Physical decontamination methods

METHODS OF DECONTAMINATION Physical Removal Chemical Methods Certification of Decontamination... 

BIOLOGICAL AGENT DECONTAMINATION Chemical Method Physical Method... 

Alternative physical methods for decontamination including electrostatic precipitation, ultraviolet irradiation, heat, etc., are reviewed below. 

Physical methods are not suitable for a rapid decontamination because they are time consuming and the process does not normally end with a detoxified agent. The apphcation of physical methods can only prevent a further spreading of the contaminants and their penetration into nonsealed or chemically hardened surfaces. 

Free acid present in equipment requires neutralization as well as washing and a five percent solution of sodium carbonate (soda ash) is used for this purpose. Because of the uncertainty of complete removal of explosives in all cases by the physical methods described, chemical methods are used also to supplement these. Standard decontamination procedures include the decontaminating chemical shown by table 15-4. 

As concentrations of contaminants increase, the potential for permeation of PPE increase. The chemical and physical compatibility of decontamination solutions and methods with selected PPE should be determined before use [2]. 

The chemical and physical compatibility of decontamination solutions or other decontamination materials must be determined before use. Any decontamination method that permeates, degrades, damages, or otherwise impairs the functioning of the personal protective equipment (PPE) is incompatible with such PPE and should not be used. If a decontamination method does pose a direct health hazard, measures must be taken to protect both decontamination personnel and the workers being decontaminated. Figure 16.22 presents a decision aid for the evaluation of health and safety aspects of decontamination methods. 

Dougherty et al. (1993) conducted a theoretical analysis of a proposed in situ method for decontaminating soil by photodegradation. Up to 86% of TCDD in the soil can be degraded by this process (Zhong et al. 1993). Because of its extremely low water solubility and volatility, TCDD is a very persistent soil contaminant. With the method, based on the physical properties that facilitate photolysis... 

For radioactive effluent treatment, the relevant membrane processes are microfiltration, ulfrafiltration (UF), reverse osmosis, electrodialysis, diffusion, and Donnan dialysis and liquid membrane processes and they can be used either alone or in conjunction with any of the conventional processes. The actual process selected would depend on the physical, physicochemical, and radiochemical nature of the effluents. The basic factors which help in the design of an appropriate system are permeate quality, decontamination, and VRFs, disposal methods available for secondary wastes generated, and the permeate. 

It has been suggested, perhaps thoughtlessly, that dispersion of slippery viscous agents in the direction of rioters would impair their co-ordinated movements and make it difficult for them to undertake malicious tasks. However, not only would there be the likelihood for uncontrolled physical accidents, but also problems in the control of motorized vehicles in the area, including those of the security forces. Additionally, in public areas, there would be a need for prompt street decontaminations by environmentally acceptable methods. 

Three basic methods of decontamination are physical removal, chemical deactivation, and biological deactivation of the agent. Biological deactivation has not been developed to the point of being practical. 

When animal skin contaminated with the nerve agent GB was flushed with water at 2 minutes (a method in which physical removal predominates over hydrolysis of the agent), 10.6 times more GB was required to produce the same mortality rate as when no decontamination occurred.7 In another study, the use of water alone produced better results than high concentrations of hypochlorite (ie, 5% or greater, which is not recommended for skin).8 Timely copious flushing with water physically removes the chemical agent and will produce good results. 

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