同步硝化与反硝化(SND)好氧颗粒污泥脱氮过程初步研究

ON DENITRIFICATION PROCESS BASED ON SIMULTANEOUS NITRIFICATION AND DENITRIFICATION IN AEROBIC GRANULAR SLUDGE

研究好氧颗粒污泥的同步硝化反硝化脱氮,寻找消除氮素对水体污染的途径。在反应器中培养了好氧条件下具有同步硝化反硝化功能的颗粒污泥,进行脱氮过程研究。好氧颗粒污泥为无载体结构,直径2～3 mm,其构成松隙,具有厌(兼)氧与好氧微生物生长代谢的环境;反应液中氨氮浓度为201 mg·L-1时,6 h反应周期内氨完全被氧化,出水中检测不到NO2--N,仅残留2 mg·L-1的N03一N,硝化与反硝化两个过程完成了脱氮反应,颗粒污泥中存在硝化细菌和反硝化细菌;改变反应器中进水有机物浓度,发现COD浓度越大,氮去除率越低,硝化细菌在高有机物浓度下反应活性受抑制,自养硝化细菌竞争氧及其他营养物质的能力弱于异养细菌;在好氧条件下(4 mgO2·L-1),进水中不加有机碳源,反应6 h后NH4+-N去除率达75％,反应过程中pH值下降,说明颗粒污泥中硝化细菌为自养型,硝化反应产酸降低反应器中pH值;在厌氧条件下,进水COD和NO3--N浓度分别为227.25 mg·L-1和103.63 mg·L-1,反应结束后,NO3--N去除率为74％,反应过程中pH值呈上升趋势,证明了好氧颗粒污泥中存在厌氧反硝化细菌,且反硝化细菌生长于颗粒污泥内部的厌氧区域,反硝化产碱使反应液pH值上升。

This article is aimed to present the new aerobic granular sludge for the denitrification process based on the simultaneous nitrification and denitrification so as to find a way to reduce the water pollution caused by nitrogen. As is known, nitrogen is one of the main factors concerning water pollution. The denitrification process can be done in the aerobic condition with the granular sludge cultivated in a reactor. It is through this reactor the denitrification process can be observed and investigated. Analyzing the electronic microscopic scanning results with the granular sludge, the author has found that the granular sludge is a perfect space for the aerobic and anaerobic microorganisms to grow. In the condition with NH4 + -N 201 mg · L-1 in the influent, the granular sludge is in a position to remove almost all of NH4 + -N, while NO2--N could not be detected and the NO3--N had just 2 mg · L-1 left in the effluent after 6 hours' reaction. In such a situation, The denitrification process could be performed both by nitrifiers and deni-trifiers simultaneously. Changing the COD concentration helps to find that the higher the COD concentration, the lower the efficiency of nitrogen removal. Thus, it can be proved that there must have existing the nitrification bacteria in the granular sludge. Under the condition of aeration (4 mgO2· L-1) and no carbon in the influent, the removing rate of NH4+-N could reach 75% after 6 hours reaction with the pH continuously decreased in the process. The result further reveals that the chemoautotrophic nitrifiers must have growing in the granular sludge in which the products of nitrification decreased the pH of broth. It can also be concluded that the aerobic granular sludge full of denitrification bacteria which can be cultivated in the inside of the granular. The reaction of denitrification produced alkali, which in turn can increase the pH of broth.