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Chapter 20 WATER & SOIL POLLUTION
Water pollution Water Pollution: any physical or chemical change in water that adversely affects the health of humans and other organisms. There are 8 categories 1. 2. 3. 4. 5. 6. 7. 8. Sewage Disease causing agents Sediment pollution Inorganic plant and algal nutrients Organic compounds Inorganic chemicals Radioactive substances Thermal pollution
1. Sewage is the release of waste water from drains or sewers and includes human waste, soaps and detergents. Disease causing agents present Enrichment: Fertilization of a body of water by presence of high level of nutrients such as nitrogen & phosphorous Sewage can be decomposed into CO 2, water and materials by microorganisms Process of cellular respiration (oxygen is required)
Sewage cont… Oxygen has a limited ability to dissolve in water and when sewage is present, the microorganisms that break it down use up most of it BIOCHEMICAL OXYGEN DEMAND (BOD) The amount of oxygen needed by micoorganisms to decompose the waste into CO 2, water, and minerals Expressed as milligrams of dissolved O 2 per liter of water (mg O 2/L) Large amounts of sewage high BOD Robs the water of dissolved O 2 Anerobic miroorganisms produce unpleasant odor. . bottom line…. High BOD =Poor water quality
2. Disease- Causing Agents Infectious organism that cause disease. They come from the wastes of infected individuals. Bacteria Diseases: Typhoid Viruses Cholera Protozoa Dysentery Parasitic Worms Polio Hepatitis
Monitoring Water sources are constantly monitored for contamination E. choli is used as it is an indication of the amount of sewage present Fecal Coliform Test • Water is filtered and the filter is put in a petri dish and incubated. • Safe water should have no more that one coliform bacteria per 100 m. L • Most strains of coliform bacteria do not cause disease, but coliform test is a reliable indication of the presence of pathogens or disease causing agents in the water
3. Sediment Pollution SEDIMENT POLLUTION: Excessive amounts of suspended soil particles that settle out and accumulate on the bottom of a body of water due to decrease in water velocity. Causes: Erosion of agricultural lands, forest soils exposed by logging, degraded stream banks, overgrazed rangelands, strip mines, construction Problems: Reduces light penetration, bring pollutants into the water, reservoir filling, channel changing (shipping) Solution: Control of soil erosion
4. Inorganic Plant & Algal Nutrients Chemicals such as Nitrogen & Phosphorus that stimulate the growth of plants and algae. Necessary in small amounts, but overload is dangerous Sources: Human & animal wastes, plant residues, atmospheric deposition, fertilizer runoff from agricultural and residential areas Problem: Excessive growth of algae and aquatic plants disrupting the natural balance between producers and consumers. Also causes enrichment, bad odors, and high BOD from excessive numbers of algae dying and decomposition.
5. Organic Compounds Chemicals that contain carbon atoms (mostly synthetic) What are they? pesticides, solvents, plastics, industrial chemicals Where do they come from? DDT Acetone Seeping landfills, leaching, runoff, dumping How do we control organic compounds? Stewardship of our water sources, use of alternative organic compounds, and tertiary water treatment. Propane
6. Inorganic Chemicals Contaminants that contain elements other than carbon: Acids, Salts, Heavy Metals 1. Lead Sources: Paint, gas, incinerator ash dumped in ordinary landfills, air pollution from factories, pesticides & fertilizer residue on produce, food cans, serving plates & old pipes. Medical Problems: Lead poisoning, hypertension, miscarriages, stillbirths, mental & physical impairments, hearing loss, ADD, lowered IQ, learning disabilities.
2. Mercury § Vaporizes at room temperature DANGEROUS! § Once mercury settles into sediment, it is converted by bacteria to methyl mercury compounds which are more toxic. - Mercury accumulates in the muscles of tuna, swordfish, sharks - Methyl mercury compounds remain in the environment for a long time and are highly toxic to organisms Sources: Coal burning power plants (33%), municipal waste incinerators (18%), Medical waste incinerators (10%), smelting metals (lead, copper, zinc), industrial waste water, household trash (batteries, paints, plastics) Medical Problems: mental retardation, cerebral palsy, developmental delays in children. Kidney disorders, damage to the nervous and cardiovascular systems, headaches, depression
7. Radioactive Substances Contain atoms of unstable isotopes that emit radiation Sources: Mining & processing radioactive minerals, nuclear plants, industries, medical & scientific facilities. Indian Point Ground Water Contaminant Flows (nuclear facility in NY)
8. Thermal Pollution Heated water produced during certain industrial processes is released into waterways Produces chemical & biological effects Chemical: decomposition of waste occurs faster depleting water of oxygen. Less oxygen dissolves in warm water Biological: less oxygen dissolved less animals or animal stress, reproductive, digestion rates & respiration rates are affected http: //www. crocodile-clips. com/absorb/AC 4/sample/LR 1105_mg. html Turkey Point Nuclear Power plant Thermal Pollution
How do NUTRIENTS affect water systems? Oligotrophic Lake Eutrophic lake Slow flowing streams with Enrichment of water nutrients minimal nutrients Clear water Supports small populations causing algal blooms High BOD Fish populations (pike, sturgeon, whitefish cold ) (catfish, carp use less O 2)
Types of Pollution Point Source: Pollution is discharged into the environment through pipes, sewers or ditches from specific sites Non-Point Source: Pollution caused by land pollutants that enter bodies of water over large areas rather than at a single point. Agricultural runoff, mining wastes, municipal wastes, construction sediments
Sources of Water Pollution 1. Agriculture 2. Municipal: Contains salts, asbestos, chlorides, copper, cyanides, grease, lead, zinc, hydrocarbons, motor oil, organic wastes, phosphates, sulfuric acid Combined Sewer System: Human and industrial wastes are mixed with urban runoff or snowmelts that overpower the treatment plant & raw sewage flows into waterways without being treated 3. Industrial - High BOD, toxic compounds, sludge - Some industries are cleaning water before they discharge it
Improving Water Quality Purification of Drinking Water § Water supplies include streams, rivers, lakes, and reservoirs (dams) 1. Water is treated with aluminum sulfate causing suspended particles to come out 2. Water is then filtered through sand 3. Some cities pump water through activated carbon granules to remove organic cmpds. 4. Addition of chlorine to kill disease- causing agents. Some cities use UV instead of Cl. 5. Fluoridation – adding fluoride to municipal water sources to prevent tooth decay.
Municipal Sewage Treatment Waste water undergoes several treatments at a sewage treatment plant to prevent environmental and public health problems. The treated water is then discharged into rivers, lakes or the ocean.
Process: Primary Treatment 1. A. B. Removes suspended & floating particles Screening & gravitational settling 1. Solid material that settles out is known as primary sludge 2. Does not eliminate the inorganic & organic compounds remaining in the wastewater.
2. Secondary Treatment A. Uses microorganisms to decompose the suspended organic material 1. Trickling filters: wastewater trickles through rock beds containing bacterial which degrade the organic material 2. Activated sludge process: Wastewater is aerated and circulated through bacteria rich particles. 3. Particles and microorganisms are allowed to settle out forming Secondary Sludge ** Water is clear and free of organic wastes such as sewage**
Primary and Secondary Treatment
3. Tertiary Treatment A. B. C. D. Considered an advanced water treatment Variety of biological, chemical & physical processes Removes phosphorus & nitrogen Can be used to purify wastewater so that it can be reused in communities where water is scarce. Question to think about. What do we do with the primary and secondary sludge? 1. Anaerobic digestion 2. Fertilizer 3. Incineration 4. Ocean dumping 5. Sanitary landfill
Individual Septic Systems Many private residences use individual septic systems instead of municipal sewage treatment. Household sewage is piped into the septic tank Particles settle to the bottom Grease and oils form a scummy layer where bacteria decomposes it Waste water containing suspended organic and inorganic material flows into the drain field through a network of perforated pipes set in trenches of crushed stone Purified wastewater then percolates into the groundwater or evaporates from the soil
Do you see how there could be a contamination problem here?
Septic Systems The septic tank works much like primary treatment in municipal sewage treatmentsewage from the house is piped to the septic tank, where particles settle to the bottom Wastewater containing suspended organic and inorganic material flows into the drain field and gradually seeps into the soil
POLLUTION CONTROL THROUGH LEGISLATION The United States has attempted to control water pollution through legislation since the passage of the Refuse Act of 1899. - intended to reduce the release of pollutants into navigable rivers. Governments control point source pollution by 1. Imposing penalties on polluters 2. Taxing polluters to pay for the cleanup
SAFE DRINKING WATER ACT Prior to 1974, the states set their own standards for safe drinking water SAFE DRINKING ACT Set uniform federal standards Required EPA to determine the maximum contaminant level (MCL) which is the maximum permissible amount of any pollutant that might adversely affect human health. Amended in 1996 - requires municipal water suppliers to tell consumers what contaminants are present in their city’s water and if those pose a health risk.
CLEAN WATER ACT Controls the quality of rivers, lakes, aquifers, estuaries and coastal water in the United States. Original name: Water Pollution Control Act of 1972 Two basic goals: Eliminate discharge of pollutants in US waterways Attain water quality levels that make waterways safe to fish and swim in. EPA is required to set up and monitor national emission limitations maximum permissible amount of water pollutants that can be discharged from sewage treatment plants, factories and other point sources.
Clean Water Act continued…. Results Overall the CWA has been effective at improving the quality of water from point sources. Point sources must obtain permits from the National pollutant Discharge Elimination System to discharge untreated water. Non Point Source Pollution is more difficult and expensive to control CWA expanded in 1987 to allow National Pollutant Discharge System to include non point sources such as sediment from erosion from construction sites. NO real effective policy to address non-point source pollution.
Laws that Protect Groundwater Resource, Conservation and Recovery Act deals with the storage and disposal of hazardous wastes and helps prevent groundwater contamination. Safe Drinking Water Act contains provisions to protect underground aquifers that are important sources of drinking water. Also regulates underground injection of wastes. Several laws related to pesticides, strip mining and cleanup of abandoned hazardous waste sites (brownfields) also indirectly protect groundwater.
Effects of Salinized Soil on Plants Normally, the water concentration inside plant cells is lower than that in the soil resulting in a net movement of water into the root cell. When soil contains a high amount of salt, its relative water concentration can be lower than the water concentration inside cells. This causes water to move out of the roots into the soil, even when the soil is wet.