Water Pollution

There are different types of pollutants which can impact on life when added to water. Toxic materials such as mercury or arsenic are poisonous to life. Enrichment with nutrients from sewage or farm waste can encourage the growth of green algae. The algae use up oxygen in the water making life difficult for other forms of life for example salmon and trout.

The same organic wastes can harbour bacteria and microscopic life which spread diseases. Acid rain or acid run off from forest plantations can prevent water from holding scarce minerals needed by life in our rivers. Even something that appears harmless such as hot water, released by industry, can cause damage reducing the amount of oxygen dissolved in the water.


In the past many factories dumped their waste into rivers in the belief that dilution would solve the problem. This proved to be false with rivers unable to cope with the quantities received. Pollutants released included toxic waste, organic waste, detergents and hot water. Today the release of waste water from industry is strictly controlled by the EPA.

Large industries require a licence to release waste water and under the licence the local authorities monitor the water released. When reports of pollution are made by the public the incident is investigated with laboratory staff from the Local Authority testing the water being released and also water quality downstream.


Large plantations of coniferous forests can have an impact on the environment making local conditions more acidic. For this reason it is important to leave a gap between streams or rivers and a coniferous plantation. Good practice in forestry allows native trees to grow alongside our waterways.


Waste water from houses contains sewage and detergents, both of which can enrich water leading to algal blooms and the spread of diseases in the case of sewage. In the past most of the waste water from our homes went directly into our rivers and seas with little or no treatment. Sewage treatment has been upgraded for many of our towns and cities. Large cities such as Dublin now have Blue Flag beaches on their doorstep.

Further upgrading of sewage treatment is still needed in many places. The government is currently investing large sums of money to allow Local Authorities to upgrade waste water treatment. One challenge faced within these facilities is that people dispose of inappropriate waste such as plastic, flushing it down the toilet. These can cause blockages and must be screened out and removed in sewage plants.

Another issue is that many houses in rural areas use septic tanks. If they are not maintained and emptied they can become a serious source of pollution at local level.


Farms produce large amounts of organic waste. With proper management these wastes can be and are returned to the natural cycle of nutrients on the land. Poor management can lead to pollution, contamination of our drinking water and fish kills. Farmers are taking steps to manage this waste through good collection systems and care when spreading it on land.

Farm wastes cannot be spread near sources for water supply, rivers or lakes. There are also restrictions on the spreading of waste on land during the winter months and in periods of heavy rainfall. Thanks to the efforts of farmers our rivers and lakes are getting cleaner and we hear about fish kills less often.

Acid rain

Acid rain can also make water in our lakes and rivers more acidic. It is caused by air pollution from chimneys in large industries and power plants. Ireland has not been badly affected by Acid Rain due to the fresh winds blowing in off the Atlantic Ocean but forests in Central and Eastern Europe have suffered from Acid Rain. Controls on emissions to air and requirements to clean emissions with scrubbers in chimney stacks have reduced this form of pollution.


The mining industry can cause pollution through the release of toxic minerals such as arsenic or excessive amounts of minerals such as copper. In Ireland there is pollution of some rivers from historic sites that are no longer mined. The Avoca River is an example. Although mining in Avoca ceased in 1982 the river is still being polluted by minerals flushed out of the mines in the water.

Oil spills

Oil when spilled on the ground can often find its way into rivers and water. Oil spills occur due to accidents or as a result of poor storage of oil or waste oil. When an oil spill occurs leading to contamination of water it is a very visible and is usually quickly reported by an alert member of the public to the local authorities.

Laboratory staff will quickly launch an investigation of reported spills. The spill is assessed for its potential to contaminate drinking supplies and its impact on wildlife. The staff will investigate the source of pollution. Fines and clean up costs are issued once the source has been identified.

For further information visit The Environmental Protection Agency