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

Problems Caused by Growing

Volume of Waste

• Difficulties in disposal

• Dump sites being filled

• Increases in pollution of aquatic environments,

e.g., waterways and oceans

Municipal Solid Waste (MSW)

• This is trash or garbage.

• In 2008, the United States–residents,

businesses, and institutions–produced

approximately 250 million tons of MSW

(before recycling).

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.

Figure 12-2 Municipal solid waste

generation rates, 1960–2008.

Components of the MSW Stream

(Examples)

• Packaging

• Furniture

• Clothing

• Bottles

• Food waste

• Papers

• Batteries

• Organic materials

Total MSW Generation (by Material), 2008--

250 Million Tons (Before Recycling)

Source: Adapted and reprinted from U.S. 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:

U.S. Environmental Protection Agency; 2009, p. 4.

The Four Dimensions

of MSW Disposal

• Recycling

• Landfilling

• Composting

• Combustion

Major Components of MSW Management

Source: Reprinted from U.S. Department of Energy, Energy Information Administration, Office of Coal, Nuclear, Electric

and Alternate Fuels. Available at:

http://www.eia.doe.gov/cneaf/solar.renewables/renewable.energy.annual/backgrnd/fig8.htm. Accessed May 2, 2010.

EPA’s Hierarchy for Management

of MSW

• From more favored to less favored

– Source reduction

– Recycling

– Disposal

Source Reduction

• Source reduction refers to “reducing the

amount of waste created, reusing whenever

possible, and then recycling what is left.”

Components of Source Reduction

• Two important components

– Waste reduction aims to reduce the amount of

waste produced at the source.

– Waste recycling refers to reuse of materials in the

waste.

Programs for Recycling Wastes

Source: Adapted and reprinted from U.S. Environmental Protection Agency, Recycle City, Dumptown Game. Available at:

http://www.epa.gov/recyclecity/gameint.htm. Accessed March 25, 2010.

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.).”

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

Recycling Rates

Source: Adapted and reprinted from U.S. 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: U.S. Environmental Protection Agency;

2009, pp. 2, 3.

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.”

• 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.

Landfill Design

• A landfill is composed of four major parts:

– a bottom liner

– a system for collecting leachates

– a cover

– an appropriate location that minimizes the

contamination of groundwater by materials

released from the site

Side View of a Landfill

Source: Adapted and reprinted from U.S. Department of Energy, U.S. Energy Information Administration. Energy

explained. Available at: http://tonto.eia.doe.gov/energyexplained/images/landfill.gif. Accessed May 4, 2010.

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.

How a Landfill Works (continued)

• 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.

Dangers Associated with Landfills

• Air pollution and groundwater contamination

• Leachates, which may include:

– Toxic heavy metals

– Solvents and cleaning agents.

• Gases such as methane

Gaseous Emissions from Landfills

• Methane, volatile organic compounds (VOCs),

and other gases

– Methane vented from landfills poses a fire hazard

and is a greenhouse gas.

• VOC emissions

– Potentially carcinogenic

– May cause complaints about odors and symptoms

of respiratory irritation

Megafills

• Megafills take in from 5,000 to 10,000 tons of

trash per day and serve regional needs for

waste disposal.

• Tend to be more cost effective than incinerators

for disposal of solid waste.

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.

Disposal of Hazardous

Materials and Wastes

• Hazardous wastes are disposed of legally in

the U.S. by:

– Discarding them on the surface of the land

– Storing them in slurry ponds

– Dumping them into landfills or into the ocean

– Incineration

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

(continued)

• 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.

Scope of the 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.

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.

Toxic Waste Dump and Workers in

Protective Clothing

Source: Reprinted from CDC Public Health Image Library, ID #1193 and ID #1530. Available at: http://phil.cdc.gov/Phil/details.asp. Accessed

March 25, 2010.

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.

Definition of Sewage

• “The waste and wastewater produced by

residential and commercial sources and

discharged into sewers.”

History of Sewage Disposal

• Romans constructed a sewage system and

aqueducts.

• The Middle Ages were a time of regression for

the sanitary disposal of sewage.

• During the 19th century, methods for the

treatment of sewage began to improve.

Modern Sewage Treatment

and Disposal

• Modern technology involves :

– Removing solids

– Deactivating microbes

– Producing wastewater that can be returned safely

to waterways or in some cases can be reused or

recycled.

Primary Stage of

Sewage Treatment

• The primary stage aims to remove large

materials, which can be composted or shipped

to landfills.

Secondary Stage of

Sewage Treatment

• Secondary processing promotes microbial

digestion of organic material that remains in

the sewage.

• 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 Stage of

Sewage Treatment

• Tertiary (high-level) processing is directed at removal of remaining solids and microorganisms from the liquid portion of sewage.

• Various methods exist for high-level processing including filtration through sand and charcoal filters and deactivation of microorganisms (disinfection) by using chlorine or UV radiation.

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.

Other Methods for Sewage

Disposal

• Composting toilets

• Septic systems

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