Hazardous waste are waste which has a potential negative effect on the health of the public or the environment.
We call them hazardous waste because if these wastes are not properly managed, it could contaminate the environment and also cause ill-health to the public. These waste can be generated both domestically and industrially.
Hazardous waste could exist in different physical forms: It could be in solid form, Liquid or Gaseous. They cannot be disposed of using normal disposal methods, but depending on their physical state, proper disposal procedures are always adopted for their disposal.
A waste is described as being hazardous if it posses either of the following characteristics:
- Toxicity: This explains the degree in which the waste can damage or be poisonous to human. Example of toxic waste includes waste containing mercury, lead, DDT, PCBs, etc
- Corrosive: Here the waste has the capacity to erode or eat away any surface it gets in contact with. Example includes solids that are acids or bases, or that produce acidic or alkaline solutions.
- Reactive: This explains the ability for the waste to act when released. These waste are unstable under normal condition. Example includes toxic fumes, gases, or vapors when heated, compressed, or mixed with water
- Ignitable: The ability of the waste to start a fire under certain conditions. Examples are, waste oil and unused solvent.
hazardous waste could be the by-products of manufacturing processes, discarded used materials, or discarded unused commercial products, such as cleaning fluids (solvents) or pesticides.
In regulatory terms, a hazardous waste is a waste that appears on one of the four RCRA hazardous wastes lists (the F-list, K-list, P-list, or U-list)
Management of hazardous waste
Hazardous waste management is a very important aspect which should be taken seriously from the point of waste generation, storage, transportation, treatment, and disposal.
Some times, waste generation can be managed at the source thereby reducing the total amount of waste generated. Storage and transportation should be done using government approved standards; spilling of waste while on transit should be curtailed.
Hazardous waste treatment:
Hazardous waste can be treated by chemical, thermal, biological, and physical methods.
- Physical treatment concentrates, solidifies, or reduces the volume of the waste. Physical processes include evaporation, sedimentation, flotation, and filtration.
- Chemical methods include ion exchange, precipitation, oxidation and reduction, and neutralization.
- Thermal treatment will involve the use of high-temperature incineration, which not only can detoxify certain organic wastes but also can destroy them.
- Biological treatment could adopt the use of a technique called Landfarming. In this technique the waste is carefully mixed with surface soil on a suitable tract of land. Microbes that can metabolize the waste may be added, along with nutrients or a genetically engineered species of bacteria is used.
After waste treatment, what comes next is disposal. The common form of disposal is either landfilling or ground injection.