Study on the Electrochemical Nitrogen Removal Efficiency in the Bio-electrochemical Denitrification Part of CANNED Process
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Graphical Abstract
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Abstract
The electrochemical nitrogen removal efficiency in a bio-electrochemical denitrification part of Complete Autotrophic Nitrite-nitrification and Electrochemical Bio-denitrification Combined Process (CANNED) was studied before the biofilm inoculation stage under pure electrochemical conditions, which was 24 h HRT and 0.052 mA/cm2 electric current density, when the influent nitrogen forms were NO2--N, NH4+-N and NO2--N+NH4+-N, respectively. The results were shown as follows: When only NO2--N was added and the NO2--N influent concentration increased from 100 mg /L to 400 mg /L, NO2--N was removed partially by the bio-electrochemical part but the NO2--N removal efficiency reduced gradually from 40% to about 20%, which was might due to the oxidation of HClO produced from the influent constant Cl- concentration. When only NH4+-N was added and the influent NH4+-N concentration increased from 100 mg/L to 400 mg/L, the bio-electrochemical part NH4+-N removal efficiency was kept about 35%. This was mainly because that NH4+-N was supplied in the form of NH4Cl in the influent and the concentration of Cl- and HClO reacted with NH4+-N increased with the NH4+-N increasing accordingly. When NO2--N and NH4+-N were both added, the removal efficiency of each individual ion was almost the same as the NO2--N and NH4+-N were added separately. The results showed that NH4+-N and NO2--N were removed partially by the influent Cl- and there was no electrochemical interaction of the NH4+-N and NO2--N removal under the electrochemical conditions in the bio-electrochemical part of CANNED.
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