Units 7+8 Review Book Pt. 4 Flashcards
(33 cards)
Biomagnification
ood chains represent the flow of energy in an ecosystem, but other things can flow through food chains, too—including environmental toxins. While the amount of usable energy decreases at every level of the food chain, the concentration of certain toxins increases at each successive level, since most toxins cannot be broken down by organisms.
term used to describe the increasing concentration of these toxin molecules at successively higher trophic levels in a food chain.
Keep in mind that although really any type of molecule could be described using the terms bioaccumulation and biomagnification, generally these terms are used to describe toxins and heavy metals.
Effects of biomagnification
Some effects that can occur in an ecosystem when a persistent substance is biomagnified in a food chain include eggshell thinning and developmental deformities in top carnivores of the higher trophic levels.
Humans also experience harmful effects from biomagnification, including issues with the reproductive, nervous, and circulatory systems.
Ecologist Sandra Steingraber has pointed out that the production of breastmilk undergoes a final level of bioaccumulation (from the tissues of the mother’s body to the breastmilk) and thus infants’ food can contain even more of these substances than that of adults.
More generally, most types of water pollution can have many negative effects on ecosystems and on human health.
For example, heavy metals from mining operations and from the burning of fossil fuels, once they make their ways into the groundwater, can enter the drinking supply.
Diverse effects such as cancers, endocrine disruptions, nervous system damage, congenital disorders, heart and lung problems, and eye and kidney damage have been linked to heavy metals.
Mercury in particular has the added danger that when it enters aquatic environments in its elemental state, bacteria in the water quickly convert it to methyl-mercury, which is highly toxic.
Increased sediment of whatever kind in waterways can reduce light infiltration, which affects primary producers and visual predators, disrupting the food chain; furthermore, when the sediment settles it can wreak havoc on riverbed and other habitats.
Wetlands and mangroves are particularly sensitive to pollutants from agricultural and industrial waste.
Pollutants can cause more immediate problems ex. Oil spills
Even in ocean environments, pollutants can cause more immediate problems than the eventual degradation of habitat when pollutants overcome a given area’s ability to dilute them: oil spills, for example, can cause organisms to die from the hydrocarbons in oil.
Oil that floats on the surface of water can coat the feathers of birds and the fur of marine mammals, drowning them or impeding their everyday survival.
Some components of oil sink to the ocean floor, killing bottom-dwellers and ruining habitats there.
Even the oil that washes up on beaches can have economic consequences on the fishing and tourism industries and cause problems for shoreline habitats. Sediment runoff is one of the causes of the degradation of the major coral reefs of the world.
Among the most important factors in judging water quality are:
pH, which is a measure of acidity or alkalinity (normal for water is 6–8)
hardness, which is a measure of the concentrations of calcium and magnesium
dissolved oxygen—low levels of dissolved oxygen indicate an inability to sustain life (warm water holds less dissolved oxygen than cool water)
turbidity, or the density of suspended particles in the water
biological oxygen demand (BOD), which is a measure of the rate at which bacteria absorb oxygen from the water
Health effect of waste
Another group of water pollutants that are very dangerous to human health are infectious agents, such as those found in human and animal waste.
Fecal waste not only contains the symbiotic bacteria that aid in the human digestive processes, but also contains disease-causing bacteria.
Several human diseases, such as cholera and typhoid fever, are caused as a result of human waste entering the water source of a community.
In fact, the major reason for the increase in the life span of humans was not modern developments in medicine; it was the introduction of cleaner drinking water and better ways of disposing of wastewater.
Wastewater
The term wastewater is used to refer to any water that has been used by humans.
This includes human sewage; water drained from showers, tubs, sinks, dishwashers, and washing machines; water from industrial processes; and storm water runoff.
Water that is channeled into storm drains, such as storm water, is generally dumped directly into rivers. (This is why storm drain covers in many locations have been stenciled with warnings about not dumping material down them.)
History of wastewater treatment
Today in the United States, wastewater that isn’t storm water is moved through sewage pipes to a sewage treatment facility, but this was not always the case.
Sewage water once was, and in developing countries still is, merely dumped into the nearest river or ocean.
While some amounts of sewage can be diluted and broken down in these waters, too much waste poses serious risks to human health and the health of the aquatic ecosystems.
First step: physical treatment
Now in the United States, sewage pipes deliver wastewater to a municipal sewage treatment plant, where it is first filtered through screens (in what’s called a physical treatment) to remove debris such as stones, sticks, rags, toys, and other objects that were flushed down toilets.
This debris is then usually separated and sent to a landfill.
Primary treatment
The remaining water is passed into a settling tank, where suspended solids settle out as sludge—chemically treated polymers may be added to help the suspended solids separate and settle out.
Removes about 60 percent of the suspended solids and 30 percent of the organic waste that requires oxygen in order to decompose.
Secondary treatment
refers to the biological treatment of the wastewater in order to continue to remove biodegradable waste.
This treatment can be done using trickling filters, in which aerobic bacteria digest waste as it seeps over bacteria-covered rock beds.
Alternately, the wastewater can be pumped into an activated sludge processor, which is basically a tank filled with aerobic bacteria.
The solids in the water, including the bacteria, are once again left to settle out.
The solids remaining are considered sludge, which is combined with the sludge from the primary treatment.
Sludge used to be dumped into the ocean, but that practice has been banned. Instead, the sludge is further processed with anaerobic bacteria (to break down more organic material).
This digestion also produces methane gas that can be used as an alternative fuel to run the treatment plant.
After drying, this sludge cake can be processed and sold as fertilizer.
At the end of secondary treatment
97 percent of the suspended solids; 95–97 percent of the organic waste; 70 percent of the toxic metals, organic chemicals, and phosphates; 50 percent of the nitrogen; and 5 percent of the dissolved salts have been removed from the wastewater.
However, almost no persistent organic chemicals, such as pesticides, are removed, nor are radioactive isotopes.
Post secondary treatment
Generally, after secondary treatment, the wastewater is chlorinated to remove any remaining living cells and then discharged into a stream, the ocean, or water that’s used to water lawns.
A negative effect of the final chlorination of the water is that trihalomethanes (potential carcinogens) can be formed when any organic matter left in the water reacts with the chlorine, and this is problematic.
Two alternate processes to chlorination—ozonation and UV radiation—have been used to treat secondary-treatment water, but they have not proven to be as effective or long-lasting as chlorine and are also much more expensive.
Sometimes tertiary treatment
Some municipal plants deposit wastewater directly into ground water; this is done in San Jose Creek in Los Angeles County, for example.
In these places, the water must be further treated by tertiary treatment.
Tertiary treatment involves passing the secondary treated water through a series of sand and carbon filters and then further chlorination.
At the San Jose Creek Plant, the tertiary treated water from the reclamation plants is discharged into percolation basins, where it replenishes groundwater, or it is used for irrigation and for watering lawns, golf courses, and plants in nurseries.
Tertiary treatment is expensive, but in arid or semi-arid regions, every gallon that can be reclaimed is one that needs not come from rapidly depleting sources, such as diminished rivers or underground aquifers.
Private wastewater treatment
Private wastewater treatment in the form of septic tank systems is hallmarked by some as the most environmentally friendly type of waste disposal.
Septic tanks act in a way that’s similar to the primary and secondary treatments that take place in municipal treatment plants.
The water is then discharged into leachate (drain) fields. In order to install these types of systems, the soil must be able to percolate the water—that is, the water must be made to move from the top of the soil though its various horizons.
Some clay soils are not porous enough to allow percolation and thus are unsuitable for a septic field.
Clean Water Act
1972
Used regulatory and non-regulatory tools to protect all surface waters in the United States.
Sharply reduced direct pollutant discharges into waterways
financed municipal wastewater treatment facilities to manage polluted runoff
achieved the broader goal of restoring and maintaining the chemical, physical, and biological integrity of the nation’s waters
supported “the protection and propagation of fish, shellfish, and wildlife, and recreation in and on the water”
Safe Drinking Water Act
1974, 1996, 2005, 2011, 2015
Established a federal program to monitor and increase the safety of the drinking water supply. It does not apply to wells that supply fewer than 25 people.
Amendments in recent years have led to more stringent regulation of lead and algal toxins in drinking water.
Solid waste
Any discarded material that is not a liquid or gas.
It is generated in the domestic, industrial, business, and agricultural sectors, and it can consist of hazardous waste, industrial solid waste, or municipal waste.
Many types of solid waste provide a threat to human health and the environment.
Steps needed to reduce the amount of solid waste to deal with
The phrase “reduce, reuse, recycle” might seem simplistic, but it does outline the steps needed to reduce the amount of solid waste that must be dealt with.
Reduce
of course, refers to the minimizing of disposable waste.
For example, there are many types of packaging that are extremely wasteful—if you keep an eye out, you’ll see them everywhere.
Reducing or eliminating the amount of packaging per item sold is one way disposable waste can be sensibly reduced.
Reuse
applies to products that in some cases are disposable, but can be put to alternative use—sometimes over and over again —before their eventual disposal. For example, refillable bottles and tanks, reusable packing materials, secondhand goods, and cloth shopping bags all represent a reduction in waste when compared to single-use items.
Finally, recycling
the reuse of materials
Recycling offers the benefit of reducing the global demand for new minerals, but the process is energy-intensive and can be costly.
Primary recycling,
materials such as plastic or aluminum are used to rebuild the same product—an example of this is the use of the aluminum from aluminum cans to produce more aluminum cans.
Secondary recycling
materials are reused to form new products that are usually lower quality goods—examples of this are old tires recycled to form carpet, and plastic bottles recycled to create decking material.
Composting
Finally, another environmentally important process is composting.
Composting, the process of allowing organic matter such as food scraps, paper, and yard waste, to decompose, allows the organic material in solid waste to be decomposed and reintroduced into the soil rather than take up space in landfills.
The product of this decomposition, known as compost, is useful as fertilizer.
Drawbacks to composting include its odor and the attraction of rodents and other pests.
Recycling and composting is very effective, measures to encourage
According to the EPA, one of the most effective steps in aiding the environment that occurred in the 20th century was the marked growth in the use of recycling and composting to deal with solid waste.
Of the 292.4 million tons of municipal solid waste produced in the United States in 2018, over 69 million tons were recycled.
According to the EPA, the following percent of each of these materials was recycled in the year 2018
In order to encourage people to reduce, reduce, and recycle, many communities have established Pay-As-You-Throw (PAYT) programs, which charge municipal customers for the amount of household garbage they throw away.
As you can imagine, this has been a strong incentive for people to practice these good habits.
An example of an incentive program that has worked beautifully is the bottle redemption bill.
Ten states have enacted bottle bills and they have worked fantastically, especially in Michigan, which has a ten-cent redemption fee.
Sanitary landfills
Modern landfills are very different from the traditional caricature of a garbage dump filled with heaps of junked cars and rats foraging for food scraps.
Federal regulations that protect human health and the environment have paved the way for sanitary landfills.
For example, federal law prohibits landfills from being located near geological faults, wetlands, or flood plains.
Additionally, landfill sites are periodically required to dig large holes in the ground and line them with geomembranes or plastic sheets that are reinforced with two feet of clay on the bottom and sides.
Smoothing wet clay is much like making a clay pot; the layer that is created is virtually impermeable.
Also, the waste in the landfill must be frequently covered with soil in order to control insects, bacteria, rodents, and odor; and the decomposed material that percolates to the bottom of the landfill (called leachate) is piped to the top of the site and collected in leachate ponds, which are closely monitored.
The rate at which the material decomposes depends on things like what the trash is composed of and what conditions are present for the microbes responsible for decomposing the waste.
Gases from the landfill, like methane, may even be piped up from the site and used to generate electricity.
Sometimes the methane is burned in continuously flaming flares to avoid larger fires or explosions.
To ensure that landfills do not contaminate the environment, they are required to be positioned at least six feet above the water table, and groundwater at the sites must be tested frequently for quality.
When one site (hole) is full, it must be capped with an engineered cover, monitored, and provided with long-term care.
Landfill mitigation measures
Of course, more and more landfills are needed to keep up with human waste.
The question arises of how to best make use of closed landfills. Landfill mitigation strategies range from burning waste for energy to restoring habitat on former landfills for use as parks.
Some countries dispose of their waste by dumping it in the ocean.
This practice, along with other sources of plastic, has led to large floating islands of trash in the oceans.
Litter that reaches aquatic ecosystems, besides being unsightly, can introduce toxic substances to the food chain.
Additionally, wildlife can become entangled in the waste, as well as ingest it; this can create intestinal blockage and choking hazards for wildlife.
Waste-to-Energy program
