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Self-standing Electrochemical Set-up to Enrich Anode-respiring Bacteria On-site
Published on: July 24, 2018
Using Fe(II)/Fe(III) as catalyst to drive a novel anammox process with no need of anammox bacteria
Yafei Yang1, Cancan Xiao2, Qing Yu2
1Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education, China), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China; School of Ecology and Environment, Zhengzhou University, Zhengzhou 450001, China.
Abstract:
A novel 'anammox' in the absence of anammox bacteria was confirmed to occur in an anaerobic sludge slurry system, in which Fe(II)/Fe(III) cycle driven by NO2--induced Fe(II) oxidation and subsequent NH4+-induced Fe(III) reduction (Feammox) pushed the nitrogen removal. Results showed that Fe(II) contents significantly (p<0.05) decreased and Fe(III) accordingly increased with NO2- addition, indicating that Fe(II) was anaerobically oxidized to Fe(III). With depletion of NO2-, the Fe(II) content began to increase which was a result of Feammox. Consequently, 96.0% NH4+-N of the NO2--added reactor was removed during 18 days operation, while NH4+-N content remained essentially unchanged in the control in which NO2- was not added. X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) analysis indicated that FeOOH was produced from chemical Fe(II) oxidation with NO2-. During the treatment, anammox bacteria was not detected, but the relative abundance of Geobacter of the NO2--added group increased by 13 folds. Isotope experiment in 15NH4+-containing reactors found that much more 30N2 and 29N2 in the 14NO2--added group were produced than those in the control (without 14NO2-), confirming that 14NO2- induced Fe(II) oxidation to participate in Feammox for 15NH4+ removal. Also, NO2- could be produced from partial denitrification of NO3-, meaning that NO3- as a more common species might substitute NO2- to trigger this new anammox process.
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