Diffuse Pollution comprises true non point source contamination and pollution arising from a multiplicity of dispersed, often individually minor, point sources. Examples of true non point sources are sheet run off from fields or seepage of nutrients from soil into ground water. Examples of minor point sources are field drains or surface water drains in urban areas. Diffuse sources are often individually minor, but collectively significant.

One of the current areas of concern is the problem contamination of water bodies of potentially harmful bacteria from human and animal waste, the presence of which is assessed by measuring Faecal Indicator Organisms or FIO’s. FIO’s can come from a number of different sources in both urban and rural areas and can cause illness in both humans and animals. This problem is being addressed mainly to ensure compliance with various EU directives such as the Bathing waters and Shellfisheries directives


The Problems

• Diffuse pollution can come from many different sources. Pollution sources are sometimes uniformly dispersed, but are often aggregated within a catchment. Diffuse pollution is closely linked to land use; for example the application of fertiliser to farmland, or forestry plantations; livestock stocking rates on pastureland; handling and transport of oil, chemicals, raw materials and products through catchments, but especially on industrial and commercial estates. Some diffuse pollutants of watercourses are not pollutants at all if not transported from the land, soil being the most obvious example. Problems occur in both the Urban and Rural environments

The Solutions

• There is no single solution to tackling diffuse pollution. The most effective approach is the treatment train concept or Best Management Practises, which rely on a range of measures from changes in house keeping and behaviour, through source control, site control and regional control to reduce and alleviate Diffuse pollution impacts. Some of the types of activities and developments involved in controlling diffuse pollution can be seen in the Urban and Diffuse Solutions pages.
  
  SEPA is currently researching way of controlling diffuse pollution and is involved in a number of projects aimed at finding the best solutions. Research Work.

Problems - Rural

Poaching is caused by livestock having unrestricted access to wet areas which then become cut up and eroded through trampling, leading to muddied water and increased sedimentation. Livestock can also cause problems when faecal pathogens enter the watercourse, and can also suffer increased rates of disease through standing in and drinking from dirty water.
	Spraying causes problems when chemicals being sprayed such as pesticides and herbicides find their way into watercourses from spray drift, which can also affect hedgerows and other habitats bordering the sprayed area. Pesticides especially can have serious effects on aquatic biota.
Inappropriate cultivation can cause problems by increasing soil erosion on the effected land. Ploughing on steep land, or at times of the year when there is a high rainfall can greatly increase runoff and soil erosion

	Car parks can represent a large runoff producing area in the urban environment, which is often contaminated with oil and petrol as well as with toxic metals from cars. Traditionally all of this pollution would be washed off into drains, polluting nearby watercourses
Industrial yards will often deal with polluting substances on a larger scale than car parks which makes them a potentially even greater producer of diffuse pollution.
	Oil is the cause of more than 20% of Scottish water pollution incidents. It can have serious affects on the fauna and flora of aquatic systems. Much of it comes from diffuse sources. Visit SEPA's Oil Care Campaign Website for more details
Runoff from roads can carry with it many pollutants, including grit and dirt which is often contaminated with toxic metals from vehicle break linings. Salt from winter gritting can also act as a pollutant, as can oil which has leaked from vehicles

Best Management Practises (BMP's) are ways of managing land or processes in the best possible manner for the benefit of the environment.

Rural BMP's: a Four point Focus

		Fencing can be used to stop livestock reaching streams and ponds which prevents erosion and poaching, reducing the amount of sediment which gets into watercourses. This can also protect the important riparian habitat from degradation
Buffer strips help to stop runoff from agricultural land reaching watercourses. They can help reduce pollution from soil erosion, pesticides and fertilizers, and can also act as a source of beneficial insects and other wildlife.
		Contour ploughing is a relatively simple land management tool which can be employed to reduce soil erosion on sloping land. By following the contours of the land, runoff can be minimised keeping more soil on the land and out of streams and burns.

Solutions - Urban

Treatment Train Concept
	Behaviour Housekeeping Source Site Regional

Effective control of urban diffuse pollution is likely to require the following:

1. SUDS retro-fits for worst local source areas of contamination of surface water drainage. Those areas are likely to be industrial estates and other commercial areas.

2. SUDS retro-fits are most likely to be effective if a treatment train approach is used. This requires a public or other agency that can purchase or otherwise obtain landuse rights in the drainage catchment area to provide or require site or local controls (such as detention basins or swales).

3. management of risks of accidental spills of oil and chemicals in commercial and industrial areas by enforceable housekeeping regulations.

4. Traffic control (reduction) measures to minimise pollution loads on urban watercourses and drainage systems.

5. Public support and awareness raising to curtail individual polluting practices (in the workplace and at home).

Porous blocks can be used to reduce runoff from paved areas. This reduces the pollutants load entering watercourses, and allows some pollutants to be broken down on site. Porous Blocks are not sealed into the ground but rest on a bed of course sand which allows water falling on them to trickle down between the blocks and soak away into the ground. Alternatively the water can be stored in underground tanks and used on site. Porous asphalt has also been developed.
	The DEX site is a development area to the East of Dunfermline which has become a demonstration site for the implementation of Sustainable Urban Drainage Systems (SUDS) in Scotland.
Good housekeeping can reduce much of the diffuse pollution from industrial areas by preventing it from getting into the environment. Good housekeeping measures include keeping oil in sealed containers, making sure that clean and dirty water are kept separate and disposing of chemicals in the correct manner.