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 – 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

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

• 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

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

• BOD - biochemical oxygen demand; biological oxygen demand

• Distribution: storage and pressure

The water 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.

BOD• The amount of oxygen used by microorganisms in the

process of breaking down organic matter in water. • The more organic matter there is (e.g., in sewage), the

greater the number of microbes. The more microbes there are, the greater the need of oxygen to support them; consequently, less oxygen is available for higher animals such as fishes.

• The BOD is therefore a reliable gauge of the organic pollution of a body of water.

• One of the main reasons for treating sewage or waste water prior to its return to a water resource is to lower its BOD-i.e., reduce its need of oxygen and thereby lessen its demand from the streams or rivers into which it is released.

The water tower at Clarkson, Nebraska, is located on a hill in the farming community of 700 residents in eastern Nebraska.

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

• 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

Wastewater DisposalWastewater leaves homes thru property laterals and enters City Sewer System. Sewers increase in size as Collection System moves wastewater into Interceptor Lines.

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

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.

First U.S. operation: The Fessenden, North Dakota, sewage lagoon is famous in the realm of wastewater treatment around the world.

Septic Tanks and Leach Fields

• Septic tank collects biosolids and breaks them down. Aerobic decay requires oxygen, anaerobic 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 13: Quiz1. 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.