All of us generate wastewater every day, from toilets, sinks, bathrooms, kitchen appliances and vehicle washing. Industry also produces a lot of wastewater.

This wastewater needs to be treated before it can be returned to the environment, otherwise, it can harm animals and plants, and make water unfit for drinking. It is easier and more cost-effective to stop pollutants reaching the water course than to try and remove them once they are in our rivers, but even well-treated sewage may be rich in nutrients which can cause algae to grow excessively under certain circumstances. This can starve other species of essential oxygen and stop plants and animals from thriving. Dissolved metals and some chemicals not normally removed by treatment processes can be toxic to animals and plants.

Sewage treatment works are under increasing pressure from population growth and increased frequency of floods and droughts. 18% of the reasons for failure in the Swale, Ure, Nidd and Upper Ouse, and 13% in the Wharfe and Lower Ouse are due to the effect of sewage discharged from wastewater treatment works and discharges from industry.