Long-term Operation And Performance Of A Bioaugmented Membrane-aerated Biofilm Reactor Treating Atrazine Wastewater

In this study,the genetically engineered microorganism?GEM?containing degradation-tracer functional recombinant plasmid was used to form GEM biofilm on the hydrophobic SPG?Shirasu porous glass?membrane surface in a SPG membrane-aerated biofilm reactor?MABR?,treating atrazine wastewater.The atrazine,COD and ammonia nitrogen removal performance and its influencing factors such as SPG membrane pore size,aeration pressure and hydraulic retention time?HRT?were investigated during the long-term operation of the MABR.The results indicated that the oxygen supply capacity could be increased in the SPG membrane aeration when the membrane pore size and the aeration pressure increased,which could improve the performance of COD and atrazine removals.The maximum oxygen supply capacity of hydrophobic SPG membrane with pore size of 1.5 ?m was estimated to be about 22.4 g·?m²·d?^-1.When aeration pressure was 70 KPa and HRT was1.5 h,the average COD removal efficiency was 80.1% and the average organic loading rate removed was 1.86 kg·?m³·d?^-1 in the MABR with 1.5 ?m hydrophobic SPG membrane.Under the same operating conditions,the average atrazine removal efficiency was 62.5%and the average atrazine loading rate removed was 0.18 kg·?m³·d?^-1.The COD and atrazine removal efficiencies decreased significantly at shorter HRT and higher influent organic loading rate.DO concentration showed more significant influence on atrazine removal.Other bacteria were observed in the GEM biofilm during a long-term operation of the MABR and their populations increased gradually.The distribution and abundance of atzA gene in the GEM biofilm samples detected by fluorescence in situ hybridization?FISH?seemed to maintain stably.The green fluorescent effect of the GEM biofilm became more and more weakened along with the MABR operation.And the protozoan was also found in the GEM biofilm.Therefore,the simplex genetically engineered microorganism biofilm became complex microbial community gradually during MABR operation,but the GEM cells could still reside in the biofilm well.Therefore,the efficient atrazine removal by GEM bioaugmentation could be maintained.