Method for enhancing denitrification of sewage with low carbon-to-nitrogen ratio by using electrode biocarrier

A method for enhancing denitrification of sewage with a low carbon-to-nitrogen ratio by using an electrode biocarrier, comprising the following steps:

• (I) acclimation of an electrode biocarrier
• (1) spatial configuration and pretreatment of an electrode
• using a carbon-based material or a metal material as an electrode;
• firstly, soaking the electrode with acetone for 24 h to remove organic impurities on a surface of the electrode, and then washing and drying the electrode for later use, wherein the electrode is configured to have a two-dimensional planar structure or a three-dimensional structure, and the three-dimensional structure is a graphite rod structure, a carbon fiber brush structure, a carbon-based layer stacked structure or a sheet metal layer stacked structure;
• (2) enrichment of an electroactive denitrification biofilm
• using an activated sludge as an inoculum, and adopting a three-electrode electrochemical reactor with the electrode obtained in step (1) as a working electrode and a carbon-based material or a metal material as a counter electrode, wherein the working electrode and the counter electrode are separated by an ion-exchange membrane, and the ion-exchange membrane is a cation exchange membrane or a proton exchange membrane;
• placing silver/silver chloride as a reference electrode in the three-electrode electrochemical reactor, controlling an environment in a working electrode chamber to be anaerobic, while an environment in a counter electrode chamber being not controlled;
• applying voltage by a direct-current power supply or inducing a micro electric field by a potentiostat to control potential of the working electrode in a range of −0.2 V to −0.7 V;
• and
• feeding with an artificial wastewater adding carbon source but without nitrate during a start-up phase, and operating the three-electrode electrochemical reactor in a sequential batch mode until a current changes periodically and steadily for 4 or more cycles, and then adding the sewage with a low carbon-to-nitrogen ratio until a stable operation;
• wherein the pure carbon source added during the start-up phase is a volatile organic acid;
• wherein the sewage with a low carbon-to-nitrogen ratio has real domestic sewage or simulated artificial water as a substrate;
• a carbon source in the substrate is a volatile organic acid or other biodegradable organic matter, and a nitrogen source in the substrate is nitrate nitrogen;
• the carbon-to-nitrogen ratio of the substrate is controlled to be less than or equal to 5;
• wherein the working electrode chamber works in a sequential batch mode or a continuous flow mode;
• under the condition that a nitrogen removal rate in the substrate is 90% and an output current changes periodically or remains unchanged, the enrichment of the electroactive denitrification biofilm is completed;
• and
• (II) control of deep denitrification of the sewage with a low carbon-to-nitrogen ratio
• after the acclimation of the electrode biocarrier, controlling the carbon-to-nitrogen ratio of the sewage in the working electrode chamber to be less than or equal to 5 and potential of the working electrode in the range of −0.2 V to −0.7 V.