Hazardous waste

Threatens human health or the environment in some way because it is –toxic –chemically active –corrosive –flammable –or some combination of the above The two largest classes of hazardous wastes are organic compounds (e.g. pesticides, PCBs, dioxins) and toxic heavy metals (e.g. lead, mercury, arsenic).

DEALING WITH HAZARDOUS WASTE Options: –produce less hazardous waste or –recycle, reuse, detoxify, burn, and bury what we continue to produce –Store forever Figure 22-16

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. Incineration: heating many types of hazardous waste to high temperatures – up to 2000 °C – in an incinerator can break them down and convert them 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. –Phytoremediation: involves using natural or genetically engineered plants to absorb, filter and remove contaminants from polluted soil and water. (video)

Phytostabilization Plants such as willow trees and poplars can absorb chemicals and keep them from reaching groundwater or nearby surface water. 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. 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. 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. Inorganic metal contaminants Organic contaminants Radioactive contaminants Brake fern Poplar tree Indian mustard Willow tree Sunflower Oil spill Landfill Groundwater Soil Polluted leachate Decontaminated water out Polluted groundwater in Groundwater Soil

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 Long-Term Retrievable Storage Secure Landfills

Love Canal 21,000 tons of toxic waste was buried by Hooker Chemical Co. in the 1940s and 1950s in Love Canal, a neighborhood in Niagara Falls, NY. Love Canal sparked creation of the Superfund law, which forced polluters to pay for cleaning up abandoned toxic waste dumps. Video 1 Video 2

Brownfields Abandoned industrial/commercial sites that are contaminated with hazardous waste –eg gas stations, factories, junkyards, old landfills Can be cleaned up and used for new purposes EPA Brownfields Program gives low interest loans to companies or groups that are willing to clean up an area and repurpose it.

Hazardous Waste Regulations in the United States Two major federal laws regulate the management and disposal of hazardous waste in the U.S.: –Resource Conservation and Recovery Act (RCRA) Cradle-to-the-grave system to keep track of hazardous material and waste. –Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Commonly known as Superfund program.

CERCLA (1980) Established management requirements for closed and abandoned hazardous waste sites. Provided for liability of persons responsible for releases of hazardous waste at these sites. Established a trust fund (by taxing chemical & petroleum industries) to provide for cleanup when no responsible party could be identified. Authorizes two kinds of response actions: Short-term removals: where actions may be taken to address releases or threatened releases requiring prompt response (ie situations that are immediately life-threatening). Long-term remediation: that permanently and significantly reduces the dangers associated with releases hazardous substances that are serious, but not immediately life threatening.

International agreements Basel Convention (1989) –Requires permission to be given by developing countries before hazardous wastes are shipped to them by developed countries –The US has signed but not ratified. Persistent Organic Pollutants Treaty (2001) –Originally called the Stockholm Treaty –An international agreement to phase out 12 (POPs) including DDT and PCBs. –The US has signed but not ratified.