Chapter 21 Water Pollution & Treatment

1. Chapter 21Water Pollution & Treatment Emily Miglis, Melissa Castrogiovanni, Jackie Innella

2. 21.1 Water Pollution • Degradation of water quality • Pollutants include heavy metals, sediment, certain radioactive isotopes, heat, fecal coli-form bacteria, phosphorus, nitrogen, sodium, certain pathogenic bacteria and viruses

3. 21.1 (cont.) Primary problem: lack of clean, disease-free drinking water • United States • Epidemics of waterborne diseases have killed thousands of people in the past • Now water is treated prior to consumption (less disease) • Worldwide • Every year, several billion people are exposed to water borne diseases

4. 21.1 (cont.) Major uses for water: domestic, industrial, agriculture • Domestic Supply • Cannot be harmful to health, taste good, odorless, should not damage plumbing/household appliances • Industrial Purposes • May require distilled water • May require noncorrosive water or water free of particles that could damage equipment • Agriculture • Vegetation tolerates wide range or water quality • Can vary widely in physical, chemical, and biological, properties

6. 21.1 (cont.) • Increasing population leads to introduction of more pollutants into the environment • Over ¼ of US drinking water systems reported a violation of federal health standards • US Environmental Protection Agency has set limits on water pollution levels for some pollutants • Pollutant maximum concentration standards have been set for only some of the more then 700 possible water contaminants

7. 21.2 Biochemical Oxygen Demand • Bacteria decays dead organic matter in streams • Bacteria uses oxygen • A lot of bacterial activity decreases oxygen levels in water • A stream with low oxygen content is a poor environment for fish and most other organisms and is considered polluted.

8. 21.2 (cont.) • The amount of oxygen required for biochemical decomposition processes is called the biochemical oxygen demand (BOD). • Measures the amount of oxygen consumed by microorganisms as they break down organic matter • Approximately 33% of all BOD in streams results from agricultural activities.

9. 21.2 (cont.) • When the BOD is high, the dissolved oxygen content of the water may become too low to support the life in the water. • US Environmental Protection Agency • Water pollution alert is when the dissolved oxygen content is less than 5mg/liter of water

10. 21.2 (cont.) • Example of high BOD from an accidental spill • 3 zones: pollution zone, active decomposition zone, recovery zone

11. 21.2 (cont.) • All streams have some capability to degrade organic waste. • Problems occur when the stream is overloaded with biochemical oxygen-demanding waste. • This overpowers the stream’s natural cleansing function.

12. 21. 9 Groundwater Pollution • About half of US people depend on groundwater • Can be easily polluted • Difficult to recognize pollutants • 75% of the 175,000 known waste disposal sites in the US may be producing plumes of hazardous chemicals that are migrating into groundwater resources.

13. 21.9 (cont.) Principles of Groundwater Pollution: An Example • Leaking buried gasoline tanks caused much pollution • Underground tanks now strictly regulated • Many thousands have been removed • Vapor extraction: removal and disposal of soil and treatment of water (expensive) • Bioremediation: microorganisms consume gasoline (much less expensive)

14. 21.9 (cont.) Leaking buried gasoline tanks led to important points about groundwater pollution: • Some pollutants are lighter then water (float on groundwater) • Some pollutants have multiple phases: liquid, vapor, and dissolved • Some pollutants are heavy than water (sink through groundwater) • Water treatment depends on physical and chemical properties of pollutant • Prevent pollutants from entering groundwater in the first place

15. 21.9 (cont.) • Groundwater pollution differs from surface water pollution. • Groundwater kills aerobic types of microorganisms and is home for anaerobic varieties. • Groundwater channels are small and variable, therefore dispersion and dilution of pollutants is limited.

16. 21.9 (cont.) Long Island, New York • Nassau County and Suffolk County (population of several million people) depend entirely on groundwater • Two major problems: intrusion of salt water and shallow-aquifer contamination

17. 21.9 (cont.) • Saltwater intrusion • Salty groundwater cannot migrate inland due to the large wedge of fresh water moving beneath the island • Intensive pumping has caused water levels to decline as much as 50 feet in some areas • Shallow-aquifer pollution • Associated with urbanization • Pollutants enter surface waters and then migrate downward • Sources of pollution: urban runoff, household sewage, salt, industrial waste, and solid waste

18. 21.10 Wastewater Treatment • Wastewater treatment, or sewage treatment costs over $15 billion per year in the United States and the cost continues to increase. • Conventional methods of wastewater treatment include septic tank disposal systems in rural areas and centralized wastewater treatment plants in cities.

19. 21.10 continued… • Septic Tank Disposal Systems • No central sewage systems or wastewater treatment facilities are available in many rural areas. • Basic parts of a septic-tank disposal system • Sewer line from the house leads to an underground septic tank in yard. • Tank is designed to separate solids from liquid, digest, and store organic matter through a period of detention, and allow the clarified liquid to discharge into the drain field from a system of piping through which the treated sewage seeps into the surrounding soil. • It’s then treated by the natural processes of oxidation and filtering.

20. Septic Tank Disposal System

21. 21.10 continued… • Wastewater treatment methods are usually divided into 3 categories: • Primary Treatment – Removal of large particles and organic materials from wastewater through screening. Removes 30% to 40% of the BOD by volume from the wastewater. • Secondary Treatment – Use of biological processes to degrade wastewater in a treatment facility. The most common treatment is know as activated sludge. • Advanced Water Treatment – Some additional pollutants can be removed by adding more steps of treatment. Advanced Water Treatment is used when it’s particularly important to maintain good water quality.

22. 21.10 continued… • Chlorine Treatment • Frequently used to disinfect water as part of wastewater treatment. • Chlorine Treatment is very effective in killing the pathogens that historically caused outbreaks of serious waterborne diseases. • Recently discovered potential is that chlorine treatment produces minute quantities of chemical byproducts, some of which have been identified as potentially hazardous to humans and other animals. • The degree of risks is controversial and is currently being debated.

23. 21.11 The Wastewater Renovation and Conservation Cycle • Wastewater renovation and conservation cycle: Practice of applying wastewater to the land. • Steps: • 1. Return of treated wastewater to crops by irrigation system • 2. Natural purification (renovation) by slow leaking of the wastewater into the soil to eventually recharge the groundwater resource with clean water • 3. Treated water reused and pumped out of ground for municipal, industrial, institutional and agricultural purposes • Sewage is transported by sewers to treatment plant. Wastewater is chlorinated and pumped into a network that transports effluent to a series of spray irrigation rigs. Wastewater trickles down through soil and collected into a network of tile drains. Indirect advanced treatment uses natural, physical, and biological environment as filter.

24. Resource recovery: the production of resources, including methane gas as well as ornamental plants and flowers that have commercial value. • Steps • 1. Wastewater run through filters that remove large objects • 2. Water undergoes anaerobic processing (produces methane gas) • 3. Nutrient-rich water flows over an incline surface with plants • Plants use nutrients and purify water • Experimental technique • Problems: • Huge investment in traditional wastewater treatments • Economic incentives to provide for new technologies are not sufficient • There are not sufficient amounts of people trained to design and operate new types of wastewater treatment plants

25. Wastewater and Wetlands • Wetlands are very effective in treating water quality problems • Municipal wastewater from primary or secondary treatment plants (pathogens, phosphorus, nitrate, suspended solids, metals) • Stormwater runoff (metals, nitrate, pesticides, oils) • Industrial wastewater (metals, acids, oils, solvents) • Agricultural wastewater and runoff (nitrate, pesticides, suspended solids) • Mining waters (metals, acidic water, sulfates) • Groundwater seeping from landfills (metals, oils, pesticides) • Wetland systems a lot less expensive • Over 25 year period, $40,000 savings is expected • Louisiana: coastal wetlands • Wastewater filled with nitrogen and phosphorus • When put into wetlands, increases production of wetland plants, which in return improves water quality • When plants die their organic material partially lets wetland loose, causing wetlands to grow vertically • Wetlands becoming more and more popular as water quality standards are tightened, and cost is very important

26. Phoenix, Arizona: Constructed wetlands • Wetlands can be created in arid regions as well • Wetland treatment for agricultural waste is sited in residential community • 4.5 million gallons per day • Incoming water has lots of nitrate • 20 mg/l • Naturally occurring bacteria reduce nitrate to below maximum contaminant level • 10 mg/l • Water flows by pipe to recharge basin • Seeps into ground for groundwater resource

27. 21.12 Water Reuse • Water reuse can be inadvertent, indirect, or direct. • Inadvertent water reuse results when water is withdrawn, treated, used, treated, and returned to the environment, followed by further withdrawals and use. • Very common • Fact of life for millions of people who live along large rivers.

28. 21.12 continued… • Several risks are associated with inadvertent reuse: • Inadequate treatment facilities may deliver contaminated or poor quality water to downstream users. • Because the fate of all disease causing viruses during and after treatment is not completely known, the environmental health hazards of treated water remain uncertain. • New potentially hazardous chemicals are introduced into the environment every year. Harmful chemicals are often difficult to detect in the water.

29. 21.12 continued… • Indirect water reuse • Planned endeavor • Treated water eventually enters groundwater storage to be reused for agricultural and municipal purposes. • Direct water reuse • Refers to the use of treated wastewater that is piped directly from a treatment plant to the next user. • Used in industry in most cases. • Very little direct reuse of water is planned for human consumption due to perceived risks and negative cultural attitudes toward using treated wastewater.

30. 21.13 Water Pollution and Environmental Law • Environmental law: the branch of law dealing with conservation and use of natural resources and control of pollution • Done on federal, state, and local levels • Mid 1990s, water pollution big controversy • 1994- congress attempted to rewrite major environmental laws • Clean water act of 1977 • Congress wanted to give industry greater felxibilty in choosing how to comply with environmental regulations • Industry interestes preferred proposed new regulations because more cost effective • Environmentalists viewed this as a giant step backward in trying to clean up the earth • Publics views were incorrectly read, most cared more about money • Congress saw strong support for clean environement and thought people will pay for clean air and water

31. Failed regulation • July 2000, president imposed new water pollution regulations • Purpose was to protect rivers and lakes from nonpoint sources to agricultural, industrial, and urban population sources. • EPA would work with local communities and states to develop detailed plans to reduce pollution. • Plan would take 15 years to implement • Been opposed for years by Congress, agricultural groups, utility industry, and U.S. Chamber of Commerce • Requirements would be costly, spending billions • Local and state governments better suited to implement own water pollution regulations