Comparing Carbon Substrates for Denitrification of Subsurface Drainage Water

Abstract

Nitrate in water from tile drained corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] fields in the U.S. Midwest contributes to nitrate contamination of surface waters. Denitrification-based biofilters are a promising strategy for reducing nitrate concentrations, but these systems require an external carbon supply to sustain denitrification. The ability of four organic materials to serve as carbon substrates for denitrification biofilters was evaluated in this laboratory study. Wood chips, wood chips amended with soybean oil, cornstalks, and cardboard fibers were mixed with subsoil (oxidized till) and incubated anaerobically for 180 d. Periodically, 15NO3-N was added to maintain nitrate N concentrations between 10 and 100 mg L-1. All of the materials stimulated NO3-N removal and the degree of removal from highest to lowest was: cornstalks, cardboard fibers, wood chips with oil, and wood chips alone. Analysis of 15N showed that immobilization and dissimilatory nitrate reduction to ammonium accounted for <4% of NO3-N removal in all treatments, therefore denitrification was the dominant NO3-N removal process. Cardboard fibers, wood chips and oil, and wood chips alone did not support as much denitrification as cornstalks, but their rates of NO3-N removal were steady and would probably continue longer than cornstalks. The addition of soybean oil to wood chips significantly increased denitrification over wood chips alone.

Efficiency of Drainage Practices for Improving Water Quality in Lithuania

“…According to Christianson et al (2012), the type of carbon fill is one of the most important considerations in denitrification systems because the properties of the medium affect factors that influence nitrogen removal. Therefore, there is considerable discussion in the literature about the use and effects of the physical, chemical, and other properties of various fill materials (Schipper and Vojvodic-Vukovic, 1998;Greenan et al, 2006;Jaynes et al, 2008;Cameron and Schipper, 2010;Warneke et al, 2011). However, woody media are preferred due to their cost and longevity.…”

Technical Note: Hydraulic Property Determination of Denitrifying Bioreactor Fill Media

“…Woodchips are commonly used as the carbon substrate in denitrification bioreactors in the Midwest due to their longevity, good performance, and easy availability (Cooke et al, 2001;Greenan et al, 2006). However, other solid carbon sources may also be used.…”

Recycling Vertical-Flow Biofilter: A Treatment System for Agricultural Subsurface Tile Water

“…Therefore, the efficiency of surface systems for treatment may be reduced because substantial amounts of contaminated water may bypass the active treatment zone. To address this limitation, subsurface systems such as in-situ bioreactors, permeable reactive barriers, biofilters, and subsurface flow constructed wetlands have been investigated (Bezbaruh and Zhang, 2003;Darbi et al, 2003;Greenan et al, 2006;Robertson et al, 2007;Schipper and Vojvodic-Vakovic, 2000;Schipper and Vojvodic-Vakovic, 2001;Schipper et al, 2004;Su and Puls, 2007;van Driel et al, 2006). These subsurface systems generally depend on microbial denitrification to mineralize and remove nitrate.…”

“…As such, it requires anaerobic conditions in the subsurface as well as an adequate supply of electron donors and available carbon. Thus, an exogenous source of carbon such as wood chips or sawdust is usually required for these systems to function properly (Greenan et al, 2006;Lin et al, 2002;Vymazal, 2007). We recently reported on a recycling vertical-flow bioreactor (RVFB) for the treatment of household greywater (Gross et al, 2007).…”