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” • During Middle Ages conditions deteriorated • Sand filters became common in 1700s in France • Chlorination was introduced in 1909 in NJ.
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.
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
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 • 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 11.6Raw 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.
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
NAPL: Non-Aqueous Phase Liquids DNAPL: Dense NAPL (dry cleaners, industrial) LNAPL: Light NAPL (gasoline, diesel)
Arsenic Poisoning http://www.angelfire.com/ak/medinet/arsenic.html
New York Sand Hogs • http://www.youtube.com/watch?v=5gfSEjMtAoc
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
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.