Study On The Influence Of Environmental Factors On Nitrifiers And Start-Up Of Nitritation Process

Nitritation reaction is the process of ammonia being transformed into nitrite by ammonia oxidizing bacteria(AOB),while its realization depends on the inhibition process of nitrite oxidizing bacteria(NOB)transforming nitrite to nitrate.However,nitrogen could not be removed in the nitritation process through transforming its state from the liquid to the gas.Thus,in order to achieve the complete biological nitrogen removal process,combined nitritation process is needed forming,such as SHARON-ANAMMOX and CANON processes,which demand lower oxygen and fewer carbon source than that of conventional biological nitrogen removal process.Start-up of the nitritation process is based on the efficient inhibition of NOB activity,rendering AOB to be the dominant species.In order to achieve the rapid start-up of the nitritation process,sequencing batch tests were demonstrated firstly to analyze the influences of environmental factors(dissolved oxygen,alkalinity,temperature)on the metabolic responses of AOB and NOB,thereby selecting optimal controlling parameters for NOB inhibition and rapid nitrite accumulation.The results showed that when dissolved oxygen(0.3~2.5 mg/L),alkalinity(438~1429 mg/L)and temperature(15?~30?)were controlled at 0.8 mg/L,1429 mg/L and 30?respectively,AOB activity exhibited higher than that of NOB and NOB activity was markedly inhibited,being beneficial for rapid nitrite accumulation.Secondly,operational controlling parameters and carriers type of rapid start-up and maintaining of nitritation process were determined from the the start-up of nitritation process treating synthetic sewage and the water quality of influent and effluent.The results showed that lower dissolved oxygen concentration(0.4~0.8 mg/L)was more beneficial for nitrite accumulation than that of higher oxygen concentration(0.2~0.4 mg/L);compared with NH4 Cl,NH4HCO3 was more suitable being employed as the nitrogen resource;compared with zeolite,ceramsite and polyethylene multi-surface hollow ring,combined fillers were more suitable as the carriers of the start-up of the nitritation process.Based on the above optimized controlling parameters,nitritation process was successfully started with the ammonia conversion rate of 80.2%and the nitrite accumulation rate of 89.07% when combined-filler SBBR process was operated until 35d.