Section 19 vid 1

Definition of Hazardous Waste

  • Hazardous waste refers to discarded materials (liquid or solid) that may:

    • Explode

    • Release toxic fumes

  • Legally defined as containing at least one of 39 toxic compounds (e.g., mutagenic, carcinogenic, teratogenic) exceeding established limits.

  • Examples include:

    • Solvents and pesticides

    • Highly flammable materials (paints, gasoline)

    • Reactive waste releasing toxic fumes (chlorine bleach, ammonia)

    • Corrosive waste (drain cleaners, industrial cleaning agents)

Major Classes of Hazardous Waste

Organic Compounds

  • Dioxins, PCBs, and pesticides are significant hazardous organic compounds.

Toxic Heavy Metals

  • Arsenic, mercury, lead are the most toxic heavy metals.

  • Only about 5% regulated by the Resource Conservation and Recovery Act (RCRA) of 1976, amended in 1984.

RCRA Overview

  • RCRA is a waste management program empowering the EPA to oversee the disposal of both hazardous and nonhazardous waste.

  • The EPA supports states in managing hazardous waste from generation to disposal (cradle to grave).

  • Key responsibilities of the EPA include:

    • Criteria for hazardous waste generation

    • Transportation, treatment, and storage

    • Disposal facilities management

    • Permitting and enforcement

CERCLA Overview

  • Superfund program, established under CERCLA (1980), funds cleanup of contaminated areas.

    • Creates a national priorities list of hazardous waste sites needing cleanup based on priority.

  • Difference between RCRA and CERCLA:

    • RCRA: Manages hazardous waste at operating facilities.

    • CERCLA: Manages and remediates abandoned or contaminated sites with no identified responsible party.

Brownfields Program

  • An EPA program offering funding for cleanup and reuse of abandoned sites contaminated by hazardous waste (e.g., former junkyards, gas stations).

Limitations of Hazardous Waste Definition

  • The government definition does not cover certain wastes:

    • Oil and gas drilling wastes

    • Household hazardous materials

    • Liquid hazardous waste containing hydrocarbons (80% of liquid hazardous waste)

    • Cement kiln dust

    • Small business waste (<100 kilograms/month)

    • Radioactive and mining wastes

Remediation Methods

Chemical and Physical Management

  • Detoxification through:

    • Incineration at high temperatures

    • Plasma torch burning

  • Physical methods include:

    • Deep well disposal

    • Storage in lagoons or pits (deemed inadequate)

    • Secure hazardous waste landfills

  • Advantages and disadvantages of burning:

    • Reduces volume, decreases water pollution, but may release toxic dioxins.

    • Residual ash requires disposal.

  • Advantages and disadvantages of burying waste:

    • Easy, inexpensive, but secured only as well as ground stability.

    • Risks of earthquakes causing leaks.

Biological Remediation

  • Bioremediation:

    • Uses microorganisms to degrade toxic substances into harmless compounds.

    • Works with both aerobic and anaerobic conditions.

  • Phytoremediation:

    • Uses plants to absorb, filter, and remove contaminants from soil and water.

    • Effective for shallow contamination but takes longer and has limitations on certain metals.

Prevention

  • Emphasis on minimizing the personal, industrial, and commercial use of hazardous materials.

Research Update

  • An experiment on phytoremediation with flowering brassicas showed they need five crops for safe thallium levels.

  • Conclusion: C) Flowering brassica is preferable to green cabbage due to shorter remediation time (30+ years for cabbage).

Summary

  • Various methods to manage hazardous waste exist, each with pros and cons.

  • Prevention remains the best strategy against hazardous waste generation.