Effect of detachment on nitrification process in biofilm system

摘要

The aim of this study is to evaluate the effect of detachment on nitrification process in a mixed-population biofilm.The biofilm was grown under constant flow condition and at low C/N ratio in a tube biofilm reactor.Detachment experiment was performed by temporarily increasing the influent flow rate into the tube reactor Changes in the composition of biofilm were examined by Denaturing Gradient Gel Electrophoresis (DGGE).Results showed that ammonium oxidation rate reached above 99％ after three weeks.Then,nitrate was detected.However,during the experiment nitrite in the effluent was observed all the time.It was found that biofilm sloughing could cause the increase of nitrite concentration in the effluent.Sloughing events happened mainly under constant hydrodynamic condition,even though flow rate in the tube was increased to 4000 mL/min,it did not cause a significant biofilm sloughing.DGGE fingerprints revealed that there was no significant shift in the composition of bacterial community throughout biofilm,but some differences in each lane were noted in band intensities in DGGE pattern.Therefore,biofim sloughing could induce the change of bacterial abundance in biofilms to influence the nitrification process.