With thanks to Water UK, Yorkshire Water and Lenntech BV.

Or click here to view all terms ordered from A-Z.



A biological process, during which nitrifying bacteria convert toxic ammonia to less harmful nitrate. It is commonly used to remove nitrogen substances from wastewater, but in lakes and ponds it occurs naturally.


Water that is unsafe or unpalatable to drink because it contains pollutants, contaminants, minerals or infective agents.

Numeric consent

A consent in which numerical limits are set for the concentration or load of substances discharged and also for the effluent flow.


Any substance that promotes growth with living organisms. The term is generally applied to nitrogen and phosphorus in wastewater, but is also applied to other essential and trace elements.

Nutrient Pollution

Contamination of water resources by excessive inputs of nutrients. In surface waters, excess algal production is a major concern.

Back to top