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LOW-TEMPERATURE, LIQUID-PHASE PROCESSES 110 research will be required. The discussions of the three types of processes below reflect their developmental differences. An advantage of these technological alternatives is that they generally permit highly controlled, dosed environments. Most of these approaches will involve minimal gas emissions, and are suitable for in situ analysis of the progress of the course of agent destruction. A variety of toxicological tests has indicated that the chemical hydrolysis products have very low toxicity, making it possible to effectively manage the waste streams resulting from most of these processes. There has been extensive study of the alkaline hydrolysis of nerve agent GB, and the chemical products have been identified. Although the chemical and biological systems have a certain, inherent technological simplicity due to their mild environmental requirements, there are several important considerations common to all of them: ⢠There are various chemical specificities in the nature of the chemical or biological reactions that may limit their applicability to some of the contaminating ingredients of many stockpile elements. ⢠The gelatinous or insoluble nature of some of the stockpile material configurations may hamper their conversion. ⢠Each approach will result in a variety of process-specific reaction products with various levels of hazard that must be handled as separate waste streams in many cases. ⢠It may be necessary to sequence several processes, in some cases integrating chemical and biological technologies to adequately manage all of their reaction products. ⢠These low-temperature processes are generally not applicable to dunnage or the 5X decontamination of metal parts. Therefore, other processes would still be needed to handle these streams in the overall demilitarization system. The implication is that alternative demilitarization chemical processes must be carefully tailored to meet the requirements for each agent. A readily available low-temperature, liquid-phase technology is unlikely to be appropriate for all of them. CHEMICAL DETOXIFICATION PROCESSES A number of chemical processes that are known conceptually, experimentally, or in practice to destroy agent will (or can) run at moderate temperatures (between room temperature and 100°C) and at atmospheric pressure. Most of these processes are relatively simple to carry out and can be used in reactors commonly used in the chemical industry. Although no
LOW-TEMPERATURE, LIQUID-PHASE PROCESSES 111 single chemical treatment appears to destroy all three agents (GB, VX, and H), reactions to destroy all three could probably use the same basic equipment. However, parallel sets of some components may be desirable for each process because of differences in reaction rates, mixing conditions, and heating and cooling requirements. A distinct advantage of these chemical processes is that they can be operated in batch mode, with complete containment during the process and opportunity to verify satisfactory agent destruction. The destruction level should satisfy treaty requirements and hazardous material requirements for subsequent on-site storage and transportation to another site. Alternatively, further on-site treatment could be used to complete oxidation. A small gas evolution is expected for acid chlorinolysis and other processes that use oxidizing agents. A further advantage of these low-temperature, atmospheric-pressure, liquid-phase processes is that leaks of lethal agents are less likely to occur than from pressurized equipment. Although all these method are generally effective for destroying the chemical agents of chief interest, they generate different waste streams. Some might yield chemicals now used in the civilian economy, but economically viable recovery is not expected. By using some of the processes, relatively simple operations at each Army storage site could convert lethal chemical agents into material that meets demilitarization requirements. Such material could be managed according to standard practices for chemical waste. This approach would permit local storage or transport of the demilitarized material, of hazard no greater than that for industrial chemicals regularly shipped, to a central location where it could be processed by conventional waste treatment technology. In the United States, research on the chemical detoxification of bulk agent for demilitarization was mostly discontinued in 1982, when the decision was made to use incineration. Fortunately, a research and testing program on decontamination techniques for battlefield use has continued and produced many advances in understanding and applying chemistry relevant to detoxification. An informative review was recently published (Yang et al., 1992). Battlefield decontamination systems face a number of constraints not directly relevant to demilitarization of bulk agents. They are restricted to ambient temperatures and the need to minimize damage to surfaces. In addition, speed and ease of operations are essential. For bulk agent demilitarization, minimizing disposal problems is more important than for battlefield decontamination. Also, some chemical reactions that have not been found useful for battlefield decontamination might, under conditions of intense mixing and higher temperature, be useful for bulk agent detoxification.
