Pollution - Environmental Science - page 160

• Pathogens and waterborne diseases exist in surface waters and can enter the drinking water supply if
water is untreated. Protists, bacteria, and pathogenic viruses can cause serious health effects in humans,
entering the water supply through runoff from sewage and animal manure.
Marine Ecosystems
Marine environments also suffer from the impacts of pollution. For many decades, the oceans were thought to
be endless, so waste was dumped into them without thought of repercussion. Now the issues of polluting mar-
ine environments are being addressed and understood. Forms of pollution include oil pollution, excess nutri-
ents, sewage, and trash such as plastics, debris, and fishing equipment.
Most oil pollution reaches the oceans through runoff from hard surfaces on the land, especially roads. Other
sources include maintenance of ships, natural seepage from the ocean floor, and spills such as the Exxon
Valdez supertanker rupture and the Deepwater Horizon (BP) drilling rig explosion. Oil spills can drastically
impact the economy, most directly through the loss of fisheries and decreased tourism. Losses to these indus-
tries ripple through a local economy. Additionally, spilled oil carried in currents can reach sites far from the
original disaster.
Trash reaches the ocean from the occupants of boats, damaged or sunken boats, barges dumping the refuse of
coastal cities, offshore winds, and water runoff. To exacerbate the problem, trash is then carried by ocean cur-
rents, waves, and gyres, sometimes traveling hundreds of miles from the original source of the trash. One espe-
cially visible effect of trash on the marine ecosystem is to sea turtles, which frequently eat and are killed by
floating plastic bags, which look much like their natural prey, jellyfish.
Maintaining Water Quality
The United States government has put in place water quality standards to maintain water quality in both fresh-
water and marine ecosystems. Drinking, ground, and surface water quality is tested for potential threatening
levels of nutrient concentrations, fecal coliform bacteria (from sewage), hardness, pH, turbidity (suspended
particles), and dissolved oxygen content. Additionally, during the past few decades, The Environmental Protec-
tion Agency (EPA) and other organizations have made efforts to reduce sources of water pollution. These
sources include leaking underground storage tanks, illegal dumping of toxic chemicals, and proper manage-
ment of landfills, runoff, and other waste. The EPA also has set standards for concentrations of over 80 con-
taminants likely to be found in drinking water. The Clean Water Act also has reduced water contamination,
helping to maintain safer water quality for both humans and ecosystems.
Clean Water Act
The Clean Water Act was created in 1972 and amended in 1977 to protect the America's freshwater
sources. Specifically, it was established to regulate the discharge of pollutants into waterways while also
establishing quality standards for surface waters, including wastewater standards for industries.
Wastewater Purification and Sewage Treatment
Wastewater is generated by humans. After water is used and before it is released back into the environment, it
is put through a cleaning process, commonly using a septic system or a municipal sewer system.
Septic systems are constructed directly on the property where they are used. Wastewater travels from the
house to a septic tank buried underground, where solids, oils, and water naturally separate by density. The
wastewater then travels to an empty field, or lawn area, where the waste products continue to be decomposed