Influence of bacterial extracellular polymers on the membrane separation activated sludge process

Abstract

The objective of this study is to elucidate influence of bacterial extracellular polymers (EPS) on the performance of the submerged membrane separation activated sludge process (SMAS). Hollow fiber membrane modules were submerged in laboratory-scale reactors and the permeate was pulled out from the modules by suction pumps. Acetic acid was used as a carbon source and peptone or ammonium nitrogen was used as a nitrogen source in the substrate. The change of EPS amount both in the mixed liquor and on the membrane was measured and its influence on the permeability of the membrane was studied. EPS was accumulated in the aeration tanks and also on the membrane, which caused an increase of viscosity of the mixed liquor and an increase in the filtration resistance. Specific resistance of EPS was calculated to be of the order of 1016 to 1017 m kg−1. Change of the filtration resistance was explained as a function of viscosity of the mixed liquor, which is caused by rapid attachment of the suspended EPS and rapid detachment of the attached EPS. Detachment rate of the attached EPS was calculated to be nearly constant during the operation.

Sludge filterability and dewaterability in a membrane bioreactor for municipal wastewater treatment

“…This observation apparently differs from analysis reported by [21] where the method of extraction and mode of measurement (as TOC or as Carbohydrates and Proteins) are different. Also [22] commented that high EPS causes high viscosity and accumulation on the membrane surface leading to increase in the filtration resistance. On account of such diversified inferences supported from various methods of analysis and different definitions of EPS fractions, the comparison of outcomes is rather difficult as also stated by [23].…”

“…The MLSS is not well correlated with any of the parameters mentioned in Table 2; a weak positive correlation with DSVI and free EPS (as TOC) can be attributed to extracellular organic materials influencing the settling behaviour at higher MLSS. Few researches [22,26] commented that filtration resistance increases with increase in MLSS; and more recent researches [21,27,28] suggest that MLSS can possibly correlate with fouling/filtration related parameters only at very high concentrations. Visual inspection confirmed the crucial role of sludge conditioning (see Fig.…”

Biotechnology advances

“…Li et al (2007b) investigated aerobic granulation in membrane bioreactor, and measured the total extracellular polymeric substances (EPS) contents on day 5 as 39.6 mg gSS − 1 , and as 749.5 mg gSS − 1 on day 28. Nagaoka et al (1996) had suggested that EPS adsorbed on the surface of aerobic biogranules led to increased water content and loose-structure of biogranules.…”

Investigating the effect of colloids on the performance of a biofilm membrane reactor (BF-MBR) for treatment of municipal wastewater

“…Suspended solids are very often identified as a main foulant (Defrance et al, 2000;Bae et al, 2005) where the significance of the submicron colloidal fraction in the SS has been reported to correlate with membrane fouling rates (Wisniewski et al, 2000;Li et al, 2005;Rosenberger et al, 2006). In MBR processes fouling has also been attributed to extracellular polymeric substances (EPS) and soluble microbial products (SMP) (Nagaoka et al, 1996;Chang et al, 2002;Li et al, 2005;Rosenberger et al, 2006).…”