[Factors affecting denitrification by denitrificans coated electrode].
OBJECTIVE
To optimize the efficiency of coated electrode denitrifying reactor.


METHODS
Synthetic groundwater was treated by coated electrode denitrifying reactor submitted to different operational parameters, such as electric current intensity (CI), oxidation reduction potential (ORP), hydraulic retention time (HRT) and temperature.


RESULTS
Denitrification efficiencies of the reactor was found to be related with the applied electric current. The denitrification efficiency was 57.3% with a HRT of 12 hours and the optimum applied electric current intensity was 15 mA. Nitrate removal rate of the reactor was calculated to be 34.4 g NO3(-)-N/m3 x d. Denitrification efficiencies were also found to be related to HRT. The average denitrification velocity was 0.183 mg NO3(-)-N/h within 12 hours. The denitrification rates increased when the temperature of synthetic water raised from 5-35 degrees C. After the electrodes had been connected to the power supply for 1 hour, the concentration of dissolved oxygen (DO) and ORP decreased sharply to 1.08 mg/L and -40 mV, respectively.


CONCLUSIONS
An adaptable reduction environment could be set up in the reactor for autotrophic denitrification shortly after the bio-electrochemical reaction began. The optimum electrode potential and current density were 2.5 V and 0.083 mA/cm2 . As the bio-electrochemical reaction went on, the pH volume decreased sharply, and nitrite accumulation was found corresponsively, which leads to the inhibition of denitrification. HRT should be controlled within 12 hours. Anode oxidation reaction could offer inorganic carbon sources for autotrophic denitrifying bacteria, but might lead to pH increase, should be paid attention in the practical operation.
Tan
Youming
Y
School of Public Health, Shanghai Second Medical University, 200025 Shanghai, China.
Wang
Meng
M
Luo
Qifang
Q
D019149:Bioreactors; D004563:Electrochemistry; D004566:Electrodes; D009566:Nitrates / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*
D009566:Nitrates