination of soil and groundwater by hexavalent chromium. Distinguishing elements of this site remediation project were two infiltration basins to flush contaminated soils, a 23-well groundwater extraction network in low permeability soils, and treatment of the concentrated chromium wastewaters. Remedial actions also included decontamina- tion and demolition of structures, and offsite disposal of 1,100 tons of contaminated soil and debris. The infiltration basins and groundwater extraction and treatment system have been operating since July 1988. This paper presents the data and experience gathered on the system's perfor- mance during the 2 years of operation, and points to potential applications at other sites.

Remediating groundwater using a hydraulic containment system for pump and treat

AbstractTwenty years of waste disposal operations at the Conservation Chemical Company (CCC) site in Kansas City, Missouri, led to contamination of soils and groundwater on a six‐acre site. As a result of this contamination, the site was listed on the federal government's National Priorities List.Following extensive litigation initiated in 1982, more than 200 contributors to the site (Potentially Responsive Parties or PRPs), CCC's insurance companies, and the government ultimately reached a settlement to fund the remedial action. The remedy that was agreed upon included: (1) a permeable cap to allow water intrusion to assist groundwater cleanup; (2) a with drawal well system to achieve an inward groundwater gradient; and (3) a groundwater treatment system employing several unit operations. Containment of the contaminated plume relied on hydraulic, rather than structural, containment to prevent mitigation of contaminants from the site. ABB Environmental Services, Inc. (ABB‐ES) was retained to perform treatability tests and to design, construct, and start up the groundwater treatment plant after the installation of the permeable cap by others.

Methods of Obtaining Aquifer Data for Groundwater Remediation System Design

Characterization of unconfined aquifer parameters prior to design of a groundwater pumping and treatment remediation system is essential for proper system engineering and yields long-term cost savings. An approach for stepwise characterization includes (1) physical property definition of sediments within the saturated zone to initially estimate aquifer parameters, and (2) proper selection, design, and execution of aquifer tests using appropriate data analyses methods. During a soil/groundwater investigation, soil samples are obtained from the saturated zone. These samples provide information on the geometry of subsurface lithosomes and are used in a series of laboratory analyses to determine the porosity, permeability, pore-fluid saturation, grain density, grain-size distribution, and saturated hydraulic conductivity of the aquifer at the sample points within the saturated zone. The analytical results are used to calculate average hydraulic conductivity (K), transmissivity (T), and specific yield for the aquifer. these data permit the appropriate aquifer test to be engineered. Results from aquifer tests are used to refine original estimates of aquifer parameters, and to accurately quantify to down- and lateral-gradient capture zones from pumping wells at select pumping rates. This provides information needed for groundwater treatment system design. Cost analyses of various pumping and treatment remediation systems indicate that expendituresmore » associated with thorough aquifer characterization represent less than 5% of the total remedial project cost. These expenditures represent a savings through the life of a project due to greater efficiency of a properly designed remediation system.« less

Plume management—An inexpensive long-term strategy for groundwater contamination at low-risk sites

The costs of full-scale groundwater treatment and source removal and the unrealistic goals of many groundwater treatment projects have prompted a reevaluation of long-term remediation strategies. This report has presented a plan that manages the groundwater contamination and is sensitive to the changing regulatory and technical climate. The groundwater treatment system is inexpensive to install, operate, and maintain. Plume migration has been stopped. Treatment time is exceedingly long, but the site operator is now free to evaluate new technology or the development of a risk-based clean-up strategy. We believe that implementing such a strategy at low-risk sites can result in significant cost savings to the hazardous waste clean-up problem.