2Water PollutionIs 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 organismsPollution can either come from point sources or nonpoint sources
3Point 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 pollutionNonpoint 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
5Human 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.
6Human 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.
7Oxygen 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 wasteMore waste More oxygen needed
8Oxygen 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.
9Oxygen 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 BODMississippi delta in Gulf of MexicoUN estimates 200 dead zones globally
10Missouri River Mississippi River Basin Ohio River MS LA Gulf of MexicoOhio RiverMissouri RiverDepleted oxygenLOUISIANAMississippiRiver BasinMSFigure 21.ANatural capital degradation: a large zone of oxygen-depleted water (less than 2 ppm dissolved oxygen) forms for half of the year in the Gulf of Mexico as a result of oxygen-depleting algal blooms. Evidence indicates that it is created mostly by huge inputs of nitrate (NO3−) and phosphate (PO43−) ions from farms, cities, and factories in the vast Mississippi River basin. The satellite image (bottom left) shows the inputs of such nutrients into the Gulf of Mexico during the summer of In the image, reds and greens represent high concentrations of phytoplankton and river sediment. This problem is worsened by loss of wetlands, which help filter plant nutrients. (NASA)LATXFig. 21-A, p. 507
12Nutrient Release Products of decomposition: Include nitrates (NO3-2) & phosphates (PhO4-2)Additional nutrient sources:Soaps & detergentsProvides abundance of nutrients to a body of waterCalled eutrophicationAnthropogenic inputs of nutrients is called cultural eutrophicationProduces algal blooms which die & decomposeChain of events that leads back to low oxygenChesapeake Bay is an example
13Pollution of Freshwater Lakes by Cultural Eutrophication 1234Some lakes become eutrophic naturally but some do not, it depends on the conditions.Overgrowth -> Breakdown -> Fish Kills -> Anaerobic BacteriaAlgae, cyanobacteria, water hyacinth, duckweedBreakdown of these plants consumes oxygenLess O2 causes organisms to dieProduce toxic HS and flammable CH4
14Chesapeake BayShallow estuary with slow flow. Caused problems with local fisheries and farms on the coast.Point Source - Industry – 60% of phosphates, toxic wasteNon point Source – Agriculture/Municipal – 60% Nitrates, pesticides
16Ocean Pollution DILUTE-DISPERSE-DEGRADE Can handle a lot of pollutants Arguments over safetySafer than buryingvs.Delaying pollution preventionPromotes degradation of ocean and connected wetlandsRed Tide – eutrophication in oceanRelease ToxinsDamage fisheriesKills birdsPoison Seafood
17and heavy metals in effluents flow into bays and estuaries. Cities IndustryNitrogen oxidesfrom autos andsmokestacks,toxic chemicals,and heavy metals in effluents flow into bays and estuaries.CitiesToxic metals and oil from streets and parking lots pollute waters;Urban sprawlBacteria and viruses fromsewers and septic tanks contaminate shellfish bedsConstruction sitesSediments are washed intowaterways, choking fish and plants, clouding waters, and blocking sunlight.FarmsRunoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus.Red tidesExcess nitrogen causesexplosive growth oftoxicmicroscopic algae,poisoning fish andmarine mammals.Closedshellfish bedsClosedbeachOxygen-depletedzoneFigure 21.10Natural capital degradation: residential areas, factories, and farms all contribute to the pollution of coastal waters and bays. According to the UN Environment Programme, coastal water pollution costs the world $16 billion annually—$731,000 a minute—due to ill health and premature death.Toxic sedimentsChemicals and toxic metals contaminate shellfish beds, kill spawning fish, andaccumulate in the tissues of bottom feeders.Oxygen-depleted zoneSedimentation and algaeovergrowth reduce sunlight,kill beneficial sea grasses, useup oxygen, and degrade habitat.Healthy zoneClear, oxygen-richwaters promote growthof plankton and sea grasses,and support fish.Fig , p. 505
18Disease-causing Organisms Wastewater carries a variety of pathogens:Viruses, bacteria, and parasitesWater-born diseases are:Cholera, typhoid fever, stomach flu, diarrheaWorldwide most common: cholera and hepatitisIn USA, hepatitis A & bacterium CryptosporidiumLarge-scale outbreaks are rare in US, but common in developing world.
19Water 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 hygiene42% of world population lacks access to proper sanitationOver half live in China & IndiaIn sub-Saharan Africa only 36% have access
20Disease-causing Organisms Not feasible to test water for all pathogensScientists use indicator species –An organism that indicates whether or not disease-causing pathogens are likely to be present.Best indicator: fecal coliform bacteriaGenerally harmless micro-organisms that live in human intestinesMost common is Escherichia coli or E. coli
21Treatment 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 & suburbanSystem to treat wastewater from large livestock operations (feed lots) is a manure lagoon.
22Septic Systems Septic system is a simple system with two components: Septic tank (1,900 – 4700 L):Buried underground near houseThree layers develop:Scum layer (top): anything that floats & rises to the topSludge layer (bottom): anything heavier than water sinksSeptage (middle): layer of fairly clear water that contains bacteria, pathogenic organisms, and nutrients (PO4-2, NO3-2)
23Septic Systems Leach field: Septage moves by gravity out of tank to underground pipes which lie below the lawnSeptage slowly seeps out due to perforations in the pipe.Septage is filtered by surrounding soil & changed into CO2 and nutrients.Pathogens can:Become part of the sludgeBe outcompeted by other micoorganismsBe degraded by soil micoorganisms in leach fieldPro: no electricity needed to run septic system, but sludge needs to be removed periodically.
25Sewage Treatment Plant Managed by municipalities that are centralized.Two steps to treating sewage-Primary treatment:Goal is for solids to settle out of wastewaterSolids 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
26Sewage Treatment Plant Secondary Treatment:Involves the remaining wastewaterGoal is to use bacteria to break down 85 – 90% of organic matter and convert it into CO2 and nutrientsProcesses 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 particlesDisinfection using chlorine, ozone, or UV light kills remaining pathogensFinal product is released into nearby river, lake, or ocean
28Manure 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 & hormonesLarge amounts of manure are handled in manure lagoonsLarge, human-made ponds lined with rubber.
29Manure LagoonsManure is broken down by bacteria (same as in sewage treatment plants)Manure can be spread of farm fieldsRisk of manure lagoons –Leaks in rubber can contaminate groundwaterOverflow to adjacent water bodiesApplication as fertilizer can runoff to nearby water bodies