A simple definition of hazardous waste is waste that can cause harm to human and the environment. Wastes are classified as hazardous if they exhibit any of four primary characteristics based on physical or chemical properties of toxicity, reactivity, ignitability and corrosively.

  1. Toxic wastes are those that are poisonous in small or trace amounts. Some may have acute or immediate effect on human or animals. Carcinogenic or mutagenic substances, such as pesticides and heavy metals, cause biological changes in the children of exposed people and animals.
  2. Reactive wastes are those that have a tendency to react vigorously with air / water and / or are unstable to shock or heat, generating toxic gases or exploding during routine management, such as gun powder and nitro glycerine.
  3. Ignitable waste burns at relatively low temperatures (<60°C) and is capable of spontaneous combustion during storage, transport or disposal, e.g. gasoline, paint thinners and alcohol.
  4. Corrosive waste destroys materials and living tissues through chemical reactions, such as acids.

The main sources of  hazardous waste are chemical manufacturing companies, petroleum refineries, paper mills, smelters and other industries. Tens of thousands of different chemicals are used in industries every day. When used incorrectly or inappropriately, they can become health hazards. PCBs (Polychlorinated biphenyls) are one example of commonly used, but potentially hazardous chemicals. They are resistant to fire and do not conduct electricity very well, which makes them excellent materials for several industrial purposes. PCBs retain their toxic characteristics for dozens of years. They cause long-term exposure problems to both human and wildlife. Rainwater can wash PCBs out of disposal areas in dumpsites and landfills thus contaminating the water table. Annually, several million tons of hazardous waste is generated worldwide.

Hazardous waste can be treated by chemical, biological, thermal and physical methods. Chemical methods include ion exchange, precipitation, oxidation and reduction, and neutralization. One biological treatment method of certain organic wastes, such as those from the petroleum industry, is called landfarming. The waste is carefully mixed with surface soil and microbes that can metabolize the waste are added, along with nutrients. In some cases, a genetically engineered species of bacteria is used. Microbes can also be used for stabilizing hazardous wastes on previously contaminated sites; in that case the process is called bioremediation.

Among thermal methods is high-temperature incineration, which not only can detoxify certain organic wastes but also can destroy them. Special types of thermal equipment, such as the wasteWOIMA® waste-to-energy power plant, are used for burning waste in either solid, liquid, or sludge form. One problem posed by hazardous-waste incineration is the potential for air pollution, which must be managed in accordance with relevant regulations using best available technologies (BAT).

The chemical, biological and thermal treatment methods outlined above change the molecular form of the waste material. Physical treatment, on the other hand, concentrates, solidifies, or reduces the volume of the waste. Physical processes include evaporation, sedimentation, flotation, and filtration. Yet another process is solidification, which is achieved by encapsulating the waste in concrete, asphalt, or plastic. Encapsulation produces a solid mass of material that is resistant to leaching. Waste can also be mixed with lime, fly ash, and water to form a solid, cement-like product. These methods require energy and the mixing medium, both of which are available at the wasteWOIMA® plant. Thus, the hazardous waste can generate the very means required to render it inert, a true win-win situation.


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WOIMA Corporation is a Finnish supplier of best-in-class waste-to-value products, projects and services worldwide. We have developed solutions that enable us, and the customer, to transform and recycle virtually any waste stream into raw materials and energy.  At WOIMA we combine Finnish engineering know-how in waste management with power generation design expertise. These solutions are used in Finland every day. They support the circular economy ideology and ensure that less than 1% of Finland’s waste ends up in landfills.

Our mission is to improve quality of life both locally and globally, as well as empower people to utilize waste as a commodity. Our decades of international project management experience ensure an on-time, in-budget and high-quality WOIMA solution delivery across the globe.


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