Presentation on theme: "Water Pollution APES: Ch. 14. Water Pollution Is defined as the contamination of streams, rivers, lakes, oceans, or groundwater with substances produced."— Presentation transcript:
Water Pollution APES: Ch. 14
Water Pollution Is defined as the contamination of streams, rivers, lakes, oceans, or groundwater with substances produced by human activity that negatively affect organisms. – Has potential to impact both aquatic & terrestrial organisms – Pollution can either come from point sources or nonpoint sources
Point Sources vs. Nonpoint Sources Point sources are: – Distinct locations like factories or sewage treatment plants that discharge pollution into a body of water. – Easier to pinpoint source of pollution Nonpoint sources are: – Diffuse areas like an entire farming region, suburban community, or storm run-off from parking lots. – Harder to control pollution from these sources
NONPOINT SOURCES Urban streets Suburban development Wastewater treatment plant Rural homes Cropland Factory Animal feedlot POINT SOURCES
Human Wastewater This is produced by human activities including: – Sewage, gray water, bathing, washing clothes & dishes. – Biggest challenge? To keep wastewater from contaminating drinking water. Can be difficult because many use same water source for drinking, bathing, washing, and disposing of sewage.
Human Wastewater Three major reasons wastewater is a concern: – Wastewater naturally undergoes decomposition by bacteria, which creates a demand for dissolved oxygen (Oxygen Demand). – Nutrients in released in wastewater decomposition can make water sources eutrophic (Nutrient Release). – Wastewater can carry a wide variety of disease- causing organisms.
Oxygen Demand Oxygen-demanding waste: – Dissolved oxygen in water is used by many animals in respiration. – Organic matter that enters a body of water & feeds the growth of decomposers (microbes). – Microbes require oxygen to decompose waste – More waste... More oxygen needed
Oxygen Demand Measured in terms of biochemical oxygen demand (BOD) – The amount of oxygen a quantity of water uses over a period of time at a specific temperature. – Lower BOD = body of water is less polluted by wastewater, whereas, higher BOD = body of water is more polluted by wastewater. Normal = 5 to 20 mg of oxygen due to decomposition of leaves, twigs etc. High = 200 mg of oxygen due to decomposition of domestic wastewater.
Oxygen Demand Dead Zones: – High BOD due to decomposition – Dissolved oxygen is too low for other organisms to survive (lethal). – Some areas there is so little oxygen that life is absent. – These areas are called “dead zones” Can be self-perpetuating due to dying organisms decomposing causing continued BOD Mississippi delta in Gulf of Mexico UN estimates 200 dead zones globally
Fig. 21-A, p. 507 Mississippi River Basin TX MS LA Mississippi River Gulf of Mexico Ohio River Mississippi River Missouri River Depleted oxygen LOUISIANA Gulf of Mexico
Nutrient Release Products of decomposition: – Include nitrates (NO 3 -2 ) & phosphates (PhO 4 -2 ) Additional nutrient sources: – Soaps & detergents Provides abundance of nutrients to a body of water – Called eutrophication – Anthropogenic inputs of nutrients is called cultural eutrophication – Produces algal blooms which die & decompose – Chain of events that leads back to low oxygen – Chesapeake Bay is an example
Pollution of Freshwater Lakes by Cultural Eutrophication Overgrowth -> Breakdown -> Fish Kills -> Anaerobic Bacteria Algae, cyanobacteria, water hyacinth, duckweed Breakdown of these plants consumes oxygen Less O 2 causes organisms to die Produce toxic HS and flammable CH
Chesapeake Bay Point Source - Industry – 60% of phosphates, toxic waste Non point Source – Agriculture/Municipal – 60% Nitrates, pesticides
Ocean Pollution DILUTE-DISPERSE-DEGRADE Can handle a lot of pollutants Arguments over safety – Safer than burying vs. – Delaying pollution prevention – Promotes degradation of ocean and connected wetlands Red Tide – eutrophication in ocean Release Toxins Damage fisheries Kills birds Poison Seafood
Fig , 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
Disease-causing Organisms Wastewater carries a variety of pathogens: – Viruses, bacteria, and parasites Water-born diseases are: – Cholera, typhoid fever, stomach flu, diarrhea – Worldwide most common: cholera and hepatitis – In USA, hepatitis A & bacterium Cryptosporidium – Large-scale outbreaks are rare in US, but common in developing world.
Water Born Disease Statistics 1.1 billion do not have access to safe drinking water. Diarrheal diseases can be prevented by: – Safe drinking water, proper sanitation, & proper hygiene 42% of world population lacks access to proper sanitation – Over half live in China & India – In sub-Saharan Africa only 36% have access
Disease-causing Organisms Not feasible to test water for all pathogens Scientists use indicator species – – An organism that indicates whether or not disease-causing pathogens are likely to be present. – Best indicator: fecal coliform bacteria Generally harmless micro-organisms that live in human intestines Most common is Escherichia coli or E. coli
Treatment of Wastewater Two most widespread systems for treating human sewage is: – Septic systems – found in rural areas with low population density. – Sewage treatment plants – found in areas of high population density such as urban & suburban System to treat wastewater from large livestock operations (feed lots) is a manure lagoon.
Septic Systems Septic system is a simple system with two components: – Septic tank (1,900 – 4700 L): Buried underground near house Three layers develop: – Scum layer (top): anything that floats & rises to the top – Sludge layer (bottom): anything heavier than water sinks – Septage (middle): layer of fairly clear water that contains bacteria, pathogenic organisms, and nutrients (PO 4 -2, NO 3 -2 )
Septic Systems – Leach field: Septage moves by gravity out of tank to underground pipes which lie below the lawn Septage slowly seeps out due to perforations in the pipe. Septage is filtered by surrounding soil & changed into CO 2 and nutrients. Pathogens can: – Become part of the sludge – Be outcompeted by other micoorganisms – Be degraded by soil micoorganisms in leach field – Pro: no electricity needed to run septic system, but sludge needs to be removed periodically.
Sewage Treatment Plant Managed by municipalities that are centralized. Two steps to treating sewage- – Primary treatment: Goal is for solids to settle out of wastewater Solids are dried & exposed to bacteria that can digest pathogens; this material is called sludge. Final product is either dumped in landfills, burned, or converted into fertilizer
Sewage Treatment Plant – Secondary Treatment: Involves the remaining wastewater Goal is to use bacteria to break down 85 – 90% of organic matter and convert it into CO 2 and nutrients Processes include – – Aeration to promote growth of aerobic bacteria (less odoriferous than anaerobic bacteria) – Secondary wastewater is left in settling ponds for several days to remove any remaining particles – Disinfection using chlorine, ozone, or UV light kills remaining pathogens – Final product is released into nearby river, lake, or ocean
Manure Lagoons Animal waste problems similar to human waste. Only a problem when on a large scale like concentrated feed lots. Manure from feed lots contains antibiotics & hormones Large amounts of manure are handled in manure lagoons – Large, human-made ponds lined with rubber.
Manure Lagoons Manure is broken down by bacteria (same as in sewage treatment plants) Manure can be spread of farm fields Risk of manure lagoons – – Leaks in rubber can contaminate groundwater – Overflow to adjacent water bodies – Application as fertilizer can runoff to nearby water bodies