Presentation on theme: "Chapter 21 Water Pollution. Core Case Study: Using Nature to Purify Sewage Ecological wastewater purification by a living machine. Uses the sun and."— Presentation transcript:
Core Case Study: Using Nature to Purify Sewage Ecological wastewater purification by a living machine. Uses the sun and a series of tanks containing plants, snails, zooplankton, crayfish, and fish (that can be eaten or sold for bait). Uses the sun and a series of tanks containing plants, snails, zooplankton, crayfish, and fish (that can be eaten or sold for bait). Figure 21-1
WATER POLLUTION: SOURCES, TYPES, AND EFFECTS Point source: specific location (drain pipes, ditches, sewer lines) Nonpoint source: cannot be traced to a single site of discharge (atmospheric deposition, agricultural / industrial / residential runoff)
Water Quality Factors DO BOD Fecal coliform - 0/100 ml for drinking water, 200 colonies/100 ml for swimming Chemical analysis Indicator species Visual analysis Figure 21-3
Water Pollution Problems in Streams Oxygen sag curve (5 zones) Factors affecting it: volume, temp, flow rate, pH Figure 21-4
Case Study: India’s Ganges River: Religion, Poverty, and Health Religious beliefs, cultural traditions, poverty, and a large population interact to cause severe pollution of the Ganges River in India. Very little of the sewage is treated. Very little of the sewage is treated. Hindu believe in cremating the dead to free the soul and throwing the ashes in the holy Ganges. Hindu believe in cremating the dead to free the soul and throwing the ashes in the holy Ganges. Some are too poor to afford the wood to fully cremate.Some are too poor to afford the wood to fully cremate. Decomposing bodies promote disease and depletes DO.Decomposing bodies promote disease and depletes DO.
POLLUTION OF FRESHWATER LAKES Dilution of pollutants in lakes is less effective - Lakes and reservoirs are often stratified and undergo little mixing. - Low flow makes them susceptible to runoff - Cultural eutrophication
POLLUTION OF GROUNDWATER It can take hundreds to thousand of years for contaminated groundwater to cleanse itself of degradable wastes. Nondegradable wastes (toxic lead, arsenic, flouride) are there permanently. Nondegradable wastes (toxic lead, arsenic, flouride) are there permanently. Slowly degradable wastes (such as DDT) are there for decades. Slowly degradable wastes (such as DDT) are there for decades. Groundwater has low flow rates, few bacteria, & cold temps - all slow down recovery time Groundwater has low flow rates, few bacteria, & cold temps - all slow down recovery time Avg. recycling time for groundwater = 1400 years Avg. recycling time for groundwater = 1400 years
Fig. 21-8, p. 502 Aquifer Water well Migrating vapor phase Contaminant plume moves with the groundwater Free gasoline dissolves in groundwater (dissolved phase) Groundwater flow Water table Gasoline leakage plume (liquid phase) Leaking tank Bedrock
Case Study: Arsenic in Groundwater - a Natural Threat Toxic Arsenic (As) can naturally occur at high levels in soil and rocks. Drilling into aquifers can release As into drinking water supplies. According to WHO, more than 112 million people are drinking water with As levels 5- 100 times the 10 ppb standard. Mostly in Bangladesh, China, and West Bengal, India. Mostly in Bangladesh, China, and West Bengal, India.
Fig. 21-9, p. 504 Solutions Groundwater Pollution CleanupPrevention Find substitutes for toxic chemicals Install monitoring wells near landfills and underground tanks Require leak detectors on underground tanks Ban hazardous waste disposal in landfills and injection wells Store harmful liquids in aboveground tanks with leak detection and collection systems Pump to surface, clean, and return to aquifer (very expensive) Pump nanoparticles of inorganic compounds to remove pollutants (may be the cheapest, easiest, and most effective method but is still being developed) Keep toxic chemicals out of the environment Inject microorganisms to clean up contamination (less expensive but still costly)
OCEAN POLLUTION Red tides Dead zones (usually about 61/year) Figure 21-11
Fig. 21-10, p. 505 Healthy zone Clear, oxygen-rich waters promote growth of plankton and sea grasses, and support fish. Oxygen-depleted zone Sedimentation and algae overgrowth reduce sunlight, kill beneficial sea grasses, use up oxygen, and degrade habitat. Red tides Excess nitrogen causes explosive growth of toxicmicroscopic algae, poisoning fish and marine mammals. Farms Runoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus. Toxic sediments Chemicals and toxic metals contaminate shellfish beds, kill spawning fish, and accumulate in the tissues of bottom feeders. Construction sites Sediments are washed into waterways, choking fish and plants, clouding waters, and blocking sunlight. Urban sprawl Bacteria and viruses from sewers and septic tanks contaminate shellfish beds Oxygen-depleted zone Closed beach Cities Toxic metals and oil from streets and parking lots pollute waters; Industry Nitrogen oxides from autos and smokestacks, toxic chemicals, and heavy metals in effluents flow into bays and estuaries. Closed shellfish beds
Oxygen Depletion in the Northern Gulf of Mexico A large zone of oxygen- depleted water forms for half of the year in the Gulf of Mexico as a result of algae blooms. Figure 21-A
Case Study: The Chesapeake Bay – An Estuary in Trouble Largest US estuary Shallow Slow flushing (1%) High phosphates, nitrates, mercury, lead Figure 21-12
OCEAN OIL POLLUTION Most ocean oil pollution comes from human activities on land. Studies have shown it takes about 3 years for many forms of marine life to recover from large amounts of crude oil (oil directly from ground). Studies have shown it takes about 3 years for many forms of marine life to recover from large amounts of crude oil (oil directly from ground). Recovery from exposure to refined oil (fuel oil, gasoline, etc…) can take 10-20 years for marine life to recover. Recovery from exposure to refined oil (fuel oil, gasoline, etc…) can take 10-20 years for marine life to recover.
Fig. 21-14, p. 509 Reduce input of toxic pollutants Solutions Coastal Water Pollution PreventionCleanup Use wetlands, solar-aquatic, or other methods to treat sewage Require at least secondary treatment of coastal sewage Sprinkle nanoparticles over an oil or sewage spill to dissolve the oil or sewage without creating harmful by-products (still under development) Improve oil-spill cleanup capabilities Recycle used oil Regulate coastal development Protect sensitive areas from development, oil drilling, and oil shipping Ban ocean dumping of sludge and hazardous dredged material Ban dumping of wastes and sewage by maritime and cruise ships in coastal waters Separate sewage and storm lines Require double hulls for oil tankers
PREVENTING AND REDUCING SURFACE WATER POLLUTION Prevent runoff Buffer zone vegetation Reduce erosion Clean Water Act - increases fishable/swimmable lakes, cuts erosion, increases sewage treatment, decreases wetland loss Water Quality Act - drinking water supplies
Reducing Water Pollution through Sewage Treatment Septic tanks and various levels of sewage treatment can reduce point-source water pollution. Figure 21-15
Reducing Water Pollution through Sewage Treatment Primary sewage treatment: a physical process that uses screens and a grit tank to remove large floating objects and allows settling - removes 60% of solids Secondary sewage treatment: a biological process in which aerobic bacteria remove as much as 90% of dissolved and biodegradable, oxygen demanding organic wastes.
Reducing Water Pollution through Sewage Treatment Primary and Secondary sewage treatment. Figure 21-16
Reducing Water Pollution through Sewage Treatment Advanced or tertiary sewage treatment: Uses series of chemical and physical processes to remove specific pollutants left (especially nitrates and phosphates). Uses series of chemical and physical processes to remove specific pollutants left (especially nitrates and phosphates). Water is chlorinated to remove coloration and to kill disease-carrying bacteria and some viruses (disinfect). Some areas use natural wetlands.
Is Bottled Water the Answer? Some bottled water is not as pure as tap water and costs much more. 1.4 million metric tons of plastic bottles are thrown away. 1.4 million metric tons of plastic bottles are thrown away. Fossil fuels are used to make plastic bottles. Fossil fuels are used to make plastic bottles. The oil used to produce plastic bottles in the U.S. each year would fuel 100,000 cars.The oil used to produce plastic bottles in the U.S. each year would fuel 100,000 cars.
Water Laws SDWA ‘74 - EPA establishes national drinking water standards - not on wells Water Quality Act ‘65 - established water quality standards for streams Ocean Dumping Act ‘72 - must have permit to dispose of materials Clean Water Act - federal assistance for sewage treatment, permit to discharge, EPA sets pollution standards