Modeling of biofouling by extracellular polymers in a membrane separation activated sludge system

Abstract

A Laboratory-scale experiment was conducted to investigate the mechanism of the bio-fouling in the submerged membrane separation activated sludge system. Flat-sheet-type membrane module was used and the change of the pressure and the filtration resistance was measured. Two reactors were operated in parallel to investigate the influence of organic loading rate on the reactor performance. A mathematical model was developed to simulate temporal changes of suction pressure, flux and filtration resistance considering accumulation, detachment and consolidation of EPS on the membrane surface. Parameters in the model were determined so that the calculated results fit to the measured variation curves. The high load reactor (1.5g-TOC L−1 day−1) showed a sudden increase of the pressure and a decrease of flux after 40th days, which could not be recovered even by membrane cleanings, while the low load reactor (0.5g-TOC L−1 day−1) showed little increase of the pressure until 120th days. The measured pattern of the flux, the pressure and the resistance were well explained by the developed model. Using the model, influence of operational parameters, such as organic loading rate, flux and shear stress working on the membrane, on the reactor performance was evaluated. It was concluded that the flux is the most influential parameter and when the flux is more than a critical value, which is as low as 0.1 m day−1, maximum time during which the set flux can be maintained becomes very short.

Effect of hydraulic retention time on membrane fouling and biomass characteristics in submerged membrane bioreactors

“…Nagaoka et al [28] investigated the influence of OLR on membrane fouling in two parallel submerged MBR s, and found that the high OLR (1.5 g-TOC/L/day) showed a sudden increase of the pressure and a decrease of flux after 40th days, which could not be recovered even by membrane cleanings, while the low OLR (0.5 g-TOC/L/ day) showed little increase of the pressure until 120th days. The data obtained from the current investigation, together with previous work in the literature, indicate that HRT or OLR was a very significant operating parameter that affects membrane performance in MBR systems.…”

“…The composition and quantity of the organic fraction of the EPS would correlate to the membrane fouling [41]. Nagaoka reported that the high OLR could lead to much production of EPS and result in severe membrane fouling [28].…”

Characterization of dissolved compounds in submerged anaerobic membrane bioreactors (SAMBRs)

“…Their model assumed that a fraction of SMPs was retained in the reactor due to membrane rejection, since part of the SMP was comprised of macromolecules. A model to predict membrane fouling taking into account the accumulation of ECP in a submerged membrane activated sludge process was also proposed by Nagaoka et al 18 According to these authors the measured pattern of changes in flux, pressure and resistance was explained well by the model, which assumed that ECP accumulates on the membrane by advection, while it is detached from the biomass by shear stress.…”

Treatment of wastewater from biodiesel plants using microbiological reactor technology

“…However, a significant increase in MLSS concentration was observed while decreasing the HRT from 15 h to 12, 9 and 6 h because shorter HRT provides more nutrients to the biomass and leads to a higher biological growth and so a higher MLSS (Dufresne et al 1998). According to Nagaoka et al (1998), MLSS is also directly influenced by organic loading rate (OLR); therefore, when OLR was varied from 1 to 2 and 3 g/L day on each HRT, an increase in MLSS concentration was also reported, as shown in Fig. 2.…”