Landfills and Hazardous Wastes

Landfills In landfills, waste is buried in the ground or piled up in large, carefully engineered mounds In landfills, waste is buried in the ground or piled up in large, carefully engineered mounds

Landfills Waste is partially decomposed by bacteria and compresses under its own weight to take up less space Waste is partially decomposed by bacteria and compresses under its own weight to take up less space Waste is layered along with soil, which speeds decomposition, reduces odor, and lessens infestation by pests Waste is layered along with soil, which speeds decomposition, reduces odor, and lessens infestation by pests

Landfills and the environment The Resource Conservation and Recovery Act (RCRA) of 1984 specifies how waste should be added to a landfill The Resource Conservation and Recovery Act (RCRA) of 1984 specifies how waste should be added to a landfill Landfill engineers protect against environmental contamination Landfill engineers protect against environmental contamination –Landfills must be located away from wetlands and earthquake-prone faults –The bottoms and sides must be lined with thick plastic and clay to prevent water contamination

Landfills and the environment Landfills produce leachate, which is a liquid that results when substances from the trash dissolve in water as rainwater percolates downward Landfills produce leachate, which is a liquid that results when substances from the trash dissolve in water as rainwater percolates downward –Landfills have systems of pipes running from the bottom of the landfill to collection ponds and treatment facilities

Landfills after closure After a landfill is closed, it is capped with an engineered cover that must be maintained After a landfill is closed, it is capped with an engineered cover that must be maintained –a barrier of plastic that prevents water infiltration and gas escaping –a gravel layer which drains water –a barrier of soil that stores water and protects the plastic layer from the weather –And a topsoil layer of at least 15 cm which promotes vegetation growth

Landfills after closure Many smaller landfills have been closed and trash is sent into much larger landfills Many smaller landfills have been closed and trash is sent into much larger landfills Many cities have been converting closed landfills into public parks Many cities have been converting closed landfills into public parks –The site where Shea Stadium is today was once a landfill

Negatives to landfills Leachate may still escape from landfills, even if well protected Leachate may still escape from landfills, even if well protected –Liners may rip or the systems may malfunction The bacteria that decompose materials need wet conditions, but this increases leachate The bacteria that decompose materials need wet conditions, but this increases leachate –Dry conditions slow decomposition: landfills often contain food and 40-year-old newspapers

Negatives to landfills Finding suitable areas for landfills is difficult Finding suitable areas for landfills is difficult –Landfills are rarely located in wealthy areas and are located disproportionately in poor and minority communities

Incinerating trash Incineration, or combustion, is a controlled process in which mixed garbage is burned at very high temperatures Incineration, or combustion, is a controlled process in which mixed garbage is burned at very high temperatures Metals are usually removed and the remainder of the waste is broken into small pieces Metals are usually removed and the remainder of the waste is broken into small pieces This reduces the weight up to 75% and its volume up to 90% This reduces the weight up to 75% and its volume up to 90%

Incinerating trash The ash remaining may be toxic and disposed of up hazardous waste landfills The ash remaining may be toxic and disposed of up hazardous waste landfills Hazardous chemicals may be released into the atmosphere Hazardous chemicals may be released into the atmosphere –Scrubbers are added to chemically treat the gases (esp. SO2 and HCl) –Filters remove particulate matter

Using waste to create energy Waste-to-energy (WTE) facilities use the heat produced be waste combustion to boil water, creating steam that drives electricity generation Waste-to-energy (WTE) facilities use the heat produced be waste combustion to boil water, creating steam that drives electricity generation –This produces 35% of the energy generated by burning coal –This is not done in the US Landfill gas is produced be anaerobic decomposition in landfills—used in the same way as natural gas Landfill gas is produced be anaerobic decomposition in landfills—used in the same way as natural gas

Hazardous Wastes Ignitability: substances that easily catch fire (ex) alcohol) Ignitability: substances that easily catch fire (ex) alcohol) Corrosivity: substances that corrode metals in storage tanks or equipment Corrosivity: substances that corrode metals in storage tanks or equipment Reactivity: substances that are chemcialle unstable and readily reach with other compounds, often explosively or by producing fumes Reactivity: substances that are chemcialle unstable and readily reach with other compounds, often explosively or by producing fumes Toxicity: substances that harm human health when they are inhaled, are ingested, or contact human skin Toxicity: substances that harm human health when they are inhaled, are ingested, or contact human skin

Where do hazardous wastes come from? Industry produces the largest amount of hazardous waste, but the disposal is highly regulated Industry produces the largest amount of hazardous waste, but the disposal is highly regulated Households are currently the largest source of unregulated hazardous waste Households are currently the largest source of unregulated hazardous waste –Includes paints, batteries, oils, solvents, cleaning agents, lubricants, and pesticides

Heavy metals are hazardous Lead, chromium, mercury, arsenic, cadmium, tin, and copper are used widely in industry for wiring, electronics, metal plating, metal fabrication, pigments, and dyes Lead, chromium, mercury, arsenic, cadmium, tin, and copper are used widely in industry for wiring, electronics, metal plating, metal fabrication, pigments, and dyes When disposed of improperly, these metals can enter the environment When disposed of improperly, these metals can enter the environment These metals are prone to bioaccumulation because they are fat- soluble and break down slowly These metals are prone to bioaccumulation because they are fat- soluble and break down slowly –Ex) mercury in fish

Disposing of hazardous waste Landfills have strict regulations when receiving hazardous wastes Landfills have strict regulations when receiving hazardous wastes –They need thicker liners than normal landfills and must be located far from aquifers –These landfills do not lessen the hazards, but keep them away from humans and wildlife

Hazardous Waste Landfill

Above Ground Hazardous Waste Disposal

Disposal of hazardous waste Deep-well injection is a well drilled deep beneath the water table, reaching into porous rock Deep-well injection is a well drilled deep beneath the water table, reaching into porous rock –Wastes are injected into the well and remains deep underground –This does not work very well since the wells corrode and leak

Disposal of hazardous waste Surface impoundments store waste in liquid form Surface impoundments store waste in liquid form –A shallow depression is dug and lined with plastic and impervious clay layers –The waste is diluted and place in the pond and allowed to evaporate –The dry matter is removed and transported elsewhere –These ponds may crack and leak, or overflow

Radioactive Hazardous Wastes Radioactive wastes are prevalent with nuclear energy and are especially hard to dispose of due to their long half-lives Radioactive wastes are prevalent with nuclear energy and are especially hard to dispose of due to their long half-lives Yucca Mountain in Nevada has been approved as the single-site repository for all US nuclear waste Yucca Mountain in Nevada has been approved as the single-site repository for all US nuclear waste

Cleaning up contaminated sites Many thousands of former military and industrial sites remain contaminated with hazardous waste Many thousands of former military and industrial sites remain contaminated with hazardous waste In 1980, the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) established a federal program to clean up US sites polluted with hazardous wastes In 1980, the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) established a federal program to clean up US sites polluted with hazardous wastes –The EPA administers the program, called Superfund

Cleaning up contaminated sites Superfund Superfund –Experts identify sites polluted with hazardous chemicals, take action to protect groundwater near these sites, and clean up the pollution –The polluter is supposed to pay for the cleanup, but in many cases the responsible parties cannot be found or held liable  In this case, they are paid for from the federal budget ($1.4 billion in 2005) and a trust fund (went bankrupt in 2004) –In 2005, 966 of the 1547 Superfund sites had been cleaned up