MBR流场、传质与能耗的相互关系研究

Considering the water shortage and urgent requirement of water treatment and reuse in China, the membrane bioreactor (MBR) has been proven as a promising technology in waste water treatment and water reuse. However, one of the major challenges for spreading application of MBR at large scales is high energy consumption, and there is a missing gap between high energy consumption and flow dynamics in MBR. Therefore, the purpose of this study is to therotically develop MBR with lower energy consumption through flow dynamics. In this study, a high-precision simulation platform by integrating biochemical reaction formulations and functions in the activated sludge model, ASM3, into the computational fluid dynamics (CFD) software.The mass transfer-reaction model of CFD will be calibrated using MBR at bench- and full scales. Based on the developed platform, the characteristics of flow field in MBR will be simulated by CFD models coupled with ASM3 under conditions of different processes, geometry, membrane module configurations and operational conditions. The relationships among mass transfer, energy consumption and mechanism for high energy consumption in MBR operation will be well revealed based on simulations under multiple conditions, and the results obtained from this study are expected to provide useful guidance for design, operation, practical application of new MBR with lower energy consumption.

面对我国水短缺、污水资源化对膜生物反应器（MBR）的迫切需求，针对MBR运行能耗高，且引起MBR运行能耗高的内在水力学特征尚未充分知晓的科学问题，以低能耗化MBR创新研究为目的，以功能不断强化的计算流体力学(CFD)软件为研究依托，将活性污泥模型ASM3生物化学反应模型与CFD传质-反应模型相契合，通过小试和实际工程的调试与校正，建立适宜进行MBR流场高精度模拟的传质-反应模型模拟平台；并以该平台为基础，对不同工艺、几何尺寸、不同膜组器构型和不同MBR运行状况，进行MBR各单元流场的CFD模拟；通过多条件的反复模拟，揭示MBR流场、传质、能耗之间相互关系及高运行能耗的原因；给出新型低能耗化MBR研制的途径、设计、安装和运行指导方案；为引领新型低能耗MBR研发、设计、建造和运行提供科学依据和技术支持。

本课题针对减轻膜生物反应器（MBR）膜污染、降低其运行能耗的迫切需求，采用计算流体力学方法（CFD）与活性污泥模型（ASM）耦合模型手段，对不同规模MBR流场、传质、能耗进行模拟、优化研究。模型参数通过小试和实际工程的调试与校正的同时，广泛运用颗粒成像测速（PIV）、流场示踪技术、超声多普勒测速等流场测试技术进行模型验证。拟通过模拟发现MBR高能耗原因，进而提出新型低能耗MBR的结构和操作条件的科学原理和研制方法。.研究发现当 D/L=22.2%时， H 循环管内平均循环流速最大； 推导得出 H 循环管内流速计算公式。结构优化后MBR膜面平均剪切力达1.2 Pa （曝气量1.0 m3 h-1，MLSS 7500 mg L-1，气泡直径2.48 mm）；经响应面分析（RSM）设计多目标优化后，MBR膜面剪切力达2.18 Pa，较单目标优化提高71.7%，同时颗粒在膜面沉降概率为1.49 ×10-4，较单目标优化下降70.9%。确定最优操作条件为曝气量2.0 m3 h-1，MLSS 8820 mg L-1，气泡直径4.88 mm。.确定500 t/d规模MBR最佳气水比为20:1；曝气管采用错位平行布置方式最优，两侧膜片剪切力明显改善；推荐污泥浓度为6000~10000 mg L-1；最佳膜片间距为20~30 mm，此装填密度较大，建设成本低，同时能防止未超过商业MBR装填极限，不易发生局部堵塞。.安全液位超高为400 mm左右。商业中空纤维膜组件的安全浸没高度在300~500 mm，个别膜组件大于500 mm。本研究发现不同安全液位高度（100~500 mm）对膜面剪切力的影响较小，400 mm时膜面剪切力最大，故选用400 mm作为推荐值。.A2/O-MBR不同工艺段微生物群落结构存在一定差异，而在不同的SRT下，A2/O-MBR的微生物群落结构相似性显著降低。内回流比由200%提高至300%，污泥停留时间由25天调整至50天，微生物群落结构发生明显变化，丰度上升，系统脱氮效率提高33.3%，剩余污泥量减少61.7%。.经结构和操作参数优化后，MBR及其组合工艺抗膜污染性能和脱氮效率明显改善。为实际规模MBR设计和运行提供了坚实的科学依据和技术支撑。