Membrane Bioreactor Technology Research Papers (original) (raw)

Rheology Sludge Viscosity a b s t r a c t Rheological characterization is of crucial importance in sludge management both in terms of biomass dewatering and stabilization properties and in terms of design parameters for sludge handling operations. The sludge retention time (SRT) has a significant influence on biomass properties in biological wastewater treatment systems and in particular in membrane bioreactors (MBRs). The aim of this work is to compare the rheological behaviour of the biomass in a MBR operated under different SRTs. A bench-scale MBR was operated for 4 years under the same conditions except for the SRT, which ranged from 20 days to complete sludge retention. The rheological properties were measured over time and the apparent viscosity was correlated with the concentration of solid material when equilibrium conditions were reached and maintained. The three models most commonly adopted for rheological simulations were evaluated and compared in terms of their parameters. Then, steady-state average values of these parameters were related to the equilibrium biomass concentration (MLSS). The models were tested to select the one better fitting the experimental data in terms of mean root square error (MRSE). The relationship

- by and +1
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- Water, Statistical Analysis, Rheology, Multidisciplinary

Membrane bioreactors (MBRs) for wastewater treatment offer the advantage of a complete removal of solids from the effluent. The secondary clarifier is replaced by a membrane filtration and therefore high biomass concentrations (MLSS) in the reactor are possible. The design of the aeration system is vital for an energy efficient operation of any wastewater treatment plant. Hence the exact measurement of oxygen transfer rates (OTR) and α-values is important. For MBRs these values reported in literature differ considerably. The OTR can be measured using non-steady state methods or using the off-gas method. The non-steady state methods additionally require the determination of the respiration rate (oxygen uptake rate ≡ OUR), which usually is measured in lab scale units. As there are differences of OUR between lab scale and full scale measurements, off-gas tests (which do not require an additional respiration test) were performed in order to compare both methods at high MLSS concentrations. Both methods result in the same average value of OTR. Due to variations in loading and wastewater composition variations of OTR in time can be pointed out using the off-gas method. For the first time a comparison of different oxygen transfer tests in full scale membrane bioreactors is presented.

This study focused on the characterization of fouling cake layer during operation of a membrane bioreactor system employed for the treatment of synthetic hypersaline oily wastewater. Also the effects of ultrasound and addition of four types of flocculants (aluminium sulfate, Chitosan, ferric chloride, polyaluminium chloride) on mitigation of membrane fouling were studied. The components of the foulants were examined by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray (EDX) analysis, inductively coupled plasma (ICP) and particle size analyzer (PSA). The FTIR demonstrated that membrane fouling layer is governed by the deposition of organic and inorganic substances composed of extracellular polymeric substances (EPS) (proteins, polysaccharides, etc.), hydrocarbon components and inorganic matters. The AFM images of the fouled membrane confirmed the idea of surface coverage as a fouling mechanism. The SEM analysis showed that rod-shape bacterial clusters were one of the contributors to membrane cake layer. The EDX and ICP results showed that Mg, Al, Ca, Na, K and Fe were the major metal elements in the fouling cake. The PSA results indicate that membrane foulants had a much smaller size than mixed liquor suspensions in the MSBR. Fouling mitigation experiments showed that the effect of organic flocculant was more than inorganic chemicals but the overall effects were not significant. Ultrasound could effectively remove the fouling cake from the membrane surface and thus recovered the membrane permeation flux for a long time.

- by Maria Serralheiro
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- Chemistry, Water, Biotechnology, Peptide Synthesis

This paper is designed to provide an overview of the main membrane-assisted processes that can be used for the removal of toxic inorganic anions from drinking water supplies. The emphasis has been placed on integrated process solutions, including the emerging issue of membrane bioreactors. An attempt is made to compare critically recently reported results, reveal the best existing membrane technologies and identify the most promising integrated membrane bio/processes currently being under investigation. Selected examples are discussed in each case with respect to their advantages and limitations compared to conventional methods for removal of anionic pollutants. The use of membranes is particularly attractive for separating ions between two liquid phases (purified and concentrated water streams) because many of the difficulties associated with precipitation, coagulation or adsorption and phase separation can be avoided. Therefore, membrane technologies are already successfully used on large-scale for removal of inorganic anions such as nitrate, fluoride, arsenic species, etc. The concentrated brine discharge and/or treatment, however, can be problematic in many cases. Membrane bioreactors allow for complete depollution but water quality, insufficiently stable process operation, and economical reasons still limit their wider application in drinking water treatment. The development of more efficient membranes, the design of cost-effective operating conditions, especially long-term operations without or with minimal membrane inorganic and/or biological fouling, and reduction of the specific energy consumption requirements are the major challenges.

- by Joao Crespo
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- Chemistry, Water quality, Arsenic, Multidisciplinary

Özet: Tekstil endüstrisindeki gelişmelere paralel olarak ticari olarak 100.000'den fazla boya çeşidi (ağırlıkça %70 civarı azo boyalarıdır) bulunmakta ve her yıl %50'si tekstil boyası olmak üzere 1 milyon tondan fazla boyar madde üretilmektedir. Üretim aşamasında 1 kg pamuğun reaktif boyalar ile birlikte 70 ile 150 L arasında değişen miktarda suya, 0.6 ile 0.8 kg NaCI'ya, ve 30 ile 6 g arasında boyar maddeye ihtiyacı vardır. Üretilen atıksuda da buna bağlı olarak AKM, boyar maddeler, tuzlar ve organik-inorganik kirliliğe sebep olan diğer yardımcı kimyasallar bulunmaktadır. Bu atıksuyun arıtımı için, karakteristiğindeki çeşitlilik nedeniyle tek bir arıtma ünitesinden çok daha fazlasına ihtiyaç duyulmaktadır. Bu amaçla yapılan çalışmada 6 farklı tipte nanofiltrasyon (NF90, NF270, NFTS40, NFXN45, NFDK ve NFDL) ve 3 farklı tipte ters osmos membranları (ROX201, ROBW30FR ve ROACM5) ile bir tekstil endüstri bölgesinden gelen evsel ve endüstriyel atıksular dead-end filtrasyon deneyleri yapılarak çeşitli basınçlar altında akı ve filtrasyon performansları izlenmiştir. Ayrıca, atıksu çeşitli pH değerlerinde (pH 3,7 ve 10) değerler yazılırsa iyi olur) NF270, NF90 ve NFTS40 membranları ile filtrelenerek membran ile boya molekülleri arasındaki elektrostatik ilişkinin membran tıkanıklığı üzerine etkisi incelenmiştir. Çalışmada en yüksek geçirgenlik NF270 membranı ile elde edilmiş olup bu değer 5.95 L/(m 2 .h.bar)'tır. NF270 membranı ile diğer nanofiltrasyon membranlarına nazaran en yüksek geçirgenlik değerine ulaşılmasına rağmen, akıda birim zamanda en yüksek azalma da bu membranda olmuştur. 15 bar basınç altında başlangıç geçirgenlik değeri olan 12 L/(m 2 .h.bar) 1 saatlik test süresi sonunda, 4 L/ (m 2 .h.bar)'a düşmüştür. Ters osmoz membranlarında ise en yüksek geçirgenlik değeri ROX201 membranı ile 2.96 L/(m 2 .h.bar) olarak tespit edilmiş ve en yüksek akı düşüşü de ROACN5 membranında gözlemlenmiştir (. Nanofiltrasyon membranları arasında en yüksek renk (>99%), iletkenlik (>94%) ve KOİ (>97%) giderimi NF90 membranı ile elde edilmiştir. Daha yüksek iletkenlik giderimi istendiğinde ise ters osmoz membranlarının kullanılması gerekmektedir. Test edilen ters osmoz membranları için iletkenlik giderim yüzdeleri RO BW30FR, RO X201 ve RO ACM5 için >96%, >95% ve >97%'dir. pH'da yapılan değişiklik akı değerlerini etkilemiştir. NF270 membranı için pH'nın 10'a yükseltilmesi, nötral ya da asidik koşullara göre daha yüksek akı/geçirgenlik elde edilmesini sağlamıştır. Ters osmoz

The EU project SAFIR aimed to help farmers solve problems related to the use of low quality water for irrigation in a context of increasing scarcity of conventional freshwater resources. New decentralised water treatment devices (prototypes) were developed to allow a safe direct or indirect reuse of wastewater produced by small communities/industries or the use of polluted surface water. Water treatment technologies were coupled with irrigation strategies and technologies to obtain a flexible, easy to use, integrated management of the system. The challenge is to apply new strategies and technologies which allow using the lowest irrigation water quality without harming food safety or yield and fruit or derivatives quality. This study presents the results of prototype testing of a small-scale compact pressurized membrane bioreactor and of a modular field treatment system including commercial gravel filters and heavy-metal specific adsorption materials. Decentralised compact pressurised membrane biobooster (MBR), was able to remove up to 99.99% of the inlet Escherichia coli and 98.52% of total coliforms. E. coli was completely removed from irrigation water in 53% of the samples by the last MBR prototype version. In 2008, 100% of samples fulfilled WHO standards (1989) and Global Gap requirement for faecal contamination. MBR removed from inlet flow in the average 82% of arsenic, 82% of cadmium, 97% of chromium, 93% of copper and 99% of lead. Boron and manganese were not removed from permeate. The field treatment system (FTS) proved to be effective against faecal contamination when applied with its complete set up including UV treatment. The sole gravel filter and heavy metal removal device (HMR) cannot provide sufficient and steadily treatment for microbial contamination. Nevertheless, gravel filter can remove up to 60% of E. coli but the removal process was not stable nor predictable. FTS removed 76% of arsenic, 80% of cadmium and copper, 88% of chromium and lead, and up to 97% of zinc. Like the MBR, boron and manganese were not removed from the irrigation water. Gravel filter directly fed with secondary treated wastewater was found able to remove 41% of arsenic, 36% of cadmium and lead, 48% of chromium and 46% of copper. The residual heavy metals concentration after the gravel filter was further reduced by the HMR: 35% for arsenic, 22% for cadmium, 25% for chromium, 33% for copper and 53% for lead.

- by Sushil Gola
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- Civil Engineering, Food Safety, Arsenic, Water Treatment

The concept of membrane bioreactor systems consists of – “Utilizing a bioreactor and microfiltration or ultra-filtration as one unit process for waste water treatment thereby replacing, and in some cases supplementing, the solids separation function of secondary clarification and effluent filtration.” Early MBRs were based on pressurized modules in recirculation loops, but the current state of the art involves immersing the membranes in the activated sludge and drawing the treated water by suction. The idea of coupling activated sludge with membrane separation was conceived in the mid-1960s at Dorr-Oliver (Stanford, Connecticut), but the technology was not commercialized in North America. Thetford Systems (Ann Arbor, Michigan), which later became part of ZENON, accomplished this in the early 1970s. The company developed a membrane bioreactor system for on-site treatment and recycling of wastewater. The system, called Cycle Let was based on an aerobic – anoxic activated sludge process with tubular ultra-filtration (UF) in a two-pump feed and bleed loop. Permeate from the UF membranes was disinfected in a UV unit, and reused for toilet flushing.

The effects of fluidized media characteristics on membrane fouling and energy consumption in the anaerobic fluidized membrane bioreactor (AFMBR) were evaluated. Both adsorbing granular activated carbon (GAC) and non-adsorbing silica and polyethylene terephthalate (PET) beads were evaluated. For fresh GAC, the energy requirement for fluidization increased with size, but smaller sizes led to greater reduction in membrane fouling. But when the GAC adsorption capacity was first exhausted, the reverse was noted, the larger particles reduced membrane fouling best. Non-adsorbing silica particles and PET beads demonstrated similar results to pre-adsorbed GAC, lower fouling was accomplished by the larger media that had a higher energy requirement for fluidization. The media packing ratio was also of importance, the higher the packing ratio up to 50%, the greater the reduction in fouling. Fouling reduction was also somewhat better at a given energy expenditure with lower specific gravity PET beads than with denser and smaller pre-adsorbed GAC particles.

- by Muhammad Aslam
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- Membrane Science, Membranes, Membrane Technology, Membrane Separation Technology

A membrane bioreactor was developed to perjorm an extractive bioconversion aimed at the production of isovaleraldehyde by isoamyl alcohol oxidation with whole cells of Gluconobacter oxydans. A liquid/liquid extractive system using isooctane as extractant and assisted by a hollow-fiber hydrophobic membrane was chosen to recover the product. The aqueous bioconversion phase and the organic phase were maintained apart with the aid of the membrane. The extraction of alcohol and aldehyde was evaluated by performing equilibrium and mass transfer kinetic studies. The bioprocess was then pe$ormed in a continuous mode with addition of the substrate to the aqueous phase. Fresh solvent was added to the organic phase and exhausted solvent was removed at the same flow rate. The extractive system enabled a fast and selective in situ removal of the aldehyde from the water to the organic phase. High conversions (72-90%) and overall productivity (2.0-3.0 g I-' hh') were obtained in continuous experiments performed with different rates of alcohol addition (1.5-3.5 g 1-t h-'). Cell deactivation was observed after I@12 h of operation.

There is a need for a low cost, sensitive, on-line sensor to assess the integrity of membrane modules used in the water industry for water treatment, membrane bioreactors and for pre-treatment prior to using nanofiltration or reverse osmosis. A sensor addressing this need is described whose operating principle is based on measuring the differential pressure across a membrane that intercepts a portion of the permeate from the pre-treatment module(s) relative to the differential pressure across a valve. The latter can be adjusted to maximize the sensitivity of the instrument. A dimensionless metric based on the differential pressures is defined and corroborated with the Silt Density Index. The sensitivity of this Integrity Sensor is demonstrated by its response to cutting one fiber in a UF pre-treatment module that contains 1500 hollow fibers.

- by Royer Krantz
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- Engineering, Water Treatment, Membrane Bioreactor Technology, Desalination

With membrane bioreactors, the production of surplus sludge is lower than with conventional activated sludge systems, a fact that has been confirmed in a large number of analyses. There is, however, no consensus about the dimension of the reactions and their respective causes. In order to examine these, at the University of Hanover a pilot plant with a capacity of 220 l was run for one year without any extraction of surplus sludge. The plant was started with 2 g MLSS/l; after one year, this value had risen to approximately 18 g MLSS/l. In order to be able to set the plant for different sludge loads (0.04 to 0.2 kg COD/(kg MLSS · d)), the wastewater was artificially stocked up. The emerging result was that in contrast to conventional systems the sludge growth was lower, but still continuously existing. Then, comparisons with theoretical approaches were run – among others with the ASM1-Model – which confirmed the findings. One possible reason could be the different biocoenoses, which ...

Eight pharmaceuticals, two polycyclic musk fragrances and nine endocrine disrupting chemicals were analysed in several waste water treatment plants (WWTPs). A membrane bioreactor in pilot scale was operated at different solid retention times (SRTs) and the results obtained are compared to conventional activated sludge plants (CASP) operated at different SRTs. The SRT is an important design parameter and its impact on achievable treatment efficiencies was evaluated. Different behaviours were observed for the different investigated compounds. Some compounds as the antiepileptic drug carbamazepine were not removed in any of the sampled treatment facilities and effluent concentrations in the range of influent concentrations were measured. Other compounds as bisphenol-A, the analgesic ibuprofen or the lipid regulator bezafibrate were nearly completely removed (removal rates 490%). The operation of WWTPs with SRTs suitable for nitrogen removal (SRT410 days at 10 1C) also increases the removal potential regarding selected micropollutants. No differences in treatment efficiencies were detected between the two treatment techniques. As in conventional WWTP also the removal potential of MBRs depends on the SRT. Ultrafiltration membranes do not allow any additional detention of the investigated substances due to size exclusion. However, MBRs achieve a high SRT within a compact reactor. Nonylphenolpolyehtoxylates were removed in higher extend in very lowloaded conventional WWTPs, due to variations of redox conditions, necessary for the degradation of those compounds.

- by Helmut Kroiss
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- Perfume, Activated Sludge, Multidisciplinary, Membrane Bioreactor Technology

This paper presents biological and physical performance data from a pilot-scale membrane bioreactor system fed with synthetic wastewater containing high molecular weight compounds. At steady state, high effluent quality was obtained and maintained for about 350days. The membrane was effective in retaining heterotrophic microorganisms and MS-2 viruses, eliminating the need for effluent disinfection. The flux through the membrane decreased rapidly

- by Nazim Cicek
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- Water, Multidisciplinary, Membrane Bioreactor Technology, Oxygen Uptake

The impact of removable and irremovable fouling on the retention of viral and bacterial indicators by the submerged microfiltration membrane in an MBR pilot plant was evaluated. Escherichia coli, sulphitereducing Clostridium spores, somatic coliphages and F-specific RNA bacteriophages were used as indicators. The membrane demonstrated almost complete removal of E. coli and sulphite-reducing Clostridium spores. However, there was no correlation with membrane fouling. The phage removal varied in accordance with the irremovable fouling, rising from 2.6 to 5.6 log 10 units as the irremovable fouling increased (measured by the change in the transmembrane pressure). In contrast, removable fouling did not have any effect on the retention of viruses by the membrane. These results indicate that irremovable membrane fouling may affect the removal efficiency of MBRs and, therefore, their capacity to ensure the required microbiological standards for the permeate achieved.

- by Ignasi Rodriguez-roda and +2
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- Wastewater Treatment, Multidisciplinary, Membrane Bioreactor Technology, Bioreactor

The development and application of a membrane bioreactor (MBR) for full-scale Municipal wastewater treatment is the most important recent technological advance in terms of biological wastewater treatment. The MBR is a suspended growth-activated sludge system which combines the use of biological processes and membrane technology to treat wastewater and provide organic and suspended solids removal instead of secondary clarifiers. Use of MBR offers the possibility to overcome a lot of problems in activated sludge processes which are mostly due to tertiary treatment. It represents a decisive step forward concerning effluent quality by delivering a hygienically pure effluent and by exhibiting a very high operational reliability. Advanced MBR wastewater treatment technology is being successfully applied at an ever-increasing number of locations around the world. This review article has covered several aspects of MBR. The membrane separation of microorganisms from the treated wastewater is discussed in detail. Problems of membrane fouling and membrane washing and regeneration, linked to activated sludge characteristics, are examined. Finally, advantages and disadvantages of MBR over conventional activated sludge are concerned.

- by Aditi Pandey and +1
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- Water and wastewater treatment, Membrane Bioreactor Technology, Environmental Biotechnology

Membrane bioreactor biofouling is usually described as an extracellular matrix in which biopolymers, inorganic salts and active microbes co-exist. For that reason, biomineralization (BM) models can be useful to describe the spatial organization and environmental constraints within the referred scenario. BM arguments were utilized as background in order to (1) evaluate CaCO 3 influence on flux decline; pore blocking and cake layer properties (resistance, permeability and compressibility) in a wide range of Chitosan/ Bovine serum albumin (BSA) mixtures during step-pressure runs and, (2) perform membrane autopsies in order to explore the genesis of mineralized extracellular building blocks (MEBB) during cake layer build up. Using low molecular weight chitosan (LC) and BSA, 2 L of 5 LC/BSA mixtures (0.25-1.85 ratio) were pumped to an external ultra filtration (UF) membrane (23.5 cm 2 , hydrophobic, piezoelectric, 100 kDa as molecular weight cut-off). Eight different pressure steps (40 ± 7 to 540 ± 21 kPa) were applied. Each pressure step was held for 900 s. CaCO 3 was added to LC/BSA mixtures at 0.5, 1.5 and 3 mM in order to create MEBB during the filtration tests. Membrane autopsies were performed after the filtration tests using thermo gravimetric, scanning microscopy and specific membrane mass (mg cm À2 ) analyses. Biopolymer-CaCO 3 step-pressure filtration created compressible cake layers (with inner voids). The formation of an internal skeleton of MEBB may contribute to irreversible fouling consolidation. A hypothesis for MEBB genesis and development was set forth.

- by Adalberto Noyola
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- Chitosan, Filtration, Multidisciplinary, Extracellular Matrix

Treatment technology for water recycling encompasses a vast number of options. Membrane processes are regarded as key elements of advanced wastewater reclamation and reuse schemes and are included in a number of prominent schemes world-wide, e.g. for artificial groundwater recharge, indirect potable reuse as well as for industrial process water production. Membrane bioreactors (MBRs) are a promising process combination of activated sludge treatment and membrane filtration for biomass retention. This paper will provide an overview of the status of membrane bioreactor applications in municipal wastewater reclamation and reuse in Europe and will depict their potential role in promoting more sustainable water use patterns. Particular attention will be paid to the impact of MBR technology on emerging pollutants. A case study will be presented on a full-scale MBR plant for municipal wastewater which is operated by Aquafin in Belgium.

- by Bruce Jefferson and +1
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- Membrane Bioreactor Technology

Recycled water is becoming increasingly valuable as a water source for urban water supplies in Australia. However, an ongoing area of confusion is the requirements for validation of recycled water schemes. There are currently no common guidelines in Australia that provide guidance on this specific component of recycled water quality management. Thus, to date the requirements for validation of various components of recycled water schemes has seemingly been decided on a case-by-case basis. The Membrane Bioreactors (MBRs) is a reasonably new technology for the purpose of water recycling, and consequently there is not yet a standardised approach to demonstrate consistent and continuous process control to regulatory authorities and obtain approval to supply. This paper describes two examples and discusses the importance of the selection of suitable online monitoring instruments; the influence of bioreactor characteristics on membrane operation; the limitation of membrane types; and the advantages and disadvantages of each validation methodology.

The removal of seven pharmaceuticals and two fragrances in the biological units of various full-scale municipal wastewater treatment plants was studied. The observed removal of pharmaceuticals was mainly due to biological transformation and varied from insignificant (<10%, carbamazepine) to>90% (ibuprofen). However, no quantitative relationship between structure and activity can be set up for the biological transformation. Overall, it can be concluded that for compounds showing a sorption coefficient (K(d)) of below 300 L kg(-1), sorption onto secondary sludge is not relevant and their transformation can consequently be assessed simply by comparing influent and effluent concentrations. The two fragrances (HHCB, AHTN) studied were mainly removed by sorption onto sludge. For the compounds studied, comparable transformation and sorption was seen for different reactor types (conventional activated sludge, membrane bioreactor and fixed bed reactor) as well as for sludge ages betwee...

- by Alfredo Alder
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- Water, Perfume, Activated Sludge, Multidisciplinary

Membrane bioreactors (MBRs) are widely used for wastewater treatment and reuse applications. Selection of a membrane configuration is a crucial step in the design process and has a high impact on further plant operations. Despite increasing experience with full-scale applications, practical knowledge concerning the impact of different membrane configurations on process performance and operational costs is still lacking. This paper provides full scale MBR performance data comparing the use of flat sheet and hollow fibre membranes and analyses the consequences on operation, performance and treatment efficiency. Hollow fibre configurations, comparing to the flat sheet, are designed for higher fluxes, operated at lower concentrations, cleaned more often and protected by stricter pre-treatment. Filterability of activated sludge from municipal MBRs is better than from industrial MBRs and does not depend on membrane configuration. The energy consumption depends more on the influent type than on the membrane configuration.

- by J. Van Der Graaf and +1
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- Engineering, Wastewater Treatment, Activated Sludge, Water Reuse

In 1994, Madoni created the Sludge Biotic Index (SBI) based on the presence and abundance of certain key protozoan groups. The use of this index has become increasingly common in wastewater treatment plant control and its applicability has been demonstrated. In this study, we applied the SBI index to a pilot-scale membrane bioreactor equipped with polyvinylidenefluoride hollow fibre membranes (0.04 m pore size). Two different sludge retention times (SRT) -25 and 35 days -were assayed, with a constant hydraulic retention time of 30 h. Operational conditions for MBR cause the fragmentation of flocs which are broken down into small dissipated elements with abundant dispersed bacteria. This process determines protozoan composition and colonization of the activated sludge. Results of the experiment showed a constant predominance of small flagellates, carnivorous ciliated protozoa and rotifers, above all in assays with 35-day SRT, independently of effluent quality. However, continuous changes in microbiota were observed, with a clear tendency for the SBI to increase over time as the sludge became more stable. Therefore, although it was not possible to establish an association between SBI and effluent quality for MBR activated sludge, the stabilisation of the process may be related to SBI.

The main objective of this work was to investigate the filterability of MBR sludge and its mixture with conventional activated sludge (CAS). In addition, the impacts of type and dose of various polyelectrolytes, filter type and sludge properties on the filterability of both MBR and Mixed sludges were determined. Specific cake resistance (SCR) measured by the Buchner funnel filtration test apparatus and the solids content of the resulting sludge cake were used to assess the dewaterability of tested sludges. The type of filter paper used in Buchner tests affected the results of filterability for MBR, CAS and Mixed sludges. SCR values and optimum polyelectrolyte doses increased with increasing MLSS concentrations in the MBR, which suggested that increase in MLSS concentrations accompanied by increases in EPS and SMP concentrations and a shift toward smaller particles caused poorer dewaterability of the MBR sludge. The significant differences observed among the filterability of CAS and MBR sludges suggested that MLSS alone is not a good predictor of sludge dewaterability. Combining CAS and MBR sludges at different proportions generally improved their dewaterability. Combining MBR sludges having typically high MLSS and EPS concentrations with CAS having much lower MLSS concentrations may be an option for full-scale treatment plants experiencing sludge dewaterability problems. Better filterability and higher cake dry solids were achieved with cationic polyelectrolytes compared to anionic and non-ionic ones for all sludge types tested.

- by Mehmet Kitis
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- Water, Kinetics, Water Purification, Filtration

This paper describes a facile approach for the surface modification of polypropylene non-woven fabric (NWF) by PVA (polyvinyl alcohol) to determine its filterability. The NWF surface modification involved the physical adsorption of PVA to immobilize PVA on the NWF surface. Chemical structures and morphological changes of the PVA-modified NWF sample surfaces were characterized in details by attenuated total reflectance Fourier transform infrared (FTIR/ATR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron micrograph (SEM), and water contact angle measurements. Results reveal that PVA concentration has significant effects on the immobilization degree of PVA, and pure water contact angle on the NWF surface decreases with the increase in PVA concentration indicating an enhanced hydrophilicity for the modified NWF. Coomassie brilliant blue G250 method was utilized to quantify the static bovine serum albumin solution adsorption on the NWF surface. This adsorption was used to indicate the protein fouling property of the modified NWF with PVA. The results showed that after PVA modification, the polar groups such as C-O, C-O-C were introduced to the NWF surface, hydrophilicity was improved, and water static contact angles were decreased from 86 ± 1 • to 43 ± 3 • , the amount of bovine serum albumin (BSA) static adsorption on modified NWF was decreased by 83.4%. Membrane bioreactor was used for the treatment of a pharmaceutical wastewater to determine the filterability of modified NWF. The results revealed that flux declination of modified NWF was only 12%, in comparison of the original NWF of 40%. The anti-fouling property for the modified NWF was enhanced greatly.

Foaming in Membrane BioReactor (MBR) is a frequently discussed topic. Some authors reported that the phenomenon is due to filamentous organisms, like at Conventional Activated Sludge (CAS) plants. However, in recent years, other authors reported that the Extra-cellular Polymer Substances (EPSs) concentration is an important factor for controlling foam as well. Nevertheless, even if a number of MBR plants are affected by foaming, presently there are no suitable methods to evaluate the phenomenon. To facilitate the study of this controversial phenomenon in an MBR system, certain foam tests proposed in the past for CASPs were investigated. The results of the tests were able to adequately measure quantity, stability and quality of the foam. In particular, the Scum Index increased proportionally with the EPS concentration and mixed liquor viscosity; Foam Power was mainly correlated with the protein concentration of in the EPS; Foam Rating was also correlated with the EPS concentration.

By means of a database including information from 117 international scientific papers, we present quantitative conclusions on the concentrations, frequencies of detection and removals of pharmaceutical products in wastewater treatment... more

Membrane bioreactor (MBR) is a reliable and promising technology for wastewater treatment and reclamation applications. In spite of more than a decade of significant advances in developing fouling mitigation methods, different physical and cleaning protocols are still necessary to be developed to limit the membrane fouling. The use of scouring agents in MBR applications has been paid attention as a new approach as an energy-efficient way to control membrane fouling. Recently, mechanical cleaning by scouring agents is becoming as intense research area considering high efficiency of fouling reduction while requiring low energy consumption. In this review, fundamental and comprehensive assessments of the mechanical cleaning concepts and their applications with porous and nonporous scouring agents for MBR system are critically reviewed. The existing challenges and future research prospects on the mechanical cleaning technology associated with scouring agents for the MBR applications are also discussed.

- by Muhammad Aslam
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- Hydrodynamics (Physics), Water, Membrane Science, Membranes

The availability of potable water has become severely limited in the past decade and the quality of current water supplies is deteriorating rapidly . Water contamination by disposal of untreated sewage into water bodies ,water scarcity ,salinity intrusion are common problems faced by many cities in India. Recycling and reuse of wastewater by commercial complexes,residential colonies,industries is the need of the hour.It would eliminate the need for large centralised treatment plants, reduce demand on local supplies and pollution of water bodies.Membrane bioreactors is an ideal solution for the water problems in urban areas. MBR processes produce effluent of high quality enough to be discharged to coastal, surface waterbodies used for irrigation,flushing and other purposes depending upon the quality of treatment . Membrane bioreactors combine conventional biological treatment processes with membrane filteration to provide an advanced level of organic and suspended solids removal. Membrane bioreactor technology has been gaining popularity over past few years all over the world.. Many countries like Singapore are using membrane treatment successfully for supplementing water supplies. MBR technology is yet to gain popularity in India as preferred treatment method over conventional treatment methods for industrial and domestic wastewater treatment. This paper focuses on performance of membrane bioreactors in wastewater treatment in a MBR plant in a hotel in Delhi and the suitability of treated water for reuse and recycling..Samples of raw sewage water and treated water were taken from the plant and tested in laboratory to analyse the efficiency of wastewater treatment by MBR technology. Composite samples were taken for 5 days in the month of October. The changes in wastewater composition were evaluated by measuring changes the total amount of organic matter in terms of BOD, COD, suspended solids (SS,phosphates,nitrogen content of raw water and treated water samples.

Anaerobic ammonium oxidation (anammox) is an energy saving biological nitrogen removal process which was limited to slow growth rate of anammox bacteria during start-up period. This study investigated the start-up of anammox process by a laboratory sequential batch reactor (SBR) for 218 days and subsequently modified the reactor as a membrane bioreactor (MBR) for 178 days. Modification of a SBR as MBR with installation of an external membrane module resulted in acceleration of specific anammox activity by 19 times. The acceleration of specific anammox activity with MBR was further confirmed by starting-up another MBR for a 242 day period. Molecular microbial analyses showed that Candidatus ''Brocadia anammoxidans'' and Candidatus ''Kuenenia stuttgartiensis'' were the dominant species in the inocula and biomass developed in the reactor. The start-up with MBR appeared to be more effective than SBR for the enrichment of anammox bacteria due to high sludge retention property of MBR configuration.

- by Yu Tao and +1
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- Membrane Bioreactor Technology, Bioreactors, WATER TREATMENT ANAMMOX, Nitrogen Removal

Membrane bioreactor (MBR) technology is an efficient technology for municipal and industrial wastewater treatment. It is a novel technology due to its divergent advantages over conventional bioreactors. With significant removal rates of contaminants, MBR has been considered as a simple, reliable and cost-effective process for wastewater treatment. However, the major drawback hindering wider application of MBRs is membrane fouling, which significantly reduces membrane performance and lifespan, resulting in a significant increase in maintenance and operating costs. This paper provides an overview of membrane fouling and mitigating strategies for fouling control in the MBR processes. Recent research tries on fouling control including quorum quenching, addition of coagulants and adsorbents, combination of aerobic granulation with MBRs, and granular materials with air scouring in the MBR tank are presented. Quorum quenching offers higher efficiency, lower toxicity and more sustainability. The addition of coagulants and adsorbents shows a serious membrane fouling reduction but optimum dosages of the various coagulants/adsorbents is needed to be established. Also, the addition of aerobic granulation with MBRs, which targets organic foulants and biofoulants shows outstanding filtration performance and a substantial reduction in fouling rate, as well as excellent nutrients removal. However, further research is needed on the improvement of long-term granule integrity.

- by Jose Gil
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- Environmental Engineering, Chemical Engineering, Civil Engineering, Wastewater Treatment

With the current need for more efficient and reliable processes for municipal and industrial wastewaters treatment, membrane bioreactor (MBR) technology has received considerable attention. After just a couple of decades of existence, MBR can now be considered as an established wastewater treatment system, competing directly with conventional processes like activated sludge treatment plant. However, MBR processes still suffer from major drawbacks, including high operational costs due to the use of anti-fouling strategies applied to the system to maintain sustainable filtration conditions. Moreover, this specific use of membranes has not reached full maturity yet, as MBR suppliers and users still lack experience regarding the long-term performances of the system. Still, major improvements of the MBR design and operation have been witnessed over the recent years, making MBR an option of choice for wastewater treatment and reuse. This minireview reports recent developments and current research trends in the field.

- by Pierre Le-clech
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- Membranes, Recycling, Water Purification, Wastewater Treatment

The membrane bioreactor (MBR) can no longer be considered as a novel process. This reliable and efficient technology has become a legitimate alternative to conventional activated sludge processes and an option of choice for many domestic and industrial applications. However, membrane fouling and its consequences in terms of plant maintenance and operating costs limit the widespread application of MBRs. To provide a better understanding of the complex fouling mechanisms and propensities occurring in MBR processes, this review compiles and analyses more than 300 publications. This paper also proposes updated definitions of key parameters such as critical and sustainable flux, along with standard methods to determine and measure the different fractions of the biomass. Although there is no clear consensus on the exact phenomena occurring on the membrane interface during activated sludge filtration, many publications indicate that the extracellular polymeric substances (EPS) play a major role during fouling formation. More precisely, the carbohydrate fraction from the soluble microbial product (also called soluble EPS or biomass supernatant) has been often cited as the main factor affecting MBR fouling, although the role of the protein compounds in the fouling formation is still to be clarified. Strategies to limit fouling include manipulating bioreactor conditions, adjusting hydrodynamics and flux and optimizing module design.

Diesel engines are preferred over spark ignition counterparts for heavy-duty applications and power generation plants because of their higher efficiency, durability, and productivity. Currently, the research interests have been propelled towards renewable and sustainable diesel fuels such as biodiesel in order to address the environmental and energy security challenges associated with these energy systems. However, the most challenging issue concerning large-scale production of biodiesel is its relatively high cost over fossil-based diesel owing to high feedstock and manufacturing costs. Therefore, cost-effective and eco-friendly biodiesel production technologies should be necessarily developed and continuously improved in order to make this biofuel more competitive vs. its petroleum counterpart. Accordingly, this paper comprehensively reviews biodiesel manufacturing techniques from natural oils and fats using conventional and advanced technologies with an in-depth state-of-the-art focus on the utmost important unit, i.e., transesterification reactor. The effects of the main influential parameters on the transesterification process are first discussed in detail in order to better understand the mechanisms behind each reactor technology. Different transesterification reactors; e.g., tubular/plug-flow reactors, rotating reactors, simultaneous reaction-separation reactors, cavitational reactors, and microwave reactors are then scrutinized from the scientific and practical viewpoints. Merits and limitations of each reactor technology for biodiesel production are highlighted to guide future R&D on this topic. At the end of the paper, the sustainability aspects of biodiesel production are comprehensively discussed by emphasizing on the biorefinery concept utilizing waste-oriented oils.

- by Hamed Kazemi Shariat Panahi and +1
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- Economics, Climate Change, Policy Analysis and Decision Making, Renewable Energy

Heterogeneous photocatalysis is a promising technology especially for environmental remediation. Despite more than a decade of worldwide research in developing photocatalytic efficiency improving techniques, many questions regarding the large scale application of photocatalytic reactors still remain unanswered. Recently, improving the photocatalytic efficiency has gained scientific attention because it might lead to more economical and robust photocatalytic operation for environmental remediation. In this review, fundamental and comprehensive assessments of the photocatalytic concepts and their applications for environmental remediation are reviewed. The existing challenges and strategies to improve the photocatalytic efficiency are discussed. Further, recent developments and future research prospects on photocatalytic systems for environmental applications are also addressed.

To meet the worldwide rapid growth of industrialization
and population, the demand for the production
of bioethanol as an alternative green biofuel is gaining significant
prominence. The bioethanol production process
is still considered one of the largest energy-consuming
processes and is challenging due to the limited effectiveness
of conventional pretreatment processes, saccharification
processes, and extreme use of electricity in common
fermentation and purification processes. Thus, it became
necessary to improve the bioethanol production process
through reduced energy requirements. Membrane-based
separation technologies have already gained attention
due to their reduced energy requirements, investment in
lower labor costs, lower space requirements, and wide
flexibility in operations. For the selective conversion of
biomasses to bioethanol, membrane bioreactors are specifically
well suited. Advanced membrane-integrated
processes can effectively contribute to different stages of
bioethanol production processes, including enzymatic
saccharification, concentrating feed solutions for fermentation,
improving pretreatment processes, and finally
purification processes. Advanced membrane-integrated
simultaneous saccharification, filtration, and fermentation
strategies consisting of ultrafiltration-based enzyme
recycle system with nanofiltration-based high-density cell
recycle fermentation system or the combination of highdensity
cell recycle fermentation system with membrane
pervaporation or distillation can definitely contribute to
the development of the most efficient and economically
sustainable second-generation bioethanol production
process.

- by Ivan Mijatovic
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- Wastewater Treatment, Activated Sludge, Membrane Bioreactor Technology, Phosphorus

- by Pierre Le-clech
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- Engineering, Membrane Science, Wastewater Treatment, Activated Sludge

The performance of an MBR pilot plant for biological nutrient removal was evaluated during 210 days of operation. The set point values for the internal recycles were determined in advance with the use of an optimisation spreadsheet based on the ASM2d model to optimise the simultaneous removal of C, N and P. The biological nutrient removal (BNR) efficiencies were high from the start of operation with COD and N removal efficiencies of 92 ± 6% and 89 ± 7, respectively. During the course of the experiment P removal efficiencies increased and finally a P-removal efficiency of 92% was achieved. The activity of poly-phosphate accumulating organisms (PAOs) and denitrifying poly-phosphate accumulating organisms (DPAOs) increased and the specific phosphate accumulation rates after 150 days of operation amounted to 13.6 mg P g À1 VSS h À1 and 5.6 mg P g À1 VSS h À1 , for PAOs and DPAOs, respectively.

- by Ignasi Rodriguez-roda and +1
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- Multidisciplinary, Membrane Bioreactor Technology, Biological Nutrient Removal, Phosphorus

A major environmental impact of waste landfilling is the contamination caused by generated leachate. Leachate is the contaminated water that drains from a landfill. Water, during its passage through a landfill, extracts both soluble and suspended solids in the forms of dissolved and particulate organics and inorganics including heavy metals, xenobiotic compounds, and ammonium ions. Further, the composition of leachate dependent upon the age and type of waste contained making treatment major engineering challenges today. Leachate in general is characterized by high COD (6000-60000 mg/L), BOD (4000-13000 mg/L), NH4-N (500-2000 mg/L) and varying BOD/COD ratio (0.1-0.7). Limiting leachate generation is the most desirable option to control but total elimination of generation is almost impossible. Leachate treatment using biological methods; oxidation ponds (OP), sequencing batch reactors (SBR), activated sludge (AS) and up flow anaerobic sludge blankets (UASB) is well documented for ammonia and organics removal. However biological treatment options show less effective in treating mature leachate than young leachate. Among biological methods, the AS, UASB, and SBR have shown over 90% COD removal and over 80% ammonia removal with 3500-25000 mg/L and 100-1000 mg/L initial COD and ammonia concentrations respectively. Among physicochemical methods in practice, activated carbon adsorption, chemical precipitation and reverse osmosis (RO) are widely applied. According to reviewed studies and applications, combined biological and physicochemical systems are the best for treating lechate. For an example AS with RO has shown almost total COD and NH4-N removal. This paper critically reviews the documented technologies for leachate treatment in respect to treatment efficiencies, advantages, and drawbacks of each.

Membrane bioreactors (MBRs) present a means of intensively biologically treating high COD or BOD wastewaters but, like other membrane processes, are constrained by their tendency to foul. Fouling is the general term given to those phenomena responsible for increasing membrane hydraulic resistance. It can be reduced by maintaining turbulent conditions, operating at sub-critical flux and/or by the selection of a suitable fouling-resistant membrane material.

- by Bruce Jefferson
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- Membrane Bioreactor Technology

Membrane BioReactor MBR Technology

El agua como recurso vital es cada vez más escasa por lo que su reúso y el cuidado de las fuentes existentes es imperativo. La tecnología de membranas en el tratamiento ofrece una solución parcial a este problema, pero su difusión y uso es considerablemente pobre en la actualidad. El artículo busca divulgar lo esencial sobre la tecnología e impartir información sobre sus ventajas y desventajas. Las configuraciones de membrana en un biorreactor son diversas y cada una provee diferentes beneficios y usos específicos. El uso de un biorreactor de membrana en el tratamiento de agua es altamente recomendado, dando como resultado efluentes de la mayor calidad. Económicamente su uso es más apropiado a plantas que apuntan a un largo periodo de uso para poder justificar la inversión.

Excess sludge treatment and disposal currently represents a rising challenge for wastewater treatment plants (WWTPs) due to economic, environmental and regulation factors. There is therefore considerable impetus to explore and develop strategies and technologies for reducing excess sludge production in biological wastewater treatment processes. This paper reviews current strategies for reducing sludge production based on these mechanisms: lysis-cryptic growth, uncoupling metabolism, maintenance metabolism, and predation on bacteria. The strategies for sludge reduction should be evaluated and chosen for practical application using costs analysis and assessment of environmental impact. High costs still limit technologies of sludge ozonation-cryptic growth and membrane bioreactor from spreading application in full-scale WWTPs. Bioacclimation and harmful to environment are major bottlenecks for chemical uncoupler in practical application. Sludge reduction induced by oligochaetes may present a cost-effective way for WWTPs if unstable worm growth is solved. Employing any strategy for reducing sludge production may have an impact on microbial community in biological wastewater treatment processes. This impact may influence the sludge characteristics and the quality of effluent. r

- by Yao-bo Fan and +1
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- Water, Wastewater Treatment, Population Dynamics, Environmental Pollution

This review reports all the analytical tools used for the membrane autopsies in seawater feed. Furthermore, we detail the possibilities of all the different types of new possibilities of pretreatments before reverse osmosis (RO) such as microfiltration, ultrafiltration, nanofiltration or membrane bioreactors. The last part gives an account of brine disposal and the possibilities of reusing RO modules for wastewater treatment. For this review a discussion about fresh water prices took place.

- by M. Pontié
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- Engineering, Wastewater Treatment, Membrane Bioreactor Technology, Desalination

This study investigated the feasibility and the treatment efficiency of a cyclic anoxic/aerobic two-stage MBR for treating polymeric industrial wastewater. The anoxic/aerobic hybrid MBR was operated without sludge withdrawal except sampling during the study. The results showed that the highest COD organic loading rate of 8.7 kg COD/m 3 day from bioreactor was obtained at phase 3. The system achieved 97% BOD 5 and 89% COD removal. It also revealed that 93% of COD removal was contributed by bioreactor at phase 3 and the similar results happened to phases 1 and 2. The highest TN and TKN removals for each phase were 60, 74, 80% and 61, 74, 81%, respectively and limited by nitritation step. SEM images of nascent and fouled membranes were offered to evaluate the cleaning method. The system was operated for 174 days, resulting in high degradation rate, flexibility towards influent fluctuations and limited sludge production.