Transcript Figure 1.1 Centers of early civilizations – Water was a

Chapter 11: Drinking Water and
Wastewater Treatment
• Drinking Water
– Historical Perspective
– Federal Protection of Drinking Water
– Treatment Process
• Wastewater
– Historical Perspective
– Treatment Process
Drinking Water:
Historical Perspective
• The Greeks and Romans recognized that
poor water quality caused disease and death
• Bathing once or twice a year was “healthy”
• Sand filters became common in 1700s
• Urban water was poorer than water from
forested watersheds
• Chlorination was introduced in 1907.
Potable Water
• Water used for drinking, cooking, and
washing
• Requires filtering, disinfection, desalinization
• Groundwater has natural filtration, may need
disinfection
• New York City does not filter suface water
because it is from forested areas.
• Reverse osmosis is needed to remove salts.
Calcutta, India, during rainy season
London Water Works (Thames River)
China
Water Quality Concerns
• Pathogens
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Bacteria (E. coli, fecal strep, cholera)
Viruses (polio, hepatitus)
Protozoa (Giardia)
Dysentary (Amoeba and Shigella)
• Emerging Contaminants
– Endocrine disruptors (contraceptives)
– Antibiotic resistant pathogens, pharmaceuticals
– Metals (lead, arsenic), Organics (gasoline, herbicides)
Federal Protection
• 1914: U.S. Treasury established a limit of 2
coliforms per 100 mL for drinking water
• 1942: U.S. Public Health Service standardized
drinking water standards
• 1948: Federal Pollution Control Act
• 1974: Safe Drinking Water Act
• 1986: Wellhead Protection Program
• 1996: Source Water Assessment and Protection
Figure 11.4 This intake structure for the Mount Werner Water Filtration Plant
is located near the mouth of Fish Creek Canyon above Steamboat Springs,
Colorado.
Drinking Water Standards, 2004
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Copper (liver and kidney damage) 1.3 mg/L
Fluoride (bone disease) 4.0 mg/L
Nitrate (Blue Baby syndrome) 10 mg/L
Nitrite (same) 1 mg/L
Dioxin (cancer) No detectible
Xylenes (nervous system damage) 10 mg/L
Atrazine (Cardiovascular damage) 0.003 mg/L
Figure 11.6 Raw water from the Mississippi River is pumped to the
Carrollton Water Purification Plant, one of two such plants that serve the city of
New Orleans.
Drinking Water Treatment
• Watershed and wellhead protection: prevents
contamination
• Diversion, storage, and intake
• Flocculation/coagulation => settling
• Filtration
• Fluoridation
• Disinfection: Cl2, O3, UV, chloramines
• Distribution: storage and pressure
Figure 11.7 The water tower at Clarkson, Nebraska, is located on a hill in
the farming community of 700 residents in eastern Nebraska.
Figure 11.5 Water intake clogged with Zebra Mussels.
Flouride and Tooth Decay
Flouride is added to strengthen
teeth and bones
Many communities add F to
improve teeth
Dentists can tell whether you grew
up on city water or not
Adding too much causes brittle
bones
Lead in Drinking Water
Sources: lead solder and pipes
Problem: behavior problems
and learning disabilities
Drinking Water from Wells
• City wells are routinely tested
• Private water wells are seldom tested
• Sources of contamination include
wastewater, landfills, junkyards
Leaking Underground Storage Tanks
NAPL: Non-Aqueous Phase Liquids
DNAPL: Dense NAPL (dry cleaners, industrial)
LNAPL: Light NAPL (gasoline, diesel)
Wellhead Protection
Arsenic Poisoning
http://www.angelfire.com/ak/medinet/arsenic.html
Wastewater:
Historical Perspective
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A major problem since the earliest cities
Most went down roads to the nearest stream
1370: First underground sewers
1867: First wastewater treatment (London)
1928: First U.S. operation (Fessenden, ND)
1964: First Athens treatment plant
Figure 11.8 The Fessenden, North Dakota, sewage lagoon is famous in the
realm of wastewater treatment around the world.
Wastewater Treatment Process
• Primary Treatment: Remove large debris
(sand, stones, garbage)
• Secondary Treatment: Break down organic
matter by adding oxygen to promote decay
– Tricking filter: Water cascades down over
coarse materials (stones, balls)
– Activated sludge: Large motors churn air into
the water
• Tertiary Treatment: Nutrient Removal
Figure 11.9 The wastewater treatment process at larger facilities includes
numerous steps such as bar screen, grit removal, primary and secondary
settling tanks, aeration, flocculation and coagulation, sand filters, and
chlorination.
Septic Tanks and Leach Fields
• Septic tank collects biosolids and breaks
them down. Aerobic decay requires oxygen,
anaeorobic decay does not. Facultative
decay is when both are present.
• Leach field takes water that has gone
through the septic tank, and is allowed to
percolate through the soil
Wetlands and Water Treatment
• Similar to the original Fessenden plan.
• Natural biodegradation and nutrient removal.
• Good environment (mixed aerobic and
anaerobic) for facultative bacteria.
• Provides habitat, increases water storage and
prevents overflows during wet weather.
CSOs
• Combined Sewer Overflows
• Used to carry sewage to treatment plant during
dry weather
• Also collects stormwater during wet weather
• System is overloaded during big storms, and is
routed directly to the river
NPDES Permit
• National Pollution Discharge Elimination
System
• Used to regulate wastewater discharges
• Requires a minimum treatment standard
– Dissolved Oxygen, pH, BOD, ammonia,
toxicity
• These permits get more strict over time as
more users need to add to the river
Chapter 11: Quiz
1. Describe how large particles are removed
during drinking water treatment.
2. Adding ____________ to drinking water
helps to prevent cavities.
3. Name one process for disinfection:
4. Name and describe the three steps in
wastewater treatment:
a.
b.
c.