It refer to the contamination of water which makes it unsuitable for drinking, washing and recreational activities.

There are 2 types of pollutions: 1)Freshwater pollution 2)Seawater pollution

Water pollution affects people, animals and plants and many aquatic plants and creatures are dying at alarming rate as a result.

Improper Disposal of Sewage
Sewage refers to waste matter that is carried away from homes and industries by sewers(pipes) for treatment or disposal. Sewage includes human waste, dirty water, and even toxic substance such as chemicals.

Sewage must be properly treated to remove toxins before it is discharge into the seas. However, not all places have sewage system. Some places also generate more sewage then their system can habdle, resulting in waste matter that is not treated before it is discharged. Moreover,certain substances such as detergents are non-biodegradable and cannot be removed. These sbstance are eventually discharged into the seas, thus polluting the water there.

Industrial sewage is usually more toxic than sewage from homes because it contains heavy metals such as lead and mercury. Many countries require industries to treat their waste matter even before it is released into the sewers.

















Occurence of Oil Spills
An oil Spill is the accidental release of oil into the seas and oceans by supertankers (very large crude oil carriers). Major oil spills are usually the result of accidents and they can cause much damage. Smaller oil spills (also called leaks) may result from oil rig operation, the painting and cleaning of ships, and the loading and unloading of cride oil.


















Use of Pesticides and fertilisers
Pesticides and fertilisers disturb balance of natural nutrients in the soil and cause water pollution when they are washed by rainwater into streams and rivers.

Effect on human health
The World Health Organization (WHO) estimates that anout 5 millions people suffer and die from illness related to contaminated water annually. Contaminated water has been linked to health problems such as diarrhoea, cholera and bilharzia (a disease caused by parasite worms in human bodies).

The poisons in pesticides and chemicals are passed on to people when they consumefish caught in polluted water. One of the world's worst water pollution disaters took place in Minamata Bay, japan, in the world 1950s when mercury waste was dumped by a chemical factory. People who ate the poisoned fish caught in the Bay suffered brain damage and paralysis. The Minamata Bay was only given the 'all clear' in 1997 when mercury levels in the surrounding seas where witin safe limits.

Endangering of marine life
Certain chemicals such as nitrates and phosphoruus are nutrients for plants. Nitrates are contained in fertilisers and hosphorus in detergents. When they enter the water, these chemicals speed up the growth of algae and floating plants such as water hyacinth. This process is known as eutrophication. these plants form a cover over the waste surface, preventing sunlight from reaching other plants in the water. They also deprive the plants and other marine life of oxygen.

A lack of oxygen also occurs when there is an oil leak. A thin layer of oil floating on the surface pf the water, called an oil slick, forms during an oil leak.  This blocks sunlight and oxygen from reaching plankton (minute plants and animals which are the food of fish) and other marine organisms and they eventually die from oxygen deprivation. As plankton and small fish form the base of the food chain, their scarcity may cause a chain reaction affecting other animals.


















Poisoning of Seabirds and Other Animals
Seabirds and other animals that are caught in an oil spill have a very slim chance of survival. Oil is sticky and holds feathers or fur together so that they can no longer insulate the animals. The animals may freeze to death as a result. The oil also prevents the aniamals from flying or swimming so they swallow the oil while trying to clean themselves.

High Economic Costs
Water pollution affects the fishing and tourism industries. Fewer fish are caught in pollutes waters. If the water is polluted by oil, fishing will not be possible for serval months even after the oil has been removed. It will take considerable time for the aquatic animals to multiply and gor their habitats to be rebuilt.

Most oil spills take place cose to the shore and around ports. When water near the beaches is polluted, tourists will stay away. This affects the tourism industry, especially in countries with beautiful beaches.

At individual level
As individuals, we can play a part to reduce pollution in our rivers,seas and coasts. We may not be able to prevent oil spills, but we can help reduce the amount of waste waterthat flows into the sewerage system bu using water wisely. We can refrain from leaving rubbish along the beaches or in ivers, We can also participate in projects to help clen up the waterways and beaches.What have you done to keep out waters clean?

The Government
Some governments also impose laws ans regulations to prosecute people and companies found guilty of polluting water. Oil-carrying ships and storage facilities are also carefully monitored and checked to prevent accidental oil dischargeds.

Another measure that can be taken at the national level is ensuring that adequate sewerage systems are in place. In Singapore, work has begun on a Deep Tunnel Sewerage System (DTSS) to treat the increasing amount of sewage more effectively.

Aim
Toensure the sustainability of our water supply - our ultimate aim is to be self- sufficient - and to manage water pollution.

Actions and Accomplishments
In order to ensure a suitabke supply of clean water, regular clean-up efforts are made to keep our water sources and waterways clean. The government has also pursued a programme of conserving our existing resources, maximising our water catchment areas and diversifing our water sources.

- The clean-up of the Singapore River and the Kallang Basin cost S$200 million and took 10years to complete. Today, the rivers are popular with tourists and loals for water sports and water spots competitions. The clean water has also enabled fish and prawns to return to the rivers.

- Water catchment areas are out-of-bounds for industries that may produce toxic chemical by-products.

- Industrial wastes are required to be treated before being discharged into the sewerage system.

- The Deep Tunnel Sewerage System (DTSS), when fully operational in 2008, will carry sewage from all existing sewers to two centralised water reclamation plants in Changi and Tuas, where it will be treated.

These measures ensure that the waters in our seas, rivers and reservoirs are all clean. Work has already begun to expand our catchment areas to two-thirds of the island, and that the successful operation of the desalination and NEWater plants has helped us to deversity our sources of water.