Q.Describe the management of hazardous wastes.

Managing hazardous waste requires a structured hierarchy of practices -- from reducing waste generation, through treatment, to safe final disposal -- supported by legal regulation, to prevent harm to human health and the environment.

What is hazardous waste?

• Waste possessing properties -- toxicity, reactivity, corrosiveness, flammability, or infectiousness -- that make it dangerous or potentially harmful if improperly handled.
• Sources include industrial waste (chemical, pharmaceutical, electroplating, and metal-processing industries), hospital/biomedical waste (syringes, pathological waste), e-waste (discarded electronics containing heavy metals), agricultural waste (pesticide containers/residues), radioactive waste, and household hazardous waste (used batteries, paints, solvents).

Management methods, roughly in order of preference

1. Waste minimisation/source reduction -- redesigning industrial processes or substituting less hazardous raw materials to generate less hazardous waste in the first place; this is the most effective and preferred approach.
2. Segregation, reuse, and recycling -- separating hazardous from non-hazardous waste at source, and recovering and reusing valuable materials (e.g., solvent recovery, metal reclamation) wherever possible.
3. Treatment -- reducing the volume or hazard of waste that must be disposed of, through:
   • Physical methods -- filtration, sedimentation, and segregation.
   • Chemical methods -- neutralisation of acids/alkalis, precipitation of heavy metals, oxidation-reduction reactions.
   • Biological methods -- bioremediation, using microorganisms to degrade certain organic hazardous compounds.
4. Incineration -- controlled high-temperature burning, especially suited to organic and biomedical hazardous waste, which destroys pathogens and reduces waste volume (with proper emission control to avoid secondary air pollution).
5. Solidification/stabilisation -- encapsulating hazardous waste within an inert, stable matrix (e.g., cement or polymer) to immobilise contaminants before disposal. …