有机碳源及DO对好氧反硝化细菌AD6脱氮性能的影响

Effect of Carbon Source and Dissolved Oxygen on Denitrification by Aerobic Denitrifier Pseudomonas mendocina AD6

采用摇瓶实验,研究了C/N值、培养液DO及柠檬酸盐、乙酸盐、葡萄糖3种有机碳源对好氧反硝化细菌Pseudomonas mendocina AD6脱氮性能的影响.C/N值不仅直接影响好氧反硝化过程中碳源数量,也显著影响培养液DO变化.C/N值为3时,因碳源数量不够而导致AD6好氧反硝化脱氮效率仅有42%;当C/N值为23、15、8时,培养液DO先快速下降至缺氧状态然后再升至好氧状态,反应末期TN损失率分别为69%、70%、55%,其中好氧条件下反硝化作用引起的TN损失约为7%、20%、25%.培养液起始DO在7.15～8.08mg/L,C/N值为15及以下,摇瓶(250mL三角瓶)装液量为25～100mL,摇床转速为180r/min,培养液DO先下降至缺氧状态,但可在反硝化反应进行24h后恢复至好氧状态,减少摇瓶装液量的充氧措施提高培养液DO效果有限.柠檬酸盐与乙酸盐是AD6能够高效利用的碳源,利用率可达90%、92%,而葡萄糖的利用率仅有41%.乙酸盐促进了AD6的好氧反硝化功能,TN去除率、好氧反硝化脱氮效率分别比以柠檬酸盐为碳源时高14%、5%.采用摇瓶试验评估好氧反硝化细菌的好氧反硝化效率应谨慎,因为取决于溶液的C/N值和碳源种类,可能相当部分N的损失是在缺氧条件下产生.

Aerobic denitrifying performances of P.mendocina AD6 at various C /N ratios,dissolved oxygen（DO） concentrations and carbon sources including citrate,acetate,and glucose were evaluated through flask experiment.At an insufficient carbon concentration,namely C /N ratio of 3,total nitrogen（TN） removal efficiency was 42% by aerobic denitrification.When the C /N ratio was increased to 8,15,and 23,the TN removal efficiency by AD6 quickly increased to 55%,70%,and 69%,in which 7%,20%,and 25% of TN losses could be contributed to the aerobic denitrification by AD6,respectively.Batch cultures were carried out in a series of 250 mL conical flasks containing 100,50,and 25 mL of the nitrate-supplemented basal medium with C /N ratio of 15,DO of 7.15-8.08 mg /L and strain AD6.Flasks were shaken in a rotary shaker at 28℃ and 180 r /min to allow better gas exchange.DO concentration of culture medium declined rapidly to anoxia condition at the beginning of reaction followed by an aerobic level with above 2 mg /L of DO after 24 h reaction.Different carbon sources had strong influence on the aerobic denitrifying performance of strain AD6.The maximum consumption rates of citrate,acetate,and glucose by strain AD6 were 90%,92%,and 41%,respectively.In the medium spiked with acetate as carbon source,TN removal efficiency and N losses due to aerobic denitrification increased to 14% and 5%,respectively,with comparison to that spiked with citrate.Evaluation on nitrogen removal performances of aerobic denitrifier should be cautious with flask experiment because aerobic,partial aerobic and total anoxic growing conditions could be changed by C /N ration and carbon source of medium.