10
Technology Comparisons

How the Comparison Criteria were Derived

This chapter provides a succinct account of how the five technologies discussed in Chapters 4 through 8 compare with one another. As noted in Chapter 2, the panel began the process of deriving these criteria by adopting three of the four critical factors identified and applied by the NRC Stockpile Committee in its Criteria Report Evaluation. The panel adapted those factors and the associated subfactors for use in the questionnaire sent to the technology TPCs and the Army (Chapter 3). The panel also used them to set the agenda for meetings with community groups and regulators (Chapter 9). From the questionnaires and meetings, the panel learned which aspects of the original factors were most important for characterizing and differentiating among the technologies selected for review and which were most important for expressing community concerns or regulatory issues. The panel has abstracted the most relevant aspects of the original factors and reorganized them to emphasize issues and relative differences that the panel believes are most important for supporting decisions on pilot demonstration of one or more technologies. These decisions may lead to operational implementation of an alternative agent destruction technology at one or both of the bulk-storage sites.

Some of the evaluation subfactors presented in Chapter 2 are important but are satisfied almost equally by all the technologies selected for the panel's review. An important example is the capacity to destroy agent. All TPCs supplied test results to the panel indicating that they had successfully destroyed both HD and VX. Because of time constraints, the panel was not able to do an in-depth review or analysis of the data from these important tests. The panel emphasizes that these tests were conducted under conditions that varied from conditions in a pilot-scale or fully operational facility. In addition, the tests for different technologies were not conducted under comparable conditions. Thus, it is inappropriate to infer that the particular DREs (destruction removal efficiencies) attained in these tests would be attained in an operating facility or to compare technologies on the basis of the number of 9's in the DREs calculated from these tests. Consequently, the panel has used the DRE results only to ascertain, in yes-or-no fashion, whether the technology can destroy agent. Because all the technologies have successfully demonstrated that they can destroy agent, this extremely important criterion is not included in the comparison criteria below. For a given technology, the total time to destroy agent at each site is covered under Implementation Schedule.

The next section describes the criteria for comparison as they emerged from the panel's deliberative process. Then, each of the five technologies is assessed with respect to the criteria.

The Comparison Criteria

The panel has continued to use three headings to organize comparison criteria into groupings that are similar but not identical to groupings used in the NRC Criteria Report Evaluation. The headings used here are Process Performance and Engineering; Safety, Health, and the Environment; and Implementation Schedule. Some subfactors that had been located under the old heading of Process Efficacy appear among the criteria for Safety, Health, and the Environment to emphasize their relevance to those issues rather than to a narrower, process-engineering evaluation of a technology. Other subfactors are included under Implementation Schedule to emphasize community concerns and acceptance. The following brief descriptions of the criteria are intended to orient them with respect to the discussions in Chapters 2 and 9 and to indicate why the panel considers each criterion relevant for comparing the alternative technologies.

Process Performance and Engineering

This heading includes two comparison criteria taken from the Process Efficacy section of Chapter 2:



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--> 10 Technology Comparisons How the Comparison Criteria were Derived This chapter provides a succinct account of how the five technologies discussed in Chapters 4 through 8 compare with one another. As noted in Chapter 2, the panel began the process of deriving these criteria by adopting three of the four critical factors identified and applied by the NRC Stockpile Committee in its Criteria Report Evaluation. The panel adapted those factors and the associated subfactors for use in the questionnaire sent to the technology TPCs and the Army (Chapter 3). The panel also used them to set the agenda for meetings with community groups and regulators (Chapter 9). From the questionnaires and meetings, the panel learned which aspects of the original factors were most important for characterizing and differentiating among the technologies selected for review and which were most important for expressing community concerns or regulatory issues. The panel has abstracted the most relevant aspects of the original factors and reorganized them to emphasize issues and relative differences that the panel believes are most important for supporting decisions on pilot demonstration of one or more technologies. These decisions may lead to operational implementation of an alternative agent destruction technology at one or both of the bulk-storage sites. Some of the evaluation subfactors presented in Chapter 2 are important but are satisfied almost equally by all the technologies selected for the panel's review. An important example is the capacity to destroy agent. All TPCs supplied test results to the panel indicating that they had successfully destroyed both HD and VX. Because of time constraints, the panel was not able to do an in-depth review or analysis of the data from these important tests. The panel emphasizes that these tests were conducted under conditions that varied from conditions in a pilot-scale or fully operational facility. In addition, the tests for different technologies were not conducted under comparable conditions. Thus, it is inappropriate to infer that the particular DREs (destruction removal efficiencies) attained in these tests would be attained in an operating facility or to compare technologies on the basis of the number of 9's in the DREs calculated from these tests. Consequently, the panel has used the DRE results only to ascertain, in yes-or-no fashion, whether the technology can destroy agent. Because all the technologies have successfully demonstrated that they can destroy agent, this extremely important criterion is not included in the comparison criteria below. For a given technology, the total time to destroy agent at each site is covered under Implementation Schedule. The next section describes the criteria for comparison as they emerged from the panel's deliberative process. Then, each of the five technologies is assessed with respect to the criteria. The Comparison Criteria The panel has continued to use three headings to organize comparison criteria into groupings that are similar but not identical to groupings used in the NRC Criteria Report Evaluation. The headings used here are Process Performance and Engineering; Safety, Health, and the Environment; and Implementation Schedule. Some subfactors that had been located under the old heading of Process Efficacy appear among the criteria for Safety, Health, and the Environment to emphasize their relevance to those issues rather than to a narrower, process-engineering evaluation of a technology. Other subfactors are included under Implementation Schedule to emphasize community concerns and acceptance. The following brief descriptions of the criteria are intended to orient them with respect to the discussions in Chapters 2 and 9 and to indicate why the panel considers each criterion relevant for comparing the alternative technologies. Process Performance and Engineering This heading includes two comparison criteria taken from the Process Efficacy section of Chapter 2:

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--> (1) technology status and (2) stability, reliability, and robustness. Table 10-1 summarizes basic engineering data for each of the evaluated alternatives, including general process description, operating conditions, and the fate of the elements from destroyed agent (that is, the form of the process residuals containing elements from the agent). Technology Status Except for neutralization, none of the alternative technologies has been used on a significant scale to destroy chemical agent. Only incineration and neutralization technologies have been used on agent at practical scales. However, for other wastes, the status of the technology varies from laboratory-scale to full-scale commercial operation. Furthermore, pilot designs must be sufficiently documented in TPC submissions to enable an assessment of hazard inventory and intrinsic safety. Incomplete designs required the panel either to apply its best "engineering judgment" based on the information provided or to state that significant uncertainties remain with respect to the technology's ability to meet cross-cutting requirements or to achieve the claimed capabilities. Stability, Reliability, and Robustness Processes that function effectively and reliably are desired. Such processes minimize unit operations, use proven components, and can be constructed from materials that are compatible with residual streams and with process conditions—including startup, shutdown, and emergency response. Frequently these processes have slow reaction rates, are operated at low temperature and low pressure, and are simple to operate and control. Although slow reaction rates are perhaps more reliable and less prone to process upsets, they may also imply greater costs because they require longer agent destruction campaigns. Slow reaction rates may also increase storage risk because the stockpile remains for a longer time. Safety, Health, and the Environment The panel identified five criteria under this heading as important for differentiating among the alternative technologies or for addressing issues of major importance to decision-making. The criteria are safety interlocking, hazard inventory, test prior to release, environmental burden, and worker safety. Safety Interlocking The safety interlocks should be simple and proven. Process monitoring that can tolerate long time constants for appropriate response is safer and contributes to steadier plant operations, with fewer unnecessary stoppages for false alarms than monitoring that requires immediate response. For example, monitoring that would stop operations as a result of a momentary anomaly such as a temperature spike is less desirable than monitoring that responds only after the elevated temperature has been detected for a longer duration. Under the latter condition, a true process upset is more likely to exist. Also, a plant becomes inherently safer when its safety performance depends less on add-on devices and more on safety interlocks that are integral to the plant design. Hazard Inventory The potential for a process upset or failure seriously affecting human health or the environment increases as the inventory of hazards increases. Relevant hazards include the quantity of agent, the quantities of other reactive or toxic materials (feed materials, intermediates, and process residuals), the presence of acids or combustible gases, thermal energy, and pressure. The potential for material failures can be assessed on the basis of characteristics of the feed and residual streams integral to the processes; examples include the localized corrosion of even highly alloyed materials, stress corrosion cracking, hydrogen embrittlement, and fatigue from stress cycling. Proper selection of materials of construction will be more difficult for some technologies, those that require high temperature corrosive environments, for example, than for others. Test prior to Release Members of the public have indicated a strong preference for batch processes or end-of-process operations that allow for the sampling and analytical testing of all process residuals prior to discharge (see the discussion of "closed loop" processes in Chapter 9). In general, a

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--> TABLE 10-1 Process Engineering Data for Alternative Technologies Engineering Parameter Catalytic Extraction Processing Mediated Electrochemical Oxidation Gas-Phase Chemical Reduction Neutralization of HD (Configurations 1, 2, 3) Neutralization of HD Configuration 4) Neutralization of VX Process Description             Medium of Treatment molten iron or nickel 8 M nitric acid Gas-phase H2 and steam hot water hot water 33% aqueous NaOH Batch or Continuous continuous semibatch continuous semibatch semibatch semibatch Operating Conditions             Process Temperature (°C) 1600 90 (max) 850 90 90 90 Process Pressure <10 atm. at injection; 12 atm above bath near atmospheric near atmospheric (slight positive pressure) near atmospheric near atmospheric near atmospheric No. of Unit Operations >12 10 >10 7 (config. 1) to 5 (config. 3) on-site 2 on-site 3 on-site Electrical Power (kW·h/1000 kg) 7,400 net (HD), 25,000 excluding cogeneration 72,600 (HD) 134,900 (VX) 1,020 99,000 (conf. 1) to 23,000 (config. 3) 13,600 8,000 Fate of Agent: Ultimate Form (kg/1,000 kg agent)a Carbon in HD 705 kg CO from HD; 166 kg CO from CH4 cofeed 1,100 kg CO2 30 kg C soot; remainder CO2b 163 kg biosolids 4,563 kg CO2 67-77 kg organics 624 kg thiodiglycol 125 kg other hydrolysis products Sulfur in HD 201 kg elemental S 900 kg Na2SO4 201 kg elemental S 799 kg Na2SO4 67-77 kg organics 163 kg biosolids 624 kg thiodiglycol   Chlorine in HD 460 kg HCl 750 kg NaCl 460 kg HCl 747 kg NaCl 715 kg NaCl; remainder in other hydrolysis products   Carbon in VX 1,152 kg CO from HD; 136 kg CO from CH4 cofeed 1,900 kg CO2 52 kg C soot, remainder CO2     463 kg EMPA-Na 49 kg MPA-2Na 931 kg S/P/N organics Phosphorus in VX 116 kg P in iron alloy 600 kg Na3PO4 326 kg H3PO3c     554 kg P-containing organics Sulfur in VX 120 kg S in alloy 550 kg Na2SO4 127 kg elemental S     864 kg S-containing organics Nitrogen in VX 52 kg N2 in offgas 300 kg NaNO3 56 kg N as N2/NH3     828 kg N-containing organics a The elemental composition of 1,000 kg of HD is 302 kg of carbon, 50.3 kg of hydrogen, 201 kg of sulfur, and 446.5 kg of chlorine. The elemental composition of 1,000 kg of VX is 494 kg of carbon, 97 kg of hydrogen, 116 kg of phosphorus, 120 kg of oxygen, 120 kg of sulfur, and 52 kg of nitrogen. b Total carbon for GPCR includes carbon from natural gas reformed to CO and H2, as well as carbon from agent. c Appearance of phosphorus as H3PO3 or its salts is hypothesized by the panel as the most likely product from the reactor, based on thermodynamics. The actual P-containing process residuals from GPCR have not been demonstrated.

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--> hold-and-test operation prior to release is more readily implemented for liquid and solid residuals than for gaseous residuals. Environmental Burden Processes can vary greatly in the composition and quantity of process residuals produced during agent destruction operations. These residuals, whether in a gaseous, liquid, or solid waste stream, will ultimately be discharged into the environment. The focus should be on minimizing the overall environmental burden (composition and quantity) resulting from an agent destruction technology. Worker Safety Plant safety and health risks are of particular concern to workers directly involved in agent destruction operations. The risk of worker exposure to agent or other hazards is a function of technology maintenance requirements, the degree of process automation, the duration of destruction campaigns, the quality of in-plant monitoring, and the intrinsic safety of the technology. Implementation Schedule The panel identified four criteria under this heading by which the alternative technologies could be assessed for their potential impact on the implementation schedule for stockpile destruction at Aberdeen and Newport. The four criteria are technical development, processing schedule, permitting requirements, and public acceptance. These four factors can interact in various ways to shorten or lengthen the overall schedule. Technical Development The alternative technologies under evaluation are at various stages of design, development, and demonstration. The time for each of them to reach pilot plant status will vary, thus affecting the overall schedule. The technology status, as discussed above, has a direct impact on the time to reach pilot plant status. This criterion considers the likely implications of technology status on the implementation schedule. Processing Schedule The size of the plant, the agent processing rate, and consequently the duration of the agent destruction campaign at a given site will vary from one technology to another. Permitting Requirements A major component of implementation for any technology is obtaining the necessary regulatory approvals and permits, particularly RCRA permits. Lack of complete information can considerably increase the time required. Regulators familiarity with and ability to comprehend the details of a technology can affect the RCRA permitting process. Community and governmental receptivity to a proposed technology can also influence the speed of the process. Public Acceptance Public acceptance of a technology can speed up regulatory decision-making. Public opposition, even by a small but determined minority, can impede implementation at many stages through litigation, extending regulatory timelines, seeking legislative redress, and other delaying actions. Public acceptance results from a program that involves affected communities meaningfully in the decision process and from decisions that reflect, at the very least, the factors the public believes are most important. For example, the selection of a technology that is capable of treating a wide range of industrial and military wastes is a concern of the communities around the agent stockpile sites. Although current law precludes other uses of an agent destruction facility, community members fear that the facility may be used to treat wastes imported from elsewhere. Hence, technologies that are designed to treat specific agents or are otherwise not available for other uses are more acceptable to the public than technologies with wide applicability. Summary of Key Comparative Differences Table 10-2 summarizes the discussions below of how the AltTech panel evaluated each alternative technology

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--> with respect to the 11 comparison criteria. Unless otherwise noted, table entries apply to both HD at Aberdeen and VX at Newport. The table provides a quick overview of the panels evaluations, with emphasis on the differences among them. However, table entries must be interpreted not only in the context of the summary evaluations in the remainder of this chapter but also in light of the detailed analyses of the technologies in Chapters 4 through 8 and the discussion of public concerns and permitting requirements in Chapter 9. Readers are urged to study these more detailed presentations so they can better understand the table entries. Catalytic Extraction Processing Process Performance and Engineering Technology Status The following points support the panels evaluation of this technology as being ready to begin commercial operation. The CEP technology has had more than 15,000 hours of testing to date. More than 12 bench-scale units have been operated, and two commercial-scale demonstration units are in operation. A third commercial-scale demonstration unit is scheduled to start operation in the summer of 1996. Commercial units are ramping up to full-scale operation at two sites in Oak Ridge, Tennessee, for volume reduction of low-level radioactive wastes. Stability, Reliability, and Robustness CEP is an example of a complex process that has been engineered to provide a high level of stability and reliability despite its inherent complexity. It uses proven components that are tightly integrated into a continuous process with numerous unit operations. For HD destruction, the unit operations include modules for the recovery of hydrogen chloride and sulfur. The panel believes the materials of construction are compatible with the process streams that will be involved in HD or VX destruction. For example, the design and materials selection for refractories are based on an intensive development program. However, decision-makers and other concerned parties should note that the reactors operate at high temperature (1425 to 1650°C) and that the agent is injected into the reactor at moderately high pressure (less than 10 atmospheres). Safety, Health, and the Environment Safety Interlocking Because CEP consists of numerous unit operations that are tightly integrated in a continuous process, a high degree of integrated process control and safety interlocking is required. Commercial-scale demonstration units have proven control systems, including safety interlocks. Two commercial-scale units designed for treating low-level radioactive waste have been started and are ramping up to full-scale operation. Process control loops and control logic, including process monitoring, have been proven. The panel believes the response times demonstrated for the monitoring and control system are adequate for safe operation with HD or VX. Hazard Inventory The primary hazard inherent in the CEP system is the energy stored in the high temperature molten metal baths. The integrity of the refractory confinement and the proximity of the molten bath to water cooling become important safety considerations. Because these issues have been addressed by the TPC, it appears the hazard inventory does not present an insurmountable impediment to the safety of the process. The combustible offgas and the agent are also part of the hazard inventory. Prior to the introduction of agent to the reactor, the quantity of agent is identical for all the alternative technologies. The TPC plans to operate the baths in agent destruction facilities with operators at a remote location. For HD destruction, the process includes proven, commercially available modules for recovering hydrogen chloride and sulfur (acid-management operations). Test prior to Release Although CEP is a tightly integrated continuous process, the TPC has provided for gaseous residuals

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--> TABLE 10-2 Summary of Comparison Criteria for VX at Newport and HD at Aberdeen Comparison Criterion Catalytic Extraction Electrochemical Oxidation Gas-Phase Reduction Neutralization Process Performance and Engineering Technology status VX and HD destruction demonstrated at bench-scale. VX and HD destruction demonstrated at bench-scale. VX and HD destruction demonstrated at laboratory-scale. VX and HD destruction demonstrated at bench-scale.   Entering commercial operation for low-level radioactive waste. No commercial or pilot-scale operation for other wastes. Applied commercially (full-scale) to chlorine-containing organics. For VX, low toxicity/burden of hydrolysate or treatability needs validation.       For VX, phosphorus-containing products and subsequent scrubbing yet to be determined.   Stability, reliability, robustness Proven components tightly integrated into a well-controlled process. Easily controllable oxidation at very low agent concentrations Several (³ 10) proven unit operations that require tight integration. No strongly exothermic reactions. Low temperature, low pressure semibatch process. Standard equipment. Safety, Health, and the Environment Safety interlocking High degree of integrated process control and safety interlocks are required and have been developed. Minimum interlocking required; reactions can be stopped easily by shutting off power. High degree of integrated process control and safety interlocks are required; high temperature hydrogen; temperature and pressure control are critical. Because of interstage storage, minimal interlocking required. Concentrated sodium hydroxide. Hazard inventory Agent under pressure in delivery system. A high temperature, moderately high pressure process. High thermal mass. Combustible and reactive offgases. Large volume of reactive reagents (HNO3, H2O2, NaOH). High temperature agent and combustible gas. Difficulty of preventing buildup of hydrogen and containing agent within a building.     For HD, large volume of toxic by-product H2S.   For HD, large volume of toxic by-product H2S.   Test prior to release Provision made for testing gases prior to combustion. Solids and liquids can be tested before shipment. Combustion gases released without analysis through stacks. All aqueous and solid residual streams can be tested prior to release. Gases treated extensively prior to release. All product streams can be stored and analyzed before release. Combustion gases released without analysis through stacks. Main (aqueous) waste stream is tested. Environmental burden Relatively low because of high degree of recycling, especially if synthesis gas-to-energy is considered recycling. Released residuals are common gases or salts in their most stable forms. Low. Sulfur recycled. HCl and/or NaCl in stable, disposable, or recyclable form. State and disposition of all secondary wastes must still be defined. For HD, aqueous discharge contains salts (NaCl, Na2SO2). Biomass. For VX, same as HD except aqueous discharge also has Na3PO4.

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--> Comparison Criterion Catalytic Extraction Electrochemical Oxidation Gas-Phase Reduction Neutralization Worker safety Process is complex but well developed. Preliminary FMEA indicates process meets safety standards. Low temperature and low pressure. Requires handling reactive chemicals. Hazard analysis for chlorine wastes developed. Analysis of more complex recovery/scrubbing systems required for agent. Low temperature and pressure. Mild caustic. HD configs. 1 and 2 have H2O2. Implementation Schedule         Technical development For HD, advanced. For VX, advanced but not as far as for HD. Appears to be straightforward, but technology least developed of those evaluated and much engineering development remains to be done. Advanced. Well developed process for destroying organic wastes. For VX, phosphorus-containing products need to be determined. Integration of phosphorus recovery into process not demonstrated. HD: 60% design status. Ready for permit application. VX: 60% design status. 6 months to resolve toxicity/treatability of hydrolysate. Processing schedule Approximately one year to destroy agent at each site, after systemization. Operations at Newport will not begin until Aberdeen activities are completed. Controlled by number of modules in facility. For each site, approximately one year to construct and systematize, one year to destroy stockpile. 15 months to systemization. Less than one year to destroy stockpile, operating at full-rate. Permitting requirements Current documentation adequate for timely review (unclear whether RCRA permit required). Process novelty could lengthen permit review time. Full-scale facilities permitted outside U.S. Permitting strategy submitted to panel. Regulators indicate technology would take the least time to permit. Public acceptance Attractive if seen as recycling. High temperature and pressure not attractive to public. Stack emissions may be a concern. BDAT designation for incinerable wastes may be positive (proven technology) or negative (versatile for other wastes). Meets key preferences of public: low temperature, atmospheric pressure, closed loop. Perceived as a closed loop system with provision for testing before release. Low pressure but high temperature. Hydrogen may be perceived as a risk. Stack emissions may be a concern. Concern about Army management of the technology. Low temperature and pressure. Closed loop batch process. Testing before release. CACs favor it. Agent-specific, not easily applied to other wastes.

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--> (synthesis gas) to be held for analytical testing prior to combustion. The products of combustion, however, are not tested prior to release to the atmosphere. Metal, sulfur, and ceramic process residuals are solids and will be tested prior to shipment off-site. Recovered HCl will be tested prior to shipment off-site. Process cooling water will be tested. Environmental Burden The TPC proposes to minimize the environmental burden by producing metal, HCl, and elemental sulfur as by-products that will be offered on the commercial market for reuse. The technical and economic feasibility of marketing these by-products is yet to be established. The process design also includes burning the offgas, which is rich in H and CO, in a gas turbine to generate electricity for in-plant use. The ceramic slag will require disposal. Worker Safety Although CEP is complex, the panel judges it to be robust enough and sufficiently developed that worker safety and health risks are satisfactorily low. A preliminary FMEA (failure modes and effects analysis) based on the conceptual design for destroying chemical agents has not revealed any unacceptable or abnormal risks. Implementation Schedule The TPC provided the panel with a detailed schedule. The panel judges this schedule to be reasonable for the complete destruction of the stockpiles at Aberdeen or Newport by 2004, provided there are no unforeseen delays. Technical Development Development efforts by the technology developer and the TPC are sufficiently advanced that, as of May 1996, they were ramping up to commercial operation of a facility (see Technology Status). The panel views this and the other status factors as a strong indication that technical development will not delay the TPC's schedule. Processing Schedule The TPC's schedule mentioned above includes approximately one year for HD processing at the Aberdeen site and one year for VX processing at Newport, once facilities are ready for full-scale operation with agent. However, because the TPC intends to use the same equipment at both sites, operations will not begin at Newport until agent destruction at Aberdeen is complete. Permitting Requirements The TPC has extensive experience in dealing with regulators and the public; it has obtained permits for CEP facilities in Massachusetts and Tennessee. The EPA has granted the companys technology the status of a best demonstrated available technology (BDAT). This designation means it has been judged to be equivalent in performance to incineration (the other BDAT). The EPA has also determined that CEP is not incineration. State regulators have not decided whether the technology requires a RCRA permit when used to destroy chemical agent. In other applications, the TPC has not been required to obtain a RCRA permit on the ground that the process was in those instances judged to be resource recycling rather than waste treatment. Public Acceptance The discussion above in the Permitting Requirements section is relevant to public acceptance of this technology. In addition, the TPC has mounted a public education program in the communities around Aberdeen and Newport to explain the beneficial aspects of its technology, with particular emphasis on its recycling characteristics. To date, comments at public meetings have been generally positive. However, the panel is not sure about longer-term reactions as the communities gain a fuller understanding of all the alternative technologies reviewed here. CEP is a high temperature, moderately high pressure process. The combustion of the offgas does entail stack emissions. (The current design provides for testing of the offgas prior to combustion and the release of combustion products to the atmosphere.) The EPA designation as a BDAT alternative to incineration is likely to affect some in the community positively because it

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--> shows the technology has passed a significant standard of governmental review and acceptance. However, it also means the process has demonstrated versatility for treating a wide variety of materials, including other hazardous wastes. As explained in Chapter 9, various community members have voiced opposition to processes with high temperature and pressure, processes that involve the release of combustion gases, or processes that could be used to treat a variety of hazardous wastes. From an engineering perspective, the panel views the CEP technology as well engineered to protect the public and the environment. Whether the interested communities will concur is an open question. Electrochemical Oxidation Process Performance and Engineering Technology Status The TPC has demonstrated destruction of HD and VX in laboratory tests with a 4-kW cell consisting of a single anode-cathode pair. A facility for tests at larger scale, processing approximately 250 g of agent per hour, has been built and is undergoing commissioning tests with an agent surrogate. This facility includes a 4-kW electrochemical cell, anolyte and catholyte feed circuits, an anolyte offgas condenser, an NOx reformer system, and a modified version of the combined offgas treatment circuit. Tests with VX and HD at this facility are planned. A small-scale version of the silver recovery system will be tested on the anolyte and catholyte solutions from the 4-kW facility. Stability, Reliability, and Robustness The agent destruction system operates at low temperatures and atmospheric pressure. The processes in the unit operations of the system are not sensitive to small excursions in composition or temperature. Rapid or runaway changes that might create emergency conditions are highly unlikely. Therefore, the response time required for control instrumentation is not very demanding. However, compositions of some constituents will change substantially during the course of a campaign, and a test program is needed to verify that the planned control systems are adequate to ensure stability over the full range of composition that will occur during operation. For processing HD, removal of precipitated silver chloride is essential for reliability during a 5-day campaign, and the equipment proposed to accomplish this will need to be tested at loading and conditions like those in full-scale operation. Although a runaway condition is unlikely, the system does produce large heat loads in relatively small volumes. Temperature control in each of the unit operations and in the system as a whole must be tested and validated. Safety, Health, and the Environment Safety Interlocking The electrochemical oxidation process consists of several unit operations, but they do not have to be tightly integrated. Temperature, pressure, and chemical concentrations will be monitored closely. If the monitoring data signal a malfunction, the cell current can be rapidly shutdown. Once the problem has been found and corrected, restarting the process is straightforward. Hazard Inventory The agent feed rate of about 0.01 m3/h for each 180-kW cell implies that 12.7 kg/h of HD is added to each cell, or 10 kg/h of VX. Because the agent will be rapidly hydrolyzed by the concentrated nitric acid, the panel expects that the inventory of agent in the anolyte circuit at any given time would be far less than 12.5 kg (equivalent to 5,000 ppm in a 2.5-m3 anolyte volume). The process requires handling highly corrosive or reactive materials such as nitric acid, concentrated sodium hydroxide solutions, hydrogen peroxide, and 90 percent oxygen gas. Worker-safety training and chemical containment are therefore paramount concerns, but harmful releases to the surrounding community are unlikely. Test prior to Release All liquid and solid reaction products will be tested prior to release. Gaseous products will not be tested prior to release but will be treated extensively to ensure the removal of any agent and of volatile organic contaminants formed in the electrochemical cell. Moreover,

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--> reaction conditions such as temperature, pressure, and the basic reaction mechanism ensure very low concentrations of agent and other organics in the feed to the gas cleaning system. In the panel's judgment, the offgas circuit could be modified to accommodate hold-and-test prior to release, if that step is required. Environmental Burden The major liquid process residual is an aqueous solution of common salts: sodium chloride, sodium sulfate, sodium phosphate, and sodium nitrate. The solution will contain silver at a concentration below applicable regulatory standards. (The U.S. standard is 50 ppb). Gaseous effluents are anticipated to be primarily CO2, O2, and N2. Worker Safety The worker safety concerns for this technology relate to handling agent and to possible exposure to some highly reactive chemicals. The agent handling procedures will be the same as for other technologies under review. The reactive chemicals of concern have been listed above: nitric acid, nitrogen oxide gases, hydrogen peroxide, and sodium hydroxide. The chemical of most concern is nitric acid, which is a particularly hazardous and reactive material. It is, however, a common industrial chemical, and the TPC has had experience handling it in the nuclear fuel processing industry. In addition, most of the equipment operates at near atmospheric pressure. A sound safety program will ensure a high level of worker safety. Implementation Schedule Technical Development The basic oxidation reactions of the Silver II process have been demonstrated at laboratory-scale on many materials; there is little doubt that a high level of agent destruction is possible. The entire process is complicated by the recovery of all the reaction products, as well as the silver reagent. The resultant overall process thus requires a large number of unit operations. In the case of VX, these operations appear to be straightforward and raise no critical or difficult problems of control or operation. However, additional engineering and demonstration will be required. The oxidation of HD raises a technical issue because of the high chlorine content of HD. In the working solution, the chlorine precipitates with silver as solid silver chloride. Whether the process can be operated satisfactorily with a large amount of solid precipitate accumulating in the cells during a campaign remains to be demonstrated. Some initial operability of the process with HD will be observed in an experimental program that started recently. This technology is the least developed of the technologies evaluated by the panel. Processing Schedule The facility design is based on a modular standard unit: two 180-kW cells of a commercial design form a 360-kW unit. As an example, one unit is capable of destroying 2 tons of mustard in approximately 3.5 days. The inventory of HD at Aberdeen could be destroyed by a facility of three standard units in 4 years; destroying the inventory of VX at Newport over the same 4-year period would require five units. The schedule for complete destruction of the stockpile at either site could be accelerated by increasing the number of modular units in the facility. Permitting Requirements Electrolytic oxidation processes have been used in industry but not for destroying hazardous wastes. The Silver II process would probably be viewed as novel by regulators, who would have little, if any, experience to rely on. In addition, the offgas treatment process has features that are not extensively used in waste treatment applications and would require validating demonstrations. These features include oxidation by hydrogen peroxide to clean up the final traces of NOx and organic residuals. Again, lack of regulator familiarity with the technology might delay the permitting process. Public Acceptance The communities near the Aberdeen and Newport sites have stated their preference for low temperature, low pressure, "closed loop" processes. The Silver II electrochemical process comes close to meeting all of these preferences. Most of the heteroatoms in the agents

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--> (P, S, and Cl) will be oxidized to stable acids or salts in solution, which can be analyzed before release. The carbon will be oxidized to CO2 and will be released to the atmosphere on a continuous basis after a cleanup that includes scrubbing with hydrogen peroxide to remove any trace organic compounds in the gas, followed by filtering through activated carbon. Thus, the process comes close to being "closed loop," as well as destroying agent at low temperature and low pressure. Gas-Phase Chemical Reduction Process Performance and Engineering Technology Status The GPCR (gas-phase chemical reduction) process has been demonstrated at commercial-scale for treating several organic wastes including chlorocarbons such as PCBs and hydrocarbons such as toluene. This commercial experience provides a substantial basis for assessing operational requirements and related considerations, mass balances (although the panel received little quantitative information on the actual PCB operation), gas recycling, secondary waste stream management for HCl, and operation of the catalytic reformer. The reactor is clearly capable of destroying chemical agent. However, the presence of heteroatoms other than chlorine (sulfur, phosphorus, and nitrogen) in the agents increases the complexity of the total system because additional operations are needed to remove products containing these atoms from the process gas stream. The sulfur in HD and VX will appear as H2S in the process gas and will be recovered as elemental sulfur. The scrubbing and sulfur conversion require a number of additional, albeit commercially available, unit operations. Because the fate and handling of phosphorus-containing materials are still uncertain on both a fundamental and practical level, this technology is not as mature for VX destruction as it is for HD. Two main uncertainties exist (which the TPC has acknowledged): (1) the principal phosphorus-containing products exiting the reactor have yet to be identified, and (2) a method must be demonstrated for scrubbing the phosphorus-containing products from the process gas and treating them to yield residuals suitable for disposal. Thermodynamic considerations suggest that oxyphosphorus acids and elemental phosphorus will be the predominant reaction products. The TPC reported little experience with these issues even at bench-scale. Although the TPC has developed a plan for addressing these issues, the time needed to resolve them is unclear. Another open issue is whether operation on agent will require monitoring stack gases from the combustion of fuel and process gas. Stability, Reliability, and Robustness The GPCR reactor has been used commercially and has proven to be reliable. The process operates at high temperature and near-ambient pressure. None of the reactions are strongly exothermic, and the methanere-forming reaction is strongly endothermic. However, the entire process consists of a number of sequential unit operations that must be tightly integrated and controlled. The recovery of solid process residuals (those containing phosphorus, sulfur, chlorine, nitrogen, and solid carbon) and the manufacture of hydrogen via steam reforming are carried out continuously with the gas-phase reduction in a recirculating gas loop. For simple chlorocarbons, the information provided by the TPC indicates that the overall system has been stable and reliable in operation. The reliability of the more complex system required for processing HD or VX will need to be demonstrated; tighter controls will certainly have to be implemented. In such a tightly integrated system, failure in one unit operation could significantly affect others. For example, any carryover of sulfur or phosphorus from the scrubber train to the steam reformer can poison the reforming catalyst. The current materials of construction, which have apparently worked reliably in the presence of chlorine, are to be used for agent destruction. In this different chemical environment, problems could develop that will have to be addressed by the TPC. Safety, Health, and the Environment Safety Interlocking From a safety standpoint, the most important parameter for GPCR is maintaining a slightly positive pressure throughout the recirculating gas circuit to avoid potential explosions from oxygen leaking into the circuit. The TPC has demonstrated provisions for pressure controls and interlocks. Upgrading monitoring and control room equipment to include new technology would further enhance the safety envelope.

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--> Hazard Inventory The inventory of high temperature hydrogen in GPCR presents a number of potential safety issues in the context of an agent destruction facility. The entire system must be maintained at slightly positive pressure. In addition to standard safety protocols for working with hydrogen, additional procedures for managing leaks must be developed. Hydrogen leaks that occur in the open are generally manageable and present no inordinate hazard, but leaks in a secondary containment building could cause an explosion if the gas accumulates. All of the TPC's existing facilities operate in the open without secondary containment and without area monitoring for hydrogen or feed material. For this technology to be used in an agent destruction facility with secondary containment, future designs must address the difficulty of preventing H2 buildup in the building while maintaining the integrity of this containment as backup protection against the accidental release of agent. Also, area monitoring for both H2 and agent will be required for safe operation within the secondary containment building. Strong acids and bases are used or created in the scrubbing systems. H2S, which must be scrubbed from the process gas and converted to elemental sulfur, is extremely toxic. Test prior to Release The process gas stream that goes to the steam boiler for combustion is held in tanks and tested prior to combustion, although the products of combustion are not tested prior to release through the stack. Solid and liquid residuals are to be tested prior to release. Environmental Burden Aside from the uncertainties about phosphorus, all the inorganics derived from the heteroatoms present in the agent are ultimately converted to common salts, salt solutions, or elemental sulfur. The TPC's submission did not detail the final disposition of all these materials. The process has two stacks for releasing combustion gases to the atmosphere: one for the propane burner that heats the SBV (sequencing batch vaporizer) and the other for the steam boiler, which burns a mixture of process gas and propane. Based on the design and the TPC's experience, these gas streams should be "clean." Nonetheless, if GPCR is selected for pilot-testing, the TPC and the Army will need to address the issues typically raised about trace products of combustion and the release of combustion products to the environment. Worker Safety The intrinsic safety of the technology was discussed above. In-plant monitoring must be upgraded for use with agent and hydrogen in a facility with secondary containment. Standard hydrogen safety procedures, which are well documented, must be employed. Implementation Schedule Technical Development Work in progress should identify the fate and necessary treatment of the phosphorus products. Except for provisions for increased monitoring, a secondary containment, and the engineering necessary for managing the sulfur and phosphorus wastes, the technology is developed to the point that a system like the TPC's existing commercial systems could serve as a pilot operation. Still to be resolved are the schedule implications of accommodating secondary containment and providing related reengineering. The TPC's submission assumes that the Army will provide the secondary containment building and ancillary nonprocess facilities. Processing Schedule The TPC's schedule calls for processing 5 metric tons of agent per day. This rate of operation, with about a 20 percent downtime, would require about one year to destroy the stockpile at the Aberdeen site. The panel estimates that the processing time at each site would be closer to two years. Permitting Requirements The TPC has received environmental permits for commercial operations in both Canada and Australia. However, no commercial operations have yet been sited in the United States, so the TPC has not been through

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--> the permitting process here. Several demonstrations at pilot-scale have been carried out in the United States. The TPC's personnel do have considerable experience with permitting issues in general (several come from a regulatory background), so the panel expects that the TPC can handle the necessary permitting and regulatory issues. For agent destruction, the need for secondary containment along with the potential for hydrogen leaks inside this containment could affect permitting requirements. This issue remains to be addressed in coordination with the Army. Public Acceptance The TPC states that the GPCR process has been well received and supported by the public. The process was tested by the EPA under the Superfund Innovative Technology Evaluation program. According to the TPC, several state departments of environmental quality and health have stated that the process is acceptable for treating sites contaminated by chemical wastes (e.g., the Colorado Department of Health for remediation at Rocky Mountain Arsenal). However, the technology has characteristics that some members of the communities near the Aberdeen and Newport sites have stated to be objectionable or contrary to their preferences. The process operates at high temperature and slightly positive pressure, whereas a preference for low temperature processes has been expressed in both communities. A portion of the process gas stream is burned in a conventional boiler, and the products of combustion are released to the atmosphere through a stack. The existing design includes provisions for holding the process gas for analysis and confirmation of composition before combustion. Neutralization of HD Process Performance and Engineering Technology Status he TPC has demonstrated neutralization of HD with hot water at bench-scale (114-liter reactors). The neutralization process is simple and uses conventional reactors common in the chemical industry. Additional complexity arises from treating the product of neutralization (hydrolysate) on- site. The biological oxidation of HD hydrolysate (primarily an aqueous solution of thiodiglycol) by mixed bacterial cultures in a SBR (sequencing batch bioreactor) has also been demonstrated at bench-scale. SBRs are in commercial operation for other applications. The biodegradation of HD hydrolysate can also be carried out effectively off-site at a commercial TSDF (treatment, storage, and disposal facility). Stability, Reliability, and Robustness The neutralization of HD is simple and easily controlled. Because the equipment is standard for the chemical industry, it should be reliable. The semibatch process operates at low temperature and atmospheric pressure, and the energy content of the reaction mixture is low. These characteristics preclude uncontrollable or runaway reactions. The biodegradation process should be similarly stable and reliable, except for possible upsets in microbial activity from loss of air or cooling. Safety, Health, and the Environment Safety Interlocking The unit processes, such as neutralization and biodegradation, operate independently of each other with interstage storage of the aqueous process stream. Therefore, only minimal interlocks are required. The process is monitored by analyzing for residual agent before the effluent (hydrolysate) is released from the neutralization reactor. Hazard Inventory The inherent hazard potential, apart from the hazards associated with handling agent, is limited because the aqueous streams are nonflammable and at low temperature (90°C) and pressure (1 atm gauge). The process does require that workers handle sodium hydroxide at concentrations of 18 to 50 percent. Test prior to Release The hydrolysate from the neutralization reactor is tested for the presence of residual agent before release

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--> from the toxics control area. The hydrolysate will be released only if the agent concentration is below 200 ppb. (The analytical detection limit is 10 ppb.) The consistency of this standard with Army agent-treatment standards needs to be evaluated. Process vapors are monitored for agent. They are scrubbed through a sodium hydroxide solution and passed through multiple carbon filters before release. Environmental Burden The major liquid process residual after biotreatment (either on-site or off-site) is a large volume of a dilute aqueous solution of sodium chloride, sodium sulfate, and unbiodegraded organic compounds. Toxicity testing using bioassays has indicated that the remaining toxicity is low and primarily a consequence of total salt concentration. This effluent stream should be demonstrated to be of acceptably low toxicity before discharge. The major solid residual is biomass in the form of bacterial cell material that resembles municipal sewage sludge. The largest gaseous residual will be oxygen-depleted air from the bioreactors, which will be water-saturated and will contain carbon dioxide. Worker Safety The major potential for exposure of workers to agent is in handling the ton containers before and after the agent is pumped out. This operation is common to all of the technologies. Agent destruction and waste disposal are carried out at low temperature and pressure, conditions that limit the possibility of injury. Handling sodium hydroxide solutions requires care, but the requisite practices are standard in the chemical industry. Implementation Schedule Technical Development The TPC has obtained considerable operating experience and some basic process data from bench-scale testing in reactors ranging up to 114 liters. The TPC plans to pilot-test the process in what would be a single module of a multimodule full-scale, full-rate facility. This approach reduces the risks, and should reduce the time, involved in scaling up from pilot-test to full-scale operation. The design of the pilot/production facility appears to be completed to the point at which the technology is ready for permit applications. Processing Schedule The schedule proposed by the TPC calls for about 15 months of systemization and low-rate operations. Full-rate operation of the multimodule facility is projected to continue for nine months. Permitting Requirements There appear to be no statutory barriers to obtaining permits for the HD neutralization-biodegradation technology. The favorable reaction from the Aberdeen community to this technology should allow necessary permits to be issued in about one year. The Army constraints on shipping the hydrolysate need to be modified to allow either off-site biodegradation of the hydrolysate at a TSDF or on-site biodegradation followed by discharge of the liquid effluent to a FOTW (federally owned treatment works). Public Acceptance A neutralize-and-ship process, such as configuration 4, seems likely to gain public acceptance because it meets four important criteria supported by the Aberdeen community and the Maryland CAC: (1) a full-containment (closed loop) process with controllable emissions; (2) low temperature, low pressure processing; (3) simplicity; and (4) an agent-specific technology, in the sense that the facility would require extensive modification to process a wide range of other wastes. Neutralization of VX Process Performance and Engineering Technology Status The TPC has demonstrated neutralization of VX with aqueous sodium hydroxide at a bench-scale (114-liter reactors) This neutralization process closely resembles the water hydrolysis or caustic hydrolysis of HD. More

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--> than 350 kg of VX were destroyed in the bench testing. The neutralization process is simple and uses conventional reactors common in the chemical industry. The hydrolysates from the bench tests were oxidized with sodium hypochlorite (bleach) and then were treated and disposed of, within permit requirements, by a TSDF, which used biodegradation in its processing. The efficacy of off-site biodegradation has not been validated through detailed treatability studies. However, the panel's preliminary assessment suggests that the toxicity of the hydrolysate may be sufficiently low that complete biodegradation is not necessary during disposal at a TSDF. As an alternative, existing commercial processes other than biodegradation could be used either at an off-site TSDF or on-site, if further treatment is necessary. Stability, Reliability, and Robustness The low temperature, low pressure, semibatch processing should be stable and reliable. The hydrolysis reaction is mildly exothermic (heat-releasing), but the relatively low energy content of the hydrolysis mixture precludes uncontrolled or runaway reactions. The simple unit processes and standard equipment closely resemble well-tested counterparts in the chemical industry. Safety, Health, and the Environment Safety Interlocking The unit processes, such as ton container processing and VX neutralization, operate independently with interstage storage of the aqueous process stream. Therefore, only minimal interlocks are required. The hydrolysate from neutralization is analyzed for residual agent before it is released from the toxics control area. Hazard Inventory The inherent hazard potential, except for the hazards associated with handling agent, is limited because the aqueous streams are nonflammable and at low temperature and pressure. The hydrolysate retains some nonagent toxicity. The process requires handling corrosive caustic and bleach solutions, but the procedures for doing this are standard in the chemical industry. Test prior to Release The hydrolysate from the VX neutralization reactor is tested for the presence of residual agent and for a toxic by-product (EA-2192) before release from the toxics control area. Process vapors, which are monitored for agent, are scrubbed through a sodium hydroxide solution and passed through carbon filters before release. Emptied storage containers are steam cleaned and tested for the presence of agent vapor before being shipped to the Rock Island Arsenal in Illinois for melting. Environmental Burden The major liquid process residual for off-site treatment and disposal is the hydrolysate, which appears to have low toxicity. As a consequence of dilution during the process, the volume of the hydrolysate is much greater than the volume of agent treated. The major solid residual is biomass. The nitrogen contained in the agent is incorporated into the biomass. Worker Safety The major potential for exposure of workers to agent is in handling the ton containers before and after agent is pumped out. This operation is common to all of the technologies. The hazards of neutralization are limited by the low temperature and pressure of the process. Handling sodium hydroxide and sodium hypochlorite solutions requires care, but the requisite practices are standard in the chemical industry. Implementation Schedule Technical Development The TPC has considerable operating experience and some basic process data from bench-scale testing with agent in reactors ranging up to 114 liters. The TPC plans to pilot-test the process in what would be a single module of a multimodule facility. This approach reduces the potential for schedule delays—and should reduce the time—in scaling up from pilot-test to full-scale operation. The design of the of the pilot/full-scale facility is advancing rapidly, and the technology appears ready for permit applications.

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--> The panel estimates that a maximum of six months should suffice to resolve the issues related to toxicity of the hydrolysate and to perform detailed treatability studies of hydrolysate biodegradation, if further treatment is required to reduce toxicity. If these issues cannot be resolved quickly, another proven process for treating the hydrolysate prior to disposal can be selected. Processing Schedule The schedule proposed by the TPC calls for about 15 months of systemization and low-rate operations. Full-rate operation of the multimodule facility is projected to continue for nine months. Permitting Requirements Implementing the TPC's plan to pilot-test VX neutralization in one module of what would become the multimodule full-scale, full-rate facility at Newport will require modification of the Indiana statute that mandates prior success of the technology at a comparable facility elsewhere. There appear to be no other statutory barriers to acquiring permits for the neutralization pilot plant. It should be feasible to modify a TSDF permit to allow shipping and treating the hydrolysate. Based on discussions with regulators, the panel estimates that acquiring the permits for the neutralization facility may require one year. Public Acceptance The neutralization process seems likely to gain public acceptance because it meets four important criteria supported by the Newport community: (1) a full-containment (closed loop) process with controllable emissions; (2) low temperature, low pressure processing; (3) simplicity; and (4) an agent-specific technology, in the sense that the facility would require extensive modification to process a wide range of other wastes.