Sodium Carboxymethyl Cellulose-Modified Zero-Valent Iron Used for Redunction of Nitrate in Autotrophic Denitrification Systems

Abstract

Zero-valent iron (ZVI) has been reported as an effective material for the reduction of nitrate in autotrophic denitrification systems. The aim of this study was to investigate the effect of the iron-reducing bacteria CC76 combined with carboxymethyl cellulose (CMC)-ZVI on nitrate reduction reaction in simulated groundwater under anaerobic conditions. Optimization conditions of biological denitrification as well as the process of iron cycle using the bacterial strains CC76 and CMC-ZVI were determined. Temperature (20.00°C, 30.00°C, and 40.00°C), initial pH (6.00, 7.00 and 8.00), and CMC-ZVI concentration (1.00, 3.00 and 5.00 g/L) were selected for response surface methodology experiments. Statistical analysis revealed that the highest nitrate removal efficiency was obtained under the conditions of a temperature of 32.20°C, initial pH of 6.87, and CMC-ZVI concentration of 3.40 g/L. Images from scanning electron microscopy and X-ray diffraction showed that the CMC-ZVI had better physical characteristics to promote denitrification in the autotrophic denitrification system.