Even if we might not know the meaning of ‘eutrophication’, we have all seen green rivers or lakes, caused by a dense algal bloom. This phenomenon arises from the excess of nutrients released into fresh waters from domestic effluent, or industrial and agricultural activities. It is a worldwide environmental concern that reduces aquatic biodiversity and water quality. Artificial drainage accelerates the pathway, due to short-circuiting, into rivers of nitrates coming from the urine of grazing animals or manure application. Lincoln Agritech and Aqualinc Research have established a pilot-scale denitrifying bioreactor draining an area of 0.65 ha dairy cow grazed paddock.