PPT BY CLARK E. ADAMS

ENVIRONMENTAL SCIENCE: TOWARD A SUSTAINABLE

FUTURE RICHARD T. WRIGHT

Chapter 17

Water Pollution and Its Prevention

WATER POLLUTION AND ITS PREVENTION

• Water pollution• Eutrophication• Sewage management and treatment• Public policy

POLLUTION

• Pollution: “the presence of a substance in the environment that because of its chemical composition or quantity prevents the functioning of natural processes and produces undesirable environmental and health effects.”

WATER POLLUTION SOURCE

WATER POLLUTION TYPES

• Pathogens• Organic Wastes• Chemical• Sediments• Nutrients

PATHOGENS CARRIED BY SEWAGE

• Disease-causing agents (Table 17.1) • Safety measures

• Purification of public water supply• Sanitary collection/treatment of sewage• Sanitary practices when processing food

ORGANIC WASTES

• Usually from fertilizers or waste• Dissolved oxygen (DO) in the water is depleted

during decomposition of organic wastes.• Water quality test

• Biochemical oxygen demand (BOD): the amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic activity;

CHEMICAL POLLUTANTS

• Inorganic chemicals

• Heavy metals, acids, road salts• Organic chemicals

• Petroleum, pesticides, detergents

SEDIMENTS …EFFECTS ON STREAM ECOLOGY

• Loss of hiding/resting places for small fish

• Attached aquatic organisms scoured from the rocks and sand

• Poor light penetration

EUTROPHICATIONEUTROPHICATIONHARMFUL CHANGES IN WATER CAUSED BY TOO MUCH FERTILIZER OR

NUTRIENTS.

http://www.stumbleupon.com/su/2E5OIB/oceantoday.noaa.gov/happnowdeadzone/

1. Fertilizer flows into water causing….

2. Increased plant growth on the surface of water, causing…..3. Decreased light in lower levels of water, causing…

4. Plants in lower levels of water to die, causing….5. Decay using up O2 and increasing CO2,causing…...

6. Death of fish and other animals.

STEPS OFEUTROPHICATION

These fish died due to eutrophication removing the

oxygen.

THREE CAUSES OF THREE CAUSES OF EUTROPHICATION:EUTROPHICATION:

•Fertilizer or manure runoff from farmland.

•Improper disposal of sewage.

•Chemical and industrial waste.

Compare the water upstream from the dam to downstream, what differences do you

see?

Compare these 2 ponds, the bottom one experiencing

eutrophication.

Increased moss growth along this shoreline due to eutrophication

What role does eutrophication play on pond succession?

Eutrophication speeds up succession.

It speeds it up causing the pond to fill in faster.

EUTROPHICATION

• Different kinds of aquatic plants• The impact of nutrient enrichment

• Combating eutrophication

DIFFERENT KINDS OF AQUATIC PLANTS

•Benthic plants (water plants)• Emergent vegetation: emerges!• Submerged aquatic vegetation (SAV)• Phytoplankton

• Green filamentous and single cell• Blue-green single cell• Diatoms single cell

THE IMPACTS OF NUTRIENT ENRICHMENT

• Oligotrophic: nutrient-poor water• Eutrophic: nutrient-rich water

EUTROPHICATION

• As nutrients are added from pollution, an oligotrophic condition rapidly becomes eutrophic.

Oligotrophic

Eutrophic

EUTROPHIC OR OLIGOTROPHIC?

•High dissolved O2

•Deep light penetration•High phytoplankton

EUTROPHIC OR OLIGOTROPHIC?

• Turbid waters• High species diversity• Good recreational qualities• High detritus decomposition

• Low bacteria decomposition• Benthic plants• Warm water• High nutrient concentration• High sediments

NATURAL AND CULTURAL EUTROPHICATION

• Natural eutrophication• aquatic succession• occurs over several hundreds of years

• Cultural eutrophication• driven by human activities• occurs rapidly

COMBATING EUTROPHICATION

• A. Attack the symptoms• Chemical treatment• Aeration• Harvesting aquatic weeds• Drawing water down

COMBATING EUTROPHICATION

•B. Getting at root cause•Controlling point sources•Controlling nonpoint sources

CONTROLLING POINT SOURCES

• Ban phosphate detergents• Sewage-treatment improvements

CONTROLLING NONPOINT SOURCES

• Difficult to address runoff pollutants• Urban• Agricultural fields• Deforested woodlands• Overgrazed pastures

COLLECTING POND FOR DAIRY-BARN WASHINGS

SEWAGE MANAGEMENT AND TREATMENT

• Development of sewage collection and treatment systems

• The pollutants in raw sewage• Removing the pollutants from sewage• Treatment of sludge• Alternative treatment systems

DEVELOPMENT OF SEWAGE COLLECTION AND TREATMENT SYSTEMS

• Through the 1970s sewage was discharged directly into waterways

• Clean Water Act of 1972

• Storm drains for collecting runoff from precipitation

• Sanitary sewers to receive all the wastewater from sinks, tubs, and toilets

POLLUTANTS IN RAW SEWAGE

• 99.9% water to 0.1% waste• Pollutants in sewage are:

• Debris and grit• Particulate organic material• Colloidal and dissolved organic material• Dissolved inorganic material

TRICKLING FILTERS FOR SECONDARY TREATMENT

TRICKLING FILTERS FOR SECONDARY TREATMENT

BIOLOGICAL NUTRIENT REMOVAL

• Activated sludge: 3 zones

• Conversion of NH4 to NO3

• NO3 converted to N gas and released

• PO4 taken up by bacteria and released with excess sludge

SLUDGE TREATMENT

• Anaerobic digestion• Composting• Pasteurization

Treatment of Sludge

MethaneHumus

ALTERNATIVE TREATMENT SYSTEMS

• Individual septic systems• Wastewater effluent irrigation• Reconstructed wetland systems

• Beaumont, TX

• The waterless toilet

DEWATERING TREATED SLUDGE

SEPTIC TANK TREATMENT

• Aerobic digestion of solids in septic tank

• Flow of liquids into drain field for evaporation, infiltration, or irrigation