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
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
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
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
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.
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.
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
Example of high BOD from an accidental spill 3 zones: pollution zone, active decomposition zone, recovery zone
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.
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.
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)
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
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.
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
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
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.
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.
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.
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.
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.
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
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
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
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.
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.
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.
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 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
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