Q.Explain management of hazardous wastes.

Hazardous wastes are managed by reduce–recycle at source, safe collection/storage/transport, treatment (neutralisation, incineration, solidification), and secure landfill disposal; special wastes (biomedical, radioactive, e-waste) need dedicated handling under strict laws.

Hazardous wastes are waste materials that pose a substantial danger to human health or the environment because of their harmful properties — they may be toxic (poisonous), corrosive, inflammable (easily catch fire), reactive/explosive, or infectious. They include many industrial chemical wastes, heavy metals, pesticides, biomedical (hospital) waste, radioactive waste and electronic waste (e-waste). If dumped carelessly, they pollute soil, water and air and cause diseases, so they must be managed scientifically.

Management of hazardous wastes:

1. Reduction at source (minimisation): the first and best step is to generate less hazardous waste — by using cleaner production processes, substituting less harmful materials, and improving efficiency so that fewer toxic by-products are formed.
2. Recycling and recovery: wherever possible, useful materials (metals, solvents, etc.) are recovered and recycled from the waste, reducing both the quantity to be disposed of and the demand for fresh resources.
3. Safe collection, storage and transport: hazardous waste must be segregated from ordinary waste, clearly labelled, and stored and transported in strong, leak-proof, corrosion-resistant containers to prevent spills and exposure.
4. Treatment to reduce hazard: the waste is treated to make it less harmful before disposal, for example:

• Chemical treatment — neutralising acids and alkalis, precipitating heavy metals, detoxifying chemicals.
• Incineration — burning combustible and biomedical wastes at very high temperature in special incinerators, which destroys organic toxins and pathogens and reduces volume (the flue gases must be cleaned).
• Solidification/encapsulation — mixing/immobilising the waste in cement or glass so that harmful substances cannot leach out.

5. Safe disposal (secured landfill): treated and residual hazardous wastes are finally disposed of in specially engineered 'secure' or 'sanitary' landfills. These have impermeable liners (clay/plastic) at the bottom, systems to collect and treat the leachate (the liquid that seeps out), and covers to prevent rain infiltration — so that toxins do not reach the soil and groundwater. The site is monitored for a long time.
6. Special categories need special methods:

• Biomedical/hospital waste: segregated (colour-coded bags), disinfected (autoclaving/chemical) and incinerated as per biomedical waste rules. …