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Disposal of Neutralent Wastes 3 Criteria for Evaluating Technologies A great many nonincineration technologies could theoretically be used to treat the neutralents from the MMD and the RRS. The committee selected the most promising technologies (see Table 3-1 ) from the following sources: recent NATO reviews, which include many general descriptions previous studies by the National Research Council of the destruction of chemical agents current programs by the Army and Army contractors for the destruction of agents or neutralent commercial experience with the destruction of other waste streams TEMPERATURE CLASSIFICATIONS The technologies were classified into four categories according to operating temperature: low temperature, moderate temperature, high temperature, and very high temperature. The technologies classified as low temperature operate at temperatures of less then 100°C (boiling point of water). These technologies do not require pressurized containment. Technologies classified as moderate temperature operate at temperatures of 100°C to 370°C. Technologies classified as high temperature operate at temperatures of 370°C to 1,000°C. Technologies classified as very high temperature operate at temperatures of more than 1,000°C. PRESSURE CLASSIFICATIONS The technologies were classified into four categories according to operating pressure: low pressure, moderate pressure, high pressure, and very high pressure. The technologies classified as low pressure operate at pressures of less than 15 pounds per square inch absolute (psia). 1 These technologies do not require pressurized containment for an aqueous system when processing waste. A wide range of reasonably standard support equipment (e.g., pumps, flanges, valves, etc.) rated for up to 615 psia are available. Technologies operating at pressures from 15 to 615 psia were classified as moderate pressure. Above 615 psia but still in Division I (less than 3,015 psia), considerably more care is necessary in the design of the process vessels to prevent leakage. Technologies operating at pressures of 615 to 3,015 psia were classified as high pressure. Above 3,015 psia (Divisions II and III), designing process vessels required specific individual designs and calculations, as well as special requirements for support and containment structures. Technologies operating at pressures of more than 3,015 psia were classified as very high pressure. SELECTION CRITERIA The committee did not have the time or resources to evaluate all of the technologies. Therefore, only the most promising technologies were selected for more detailed evaluation. These technologies were selected according to the following criteria: If a great deal of information was available, and the technology was under serious consideration and/or evaluation for other demilitarization or waste treatment purposes (e.g., technologies being tested under the ACWA Program), it was selected for evaluation. 1 Fifteen (15) psia is the established transition point between low-pressure tank and pressure vessel design standards covered under the API Std. 620 and ASME Boiler & Pressure Vessel Code, Section VIII (Div. I for under 3015 psia, Div. II & III for over 3015 psia).
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Disposal of Neutralent Wastes TABLE 3-1 Technologies Selected for Evaluation Technologies Oxidation or Reduction Temperature Pressure Chemical oxidation oxidation low low Biodegradation oxidation low low Electrochemical oxidation (Ag(II) and Ce(IV)) oxidation low low Solvated-electron technology (SET) reduction low moderate Wet-air/O2 oxidation (WAO) oxidation moderate moderate to very high Supercritical water oxidation (SCWO) oxidation high very high Gas-phase chemical reduction (GPCR) reduction high low to moderate Plasma-arc technology oxidation very high low to moderate If, in the committee's collective judgment, a technology was likely to be safe, effective, and permitted, and also likely to rate satisfactorily on the pollution prevention criteria (see below), it was selected for evaluation, and efforts were made to gather more information. The eight technologies selected cover a broad range and are not limited to the technologies advocated by technology providers. TOP PRIORITY CRITERIA Relatively Safe Processes (Low Risk) Technologies were reviewed to determine if a common process failure (e.g., explosion, corrosion, mechanical failure, operator error, incorrect feeds, service failure, etc.) under normal operating conditions could lead to serious worker, community, or environmental damage. The following factors were considered: minimal storage and transportation of hazardous materials minimal toxicity and flammability of all materials temperatures and pressures below the threshold values that challenge reliable containment Technical Effectiveness Technologies were evaluated for their consistency in achieving a standard (in this case, destruction) of neutralent. The following factors were considered: efficiency of detoxification of the neutralent (i.e., solid wastes could be disposed of in a landfill and liquid wastes released to a POTW) integration into a system for the destruction of nonstockpile materiel Permit Status Technologies were evaluated for serious regulatory obstacles that would prevent environmental and/or operational permitting. The following factors were considered: potential major delays in obtaining permits under federal (and international), state, or local regulations potential for meeting schedules of international treaties Pollution Prevention The committee evaluated the technologies on the principle of “green chemistry” (Mulholland and Dyer, 1999). In other words, pollution prevention and waste minimization practices are implemented at the beginning of the process (pollution prevention) as opposed to after the fact (pollution abatement). The following factors were considered: minimal addition of processing materials 2 that would require treatment, disposal, regeneration, recycling, or other handling minimal number of processing steps, which all have an incremental environmental burden in potential leaks and energy, maintenance, shutdown and start-up, and clean-out requirements 2 Processing materials include not only the obvious purchased solvents, acids, bases, etc., and service materials, such as catalysts, filters, and adsorbents, but also common items, such as water, nitrogen for instruments and vapor-space inerting, and nitrogen in air used as a source of oxygen. These materials might be used for the process itself or for support tasks, such as cleaning.
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Disposal of Neutralent Wastes minimal toxicity of emissions, wastes, or other material that require treatment, disposal, regeneration, recycling, or other handling 3 operating temperatures and pressures as close to ambient as possible minimal corrosion, plugging, sensitive process-control parameters, and other operating difficulties minimal high-temperature vapor streams that require high-quality treatment IMPORTANT CRITERIA Once the selected technologies had been evaluated according to top priority criteria, they were evaluated by the important criteria. Robustness A robust technology can function successfully in stable continuous operation. The term “continuous” means the technology can treat neutralent from beginning to end and does not require another technology as an intermediate step before final disposal. Continuous also means that feedstock can be continuously supplied or supplied in the batch mode. Operation of a robust technology has the following characteristics: tolerance of normal variations (differences in concentrations of hazardous materials or chemical agents) start-up and shutdown of a facility without major complications or delays operation at small scale or large scale, as required capability of treating a wide range of potential feeds (neutralents from the RRS and MMD) Cost Although the committee did not conduct a cost analysis for each technology, cost was estimated based on past experience and knowledge. The following cost factors were considered: total costs, including capital and operating costs costs per unit of feed Practical Operability The following factors related to practicality were considered: minimal training for operators (average skill levels for the chemical industry) use of standard instrumentation for monitoring and process controls Continuity Two factors were considered in this category: likelihood of finding a vendor likelihood that supplies of raw materials will be available Space Efficiency The main factor in space efficiency was the weight, area, and volume of operating equipment per volume of material processed. Materials Efficiency The following factors were considered: recycling of materials as part of the internal operation of the facility shipment of wastes off site for beneficial reuse use of recycled materials from external sources Areas of Special Concern Because of the lack of empirical information on neutralent treatment, the committee's approach to establishing evaluation criteria for the eight selected technologies was necessarily qualitative. Some particular areas of concern are included in those criteria that were not identified separately. These areas of concern are discussed in the write ups of specific technologies in Chapter 4 and are identified below: acetic acid (a compound resulting from oxidation processes that is difficult to oxidize further and will probably be present in neutralents; although easily biodegradable, its presence is a good indicator of the need for discharge to a POTW) arsenic (including oxides and metallo-organic compounds) nitrogen oxides (including NOx, N2O) sulfur compounds (SOx, H2S) dioxins and furans cleanup, decontamination, and relocation of facility 3 For example, arsenic, which is present in lewisite neutralent, is a semivolatile metal in a high-temperature process. The arsenic is released as a vapor and condenses in the gases as a very fine, hard-to-capture particulate. The 1999 EPA incinerator regulations added stringent emission limits for semivolatile metals, and incinerator operators are, therefore, very cautious about accepting wastes containing organo-arsenic compounds.
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