Bioreactors are subsurface trenches filled with a carbon source, mainly wood chips, through which water is allowed to flow just before leaving the drain to enter a surface water body. The carbon source in the trench serves as a substrate for bacteria that break down the nitrate through denitrification or other biochemical processes. Bioreactors provide many advantages:

• Simple & proven technology

• Cost efficient

• Odoriferous contamination control

• No land needs to be taken out of production

• No decrease in drainage effectiveness

• Little or no maintenance

• Can last for up to 20 years