Process Control Of Simultaneous Shortcut Nitrification And Denitrification In A Sequencing Batch Moving Bed Biofilm Reactor

The experiments were carried out in sequencing batch moving bed biofilm reactors which were operated in the pattern of A/O. In the experiment, the factors which could affect the working condition of simultaneous shortcut nitrification and denitrification, such as different distribution of anaerobic time and aerobic time, COD concentration, concentration of NH₄⁺-N, pH valu and dissolved oxygen and so on; the treatment effect on the actual domestic wastewater was studied too. On the other hand, the properties of MBBR working conditions were also investigated. The experimental results are shown as follows:(1) The removal rate of COD and NH₄⁺-N are quite close in both the serial system and single reactor when the working condition are the same in the MBBR.(2) When the working conditions in the MBBR system are changed, the influence on COD effect is not as obvious as that of in the nitrogen removal. While the nitrogen removal can be recover quite soon. That means a thick biofilm in the carrier of the system and it makes a well oxygen gradient distribution and an anaerobic microenviroment is formed. It provided a suitable condition for the simultaneous shortcut nitrification and denitrification.(3) The total nitrogen removal rate reached 66.4% in SBMBBR system when controlling the anaerobic time (3h), nitrogen concentration of influent (50mg/L), pH (8.0), and DO (1.0 mg/L) in a low COD concentration. At the same time the nitrite rate reached 99.7%, the nitrogen removal in the low COD system had been enhanced.(4) Anaerobic time influenced the nitrite rate in the sequencing batch moving bed biofilm reactor. A 3h's anaerobic time can reach a 57.2% total nitrogen removal rate. And the nitrite concentration is 2.26 mg/L in the experiment.(5) A relative high nitrite rate and total nitrogen removal rate can be gained when the COD concentration of influent is low and the NH₄⁺-N is suitable. That is say when the COD concentration of influent is 100 mg/L and the NH₄⁺-N concentration of influent is 40-60 mg/L the indexes mentioned above is 56.4% and 55.6%.(6) The nitrate effect is clearly while the denitrification is inhibited when the pH value is 8.0. There was no shortcut nitrification in the system when the pH value is 7.3. But a relative high total nitrogen removal rate is gained at this time. That shows a simultaneous shortcut nitrification and denitrification can hardly realize in a neutral environment. (7) Low DO condition can realize simultaneous shortcut nitrification and denitrification in the SBMBBR. And when DO is 1.0 mg/L, the total nitrogen removal rate reached 66.4%.(8) Taking the best working condition of the SBMBBR: anaerobic for 3h and aerobic for 6h, adjusting the DO at 1.0 mg/L and pH 8.0 as the working environment, the system treatment effect on actual domestic wastewater reached a total nitrogen removal of 90.9%.(9) In the treatment on actual domestic wastewater the nitrogen transform changed from simultaneous shortcut nitrification and denitrification into simultaneous nitrification.