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在传统的活性污泥法中,功能微生物生长容易受到环境条件的影响。有研究[1]表明,向反应器中添加载体,可以为微生物提供更多的附着点,微生物会与载体耦合形成稳定的微生物复合体,从而增加污染物的截留与功能微生物的持留效果,能够显著提高反应器的微生物生物量和耐冲击能力[2],可以充分发挥其原有的效率和优势,使得出水水质更稳定。
微生物在载体表面的增殖生化过程主要受到载体表面孔道结构分布的影响,复合微生物体形成的关键在于载体的选择[3]。最初的载体主要是鹅卵石、玻璃颗粒等颗粒状的材料[4],但随着生物膜的生长,颗粒载体的空隙会逐渐被堵塞,从而影响到载体内部的物质转化,因而近年来相关研究在选择载体时,会优先考虑具有较大孔隙、良好亲水性和生物亲和性的材料[5]。EROL等[6]利用壳聚糖纳米粒子作为载体固定漆酶,可以去除水溶液中96%的苯酚。TING等[7]使用藻酸盐-EM(功能微生物)复合微生物体系去除水中的铅(Pb),对于Pb的去除量可达4.011 mg·g−1。VANOTTI等[8]利用聚乙烯醇颗粒作为载体固定硝化污泥,
${\rm{NH}}_4^ + - {\rm{N}}$ 硝化速率为567 mg·(L·d)−1。但是,现有研究中常见的载体材料属于聚合化学物质,只能通过加工获得,成本较高[9]。因此,有必要寻找出性能稳定合适且价格低廉的载体。活性炭是一种廉价易得的材料[10],具有丰富的孔隙结构,常被应用于吸附研究中,将其作为微生物载体具有一定的可行性。王真真等[11]固定微生物的研究结果表明,活性炭纤维的使用可以有效减少微生物损失;练文标[12]发现添加粉末活性炭的序批式活性污泥反应器在污泥驯化成熟稳定后,废水COD平均去除率可增加至90%,比普通反应器提高了10%,反应器的耐负荷冲击能力显著提高,其污泥膨胀和生物泡沫问题也得到了有效解决。WU等[13]发现,活性炭分子链上分布了大量的羟基、羧基等活性基团,对水体中带正电荷的污染物具有良好的络合吸附和絮凝作用,这些基团同样有利于细胞粘附和增殖[14-15]。因此,活性炭可以作为一种合适的生物膜载体,在降低成本的同时亦能更好地发挥复合生物体的优势[16]。此外,针对活性炭对微生物种群构成产生的影响进行系统性地研究,目前鲜有报道。
因此,根据课题组前期预实验,本研究选取中孔发达且比表面积较大的150目煤质活性炭作为孔隙尺寸和颗粒粒径较为合适的载体材料,在传统的序批式活性污泥反应器(sequencing batch reactor,SBR)中投加煤质活性炭构建活性污泥体系,通过对比实验组(投加材料)与对照组(不投加材料)的SBR在脱氮性能、复合微生物体表面形态和内部结构、反应器中EPS 含量及其主要微生物种群结构组成和关键脱氮除磷菌群的区别,探究了微生物体耦合活性炭在传统SBR中的脱氮增效机制,以期为强化生物脱氮提供参考。
利用微生物耦合载体提升传统SBR工艺脱氮的有效性
Utilizing microbial- carrier coupled system to improve the effectiveness of nitrogen removal by traditional SBR process
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摘要: 功能微生物的种类、稳定性以及增殖率对污水处理厂活性污泥单元工艺效果有重要影响。利用特定孔隙率的活性炭作为载体,与筛选得到的功能微生物可以较好地耦合,构成新型复合微生物体,可显著提高SBR反应器的脱氮效果。本实验在序批式活性污泥反应器(SBR)中投加孔较为发达的150目煤质活性炭构建微生物耦合载体活性污泥系统(R2),以不加任何载体的单独活性污泥系统作为对照组(R1)。经SEM和TEM观察表明,R1中微生物较为分散,而R2中的微生物可以在活性炭表面和孔隙内部呈团聚状富集。连续流实验结果表明,R2中的污泥在45 d后基本驯化稳定,且污泥膨胀较小,出水中
${{\rm{NH}}_4^ +} $ -N和TN的去除率分别为(81.92±2.52)%和(56.44±2.56)%,脱氮效果明显优于对照组R1的(43.56±1.66)%和(39.96±3.69)%。R2反应器中胞外聚合物(EPS)的含量由147.56 mg·g−1(以VSS计)增加至416.33 mg·g−1(以VSS计),且蛋白质和多糖比值高于R1,说明微生物耦合活性炭有利于污泥的颗粒化和颗粒污泥系统的稳定。从微生物作用机理的角度开展研究,发现R2中Proteobacteria (83.79%),Bacteroidetes (9.34%), Firmicutes (2.87%)的相对丰度较高,且相比于R1,R2中和污泥膨胀相关的菌门Actinobacteria的丰度下降,而与脱氮功能有密切关联的菌属Enterobacter (25.11%)、Azohydromonas(14.24%)和Microbacterium(8.38%)的丰度上升。以上研究结果说明,合适的载体能够提高功能微生物在水处理中的增效作用和稳定性。Abstract: The type, stability and proliferation rate of functional microorganisms have an important influence on the process effect of the activated sludge unit of the sewage treatment plant. This study found that activated carbon with a specific porosity as a carrier could couple with the functional microorganisms screened in this study and form a new type of composite microorganism, which significantly improved the denitrification effect of the SBR reactor. A novel microbial-carrier coupled activated sludge process (named as R2) was constructed by adding150 mesh of coal-based activated carbon in a sequential batch activated sludge reactor (SBR) in order to improve nitrogen removal performance in the traditional activated sludge process. At the same time, the traditional activated sludge system without any carrier addition was taken as the control group (named as R1). SEM and TEM images indicated that the microorganisms can be enriched in agglomerated form on the surface and preliminary interior of activated carbon in R2, while the microorganisms in R1 were relatively scattered. The results of continuous flow experiment indicated that the domestication of sludge was basically stable and low bulking after 45 days in R2, and the${\rm{NH}}_4^ + - {\rm{N}}$ and TN removal efficiencies were (81.92±2.52)% and (56.44±2.56)%, respectively, which were much higher than (43.56±1.66)% and (39.96±3.69)% in R1, respectively. The study on microorganisms showed that the content of extracellular polymeric substances (EPS) in R2 increased from 147.56 mg·g−1 (calculated by VSS) to 416.33 mg·g−1 (calculated by VSS), while the ratio of protein (PN) to polysaccharide (PS) was higher than R1, indicating that the microbial-carrier coupled activated sludge process was beneficial to sludge granulation and the stability of granular sludge system. From the perspective of microbial action mechanism, it was found that the relative abundance of Proteobacteria (83.79%), Bacteroidetes (9.34%), and Firmicutes (2.87%) in R2 were higher than R1, while the abundance of Actinobacteria related to sludge bulking decreased, the abundance of Enterobacter (25.11%), Azohydromonas (14.24%) and Microbacterium (8.38%) closely related to the denitrification function increased. This study confirms that a suitable carrier can effectively improve the synergistic effect and stability of functional microorganisms in water treatment. -
表 1 SBR反应器的运行方案
Table 1. Operation scheme of SBR reactor
运行阶段 运行周期/d 溶解氧/(mg·L−1) pH 温度/℃ 阶段Ⅰ 0 ~ 8 1.50~2.20 7.1±0.2 25±2 阶段Ⅱ 9 ~ 25 1.15~3.30 7.1±0.2 25±2 阶段 Ⅲ 26 ~ 45 2.30~2.50 7.1±0.2 25±2 表 2 模拟废水的
-N与TN平均去除率${\bf{NH}}_4^ + $ Table 2. Average removal rate of
-N and TN in simulated wastewater${\rm{NH}}_4^ + $ % 反应器 阶段 Ⅰ平均去除率 阶段 Ⅱ平均去除率 阶段 Ⅲ平均去除率 -N${\rm{NH}}_4^ + $ TN -N${\rm{NH}}_4^ + $ TN -N${\rm{NH}}_4^ + $ TN R1 58.82 ± 3.51 43.36 ± 5.54 48.12 ± 2.87 31.35 ± 1.21 43.56 ± 1.6 39.96 ± 3.69 R2 55.34 ± 5.23 39.93 ± 1.92 53.34 ± 1.72 45.28 ± 2.14 81.92% ± 2.52 56.44 ± 2.56 表 3 不同载体对SBR污泥驯化稳定时长与氮去除效果的比较
Table 3. Comparison of the stabilization time of sludge acclimation and nitrogen removal effect of SBR with different carriers
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