Characteristics And Simulation Of Denitrifying Nitrogen And Phosphorus Removal In Sequencing Batch Hybrid Reactor(SBHR)

In order to study the technology of simultaneous nitrogen and phosphorus removal of municipal wastewater with high load,low carbon source consumption,low oxygen demand and low sludge production,a sequencing batch hybrid reactor(SBHR)system was studied in this paper based on the latest researches on hybrid biological reactor and denitrifying dephosphatation.The rapid start-up of SBHR and the enrichment of denitrifying phosphorus accumulating bacteria were investigated.Then,the mechanisms of denitrifying nitrogen and phosphorus removal,the effect of substrate on nitrogen and phosphorus removal,and the characteristics of microbial community in SBHR were studied by means of fluorescent in situ hybridization(FISH)technology,back propagation artificial neural network(BP-ANN),1 6S rDNA high throughput sequencing technology,and the fluidization in SBHR was simulated by computation fluid dynamics(CFD).All of these mentioned above provided the theoritical support for the applications of SBHR.Microorganisms for denitrifying phosphorus removal in SBHR were enriched and cultured with the operating conditions:temperature of 20-25?,pH of 6.5-8 and stirring speed of 80 r/min.The SBHR system was operated for 30 d with a mode of anaerobic/anoxic/short-time aerobic and then operated for 30 d with a mode of anaerobic/aerobic/anoxic.After 60 d operation,the COD,NH4+-N and TP removal was higher than 90%,96%and 90%,respectively.The phosphorus accumulating bacteria became the dominant species in the SBHR system according to FISH technique.The transformation and degradation characteristics of COD,nitrogen and phosphorus in SBHR system were studied after enrichment and culturing of phosphorus accumulating bacteria.Analysis of a single operation cycle showed that 58.3%of COD was consumed in the anaerobic period and 34.3%of COD was removed in the aerobic period;39.2%of TN was removed in the anaerobic period,and 50.4%of TN was removed in the aerobic period with simultaneous TP removal by denitrifying phosphorus removal.The SBHR system ran stably for 3 months,and the average COD,TN and TP removal reached 94.7%,90.7%and 95.8%,respectively.The BP-ANN model was established to forecast the effluent quality.The continuous experimental data for 44 d was taken as the training samples for BP-ANN model.The prediction results showed that the results predicted by BP-ANN model were verified by the measured results.The mean absolute error of all test samples was below 3.35%.The contribution of each influent factor to effluent quality was investigated by weight analysis method.The influent C/P ratio showed the greatest influence on SBHR system performances.The nitrogen and phosphorus removal efficiency of SBHR system was the highest when the influent C/P ratio was 31-44.Experiments proved that the best influent C/P ratio and C/N ratio should maintain between 30-45 and 10-15.Based on 16S rDNA high-throughput sequencing technology,diversity of microbial community of suspended sludge and biofilm in the SBHR system was analyzed.The results showed that biological abundance of biofilm was higher than that of suspended sludge.Proteobacteria was the dominated phylum and accounted for 75.2%and 60.5%in suspended sludge and biofilm,respectively.There are 5 class of Proteobacteria,which all were found in the SBHR system,including Alphaproteobacteria,Betaproteobacteria,Gammaproteobacteria,Deltaproteobacteria and Epsilonproteobacteria.The Betaproteobacteria and Gammaproteobacteria were the two main classes of Proteobacteria.The Betaproteobacteria accounted for about 63.3%and 40.5%in suspended sludge and biofilm,respectively.The bacterial were well-distributed on the level of order,and the dominant bacteria were Rhodocyclale,Burkholderiales and Xanthomonadales.On the level of genus,the dominant bacteria such as Rhodoferax,Dechloromonas and Pseudomonas were 14.0%,12.6%and 10.1%in suspended sludge,respectively;Rhodoferax,Flavobacterium,Propionivibrio and Thauera were 15.4%,12.2%,10.2%and 10.1%in biofilm,respectively.Among these bacteris,Rhodoferax,Dechloromonas,Pseudomonas and Propionivibrio all belonged to bacteria for denitrifying phosphorus removal.So the bacteria for denitrifying phosphorus removal were the dominant bacteria in the SBHR system.Based on FLUENT software,the fluidization of in the SBHR was simulated by CFD under different stirring speeds.It was found that the shearing force was unevenly distributed in SBHR,but mainly stronger around the stirrer.Three dimensional simulation of gas-liquid two-phase flow with different aeration times in the SBHR was established.Simulation results showed that the air was unevenly distributed in the aerobic phase,so the anaerobic zone and anoxic zone coexisted in the SBHR system,and the transfer gradient of oxygen was benefit for the biological denitrifying nitrogen and phosphorus removal.However,with aeration weakened,the air was well-distributed by the shearing force of stirrer in the anaerobic phase,which made the system totally in an anaerobic environment for nitrogen and phosphorus removal.The SBHR simulation showed that the reactor structure and operation mode had a positive effect on denitrifying nitrogen and phosphorus removal of system,which provids a support for the practical application of SBHR system.