1、城市污水常温处理中的新型改良 EGSB（膨胀颗粒污泥床）反应器的发展 1.材料和方法1.6 水动力特性有一种利用锂离子（Li +）的脉冲追踪仪，可以通过锂离子反应器中不同区域内停留的时间来分析水动力特性。在每一次试验中，通过脉冲注射器向进水中注入 10mL 浓度为 10mg/L 锂离子溶液，运用电感耦合等离子 ICP/脂肪醇聚氧乙烯醚硫酸盐 AES 外加铂金埃尔默奥普玛 2100 等离子发射光谱仪对污水中锂离子的浓度进行周期性检测。2 结果和讨论2.1 反应器的性能1）上升流速（V up）的影响。对于 EGSBc 和 EGSBm 两种反应器，上升流速对污水中 COD 和 CODfilt 浓度的
2、影响在图 2 中有说明。结果表明在 EGSBm和 EGSBc 两种污水中，当上升流速从 5.0 米/时( 阶段 3)到 10.3 米/时（阶段 5） ，CODfilt 浓度分别从 94.1 和 97.1 毫克/升（阶段 1）下降为 59.4 和 71.4 毫克/ 升（阶段 5）.两种反应器污水中 COD 浓度和 CODfilt 浓度变化趋势大致相同。在较高的上升流速下，通过比较两者污水中 COD 的浓度，显而易见，EGSB m 比EGSBc 具有更好的性能和恢复效果。当上升流速从 2 米/ 小时（阶段 1）到 10.3米/小时变化时，两种反应器中 SS 的浓度分别从 18.5 和 22.2 毫
3、克/ 升上升为60.1 和 126.5 毫克/升。从中我们看出在相同流速下， EGSBm 比 EGSBc 更容易造成生物量的流失。因此，EGSB m 具有较好的恢复能力是因为其高污泥浓度的保持能力。2)水力停留时间的影响。水力停留时间对 EGSBm 和 EGSBc 两种反应器中污水中COD 和 CODfilt 浓度的影响可以在图 3 中看出来。结果显示，在 EGSBm 反应器中，当水力停留时间从 6 降为 2 小时时，COD 和 CODfilt 浓度分别从 119.7 毫克/升和 94.1 毫克/升（阶段 1）下降为 104 和 82.6 毫克/升（阶段 7） 。当水力停留时间降为 1 小时后
4、，EGSB m 和 EGSBc 两者中 COD 和 CODfilt 浓度都有上升趋势。但是，EGSB m 有更好的基质清除效果，主要是因为它具有改进了的水循环结构。在 EGSBm 和 EGSBc 两种反应器中，挥发性脂肪酸的平均浓度分别从 28和 31 克/升（阶段 6，水力停留时间 4 小时）上升为 42 和 65 克/ 升（阶段 7，水力停留时间 2 小时） 。这就意味着在低水力停留时间内，EGSB m 比 EGSBc 更能有效利用挥发性脂肪酸来产生甲烷气体。3）有机负载率的影响。在两种反应器中，有机负载率对 COD 和 CODfilt 浓度的影响如图 4。当有机负载率由 7.2（阶段 8
5、）突然降为 1.2 千克 COD/（立方米*天） （阶段 9） ，EGSB m 反应器能维持它的处理效率不变，而 EGSBc 则发生不同程度的变化。当有机负荷率从 1.2（阶段 9）又调整到 7.2 千克 COD/（立方米*天）时，在阶段 10 的初期两种反应器中 COD 和 CODfilt 浓度都有明显提高。随后，EGSB m 恢复到最初有机去除效率需用 10 天时间，而 EGSBc 反应器在 20 天后任然没能达到最初的有机物去除率水平。显而易见，EGSB m 更能有效抵抗有机载荷的变化。总的来讲，当实验条件发生变化时，EGSB m 反应器中 COD，COD filt 和 SS浓度比 EG
6、SBc 中的浓度要低得多。即使 SS 浓度会随上升流速的升高而升高，但 EGSBm 比 EGSBc 的生物量流失少。而且在上升流速高达 10.3 米/ 小时时，EGSBm 反应器中污水 COD 含量几乎不变。2.2 颗粒污泥的分析这幅变形梯度凝胶电泳剖面图显示的是从 EGSBm 反应器中提取的 75 天和165 天颗粒污泥样本中 9-12DNA 片段。相比之下，我们可以从处理酸性污水的最初的接种污泥中提取第 15 号 DNA 片段。这些 DNA 片段分布在 16S 核糖核酸 RNA 的 V3 区段内，每个基因片段代表一种微生物种类。比较了不同污泥样品的变形梯度凝胶电泳（DGGE）剖面图，结果表
7、明,带1、2、3、4、9、10 的接种污泥也存在于第 75 天和第 165 天 EGSBm 污泥样品中,而其他的 9 个频段内的接种污泥很少见。相反,在 EGSBm 颗粒污泥的样品中出现了一些新的频段。频段的强度随不同的运行阶段和反应区域而变化。然而,微生物物种的数量在整个反应阶段和反应区域内并没发生明显变化。由于环境的变化,譬如循环比率,水力停留时间（HRT） ，有机负载率（OLR）和进水质量，微生物会选择性地形成稳定的微生物群落，通过竞争来有效地降解有机污染物。在 EGSBm 反应器运行 1,45,76 和 110 天，分别检测 A、B、C 、D 四个区域内颗粒污泥直径的变化。记录数据如图
8、 6。在第 1 天，接种污泥的直径均匀地分布在 0.8-2 毫米的范围内。在第 45 和 76 天，大部分颗粒污泥的直径分布在0.6-2 毫米范围内，而 A 和 B 区域也有一少部分颗粒污泥的直径分布在 0.01-0.4毫米范围内。在第 110 天，颗粒污泥的直径逐渐地变大。从中我们看到颗粒污泥在 EGSBm 中最初是分散的,随着反应条件的变化逐步聚集为厌氧微生物菌落。2.3 水动力特性当进水向上流动通过颗粒污泥床时，它将和该区域内污水混合（或分散到污水中） 。因此，对于理想的塞式流动应分散考虑，如下面所表达的停留时间分布（RTD）模型：在公式中，D/UL 表示无量纲的离散量，D 表示扩散系数
9、（平方米/小时） ，U 表示上升流速 Vup（米/小时） ，L 代表反应器的长度（米） 。对于理想的塞式流动反应器，D/UL 的值是 0。相反，对于理想的连续搅拌釜式反应器（CSTR） ，D/UL 的值趋近无穷大。通过脉冲示踪剂（例如，Li +）的方法，示踪剂浓度会随着试验时间在不同的水力停留时间发生变化，如图 7。依据图 7 的结果，经过计算和总结得出了表 3 中的数据，记录了在三种不同的上升流速下无关量 Vd和 D/UL 的值。对于 EGSBc 系统，在上升流速为 5 米/小时时，D/UL 最大可取 0.18 对应的Vd 的最小值取 10.13。当上升流速降为 2 米/小时时，D/UL 的
10、值会随之降低，意味着局部流动增强了。这与先前得出的结论一致，在 EGSBc 系统中，当上升流速超过 5 米/小时时，SS 的浓度会随上升流速的升高而升高（如图 2 所示） 。对于 EGSBm 系统，D/UL 的值会随 Vup 的增大而增大（ Vd 下降） 。在上升流速 Vup为 10.3 米/小时，V d 取值为 0.87%表明 EGSBm 系统能保持较好的水动力条件。这和前面在 EGSBm 污水中 COD 和 CODfilt 浓度数据结论一致（见图 2） 。当上升流速 Vup 上升时，EGSB m 的综合水动力特性有所提高，同时污泥流失得到控制，所以它对有机污染物的去除效果更明显。这再次证明
11、了改进型的 EGSBm 提高了污水处理效率。3 总结这项研究表明，在常温条件下，EGSB m 反应器通过混合液循环能更有效，更稳定地处理城市污水，相反，EGSB c 则采用污水回收的形式。EGSB m 比EGSBc 更能有效地处理污水中的 COD、COD filt 和 SS。在较高的上升流速情况下，EGSB c 比 EGSBm 颗粒污泥流失情况严重。在 EGSBm 系统中，纵贯整个反应过程，不管污水水质的变化和流体力学特性，厌氧生物都保持一个稳定的生物群落，这样就能保证有效降解有机污染物。在 EGSBm 反应开始后，一小部分颗粒污泥通过分解，新的颗粒污泥厌氧微生物逐步聚集起来进而适应反应条件。
12、运用流体停留时间模型对水力特性分析显示，在 EGSBm 系统中，D/UL 的值会随上升流速 Vup 的增加而增加。V d 低至 0.87%上升流速 Vup 是 10.3 米/小时对应的 D/UL 值为 0.15。然而，在 EGSBc 系统中，当上升流速 Vup 是 5 米/小时时，D/UL 的最大值是 0.18。在 EGSBc 系统中，无论 Vup 是增大还是减小，都会导致 D/UL 值的减小，主要是因为混合不充分进而增强了局部流动。在EGSBm 系统中，良好的水动力条件确保了在较高流速情况下污水处理的效率。development of a novel modified EGSB reacto
13、r for municipal sewage treatment at ambient temperatures 1.6 Hydrodynamic Characteristics A pulse tracer,Li+ was used to analyze the retention time distribution in the reactor.In each analysis,10 mL of 10 mg/L Li+ was introduced into the influent through pulse injection and its concentration in the
14、effluent was determined periodically by ICP/AES coupled with a PerkinElmer Optima 2100 DV plasma emission spectrometer. 2 Results and Discussions 2.1 Reactor Performance 1)Effect of VupThe effect of Vup on the COD and CODfilt concentrations of the EGSBc and EGSBm effluents is shown in Fig.2.Results
15、indicate that the mean concentrations of CODfilt of the EGSBm and EGSBc effluents decreased from 94.1 and 97.1 mg/L(P1)to 59.4 and 71.4 mg/L(P5),respectively,when the Vup increased from 5.0 m/h(P3)to 10.3 m/h(P5). Effluent COD concentration of the two reactors had the same trend as CODfilt concentra
16、tion.The EGSBm exhibited a much better performance and restorability at a high Vup than the EGSBc ,as reflected by the COD dataThe SS concentrations of the EGSBm and EGSBc .effluents increased significantly from 18.5 and 22.2 mg/L to 60.1 and 126.5 mg/L,respectively,as the Vup increased from 2 m/h(P
17、1)to 10.3 m/h(P5).It is seen that much less biomass was washed out of EGSBm than EGSBc under identical conditions.Therefore, the better restorability of the EGSBm ，could be ascribed to its high sludge concentration maintained. 2)Effect of HRT.The effect of HRT on the COD and CODfilt concentrations o
18、f EGSBcand EGSBm effluents is shown in Fig.3.Results indicate that the mean concentrations of COD and CODfilt of the EGSBm effluent decreased from 119.7 and 94.1 mg/L(P1)to 104 and 82.6 mg/L(P7),respectively,when the HRT significantly decreased from 6to 2h.Similarly,the meanconcentrations of COD and
19、 CODfilt of the EGSBc effluent decreased from l22.7 and 97.1 mg/L(P1) to 113.3 and 91.5 mg/L(P7),respectively.As the HRT further decreased to 1 h,the COD and CODfilt concentrations of both EGSBm and EGSBc effluents increased rapidly.However,the EGSBm always achieved higher substrate removal efficien
20、cies than the EGSBc due to its modified recirculation mode. The mean concentrations of VFA of both EGSBm and EGSBc effluents increased rapidly from 28 and 31 g/L(P6，HRT 4 h)to 42 and 65 g/L(P7，HRT 2 h),respectively.This implies that the VFA was used more rapidly for methane generation in EGSBmthan E
21、GSBc at low HRT values. 3）Effect of OLR.The effect of OLR on the COD and CODfilt concentrations of the EGSBm and EGSBc effluents is shown in Fig.4.When the OLR suddenly decreased from 7.2(P8)to 1.2 kgCOD/(m3d)(P9), the EGSBm almost maintained its treatment efficiency, while the treatment efficiency
22、of the EGSBc was improved to some extent.When the OLR was adjusted from 1.2(P9) back to 7.2 kgCOD/(m3d)(P10),a rapid increase of the COD and CODfilt concentrations of both EGSBm and EGSBc effluents was observed during the initial period of P10.Thereafter,the EGSBm approximately restored its organic
23、removal efficiency within 10 d,but the EGSBc failed to regain its removal efficiency even after 20 d.This clearly indicates that the EGSBm is more resistant to shock organic loadings.In general,the COD,CODfilt and SS concentrations of the EGSBm effluent was notably lower than those of the ECSBc effl
24、uent when the experimental condition(e.g.,Vup , HRT,and OLR)was changed.Although the SS concentrations of both EGSBm and EGSBc effluents increased with the increasing Vup,the EGSBm always washed out much less biomass than the EGSBc .The COD concentration of the EGSBm effluent was maintained quite st
25、able even at a Vup value as high as 10.3 m/h.2.2 Granular Sludge Analysis The DGGE profiles showed that 9-12 DNA snippets were extracted from the 75 d and 165 d granular sludge samples of the EGSBm . In comparison,15 DNA snippets could be extracted in total from the original inoculation sludge treat
26、ing citric acid production wastewater(as shown in Fig.5).These DNA snippets distributed in the V3 section of the 16SrDNA gene with each snippet representing one microbial species.Comparing the DGGE profiles of different sludge samples. the results demonstrate that Bands 1,2,3, 4,9,10 of the inoculat
27、ion sludge were also present in the 75 d and 165 d sludge samples of EGSBm ,while other 9 bands of the inoculation sludge were seen few . In contrast, a few new bands appeared in the granular sludge samples of the EGSBm .Some band intensities varied with different operation phases and reaction regio
28、ns. However, the number of microbial species remained similar regardless of operation phase and reaction region in the EGSBm .Due to environmental changes such as recirculation percentage,HRT,OLR and influent quality, the microorganisms would selectively form a stable microbial community through com
29、petition to effectively degrade organic pollutants The diameter change of the granular sludge in regions A,B,C and D of the EGSBm was inspected at 1,45,76 and 110 d after the reactor was started up, as shown in Fig.6. At 1 d,the diameters of the seed sludge in all regions distributed quite uniformly
30、 in the range of 0.8-2 mm. At 45 and 76 d,most granular sludge remained in the diameter range of 0.6-2 mm . while a small portion of granular sludge in Regions A and B disaggregated and distributed in the diameter range of 0.010.4 mm .At 110 d, the diameter of granular sludge was gradually increased
31、.It is seen that the granular sludge in the EGSBm was first disaggregated during the early period of operation, and then gradually aggregated as the anaerobic microorganisms were acclimated to the operational conditions. 2.3 Hydrodynamic Characteristics When the influent flowed upward through the gr
32、anular sludge bed,it would mix with(or disperse into)local wastewater.Therefore,the hydrodynamics of an ideal plug-flow should take dispersion into consideration,as expressed by the following residence time distribution(RTD)model： where D/UL is the dimensionless dispersion number, D denotes the coef
33、ficient of diffusion(m2 /h),U equals Vup(m/h),and L represents the length of reactor(m). For an ideal plug-flow reactor,the value of D/UL equals zero.On the contrary,for an ideal continuous stirred tank reactor(CSTR),the value of D/UL approaches infinity.Through the pulse tracer (i.e.,Li+)method, th
34、e tracer concentration changes along with the experimental time under different HRT were shown in Fig.7.Based on the results of Fig.7, the values of inutility volume(Vd )and D/UL at three different upflow liquid velocities were calculated and summarized in Tab.3. For the EGSBc,a maximal D/UL of 0.18
35、 which corresponded to a minimal Vd of 10.13 was observed at the Vup of 5 m/h.As the Vup decreased to 2 m/h, the D/UL value decreased,implying insuficient hydrodynamic mixing. As the Vup increased to 10.3 m/h,the D/UL value also decreased, implying enhanced short-flow.This agrees with the previous r
36、esult that the SS concentration of the EGSBc effluent increased rapidly when the Vup exceeded 5.0 m/h(as shown in Fig.2). For the EGSBm, the D/UL kept increasing(or the Vd kept decreasing)with the increasing Vup.The Vupvalue of 0.87% at the Vup of 10.3 m/h indicated a favorable hydrodynamic conditio
37、n maintained in the EGSBm. This agrees with the previous results of COD and CODfilt concentrations of the EGSBm effluent(as shown in Fig.2).As the Vup increased,the hydrodynamic mixing of the EGSBm was enhanced while the sludge washout was controlled, leading to an improved removal efficiency of org
38、anic pollutants.This demonstrates again that the modified recirculation of the mixed liquid in the EGSBm improved the treatment eficiency of municipal wastewater. 3 Conclusions This study showed that municipal sewage could be treated eficiently and stably with the EGSBm reactor through recirculating
39、 its mixed liquid at ambient temperatures,by contrast,effluent recycling was adopted by EGSBc. The EGSBm could achieve improved treatment efficiencies in terms of COD,CODfilt and SS in comparison with the EGSBc .The washout of granular sludge from the EGSBm was much less than that from the EGSBc at
40、high Vup values. Throughout the reactor height, anaerobic microorganisms maintained a stable microbial community in the EGSBm regardless of the changes of wastewater quality and hydrodynamic characteristics. thus ensuring the effective degradation of organic pollutants. Though a small portion of gra
41、nular sludge disaggregated after the EGSBm reactor was started up,new granular sludge gradually aggregated as the anaerobic microorganisms were acclimated to the operational conditions. The hydrodynamic analysis using the RTD model revealed that the D/UL of the EGSBm kept increasing as the Vup incre
42、ased.The Vd was as low as 0.87% at the Vup of 10.3 m/h which corresponded to a D/UL value of 0.15.However,the maximal D/UL(0.18)for the EGSBc was found at the Vup of 5 m/h.Either decreasing or increasing the Vup in the EGSBc would result in a decrease of the D/UL due to insuficient mixing or enhanced short-flow.The favorable hydrodynamic condition obtained in the EGSBm helped to achieve an enhanced treatment eficiency at high Vup values.
