Phosphates and nitrates are useful nutrients but when they become too concentrated in our water environments they can cause problems. The main sources of phosphates coming into water bodies are drainage from farmland (fertilizers, runoff from manure, etc.) and sewage effluent (which contains dishwasher detergents, food and drink additives). Nitrates are used in fertilizer, which help farmers to produce more crops which can mean lower food prices.

However, high phosphate and nitrate levels can cause eutrophication – an issue when there is too much nutrient in a water body (e.g. rivers and lakes). This can cause excessive growth of algae and other plants, which then affects water quality, damages plants and animals and stops us using the water. It can cause severe illness in infants and domestic animals.