Nitrate removal from tile drainage water using woodchip denitrification bioreactors

Abstract

Tile drainage systems introduced in agricultural areas significantly alter water and nutrient balance and increase water pollution via accelerated nitrates leaching from the soil. In order to reduce this negative effect, new ways and measures to reconstruct tile drainage systems are being searched for. One of the possible solutions of this problem is installation of denitrification bioreactors at the outlets of the systems. Their presence is based on biological removal of nitrate-nitrogen from tile water under anaerobic conditions. Three denitrification bioreactors imitating tile drainage systems were created in Drainage laboratory of the Water Resources Engineering Institute at Aleksandras Stulginskis University, Lithuania. Bioreactors containers were filled with deciduous, coniferous and mixed wood chips. Laboratory and field tests have shown that the average nitrate-nitrogen removal from water in the bioreactor filled with deciduous woodchips was 66%, with conifer woodchips – 68%, and with mixed woodchips filler – 67%. The obtained results suggested that denitrification bioreactors could be applied in tile drainage systems as edge of field measure to reduce water pollution in drained agricultural areas.