As this goes up, DO goes down.

This is caused by degradable wastes.

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.

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.

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.

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.

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.

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.

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.

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.

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.