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生物制药废水是一种难处理的高浓度有机废水,具有成分复杂、冲击负荷大、有机物含量高、可生化性差、色度深和毒性强等特点[1]。视生产工艺不同,生物制药废水往往还含有高浓度氨氮。膜生物反应器(membrane bioreactor,MBR)因其具有污泥停留时间长、污泥产量低和出水水质好等优点[2],近年来已成为生物制药废水处理领域的首选工艺之一。然而,膜污染一直是制约MBR工艺广泛应用的主要因素。
已有研究[3]表明,优化操作条件、改善混合液特性和开发膜材料等方法可缓解膜污染进程。其中,添加填料是一种能够快速、有效改善混合液特性并缓解膜污染的方法[4]。HAZRATI等[5]在研究传统MBR(R1)与膜区添加悬浮聚乙烯填料的MBR(R2)对膜污染特征的影响时发现,在反应器运行第95天,R1和R2的跨膜压差(trans-membrane pressure,TMP)分别为12 kPa和5 kPa,滤饼层阻力分别为12.15×1011 m−1和5.83×1011 m−1,污泥颗粒平均粒径分别为44 μm和119 μm。这表明膜区添加填料能够增大污泥粒径,降低滤饼层阻力,进而改善膜污染。RAFIEI等[6]在生物包封膜生物反应器(bio-entrapped membrane bioreactor,BE-MBR)膜区添加聚氨酯填料,发现BE-MBR的膜运行周期为21 d,其溶解性微生物代谢产物(soluble microbial products, SMP)中蛋白质的浓度为33.1 mg·L−1,比传统MBR(conventional membrane bioreactor, CMBR)膜运行周期延长17 d,蛋白质浓度降低164.6 mg·L−1。这表明膜区添加填料能够降低膜表面蛋白质的黏附,延长膜运行周期。朱逸舟等[7]将悬浮聚乙烯填料加入到A2O-MBR的好氧区中,发现有机负荷从0.66 kg·(m3·d)−1增加至1.98 kg·(m3·d)−1时,出水COD、
${\rm{NH}}_4^ + $ -N和TN浓度均能保持在50、5和15 mg·L−1以下,系统表现出良好的运行稳定性。填料种类及其添加方式对缓解膜污染有重要作用。CHENG等[8]指出,悬浮型填料具有流化效果好、比表面积大、孔隙率高、附着生长的生物量较多、耐受反应器中有毒化合物的能力强等优点,在MBR中应用广泛。宋咏等[9]认为,软质聚氨酯悬浮填料和硬性聚乙烯悬浮填料能够有效降低膜阻力,提高膜组件的过滤性能。现阶段,填料添加方式主要为单一好氧区添加[10]或膜区添加[11],不同添加方式(好氧区和膜区同时添加填料)对污染物去除特征、运行稳定性和膜污染特征的相关研究鲜见报道。本研究旨在开发一种复合型悬浮生物膜强化膜生物反应器(hybrid suspended biofilm enhanced-membrane bioreactor,HSBE-MBR),通过在MBR不同区域(缺氧区、好氧区和膜区)添加悬浮填料,分析典型污染物的去除特征、SMP和胞外聚合物(extracellular polymeric substances,EPS)浓度及其组分变化、污泥粒径分布特征等,研究填料添加方式对处理效果、运行稳定性及膜污染特征的影响,分析膜污染机理,优化填料添加方式,为生物制药废水实现稳定化处理提供参考。
填料添加方式对MBR运行稳定性及膜污染特征的影响
Influence of the filler addition method on characteristics of operation stability and membrane fouling in MBR
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摘要: 为提高MBR的去除性能并延缓膜污染,采用复合型悬浮生物膜强化膜生物反应器(hybrid suspended biofilm enhanced membrane bioreactor, HSBE-MBR)处理生物制药废水,考察了填料添加方式对HSBE-MBR中典型污染物的去除特征、运行稳定性及膜污染特征的影响,并分析了膜污染机理。结果表明:缺氧区和好氧区添加填料时(工况1),TCOD、
${{\rm{NH}}_4^ + }$ -N和TN平均去除率分别为91.61%、97.08%和79.40%;缺氧区、好氧区及膜区添加填料时(工况2),TCOD、${{\rm{NH}}_4^ + }$ -N和TN平均去除率分别为91.09%、97.24%和83.66%。在上述2种工况下,HSBE-MBR对TCOD、${{\rm{NH}}_4^ +} $ -N和TN均具有良好的去除性能,且运行稳定性良好,工况2中TN去除率提高了4.26%。在工况1下,膜运行时间为0.02~8.17 d;在工况2下,膜运行时间为0.26~138 d。2种工况下的膜污染机理均以滤饼层污染为主,滤饼层阻力占比分别为94.7%和90.1%;膜区添加填料能够减缓膜表面滤饼层的形成,使滤饼层阻力降低8.07%;同时,混合液中溶解性微生物代谢产物(soluble microbial products, SMP)、松散结合EPS (loosely bound-EPS, LB-EPS)和紧密结合EPS (tightly bound-EPS, TB-EPS)浓度分别由(63.70±12.95)、(13.97±2.03)和(153.82±12.64) mg·g−1(工况1)降低为(31.77±3.17)、(9.11±0.40)和(78.12±18.92) mg·g−1(工况2)。粒度分布测定结果表明,膜区添加填料后,污泥平均粒径从31.35 μm(工况1)增大至34.71 μm(工况2)。根据污染物去除特征及膜污染特征,确定最优添加方式为在缺氧区、好氧区和膜区添加填料。上述研究结果可为提高MBR运行稳定性并改善膜污染提供参考。-
关键词:
- 复合型悬浮生物膜强化膜生物反应器(HSBE-MBR) /
- 生物制药废水 /
- 填料添加方式 /
- 膜污染 /
- 混合液性质
Abstract: To improve MBR removal performance and alleviate membrane fouling, the hybrid suspended biofilm enhanced-membrane bioreactor (HSBE-MBR) was employed for biopharmaceutical wastewater treatment. The aim of the study was to explore the effect of the filler addition method on the removal characteristics of typical pollutants, operation stability and membrane fouling and to determine the membrane fouling mechanism. Results showed that the average removal efficiencies of TCOD,${\rm{NH}}_4^ + $ -N and TN were 91.61%, 97.08% and 79.40%, respectively when the fillers were added in the anoxic and oxic zone (condition 1). The average removal efficiencies of TCOD,${\rm{NH}}_4^ + $ -N and TN were 91.09%, 97.24% and 83.66%, respectively when the fillers were added in the anoxic, oxic and membrane zone (condition 2). Under above two conditions, HSBE-MBR had good performance on TCOD,${\rm{NH}}_4^ + $ -N and TN removal, and maintained the good operation stability, TN removal efficiency increased by 4.26% under condition 2. HSBE-MBR operation time increased from 0.02~8.17 d (condition 1) to 0.26~138 d (condition 2). Cake formation was identified as the main membrane fouling mechanism under conditions 1 and 2, and their cake resistance ratios were 94.7% and 90.1%, respectively. The fillers added in membrane zone could effectively mitigate the cake formation on the membrane surface, and reduce the cake resistance by 8.07%. Meanwhile, the concentrations of soluble microbial product (SMP), loosely bound-EPS (LB-EPS) and tightly bound-EPS (TB-EPS) in the sludge mixed liquor were reduced from (63.70±12.95), (13.97±2.03) and (153.82±12.64) mg·g−1 (condition 1) to (31.77±3.17), (9.11±0.40) and (78.12±18.92) mg·g−1 (condition 2), respectively. The result of particle size distribution showed that the average particle size of the sludge increased from 31.35 μm (condition 1) to 34.71 μm (condition 2) when adding the fillers in the membrane zone. According to the characteristics of pollutants removal and membrane fouling, the optimal method of the fillers addition is to add them in the anoxic, oxic and membrane zone. This provides the reference for further improvement of the operation stability and membrane fouling alleviation of MBR. -
表 1 原水水质
Table 1. Raw water quality
工况 取样次数n 项目 质量浓度/(mg·L−1) TCOD ${\rm{NH}}_4^ + $ -N${\rm{NO}}_3^ - $ -N${\rm{NO}}_2^ - $ -NTN 1 20 范围 2 652.26~7 483.91 291.41~630.22 12.89~45.50 0~14.29 317.49~653.16 平均值±标准差 4 034.49±1 238.23 394.49±88.55 21.25±6.96 1.34±3.15 417.08±89.72 2 44 范围 1 903.07~5 026.94 191.02~662.29 0.57~52.89 0~1.90 204.09~681.86 平均值±标准差 3 317.34±698.34 413.14±95.61 16.99±7.92 0.22±0.39 430.34±96.18 表 2 不同工况下的膜阻力分布特征
Table 2. Characteristics of membrane resistance distribution at different operation conditions
阻力
类型工况1 工况2 膜阻力/(1011 m−1) 占比/% 膜阻力/(1011 m−1) 占比/% Rm 0.71 1.7 0.54 1.4 Rp 1.49 3.6 3.42 8.5 Rc 39.28 94.7 36.11 90.1 Rt 41.48 100 40.07 100 -
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