Water Pollution

biological oxygen demand
As this goes up, DO goes down. This is caused by degradable wastes.
oxygen sag curve
In a flowing stream, the breakdown of degradable wastes by bacteria depletes dissolved oxygen and creates this. This reduces or eliminates populations of organisms with high oxygen requirements until the stream is cleansed of wastes.
The natural nutrient enrichment of a shallow lake, estuary, or slow-moving stream, mostly from runoff of plant nutrients such as nitrates and phosphates from surrounding land.

cultural eutrophication
Near urban or agricultural areas, human activities can greatly accelerate the input of plant nutrients to a lake. It is mostly nitrate- and phosphate-containing effluents from various sources that cause such a change.
An _______ lake is low in nutrients and its water is clear.

During hot weather or drought, cultural eutrophication produces dense growths or blooms or organisms such as algae and cyanobacteria and thick growths or water hyacinths and other quatic plants. These dense colonies of plant life can reduce lake productivity and fish growth by decreasing the input of solar energy needed for photosynthesis.
Dense colonies of plant life can reduce lake productivity and fish gworth by decreasing the input of solar energy needed for photosynthesis by ______ that support fish.

Citizen pressure on elected officials led to the development of a scheme to divert nutrient-rich ________ from Seattle’s sewage treatment plants into the nearby Puget Sound, where tides would mix them with ocean water.
baby-blue syndrome
The conversion of nitrates in tap water to nitritesin infants under 6 months old can cause a potentially fatatl condition known as _____, in which blood lacks the ability to carry sufficient oxygen to body cells.
Toxic ___________ contaminates drinking water when a well is drilled into aquifers with this-contaminated soils and rock.;Long-term exposure to _________ in drinking water is likely to cause 200,000 to 270,000 premature deaths from cancer of the skin, bladder, and lung in Bangladesh alone.

inadequate oxygenation of the blood
Clean Water Act
Sets standards for allowed levels of key water pollutants and requires polluter to get permits limiting how much of various pollutants they can discharge into aquatic systems
discharge trading policy
Uses market forces to reduce water pollution in the United States;A water pollution source is allowed to pollute at levels higher than allowed in its permit if it buys credits from permit holders with pollution levels below what they are allowed.
septic tank
Household sewage and wastewater is pumped into a settling basin, where grease and oil rise to the top and solids fall to the bottom and are decomposed by bacteria.;The resulting partially treated wastewater is discharged in a large drainage field through small holes in perforated pipes embedded in prous gravel or crushed stone just below the soil’s surface.
wastewater treatment plant
Raw sewage reaching _____________ typically undergoes one or both of two levels of wastewater treatment.

primary sewage treatment
a physical process that used screens and a grit tank to remove large floating objects and allow solids such as sand and rock to settle out The waste stream flows into a primary settling tank where suspended organisc solids settle out as sludge.
secondary sewage treatment
A biological process in which aerobic bacteria remove as much as 90% of dissolved and biodegradable, oxygen-demanding organic wastes
advanced (tertiary) sewage treatment
Uses a series of specialized chemical and physical processes to remove specific pollutants left in the water after primary and secondary care. Its most widespread use involves using special filters to remove phosphates and nitrates from wastewater beore it is discharged into surface waters to help reduce nutrient overload from nitrates and phosphates.
Sewage treatment produces a gooey ________ containg a slimy mixture of baceria-laden solids and often-toxic cemicals and metals when sewer systems mix industrial and household waste.

About 36% of the sludge is used to ertilize farmland, forests, golf courses, cemeteries, parkland, highway medians, and degraded land.
composting toilet systems
Eliminate sewage systems by switching to waterless _____________________ that are installed, maintained, and manged by professionals. These would be cheaper to instal and maintain that current sewage treatment because they do not require vast systems of underground pipes connected to centralized sewage treatment plants.

Safe Drinking Water Act

requires the EPA to establish national drinking water standards, called maximum containment levels, for any pollutants the may have adverse effects on human health