Water Quality

Rural Pollution


Phosphate is the naturally occurring form of phosphorus. Phosphorus is one of the most abundant elements on Earth and it is essential for all plant and animal growth. It is highly reactive therefore, generally occurs bound to soil particles or the soil organic matter.  It enters water primarily in combination with soil particles where it becomes available for plant growth.

Mineral fertilisers account for approximately 80% of phosphates used worldwide, while 12% occurs from detergents and the rest from animal feeds. Phosphates are often the limiting nutrient for plant growth due to low availability in soils.  Fertilisers are applied to increase the abundance of available phosphorus for plant growth. It is estimated that 50% of phosphorus entering water course comes from Agriculture with the other major source coming from Sewage Treatment. As phosphorus is bound to sediment the major loss is through surface run-off on cultivated land during high rainfall or flood events.

High levels of phosphates in water course encourages the growth of algae (algal bloom) and other aquatic plants. Following this, overcrowding occurs and plants compete for sunlight, space and oxygen. This is also know as eutrophication.


Nitrates like phosphorous are a vital component for all living things. In animals, they form part of protein and DNA found in cells, they get nitrogen from eating plants and other animals. Plants also require nitrogen to live and grow, the get there nitrogen by absorbing it from water and soil.

Nitrate are  naturally occurring, all aquatic organisms create waste and aquatic plants and organisms eventually die.  This creates ammonia, bacteria in the water changes this ammonia to produce nitrite which is then converted by other bacteria to nitrate. Nitrates (NO3-)  are formed by combining oxygen and nitrogen. Nitrates also come from the earth.  Soil contains organic matter, which contains nitrogen compounds.  Just like the ammonia in water, these nitrogen compounds in the soil are converted by bacteria into nitrates.

Excessive nitrate levels found in water course could come from human intervention. Agriculture is a high source of nitrate due to it being applied to crops to encourage plant growth. In addition, sewage treatment works and domestic application can also be a source of nitrates. Just like phosphorus, nitrates can run-off the surface during high rainfall and flood events, entering water course. Like phosphorous, nitrates can also lead to eutrophication and enrichment of water course. In addition, nitrates can also have adverse effects on human life. Nitrates can interfere with the ability of our red blood cells to carry oxygen and in infants are more at risk of nitrate poisoning than older children or adults. Therefore it is important to reduce nitrate levels in water course so that it is safe to drink.

Septic Tanks

Septic tanks are household sewage treatment systems. They are often found in rural areas that are not connected main sewage. Well maintained septic tanks can adequately deal with household wastewater. however, if poorly maintained they could be churning out untreated sewage, which causes surface water and groundwater contamination.
This poses dangers to drinking water – spreading disease in humans and animals – as well as damaging the environment. You could be releasing these bacteria, viruses and toxic chemicals to local streams, rivers, lakes and seas. These could harm people, increasing the chances of infectious diseases such as eye and ear infections, acute gastrointestinal illness and hepatitis. They’re also harmful to local wildlife, with pollutants killing native plants and aquatic species.

To find out more information, please check out our campaign: Call of Nature Yorkshire 

Urban Pollution

Sewage Treatment Works

Wastewater is treated to remove pollutants  and contaminants. Wastewater treatment is a process to improve and clean water, removing some or all of the contaminants, making it suitable to discharge back to the environment. Discharging treated water could be via surface water, such as rivers or the ocean, or to groundwater.

Sewage treatment works are increasingly put under pressure due to high pollutant loads as well as increasing populations. Area’s that have a high tourist population are often most notably effected as sewage treatment works are designed for resident populations and not for increased populations during busy periods. Therefore, sometimes sewage treatment works can fail and release pollutants back into water course. This can include, phosphates, nitrates and coliform bacteria.

Road Run-Off

A high proportion of road run off can enter streams and water courses without ever flowing through pipes, sewers, treatment plants or stormwater outfall structures. Such wastewater sources are also known as non point source pollution.

It often occurs when precipitation falls on urban environments, picking up pollutants and depositing them into surface waters or introduces them into groundwater. The water carries with it all the wastes and chemicals from buildings, streets, roads and construction sites; salts, oils, gasoline and other chemicals from motor vehicles. These chemicals can all have an effect on aquatic life as well as treating drinking water standards and putting pressure on water treatment systems.


Road and surface water drains are designed to carry only rainwater, usually to the nearest watercourse. Unfortunately, this is often not fully understood which can lead to engine oil, cooking oil, paints, chemical wastes, detergents and even litter to enter these drains and consequently watercourse which can cause pollution These pollutions can range from the creation of an eyesore to the killing of fish and wildlife.

Pollution is also caused by misconnections. Misconnected properties let the foul waste from toilets, washing machines, dishwashers, showers, baths and sinks to enter surface water drains. Instead these wastes must go to a sewage treatment works through the foul sewer.

The Yellow Fish Campaign is a initiative promoting the slogan; “Only Rain Down the Drain”. This campaign is an interactive and enjoyable way of spreading the message. If you see a Yellow Fish on a drain cover, it means that this is a surface water drain and anything entering goes straight to a watercourse.