Part 6: Water Pollution Point source pollution - source is from drain pipes, ditches, sewer outfalls, factories and power plants - easy to monitor and regulate Nonpoint source pollution - runoff from farm fields and feedlots, lawns and gardens, golf courses, construction sites, atmospheric deposits - no specific location so harder to monitor and regulate
Types and Results of Water Pollution Infectious agents - 25 million deaths a year Organic materials - biological oxygen demand (BOD) increase resulting in oxygen sag Plant nutrients - eutrophication, toxic tides Metals - mercury and lead poisoning Nonmetallic salts - poison seeps and springs Acids and bases - ecosystem destabilization Organic chemicals - birth defects, cancer Sediments - clogged estuaries, death of coral reefs Thermal pollution - thermal plume
Infectious Agents Main source of waterborne pathogens is untreated or improperly treated human waste. –Animal wastes from feedlots and fields is also an important source of pathogens. –In developed countries, sewage treatment plants and pollution-control devices have greatly reduced pathogens. –Tests for water quality are done for coliform bacteria (intestinal bacteria). Such tests are easy and cheap. Escherichia coli (E. coli) is the major coliform bacterium species
Environmental Implications of Oxygen-Demanding Wastes Oxygen – the life-giving gas –added to water by diffusion from wind and waves, and by photosynthesis from green plants, algae, and cyanobacteria. –removed from water by respiration and oxygen-consuming processes. Water with a Dissolved Oxygen Content (DOC) content > 6 parts per million (ppm) supports desirable aquatic life Water with < 2 ppm oxygen supports mainly detritivores and decomposers.
Biochemical Oxygen Demand (BOD) - the amount of dissolved oxygen consumed by aquatic microorganisms in respiration. When organic wastes are added to rivers, microorganisms use more oxygen in consuming the increased food resource. –Thus, DOC levels decline downstream (oxygen sag) from a pollution source as decomposers metabolize organic waste materials.
Plant Nutrients and Cultural Eutrophication Oligotrophic - Bodies of water that have clear water and low biological productivity. Eutrophic - Bodies of water that are rich in organisms and organic material. –Eutrophication - Process of increasing nutrient levels and biological productivity. Cultural Eutrophication - Increase in biological productivity (plants & algae) and ecosystem succession caused by human activities (excess fertilizer).
Inorganic Pollutants Metals –Many metals such as mercury, lead, cadmium, and nickel are highly toxic. Highly persistent and tend to bioaccumulate in food chains. –Lead pipes are a serious source of drinking water pollution. Mine drainage and leaching are serious sources of environmental contamination. Nonmetallic Salts –Many salts that are non-toxic at low concentrations can be mobilized by irrigation and concentrated by evaporation, reaching levels toxic to plants and animals (selenium & arsenic). –Leaching of road salts has had detrimental effect on many ecosystems. Acids and Bases –Often released as by-products of industrial processes.
Organic Chemicals Thousands of natural and synthetic organic chemicals are used to make pesticides, plastics, pharmaceuticals, pigments, etc. Two most important sources of toxic organic chemicals in water are: –Improper disposal of industrial and household wastes –Runoff of pesticides from high-use areas Fields, roadsides, golf courses Some dissolve out of the products we use
Sediment Human activities have accelerated erosion rates in many areas. –Cropland erosion contributes about 25 billion metric tons of suspended solids to world surfaces each year. Sediment can either be beneficial (nourish floodplains) or harmful (smother aquatic life).
Sediment & industrial waste flowing into Lake Erie
Thermal Pollution Raising or lowering water temperatures from normal levels can adversely affect water quality and aquatic life. –Oxygen solubility in water decreases as temperatures increase. Species requiring high oxygen levels are adversely affected by warming water. –Higher temperatures affect coral growth Industrial cooling systems often use heat-exchangers to extract excess heat, discharging heated water back into original source. –Thermal Plume Produce artificial environments which attract many forms of wildlife. May also adversely affect local life
Part 7: Water Quality Today
Groundwater and Drinking water Pollution About half the US population, and 95% of rural residents, depend on underground aquifers for drinking water. –For decades, groundwater was assumed impervious to pollution. –Soils/rocks above aquifers would somehow take care of any pollutants (years ago, just wastes) The Earth’s a big place, right?
Some sources of groundwater pollution
Underground storage tanks – an example That’s where the gasoline is stored at your local gas station Over time, they (and the pipes going to the pumps) leak The gasoline seeps downward into shallow aquifers –Benzene, toluene, xylenes, methyl tertiary butyl ether (MTBE) –Benzene & MTBE known carcinogens –Benzene can degrade somewhat quickly; MTBE is more stubborn
Progress and Problems in Other Countries Sewage treatment in wealthier countries of Europe generally equal or surpass the US. In Russia, only about half of the tap water supply is safe to drink. In urban areas of South America, Africa, and Asia, 95% of all sewage is discharged untreated into rivers. Two-thirds of India's surface waters are contaminated sufficiently to be considered dangerous to human health.
Part 8: Pollution Control Nonpoint Pollution Sources and Land Management –Reduce nutrient loading thru land use regulations –Source reduction is cheapest and most effective way to reduce pollution. To work society must get public and business leaders to avoid producing or releasing substances into the environment. Studies show as much as 90% less road salt can be used without significantly affecting winter road safety. Soil Conservation Banning phosphate detergents Sewage Treatment Remediation
Sewage Treatment Rationale –More than 500 pathogenic bacteria, viruses, and parasites can travel from human or animal excrement through water. Natural Processes –In many areas, outdoor urination and defecation is the norm (do bears do something in the woods?). When population densities are low, natural processes can quickly eliminate waste. Artificial Wetlands Are a Low Cost Method –Natural water purification Effluent can be used to irrigate crops or raise fish for human consumption.
Municipal Sewage Treatment Primary Treatment - Physical separation of large solids from the waste stream. Secondary Treatment - Biological degradation of dissolved organic compounds. –Effluent from primary treatment transferred into trickling bed, or aeration tank Effluent from secondary treatment is usually disinfected (chlorinated) before release into nearby waterway. Tertiary Treatment - Removal of plant nutrients (nitrates and phosphates) from secondary effluent. –Chemicals, or natural/constructed wetlands. In many US cities, sanitary sewers are connected to storm sewers (ummmmm… maybe, Atlanta???). –Heavy storms can overload the system, causing by-pass dumping of raw sewage and toxic runoff directly into watercourses.
Sewage Treatment Typical organic compounds in released wastewater. Concentrations in micrograms per liter. (numbers as of 2002)
Water Remediation Containment methods confine liquid wastes in place, or cap surface with impermeable layer to divert water away from the site. Extraction techniques are used to pump out polluted water for treatment. –Oxidation, reduction, neutralization, or precipitation. Living organisms can also be used effectively to break down polluted waters.
Clean Water Act (1972) –Established uniform, nationwide controls –Goal was to return all U.S. surface waters to "fishable and swimmable" conditions. For point sources, discharge permits and “best practicable control technologies” are required. –Set zero discharge requirement for 126 priority toxic pollutants. –Amended in 1985 Part 9: WATER LEGISLATION
Other important legislation Safe Drinking Water Act (1974) –Minimum safety standards for all community water supplies Resource Conservation & Recovery Act (RCRA) (1976) –Regulates storage, shipping, processing & disposal of hazardous wastes Toxic Substances Control Act (TOSCA) (1976) –Categorizes toxic & hazardous substances –Regulates use & disposal of poisonous chemicals
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA; “Superfund”) (1980) and Superfund Amendments & Reauthorization Act (SARA) (1984) –Sealing, excavation, or remediation of toxic & hazardous waste dumps –Funded mainly by a tax on petroleum & chemical companies in the past (you know who payed that?......)
Emergency Planning & Community Right-to- Know Act (1986) –Part of SARA –Not really water-related –Has to do with chemicals present in the workplace –For any chemicals used by a company, a Material Safety Data Sheet (MSDS)must be readily available Gives the product’s makeup, it’s properties, hazards, and lots of other fun stuff Technically, an MSDS is also needed for water in the water cooler