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Water pollution

What did you use water for this morning - a shower, cooking breakfast, washing the breakfast dishes, brushing your teeth or flushing the toilet?

All of the sewage from your house will eventually make its way back into the rivers, lakes and the sea.

Did you or any other members of your family read a newspaper, use packaged products or eat some fresh fruit? All of these things, along with most other things that you use or eat, also produce sewage in their production.

The sewage from houses, schools, office buildings, farms and factories contains all kinds of chemicals and materials that are not naturally found in our waterways. Some of these chemicals are poisonous and can be dangerous, even in very small amounts. Others, such as human wastes, are not poisonous but are produced in such great quantities that natural systems simply can't cope. As a result, sewage must be purified in some way before it is released into the environment.

Water pollution happens when sewage is not effectively treated before it is released into the environment. This can happen in many ways, some are accidental, but others are deliberate. 

Sources of water pollution

Most people are affected in some way by water pollution and we have all read stories of dead fish and polluted rivers and beaches. However, fewer people are aware of the many sources of water pollution. 


Many of the problems faced by sewage treatment plants begin with the material people tip down the drain or flush down the toilet at home. Treatment plants are not capable of treating many of these wastes and some pass through the system untreated.

For example, Australian families use vast numbers of feminine hygiene products each year. Although many of these products are disposed of correctly (in household rubbish), those that are flushed down the toilet can cause problems by blocking screens at a treatment plant.

Industry, offices and schools

As with household sources of water pollution, industry, offices and schools can be the source of a whole range of materials and chemicals that are carelessly tipped down the drain. The thoughtless disposal of toxic chemicals is a serious problem because these chemicals can cause pollution, even if they are in small quantities.

Many industries are also allowed to dispose of materials or chemicals into the sewerage system. However, they must do so under strict guidelines controlled by the water authorities responsible for the treatment of sewage.


Occasionally pumping stations break down, sewer pipes break or become blocked, and untreated sewage is released. Luckily these problems are few and far between and are generally a minor source of water pollution.

Treatment plants

Sewage treatment plants may also break down. However, they are generally designed with enough back-up systems to prevent any major water pollution problems. Modern treatment plants treat sewage to a stage where it is safe to release back into the environment and there is a growing use of recycled sewage.

Septic tanks

Septic tanks treat sewage on site and are sometimes responsible for the release of untreated sewage (raw sewage), especially after heavy rain. As septic tanks are not as effective as reticulated sewerage systems, they are gradually being replaced as reticulated sewerage systems are expanded.

Illegal dumping

As well as carelessly, or accidentally putting waste chemicals and materials into the sewage system, some industries or people deliberately dump wastes into the sewers or directly into the environment. This is done to avoid the high cost of treating these wastes properly.

Stormwater drains

Rain water that falls on our houses and roads is carried away in a system of pipes that is separate from the sewerage system that carries sewage. These stormwater drains also collect any litter or other material, including animal droppings, that lies around our streets. All of this rubbish is generally carried straight into rivers or out to the sea by the stormwater drains.

Because stormwater is not treated, this system is responsible for carrying much of the rubbish found along our streams and beaches. Stormwater drains are also commonly responsible for carrying either deliberately or accidentally spilled toxic chemicals, oils and other materials into the sea.


Most farmers use a wide range of fertilisers, herbicides, insecticides and other chemicals on their crops. Scientists are only just beginning to realise how much of these chemicals are washed into creeks and drains and on into the sea.

Types of water pollution

There are many forms of water pollution. Here are some of the common ones that you often read about:

  • Escherichia coli (E. coli)
    These bacteria (microorganisms) come from animal (mainly human) wastes and provide definite evidence of faecal pollution. The level of E. coli in water is used as a guide to the amount of animal or human wastes in the water and may indicate the presence of pathogenic bacteria.
  • Toxic chemicals
    Many chemicals used in industry are poisonous to wildlife (and humans). Dioxin and heavy metals, such as mercury, are well known examples of the thousands of toxic chemicals produced by industry. Even in very small quantities, toxic chemicals are a very serious cause of water pollution.
  • Oil
    All kinds of oil ends up in our waterways through accidental spills or illegal dumping. Because oil floats on the surface of water, any oil spill can be disastrous for marine life.
  • Plastics
    Australians use around 3.9 billion plastic bags a year. Plastic bags and other plastic items are very useful around the home, but can also have a disastrous effect on marine life. A great deal of this plastic pollution finds its way into the sea through stormwater drains.

Who's responsible?

Whenever there is a problem with water pollution it is important to know who is the responsible authority.

Melbourne Water

Melbourne Water is responsible for large stormwater drains and for rivers and creeks. They also undertake a monitoring program to measure water quality in rivers and streams.

Local municipal councils

Local Councils are responsible for small stormwater drains and they also manage septic tanks.

Environment Protection Authority

The EPA is responsible for setting environmental standards and helping companies and individuals achieve these standards. They can do this with incentives or penalties for those who breach environmental laws.