Development of hybrid membrane bioreactor for tannery effluent treatment
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Keywords:
Electrocoagulation
Membrane bioreactor
Membrane Fouling
Abstract BACKGROUND Membrane bioreactor (MBR) is commonly considered a promising technology for wastewater treatment due to its outstanding effluent quality, low sludge production, and smaller environmental footprint. However, membrane biofouling is regarded as the bottleneck of MBR processes preventing their universal application. Optimizing operating conditions and improving the antifouling properties of membranes have a substantial impact on the rate and characteristics of membrane fouling in MBR systems. RESULTS In this study, a two‐step process was performed to mitigate membrane fouling by optimizing sludge retention time (SRT) and organic loading rate (OLR) and improving membrane characteristics in an MBR system developed for the treatment of pharmaceutical wastewater. At first, pure membrane fouling and sludge characteristics were examined in three identical MBRs at different OLRs (40, 100, and 160 mg chemical oxygen demand(COD)/L.d) under various SRTs (7.5, 22.5, and 37.5 days). The investigation indicated that high protein concentration in loosely bound extracellular polymeric substances (LB‐EPS) caused more irreversible fouling at the OLR and SRT of 40 mgCOD/L.d and 7.5 days, respectively. In the second stage, a modified anti‐biofouling membrane was installed into the optimized submerged MBR at OLR = 100 mgCOD/L.d and SRT of 22.5 days for further mitigation of membrane fouling. Membrane fouling significantly reduced as the protein and gram negative bacteria on the surface of the modified membrane decreased. CONCLUSION The results showed that the reversible and irreversible membrane fouling were controlled successfully through the proposed optimization of operational conditions and by improving the membrane characteristics in MBR. Finally, the protein of LB‐EPS is a vitally important factor affecting the irreversible membrane fouling. © 2020 Society of Chemical Industry (SCI)
Membrane bioreactor
Membrane Fouling
Extracellular polymeric substance
Biofouling
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A long-term operation was conducted to investigate the alleviation of membrane fouling by sludge/water pre-separation membrane bioreactor (S/W-MBR). The variation of trans-membrane pressure (TMP), concentration of sludge and extracellular polymeric substances (EPS) on S/W-MBR and submerged membrane bioreactor (SMBR) was also studied. The results showed that the sludge concentration in S/W-MBR was basically identical with that of SMBR's biotic area, while the sludge concentration was significantly decreased in S/W-MBR's membrane area than that of SMBR's. The concentration of EPS was increased with operation time in both two MBRs' biotic area, but it was lower and basically maintained at the level of 15 mg/g in S/W-MBR's membrane area. The S/W-MBR was more capable of alleviating membrane fouling, and it had been cleaned only 2 times while the SMBR who had been cleaned 5 times during the period of about 90 days laboratory performance.
Membrane bioreactor
Membrane Fouling
Extracellular polymeric substance
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The coagulation-microfiltration(MF) combination process of treating micro-polluted water was studied.The effect of coagulation parameters such as dosage,pH and time were discussed and the results demonstrated that dosage and pH were the critical parameters,while time was not.The coagulation-microfiltration combination process could mitigate membrane fouling.Comparing two filtration methods,it was observed that filtration of coagulation floc suspention was better than filtration of supernatant.The effect of different coagulants on the removal of organics and mitigation membrane fouling in coagulation-microfiltration combination process were also studied.Ferric chloride and polyaluminium chloride(PAC) were used as coagulants.The results suggested that ferric chloride was slightly superior for micro-polluted water on the basis of CODMn and UV254 removal,while PAC was slightly superior on mitigating membrane fouling.By evaluating the recovery effect of the membrane permeability,characteristics of membrane fouling and its cleaning in a coagulation-microfiltration combination process were studied.The results showed that the membrane fouling caused by cake layer,microorganism and organic pollutants and inorganic pollutants accounted for 70%-80%,20%-25%,5%-8%,respectively.The coagulation-microfiltration combination process of micro-polluted water with tap water flushing could restore the membrane permeability effectively.
Membrane Fouling
Filtration (mathematics)
Membrane permeability
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Membrane fouling is the main bottleneck of the membrane bioreactor(MBR) and its widespread application. In this paper, a lab-scale submerged MBR treating synthesis wastewater was operated to examine the affecting mechanisms and correlation of soluble microbial products(SMP) with membrane fouling. A single-fiber microfiltration set-up was fabricated and applied to evaluate the importance of sludge properties of different sludges, including MLSS, EPS, SMP and their organic components, to the fouling evolution rate. It was revealed that MLSS, EPS and SMP all show positive correlation with the fouling rate(ΔTMP/Δm). However, the importance of SMP separated from MBR activated sludge(AS) to fouling rate(rp = 0.126) is rather lower than that of SMP in MBR cake sludge(CS)(rp =0.871). The protein and polysaccharide in CS-SMP, other than humic-like substances, were proved to be the major substances affecting fouling layer formation. Both the examination by fluorescence excitation emission matrix(EEM) and the observation under confocal laser scanning microscopy(CLSM) display that the SMP have to transform in the term of surface properties and size distribution with the development of membrane filtration. The AS-SMP has obvious protein-peak compared with MBR effluent, which implies that the protein is preferentially intercepted by membrane compared with other organic components. Whilst, after the membrane interception, the SMP in CS has a size as large as 100 μm, which would facilitate the cake layer formation and hence is determinative for the fouling evolution. A comprehensive observation of fouled membrane surface with CLSM also demonstrates that there are two types of fouling layer on the membrane surface, i.e. cake-dominant and gel-dominant fouling layer, both of which are highly depend on the content of AS-SMP in SMBR. It was noted that the SMP in SMBR and cake sludge is the major foulant. The present work is valuable for understanding of the membrane fouling mechanisms and also for proposing the strategies for membrane fouling control in SMBR.
Membrane bioreactor
Membrane Fouling
Extracellular polymeric substance
Filtration (mathematics)
Segmented filamentous bacteria
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Membrane Fouling
Filtration (mathematics)
Colloidal Silica
Membrane Technology
Cross-flow filtration
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This study investigated the effect of microbubble floatation on the fouling of microfiltration membranes. Synthetic feed solutions containing either kaolin or alginic acid were used for the membrane filtration tests. A dissolve air flotation system using a pump-type microbubble generator was adopted as a pretreatment for microfiltration system. A multi-array submerged membrane filtration system was used to monitor the changes in transmembrane pressure with time under various operating conditions. Turbidity removal efficiency, particle counts, and fouling rate for the microfiltration membrane were measured after the microfiltration floatation. The effect of coagulant dose on the treated water quality and membrane performance was also investigated. Results showed that microbubble floatation without coagulant was effective to reduce membrane fouling by kaolin but it was not very effective to control fouling by alginate. With the aid of coagulant, microbubble flotation could control fouling by alginate. This is attributed to the removal mechanisms of foulants by microbubble floatation: suspended particles can be separated by the microbubbles without coagulant but dissolved organics can be only removed by the combined effect of coagulation and floatation.
Membrane Fouling
Filtration (mathematics)
Turbidity
Ultrafiltration (renal)
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Membrane bioreactor(MBR) is a high-efficiency technology for wastewater treatment and reuse.Membrane fouling is the main problem of MBR,which has limited its widespread application.The factors that influencing the membrane fouling of MBR were systematically discussed from the aspects of membrane characteristics,operation condition,and characteristics of activated sludge mixed liquor;and then,the measures for membrane fouling controlling were summarized according to the mentioned factors.It was pointed out that,through the effective and reasonable controlling measures,membrane fouling could be mitigated significantly,which created the condition for the wilder application of MBR in the field of wastewater treatment and reuse.
Membrane Fouling
Membrane bioreactor
Wastewater Reuse
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MBR is popular in the research of waste water disposal at present.The key to limit MBR's wide application is membrane pollution.Membrane fouling in membrane bioreactors is discussed in this paper,involving the type of membrane fouling,membrane fouling models,membrane washing,design and operations considering antifouling in the integrated MBR etc.
Membrane bioreactor
Membrane Fouling
Biofouling
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Bacteriophage MS2
Membrane Fouling
Filtration (mathematics)
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In order to prevent membrane fouling and improve the elimination effect of phosphorus,polymeric aluminum and fly-ash were fed to membrane bioreactor to change the property of wastewater treatment;meanwhile active sludge was analyzed with X-ray diffraction and infrared spectrum methods,and hollow membrane was probed with SEM to investigate the mechanism of membrane fouling.The results show that the property of active sludge and bio-membrane structure were changed by adding polymeric aluminum,especially the removal rate of phosphorous could reach 85% and the membrane fouling was reduced effectively.Moreover no effect was observed when ash-fly was fed into the membrane bioreactor.
Membrane bioreactor
Membrane Fouling
Membrane structure
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