Browsing by Author "Katayama, H."

Now showing 1 - 5 of 5

Combined effects of EPS and HRT enhanced biofouling on a submerged and hybrid PAC-MF membrane bioreactor
(2013-02) Khan, Mohiuddin M. T.; Takizawa, S.; Lewandowski, Zbigniew; Rahman, M. Habibur; Komatsu, K.; Nelson, Sara E.; Kurisu, F.; Camper, Anne K.; Katayama, H.; Ohgaki, S.
The goal of this study was to quantify and demonstrate the dynamic effects of hydraulic retention time (HRT), organic carbon and various components of extracellular polymeric substances (EPS) produced by microorganisms on the performance of submersed hollowfiber microfiltration (MF) membrane in a hybrid powdered activated carbon (PAC)-MF membrane bioreactor (MBR). The reactors were operated continuously for 45 days to treat surface (river) water before and after pretreatment using a biofiltration unit. The real-time levels of organic carbon and the major components of EPS including five different carbohydrates (D(Ã¾) glucose and D(Ã¾) mannose, D(Ã¾) galactose, N-acetyl-D-galactosamine and Dgalactose, oligosaccharides and L( ) fucose), proteins, and polysaccharides were quantified in the influent water, foulants, and in the bulk phases of different reactors. The presence of PAC extended the filtration cycle and enhanced the organic carbon adsorption and removal more than two fold. Biological filtration improved the filtrate quality and decreased membrane fouling. However, HRT influenced the length of the filtration cycle and had less effect on organic carbon and EPS component removal and/or biodegradation. The abundance of carbohydrates in the foulants on MF surfaces was more than 40 times higher than in the bulk phase, which demonstrates that the accumulation of carbohydrates on membrane surfaces contributed to the increase in transmembrane pressure significantly and PAC was not a potential adsorbent of carbohydrates. The abundance of N-acetyl-Dgalactosamine and D-galactose was the highest in the foulants on membranes receiving biofilter-treated river water. Most of the biological fouling compounds were producedinside the reactors due to biodegradation. PAC inside the reactor enhanced the biodegradation of polysaccharides up to 97% and that of proteins by more than 95%. This real-time extensive and novel study demonstrates that the PAC-MF hybrid MBR is a sustainable technology for treating river water.
Continuous and efficient removal of THMs from river water using MF membrane combined with high dose of PAC
(2009-12) Khan, Mohiuddin M. T.; Lewandowski, Zbigniew; Takizawa, S.; Yanade, Kyosuke; Katayama, H.; Ohgaki, S.
A combination of microfiltration (MF) membrane with a high concentration (40 g/L of the reactor) of powdered activated carbon (PAC) efficiently and continuously removed trihalomethanes (THMs) and total organic carbon (TOC) from river water for a period of two months. Without PAC, the membrane reactor was able to remove less than 18% of THMs and less than 5% of TOC; with PAC, 65 to 95% of THMs and TOC were removed. Even though the THMs concentration in the influent was steadily increasing (reaching 50 Î¼g/L), THMs concentration in the effluents from the reactors with PAC were consistently below 15 Î¼g/L. While the MF membranes alone could not remove organics, PAC and microbial activity in the biofilm deposited on the PAC particles assured long term and continuous removal of THMs. No additional PAC was added into or removed from the reactors during the filtration period. Operational parameters such as the backwashing of the membrane, interval of the filtration cycle and biological pretreatment of the river water had a small effect on the extent of THMs removal, but they increased the filtration time prior to membrane cleaning and improved the overall performance of the reactors.
Membrane fouling due to dynamic particle size changes in the aerated hybrid PAC–MF system
(2011-04) Khan, Mohiuddin M. T.; Takizawa, S.; Lewandowski, Zbigniew; Jones, Warren L.; Camper, Anne K.; Katayama, H.; Ohgaki, S.
To quantify the effect of dynamic particle size changes and degradation and accumulation of suspended solids (SS) in influents to reactors on membrane fouling frequency in hybrid powder-activated carbon (PAC)–microfiltration (MF) reactors, we operated a PAC–MF system (hollow-fiber module) for more than five months to purify river water before and after pretreatment by a biofilter. The transmembrane pressure, backwashing pressure, resistance to filtration, and SS accumulation and degradation during these dynamic changes were evaluated. The initial dose of PAC was 40 g/L of the reactor and no additional PAC was added during this continuous operational period. The presence of PAC reduced the membrane resistance to filtration even at the end of filtration period when the number of particles in the smallest range (>1.0–3.6 μm) was the highest measured by the flow cytometer and microscopy image analysis. This resistance was reduced further when the river water was biofiltered prior to membrane filtration. This real-time study demonstrates that over time PAC and other particles coming into the reactors through the influents degrade and/or become smaller because of the turbulence caused by continuous aeration below the MF membrane fibers. The number of particles in the reactors with diameters less than 10 μm increased with time, increasing the fouling frequency; however, the presence of PAC further reduced the particle enhanced fouling. The presence of PAC also increased SS degradation by up to 10%. The increased number of bacteria inside the PAC–MF systems did not contribute to the number of membrane fouling. Even though the particle sizes inside the reactors became smaller with time, the gradual increase in net accumulation of SS was also an important factor controlling the performance of the PAC–MF system.
Powdered activated carbon and biofiltration improve MF performance: Part I
(2007-05) Khan, Mohiuddin M. T.; Jones, Warren L.; Camper, Anne K.; Takizawa, S.; Katayama, H.; Kurisu, F.; Ohgaki, S.
This article shows how the use of high-dose powdered activated carbon and biofiltration are able to improve the performance of membrane-based microfiltration systems. The first part, which appears here, provides an overview of the study, materials and methods, and experimental design and operational conditions of the reactors.
Powdered activated carbon and biofiltration improve MF performance: Part II
(2007-06) Mohiuddin, Khan T.; Takizawa, S.; Katayama, H.; Kurisu, F.; Camper, Anne K.; Ohgaki, S.
This article shows how the use of high-dose powdered activated carbon and biofiltration are able to improve the performance of membrane-based microfiltration systems. The first part of this feature, which was published in the May 2007 issue of Membrane Technology, provides an overview of the study, materials and methods, and experimental design and operational conditions of the reactors. The second installment, which appears here, discusses the results of this study.