Hazardous Waste

HAZARDOUS WASTE Hazardous waste: discarded solid or liquid material that is toxic, ignitable, corrosive, or reactive enough to explode or release toxic fumes. The two largest classes of hazardous wastes: organic compounds pesticides, PCBs, dioxins toxic heavy metals lead, mercury, arsenic

What Harmful Chemicals Are in Your Home? Cleaning Gardening • Disinfectants • Pesticides • Drain, toilet, and window cleaners • Weed killers • Ant and rodent killers • Spot removers • Septic tank cleaners • Flea powders Paint Automotive • Latex and oil-based paints • Gasoline • Paint thinners, solvents, and strippers • Used motor oil • Antifreeze • Stains, varnishes, and lacquers • Battery acid • Solvents Figure 22.15 Science: harmful chemicals found in many U.S. homes. The U.S. Congress has exempted disposal of these materials from government regulation. QUESTION: Which of these chemicals are in your home? • Wood preservatives • Brake and transmission fluid • Artist paints and inks General • Rust inhibitor and rust remover • Dry-cell batteries (mercury and cadmium) • Glues and cements Fig. 22-15, p. 534

Two major federal laws regulate hazardous waste in the U.S.: Resource Conservation and Recovery Act (RCRA) 1976 Cradle-to-the-grave system to keep track waste. Requires EPA to set standards for hazardous waste Permit for more that 100kg per month Guidelines/financial aid to help state programs Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Commonly known as Superfund program.

Guess what percent of hazardous wastes in the U. S Guess what percent of hazardous wastes in the U.S. are not regulated by hazardous-waste laws? 95%

Brownfields Land that was polluted by industrial or commercial uses. (Link) Cleaning up and reinvesting in these properties protects the environment, and takes development pressures off green spaces and working lands. Does not include superfund sites.

Conversion to Less Hazardous Substances Physical Methods: using charcoal or resins to separate out harmful chemicals. Chemical Methods: using chemical reactions that can convert hazardous chemicals to less harmful or harmless chemicals.

Conversion to Less Hazardous Substances Biological Methods: Bioremediation: bacteria or enzymes help destroy toxic and hazardous waste or convert them to more benign substances. Pros: can be cheaper than landfills if toxin-degrading bacteria can be found. Cons: works for a few specific ORGANIC wastes Ex. Oil spills

Ex. desalination of agricultural land Phytoremediation: involves using natural or genetically engineered plants to absorb, filter and remove contaminants from polluted soil and water. Ex. desalination of agricultural land

Radioactive contaminants Organic contaminants Inorganic metal contaminants Poplar tree Brake fern Sunflower Willow tree Indian mustard Rhizofiltration Roots of plants such as sunflowers with dangling roots on ponds or in green- houses can absorb pollutants such as radioactive strontium-90 and cesium-137 and various organic chemicals. Phytostabilization Plants such as willow trees and poplars can absorb chemicals and keep them from reaching groundwater or nearby surface water. Phytodegradation Plants such as poplars can absorb toxic organic chemicals and break them down into less harmful compounds which they store or release slowly into the air. Phytoextraction Roots of plants such as Indian mustard and brake ferns can absorb toxic metals such as lead, arsenic, and others and store them in their leaves. Plants can then be recycled or harvested and incinerated. Landfill Polluted groundwater in Oil spill Figure 22.17 Solutions: phytoremediation. Various types of plants can be used as pollution sponges to clean up soil and water and radioactive substances (left), organic compounds (center), and toxic metals (right). (Data from American Society of Plant Physiologists, U.S. Environmental Protection Agency, and Edenspace) Polluted leachate Decontaminated water out Soil Soil Groundwater Groundwater

Aesthetically pleasing Trade-Offs Phytoremediation Advantages Disadvantages Easy to establish Slow (can take several growing seasons) Inexpensive Less erosion Aesthetically pleasing Less habitat Destruction vs. removing soil and taking it to a land fill Vegetation is now hazardous May introduce exotic species Effective only at depth plant roots can reach Can reduce material dumped into landfills Some toxic organic chemicals may evaporate from plant leaves Produces little air pollution compared to incineration Figure 22.18 Trade-offs: advantages and disadvantages of using phytoremediation to remove or detoxify hazardous waste. QUESTION: Which single advantage and which single disadvantage do you think are the most important? Some plants can become toxic to animals Low energy use Fig. 22-18, p. 538

Conversion to Less Hazardous Substances Incineration: heating many types of hazardous waste to high temperatures – up to 2000 °C (3,600 ° F)– in an incinerator can break them down and convert them to less harmful or harmless chemicals. Cons- same as before, toxic ash

Conversion to Less Hazardous Substances Plasma Torch: passing electrical current through gas to generate very high temperatures (10,000oC or 18,000oF) can create plasma. The plasma process can be carried out in a torch which can decompose liquid or solid hazardous organic material.

Mobile. Easy to move to different sites Produces CO2 and CO Trade-Offs Plasma Arc Advantages Disadvantages Small High cost Mobile. Easy to move to different sites Produces CO2 and CO Can release particulates and chlorine gas Produces no toxic ash Figure 22.19 Trade-offs: advantages and disadvantages of using a plasma arc torch to detoxify hazardous wastes. QUESTION: Which single advantage and which single disadvantage do you think are the most important? Can vaporize and release toxic metals and radioactive elements Fig. 22-19, p. 538

Long-Term Storage of Hazardous Waste Deep-well disposal: liquid hazardous wastes are pumped under pressure into dry porous rock far beneath aquifers. Surface impoundments: excavated depressions such as ponds, pits, or lagoons into which liners are placed and liquid hazardous wastes are stored.

Long-Term Storage of Hazardous Waste: Chemicals you can’t detoxify Long-Term Retrievable Storage: Metal drums stored them in areas that can be inspected Secure Landfills: waste are put into drums and buried in carefully designed and monitored sites.

Case Study: Lead Lead is especially harmful to children Leaded gas, paint Partial paralysis Mental retardation Palsy Neurological damage Stored in bones Lead Pollution More info Figure 22-24

high levels in some types of fish neurotoxin Minamata disease Case Study: Mercury burning coal incinerating wastes high levels in some types of fish neurotoxin Minamata disease More info Figure 22-26

Fig. 22-25, p. 542 AIR WINDS PRECIPITATION WINDS PRECIPITATION Hg and SO2 Hg2+ and acids Hg2+ and acids Photo- chemical Human sources Elemental mercury vapor (Hg) Inorganic mercury and acids (Hg2+) Inorganic mercury and acids (Hg2+) Coal- burning plant Incinerator Deposition Runoff of Hg2+ and acids Deposition WATER Large fish Vaporization Deposition Small fish BIOMAGNIFICATION IN FOOD CHAIN Deposition Figure 22.25 Science: cycling of mercury in aquatic environments, in which mercury is converted from one form to another. The most toxic form to humans is methylmercury (CH3Hg+), which can be biologically magnified in aquatic food chains. Some mercury is also released back into the atmosphere as mercury vapor. QUESTION: What is your most likely exposure to mercury? Phytoplankton Zooplankton Bacteria and acids Oxidation Elemental mercury liquid (Hg) Inorganic mercury (Hg2+) Organic mercury (CH3Hg+) Bacteria Settles out Settles out Settles out SEDIMENT Fig. 22-25, p. 542

Global Outlook: International Action to Reduce Hazardous Waste Stockholm Convention: An international treaty calls for phasing out POPs (persistent organic pollutants) POPs are soluble in fat. The U.S has not ratified this treaty. DDT, PCBs, dioxins, other chlorine containing pesticides Basel Convention: stops shipping of hazardous waste to countries without permission. (usually developed to developing)