Water pollution affects plants and organisms living in these bodies of water. In almost all cases the effect is damaging not only to individual species and populations, but also to the natural biological communities.
Water pollution is a major global problem which requires ongoing evaluation and revision of water resource policy at all levels (international down to individual aquifers and wells). It has been suggested that it is the leading worldwide cause of deaths and diseases, and that it accounts for the deaths of more than 14,000 people daily. An estimated of 580 people in India die of water pollution related illness every day. Around 90% the water in the cities of China is polluted, and as of 2007, half a billion Chinese had no access to safe drinking water. In addition to the acute problems of water pollution in developing countries, developed countries continue to struggle with pollution problems as well. In the most recent national report on water quality in the United States, 45 percent of assessed stream miles, 47% of assessed lake acres, and 32 percent of assessed bays and estuarine square miles were classified as polluted. The head of Chinas national development agency in 2007 said 1/4th the length of China's seven main rivers were so poisoned the water harmed the skin.
Water is typically referred to as polluted when it is impaired by anthropogenic contaminants and either does not support a human use, such as drinking water, or undergoes a marked shift in its ability to support its constituent biotic communities, such as fish. Natural phenomena such as volcanoes, algae blooms, storms, and earthquakes also cause major changes in water quality and the ecological status of water.
Category
Surface water and groundwater have
often been studied and managed as separate resources, although they are
interrelated. Surface water seeps through the soil and
becomes groundwater. Conversely, groundwater can also feed surface water
sources. Sources of surface water pollution are generally grouped into two
categories based on their origin.
Point sources
Point
source water pollution
refers to contaminants that enter a waterway from a single, identifiable
source, such as a pipe or ditch.
Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain. The U.S. Clean Water Act (CWA) defines point source for regulatory enforcement purposes. The CWA definition of point source was
amended in 1987 to include municipal storm sewer systems, as well as industrial
stormwater, such as from construction sites.
Nonpoint sources
Nonpoint
source pollution refers
to diffuse contamination that does not originate from a single discrete source.
NPS pollution is often the cumulative effect of small amounts of contaminants
gathered from a large area. A common example is the leaching out of nitrogen compounds from fertilized agricultural
lands. Nutrient runoff in stormwater from "sheet flow" over an agricultural
field or a forest are
also cited as examples of NPS pollution.Contaminated storm water washed off of parking lots, roads and highways, called urban runoff, is sometimes included under the category of NPS pollution. However, this runoff is typically channeled into storm drain systems and discharged through pipes to local surface waters, and is a point source.
Groundwater pollution
Interactions between groundwater and surface water are complex.
Consequently, groundwater pollution, sometimes referred to as groundwater
contamination, is not as easily classified as surface water pollution. By its very nature, groundwater aquifers are susceptible to contamination from
sources that may not directly affect surface water bodies, and the distinction
of point vs. non-point source may be irrelevant. A spill or ongoing releases of
chemical or radionuclide contaminants into soil (located away
from a surface water body) may not create point source or non-point source
pollution, but can contaminate the aquifer below, defined as a toxin plume. The movement of the plume, called a
plume front, may be analyzed through a hydrological
transport model or groundwater model. Analysis of groundwater contamination
may focus on the soil characteristics and site geology, hydrogeology, hydrology, and the nature of the contaminants.
Causes
The specific contaminants
leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical or sensory changes such as
elevated temperature and discoloration. While many of the chemicals and
substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration is often the key in determining what is
a natural component of water, and what is a contaminant. High concentrations of
naturally occurring substances can have negative impacts on aquatic flora and
fauna.Oxygen-depleting substances may be natural materials, such as plant matter (e.g. leaves and grass) as well as man-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.
Many of the chemical substances are toxic. Pathogens can produce waterborne diseases in either human or animal hosts. Alteration of water's physical chemistry includes acidity (change in pH), electrical conductivity, temperature, and eutrophication. Eutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases in the primary productivity of the ecosystem. Depending on the degree of eutrophication, subsequent negative environmental effects such as anoxia (oxygen depletion) and severe reductions in water quality may occur, affecting fish and other animal populations.
Pathogens
Disease-causing microorganisms are referred to as pathogens. Although the vast majority of bacteria
are harmless or beneficial, a few pathogenic bacteria can cause disease. Coliform bacteria are a commonly used bacterial
indicator of water
pollution, although not an actual cause of disease. Other microorganisms sometimes found in surface waters which
have caused human health problems include:- Burkholderia pseudomallei
- Cryptosporidium parvum
- Giardia lamblia
- Salmonella
- Novovirus and other viruses
- Parasitic worms (helminths).
Pathogen discharges may also be caused by poorly managed livestock operations.
Causes and other contaminants
Contaminants may include organic and inorganic substances.Organic water pollutants include:
- Detergents
- Disinfection by-products found in chemically disinfected drinking water, such as chloroform
- Food processing waste, which can include oxygen-demanding substances, fats and grease
- Insecticides and herbicides, a huge range of organohalides and other chemical compounds
- Petroleum hydrocarbons, including fuels (gasoline, diesel fuel, jet fuels, and fuel oil) and lubricants (motor oil), and fuel combustion byproducts, from stormwater runoff
- Tree and bush debris from logging operations
- Volatile organic compounds (VOCs), such as industrial solvents, from improper storage.
- Chlorinated solvents, which are dense non-aqueous phase liquids (DNAPLs), may fall to the bottom of reservoirs, since they don't mix well with water and are denser.
- Perchlorate
- Various chemical compounds found in personal hygiene and cosmetic products
- Drug pollution involving pharmaceutical drugs and their metabolites
- Acidity caused by industrial discharges (especially sulfur dioxide from power plants)
- Ammonia from food processing waste
- Chemical waste as industrial by-products
- Fertilizers containing nutrients--nitrates and phosphates—which are found in stormwater runoff from agriculture, as well as commercial and residential use
- Heavy metals from motor vehicles (via urban stormwater runoff) and acid mine drainage
- Silt (sediment) in runoff from construction sites, logging, slash and burn practices or land clearing sites.
- Trash or garbage (e.g. paper, plastic, or food waste) discarded by people on the ground, along with accidental or intentional dumping of rubbish, that are washed by rainfall into storm drains and eventually discharged into surface waters
- Nurdles, small ubiquitous waterborne plastic pellets
- Shipwrecks, large derelict ships.

The Vermont Yankee Nuclear Power Plant discharges heated water to the Connecticut River.
Thermal pollution
Thermal pollution is the rise or
fall in the temperature of a natural body of water caused by human influence.
Thermal pollution, unlike chemical pollution, results in a change in the
physical properties of water. A common cause of thermal pollution is the use of
water as a coolant by power plants and industrial manufacturers. Elevated
water temperatures decreases oxygen levels, which can kill fish, and can alter food chain composition, reduce species biodiversity, and foster invasion by new thermophilic species.[19][20][21] Urban runoff may also elevate
temperature in surface waters.Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers.
Transport and chemical reactions of water pollutants
Most water pollutants are
eventually carried by rivers into the oceans. In some areas of the world the
influence can be traced hundred miles from the mouth by studies using hydrology
transport models.
Advanced computer
models such as SWMM
or the DSSAM Model have been used in many locations
worldwide to examine the fate of pollutants in aquatic systems. Indicator filter feeding species such as copepods have also been used to study pollutant
fates in the New York
Bight, for example. The
highest toxin loads are not directly at the mouth of the Hudson River, but 100 kilometers south, since several
days are required for incorporation into planktonic tissue. The Hudson discharge flows south
along the coast due to coriolis force. Further south then are areas of oxygen
depletion, caused by
chemicals using up oxygen and by algae blooms, caused by excess nutrients from algal cell death and decomposition.
Fish and shellfish kills have been reported, because toxins
climb the food chain after small fish consume copepods, then large fish eat smaller fish, etc.
Each successive step up the food chain causes a stepwise concentration of
pollutants such as heavy metals (e.g. mercury) and persistent
organic pollutants such
as DDT. This is known as biomagnification, which is occasionally
used interchangeably with bioaccumulation.
Measurement
Water pollution may be analyzed
through several broad categories of methods: physical, chemical and biological.
Most involve collection of samples, followed by specialized analytical tests.
Some methods may be conducted in situ, without sampling, such as temperature.
Government agencies and research organizations have published standardized,
validated analytical test methods to facilitate the comparability of results
from disparate testing events.
Sampling
Sampling of water for physical
or chemical testing can be done by several methods, depending on the accuracy
needed and the characteristics of the contaminant. Many contamination events
are sharply restricted in time, most commonly in association with rain events.
For this reason "grab" samples are often inadequate for fully
quantifying contaminant levels. Scientists gathering this type of data often
employ auto-sampler devices that pump increments of water at either time or discharge intervals.Sampling for biological testing involves collection of plants and/or animals from the surface water body. Depending on the type of assessment, the organisms may be identified for biosurveys (population counts) and returned to the water body, or they may be dissected for bioassays to determine toxicity.
Physical testing
Common physical tests of water
include temperature, solids concentrations (e.g., total
suspended solids (TSS))
and turbidity.
Chemical testing
Water samples may be examined
using the principles of analytical
chemistry. Many
published test methods are available for both organic and inorganic compounds.
Frequently used methods include pH, biochemical
oxygen demand (BOD),chemical
oxygen demand (COD), nutrients (nitrate and phosphorus compounds), metals (including copper, zinc,
cadmium, lead and mercury), oil and grease, total petroleum
hydrocarbons (TPH), and pesticides.
Biological testing
Biological testing involves the
use of plant, animal, and/or microbial indicators to monitor the health of an aquatic ecosystem. They are any biological species or group of species whose function,
population, or status can reveal what degree of ecosystem or environmental
integrity is present. One example of a group of bioindicators
are the copepods and other small water crustaceans that are present in many water bodies.
Such organisms can be monitored for changes (biochemical, physiological, or
behavioural) that may indicate a problem within their ecosystem.
Control of pollution
Decisions on the type and degree
of treatment and control of wastes, and the disposal and use of adequately
treated wastewater, must be based considering all the technical factors of each
drainage basin, in order to prevent any further contamination or harm to the
environment.
Domestic sewage
Domestic sewage is typically
99.9 percent water with 0.1 percent pollutants. Although found in low
concentrations, these pollutants pose risk on a large scale. In urban areas, domestic sewage is
typically treated by centralized sewage treatment plants. Well-designed and
operated systems (i.e., secondary treatment or better) can remove 90 percent or
more of these pollutants. Some plants have additional systems to remove
nutrients and pathogens. Most municipal plants are not specifically designed to
treat toxic pollutants found in industrial wastewater.Cities with sanitary sewer overflows or combined sewer overflows employ one or more engineering approaches to reduce discharges of untreated sewage, including:
- utilizing a green infrastructure approach to improve stormwater management capacity throughout the system, and reduce the hydraulic overloading of the treatment plant
- repair and replacement of leaking and malfunctioning equipment
- increasing overall hydraulic capacity of the sewage collection system (often a very expensive option).
Industrial wastewater
Some industrial facilities
generate ordinary domestic sewage that can be treated by municipal facilities.
Industries that generate wastewater with high concentrations of conventional
pollutants (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile
organic compounds) or other nonconventional pollutants such as ammonia, need
specialized treatment systems. Some of these facilities can install a
pre-treatment system to remove the toxic components, and then send the
partially treated wastewater to the municipal system. Industries generating
large volumes of wastewater typically operate their own complete on-site
treatment systems.Some industries have been successful at redesigning their manufacturing processes to reduce or eliminate pollutants, through a process called pollution prevention. Heated water generated by power plants or manufacturing plants may be controlled with:
- cooling ponds, man-made bodies of water designed for cooling by evaporation, convection, and radiation
- cooling towers, which transfer waste heat to the atmosphere through evaporation and/or heat transfer
- cogeneration, a process where waste heat is recycled for domestic and/or industrial heating purposes.
Agricultural wastewater
Nonpoint source controlsSediment (loose soil) washed off fields is the largest source of agricultural pollution in the United States.Farmers may utilize erosion controls to reduce runoff flows and retain soil on their fields. Common techniques include contour plowing, crop mulching, crop rotation, planting perennial crops and installing riparian buffers.
Nutrients (nitrogen and phosphorus) are typically applied to farmland as commercial fertilizer; animal manure; or spraying of municipal or industrial wastewater (effluent) or sludge. Nutrients may also enter runoff from crop residues, irrigation water, wildlife, and atmospheric deposition.Farmers can develop and implement nutrient management plans to reduce excess application of nutrients and reduce the potential for nutrient pollution.
To minimize pesticide impacts, farmers may use Integrated Pest Management (IPM) techniques (which can include biological pest control) to maintain control over pests, reduce reliance on chemical pesticides, and protect water quality.
Point source wastewater treatment
Farms with large livestock and poultry operations, such as factory farms, are called concentrated animal feeding operations or feedlots in the US and are being subject to increasing government regulation. Animal slurries are usually treated by containment in anaerobic lagoons before disposal by spray or trickle application to grassland. Constructed wetlands are sometimes used to facilitate treatment of animal wastes. Some animal slurries are treated by mixing with straw and composted at high temperature to produce a bacteriologically sterile and friable manure for soil improvement.
Construction site stormwater
Sediment from construction sites
is managed by installation of:- erosion controls, such as mulching and hydroseeding, and
- sediment controls, such as sediment basins and silt fences.
- spill prevention and control plans, and
- specially designed containers (e.g. for concrete washout) and structures such as overflow controls and diversion berms.
Urban runoff (stormwater)
Effective control of urban
runoff involves reducing the velocity and flow of stormwater, as well as
reducing pollutant discharges. Local governments use a variety of stormwater
management techniques to reduce the effects of urban runoff. These techniques,
called best management practices (BMPs) in the U.S., may focus on water quantity control, while
others focus on improving water quality, and some perform both functions.Pollution prevention practices include low-impact development techniques, installation of green roofs and improved chemical handling (e.g. management of motor fuels & oil, fertilizers and pesticides). Runoff mitigation systems include infiltration basins, bioretention systems, constructed wetlands, retention basins and similar devices.
Thermal pollution from runoff can be controlled by stormwater management facilities that absorb the runoff or direct it into groundwater, such as bioretention systems and infiltration basins. Retention basins tend to be less effective at reducing temperature, as the water may be heated by the sun before being discharged to a receiving stream.
SUBSCRIBERS - ( LINKS) :FOLLOW / REF / 2 /
findleverage.blogspot.com
Krkz77@yahoo.com
+234-81-83195664
No comments:
Post a Comment