Nitrate removal from groundwater in columns packed with reed and rice stalks

Abstract

Nitrate leaching contaminates groundwater. The objective of this study was to determine if reed and rice stalks could enhance denitrification and reduce nitrate leaching into groundwater. Artificial groundwater spiked with nitrate and field groundwater samples were tested in the columns in sand reactors packed with either reed or rice stalks. The maximum nitrate removal rates were determined to be 1.93 and 1.97 mg nitrate‐N l⁻¹ h⁻¹, respectively, in the reed and rice stalk‐packed columns. The maximum nitrate‐nitrogen removal rate in reactors packed with reed stalk was 1.33 mg nitrate‐N l⁻¹ h⁻¹ when experimented with natural groundwater. Chemical oxygen demand consumption was higher when rice stalk (176.1 mg l⁻¹) was used as the substrate, compared to reed stalk (35.2 mg l⁻¹) at the same substrate dosage. No nitrite accumulation was detected during the test. The results demonstrate that agricultural byproducts, such as reed and rice stalks, may be used as substrate amendments for enhanced denitrification in natural settings, such as lakeside lagoons, ditches or wetlands.

Keywords:

• denitrification
• groundwater
• nitrate
• reed stalk
• rice stalk

Acknowledgments

This study was supported by the National Natural Science Foundation of China (No. 40672154 and No. 40872166), Program for New Century Excellent Talents in University (No. NCET‐06‐0541) and the National Basic Research Program of China (‘973’ project: 2007CB815603).