Showing papers in "Environmental Progress in 1990"

The use of pervaporation for the removal of organic contaminants from water

Abstract: A resistance-in-series model was formulated and validated using silicone rubber hollow fibers for the treatment of water containing trichloroethylene (TCE). This process model was coupled with a costing model to assist in the design of pervaporation systems. The model was used to predict performance, capital cost and operation cost of pervaporation for water treatment applications and to optimize design variables such as membrane thickness and the module hydrodynamics

Heterogeneous photocatalysis for water purification: Contaminant mineralization kinetics and elementary reactor analysis

Abstract: Heterogeneous photocatalysis is the third and newest of an emerging series of photolytic technologies for water treatment and purification. The earlier examples of ultraviolet ozonation and ultraviolet peroxidation involved direct photoactivation of the contaminant and/or dissolved oxidant and are dominated by solution phase chemistry. Photocatalysis, in contrast, involves photoactivation of the heterogeneous catalyst (an example of indirect photochemical processes) and is dominated by reaction events initiated at the catalyst surface. This paper summarizes (1) current rate equations for photocatalyzed simultaneous destruction of multiple oxidizable organic contaminants and (2) simplified convective transport equations appropriate to photoreactor design under various degrees of fluid mixing and simultaneous reaction contributions by heterogeneous (photocatalyzed) as well as homogeneous reactions.

Chitosan in crab shell wastes purifies electroplating wastewater

Abstract: Chitosan, a polyglucosamine, can be formed by de-acetylating chitin, a major structural component of crustacean shells. Crab shell particles were treated and deacetylated to elaborate chitosan on their outer peripheries. Experimental data and an approximate preliminary economic analysis are presented to show the potential of using treated crab shell waste for purifying electroplating rinsewater. This approach is compared with currently used precipitation technology for removing metal ions.

Adsorptive capacities of activated carbon for organic constituents of wastewaters

Abstract: The adsorptive capacities of activated carbon for major organic constituents (target compounds) of a wide variety of wastewater were measured in pure water and in actual wastewater samples. Competitive adsorption due to the presence of other orgnic components of total organic carbon of the wastewater (background TOC) reduced carbon capacities for all target compounds in the wastewaters from the respective pure water isotherms. The capacity reduction for a target compound was found to depend on the relative adsorptivity of the target compound versus competing compounds (poorly adsorbed TOC components produced a small reduction in capacity for a more strongly adsorbed target compound), and the fraction of the background TOC attributable to the target compound. Those findings were validated by carbon column adsorption breakthrough data.

Supercritical CO2-cosolvent extraction of contaminated soils and sediments

Abstract: DDT- or PCB-contaminated topsoils of high organic content were extracted using supercritical CO2 or CO2-5 wt% cosolvent (toluene, acetone, methanol, acetic acid, diethylamine) mixtures at 313 K and 101 bar. In separate experiments, the pure contaminants were dissolved in supercritical CO2 at the same conditions and the equilibrium solubilities determined. Most of the cosolvents only marginally improve extraction rates over the case of pure CO2. Methanol, however, increases total amounts of DDT removal from 50–80% to > 95%, and increases DDT and PCB extraction rates by as much as an order of magnitude. Methanol is a superior cosolvent probably because its hydrogen-bonding ability is better suited to interaction with the organic matter in the soil (humic acids, fulvic acids, polysaccharides); the organic matter essentially “dissolves” the contaminants in the soil matrix. Comparing a simple fixed–bed, local equilibrium (based on pure contaminant equilibria) desorption model to the actual desorption data indicates that contaminant solubilities in supercritical fluids are enhanced (over the pure contaminant case) when desorbing from soils. The enhancements may be related to the simultaneous desorption of other low molecular-weight organics from the soils.

Bioturbation: A facilitator of contaminant transport in bed sediment

Abstract: The biological activity of benthic organisms (=bioturbation) in bed sediments can be significantly more important than physicochemical processes in the movement of sediment particles and interstitial constituents within the sediment column and to the overlying water. Bioturbation-driven transport processes may be served orders of magnitude more rapid than molecular-driven processes for some constituents, i.e., particle reactive compounds like PCB, when considered on a chemical pore water concentration gradient basis. Benthic organisms affect particle redistribution and solute transport by burrowing, ingestion/excretion, tube-building and biodeposition. In most benthic environments, whether freshwater, estuarine or marine, numbers of organisms and rates of sediment turnover are highest in the oxygenated zone above the redox boundary, generally the top 2-5 cm of the sediment column. However, a variety of organisms penetrate deeper into the sediment and may also be important in transport of both dissolved and particle reactive constituents. When considering capping of contaminated sediment in place or capping of contaminated dredge spoils, the effects of bioturbation on the mobility of the contaminants must first be considered before establishing engineering design criteria. Capping of contaminated bed sediments or dredge spoils can elevate the bioturbated zone above the contaminated bed sediment and thus potentially reduce the ratemore » of contaminant transport by several orders of magnitude.« less

Treatment of organic-contaminated wastewater streams by pervaporation

Abstract: The removal and recovery of organic contaminants from aqueous streams by pervaporation membrane systems is a viable and economical treatment for many waste streams. Specific opportunities for the technology are identified in this paper. Laboratory and pilot system data are used to develop system designs and to calculate the cost of treating specific streams.

An overview of solvent extraction treatment technologies

Abstract: In the course of evaluating potential technologies for treatment of contaminated soils at a regulated site in the upper Midwest, solvent extraction technology was reviewd and appeared to be a viable alternative to incineration and land disposal. Because of stringent federal and state land disposal rules, liability issues, and rising disposal costs, technologies that will treat and detoxify hazardous wastes effectively are preferred over other less aggressive technologies. Industry is actively seeking and evaluating options, and the regulatory community is encouraging development and application of new treatment technologies as alternatives to land disposal. To advance this effort, the U.S. Environmental Protection Agency (EPA) established the Superfund Innovative Technology Evaluation (SITE) program to promote the development of innovative technologies and to demonstrate such technologies at Superfund sites. Solvent extration technology is being evaluated in the SITE program. This paper was prepared because of the lack of a compiled source of existing information on the alternative use of solvent extraction technology for treating soils contaminated with hazardous substances in a manner other than incineration.

Feasibility of using alginate to absorb dissolved copper from aqueous media

Abstract: Alginate (a biopolymer from kelp and some bacterial strains) is known to absorb copper favorably in the presence of other cations. In this work, the feasibility of using a 2-liter batch three-phase (air/liquid/alginate gel) loop fluidized bed reactor to polish water containing 10-150 ppm dissolved copper was investigated. Three methods were tested: (1) calcium alginate spheres, prepared by dispensing sodium alginate (3.2 wt. % in water) into a 0.05 M calcium nitrate solution, were used as the absorbent, (2) the alginate spheres were formed in situ by dispensing the sodium alginate solution directly into the reactor fluid, and (3) same as (2) except that a trace amount of EDTA was added to the alginate solution. Batch absorption data showed that Method 3 yielded the best result; the concentration of dissolved copper was successfully reduced from 140 ppm to 10 ppm with 3.2 g sodium alginate and 0.2 g EDTA used. However, when the initial concentration was below 40 ppm, both Method 2 and Method 3 are not recommended because the concentration of dissolved copper was too low to allow in situ formation of alginate spheres. Method 1 was found to be useful for treating water containing 10 ppm dissolved copper.more » But the competition from calcium seriously affected the effective capacity of the alginate for copper. The application of the classical shell progressive model to describe the absorption kinetics was discussed.« less

Supercritical fluid extraction of aromatic contaminants from a sandy loam soil

Abstract: Near-critical fluids and liquefied gases can achieve high efficiencies in the extraction of organic contaminants from soil Adsorptive behavior of several polycyclic aromatic hydrocarbons (PAHs) from supercritical carbon dioxide (SC CO{sub 2}) onto sandy loam-type soil has been characterized Data for the solubility of phenanthrene, anthracene, triphenylene, and perylene in SC CO{sub 2} demonstrates a strong relationship between solubility and the carbon number and angularity of the ring structure Soil adsorption isotherms for these compounds are non-linear, and have been described using Freundlich and BET adsorption models The slope of the adsorption isotherms has been correlated with PAH solubility on log-log coordinates Addition of polar modifiers, eg, water or methanol, dramatically reduces the PAH adsorption levels, indicating the importance of polar adsorption sites on soil surfaces

In situ biodegradation of TCE contaminated groundwater

Abstract: Trichloroethylene (TCE) is one of the most widely used chlorinated solvents; it is also a common groundwater contaminant. TCE-contaminated groundwater is presently treated by transferring the solvent either to a solid (carbon adsorption) or to the atmosphere (air stripping). Biological treatment of the contaminated water is an alternative that causes complete destruction of the solvent. When performed within the aquifer it is termed in situ biotreatment. A specific strain of bacteria (G4) has been isolated that degrades TCE enzymatically. The process has been extensively tested in the laboratory and confirmed in a field pilot test. The pilot test involved the injection of a clean, oxygenated water stream directly into the TCE plume. Nutrients and G4 were added to the injection stream and TCE concentrations were measured up - and downgradient of the injection well. A decline in TCE levels was observed eight hours after injection and continued for the following ten days. TCE concentrations were reduced from a high of 3,000 ppb to a mean value of 78 ppb during a 20 day period.

Removal of organics from offshore produced waters using nanofiltration membrane technology

Abstract: The separation of oil and produced water mixtures from oil and gas producing wells has traditionally been accomplished by gravity settlers (e.g., multi-phase separators, skimmers, and flotation cells). However, current EPA regulations on the organic content of discharged produced water have reached the limits of these separation techniques. The industry is in need of new technologies to treat these waters. One such technology that the authors have found promising is organics/water separation by nanofiltration membranes.

Separation of hazardous organics by reverse osmosis membranes

Abstract: Extensive experimental studies showed that thin-film, composite membranes can be used effectively for the separation of selected hazardous organic compounds. This waste treatment technique offers definite advantages in terms of high solute separations at low pressures (<2 MPa) and broad pH operating range, and the use of charged membrane would allow the selective separation of some organics from feeds containing high salt concentrations. In addition, feed pre-ozonation of selected organics has been shown to provide significant improvement in flux and rejection characteristics for both charged and uncharged membranes due to formation of ionizable organic acid intermediates during the ozonation that do not interact as strongly with the membrane. It has been shown that the overall ozonation–membrane process could be greatly effective in producing permeate water of high quality while minimizing the volume of waste that must be further treated. Batch adsorption studies were also utilized to understand the membrane flux drop phenomena in non-ozonated solutions.

Bench–scale evaluation of calcium sorbents for acid gas emission control

Abstract: Calcium sorbents for acid gas emission control were evaluated for effectiveness in removing SO{sub 2}/HCl and SO{sub 2}/NO from simulated incinerator and boiler flue gases. All tests were conducted in a bench-scale reactor (fixed-bed) simulating fabric filter conditions in an acid gas removal process. Reagent grade Ca(OH){sub 2} was used to establish baseline sorbent performance. The reactivity of reagent grade Ca(OH){sub 2} with HCl from SO{sub 2}/HCl mixtures gradually increased with decreasing approach to saturation temperature. SO{sub 2} reactivity toward Ca(OH){sub 2} was very sensitive to approach to saturation. Novel calcium silicate sorbents were tested for reactivity with both SO{sub 2} and HCl. A thermal window for optimum NO removal was found at 90{degree}C (194{degree}F) when Ca(OH){sub 2} was used at SO{sub 2}/NO ratios of 1:1. Reactivity of Ca(OH){sub 2} toward SO{sub 2} from SO{sub 2}/NO mixtures was very sensitive to approach to saturation, while reactivity with NO was insensitive. Several additives were subsequently tested to determine optimum sorbent combinations for SO{sub 2}/NO control. To date the most promising additives are Mg(OH){sub 2} and Na{sub 2}HPO{sub 4} at 10 mol% concentrations. As with SO{sub 2}/HCl, calcium silicate has been shown to be superior for SO{sub 2}/NO capture. Some implications formore » larger-scale process configurations and sorbent selection for HCl/SO{sub 2}/NO control are discussed. Future activities and limited larger-scale pilot plant results are also discussed.« less

EPA's assessment of European contaminated soil treatment techniques.

Abstract: Site remediation is a pressing issue in European countries due to limited availability of land. Therefore, much progress is being made in the development of effective technologies for remediating contaminated sites. The purpose of the program described in this paper was to investigate the most successful and innovative European technologies for potential introduction into U.S. markets. Phase I of this EPA–sponsored project was a 9-month research effort which identified 95 innovative technologies in use or being researched in foreign countries. During Phase II, the most promising technologies identified in Phase I were studied in–depth through personal interviews with the engineers who research and apply these technologies, and through tours of laboratory models and full–scale installations. Phase III of the assessment effort culminated in the first forum on innovative domestic and international hazardous waste treatment technologies on June 19–21, 1989, in Atlanta, Georgia. The most successful full–scale technologies investigated were developed in the Netherlands and West Germany. These technologies include vacuum extraction of hydrocarbons from soil, in situ washing of cadmium-polluted soil, in situ steam stripping, and a number of landfarming and soil washing operations. The paper provides description of 11 soil remediation techniques that have shown such promise in laboratory studies or in practice to warrant consideration of their use in the United States, and summary information on the international technologies selected for presentation at the Phase III forum as they relate to soils remediation.

Adsorption of benzene from aqueous solutions by bentonite treated with quaternary amines

Abstract: The adsorptive properties of Wyoming bentonite, which has been tailored using various tetraalkylammonium (TAA{sup +}) ions, have been investigated for the selective removal of hazardous organic pollutants found in waters and soils contaminated by petrochemical spills. The effectiveness of the tailoring agents is evaluated by comparing the adsorption isotherms of benzene on both treated and untreated soils. Five TAA{sup +}-type compounds are investigated: ammonium (NH{sub 4}{sup +}), tetramethylammonium (TMA{sup +}), tetraethylammonium (TEA{sup +}), tetrapropylammonium (TPA{sup +}), and tetrabutylammonium (TBA{sup +}). The optimum dose characteristics are determined for each tailoring cation. The adsorption capacity of the treated clay decreases for doses that exceed the optimum dose because of the increase in organic content in solution, which induces a reduction in the partition coefficient between organically coated solid and the liquid phase. Despite the similarity in nature of the TAA{sup +} cations used in this study, significant differences in the adsorption capacities are obtained for the various compounds.

Performance of selected in situ soil decontamination technologies: An Air Force perspective

Abstract: Every year, the US Air Force stores and transfers three billion gallons of JP-4 jet fuel. Unfortunately, not every gallon of fuel has been consumed in flight. Fuel spills account for nearly half of the chemically contaminated sites on Air Force installations and that percentage is growing as underground storage systems are more closely inspected. The Air Force Engineering and Services Laboratory is responsible for developing and testing new and more cost effective technologies capable of cleaning up fuel spills in a variety of soil and groundwater conditions. Special emphasis has been placed on soil decontamination because their sampling data has confirmed that the majority of spilled fuel is adsorbed or occluded in the soil above the water table.

Prediction of activated carbon adsorption performance under high relative humidity conditions

Abstract: Humidity effects on carbon adsorption were investigated using five volatile organic compounds (VOCs). Relative humidities ranged from 54% to 92%. Under these high relative humidity conditions, the Dubinin–Polanyi equation was used to analyze the results of activated carbon adsorption capacity. Based on the Dubinin–Polanyi equation and the concept of a mass transfer zone, an adsorption kinetic equation was derived to predict the carbon adsorption (MTZ) velocity and the adsorbate concentration profile in the bed.

Overview of industrial source control for nitrogen oxides

Abstract: Contemporary debate over major clean air issues has kept the control of nitrogen oxides (NOx) in the forefront of public interest. While amendments to the Clean Air Act, new rules, programs, and policies emerge in response to concern for acid deposition, ozone non–attainment, global warming, and public health and welfare, it is anticipated that NOx control technology will be applied to a greater degree. However, existing regulations, policy and market forces are already forcing technologicaladvances. This article presents a summary of the current regulatory situation and looks ahead at the Clean Air act reauthorization. The article also presents an overview of stationary source control for NOx emissions.

Startup and opertion of an anaerobic biological activated carbon (AnBAC) process for treatment of a high strengh multicomponent inhibitory wastewater

Abstract: A joint study has been conducted by investigators at the State University of New York at Buffalo and Occidental Chemical Corporation to examine the feasibility of the anaerobic biologica activated carbon (AnBAC) process for treatment of a high strengh multicomponent inhibitory wastewater. The three principal components of the study waste are phenol, formaldehyde, and methanol. Bench–scale studies were conducted over a two-year period using 2.54 cm and 5.08 cm ID AnBAC columns. Based on the results of the bench–scale studies, organic contaminant removal of greater than 90 percent was achived at loading rates of 0.06 g COD/g GAC/day. Subsequently, the results from the bench–scale studies were used to design a pilot–scale AnBAC system which has been operating successfully for approximately ten months at Occidental Chemical Corporation's Durez Division plant in North Tonawanda, New York. The purpose of this paper is to present performance data from both the bench– and pilot–scale systems and identify startup procedures found necessary for successful initiation of AnBAC column operation. Based on the data collected, the AnBAC process is capable of providing excellent treatment performance of the high strength waste. Proper balancing between the applied organic loading rate and the process removal capacity was found to be crucial in maintaining a healthy biomass during column startup due to the inhibitory nature of the wastewater.

The effect of oxidants on UV destruction of chlorophenols

Abstract: Ultraviolet treatment is used for the destruction of refractory wastewater components. This paper addressed its application on the destruction of nonbiodegradable chlorophenols with the presence of different oxidants. The experiments were carried out in a batch photoreactor under various pH, dissolved oxygen (DO) time, and oxidant types and concentrations. Experimental result indicates that the dissolved oxygen levels has little effect on the destruction of chlorophenols by UV irradiation. The presence of some oxidants (e.g., H{sub 2}O{sub 2}) significantly increases the destruction efficiencies of chlorophenols by UV treatment. The reaction kinetics are studied and discussed. Proper reactor design is essential to the successful application of UV/oxidant treatment.

Biodegradation of chlorinated hydrocarbons in an immobilized bed reactor

Abstract: A 75 liter immobilized microbe biological reactor with a bed retention time of 20.5 hours was used in a continuous flow mode to remediate contaminated groundwater containing ethylene dichloride (EDC), tetrachloroethylene, and trichloroethylene, with EDC being the predominant contaminant. The reactor was initially seeded with Xanthobacter autotrophicus, a demonstrated halogenated aliphatic substrate utilizer. The reactor was operated for forty-two days. Material balance determinations for primary volatile aliphatics of concern indicated an average of 90.2% mineralization of EDC, 81.7% of the trichlorethylene (TCE) and 64.0% of the tetrachlorethylene (TeCE). In addition to Xanthobacter autotrophicus, four indigenous bacterial species from the groundwater had successfully acclimated to the reactor bed.

Groundwater treatment with zero air emissions

Abstract: Air emissions from the treatment of volatile organic compound (VOC) - contaminated groundwater are a growing problem in the US. Historically, air stripping has been used to remove VOCs from contaminated groundwater. Air stripping technology is a cross media treatment technique, i.e., it solves a groundwater problem by transferring contamination to the atmosphere. In response to the air pollution problem created by air stripping, the public, air quality regulatory agencies, the federal government and private industry are exerting pressure to eliminate and/or reduce air emissions from the clean-up of contaminated groundwater. These forces make it desirable to consider alternative and innovative technologies for the treatment of groundwater contaminated with VOCs.

PCB detoxification technologies: A critical assessment

Abstract: Management of PCBs under the Toxic Substances Control Act (TSCA) since promulgation of the first regulations in 1978 has cost industry and government over $1 billion. A significant portion of that expense has been associated with disposal of PCB liquids and PCB articles, ranging from routine PCB removal and replacement to disposal of debris from PCB spills and fires. Since the first PCB incineration permit was granted by the U.S. EPA in 1979, PCBs have also been one of the most expensive chemicals to dispose of commercially. High prices combined with the limited permitted disposal capacity has prompted scientists and engineers to continue the search for less expensive ways to detoxify PCB-contaminated material. Ironically, these factors have also driven the development of innovative technology for other less expensive waste streams that would otherwise have been passed over. The search for improved PCB detoxification technology continues as disposal capacity continues to shrink and PCB–related cleanups approach the remediation stage. This paper looks at the state of PCB detoxification technology, reviewing past and present technology development efforts and relating these technologies to the industry's remedial needs in the coming years.

Homogeneously catalyzed oxidation for the destruction of aqueous organic wastes

Abstract: Several organic species, specifically atrazine, 2,4-dichlorophenozyacetic acid, and biphenyl, were converted to CO{sub 2} and other non-harmful gases through oxidation catalyzed by inorganic acid. Nearly complete conversion was obtained through homogeneous liquid-phase oxidation with ammonium nitrate. The kinetics of reaction have been investigated and indicate parallel oxidation and thermal degradation of the oxidant. This results in a maximum conversion at an intermediate temperature. Increasing oxidant concentration accelerates the rate of conversion and shifts the location of the optimum temperature. Reaction at varying acid concentration revealed that conversion increased with an approximately linear relationship as the pH of the solution was increased. Conversion was increased to greater than 99% through the addition of small amounts of transition metal salts demonstrating the suitability of a treatment process based on this technology for wastestreams containing small quantities of heavy metals.

Cleanup of contaminated soils by pyrolysis in an indirectly heated rotary kiln

Abstract: The destruction of hazardous waste and cleanup of contaminated soils by pyrolysis in an indirectly heated rotary kiln system, followed by combustion of the volatiles in a secondary combustion chamber, has been tested in a pilot plant and demonstrated in an industrial scale plant. Deutsche Babcock Anlagen AG conducted comprehensive tests in a pilot plant with throughput rates of 0.5 to 1 ton/hour. following these tests, Deutsche Babcock designed and constructed the industrial scale demonstration plant with a throughput rate of 7 tons/hour for Bergbau Ag Westfalen near Dortmund, West Germany.

Performance models for NOx absorbers/strippers

Abstract: The focus of this paper is to present a review of recent developments in the modeling of NOx absorbers and strippers. The fundamental concepts of design and process simulation for this specialized area of mass transfer are developed. This review and conceptual analysis is intended to provide simple design/simulation equations and to present the usefulnessand limitations of these equations. This activity is useful because of the interrelationships between mass transfer and the complexity of the NOxHNOxH2O chemical system.

Modeling and simulation of bioremediation of contaminated soil

Abstract: A mathematical model has been developed for in situ biodegradation of contaminants in a soil bed. The model equations comprise three convection-dispersion partial differential equations and one ordinary differential equation. Dimensional analysis of the model equations has been performed, and solution of these equations has been conducted by the newly-developed three-point backward finite difference method. The effects of insufficient oxygen supply, growth of biomass and resistance to contaminant migration on the rate of biodegradation have been examined by numerically simulating the dynamic behavior of in situ biodegradation processes. The results of numerical simulation indicate that the rate of biodegradation of contaminants in soil may be constrained not only by insufficient oxygen supply, but also by resistance to contaminant migration within the pore network. The effect of recycling the unreacted contaminants from the bottom of the bed to the top has been examined through simulation, showing that biodegradation takes place mainly in the upper part of the bed.

Air stripping of volatile hydrophobic compounds using packed crisscross flow cascades

Abstract: The removal of four volatile organic compounds from aqueous solution by air stripping using a cascade crossflow device has been studied. This method of operation gave mass transfer coefficients and removal efficiencies quite similar to those achieved in conventional countercurrent operations. However, in terms of reduced pressure drops and greater range of stable operation, the advantages of the cascade crossflow device far outweigh those of the conventional countercurrent stripper.