Emerging Technologies for Hazardous Waste Management - ACS

Chapter 1

Emerging Technologies for Hazardous Waste Management Overview 1

D. William Tedder and Frederick G. Pohland

Downloaded by 80.82.77.83 on January 3, 2018 | http://pubs.acs.org Publication Date: August 2, 1991 | doi: 10.1021/bk-1991-0468.ch001

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School of Chemical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0100 Department of Civil Engineering, University of Pittsburgh, Pittsburgh, PA 15261-2294 1

International developments in recent years have resulted in rapid changes in the political climate, especially in eastern Europe. A new openness in the War saw Pact countries and the Soviet Union (U.S.S.R.) has revealed numerous smokestack industries still operating with 1940s technologies, and pollution problems that are no longer tolerated in the West (1-4). This new openness is also closing low-cost doors for Western waste disposal (5,6). Perhaps for the first time, the realities of industrialization without modern pollution control and waste management are recognized nearly worldwide; the clamor for im proved waste management and pollution abatement now echoes in regions that have long been silent. More than ever before, hazardous waste management is an international concern (7). With the apparent end of the cold war in sight, thoughts are turning toward the legacy of the arms race (8). Eyes are now focusing on the stark realities of dismantling large stockpiles of weapons, including significant inventories of chemical and biological agents of mass destruction. Agreements are already in place between the U.S. and the U.S.S.R. to reduce nuclear capabilities, and those of chemical and biological warfare, but the most appropriate manage ment technologies are still emerging. The costs of the cold war have been enormous, although the total costs may not yet be calculable. In a recent interview, for example, a Russian official made the casual observation that "the cost of producing chemical weapons is much less than the cost of safely destroying them" (anon., recent U.S. televised report). Clearly, these aging inventories of chemical and biological weapons cannot be ignored, and must be safely detoxified. Hazardous waste manage ment has significant economic ramifications. This volume addresses some of these problems, but necessarily focuses on a few approaches that are under development. Since these are emerging tech nologies and management techniques, neither process safety nor economic considerations are discussed in detail, although several contributions also in clude these factors. While both factors are important, additional research and 0097-6156/91/0468-0001$06.00/0 © 1991 American Chemical Society Tedder and Pohland; Emerging Technologies in Hazardous Waste Management II ACS Symposium Series; American Chemical Society: Washington, DC, 1991.

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EMERGING TECHNOLOGIES IN HAZARDOUS WASTE MANAGEMENT Π

development are needed before they can be assessed with acceptable levels of confidence.


Thermal Treatment and Abiotic Emissions Control In the U.S., hazardous waste incinerators and nuclear power reactors share the same dubious distinction. Much of the public perceives them as being risky, and both are subject to the "not in my backyard" or "NIMBY" syndrome. This perception is at least partly due to their respective potentials for generating airborne pollutants which may travel some distance from the generating site before deposition. Although technologies for the treatment of airborne emis sions are highly developed (9), there is public concern that harmful emissions will be generated and released to the environment. In certain instances, how ever, the most effective strategies for managing hazardous wastes will utilize thermal technologies; incineration will be unavoidable in some cases. Conse quently, the development of improved waste incineration methods and off-gas treatment technologies is essential. In Chapter 2, investigators from the Institute of Gas Technology in Chicago present a novel concept for utilizing internal radiant energy within a gas-fired combustion chamber to maintain higher combustion temperatures. This tech nology has been patented and appears important for the thermal destruction of many chlorinated species where removal efficiencies are highly dependent upon the combustion chamber temperatures and residence times. Short residence times are desirable to reduce the production of nitrogen oxides, but shorter residence times also require higher temperatures. Therefore, these promising results should prove significant in waste incineration. A second contribution describes fundamental studies using an electrodynamic balance (EDB) to measure single-particle desorption rates, a key phe nomenon for the design of thermal treatment of soils and solid residues. In Chapter 3, Stephanopoulos et al. present results for three types of solid particles—montmorillonite, and two synthetic chars with different pore struc tures. Significant differences were identified among the various solid-organic compound pairs examined in adsorption-desorption sequences in the EDB. Not surprisingly, these differences are related to the solid pore structures. Con tinuing studies should define minimal temperature requirements more pre cisely and enable the design of more efficient and controllable thermal treat ment processes. Jozewicz and Kirchgessner discuss lime treatment methods in Chapter 4 that can be used to maintain high reactivities for the removal of sulfur dioxide. This technology is important for emissions control from coal-fired boilers, but also has implications for the removal of acidic species from hazardous waste incinerator effluents. In particular, a small amount of SO2 in the calcination

Tedder and Pohland; Emerging Technologies in Hazardous Waste Management II ACS Symposium Series; American Chemical Society: Washington, DC, 1991.

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1. TEDDER & POHLAND Overview

gas yields a CaO that is more reactive with S 0 upon furnace injection than a CaO calcined in the absence of SO2. 2


Water Management Potential improvements in water management may result from better detoxi fication techniques through chemical reactions and purification. Groundwater pollution (e.g., from landfills and land-disposed leachates) remains a concern. It is increasingly difficult for generators to abandon wastes, and short-term ben efits must be weighed more carefully against long-term liabilities. The resulting polluted waters usually contain only trace levels of restricted species, but appro priate management is still required. Moreover, traditional methods are often ineffective and new treatment methods are needed to economically manage these wastes. Photochemical and ultraviolet (UV) treatment technologies are still being actively investigated and three contributions describe aspects of this important topic. In Chapter 5, Larson, Marley and Schlauch review the status and sev eral important applications. Light can promote the decomposition of dissolved pollutants by a variety of mechanisms. Although some classes of organic chem icals absorb sunlight strongly and are rapidly photolyzed in natural waters or wastewaters, for others, some means of indirect photodegradation is necessary. Classical sensitized photolysis with its singlet oxygen mechanism is probably of limited importance in water, but sensitizers such as riboflavin may be active toward compounds with which they can form light-absorbing complexes. Solar radiation can be concentrated and, in certain instances, effectively combined with catalysts to enhance destruction rates. Graham et al. de scribe laboratory and small-scale field studies in which thermal heating and U V radiation combine to provide enhanced destruction rates for 1,2,3,4tetrachlorodibenzo-/?-dioxin at temperatures below 800 °C. Products of incom plete combustion are formed with lower yields, and are destroyed at lower tem peratures than in conventional incinerators. It appears that a simultaneous ex posure to concentrated sunlight and high temperature can significantly increase pollutant destruction rates when compared to heating at similar temperatures alone. The relative merits of chemical treatment (e.g., H 0 or O3) vs photochemical-induced oxidation and reaction is of continuing interest. A number of papers relating to this topic were presented during the 1989 Sym posium (10) and additional contributions were received this year. Heeks et al. (Chapter 7) present a particularly interesting comparison of oxidation tech nologies conducted at the Xerox facility in Webster, N Y . The Ultrox, PeroxPure, and Rayox systems are all commercially available and were compared for their efficacy in destroying several common chlorinated solvents and toluene. 2

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EMERGING TECHNOLOGIES IN HAZARDOUS WASTE MANAGEMENT II

It was concluded that U V oxidation technology is applicable on a commer cial scale for groundwater purification. It was particularly effective in the de struction of toluene and unsaturated chlorinated solvents, but less efficient for the destruction of saturated chlorinated species such as dichloro- and trichloroethanes.


Water purification by solute separation and retention is another important option. The main problems with such technologies relate to the extremely low pollutant concentrations, the relatively high decontamination factors that are required, and the need to either regenerate or stabilize spent separating agents. Modeling capabilities are also needed to guide research and the selection of alternatives. Ion exchange technology represents one alternative that can be important, even for the removal of low pollutant concentrations. In multicomponent sys tems, competition may occur for active sites between the various solutes. This situation complicates the analysis and design. In Chapter 8, Robinson, Arnold and Byers present data and analysis techniques for such cases, using the sys tem Ionsiv IE-96 chabazite zeolite to remove ^Sr and Cs from wastewa ters containing parts per billion concentrations. Binary isotherms obtained by batch measurements were fitted using a modification of the Dubinin-Polyani model (11). 137

Chapter 9 includes a related ion exchange study by Hall, Watson and Robin son. Traditionally a batch unit operation, ion exchange can be operated contin uously. Higgins (12,13) developed one of the earlier designs. The present unit operates similarly, primarily for strontium removal. It offers substantially re duced secondary waste production rates compared to the available alternatives. These authors present their multicomponent equilibrium model, the use of the Thomas model for predicting breakthrough and their scaleup techniques.

The selection of wastewater treatment technology requires the evaluation of many parameters and costs. Such comparisons are usually lengthy, but can be shortened somewhat by the strategic application of spreadsheet-based com puter simulation programs. In Chapter 10, Counce et al. describe an economic model that can assist in the evaluation of volatile organic chemical (VOC) air-stripping options for treating groundwater. They clearly review the nec essary steps in such evaluations and explain its implementation into spread sheets. Their simulator consists of three general parts: (1) process design, (2) estimation of fixed capital and annual operating costs, and (3) operating life time analysis. This chapter is a useful reference and overview of the evaluation procedures. Their examples, jet fuel and trichloroethylene spills, illustrate the value of parametric methods.



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Biological Treatment The biological treatment of wastewaters and solids continues as an emerging technology (14,15), and four contributions are included in the present volume. Solids treatment, often referred to as "bioremediation," is finding many ap plications. One of the more effective methods for remediating oil spills, de veloped from the Exxon Valdez experience (16), is simply to add phosphate and nitrate fertilizers to the environment, and allowing naturally occurring mi croorganisms to metabolize the hydrocarbons (Lessard, R. R., I&EC Special Symposium Dinner Speaker, Atlantic City, NJ, 1990). Although microbiological processes involve incredibly complex chemistry, they are often surprisingly simple to implement and are cost effective. Biotech nology may frequently be the best choice, especially if the waste is not particu larly labile and time is not a limiting remediation consideration. Other factors, such as the average annual temperature and active growth period, may also determine overall effectiveness. In Chapter 11, Fernando and Aust describe the biodégradation of muni tions wastes using Phanerochaete chrysosporium, a white rot fungus. After 30 days incubation, about half of the C in their 2,4,6-trinitrotoluene (TNT) sam ples degraded to C 0 and only 3% could be recovered. Similarly, about two thirds of the initial hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX) concentra tion was converted to C 0 after the same incubation period. Ground corn cobs served as the nutrient for this fungus; soil cultures apparently degraded TNT and R D X at higher rates than liquid cultures. Pseudomonas has also been used to degrade TNT (27). Pseudomonas and Aceinomycetes are reported to degrade aromatics (18-21). Polycyclic aromatics and biphenyls are degraded by Phanerochaete chrysosporium (22,23). In Chapter 12, Utgikar and Govind discuss the use of a biofilter to control volatile organic chemicals. They present a mathematical model and summary calculations for 90% V O C removal. Their approach utilizes a countercurrent packed column (or trickle bed filter) to transfer VOCs from the air to a liquid phase. A microbial culture is attached to the packed column (e.g., activated car bon) and nutrients are provided through recirculation of the liquid phase which is introduced into the top of the packed column. Experimental data are pre sented for the removal of toluene and methylene chloride. They used biomass (a mixed culture) from an activated sludge plant that had been acclimated to toluene and methylene chloride. A third experimental study of biodégradation is presented by Havens and Rase in Chapter 13. They examined the use of an enzyme, parathion hydrolase, derived from an overproducing strain of Pseudomonas diminuta. This enzyme was partially purified and immobilized on several rigid supports, several con trolled pore glasses and a beaded polymer. These supports were compared with respect to parathion degradation; the hydrolase attacks the phosphoryl oxygen. 1 4

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The immobilized enzyme was capable of reducing the concentrations of several organophosphorous pesticides to levels below 1 ppm. In Chapter 14, Baltzis, Lewandowski, and Sanyal present a mathematical model for describing biological denitrification in a sequencing batch reactor. Their model assumes noninhibitory kinetics for nitrate reduction, inhibitory ki netics for nitrite reduction, and incorporates possible toxicity effects of nitrite on the biomass. It has been successful in qualitatively describing experimental data from a 1200-gallon pilot unit. Not surprisingly, sensitivity analyses indi cate that kinetic parameters have the greatest impact on reactor performance. They demonstrate how their model can be used to select operating parameters; results are currently being applied to the design of a larger unit for treating mu nitions wastes.

Solid Waste Management The disposal of solid wastes is often considered the alternative of last resort. Appropriately, more emphasis is being placed on waste minimization and pro cess modifications that avoid waste production altogether. Moreover, efficient processes that minimize waste production are essential to maintain a competi tive posture. In the meantime, substantial inventories of hazardous solids must be sta bilized and eliminated. Superfund sites are perhaps the most widely discussed and represent the most significant potential risks, but landfills are much more pervasive and many contain low concentrations of hazardous materials from illegal or unregulated practices. Thus, stabilization is a common problem at hazardous waste sites and landfills, and with mine tailings. It is appropriate to overview the state-of-the-art with respect to solidifica tion and waste stabilization. Chapter 15 provides a starting point for this last section in the book. Much of the impetus results from the Resource Conser vation and Recovery Act, the Comprehensive Environmental Response, Com pensation and Liability Act and the Superfund Amendments and Reauthoriza tion Act. Ultimately, these legislative actions translate into economic reali ties that must be faced by the waste generators, primarily those who are in timately involved with manufacturing. While stabilization is often effective, Bishop points out that not every waste can be stabilized. A number of fac tors (e.g., p H and redox potential) may affect the leachabilities of the resulting waste forms. At one extreme, borosilicate glasses are contemplated for highlevel fission product wastes. At the other extreme, minimal treatment, such as immobilization in a pozzolan-based cement, is proposed. In Chapter 16, Chawla et al. overview a related issue, the interactions be tween soils, contaminants, and surfactants. This topic is particularly important whenever soil washing is contemplated (20). Soil matter can bind with organic




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pollutants through various physical and chemical interactions. Adsorption, hy drogen bonding, and ion exchange can all be important. The interactions be tween a soil, the contaminant, and any surfactant that is considered for soil washing are of paramount importance. The chemistry of species migration is complex and site-dependent. This consideration has long been a dominant consideration in radioactive waste management and in the selection of a federal repository for high-level waste disposal. In the long-term, it is necessary to avoid water and seek highly ad sorbent geologic formations. In the short-term, much useful information can be obtained from transport studies in real time. In Chapter 17, for example, Sandhu and Mills examine the mechanisms of mobilization and attenuation of inorganic species in coal ash basins. The site is the Savannah River Plant, a well-known plutonium production facility, but also a generator of ash from coal-fired power generation. Sediment cores, collected from ash basins of var ious ages, were sectioned and analyzed to elucidate the mobilization mecha nisms. There were significant releases and mobilization of most elements to the lower horizons of impounded ashes; this effect was most pronounced in the old basin. Low pH, generated by decomposing organic matter, appears partly responsible, but complexation by organic ligands may also play a role. In Chapter 18, Doepker discusses a similar finding at mine sites where soils close to metal smelters have elevated concentrations of lead, cadmium, copper, zinc and other heavy metals. Acetate ion (e.g., ammonium acetate at a pH of 4.5) effectively mobilizes cadmium and, to a lesser extent, zinc and lead. Although the western soil conditions are quite different from those in South Carolina, acidity and pH are key factors in metals leachabilities. Soil venting is another important method for site remediation that is finding many applications. It is broadly accepted for soils contaminated with volatile or semivolatile species. It is complicated, however, by a need to understand the site hydrology and air flow in some detail. In Chapter 19, Kuo et al. describe a three-dimensional soil venting model that can be used to understand a site and develop venting strategies. Their predictions are compared with experimental measurements at several remediation sites. While much has been said about fixation, there are many species requiring immobilization and innumerable matrices and constraints affecting the prob lem. Chu et al., for example, compare fixation techniques for soil containing arsenic in Chapter 20. The waste soils contained from 1200 to 2100 mg/kg. They compared Portland cement, fly ash, silicates, and ferric and aluminum hydrox ides, and found that silicates were most effective in reducing arsenic leaching rates. Low-level radioactive waste disposal is discussed by Darnell et al. in Chap ter 21. In particular, they analyze the long-term structural and radiological performance of abovegrade earth-mounded concrete vaults. Vault and grout waste degradation are modeled over extended time periods using computer


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codes. The resultant radiological doses are calculated. They conclude that this disposal strategy will satisfy the performance objectives set by the U.S. Depart ment of Energy.


Summary The emerging themes for rational waste management strategies are relatively straightforward. Toxic materials, once created, must either be detoxified or effectively isolated from the environment. The complexities lie primarily with technology selection issues, process integration, and practical constraints (e.g., costs). In many instances, the best strategy may be to avoid waste production or reduce generation rates by modifying the manufacturing processes. While combustion technologies have the potential for dispersing hazards and increasing effective population doses, rational long-term management pre cludes the disposal of thermally or chemically unstable waste forms. Intuitively, the preferred waste forms are those which are thermodynamically stable. The complexities begin with selecting conversion technologies (e.g., chemical vs. thermal or combustion). Many wastewater problems result from the presence of exceedingly low pollutant concentrations. The common challenge is to find effective technolo gies for removal and concentration before detoxification. In this regard, lowtemperature oxidation technologies [either chemical, photochemical, or other water irradiation techniques (24)] continue to attract considerable attention from numerous investigators. They are a continuing theme in this volume as well as its predecessor (10). The use of biological systems for waste treatment is another strategy that is clearly emerging, and the possibilities seem as varied as the number of mi croorganisms one may employ. As demonstrated by contributions in this vol ume, gaseous, liquid, and solid wastes may be treated using bioengineering techniques. While many of these methods can be complex, they can also be surprisingly simple. Increasingly, they are perceived as affordable, but bioremediation may also be slow. Thus, they are emerging as mid- to long-term treatment options. Species migration and waste solidification must often be considered con comitantly. Thermodynamic stability is a primary concern in both instances, and this subject has not been adequately discussed, especially with respect to complex matrices such as contaminated soils. Of course, pH plays a key role and, as noted previously (10), species are more labile in acidic, rather than in basic media. Redox potential is also important for species undergoing valence changes; reducing conditions generally seem to make immobilization more fa vorable.



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Literature Cited 1. Siuta, J. State, conditions and indispensable activities in the sphere of environmental protection. Ζ Nauk Polit L Bud, 40:5-23, 1988. 2. Ziegler, C. E . Bear's view: Soviet environmentalism. Technol Rev, 90(3):44-51, April 1987. 3. Bazell, R. Science and society: red forest. New Republic, 198(2):11, May 3, 1988. 4. Colchester, N . Industrial waste. The Econ, 315(2):PS12, June 30 1990. 5. Simons, M. In Leninallee, cans, bottles and papers: it's the West's waste! New York Times, 139, July 5 1990. 6. East European loss will boost E C waste market. Euro Chem News, 55(1):P20, July 23 1990. 7. West assists East with pollution programme. Euro Chem News, 53(1):P14, Nov 13 1989. 8. Marshall, E. Radiation exposure: hot legacy of the cold war. Science, 249(1):474, Aug 3 1990. 9. Goossens, W. R. Α., Eichholz, G. G., and Tedder, D. W., editors. Treatment of Gaseous Effluents at Nuclear Facilities. Volume 2 of Radioactive Waste Management Handbook, Harwood Academic Publishers, New York, 1991. 10. Tedder, D. W. and Pohland, F. G., editors. Emerging Technologies in Haz ardous Waste Management. Volume 422 of ACS Symposium Series, Amer ican Chemical Society, Washington, DC, 1990. 11. Ruthven, D. M. Principles ofAdsorption and Adsorption Processes. John Wiley & Sons, New York, 1984. 12. Higgins, I. R. Countercurrent liquid-solid mass transfer method and ap paratus. U.S. Patent No. 2,815,322, Dec 3, 1957. 13. Long, J. T. Engineering for Nuclear Fuel Reprocessing. American Nuclear Society, La Grange, IL, 2nd edition, 1978. 14. Forgie, D. J. L . Selection of the most appropriate leachate treatment methods. Part 1: A review of potential biological leachate treatment methods. Water Pollut Res J Can, 23(2):308-328, 1988. 15. Lee, M. D., Thomas, J. M . , Borden, R. C., Bedient, P. B., and Ward, C. H . Biorestoration of aquifers contaminated with organic compounds. CRC Crit Rev Environ Con, 18(1):29-89, 1988. 16. Lee, D. B. Tragedy in alaska waters. National Geographic, 176(2):260-263, August 1989. 17. Selivanovskaya, S. Y., Gorkunova, T. A., and Naumova, R. P. Effect of clay on aerobic bacterial decomposition of trinitrotoluene. Sov J Water Chem Tech (Eng Trans Khim Tekn Vo), 9(1):31-34, 1987. 18. Inoue, A . and Horikoshi, K. A pseudomonas thrives in high concentra tions of toluene. Nature, 388:264-266, 1989.



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19. Zimmermann, W. Degradation of lignin by bacteria. J. Biotech, 13(23):119-130, Feb 1990. 20. McDermott, J. B., Unterman, R., Brennan, M . , Brooks, R. E., Mobley, D. P., Schwartz, C. C., and Dietrich, D. K. Two strategies for PCB soil remediation: biodegradation and surfactant extraction. In Proc AIChE Nat Meeting, New York, 1988, American Institute of Chemical Engineers, New York, 1988. 21. Johnston, J. B. and Renganathan, V. Production of substituted catechols from substituted by a Pseudomonas. Enzym Microb Tech, 9(12):706-708, Dec 1987. 22. Eaton, D . C. Mineralization of polychlorinated biphenyls by Phanerochaete chrysosporium: a ligninolytic fungus. Enzym Microb Tech, 7:194196, 1985. 23. Bumpus, J. A. Biodegradation of polycyclic aromatic hydrocarbons by Phanerochaete chrysosporium. Appl Envir Microb, 55:154-158, 1989. 24. Fleming, R. W. and Tedder, D. W. Water purification by radiation induced oxidation (thesis excerpts). J Env Sci Health, A25(4):425-446, 1990. RECEIVED April 5, 1991


Emerging Technologies for Hazardous Waste Management - ACS

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