填料添加方式对MBR运行稳定性及膜污染特征的影响

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。

Influence of the filler addition method on characteristics of operation stability and membrane fouling in MBR

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.