Diffuse water pollution is caused by the combined effect of a large number of small sources of pollution. Usually rainfall carries the pollution into watercourses or into ground waters.
In the UK diffuse pollution affects the quality of more streams, rivers, lakes, lochs, estuaries and coastal waters than any other source of water pollution.
Diffuse pollution affects both rural and urban areas.
Causes of diffuse pollution in rural areas
Store and handle materials such as fertilisers, pesticides, silage liquor, oil and other chemicals carefully to avoid causing pollution through leaks or spills.
If your business manages fields or forestry, then run-off from your land may be spreading pollution, such as:
- nitrogen and phosphorous from fertilisers
- faecal pathogens from your livestock
- soil particles from cultivated land
- pesticides and animal medicines
- organic material such as slurries, sewage sludge and manures.
Industry can be a source of diffuse water pollution in rural areas which can come from:
- contaminated land
- silt and dust from mining and quarrying
- drainage from disused mines
- chemicals and oil from minor spills and leaks
- incorrect disposal of wastes to surface water drains
- incorrect waste pipe connections
- silt and dust from construction and demolition.
You can reduce the risk of diffuse pollution in rural areas by using proven land management practices.
Causes of diffuse pollution in urban areas
Transport and car parks can be a source of pollutants such as:
- oil and brake fluid from leaks and car maintenance
- rubber and heavy metals from wear on tyres and brakes
- polycyclic aromatic hydrocarbons (PAHs) and unburned fuel from exhaust emissions
- salt during winter months
- detergents and grease from vehicle cleaning.
Even rainwater run-off from your car parks can contain residues of fuel and oils which could cause pollution if you do not manage it properly.
Industry can be a source of diffuse water pollution in urban areas which can come from:
- contaminated land
- chemicals and oil from minor spills and leaks
- incorrect disposal of wastes to surface water drains
- incorrect or faulty waste pipe connections
- silt and dust from construction and demolition.
Other sources of diffuse water pollution in urban areas are:
- heavy metals and pollution from chimneys washed from roofs
- animal faeces, for example from dogs and birds.
You can control diffuse pollution from lightly contaminated run-off by using sustainable drainage systems (SUDS).
