Study On Removal Of Nitrate From Secondary Effluent By Immobilized Three-dimension Electrode-biofilm Reactor

In this study, the immobilized cell technology was applied in the three-dimension electrode-biofilm reactor for helping the microorganisms to link onto the cathodes. The existing three-dimension electrode-biofilm reactor was improved. Continuous treatment experiments using a secondary effluent containing nitrate were carried out to investigate the advanced denitrification performances by a self-made immobilized three-dimension electrode-biofilm reactor.Various influence such as electric current, HRT, C/N were examined, and the feasible condition was confined. Comparative tests confirmed that the use of immobilized cell technology could promote denitrification effectively. The results obtained in this study suggested that the current density was 30mA and the flux of influent was 9ml/min, the COD and the nitrate removal efficiency was 50% and 82.03%, respectively. The load of denitrification of the reactor was 0.297 mg(NO3--N)/(cm2·d). Under the same operating conditions, the removal efficiency was 20% increased than ordinary reactor by the use of immobilized cell technology.The reactor could only consume 0.06KW·h for the sewage containing 40mg NO₃^--N/L and 76mg COD/L , when nitrate removal efficiency was about 80%. So reactor was operated well under low energy-consumption.To make full use of electrode-biofilm, experiments were designed to contrast the nitrate and COD removal from wastewater with the experimental device put in front or behind the traditional biological installations. The experiments was carried out under the condition that: the temperature of 18℃, HRT for 4h, current density was 30mA, the nitrate containing was around 40mg NO₃^--N/L.The results of the experiments showed that the efficiency of COD was a little higher while the electrode-biofilm device was put ahead than behind; the efficiency of nitrate removal was better while the electrode-biofilm device was put behind than put ahead. With the experimental results, the denitrification reaction in electrode-biofilm device was accounted and analyzed in detail under different technological conditions from the angle of microbe nutrition.