Research On Spiral Flow Internal-loop Air-lift Bioreactor

This research is focused on the modification of the bioreactor configuration, aimed to improve the SS removal efficiency, based on analysis of the drawbacks of the existing internal-loop air-lift bioreactor, analysed and summarized the theory of three-phase separator and the theory of centrifugal . It is considered that several modification measures can be taken: We designed spiral three-phase separator and applied on internal-loop air-lift bioreactor, aimed to improve the separation of gas, solid, liquid; the SS of the reactor effluent is reduced by installed spiral three-phase separator on reactor's center tube. According to the considerations mentioned above, modified Spiral Flow Internal-loop Air-lift Bioreactor were designed, extensive experiments have been conducted under different operational conditions. The results of the experimental study can be concluded as following.1. The modified Spiral Flow Internal-loop Air-lift Bioreactor has good effect of COD, NH3-N, TP in control conditions of filler volume, HRT, aeration volume.2. The average COD removal rate up to an average 80% under the reactor stable operation and COD removal rate did not lower with the increase of the load and reduce the amount of aeration. This shows that the system capacity of removing organic matter is still rich. The COD removal efficiency of the system was still as high as 84.94% under given condition--with filler volume in 12L that accounting for 20% of the reaction zone, aeration volume of 0.6m3/h, water flow 16L/h, HRT=3.75h--and at this point the system up to the volume load 2.154kgCOD/ (m3?d), above average aerobic biological treatment process.3. NH3-N removal over 90% under the reactor stable phase. And it reached 97.56%, when the volume load of reactor was 0.269kg NH3-N/(m3?d). It indicates that the improved reactor still has higher removal efficiency to NH3-N. The effluent NH3-N concentration increased and changed insatiably appears with the increase of volume load. Thus the improved spiral flow-loop air-lift reactor volume of NH3-N could initially identified around 0.27kgNH3-N/(m3·d). NH3-N removal decreased with the reduction of aeration amount mainly owing to the reduction of dissolved oxygen in the reactor causing the anaerobic/anoxic state appears at the bottom. So the denitrifying bacteria synchronous denitrifying will eventually generate, which could impact the reactor effluent NH3-N concentration.4. The TP removal of improved system is common. The TP removal rate maintained at about 60% in the stable phase of the system. From the theory of biological phosphorus removal, we know that spiral flow internal-loop air-lift bioreactor is not dominant and The TP removal still rely on the sludge discharge.5. The SS Removal of the spiral flow internal-loop air-lift bioreactor is good. The SS of effluent from bioreactor was reduced obviously no matter the filler volume, HRT and aeration volume--the average of the various stages effluent SS maintained at 30~40mg/L——confirmed preliminary the previously idea of this test.6. Compared micro-organisms of the reactor start-up period and the stable operation period, we found that there are numbers of ciliate protozoa category and rotifers, nematodes and other micro-metazoan in the activated sludge after six months operation.