The Electrically Assisted Microbial System Enhances The Removal Of Ammonia Nitrogen In Wastewater

Ammonia nitrogen,as the main component of nitrogen pollution in water,poses a great threat and challenge to the water environment.In this paper,a single-chamber three-electrode electric-assisted microbial system was constructed by introducing electrodes into an anoxic microbial reactor.The effect and mechanism of ammonia nitrogen removal when different substrates?sodium acetate,glucose,sodium bicarbonate,and sodium nitrite?were added to the system was studied;The key factors of the electric-assisted microbial system with ammonia nitrogen as the electron donor,bicarbonate as the sole electron acceptor and carbon source was explored.Based on the single-chamber electric-assisted microbial system,bicarbonate and nitrite were used as electron acceptors,and a two-chamber electric-assisted microbial system was constructed to study its effect on the removal of ammonia nitrogen by microorganisms.In order to further explore the conversion of ammonia nitrogen in the anode chamber without microorganisms,an electric-assisted microbial cathode coupled with electrocatalytic anode system was constructed.The results show that:?1?After long-term domestication,the single-chamber three-electrode electric-assisted microbial system can use the organic substance sodium acetate to convert ammonia nitrogen into nitrogen with a conversion rate of 77.39%;however,the system cannot use glucose for the conversion and removal of ammonia nitrogen.In order to reduce the use of organic carbon sources in biological degradation process,bicarbonate is used as the sole carbon source and electron acceptor.The system removed 45.65 mg·L^-1of ammonia nitrogen,and the removal rate is 75.21%.The equivalent conditions for biological systems without external potential removed25.57 mg·L^-1of ammonia nitrogen.The enhancement of microorganisms by electric-assisted treatment has improved the removal rate of ammonia nitrogen by70%.In the system using nitrite as the electron acceptor,the electric-assistant stimulation of microbial activity strengthened the biological anode oxidation of ammonia nitrogen,and in addition,the nitrite can be reduced faster by biological cathode.?2?The electric-assisted microbial system using bicarbonate as a carbon source and an electron acceptor is significantly affected by the IC/TN molar ratio,external potential,temperature,and p H.When the initial concentration of ammonia nitrogen is60 mg·L^-1,the system achieved the maximum nitrogen removal efficiency at an external voltage of 1.0 V.Excessive voltage is harmful to microorganisms.Biomass activity is affected by temperature and p H,so the system has the optimal temperature and p H.Ammonia nitrogen removal efficiency is the highest at a temperature of303.15 K and p H=7.5.The molar ratio of inorganic carbon and ammonia nitrogen consumption during system operation is about 1.10:1.So when the substrate addition ratio is slightly higher than or equal to this ratio,the nitrogen removal ratio of system is the highest.?3?Under the condition of low substrate concentration,when the two-chamber electric-assisted microbial system uses nitrite and bicarbonate as the electron acceptor,the removal rate of anode ammonia nitrogen is 70.92%and 91.96%,respectively.This system improves the removal rate of ammonia nitrogen.The electric-assisted microbial cathode coupled with electrocatalytic anode system will greatly reduce the running time of removing the same amount of ammonia nitrogen and further improve the nitrogen removal efficiency.