Download poster «Exoenzyme activities, operational parameters, cell viability and EPS in a MBR»
Domestic sewage should be subjected to purification processes before being discharged to streams or reused for other purposes. One of the most innovative biological treatment processes is the membrane biological reactor (MBR).MBR systems are based on the combination of the activated sludge system and membrane technologies to separate the particulate material from water, avoiding the need of a secondary clarifier. One of the main operational problems in MBRs is the membrane fouling or biofouling. Bacteria present in the biomass of an activated sludge system produce sticky compounds denominated extracellular polymeric substances (EPS) which result from active bacterial secretion, shed from the cell surface or cell lysis. Thus, the activated sludge floc components are bound together by means of EPS: polysaccharides, proteins, nucleic acids and lipids, which provide the mechanical stability to the floc, and mediate their adhesion to surfaces. After long time filtration of wastewater, both accumulation of EPS and amount of microbial populations reach to maximum, which also indicate the minimum permeating capacity of a membrane module. There are different factors affecting fouling: membrane, sludge characteristics and operation parameters (sludge retention time, dissolved oxygen, type of wastewater and food/microorganisms ratio), that also affects the EPS properties. In this study, cell viability, extracellular redox activity, EPS (proteins and carbohydrates), exoenzymatic activities (β- glucuronidase and phosphatase) from an urban MBR activated sludge have been analyzed. Canonical correspondence analysis (CCA), a method of direct gradient analysis, revealed the relationships of exoenzymatic activities, cell viability and EPS with the operational parameters and wastewater influent characteristics. Phosphatase was correlated with high levels of hydraulic retention time (HRT), while β-Glucuronidase was related with excess sludge production (ESP). Bioreactor temperature (Tr) correlated negatively to β- gucuronidase and phosphatase in agreement with other works. Results of biplot analysis of influent water showed an inverse relationship between the concentration of total phosphorus (TP) influent and the phosphatase and β-gucuronidase exoenzimatic activities. The influent increase in the availability of C might have contribute negatively to the phosphatase activity.
Amorós, I., Grañana, C., Borrás, E., Zuriaga, E., Zornoza, A., Alonso, J.L. (2012) V International Conference on Environmental, Industrial and Applied Microbiology – BiomicroWorld 2013. Madrid, Spain.