MBR Process Research Articles

침지형 MBR공정에서 파울링 특성과 파울링 완화제의 적용성에 관한 연구

Though MBR process has many advantages, the greatest risk factors in operating MBR process are occurrence of membrane fouling and decrease of flux. It is very difficult to find exact mechanism due to complex influence by many effects, although there have been recently many studies of membrane fouling. The purposes of this study are firstly evaluating bioreactor of lab-scale and micro-filtration hollow fiber membrane, secondly investigating correlation between foulants affecting membrane performance and membrane fouling, and lastly evaluating various parameters affecting fouling and applicability of membrane fouling reducer. This study found that TMP was increasing rapidly and showed 0.32 bar and the average of flux was 88 LMH. EPS concentration tends not to change much above MLSS concentration (6,000 mg/L). However, EPS concentration variation is wide below MLSS concentration (6,000 mg/L). Also, from results of membrane surface condition and element analysis using SEM/EDX, carbon and fluorine were founded to be the highest percentage in membrane because of characteristics of membrane material. In operating continuously, inorganic fouling was generated by increase of these inorganic substances such as and . Lastly, the best filtration performance was obtained for 0.03 mg MFR/mg MLSS by results of particle size, zeta potential, , EPS and MLSS concentration.

Comparison between MBR and A/O processes treating saline wastewater

Membrane bioreactor MBR and A/O processes are employed to treat saline wastewater. The mixed liquid suspended solids in the MBR and A/O were 7,000 and 3,500 mg/L, respectively. With the same influents, MBR process was more suitable for the treatment of high-salinity wastewater. The chemical oxygen demand and ammonia removal efficiencies were 75 and 82%, respectively, with the salinity of 24.5 g/L. Both were higher than that through the A/O process. Autotrophic nitrifying bacteria could be enriched and had sufficient time to accommodate to the saline environment. Both sludge volume index (SVI) decreased with salinity increment. However, the SVI of MBR dropped more than that of A/O, which indicated a better sludge-settling property in the MBR process. Filamentous bacteria existed in the A/O reactor and made the sludge-settling property worse than that in the MBR process. Membrane fouling occurred inevitably during the MBR process. Microbes and organics could be removed by combined physical and chemical cleaning.

Wastewater treatment using membrane bioreactor and reverse osmosis process

The objective of this study was to investigate the effect of hydraulic retention time (HRT) on removal efficiencies of organic matter, nitrogen, and phosphorus in membrane bioreactors-reverse osmosis (MBR-RO) process for treating synthetic sewage. In MBR process, turbidity was less than average 2 NTU and average removal efficiency showed more than 99% during the operational period (MBR 105 day). As a result of HRT variation, average removal efficiencies of CODCr on HRT 6, 12, 18, and 24 h were about 72.4, 84, 88.6, and 92.5%, respectively. The NH4+–N removal efficiency was about 60.2, 85.5, 91.3, and 92.2%, respectively. TN and TP removal efficiencies increased from 53.7 and 56.8 to 82.5 and 86.4%, respectively, as the HRT increased from 6 to 24 h. In RO process, average removal efficiencies of color and CODCr in RO permeated water were about 99.9 and 96.8%, respectively. Also, removal efficiencies of TN, NH4+–N, NH4+–N, and TP were all above average 90%.

Submerged Membrane Bioreactor (SMBR) for Treatment of Textile Dye Wastewatertowards Developing Novel MBR Process

This paper deals with the application of a submerged membrane bioreactor (SMBR) with commercial membrane module and novel MBR modulefor the treatment of model textile dye wastewater (MTDW). For this work, MTDW was developed based on different publications and a pilot-scale automated SMBR unit was applied to carry out the tests with this model wastewater. The system is on the way to be upgraded to attain novel MBR module replacing the applied commercial membrane by novel membrane materials which have been developed by the European Commission funded project “BioNexGen” [1]. The hydraulic volume of the employed SMBR reactor was 57 L. One flat sheet commercial MBR module was submerged in the reactor. The module consisted of 3 sheets, with 25cm×25cm dimensions of each sheet covering total active membrane area of 0.33 m2. To reach the target, different MBR process parameters like COD, BOD, TOC, pH, conductivity, flux, TMP, MLSS, colour contents, air supply, O2 consumption, HRT, SRT, drying residue, nutrients etc. have been investigated. It is reported that under the operating conditions of permeate flux of 4 L/m2h, around 50 mbar of TMP, 12g/L of MLSS, 40-80h of HRT, 1.0 m3/h of air supply to MBR reactor, pH of 8.2±0.2- 10.5±0.2 and temperature of 18±2°C, the COD removal efficiency was around 90% for 2450mg/L inlet COD fed to the membrane bioreactor and Red and Blue colour removal efficiencies were 25-70% and 20-50% respectively. In order to develop novel MBR process, a novel MBR module has already been applied replacing the commercial one and the preliminary results are reported.

Biotoxicity evaluation of coking wastewater treated with different technologies using Japanese medaka (Oryzias latipes)

The potential biotoxicity to the environment should be addressed during wastewater treatment. In this study, biotoxicity of coking wastewater effluent from MBR, Fenton, electro-Fenton and coagulation treatment processes was evaluated using embryos and larvae of Japanese medaka (Oryzias latipes). The acute toxicity based on 96-h larval mortality as well as the chronic toxicity based on embryo hatching, larvae swim-up failure, growth, and sexual ratio were determined. The results showed that different treatment processes have various biotoxicity levels. The acute toxicity of Fenton and electro-Fenton effluents was much higher than that of MBR and coagulation. For the chronic toxicity, the effluent of the Fenton/electro-Fenton process displayed lower embryo hatching, larvae survival and growth in comparison with the effluents of MBR and coagulation. No endocrine disruption was detected in MBR, Fenton and electro-Fenton effluents, but was contained in the coagulation effluent. The biotoxicity test indicated that the effluent of MBR was very safe for the environment. The toxicological indices were necessary for ecological safety maintenance in the industrial wastewater treatment.

Economic evaluation of a combined photo-Fenton/MBR process using pesticides as model pollutant. Factors affecting costs

The aim of this paper is to carry out an economic assessment on a solar photo-Fenton/MBR combined process to treat industrial ecotoxic wastewater. This study focuses on the impact of the contamination present in wastewater, the photochemical oxidation, the use of an MBR as biological process and the plant size on operating and amortization costs. As example of ecotoxic pollutant, a mixture of five commercial pesticides commonly used in the Mediterranean area has been used, ranging from 500mg/L to 50mg/L, expressed as dissolved organic carbon concentration. The economic evaluation shows that (i) the increase in pollution load does not always involve an increase in photo-Fenton costs because they also depend on organic matter mineralization; (ii) the use of an MBR process permits lower photochemical oxidation requirements than other biological treatments, resulting in approximately 20% photo-Fenton cost reduction for highly polluted wastewater; (iii) when pollution load decreases, the contribution of reactant consumption to the photo-Fenton process costs increase with regard to amortization costs; (iv) 30% total cost reduction can be gained treating higher daily volumes, obtaining competitive costs that vary from 1.1–1.9€/m3, depending on the pollution load.

Fouling characteristics in pure oxygen MBR process according to MLSS concentrations and COD loadings

A submerged MBR with a pure oxygen system was operated at high COD loading conditions to find out how high a level of COD loading can be treated consistently in an aerobic condition. Pure oxygen was supplied with circulated MLSS to the aerobic tank by a two-phase nozzle to increase oxygen transfer efficiency. Tested COD loadings ranged from 2 to 10kgCOD/m3 day. And the effect of MLSS concentration on the membrane fouling was investigated from 5000 to 25,000mg/L. The membrane fouling rates and filtration resistance were tested to evaluate the effect of COD loadings and MLSS concentrations. Over the range of COD loading tested (2.0–10kgCOD/m3 day), the effluent qualities ranged from 35 to 69mg/L and the COD removals ranged from 99.1 to 99.7 for synthetic wastewater. The membrane fouling rates increased seven-fold over a five-fold increase in COD loadings. And the fouling rates increased almost nine-fold over a three-fold increase in MLSS concentration. The membrane fouling in high COD loading conditions was more sensitive to MLSS concentration than COD loading. The specific EPS productions in this test ranged from 6.9 to 10.9mgEPS/gVSS, and the specific polysaccharide and protein productions were 9.2mgPolysaccharide/gVSS and 1.8mgProtein/gVSS, respectively.

Effect of dissolved oxygen on the performance of a step-feed hybrid MBR process treating synthetic domestic wastewater

An innovative step-feed Anaerobic-(Oxic/Anoxic)n-Membrane Bioreactor [An-(O/A)n-MBR] process was developed to treat synthetic domestic wastewater. Performance of the lab-scale system was investigated at different dissolved oxygen (DO) concentration (0.4–2.4 mg/L) in the aerobic tank of the multiple A/O zone. The results showed that, under the conditions imposed, the DO level has little influence on chemical oxygen demand removal and the removal efficiency was more than 94% throughout the operation. However, DO levels have great influence on nitrogen and phosphorus removal. Better nitrification efficiency could be obtained when DO was in the range of 0.8–2.4 mg/L; the ammonia removal efficiency was more than 99%. High total nitrogen (TN) and total phosphorus (TP) removal performance can be obtained when DO was in the range of 0.8–1.2 mg/L; the average removal efficiency was 74.8 and 71.4%, respectively. In this condition, DO can meet the demand of nitrification and phosphorus uptake simultaneously, and the simultaneous nitrification and denitrification occurred in the aerobic tanks under lower DO concentration. Meanwhile, since the DO circulated from the aerobic tank to the anoxic tank decreased, denitrification was enhanced and the nitrate quantities in the sludge recycle system decreased, resulting in the decrease of carbon substrate competition between denitrification and phosphorus release in the anaerobic zone. Ultimately, the performance of TN and TP removal was enhanced.

Integration of aerobic granular sludge and mesh filter membrane bioreactor for cost-effective wastewater treatment

Conventional MBR has been mostly based on floc sludge and the use of costly microfiltration membranes. Here, a novel aerobic granule (AG)-mesh filter MBR (MMBR) process was developed for cost-effective wastewater treatment. During 32-day continuous operation, a predominance of granules was maintained in the system, and good filtration performance was achieved at a low trans-membrane pressure (TMP) of below 0.025m. The granules showed a lower fouling propensity than sludge flocs, attributed to the formation of more porous biocake layer at mesh surface. A low-flux and low-TMP filtration favored a stable system operation. In addition, the reactor had high pollutant removal efficiencies, with a 91.4% chemical oxygen demand removal, 95.7% NH4+ removal, and a low effluent turbidity of 4.1NTU at the stable stage. This AG-MMBR process offers a promising technology for low-cost and efficient treatment of wastewaters.

Hollow fiber membrane life in membrane bioreactors (MBR)

The MBR technology has evolved rapidly over the past two decades with significant gains in performance and reliability, and reductions of costs. While the MBR process is recognized for providing superior effluent quality in a small footprint, it carries additional operating costs associated with the membrane system, including the periodic replacement of the membranes which have a life shorter than the civil components of the plant. The methodology used to determine membrane life was to analyze the entire data set of ZeeWeed MBR membranes shipped to North American sites over the period of 15years since their commercial introduction. This analysis shows that membrane life for the current generation product should be greater than 10years. The analysis also considered the various mechanisms of aging and end-of-life triggers. It was determined that a slow increase in operating pressure and the need for more frequent chemical cleaning should be the dominant end-of-life trigger with the current product. The most effective method for membrane replacement is a planned campaign where a fixed portion of the plant, typically dictated by the membrane train configuration, is replaced on an annual basis in the period of time around the anticipated life of the membranes.

Comparison of A<sup>2</sup>/O and Membrane Bioreactor Processes for Municipal Wastewater Treatment: Nutrient Removal Performance and Sludge Characteristics

The performance of nitrogen and phosphorus removal was investigated in pilot-scale A2/O, A2/O-MBR and mA2/O-MBR processes for treating municipal wastewater. The results show that these processes had a similar COD and ammonia removal efficiency, but A2/O process had better denitrification efficiency than MBR processes. In order to explain the difference of nitrogen and phosphorus removal performance in the investigated processes, specific oxygen uptake rate (SOUR), specific denitrification rate (SDNR), anaerobic release rate and anoxic and aerobic uptake rate of the activated sludge taken from A2/O and mA2/O-MBR processes were compared. The results show that the activated sludge of mA2/O-MBR process had a higher nitrifying activity in aerobic tank than A2/O process, the denitrifying activity in anoxic tanks were roughly equal and A2/O process had a higher denitrifying phosphorus removal activity in anoxic tank than mA2/O-MBR process.

Study on Activated Sludge Properties of A/A/O Combined Membrane Bioreactor during Startup Period

To improve treatment performance and alleviate membrane fouling, the physical and biological properties of sludge in combined MBR which divided into anoxic, anaerobic and aerobic zone were studied. During initial startup period, the sludge in A/A/O combined MBR was suspended growth, after textile carrier package, the sludge was suspended and fixed growth. The biomass analysis showed that with the increase of operation time, MLVSS/MLSS decreased from 0.93 to 0.72 which certified that high MLSS concentration caused biomass growth slow gradually, while packing textile carrier could supply attached biomass which maximum value was 0.18g/cm(3777.8mg/L). Meanwhile, high MLSS concentration also resluted in high sludge viscosity which could reach to 35.42mPa•s and decreased sludge activity. Particle size anaylisis showed that shear stress of aeration made the sludge flocs smaller than conventional activated sludge process. All the sludge properties which had been analysis in this study showed A/A/O combined MBR had great difference from conventional MBR process, and some parameters could be used for membrane fouling control in A/A/O combined MBR for wastewater treatment project.

Removal of micropollutants by membrane bioreactor under temperature variation

The effects of controlled temperature variation in the range of 10–45 °C were assessed in a lab-scale MBR that treated synthetic municipal wastewater spiked with selected micropollutants. The effects were evaluated with respect to total organic carbon (TOC) and total nitrogen (TN) removal, micropollutant removal, sludge growth, level of soluble microbial products (SMPs) in the mixed liquor and membrane fouling. Overall, the temperature shifts caused high variation in the TOC and TN levels in the reactor supernatant, however that in membrane-permeate was relatively more stable, substantiating the robustness of the MBR process. Results regarding the removal of micropollutants at ambient temperature (20 °C) demonstrate an apparent correlation between hydrophobicity, chemical structures and the removal of micropollutants. Temperature variation below and above 20 °C, especially the operation under 45 °C appeared to significantly influence the removal of certain less hydrophobic (log D < 3.2) micropollutants possessing strong electron withdrawing functional groups. The removal of most hydrophobic compounds (log D > 3.2) was stable under the temperature range of 10–35 °C, however, deteriorated at 45 °C. The temperature shifts were also associated with higher levels of SMP in the mixed liquor which appeared to trigger membrane fouling as evidenced by a rapid increase in transmembrane pressure.

Physico-chemical characterisation versus in situ micro-structural characterisation of membrane fouling in membrane bioreactors

Fouling characteristics of aerobic submerged membrane bioreactors were analysed under two different membrane materials. Polyethersulfone (PES) membranes were found to foul faster at sub-critical flux than polyolefin (PO) membranes. Physico-chemical characterisation, by means of comparison of extracellular polymeric substances (EPS) and soluble microbial products (SMP) concentrations, as well as the mixed liquor suspended solids (MLSS) concentration were unable to explain the differences in membrane fouling of the contrasting membrane materials. The use of confocal laser scanning microscopy (CLSM) to image organic foulants directly on the membrane surface, coupled with image analyses showed that membrane fouling mechanism shifted from a biofilm initiated process on PO membranes to a bio-organic dominated process on PES membranes under sub-critical flux conditions. These results show that physico-chemical characterisation of an MBR process may not effectively distinguish the effectiveness of different membrane materials, so long as operating conditions are identical, and that characterisation of foulants on the membrane surfaces was necessary to elucidate the differences in membrane fouling.

Exploration of dual optimal conditions for COD and nitrogen removal in an MBR

AbstractMembrane bioreactors (MBRs) have been increasingly used for wastewater treatment in last decade. MBR process has several characteristics such as high sludge retention time, high mixed liquor concentration and accumulation of soluble microbial products. Although activated sludge models (ASMs) have been developed for conventional activated sludge process, applying the ASM model to MBR process seems to be proper. In this study, a model‐based systematic approach that can find optimal operational conditions for chemical oxygen demand (COD) and nitrogen removal was explored to a MBR process. To enhance the modeling performance of the ASM, the precise influent characterization for MBR process was performed by using a respirometry. The optimization results in MBR plant showed that the removal efficiencies of COD and nitrogen in the plant were greatly improved to 88.10 and 62.67%, respectively. Copyright © 2011 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

An independent water system with maximized wastewater reuse for non-potable purposes - Model case for future urban development

A study was conducted to formulate an optimized plan for upgrading an independent water system in a college campus where the available water source is from 5 groundwater wells with a maximum water supply capacity of 3000 m3/d but the water demand is much beyond this value for both potable and non-potable consumption. By water balance analysis, it was estimated that with the available fresh water consumed only for potable and related miscellaneous uses for 30000 people, the quantity of the reclaimed water could be enough to cover all the non-potable consumption. By material balance analysis, the pollutant loadings of organics, nitrogen and phosphorus were calculated and the requirements for pollutant removal corresponding with reuse purposes were evaluated. Considering the quality criteria of water reuse for lake landscaping, toilet flushing and gardening, and the demand for each water usage in the campus, a dual-quality reclaimed water supply scheme was proposed as (1) supply of lower quality reclaimed water for gardening and road sprinkling by upgrading the existing wastewater treatment facility of 1500 m3/d using conventional process, and (2) supply of higher quality reclaimed water for lake water replenishment and toilet flushing by implementing a new wastewater treatment facility of 2500 m3/d using MBR process. The independent water system thus optimized could sustain a total water consumption of more than 6000 m3/d using the 3000 m3/d source water. This provided a model case for future urban development in the water deficient region.

Pilot-Scale MBR and RO Process for COD, Nitrogen and Phosphorus Removals of Mixed Domestic – Industrial Wastewater at 30°C in Singapore

Pilot-Scale MBR and RO Process for COD, Nitrogen and Phosphorus Removals of Mixed Domestic – Industrial Wastewater at 30°C in Singapore

Characterization of Long-Term Foulants Deposited on Full-Scale Membrane Modules in Submerged MBR Processes

Characterization of Long-Term Foulants Deposited on Full-Scale Membrane Modules in Submerged MBR Processes

Modeling of Membrane Fouling Based on Extracellular Polymers in Submerged MBR

To offer an overall conceptual understanding and extend the knowledge of combined submerged MBR process, a modified membrane fouling model was developed. The model was constructed based on Extracellular Polymers (EPS) which increased with biomass growth in submerged MBR system. Due to density of EPS accumulated on the membrane surface caused trans-membrane pressure increase which finally results in flux decrease, the membrane fouling model adopted EPS concentration in mixed liquor and EPS density on membrane surface as main influence factors for trans-membrane pressure variation. Simulation results show that the fouling model could well predict membrane fouling in submerged MBR which three zones as anoxic, aerobic and anaerobic, it could offer operational and design parameters decision and optimal operational conditions.

Optimizing aeration rates for minimizing membrane fouling and its effect on sludge characteristics in a moving bed membrane bioreactor

In MBR processes, sufficient aeration is necessary to maintain sustainable flux and to retard membrane fouling. Membrane permeability, sludge characteristics, nutrient removal and biomass growth at various air flow rates in the membrane and moving bed biofilm reactor (MBBR) compartments were studied in a pilot plant. The highest nitrogen and phosphorous removal rates were found at MBBR aeration rates of 151 and 85Lh−1 and a specific aeration demand per membrane area (SADm) of 1.2 and 0.4 mair3 m−2 h−1, respectively. A linear correlation was found between the amount of attached biofilm and the nutrient removal rate. The aeration rate in the MBBR compartment and SADm significantly influenced the sludge characteristics and membrane permeability. The optimum combination of the aeration rate in the MBBR compartment and SADm were 151Lh−1 and 0.8–1.2 mair3 mmembrane−2 h−1, respectively.