Eutrophication is the
artificial nutrient enrichment of an aquatic system with organic material or
inorganic nutrients, causing an excessive growth of aquatic plant life.
Eutrophication is mostly caused by the input of untreated sewage into the river
or lake, the leaching of inorganic fertilisers from agricultural lands and the
discharging of animal waste from farmlands into the lakes, rivers or ponds. This
process induces growth of plants and algae. This results in a population
explosion known as an algal bloom. Therefore, eutrophication may cause the
oxygen level in the water decreases and danger the other aquatic organism life.
Eutrophication is a vital environmental problem since it
causes in a change of water quality and is affect most of the lakes in the
world. In fact, all water bodies are confronted with a slow eutrophication
process, but in recent decades has undergone a very rapid progression due to
the various activities by mankind. This process continuously increase in the amount
of nutrients, especially phosphorus and nitrogen until it exceeds the natural
constituent of the water body.
Causes of eutrophication
Eutrophication is mostly cause by the leaching of the
fertilisers from the farming area or the agricultural lands. When the
fertilisers at the land are rinsed off by the rain water, they runoff into
nearby rivers, lakes, ocean and even the groundwater. The algae and other
aquatic plant absorb the nutrients and their photosynthesis activity increased.
This may result in the dense growth of algae and other aquatic plants in the
In addition, the untreated sewage is also one of the
factor that causes eutrophication. Sewage such as human waste from housing
area, chemicals and harmful liquids from industrial area, solid and liquid from
dumping area that are all haven’t undergo sewage treatment are considered as
untreated sewage. In various developing countries, the sewage are illegally
discharged directly into the river that near the housing area or industrial
area. The waste are then travel along the river into the sea. The waste that
contain a lot of nutrients contributes to the growth of algae. A huge number of
aquatic animals have died because of the algal bloom causing the imbalance
Also, eutrophication can
be caused by the nature. After a lot of years, the lakes, ponds or river start
to accumulate large amount of sediments at the bottom. As the current of water
flow, it tends to wash off the excess nutrients at the land into the water.
These sediments are able to absorb large quantities of phosphorus and nitrogen.
And leading to eutrophication in the end.
The process of eutrophication
explosion of algae known as algal bloom. This is caused by excess nutrients
draining into ponds, rivers and lakes. The excessive growth of algae restricts
the penetration of sunlight into the water. So, the photosynthesis of other
aquatic plant is greatly reduced. Therefore, the oxygen level in the water
greatly decreases. The algae also grow faster than other organisms in the
water. As a result, most of the algae die without being consumed.
the other photosynthetic organisms die and organic material dead plant deposits
at the bottom of the water. Decomposing microorganisms especially aerobic
bacteria accumulates at the bottom at the lake, decomposing the dead plants,
grow rapidly and use up the oxygen in the deeper water. The microorganisms use
up the oxygen faster than it can be supplied. This resulting the biochemical
oxygen demand (B.O.D) increase as the oxygen level greatly decrease.
The extremely low level of oxygen kills
aquatic animals such as fish and shrimp and most of the aerobic bacteria will
not survive. In extreme cases, the water will becomes completely deoxygenated
as the oxygen level continue to drop. As this time, the anaerobic bacteria will
grow and release toxic gases such as hydrogen sulphide. At high B.O.D levels,
leeches and sludge worms may appear and grow rapidly as they are more tolerant
of lower concentration of dissolved oxygen.
What is Biochemical Oxygen Demand
Biochemical oxygen demand (BOD) is
the amount of dissolved oxygen needed by living organisms to oxidised organic
material that is present in a given water sample at certain temperature. There
are a few variables that are affecting the rate of oxygen consumption: pH,
temperature, the presence of certain kinds of microorganisms and the type of
inorganic and organic material in the water. The measurement of B.O.D is an
indication of the level of water pollution.
Higher level of consumers like fish eat some of the producer
like aquatic plants and the nutrients move up the food chain. When these
consumers die, microorganisms use oxygen to decompose the organic compounds.
So, when eutrophication occurs, the level of oxygen is very low because of the
algae blocking the sunlight to penetrate through the water and causes the
photosynthetic plants die. No further the oxygen can be produced, aerobic
organisms suffocate and die and oxygen is used to decompose the dead bodies. At
this point, the B.O.D level in the water is extremely high, therefore the water
is considered as polluted. The higher the B.O.D, the more rapidly the oxygen is
depleted, the more the water polluted.
is the main solution for eutrophication. Eutrophication is mainly begin from
the use of phosphate and nitrate-rich fertilisers. By practicing composting organic material such
as food residue by burying them in the backyard can actually solve the problem.
The nutrients in the food residue do not contain nitrates and phosphorus that
cause algae to grow, so when there is run-off, it does not cause
eutrophication. Same goes to agriculture land or farmland, if the farmers use
composting as fertiliser for their farms, there will be no run-off that contain
nitrates and phosphorus.
Tightening the laws and regulations against irresponsible
laws and regulations against polluter can control the process of
eutrophication. Irresponsible industries, farmers, residence that discharging
harmful material into the river, pond or lake should face a serious
consequences such as being fined or go to jail.
They should be blamed for their behaviour as they be responsible for the
entry of nutrients into the water system and cause eutrophication. The laws
should aim at enhancing high water quality standards and zero-tolerance to polluter.
With the support of policymakers, citizens, pollution regulatory authorities
and the government, it is easy to control eutrophication.
Reducing Sediment Addition
When extra soil get washed into the lake or stream bank,
erosion occurs. The extra soil particles will cause the water become cloudy and
deposit at the bottom of the lake. The soil sometimes contain nitrate and
phosphorus which contributes to algal bloom. Steps have to be taken to
stabilize the lakeshore or river bank. The most effective technique is
shoreline buffer of native plants.
Filtration of waste water
Wastewater treatment plants, also called sewage treatment
plants or water pollution control plants, remove most pollutants from waste water
from any combination of domestic, industrial, commercial or agricultural
activities, before it is released to local waterways. At the plants, physical
and biological processes closely duplicate how wetlands, rivers, streams and
lakes naturally purify water. Many processes in a wastewater treatment plant are designed
to mimic the natural treatment processes that occur in the environment. If not
overloaded, bacteria in the environment will consume organic contaminants,
although this will reduce the levels of oxygen in the water and may
significantly change the overall ecology of the receiving water. Thefore, the
numbers of disease-causing microorganisms are reduced by natural environmental
conditions such as predation or exposure to ultraviolet radiation.