Beads, vapor characteristics make step-wise cleanup vital
Since the early 1990s, U.S. environmental regulations have eliminated the development of mercury as a new product. Despite these changes targeting mercury use, alternatives have been slow to develop, and in cases such as precision measurement devices are not possible. As a result, mercury has been mined through reclamation and recycling processes.
Consumers can still find mercury in high-pressure sodium lamps, fluorescent bulbs, some thermostats, spent batteries, sphygmomanometers, thermometers, dental amalgams, chemicals and staining solutions. It is used in more than 3,000 industrial applications.
People know the dangers of this neurotoxin but they still seem to use it. Careful handling should minimize general exposure, but what should a person do when a spill occurs? The following refresher "course" should provide some valuable insight.
No mercury spill cleanup can be undertaken without the right tools. A spill kit should be on hand at any workstation where the risk of mercury spillage and exposure exists. The kit should contain goggles, nitrile gloves, disposal bags, waste labels, storage container, mercury-type respirator, mercury-sensing badges or instruments, absorbent scratch pads, water spray bottle, shoe covers, warning tape and, preferably, zinc-ferrous based magnetic mercury amalgamation powder. Additional tools such as plastic, non-sparking shovels and sweeping devices and a telescoping magnetic tool to collect hardened amalgam are recommended.
Commercially available spill kits range in price from $50 to $200 depending on the size.
With tools at the ready, what is the next step?
1. Limit exposure. A company or site should follow a set procedure to reduce the risk of exposure to individuals and contain the mercury spillage area.
Cleanup team members should don personal protective equipment (removing all metallic objects) and isolate the contaminated area, evacuating all personnel until the cleanup is complete. The spill area should be marked off with tape or signs. The team should interview the person involved in the spill and together they should fill out an inquiry report. This process helps determine whether the spill is simple (less than 1 pound of mercury) or complex.
Most mercury spills are in liquid form, making collection of the small beads particularly difficult.
But a broken light fixture is just as much a risk to employees because the dust readily spreads and can be inhaled.
2. Ventilate the area. Since free mercury will readily vaporize, air conditioning or heating systems should be shut down and windows opened to get the maximum amount of air in the room and allow the vapors to flow outside.
3. With the area contained, the cleanup team can begin determining the areas of contamination and residue on a hard, soft, or soil surface. Mercury-sensing gauges, a gas vapor analyzer, or even a high-intensity halogen light can detect the presence of mercury droplets or powder. The team also may choose to apply sodium sulfide solution to the area; a dark reddish brown color appears in the presence of mercury.
There are two methods used to clean up mercury: amalgamation or insolubilization. Both methods will turn mercury into a non-vaporizing form. Insolubilization requires that mercury be made into a solid, stable mercury compound, mercuric sulfide. Amalgamation mixes the mercury with one or more metals into a solid.
4. Once the mercury has been located, the team should apply the magnetic amalgamation powder directly to the contaminated area. Using the spray bottle, they should apply a slight mist of water onto the powder, allowing the dry acid reagent to react with the metals and start to form the solid bond. Scratch pads should be used to mix the powder and mercury together until the metals look like a paste. With normal setting times -- approximately one hour -- the team should survey the entire area for additional contamination spots, noting cracks, crevices and any orifices.
The additional spots should be remediated as before. Once the material hardens, the team can use the magnetic pickup tool to collect the mercury-bearing waste and place it in the storage container. This application also works well when mercury has accidentally been poured down a drain. The magnetic tool can be used like a drain snake to collect and remove the waste amalgam.
For insolubilization, the spill response team would use a sulfide mixture powder on the mercury contaminated area. A distinguishing brown color appears in the presence of mercury. Once the material hardens, it can be collected for disposal, similarly to the amalgam method.
5. The team should place all contaminated materials into the bucket with sealed lid. This container will be the primary device to return the objects to the mercury recycler. They should inspect the area and atmosphere for any residual indication of mercury vapors. A wax-like sealant can be applied over the surface area to cover any residual mercury, if applicable. Occupational Safety and Health Administration standards limit the exposure risks to vapor to be no more than 0.2 mg/L. Great care must be taken to inspect all the areas before declaring the site safe for employees. The team also should collect the tools, gloves, boots, etc., and put these into separate containers for disposal.
Another common spill situation occurs when mercury has been spilled in a doctor’s office and winds up on carpeting. The same skill and observation to detail must be followed to complete the cleanup task. Application of the amalgamation powder and collection with a mercury-only vacuum is the preferred method. The affected carpet area is then cut out and ripped up, with all items, including the vacuum cartridge, put into disposal containers for return to the recycler. Vapor analysis will indicate if additional treatment is needed.
Occasionally, mercury is spilled outside and into the surrounding soil. Great care must be taken to set up a perimeter around the contaminated area and to collect the soil for cleaning. Soils vary in type and consistency, and commonly, the mercury is found very close to the surface. The soil can be taken off site for reclamation via distillation or by using a combination of forming layers of the amalgamation powder and sand, making a slurry of the soil and water and passing the mixture through the filter media. The effluent should be tested for mercury contamination and the filter media retained for processing at the recycler.
Recyclers have additional precautions they must take in handling mercury-bearing waste. The U.S. Environmental Protection Agency's Greenlights program, for example, has set standards for fluorescent bulb disposal and mercury reclamation.
For more information about standards, recycling facilities, and how to set up a collection program contact the Mercury Awareness Program or the Association of Lighting and Mercury Recyclers.