Water Quality Issues of Electricity Production:
Pollution of Water Bodies
What do we mean by water
Water bodies come
in many forms: huge oceans; large and small lakes; and a diversity of
rivers and streams. Each of these ecosystems feature a tapestry of waterborne
species that are all dependent upon a high degree of water quality. These
bodies of water are also essential to human survival and public health.
For example, underground aquifers often supply us with drinking water.
Waterways are also not only key transportation routes for billions of
dollars in global commerce, but they represent popular opportunities for
recreation in the form of fishing, boating and water sports. Some particularly
pristine spots in or near ocean, lakes and rivers may be candidate for
long-term preservation because of their stunning aesthetic values.
and continued operation of power plants, particularly those fueled by
fossil or nuclear fuels, are among the human activities that can have
the most profound and wide ranging negative impacts on water quality.
How can electricity production
impair water quality?
The following procedures
all can occur during routine operations and maintenance of power plants
and each can significantly impact water quality:
This waste stream results from periodic purging of the impurities that
become concentrated in steam boiler systems. These pollutants include
metals such as copper, iron and nickel, as well as chemicals added to
prevent scaling and corrosion of steam generator components.
run-off: This waste stream is created when water comes in contact
with coal storage piles maintained on the power plant site. While most
piles are kept covered, active piles used to meet the power plants immediate
needs are often open to the elements. Metals and other naturally occurring
contaminants contained in coal leach out with the rainfall and are deposited
in nearby water bodies.
wastes: Water used for power plant cooling is chemically altered
for purposes of extending the useful life of equipment and to ensure
efficient operation. Demineralized regenerants and rinses are chemicals
employed to purify waters used as makeup water for the plant's cooling
system. Cooling tower blowdown contains chemicals added to prevent biological
growth in the towers and to prevent corrosion in condensors.
wastes: These wastes derive from the chemical additives intended
to remove scale and other byproducts of combustion.
Thermal plants create or use steam in the process of creating electricity
require water for cooling. This water typically comes from adjacent
water bodies or groundwater sources and is discharged back into the
water body at significantly higher temperatures. By altering the temperature
in the "mixing zone," the discharge of thermal wastewater can both negative
and positive effects on aquatic life. On the plus side, the warmer temperature
water may create more favorable feeding and breeding conditions for
certain species located near the power plant's water source. However,
when the power plant is suddenly shut down for routine maintenance or
unplanned outage, the resulting wide swing to colder temperatures can
be lethal to sensitive fish populations. Hydropower dams can also alter
the natural temperature of the water, as discussed above.
the impacts of power production on water quality?
Many large central
station fossil and nuclear power plants rely upon water for cooling
and are therefore located near bodies of water. In some instances, the
diversion of rivers creates reservoirs adjacent to power plants for cooling,
rinsing and the releases of effluents. A variety of processes associated
with fuel handling and ongoing maintenance of large thermal power plants
create or concentrate chemical pollutants that are then discharged into
nearby water bodies. Even when releases are limited to what is allowed
in water use permits, there is still the occasional but inevitable accidental
Both of these sources
of pollution can be legal and alone can cause significant harm to streams,
rivers, lakes, estuaries and groundwater. Water quality can degrade to
the point where fish and other aquatic life populations decline - even
when power plant operators abide by water permit restrictions. Often,
the water used in the power plant is also being diverted from other "higher"
uses such as recreation or tourism, drinking water supplies, and other
less intrusive commercial opportunities.
In addition, the
habitat of many animal and plant species can be destroyed during the construction
of and continued operation of large fossil and nuclear power plants. These
same facilities represent challenges to maintaining a sense of aesthetics
in scenic environments.
operation of hydropower facilities can also have negative impacts on water
quality. By slowing the river's flow, most dams increase water temperatures.
Other dams decrease temperatures by releasing cooled water from the reservoir
bottom. Fish and other species are sensitive to these temperature irregularities,
which often destroy native populations. These temperature changes, when
combined with water stagnation, may also lead to the accumulation of decaying
materials in the reservoir and a corresponding loss of oxygen, which then
increases substances toxic to aquatic wildlife in the reservoir. And when
this oxygen-deprived water is released from behind the dam, it can kill
fish and vegetation downstream. Alternatively, water falling over spillways
to spin turbines to generate electricity can super-saturate the water
with gases from the surrounding air. The gas bubbles, which are absorbed
into fish tissue, may cause damage and ultimately kill the fish. Crystal-clear
rivers can also degrade quickly when water is impounded behind a man-made
dam, accumulating sediment and silt.
Hydropower dams also
impact fish and wildlife habitat. Construction of a dam converts river
habitat into a lake-like reservoir. This often eliminates native populations
of fish and other wildlife. Warm, slow moving reservoirs also often favor
predators of naturally occurring species. It has been argued that reservoirs
can enhance waterfowl habitat, but such artificially created habitats
may be of considerably lower quality than the naturally evolved and undisturbed
river systems. Peaking power operations can also cause dramatic changes
in reservoir water levels -- often up to 40 feet -- that degrade shorelines
and disturb fisheries, waterfowl, and bottom-dwelling organisms.
consumer electricity choice address water quality problems?
Water quality impacts
vary - sometime significantly - from electricity generating technology
to technology. Many renewable energy technologies such as wind and solar
photovoltaic technology produce electricity without generating any waste
effluent released into waterways or without relying upon any cooling water.
By contrast, thermal power plants that run on coal and other fossil fuels
introduce a myriad of chemicals for maintenance or operational purposes,
and through combustion, liberate other chemicals from the fuel that wind
up in the power plant's discharge. Nuclear power plants consume even more
water than fossil fuel facilities because of the additional cooling requirements
of reactor cores and can have major impacts on marine environments.
Consumers can help
maintain the sustainability of rivers and streams, lakes and oceans, by
ensuring that their power comes from low impact and renewable sources
that do not rely upon water for cooling. Some renewable resources, such
as solar thermal facilities or geothermal power plants may require cooling
water and therefore may have more of an impact than those other renewable
sources that lack any need for water cooling. Most renewable resources,
however, are smaller than coal and nuclear power plants and therefore
their negative impacts on water bodies are considerably less.
American Rivers http://www.americanrivers.org
Low Impact Hydropower Institute http://www.lowimpacthydro.org