生物活性炭耦合膜生物反应器处理抗生素类水污染物的传质机理研究

Nowadays, antibiotics have been globally recognized as an urgent pollutant discharged to water cycle considering the risk of the resistance spread, due to their huge production and usage. Therefore, this project will develop a novel system combining advantages of adsorption, biodegradation and membrane separation, for the purpose of efficient and sustainable treatment of antibiotic-bearing wastewater, i.e., biofilm-covered granular activated carbon (BGAC) technology will be integrated in membrane bioreactor (MBR) with continuous influent spiked with antibiotic. Firstly, performance of the BGAC-MBR system will be evaluated and optimized in terms of antibiotic rejection, effluent flux and so on. Secondly, transport and transition processes of the target antibiotic, such as biodegradation, adsorption and diffusion, will be examined through the coupled batch kinetic experiments. Moreover, physical and microbial characteristics of those biofilms will be looked into using molecular biology techniques, and thereafter correlated to the antibiotic transfer processes, respectively. Finally, a reasonable mathematic model will be proposed for describing the overall BGAC-MBR process, based on conventional mass transfer equations (e.g. the Monod's) and their alignments referring to the above experimental studies. It is expected that the results of this project will provide a solid technical and theoretical foundation for full-scale application of BGAC-MBR in industry, which in turn can help solve problems caused by antibiotics emission in aquatic environment.

随着全球大量生产和使用抗生素，流入水循环圈的废弃抗生素不断增多，由此产生耐药性扩散等严重危害。因此，本申请项目将开发一个综合吸附、降解和膜分离优势的新型系统，实现高效率、持续性处理含抗生素废水的目的。首先，将长有生物膜的活性炭即生物活性炭（BGAC）与膜生物反应器（MBR）整合，形成连续运行的BGAC-MBR耦合系统，通过抗生素去除率、出水通量等指标对系统性能进行评估和优化。其次，配合分批动力学实验，找出抗生素在BGAC-MBR中降解、吸附和扩散的传质规律。然后，对生物膜的菌群分布和结构属性进行分子生物学表征，并和抗生素迁移转变过程进行关联。最后，结合以上实验结果，对Monod方程等传统模型进行修正，建立一个合理描述抗生素在BGAC-MBR中传质过程的机理模型。本项目研究成果将为BGAC-MBR工业化应用提供坚实的技术和理论基础，促进解决抗生素类水污染物造成的环境问题。

本项目针对污水中的微量抗生素这一新兴污染物，提出了一个综合吸附、降解和膜分离优势的BGAC-MBR处理系统，即利用长有生物膜的活性炭即生物活性炭（BGAC）与膜生物反应器（MBR）整合，实现高效率、持续性处理含抗生素废水的目的。项目首先考察BGAC-MBR反应器运行效果，结果发现微量抗生素对污泥生长并无明显抑制作用乃至对污泥的生长具有刺激作用，同时污泥对其也具有一定的耐受能力，MBR反应器可以正常运行，COD平均去除率达95%，污泥进过驯化后抗生素去除率接近100%，加入BGAC能通过减少菌体在膜面沉积而有效控制膜污染方面，通过改进胞外DNA提取方法分析发现，MBR能很好的截留耐药菌和胞内抗性基因，但渗出的菌群中耐药菌比例增大且出水含有胞外抗性基因，因此对耐药性风险控制问题需要进一步研究。其次，本项目探究了该系统的传质反应机理，发现BGAC-MBR去除抗生素的主要机理是微生物降解机制，并找出不同抗生素条件下的特征功能性微生物种属，GAC吸附符合混合级数动力学模型，生物膜的吸附作用可以忽略，其作用是增加了3-28%的滤膜阻力，通过拦阻扩散原理提高出水中抗生素的去除率，也可使GAC实现生物再生。最后还对系统剩余污泥进行了资源化处理，发现可以通过VFA-PHA两段式工艺实现污泥处置和获得可降解生物塑料PHA的双重目的，通过调控VFA奇偶碳成分可调节PHA含量，剩余污泥以月桂酸为唯一碳源时可以进一步获得高值第三代PHA产品。本项目研究成果为BGAC-MBR 工业化应用提供了有益的技术参考，促进解决抗生素造成的水污染问题。