Health and safety at hazardous waste sites depend on decontamination, the procedure of removing or neutralizing contaminants that have accumulated on employees and equipment. Decontamination shields workers from dangerous substances that might contaminate and eventually absorb the protective clothing, respiratory equipment, tools, vehicles, and other equipment used on the job site; it safeguards all site personnel by limiting the transfer of dangerous substances into clean areas; it aids in preventing the mixing of incompatible chemicals, and it safeguards the neighborhood by preventing uncontrolled transportation of contaminants from the site.
Before any individuals or equipment can access places where there is a risk of exposure to hazardous materials removal, a decontamination plan should be created and put up. The decontamination strategy ought to:
- Establish the quantity and configuration of the decontamination stations.
- Find the necessary disinfection equipment.
- Choose the best decontamination techniques.
- Create measures to protect clean areas from contamination.
- Establish techniques and guidelines to reduce worker exposure to pollutants during the removal of personal protective gear and clothes (PPE).
- Set up procedures for getting rid of garments and equipment that haven't been fully decontaminated.
The plan should be updated whenever the type of personal protective equipment or clothing changes, the site conditions change, or the site dangers are re-evaluated in light of new knowledge.
Establishing Standard Operating Procedures that reduce contact with waste and the possibility of contamination is the first stage of decontamination. For instance:
- Emphasize safety procedures at work that reduce interaction with dangerous substances.
- Utilize methods for handling, opening containers, and remote sampling.
- Instruments for sampling and monitoring are bagged for protection. Create ports and holes in the bags for sensors that need to make contact with the materials on the site.
- Wear disposable outerwear, and when necessary, use disposable tools.
- Apply a strippable coating on instruments and equipment so that they can be stripped off during decontamination.
- Cover the contaminating source, such as with plastic sheeting or overpacks.
To get rid of any dangerous chemicals or infectious organisms that may have stuck to them, all employees, clothing, equipment, and samples leaving the contaminated area of a site must be decontaminated. Decontamination techniques either 1) physically remove contaminants, 2) inactivate contaminants using chemical detoxification, disinfection, or sterilization, or 3) remove contaminants using a mix of both physical and chemical techniques.
Physical Removal
Gross contamination can frequently be eliminated physically through the use of dislodging/displacement, rinsing, wiping off, and evaporation. High pressure, high heat, and/or high-pressure physical methods should be used sparingly and only when essential because they can spread contamination and result in burns.
Following are some categories of contaminants that can be eliminated physically:
- Loose contaminants. Water or a liquid rinse can be used to get rid of dust and fumes that stick to tools and people or be sucked into spaces like the weave of clothing fabrics. The removal of materials that are electrostatically attracted can be improved by applying anti-static coatings to clothing or equipment. These are offered commercially as anti-static sprays or wash additives.
- Adhering contaminants. Other than electrostatic attraction, some contaminants cling to surfaces. The type of contaminants and the temperature have a big impact on the adhesive properties. For instance, contaminants like glues, cement, resins, and muds have far stronger adhesive qualities than elemental mercury and are therefore challenging to physically remove. Scraping, brushing, and wiping are examples of physical removal techniques for gross contaminants. It is possible to improve the removal of sticky contaminants by solidifying, freezing (e.g., with dry ice or ice water), adsorbing or absorbing (e.g., with powdered lime or kitty litter), or melting.
- Volatile liquids. Evaporation followed by a water rinse can be used to get volatile liquid contaminants off of protective garments or equipment. By utilizing steam jets, volatile liquid evaporation can be accelerated. Care must be taken to avoid worker inhalation of the vaporized compounds during any evaporation or vaporization operation.
Chemical removal
Gross contamination should be physically removed, then cleaned using a wash/rinse procedure. These cleaning solutions often employ one or more of the techniques listed below:
- Dissolving contaminants. Surface contaminants can be chemically removed by dissolving them in a solvent. Chemical compatibility between the cleaning solution and the equipment is required. When decontaminating personal protective gear made of organic materials that could be harmed or dissolved by organic solvents, this is especially crucial. Additionally, any organic solvents, such as alcohols, ethers, ketones, aromatics, straight-chain alkanes, and common petroleum products, that may be flammable or potentially poisonous must be chosen, used, and disposed of carefully.
- Surfactants. By lowering the forces of adhesion between contaminants and the surface being cleaned and by preventing the redeposition of the contaminants, surfactants improve physical cleaning techniques. Detergents used in the home are among the most popular surfactants. To enhance the dissolving and dispersion of pollutants into organic solvents, certain detergents can be utilized.
- Solidification. Solidifying liquid or gel contaminants can enhance their physical removal. The mechanisms of solidification are (1) moisture removal through the use of absorbents such as grounded clay or powdered lime: (2) chemical reactions via polymerization catalysts and chemical reagents; and (3) freezing using ice water.
- Rinsing. Through solubilization, dilution, and physical attraction, rinsing eliminates contaminants. More contaminants are removed by multiple rinses with clean solutions than by a single rinse with the same volume of solution. In comparison to repeated rinsings with smaller total volumes, continuous washing with big volumes will remove even more contaminants.
- Disinfection/Sterilization. Chemical disinfectants are an efficient way to render infectious pathogens inactive. Unfortunately, heavy equipment and personal protection equipment cannot usually be sterilized using ordinary methods. For use with infectious pathogens, it is advised to utilize disposable PPE.