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Chapter12presentation Chapter12presentation Presentation Transcript

  • Chapter 12 Solid and Liquid Wastes
  • Learning Objectives By the end of this chapter the reader will be able to: • Describe trends in the production of solid waste • Discuss methods for source reduction of solid waste • Discuss the role of landfills for disposing of solid waste • Describe methods for primary, secondary, and tertiary sewage treatment • Discuss hazards of poorly designed solid waste disposal sites and improperly processed sewage
  • Introduction • Ecosystems produce waste, and that waste needs to be appropriately disposed of or it would eventually destroy the ecosystem • Problems arise when the waste is not organically based and the number of single use items increases o Decomposition is reduced and wastes build up • The issues are: o Incinerators of the past are not ideal o Increases in pollution of aquatic environments o We are slowly running out of space for this waste so as a society we need to take a serious look at how we use, reuse, and dispose of waste View slide
  • Municipal Solid Waste (MSW) • Americans produce approximately 250 million tons of MSW (before recycling) each year. • About 4.5 pounds of waste per person per day • Refuse o • o • Garbage Organic putrescible matter from scraps of food Rubbish Combustible and non-combustible generated from various activity and sources • Paper, containers, beverage cans, wrappings, yard trimmings o Ashes • Combusted materials that have burned to total breakdown • Most of the time can be incorporated into the soil with very little negative impact View slide
  • Figure 12-2 Municipal solid waste generation rates, 1960–2008. Source: Adapted and reprinted from US Environmental Protection Agency, Solid Waste and Emergency Response (5306P). Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2008. Washington, DC: US Environmental Protection Agency; 2009, p.1.
  • Storage of MSW • Most homes use various receptacles to accumulate waste until it can be removed o Long term receptacles should be “fly-tight” and noncorrosive o Can be lined with bags for easy disposal or cleaned after they are emptied • Large-volume receptacles are used at businesses or multi-housing areas • Should be collected at least once per week (most areas it is twice) o Schedule is suggested based on the life cycle of the house fly o Collecting refuse weekly controls the fly population • Collection is through a private or government operation • Trucks must meet certain specifications for transporting and compacting refuse
  • Components of the MSW Stream • • • • • • • • Food waste Papers Batteries Organic materials Packaging Furniture Clothing Bottles
  • Components of MSW Disposal • Formerly completed through open-dumping and incineration • The EPA recommends that wastes are handled in other manners because of disease and other hazards to the environment o o o o o Source Reduction Recycle-Reuse Composting Waste to Energy (WTE) Landfill
  • Source Reduction • Source reduction refers to “reducing the amount of waste created, reusing whenever possible, and then recycling what is left.” • Achieved by reducing the amount of hazardous components in products, eliminating excess packaging, and making products last longer o Incentivize the public to throw out less o Design products so that they last longer o Design products that have a secondary use
  • Recycling • The EPA defines recycling (reuse) as the process of “Minimizing waste generation by recovering and reprocessing usable products that might otherwise become waste.” (i.e., recycling of aluminum cans, paper, and bottles, etc.) • Collection of materials to be used to make new products • Reduces the need for virgin sources, saves energy, and creates jobs • Still don’t or can’t recycle as much as we should
  • Recycling • We all need to recycle like this guy…
  • Recycling
  • Advantages of Recycling • Reduces emissions of greenhouse gases • Prevents pollution generated by the use of new materials • Decreases the amount of materials shipped to landfills • Preserves natural resources • Opens up new manufacturing employment opportunities • Saves energy
  • Composting “the aerobic biological decomposition of organic materials [e.g., leaves, grass, and food scraps] to produce a stable humus-like product…. Biodegradation is a natural, ongoing biological process that is a common occurrence in both human-made and natural environments.” • Materials must be separated and non biodegradable materials disposed of in some other manner • o Glass, plastic, rubber products, and metal • Produces a useful material that resembles soil and that can be used in gardening.
  • Composting Success • The state of Massachusetts has one of the most successful composting programs in the U.S. • Yard and food waste are composted, preventing 37,500 tons of waste from entering the disposal process and saving approximately $2 million each year.
  • Waste-to-Energy • Burn municipal waste to generate steam for electricity • Can decrease waste volume by 60 to 90%, while recovering energy from discarded products
  • Landfill Design • Solid waste buried in sections and covered with soil • Class I facilities serve municipal, institutional, residential and rural populations o o o o 100 ft from property lines 500 ft from residences 500 ft from wells 200 ft from springs, lakes, and other bodies of water • Constructed to prevent any leaching of waste into ground or surface water • A landfill is composed of four major parts: o o o o a bottom liner a system for collecting leachates a cover an appropriate location that minimizes the leaching of waste into groundwater
  • How a Landfill Works • The bottom is lined with a dense layer of clay and sealed with thick plastic sheeting to contain leaks of hazardous materials. • A flexible membrane liner holds in toxic chemicals that might contaminate groundwater. • A leachate sump collects leachates, which then can be subjected to further treatment. • Garbage is piled up in rows; bulldozers and rollers compact the garbage; at the end of the day, the newly added garbage is covered with soil and other materials. • After the garbage is covered, anaerobic bacteria aid in the decomposition of organic materials and produce methane gas.
  • Side View of a Landfill
  • Dangers Associated with Landfills • Air pollution and groundwater contamination • Leachates, which may include: o Toxic heavy metals o Solvents and cleaning agents. • Methane, volatile organic compounds (VOCs), and other gases o Methane vented from landfills poses a fire hazard and is a greenhouse gas. • VOC emissions o Potentially carcinogenic o May cause complaints about odors and symptoms of respiratory irritation
  • Federal Landfill Standards 1. Location restrictions 2. Composite liners requirements 3. Leachate collection and removal systems 4. Groundwater monitoring requirements 5. Closure and postclosure care requirements 6. Corrective action provisions 7. Financial assurance Source: Adapted and reprinted from US Environmental Protection Agency. Municipal Solid Waste: Landfills. Available at: http://www.epa.gov/osw/nonhaz/minicipal/landfill.htm. Accessed March 25. 2010.
  • Incineration • Can be used to generate energy while at the same time reducing the volume and weight of waste. • No attempt is made to separate the trash into components; at the high temperatures of incinerating plants, glass and aluminum in the trash melt. • Metals from the residues of combustion can be recycled into scrap metal; remaining ash is deposited in landfills.
  • Disadvantages of Incineration • Emissions may be potentially hazardous to human health and the environment. • Toxic materials emitted may cause air pollution or be deposited on the land.
  • Hazardous Materials and Wastes • Hazardous wastes are disposed of legally in the U.S. by: o o o o Discarding them on the surface of the land Storing them in slurry ponds Dumping them into landfills or into the ocean Incineration
  • Hazardous Materials and Wastes Characteristics… •Corrosive o Chemically wearing away substances o pH below 2 or above 12.5 •Toxic o Poisonous to people and other organisms •Ignitable o Capable of bursting into flames •Reactive o Capable of exploding or releasing poisonous gas when mixed with another substance or chemical
  • Group Questions o What household chemicals do people have in their homes or garages that are hazardous and that could become hazardous waste? o Do you think you or your family contribute to the hazardous waste problem? If so, how? o What problems could you, your family, and the community face as a result of being exposed to hazardous waste? o What businesses in your community do you think might use hazardous materials? o What are some ways hazardous waste problems can be prevented? Which of these things can you do?
  • Sources of Hazardous Wastes Hazardous materials used in the home •Pesticides, cleaning products, automotive products, painting supplies, and other flammable and nonflammable products Medical waste •Chemicals, infectious agents, and radioactive materials Industrial hazardous waste •Heavy metals from plating operations, toxic chemicals, solvents, and residues from the manufacture of pesticides
  • Sources of Hazardous Wastes Radioactive waste •Spent nuclear fuel and tailings from uranium processing Mining wastes and extraction wastes •Toxic chemicals left over from mining operations include acids and heavy metals.
  • Hazardous Waste Problem • More than 400 million tons are generated worldwide on an annual basis. • Developed world generates most of the toxic wastes. • Some developing nations will take hazardous wastes for cash payments; this practice may endanger the health of the local population.
  • Hazardous Waste Problem • How hazardous waste released into the environment can affect plants (flora) or animals (fauna) in an ecosystem. o o o o o o o o o o o Gaps in vital food chains or nutrient cycles Reproductive problems Developmental effects Tumors Critical organ damage Immune system dysfunction Altered individual or population growth rates Changes in population and community organization Loss of total biomass Relative loss of taxa or species abundance in defined areas Loss of species diversity.
  • Uncontrolled Hazardous Waste Sites in the U.S. • An estimated 40,000 of these sites have been reported to federal agencies. • 1,300 sites are on the National Priorities List (NPL). • Superfund legislation mandates the cleanup of hazardous waste sites.
  • Impacts of Uncontrolled Sites • • • • Potential adverse human health effects High costs of cleanup Reductions in property values Potential ecological damage
  • Love Canal • Was the former site for disposal of toxic wastes • Later used for residential construction • Became identified with hazardous chemical exposures and their possible harmful influences on human health • Led to the creation of the Superfund
  • Medical Waste • “any solid waste that is generated in the diagnosis, treatment, or immunization of human beings or animals, in research pertaining thereto, or in the production or testing of biologicals….” • More than 3.5 million tons are produced annually in the U.S.
  • Medical Waste Medical waste disposal methods •Shredding and Chlorinating o Reduces volume but comes with high costs and potential slurry contamination •Incinerator Technology o High temperature combustion to destroy organics in waste materials o Multiple chamber incinerators, Rotary kiln incinerators, and Controlled air incinerators •Thermal Plasma Technology o Exposes waste to intense incandescent heat o Chamber temps reach 20,000oF o Vaporizes materials into molecular components and sold off as construction material o Largely unproved and very costly
  • Sewage • “The waste and wastewater produced by residential and commercial sources and discharged into sewers.” • Water containing human waste is known as sewage o Usually about 1% of the content o U.S. law requires the removal of human excrement in a sanitary manner • Treatment of human waste is divided into two main types: o Non-water-carried o Water-carried
  • Wastewater Treatment • Non-water-carried systems o Pit privy (pit latrine or outhouse) • No water is available to flush waste away to a treatment plant • Once full, hole is covered, and the structure is moved to a new location o Box and can • Waste is contained until it can be removed and treated • Used in “port-a-pots”, on buses, campers, planes, etc
  • Wastewater Treatment • Individual water-carried systems o Septic Tank System • Waste water initially passes through a trap under the sink or toilet before it continues through the pipes out the house • The pipe then enters the septic tank o Goal of a septic tank and drainfield system is to filter out as much solid as possible then allow plants to draw the waste water from the soil (transpiration) or to the surface to evaporate • Evapotranspiration
  • Wastewater Treatment • Individual water-carried systems o Not all soils are capable of handling enough absorption of water • Perc Test (percolation test) o Hole is dug and filled with water to determine the rate at which water drains out of the hole o The faster the drainage, the better o Type of soils will also determine percolation rate o Drainfield areas should be well clear of surface water such as streams, ponds, water supplies, dwellings, property lines etc. o Health department must inspect systems before they are backfilled
  • Wastewater Treatment • Individual water-carried systems o Septic Tank System • The septic tank serves three functions 1. Settling basin for removal of solids as sludge 2. Stores sludge and scum until it can be removed 3. Provides a chamber for biological decomposition • Biological activity is anaerobic and produces gasses o CO2, H2S, CH4, as well as water o Gas travels back through the lines and out the house vent
  • Drainfield System
  • Septic Tank
  • Municipal Wastewater Treatment • Modern technology involves : o Removing solids o Deactivating microbes o Producing wastewater that can be returned safely to waterways or in some cases can be reused or recycled. • Wastewater exits a dwelling through the same pipes as it would for a septic system o Flows into a sanitary sewer to be transported to a treatment facility • Storm sewers however do not use the same pipes and do not go to a treatment facility o Wastewater that enters a treatment facility flows first through a bar screen and grit chamber
  • Municipal Wastewater Treatment • Typically, sewage treatment involves three stages, called primary, secondary and tertiary treatment. • The primary stage aims to remove large materials, which can be composted or shipped to landfills. • Secondary processing promotes microbial digestion of organic material that remains in the sewage. o Microorganisms that are present naturally in sewage or that may be added to enhance microbial action aid in the digestion of the liquor during aeration. • Tertiary (high-level) processing is directed at removal of remaining solids and microorganisms from the liquid portion of sewage.
  • Sewage Processing System Primary Tank Secondary Processing Aeration Empty Aeration Tank Source: Author. Courtesy of the Irvine Ranch Water District, Irvine, California.
  • U.S. Sewage Requirements • Most jurisdictions in the U.S. require that wastewater receive at least secondary treatment. • Water that has received only primary treatment is not recommended for any use and generally needs secondary or tertiary treatment for common purposes such as landscape irrigation.
  • Wastewater stabilization ponds • Used when treatment volume is low or areas cannot afford treatment plants • Uses large ponds with a depth of about 4 feet • Uses biological decomposition to dispose of wastes • Anaerobic process at the bottom creates gasses that accelerates the aerobic activity towards the top • The stabilization pond is designed to receive no more than 50 pounds of BOD 5 per day per acre.  o The biochemical oxygen demand , or BOD 5 , is the amount of organic matter which can be biologically oxidized in 5 days at 20°C in the dark.  This is a way of measuring how much organic matter is in the water • The effluent is chlorinated as it flows out of the pond into a surface water supply
  • Wastewater stabilization ponds
  • Composting toilets
  • Water Pollution According to the American College Dictionary, pollution is defined as:  “to make foul or unclean; dirty.” Two types of water pollutants exist - point source and nonpoint source.   Point sources of pollution occur when harmful substances are emitted directly into a body of water.   The technology exists for point sources of pollution to be monitored and regulated  A nonpoint source delivers pollutants indirectly through environmental changes.   Nonpoint sources are much more difficult to control.   Pollution arising from nonpoint sources accounts for a majority of the contaminants in streams and lakes
  • Hazards Posed by Animal Wastes • Contamination from nutrients, organic materials, microorganisms, residues of medicines, and potentially toxic gases • Workers in contact with livestock exposed to pathogenic microorganisms • Creation of antibiotic-resistant bacteria that may endanger human health
  • Groundwater Contamination • Once dissolved, pollutants can move along with water to holding areas o Plume • Area of contaminated ground water • May be several miles long o Light non-aqueous phase liquids • Liquid contaminants that are lighter than water witch will then float towards the top o Dense non-aqueous phase liquids • Dense contaminant that forms pools at the bottom of an aquifer