Waste Management: How Waste is Treated

The Department of Energy (DOE) has a program which directs the proper storage, treatment and the disposal of the department's generated waste called the Waste Management Program. As there has been growing concern for the environment, it is necessary for wastes to be treated, especially those wastes which contain hazardous chemicals and radioactive components. Waste treatment techniques have been used by the DOE (1) to modify or change completely the physical, chemical or biological characteristics of the waste and (2) to lessen the wastes' volume as well as its toxicity; thus, making the waste safer for disposal.

The selection of treatment techniques of waste materials are based on the materials' composition, quantity and form. Other materials that are safe to dispose are not treated by the DOE. At present, the methods being used by the DOE in treating waste are solidification and volume reduction.

Solidification. This technique is used to treat non-solid radioactive waste. One example of this technique is the calcining process. The process uses the fluidized bed system, wherein the radioactive liquid waste droplets are being sprayed into the calcining vessel where the waste turn into solids quickly on the hot fluidized beds. Waste materials, in the end, become water vapor and small radioactive waste grains. These materials are then transported through pipes to stainless steel for long term storage until disposal. Another example of the solidification technique is the vetrification, a process which combines semi-liquid waste with glass. Here, extremely radioactive liquid waste and sludge are mixed with glass particles and heated at a very high temperature to generate a molten glass which will then be poured into stainless steel canisters. This process will trap radioactive elements which prevent it to freely move into the environment.

Solid Waste Reduction. This technique will reduce the solid volume of the waste through incineration, compaction and sizing. Incineration has been made the standard process used by the department to treating mixed wastes. This process may be used in treating and destroying combustible materials in transuranic, low-level and some mixed waste. However, this process poses some challenges. First, incineration does not destroy the radioactivity of the waste material. Second, incineration does not destroy heavy metals - a very significant problem in many hazardous waste streams. Third, the process results into toxic compounds which have been formed due to incomplete combustion such as dioxins and furans - highly hazardous compounds. Finally, incineration also generates a significant amount of gases and particulates that must be controlled through an air pollution control system.

Another technique in solid waste reduction is compaction which is a means of reducing the volume of noncombustible waste through the compression into a smaller and denser waste form. The last technique in solid waste reduction is the sizing process which uses the supercompaction technology. The supercompaction technology paves way in compessing barrels which contain radioactive solid waste to one fifth of their original size. The process uses a plasma arc torch to cut the large pieces of contaminated metals into smaller pieces, thus needing less packaging space. As the metal pieces have been reduced in size, they will be stacked in containers and then buried as low-level waste.