CH. 21 SOLID AND HAZARDOUS WASTE

APES Mrs. Soja

I. THE SOLID WASTE PROBLEM

A. Solid Waste - any unwanted material that is solid

1. The U.S. produces 11,000,000,000 tons per year (4.3 pounds per day) about 33% of the world’s total

2. Waste Stream: the steady flow of wastes that humans produce from all sources

 

SOURCES OF SOLID WASTE

A. Mining waste 1. Makes up 75% of all waste, but

much of that is used soil or spoil 2. Mining wastes are left in large

piles called slag heaps that can contaminate air and water.

 

Fig. 21.2, p. 519

Municipal1.5%

Sewage sludge1%

Mining and oiland gas

production75% Industry

9.5%Agriculture

13%

Fig. 21.3, p. 519

Burned in incinerators (16%)

Dumped inlandfills

(54%)

Recycled orcomposted

(30%)

B. Industrial Solid Waste:

1. Scrap metal, plastics, paper, fly ash and sludge2. Most is burned or buried on-site 

C. Municipal Solid Waste (MSW)

1. From homes and businesses2. 700kg per person per year3. 60% dumped, 24% recycled, 16% burned

III. DISPOSAL OF SOLID WASTE

A. Open Dumps - Most common method in developing countries

1. Manila: 10 huge dumps•Thousands of people live and work on dumps scavenging for food & materials: Very unsafe

2. Cairo: Traditional garbage collectors live with their trash

3. Outlawed in most developed countries, but still happens

a. Dumping of materials like oil and paints: one liter can make 1,000,000 liters undrinkable

B. Sanitary Landfills

1. Stops problems with insects, rodents, cheap, low odor2. Litter is compacted and covered 6” every day3. Problems Associated with Sanitary Landfills a. New landfills (15%) are lined with plastic and clay to

prevent leachate from getting into groundwater. Liners are only required in new landfills and only last for 30 years before they leak. Leachate is rainwater that gets contaminated as it moves through the landfill.

b. 60% of solid waste ends up in landfills, 50% of U.S. cities have used landfill space

c. Methane gas produced by decomposing microbes d. Cause traffic, noise and dust and deprive us of

resources.

http://videos.howstuffworks.com/hsw/16921-the-garbage-story-an-introduction-video.htm

Fig. 21.12, p. 537

Topsoil

Sand

Clay

Garbage

Garbage

Sand

Synthetic liner

Sand

Clay

Subsoil

When landfill is full,layers of soil and clayseal in trash

Methane storageand compressor

building

Electricitygeneratorbuilding

Leachatetreatment system

Methane gasrecovery

Pipe collect explosivemethane gas used as fuel

to generate electricity

Compactedsolid waste

Leachatestorage tanks

Leachatemonitoringwell

Leachatemonitoringwell

GroundwaterGroundwater

Groundwatermonitoringwell

Groundwatermonitoringwell

Leachate pipesLeachate pipes Leachate pumped upto storage tanks for

safe disposal

Leachate pumped upto storage tanks for

safe disposal

Clay and plastic liningto prevent leaks; pipescollect leachate from

bottom of landfill

Fig. 21.13, p. 538

AdvantagesNo open burningLittle odorLow groundwaterpollution if sitedproperlyCan be builtquicklyLow operatingcostsCan handle largeamounts of waste

Filled land canbe used for otherpurposes

No shortage oflandfill space inmany areas

DisadvantagesNoise and trafficDustAir pollution fromtoxic gases andvolatile organiccompoundsreleasegreenhousegases (methaneand CO2)

Groundwatercontamination

Slowdecompositionof wastes

Encourages waste production

Eventually leaksand cancontaminategroundwater

Fig. 21.14, p. 538

Advantages

Safe method ifsites are chosencarefully

Wastes can beretrieved ifproblemsdevelop

Low cost

Disadvantages

Leaks or spills atsurface

Leaks fromcorrosion of wellcasing

Existing fracturesor earth quakescan allow wastesto escape intogroundwater

Encourageswaste production

4. Energy from Landfills

a. Methane gas is produced by anaerobic microbes within the fill; can be harnessed for energyb. Still adds to global warming; risk of explosion from gases

The Special Problem of Tires in Landfills

a. Tires are made of vulcanized rubber that cannot be melted or reused

C. Incineration - also called “energy recovery” or

“Waste-to-Energy” 1. Trash is burned, and the heat is used

to generate electricity 2. 1000 plants word-wide (110 in U.S.) 3. Types of Incinerators

Fig. 21.11, p. 536

Advantages

Reduced trashvolume

Less need forlandfills

Low waterpollution

Disadvantages

High cost

Air pollution(especiallytoxic dioxins)

Produces ahighly toxic ash

Encourageswaste production

Fig. 21.10, p. 536

Power plant

Steam

Turbine GeneratorElectricity

Crane

Furnace

Boiler

Wetscrubber

Electrostaticprecipitator

Conveyor

Water Bottomash

Conven-tional

landfillWaste

treatmentHazardous

Wastelandfill

Dirtywater

Waste pit

Smokestack

Flyash

a. Mass Burn 1) All trash burned 2) More air pollution: 10-20% of

original mass is ash: disposed of as toxic waste

3) In the US- there are few regulations, regulations are not enforced and workers are untrained.

b. Refuse-Derived 1) Trash is sorted before burning 2) Less air pollution, higher quality fuel

4. Problems Associated with Incineration A. Carbon Monoxide, particulates, heavy

metals and toxic chemicals released B. Expensive pollution control devices

must be installed; scrubbers, electrostatic precipitators

C. Electrostatic precipitators spray gases from incinerator giving them a positive charge and gases stick to negatively charged plates

D. Ash produced must be disposed of in hazardous landfills

D. Composting 1. Organic Wastes a. Grass clipping,

leaves and other organic wastes can be used as fertilizers

E. Ocean Dumping

1. 55,000,000 lbs of trash are dumped in the sea every year2. 300,000 lbs of fishing gear (causes 50,000 Northern Fur Seals to die every year)3. Ocean dumping prohibited in U.S. between 1988-1992Boats dump raw sewage overboard worldwide, and much of our solid waste ends up in the Ocean

F. Exporting Waste

1. Wastes get exported from developed to developing countries

a. Little control by receiving countries about what is in trash

2. 1994: ban on transporting toxic wastes

3. Also happens within countries - trash goes to poor neighborhoods (Native American reservations)

4. N.I.MB.Y. philosophy everywhere

WASTE PREVENTION (Reduce, Reuse & Recycle)

A. Integrated Waste Management1.Variety of methods to minimize waste (3 R’s= Reduce, Reuse, Recycle) 2. Saves money, decreases pollution control, reduces extraction of resources

.