Microbial attachment to a solid surface is a universal phenomenon occurring in both natural and engineering systems and is responsible for various types of biofouling. Membrane systems have been widely applied in drinking water production, wastewater reuse, and seawater desalination. However, membrane biofouling is the bottleneck that limits the development of membrane systems. In this review, some biological control strategies of microbial attachment which would have great potential in alleviating membrane biofouling are discussed, including inhibition of quorum sensing system, nitric oxide-induced biofilm dispersal, enzymatic disruption of extracellular polysaccharides, proteins, and DNA, inhibition of microbial attachment by energy uncoupling, use of cell wall hydrolases, and disruption of biofilm by bacteriophage. It appears that biological control of microbial attachment would be a novel and promising alternative for mitigating membrane biofouling and would be a new research niche that deserves further study.

Anaerobic membrane bioreactors (AnMBRs) have recently gained consideration as an alternative technology for the treatment of municipal wastewater. Despite that, the effect of reactor configurations on their performance and sustainability remains understudied.This work aims to evaluate two different AnMBR types at low organic-loading conditions. Results show that the microbial consortium developed in each reactor can potentially have a significant impact on both biogas production and the microbial products that affect biofouling. Abstract 1Two lab-scale anaerobic membrane bioreactors (AnMBRs), one up-flow attached-growth 2 (UA) and another continuously stirred (CSTR), were operated under mesophilic 3 conditions (35 °C) while treating synthetic municipal wastewater (800 mg/L COD). Each 4 reactor was attached to both polyvinylidene fluoride (PVDF) and polyethersulfone (PES) 5 microfiltration (MF) membranes in an external cross-flow configuration. Both reactors 6were started-up and run under the same operating conditions for multiple steady-state 7 experiments. Chemical oxygen demand (COD) removal rates were similar for both 8 reactors (90-96%), but captured methane was found to be 11-18% higher for the CSTR 9 than the UA reactor. Ion Torrent sequencing targeting 16S rRNA genes showed that 10 several operational taxonomic units (OTUs) most closely related to fermentative bacteria 11 (e.g., Microbacter margulisiae) were dominant in the suspended biomass of the CSTR, 12 accounting for 30% of the microbial community. Conversely, methanogenic archaea 13 (e.g., Methanosaeta) and syntrophic bacteria (e.g., Smithella propionica) were found in 14 significantly higher relative abundances in the UA AnMBR as compared to the CSTR, 15 due to their affinity for surface attachment. Of the methanogens that were present in the 16 CSTR sludge, hydrogenotrophic methanogens dominated (e.g., Methanobacterium). 17 Measured EPS (both proteins and carbohydrates) -which has been broadly linked to 18fouling -was determined to be consistently lower in the UA AnMBR membrane samples 19 than in CSTR AnMBR membrane samples. Principal component analysis (PCA) based 20 on HPLC profiles of soluble microbial products (SMPs) further demonstrated these 21 differences between reactor types in replicate runs. The results of this study showed that 22 reactor configuration can significantly impact the development of the microbial 23

No abstract

Please cite this article as: Y. Xiong, M. Harb, P-Y. Hong, Characterization of biofoulants illustrates different membrane fouling mechanisms for aerobic and anaerobic membrane bioreactors, Separation and Purification Technology (2015), doi: http://dx.doi.org/10.1016/j.seppur. 2015.11.024 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThis study compares the membrane fouling mechanisms of aerobic (AeMBR) and anaerobic membrane bioreactors (AnMBR) of the same reactor configuration at similar operating conditions. Although both the AeMBR and AnMBR achieved more than 90% COD removal efficiency, the fouling mechanisms were different. Molecular weight (MW) fingerprint profiles showed that a majority of fragments in anaerobic soluble microbial products (SMP) were retained by the membrane and some AnMBR systems and can be applied to facilitate the development of appropriate fouling control strategies.