电极生物膜反应器去除硝态氮的工艺条件研究

摘 要：根据电化学生物反硝化理论，用自制的电极生物膜反应器处理模拟地下水中的硝态氮，研究了该反应器在处理硝态氮时影响去除率的主要影响因素，得出的该反应器的最佳工艺条件：最佳电流为5mA，最佳碳氮比为2，最佳温度为35C，最佳停留时间为6小时。

关键词：电极生物膜法，硝态氮，反硝化，地下水

Abstract-Biofilm-electrode process was used in treetment of groundwater containing nitrate.The result shows that biofilm-electrode process has higher rate of nitrate degradation than traditional biofilm process under a similar conditions.With no organic carbon source， autotrophic denitrifying bacteria play a role in nitrate degradation， biofilm-electrode process has a 24% rate of nitrate degradation.The reactor that biofilm both on anode and cathode has a higher rate of nitrate degradation than the reactor that biofilm only on cathode.The rate of nitrate degradation can be 100% under the condition that current is 5mA，m（C）/m（N） is 2，temperature is 35℃，HRT is 6h.

Keywords- biofilm-electrode process；denitrification； groundwater； nitrate

1.Experimental facility and method

The reactor is made of glass，diameter is 8.2cm，height is 15cm，cubage is 0.8L.Cathode and anode are all made of graphite plate，length is 10cm，width is 5cm，area is 50cm2，distance between cathode and anode is 2cm.The reactor is stirred by a constant temperature stirrer，we can control temperature of the reactor and stir the water to make the concentration of nitrate uniform.The reactor connects direct-current power suply and current can be controlled.

Inoculate activated sludge to the reactor and infunde nutrient solution，cultivate activated sladge under normal temperature and anaerobic conditions，change water every day. We can see thinnish biological membrane on electrode after 15 days.Clear surplus sludge away from the reactor，cultivate biological membrane on electrode under low current condition，control current at 2mA.m（C）/m（N） is 3：1，concentration of nitrate inflow is 50mg/L.Change water every day and detect concentration of nitrate outflow，nitrate degradation rate achieves stabilized 70% after 20 days，it succeeds in cultivating biological membrane.

2.Result and discussion

2.1 Effect of current on nitrate degradation rate

Experimental condition：temperature is 30℃、m（C）/m（N） is 2：1，HRT is 6 hours，concentration of nitrate inflow is 50mg/L.Conduct an experiment when current is 1mA、3mA、5mA、8mA、10mA、15mA.

nitrate degradation rate grows when current rises， nitrate degradation rate is highest when current is 5mA，the rate is 100%.Then nitrate degradation rate reduce when current keep on rising.It go against nitrate degradation when rurrent is too low or too high. Under our experimental condition，the best current is 5mA，the best current density is 0.1mA/cm2.

2.2 Effect of carbon nitrogen ratio on nitrate degradation rate

Experimental condition：Current is 5mA、temperature is 30℃、HRT is 6 hours、concentration of nitrate inflow is 50mg/L.Conduct an experiment when m（C）/m（N） is 0.5、1、1.5、2、2.5.

nitrate degradation rate can reach 25% with no organic carbon source. Nitrate degradation rate rises when organic carbon source is increased. 93% when m（C）/m（N） is 2， 100% when m（C）/m（N） is 2.5. Nitrate degradation rate will be higher or HRT will be shorter if keep on increasing organic carbon source，but nitrate degradation rate is enough high when m（C）/m（N） is 2 or 2.5，so it is dispensabale to keep on increasing organic carbon source. Concentration of nitrite in outflow is ruleless along with rising of carbon nitrogen ratio，and variation trend of total nitrogen degradation rate is similar to nitrate degradation rate. Biofilm-electrode process is appropriate for treetment of low carbon waste water，such as groundwater containing nitrate.

2.3 Effect of temperature on nitrate degradation rate

Experimental condition： current is 5mA、m（C）/m（N） is 2、HRT is 6 hours、concentration of nitrate inflow is 50mg/L. Conduct an experiment when temperature is 15℃、20℃、25℃、30℃、35℃、40℃.

The experimental result shows that there is a best temperature range in which nitrate degradation rate is highest. Nitrate degradation rate is greater than 80% when temperature is between 25℃ and 40℃， 100% when temperature is 35℃. Nitrate degradation rate is only 43% when temperature is 15℃， nitrate degradation rate will rise as temperature rise，and nitrate degradation rate drop as temperature keep on riseing when temperature is greater than 35℃.

3. conclusion

Current 、HRT、carbon nitrogen ratio、temperature will influence nitrate degradation rate obviously in biofilm-electrode process.The best technological parameter under our experimental condition is：current is 5mA、HRT is 6 hours、m（C）/m（N） is 2-2.5、temperature is 30℃-35℃.

作者简介：陈 芝，1983.11.09，女，江西抚州，江西科技学院，讲师，硕士学位，物理电子。