Chapter 21: Water Pollution

1. Chapter 21:Water Pollution

2. 21.1 Water Pollution • Water pollution: the degradation of water quality • A pollutant is any biological, physical, or chemical substance that is harmful to desirable living organisms • Water pollutants include… • heavy metals, sediment, certain radioactive isotopes, heat, fecal coliform bacteria, phosphorous, sodium, nitrogen, and pathogenic bacteria and viruses.

4. Major uses for water today: • Agriculture: Most vegetation can tolerate a wide range of water quality, allowing for agricultural water to vary in physical, chemical, and biological properties. • Industrial Processes: The quality of water needed for industrial purposes varies widely depending on what the process involves; some processes need distilled water, or water with a specific quality. • Domestic (Household) Supply: Water in a domestic supply must be free of any materials harmful to health or household plumbing and appliances i.e. Insecticides, pesticides, pathogens, etc.

5. 21.1 Water Pollution • Some pollutants may be a pollutant to one environment, but not to others • The primary problem with water pollution today is a lack of clean, disease-free drinking water • The U.S. treats drinking water before consumption, eliminating most waterborne diseases, but in many other parts of the world this is not the case. • Major uses for water today include agriculture, industrial processes, and domestic supply.

6. Domestic Water Use: How safe is it? • Water for domestic use is drawn from surface and groundwater • It is stored in reservoirs and ponds so solids and sediment settle increasing the clarity • All water must then be treated to meet national drinking water standards (see p424) • Next, the water is run through a water plant where it is filtered and chlorinated • Once it reaches people’s homes it is treated even further through charcoal filters in the tap • Many people do not like to drink tap water because it runs through metal pipes and contains chlorine, but the drinking water in the US is considered the safest in the world and the added chlorine is necessary because it eliminates waterborne disease • Although our drinking water may be the safest in the world, little is known of the long term effects of the minimal amounts of toxins that are contained in the water • These may be heavy metals and organic chemicals that require more research • These concerns have caused the bottled water industry to become a multi-billion dollar industry

7. 21.2 Biochemical Oxygen Demand (BOD) • When there is dead organic matter in a stream, bacteria breaks it down using oxygen from the water • If there is too much bacterial activity due to dead material, the oxygen supply will deplete and make a zone inadequate to sustain life for other organisms • Therefore, a stream with a low enough oxygen level is considered polluted • The Biochemical Oxygen Demand is the amount of oxygen required for the biochemical decomposition process • Scientists determine water quality by measuring the amount of oxygen consumed by microorganisms as they break down organic matter in small samples • This is commonly practiced at wastewater treatment plants • Dead organic matter comes from sources such as leaves falling off a tree, agricultural runoff, and runoff from urban sewage • An example of too much organic matter going into a body of water at once is a sewage treatment plant that overflows from storm runoff and runs off into streams untreated • This could cause the oxygen supply to become too low to support life in the water • This also causes three zones to form in the water • 1) pollution zone: High BOD • 2) Active decomposition zone: dissolved oxygen content reaches a minimum due to rapid decomposition • 3) recovery zone: dissolved oxygen increases and BOD is reduced

9. http://www.youtube.com/watch?v=4vFD6fCMDTA

10. Sources and Processes of Water Pollution: • An increasing population often results in increases pollutants in the environment. • The U.S. Environmental Protection Agency has set thresholds on water pollution levels for some pollutants. If the pollutant is present in a greater concentration that the threshold the water in unsuitable for use.

11. 21.9: Groundwater Pollution • Groundwater- water found beneath the Earth’s surface within the zone of saturation under the water table • Almost 50% of Americans’ drinking water comes from groundwater • This concerns environmentalists; groundwater can be easily polluted by hard-to-detect toxins • Only a small portion is known to be contaminated, but as groundwater contamination testing is becoming more commonplace, we’re finding higher proportions of contaminated groundwater

12. Causes of Groundwater Pollution • Increasing human population increases stress on groundwater supply • Runoff from precipitation • Road salts, oil, fertilizers, pesticides • Waste disposal sites in the US are producing chemical plumes that migrate into the groundwater • Approx. 75% of 150,000 sites suspected of this • http://www.youtube.com/watch?v=5xs1jLlbztE

13. 5 Principles of Groundwater Pollution • Some pollutants, like gasoline, are lighter than water; float on the groundwater • Some pollutants have 3 phases: liquid, vapor and dissolved. • Dissolved phases chemically combine with groundwater. Ex: salt dissolves in. • Some pollutants are heavier than water, and sink downward thru the groundwater • Particulates, cleaning solvents • Treatment must address physical and chemical properties of the pollutant • Ex: extraction well for gas because gas floats on water • Emphasis should be placed on prevention of pollution instead of clean up (cheaper, less environment damage)

14. Treatment Options • Bioremediation – A method of treating groundwater pollution problems that utilizes microorganisms in the ground to consume or break down pollutants • Vapor extraction system • A well pump extracts vapor from gasoline underground before it affects water in homes • Removal and disposal of soil (near contaminated areas) • Very expensive; big environmental consequences

16. Case Study: Long Island • Nassau county: groundwater pollution caused by saltwater infiltration and shallow aquifer contamination • Shallow-aquifer pollution associated with urbanization • Urban runoff, household sewage from cesspools and septic tanks, salt (for de-icing highways) and industrial and solid waste • Pumping of groundwater over the past 15 years has led to declining water levels • As groundwater is removed from coast, subsurface outflow to ocean decreases, allowing salt water to migrate inland

17. Saltwater Intrusion

18. 21.10 – Wastewater Treatment • When used for industrial or municipal purposes, water is often degraded • Wastewater Treatment – Process of treating wastewater (primarily sewage) in specially designed plants that accept municipal wastewater. Generally divided into three categories: Primary treatment, secondary treatment, and advanced waste-water treatment

19. 21.10 – Wastewater Treatment • Conventional Methods: • Septic tank disposal systems in rural areas • Centralized water treatment plans in cities • Recent innovative approaches: • Application of wastewater to the land • Wastewater renovation and reuse

20. 21.10 – Septic Tank Disposal Systems • In rural areas, there is no central sewage systems or wastewater treatment facilities available • Result: individual septic tanks • By law, an evaluation is needed for the site of a potential septic tank

22. 21.10 – Primary treatment • Incoming raw sewage enters the plant’s sewer line • Sewage then enters the grit chamber • Then enters the primary sedimentation tank • Sludge is removed and transported to the digester for further processing • Removes 30 to 40% of BOD

23. 21.10 – Secondary Treatment • Most common method of secondary treatment is activated sludge • Wastewater from primary sedimentation tank enters the aerotation tank • Waste water mixed with air • Enters the final sedimentation tank, sludge settles out • Treated by anaerobic bacteria • Discharged to a river, lake, or ocean • Removes about 90% of BOD

25. 21.10 - Advanced Wastewater Treatment • Primary and secondary treatment do not remove all pollutants from incoming sewage • Additional pollutants can be removed by adding more steps of treatment • The treated water is released into the surface water and can be used for irrigation or municipal properties • Advanced wastewater treatment is used when it is important to maintain good water quality

26. 21.10 – Chlorine Treatment • Chlorine is frequently used to disinfect water in the process of wastewater treatment • It’s very effective in killing the pathogens that have historically caused outbreaks of serious waterborne diseases • It has been recently discovered that chlorine treatment produces very small quantities of chemical byproducts • Some of these are potentially hazardous to humans and animals • How much of a risk these chemical byproducts are is a matter of debate and is rather controversial • However, evidence suggests that these byproducts create a risk of cancer and other possible side effects

27. 21.11 Land Application of Wastewater • Wastewater renovation and conservation cycle - First is returns treated water to crops via irrigation systems, then it naturally purifies water wastewater through percolation (renovation), and lastly it reuses the treated water.

28. 21.11 Land Application of Wastewater • Resource recovery wastewater treatment plant- Both environmentally preferred and economically viable. It uses methane gas as fuel. • How it Functions- First wastewater is run through filters, then it is put through anaerobic processing, and finally the nutrient rich water is run over an incline and onto plants.

29. 21.11 Land Application of Wastewater • Wastewater and wetlands • Treating wastewater through wetland systems is attractive to communities that find it difficult to purchase wastewater treatment plants. • Louisiana applies nitrogen and phosphorus rich wastewater to wetlands and increases plant production/ improves water quality. • Arizona constructed artificial wetlands that contain bacteria that reduce Nitrate concentration in the wtaer.

30. 21.12- Water Reuse • Water reuse can be inadvertent, indirect, or direct • Inadvertent- water is withdrawn, treated, used, treated, and returned to the environment, followed by further withdrawals and use • Millions depend on it who live near large rivers • Risks- poor treatment= poor water quality • Diseases or viruses may develop before or after treatment, making potential health risks • New diseases may form

31. Indirect water reuse • Planned water usage • US used several thousand cubic meters of treated wastewater per day to be applied to surface recharge areas • Treated water enters ground water storage to be reused for agricultural and municipal purposes

32. Direct water reuse • Treated water is pumped directly from a treatment plant to the next user • Used in agriculture, industry, irrigating golf courses, on institutional grounds, and parks • Growing rapidly • Las Vegas hotels use water from rivers, fountains, canals, and lakes (required to treat and reuse waste water) • Little direct use of water is used for human consumption (except in emergencies) because of risks and negative cultural attitudes toward using treated water

33. 21.13 Water Pollution and Environmental Law • Environmental Law- branch or law dealing with conservation and use of natural resources and control of pollution • In the US, laws at the federal, state, and local levels address these issues • First federal law to protect water resources- Refuse Act of 1899 = protected navigable streams, rivers, and lakes from pollution • Many federal laws have been passed to clean up or treating pollution problems or treating wastewater. • Also, there has been a focus on preventing pollutants from entering water • Prevention has the advantage of avoiding environmental damage and costly cleanup/treatment

35. Water Laws • 1990’s was a time of debate in the US over water pollution. • US tried to rewrite the Clean Water Act in 1994 to give industry more flexibility to comply with environmental regulations with water pollution • Gov. saw this as a way to save money without causing environmental degradation • Environmentalists saw it as a step backwards to cleaning up water resources. • Congress was wrong; people are willing to pay more for clean water • Unfortunately, congress continues to debate and little has been resolved

36. Water Laws • In 2000, the US president aimed to protect thousands of streams and lakes from nonpoint agricultural, industrial, and urban pollution sources. • This will be enforced by the Environmental Protection Agency, which will work with local communities and states to develop plans to reduce pollution in streams, lakes, and estuaries • Problems- It is difficult to regulate, it will take 15 years to implement completely, and it has been opposed by Congress, agricultural groups, the utility industry, and the US Chamber of Commerce. • Main objections- it is costly (billions of dollars) and that local and state gov’ts are better suited to control their own water pollution regulations • The god news is that these regulations mark a new phase in water pollution control in the US