Behaviour of biopolymeric substances in the activated sludge of an MBR system working with high hydraulic retention time

Abstract

This study was undertaken to analyse the activated sludge of a membrane bioreactor (MBR), the behaviour of extracellular polymeric substances (EPS) and soluble microbial products (SMP) as well as their biopolymers composition, in the activated sludge of a membrane bioreactor (MBR) and their influence on membrane fouling were analysed. For the experiment an experimental fullscale MBR working with real urban wastewater at high hydraulic retention time with a variable sludge-retention time (SRT) was used. The MBR system worked in denitrification/nitrification conformation at a constant flow rate (Q = 0.45 m/h) with a recirculation flow rate of 4Q. The concentrations of SMP in the activated sludge were lower than the concentrations of EPS over the entire study, with humic substances being the main components of the two biopolymers. SMP and, more specifically, SMP carbohydrates, were the most influential biopolymers in membrane fouling, while for EPS and their components, no relation was found with fouling. The SRT and temperature were the operational variables that most influenced the SMP and EPS concentration, causing the increase of SRT and temperature a lower concentration in both biopolymers, although the effect was not the same for all the components, particularly for the EPS carbohydrates, which increased with longer SRTs. Both operational variables were also the ones most influential on the concentration of organic matter of the effluent, due to their effect on the SMP. The volatile suspended solid/total suspended solid (VSS/TSS) ratio in the activated sludge can be applied as a good indicator of the risk of membrane fouling by biopolymers in MBR systems.

Tendencias en la modelación matemática de biorreactores con membranas sumergidas para el tratamiento de aguas residuales

“…Recientemente, la influencia de las SPE solubles o PMS ha atraído la atención de los investigadores (Drews et al, 2008;Geng & Hall, 2007;Jeong et al, 2007;Jiang et al, 2010;Kim & Nakhla, 2009;Marín et al, 2017;Paul & Hartung, 2008;Rosenberger et al, 2005;Rosenberger et al, 2006;Wang et al, 2009;Wu et al, 2008;Yao et al, 2011). Geng y Hall (2007) observaron que la distribución de la talla de los flóculos y la cantidad de SPE solubles o PMS en la mezcla de licor fueron los elementos más importantes que influyeron en el proceso de colmatación de la membrana.…”

“…Kim y Nakhla (2009) reportaron que las mayores velocidades de colmatación se favorecieron preferiblemente por los PMS que por las SPE enlazadas. De igual manera, Wang et al (2009) y Marín et al (2017) observaron una correlación mucho más acentuada de los PMS con la colmatación de la membrana que con las SPE enlazadas. La mayoría de las sustancias orgánicas solubles, incluyendo los PMS, pueden entrar en los poros de las membranas de micro y ultrafiltración, las cuales por el tamaño de sus moléculas y sus propiedades adherentes pueden acumularse parcialmente en el interior de los poros de la membrana, ocasionando la obstrucción de estos (Lin et al, 2014).…”