Filtration Characteristics Of Membranes Research Articles

Effect of UF Membrane Rotation on Filtration Performance Using High Concentration Latex Emulsion Solution.

A high shear rate can be applied to fluid near a membrane surface by rotating the membrane. This shear rate enables higher permeate flux and higher concentration operation when compared with a conventional cross-flow membrane since fouling and/or concentration polarization are reduced. The purpose of this study was to clarify the relationship between the fluid behavior and membrane separation characteristics of a rotating membrane surface when a latex aqueous solution was used. Due to the synergistic effect of particle removal by the centrifugal forces generated by the rotation of the membrane and the reduction in the thickness of the velocity boundary layer, membrane filtration of high-concentration slurry, which is difficult to dewater by the cross-flow method, is possible. The experimental data using an aqueous latex solution with a wide range of slurry concentrations and various membrane diameters are well correlated using a shear rate derived from the boundary layer theory. It is thus confirmed that the shear rate can be used as a design and operating parameter to define the membrane filtration characteristics.

A Study on Membrane Filtration Characteristics of Methanogenic Mixed Liquor in Two Phase Anaerobic Digestion of Food Waste

Objectives:An experimental study was conducted to investigate the membrane filtration characteristics of mixed liquor in methanogenic reactor to extend solid retention time (SRT) in food waste anaerobic digestion system.Methods:On the basis of the particle size distribution (0.5~700 µm) of the methanogenic mixed liquor, three grade membranes (MF, UF, NF) were tested in a stirred cell filtration and a plate type module. Furthermore foulants of membrane, especially UF, was investigated by SEM-EDS, FTIR, SEC.Results and Discussion:As a result UF membrane was selected for stable filtration of the liquor in terms of flux (2.51 L/m<sup>2</sup>･h･bar) and the flux recovery (100%) as well as filtration resistance (Total 7.15.E+13 m<sup>-1</sup>). Average flux was 18 L/m<sup>2</sup>･h･bar for the selected UF membrane in cross flow filtration using a flat plate module. The filtration results showed that membrane fouling was caused by gel and cake layer formed on the membrane surface and 90% of the initial flux could be recovered by physical washing. It was identified that major fouling causing materials were byproducts of carbohydrate and protein decomposition, and small amount of inorganic substance detected on the membrane surface were salt and struvite like materials.Conclusions:Based on the membrane filtration characteristics analyzed from the study, the UF membrane coupled anaerobic digestion is feasible to be applied as a novel food waste treatment system for SRT extension of the methanogenic reactor.

Membrane Bioreactors for Anaerobic Treatment of Wastewaters

Anaerobic biological treatment systems can offer a number of advantages over their aerobic counterparts. The operational costs associated with anaerobic systems are typically lower than with aerobic systems, and anaerobic systems also generate less waste sludge. In addition, the energy associated with the biogas produced during anaerobic biological treatment can potentially be recovered. However, to date, the use of conventional anaerobic biological systems for the treatment of dilute wastewaters has been relatively limited. The present study was designed to address this current knowledge gap. The specific objectives of the present study were (1) to assess and compare the treatment performance of external and a submerged membrane AnMBRs operated at different OLRs when treating a low strength municipal wastewater at a relatively low temperature, (2) to assess and compare the membrane filtration characteristics of mixed liquors generated in external and submerged membrane AnMBRs, (3) to assess and compare the membrane filtration characteristics of a mixed liquor in AnMBRs when filtering through inorganic and organic membranes, and (4) to assess and compare the membrane filtration characteristics of the mixed liquors generated in AnMBRs to the mixed liquor generated in an aerobic MBR operated with the same influent wastewater. This title belongs to WERF Research Report Series ISBN: 9781843397601 (Print) ISBN: 9781780403946 (eBook)

Applicability of dynamic membrane technology in anaerobic membrane bioreactors

This study investigated the applicability of dynamic membrane technology in anaerobic membrane bioreactors for the treatment of high strength wastewaters. A monofilament woven fabric was used as support material for dynamic membrane formation. An anaerobic dynamic membrane bioreactor (AnDMBR) was operated under a variety of operational conditions, including different sludge retention times (SRTs) of 20 and 40 days in order to determine the effect of SRT on both biological performance and dynamic membrane filtration characteristics. High COD removal efficiencies exceeding 99% were achieved during the operation at both SRTs. Higher filtration resistances were measured during the operation at SRT of 40 days in comparison to SRT of 20 days, applying a stable flux of 2.6 L/m2 h. The higher filtration resistances coincided with lower extracellular polymeric substances concentration in the bulk sludge at SRT of 40 days, likely resulting in a decreased particle flocculation. Results showed that dynamic membrane technology achieved a stable and high quality permeate and AnDMBRs can be used as a reliable and satisfactory technology for treatment of high strength wastewaters.

Survey on nitrogen removal and membrane filtration characteristics of Chlorella vulgaris Beij. on treating domestic type wastewaters

The main objective of this study is to evaluate the nitrogen assimilation and filtration characteristics of Chlorella vulgaris Beij. when treating domestic wastewaters. Chlorella could assimilate organic nitrogen, ammonia and nitrate in wastewater, and the mean cell residence time (MCRT) to achieve the maximum biomass content in a bioreactor was different for each individual nitrogen source used. The experimental results showed that using nitrate as the only nitrogen source was the most favorable for biomass growth. With ammonia and nitrate coexisting in the aquatic phase, Chlorella possibly utilized ammonia first, and this was unfavorable to subsequent biomass growth. Nitrifying bacteria in wastewaters significantly affected Chlorella growth as they possibly competed with Chlorella in assimilating ammonia and nitrate in domestic wastewater. In a submerged ultrafiltration (UF) membrane module, with an initial concentration of 850 mg/L of Chlorella, the optimized flux was 0.02 m(3)/(m(2)·h), and the filtration cycle was 30 min. A 'dual membrane bioreactor (MBR)' configuration using UF membranes for Chlorella incubation was proposed. MBR1 provides an environment with long MCRT for efficient nitrification. The converted nitrate is assimilated by Chlorella in MBR2 to sustain its growth. UF permeate from MBR1 is bacteria-free and does not affect the growth of Chlorella in MBR2. MCRT of Chlorella growth is controlled by the UF membrane of MBR2, providing the flexibility to adjust variations of nitrogen composition in the wastewater.

Ultrafiltration of Thin Stillage from Conventional and E-Mill Dry Grind Processes

We used ultrafiltration (UF) to evaluate membrane filtration characteristics of thin stillage and determine solids and nutrient compositions of filtered streams. To obtain thin stillage, corn was fermented using laboratory methods. UF experiments were conducted in batch mode under constant temperature and flow rate conditions. Two regenerated cellulose membranes (10 and 100kDa molecular weight cutoffs) were evaluated with the objective of retaining solids as well as maximizing permeate flux. Optimum pressures for 10 and 100kDa membranes were 207 and 69kPa, respectively. Total solids, ash, and neutral detergent fiber contents of input TS streams of dry grind and E-Mill processes were similar; however, fat and protein contents were different (p < 0.05). Retentate obtained from conventional thin stillage fractionation had higher mean total solids contents (27.6% to 27.8%) compared to E-Mill (22.2% to 23.4%). Total solids in retentate streams were found similar to those from commercial evaporators used in industry (25% to 35% total solids). Fat contents of retentate streams ranged from 16.3% to 17.5% for the conventional process. A 2% increment in fat concentration was observed in the E-Mill retentate stream. Thin stillage ash content was reduced 60% in retentate streams.

Cheese whey treatment performance of an aerobic jet loop membrane bioreactor

The raw chess whey (CW) treatment capacity of a jet loop membrane bioreactor (JLMBR) was evaluated. Raw CW was first characterized for carbonaceous, nitrogenous and phosphorus compounds. The total COD range of the raw CW was between 73 and 86 kg m −3 and 82% of the total COD was found to be soluble. The JLMBR system, of 32 l capacity was operated continuously for 3 months with a sludge age of 1.1–2.8 days and COD loads of 3.5–33.5 kg-COD m −3 per day. A treatment efficiency of 97% was obtained for 1.6 days of sludge age and COD loads of 22.2 kg-COD m −3 per day. The sludge flocks observed in the system were highly motile, dispersed and had poor settling properties. The membrane filtration characteristics of this sludge were investigated and increasing MLSS concentration decreased membrane flux values.

Effect of Coagulation Conditions on Membrane Filtration Characteristics in Coagulation−Microfiltration Process for Water Treatment

In a coagulation−microfiltration (MF) hybrid process, membrane permeability and permeate water quality were investigated in conjunction with coagulation mechanisms under two kinds of dead-end (e.g....

Membrane Filtration Characteristics in Membrane-Coupled Activated Sludge System: The Effect of Floc Structure on Membrane Fouling

The membrane-coupled activated sludge (MCAS) process has many advantages over the conventional activated sludge system, but the inherent membrane fouling problem still remains to be solved. However, it is not yet advanced enough to understand the reliable fouling mechanism. The strength of the MCAS process lies in the almost complete removal of suspended solids from the activated sludge broth. But it has made us overlook the effect of sludge morphology and physiology on membrane flux which is one of the key factors in deciding the economical feasibility of the MCAS system. The aim of this study was to investigate membrane filtration characteristics in the MCAS process, especially to correlate floc structures of the activated sludge with membrane fouling. A series of ultrafiltrations with both hydrophilic and hydrophobic membranes using the stirred batch cell system was performed to assess flux behavior according to the floc structures of the activated sludges (normal, pinpoint, and bulking activated sludge). The order of fouling tendency was found to be normal sludge < pinpoint sludge < bulking sludge. Also, all the membranes behaved in the same way. The cake layer resistance (R c) made up most of the total resistance (R t), but the fouling resistance (R f) was negligible in any floc structure. The key factors controlling the R c were the shape and size of the activated sludge flocs and the porosity of the cake layer accumulated on the membrane surface. The hydrophobic membrane showed a greater fouling tendency than the hydrophilic membrane regardless of the microbial floc structures. The difference in fouling tendency between the two membranes was attributed to the hydrophobic interactions between the membrane and floc surfaces.

Membrane filtration characteristics in membrane-coupled activated sludge system — the effect of physiological states of activated sludge on membrane fouling

The effect of sludge physiology on membrane fouling was investigated in a membrane-coupled activated sludge (MCAS) system. A series of ultrafiltrations were performed to assess the flux behaviors according to foaming potential, solids retention time (SRT), growth phase and nutrient condition of the activated sludge. The foaming sludge showed greater flux decline than the non-foaming sludge. The extraordinary increase, that is, more than 100 times in membrane fouling for the foaming sludge, was attributed to the hydrophobic and waxy nature of the foaming sludge surface, which was confirmed by a comparison with relative hydrophobicity. Membrane fouling tendency was increased as SRT decreased. A greater flux decline was observed at the endogenous phase than at the log growth phase. The activated sludge acclimated to the nitrogen deficient substrates produced less extracellular polymeric substances (EPS) and exhibited higher flux than the control activated sludge. The quantitative measurements of EPS content in order to estimate the extent of membrane fouling in various activated sludges showed that, in any physiological states of activated sludge, the higher the content of EPS the activated sludge had, the greater the membrane fouling proceeded. The EPS content of activated sludge is suggested as a probable index for the membrane fouling in a MCAS system.

A method for chronic membrane plasmapheresis in the rat

Therapeutic apheresis as applied to humans may encompass a single treatment or numerous treatments for disorders ranging from acute poisoning to severe chronic autoimmune disease. However, the mechanisms of beneficial effects of apheresis are not well characterized. Utilizing a miniaturized hollow-fiber membrane system, we have developed a reliable technique for long-term vascular access in the rat that permits repetitive plasmapheresis. We established vascular access in 14 animals, with 8 and 6 rats randomized to 3- and 7-wk experimental periods, respectively. Immunoglobulin levels of blood samples obtained immediately before and after each plasmapheresis were measured to examine membrane filtration characteristics. Overall, 100% of the animals survived and 93% successfully completed their assigned experimental periods. Mean decrease of immunoglobulin G and M levels for 28 plasmapheresis treatments in five rats was 66.9 +/- 8.1 and 61.0 +/- 7.3% (SD), respectively, indicating effective membrane filtration. This model of apheresis can be applied to several disorders in the rat, including, but not limited to, spontaneous insulin-dependent diabetes mellitus and experimental inflammatory bowel disease.

The influence of organic acid concentration in methanogenic waste on membrane filtration characteristics

The influence of organic acid concentration in methanogenic waste on membrane filtration characteristics

Filtration characteristics of membranes for plasma separation and changes in membrane structure after blood contact.

Plasma separation experiments with a hollow fibrous filter were made to clarify the effects of hematocrit, protein concentration and wall shear rate on filtrate flux. The resistance of the polarization layer caused by red blood cells is the dominant factor in filtration and accounts for 50 to 80% of total filtration resistance. Factors governing the filtrate flux in plasma separation are plasma viscosity, hematocrit and wall shear rate. An estimation equation for filtrate flux is proposed. Membrane structural changes after plasma separation were evaluated to clarify fouling characteristics in plasma separation by using radioisotope-labeled solute and scanning electron microscopy. The decrease in pore diameter and surface porosity is attributed to both protein adsorption onto pore walls and plugging by red blood cells.