8) Recycling programs have become quite common in municipalities across the U.
Explain why local governments would bother to recycle when the cost of the programs oftentimes exceeds the value of the raw materials being recycled? 9) Suppose that your community has a large sewage treatment plant which is discharging nitrogen-rich wastewater into a nearby stream.
Describe how the introduction of excessive amounts of nutrients (e.
, nitrogen) can affect the water quality downstream of the sewage plant.
10) As shown in Figure 12.
3, sewage and stormwater drains typically share the same set of underground pipes.
During heavy rains these combined systems often become overloaded to the point where untreated wastewater is allowed to discharge directly into a stream.
Describe the type of downstream water-quality problems you would expect when this occurs.
11) Recent studies have documented the presence of a wide range of hormones and antibiotics in U.
streams—these compounds originate from the medicines we take.
Because streams serve as the water supply for many municipalities, large numbers of people are likely being exposed to these compounds.
Although the concentrations are low, data are lacking as to the long-term effect on human health.
a) If the source of your city's drinking water is a stream, what would you do until more scientific data becomes available? Note that bottled water may not be a solution as it is often times just city water.
b) How could you personally, as a citizen, help reduce the amount of pharmaceuticals that are entering our water supplies? 12) Figure 12.
4 illustrates how a septic tank and drain field is used to treat household wastewater.
a) Explain why it is so important that the drain field and gravel bed of the septic system be located well above the water table.
b) Describe a common landscape position where people like to build homes, but where the geologic conditions make it nearly impossible for septic tanks to function properly 13) Explain what inevitably happens when homeowners fail to have the sludge periodically pumped out of their septic tanks.
14) Figure 12.
5 shows the drainage basin of the Mississippi River and the hypoxic or dead zone that has developed in the Gulf of Mexico.
Here, excessive amounts of nutrients are being carried by the modern Mississippi and then discharged into the Gulf of Mexico, causing an oxygen-depleted (i.
, hypoxic) zone.
a) Describe at least two anthropogenic (human) sources for the excessive nutrients being carried by the modern Mississippi.
b) Explain how the oxygen-depleted zone in the Gulf of Mexico would impact both the marine life and human economy in the region.
15) Describe how humans living in the Mississippi drainage basin might be able to reduce the amount of nutrients entering the drainage system, and thereby help minimize the oxygen depletion problem in the Gulf.