Environmental guidance for your business in Northern Ireland & Scotland

Causes of water pollution

Causes of water pollution

Water pollution has damaging effects on the environment, humans, plants and animals. Pollution can occur if your business discharges substances into surface waters or groundwater without prior treatment or by accident, eg after a spill.

Key causes of pollution include:

  • spills or leaks from oil and chemical containers
  • trade effluent going into surface water drains instead of foul water drains, or straight into watercourses
  • removing too much water from surface waters and groundwater
  • run-off containing fertilisers and pesticides from farming into surface waters
  • run-off containing salt during winter months
  • silt and soil from construction sites and bank erosion on farms
  • wash waters and waste products
  • fuel spills
  • releases of hot water
  • spills of food products, eg dairy products and fruit juice.

If you pollute the water environment, you may be committing an offence.

Surface waters and groundwater are protected by a number of licensing regimes that prevent and control pollution from businesses. See the page in this guide on regulation that protects surface water and groundwater.

Point source and diffuse water pollution

Point source water pollution occurs where pollution comes from a specific, identifiable source, such as a sewage pipe or factory wastewater pipe.

Diffuse water pollution is caused by various sources, which are often hard to identify. Individual sources may be relatively small, but the combined effect of numerous sources can be damaging. Diffuse pollution has a greater impact on the water environment than any other source of pollution.

In rural areas, sources of diffuse water pollution include:

  • run-off from agricultural land containing substances including pest control products, animal medicines, slurry, sewage sludge and manure
  • run-off and leaching from contaminated land
  • silt and dust from mining, quarrying, construction and demolition
  • groundwater drainage discharging from disused mines
  • incorrect waste pipe connections.

In urban areas, sources of diffuse water pollution include:

  • pollutants from car parks and transport, such as oil and brake fluid, rubber and metal from tyres and brakes, exhaust emissions, and detergents and grease from vehicle cleaning
  • heavy metals and pollution washed from roofs
  • animal faeces, for example from dogs and birds.

You can prevent diffuse water pollution by:

  • using sustainable urban drainage systems (SUDS) to control diffuse pollution from lightly contaminated run-off
  • fencing off areas and establishing cover to prevent soil erosion
  • using silt traps, buffer strips and sand bags to prevent run-off containing sediment from polluting surface waters and groundwater
  • storing and handling hazardous materials carefully to prevent diffuse pollution from leaks and spills.

Further information

Septic tanks


Chemical storage

Oil Storage

Farming and Water Scotland

You can use the NetRegs e-learning tools to get a good overview of key issues. These tools are free to use and cover the essential points of each topic. They might be useful as a refresher course, or to make sure that staff have a good understanding of their environmental responsibilities.

  • Preventing pollution – a general guide
  • Duty of care
  • Sinks, drains and sewers
  • WEEE
  • Generating renewable energy

All are available at: NetRegs e-learning tools

Return to Preventing Water Pollution home page

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