Nitrate removal and hydraulic performance of organic carbon for use in denitrification beds

 

Situation: Denitrifying bioreactors are an effective way to remove nitrogen (N) from runoff. Most field trials and operational bioreactors use woodchips as the carbon source necessary to support denitrification. However, other carbon sources may provide increased N removal rates, lower installation costs, and reduced bioreactor sizes. 

 

Actions: A study in New Zealand by Drs. Cameron and Schipper compared the nitrate-N removal rates of nine different carbon substrates at two different temperatures over a 23 month period. The substrates used were five different grain sizes of pine woodchips (softwood), eucalyptus woodchips (hardwood), maize cobs, green waste, and wheat straw. 

 

Take-home message: 

• There was no difference in nitrate-N removal rates between the pine woodchips of different grain size.
• There was no significant difference in nitrate-N removal rates between hardwood media and softwood media.
• Maize cob had significantly higher nitrate-N removal rates for both temperature treatments than other media. It is likely that maize cobs would need to be replaced more frequently.

 

For more information:

• Cameron, Stewart G., and L. A. Schipper. 2010. Nitrate removal and hydraulic performance of organic carbon for use in denitrification beds. Ecological Engineering (36): 1588-1595
• Email scameron@gns.cri.nz or schipper@waikato.ac.nz