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Membrane fouling has been a key factor limiting the applications of membrane bioreactor (MBR). In this study, a novel umbrella-shape membrane module was applied to construct two MBRs for two-stage partial nitrification-anaerobic ammonia oxidation (PN-ANAMMOX) process. After 55 days operation, the ANAMMOX process was started and the PN process was well controlled. Then, the ANAMMOX and PN process were successfully coupled to run the PN-ANAMMOX process. On 103 days, the best nitrogen removing effect was achieved with the maximum nitrogen loading rate (NLR) of 0.4 kg N·(m3·d)−1 and the corresponding maximum total nitrogen removal rate (TNRR) of 75.23%. The umbrella-shape membrane module in both reactors only needed to be cleaned once during the operation for 105 days, indicating that the membrane module had better resistance to membrane fouling. The functional bacteria were cultivated in suspension state; moreover, the cell densities of ammonia oxidizing bacteria (AOB) and ANAMMOX bacteria (AnAOB) reached 58.32 × 1012 copies/g sludge and 28.39 × 1012 copies/g sludge. Their abundances reached 73.25% and 57.80% of the total bacteria, respectively. MBR improved by umbrella-shape membrane module could realize the rapid start-up of ANAMMOX process, effective control of PN process, and stable operation of PN-ANAMMOX process. This study provided a novel approach to control membrane fouling by optimizing the membrane module shape and widened applications of MBRs in PN-ANAMMOX process. [ABSTRACT FROM AUTHOR]

The behavior of ibuprofen (IBU) during the startup phase of a microfiltration membrane bioreactor (MBR) was determined. A full-scale experimental installation treating real urban wastewater was used for the study. The MBR was composed of an anoxic and an aerobic bioreactors working in pre-denitrification configuration, followed of a membrane reactor. A full mass balance was carried out to estimate the contribution of biotransformation and sorption to biomass to the overall removal of the IBU. During the startup phase of the MBR system there were significant oscillations of the operational variables, mainly of the sludge retention time (SRT); nevertheless, the capacity of the system for IBU removal was very high, with yields of over 94%, despite reaching minimum SRT values of 4.15 d. The main IBU removal occurs in the aerobic reactor, both in the liquid phase and the one associated with the sludge, while in the anoxic bioreactor the removal was scarce, although a certain transfer of IBU from the liquid phase to the sludge took place under anoxic conditions. Despite the high IBU removal yields during startup, the SRT was the most influential variable in IBU removal, an effect observed in all bioreactors, particularly in the anoxic one. [ABSTRACT FROM AUTHOR]

• GO nanosheets were successfully immobilized with PVP. • PVP-GO enhanced the hydrophilicity and pure water flux of membranes. • Fouling of PVDF membranes was decreased owing to the presence of PVP-GO. In this study, the effect of graphene oxide (GO) and polyvinylpyrrolidone (PVP) grafted GO (PVP-GO) on the hydrophilicity and antifouling properties of polyvinylidene fluoride (PVDF) was investigated. PVP-GO was synthesized via surface initiated free radical polymerization method. Successful immobilization of PVP on the GO surface was proved by FTIR and XRD analyses. FESEM results of PVP-GO nanosheets showed that immobilization increased interlayer space between nanosheets which resulted in better dispersion of PVP-GO in PVDF membranes. In addition, the presence of GO and PVP-GO nanosheets resulted in membranes with more and bigger finger-like pores and thinner sponge-like layer. Contact angle measurement, abrasion resistance and pure water flux of membranes containing different percentage of GO and PVP-GO ranging from 0 to 2 wt% were investigated. PVDF/GO (1.5 wt%) and PVDF/PVP-GO (1.5 wt%) showed the best hydrophilicity and pure water permeation and therefore, their performance was compared with neat PVDF in MBR system. The results indicated that the presence of GO and PVP-GO improved antifouling properties of PVDF membrane due to their hydrophilicity. [ABSTRACT FROM AUTHOR]

A novel submerged membrane bioreactor integrated with ozonation and photocatalysis has been developed to treat the real textile wastewater and study the fouling behaviour. This study evaluates the performance efficiency in pilot-scale for the three reactors such as membrane bioreactor, ozonised membrane bioreactor and further clubbed with photocatalysis. The membrane filtration consists of polyvinilidine difluoride hollow fibre membrane module having pore size 0.1 μm. Tungsten oxide, a visible photocatalyst was made into spongy alginate beads and used in photocatalytic reactor. The photocatalyst dose has been optimised as 500 mg/L. About 10% membrane filterability ratio has been achieved by integrating ozone with MBR with the maximal ozone dosage of 5 g/h. It showed better removal efficiency in colour and chemical oxygen demand of 94% and 93% respectively. The biodegradability efficiency also was enhanced from 0.2 to 0.4 with optimised ozone dosage (5 g/h). The study on reversible and irreversible fouling has been done to understand the fouling nature. The important analysis such as microbial community and scanning electron microscopy analysis were done to study the biofouling and extent of fouling after filtration. The treatability studies implemented for textile wastewater showed that integrated MBR systems are suitable in meeting the discharge norms prescribed by the Indian statutory body in terms of chemical oxygen demand, colour and total suspended solids. Image 1 • Novel pilot-scale ozone integrated submerged membrane bioreactor (MBR). • MBR clubbed with photocatalysis for organic removal. • Efficient reduction in colour and chemical oxygen demand for effective reuse. [ABSTRACT FROM AUTHOR]

Sub-visible particles, an often-overlooked fine particle (0.45–10 μ m) with a size between sludge solids and soluble microbial products (SMP), have recently been identified as a critical foulant in anaerobic membrane bioreactors (AnMBRs), and our recent new insights into the size-fractionation and composition of sub-visible particles in AnMBRs have enabled fouling to be understood in more depth. Here, we investigated the microbial diversity of the sub-visible particles in three size fractions (i.e., 5–10, 1–5, and 0.45–1 μ m) from bulk and cake solutions in a lab-scale AnMBR, and their fouling potential was further explored based on their filtration behavior and biofilm formation. Results show that with decreasing particle size, a significant shift in microbial communities was observed for the sub-visible particles in both bulk and cake solutions; (a) with notable decreases in filamentous microbes in the order SJA-15 , GCA004 , and Anaerolineales of phylum Chloroflexi , and, (b) with substantial increases in sulfate-reducing bacteria (i.e., the family Syntrophobacteraceae, genus DCE29 of family Thermodesulfovibrionaceae, Desulfovibri o, and Geobacter). More importantly, the filamentous microbes associated with micro-particles (5–10 μ m) led to higher cake fouling resistances while free living cells in the form of colloidal particles (0.45–1 μ m) induced severer pore blocking. Moreover, the micro-particles had an enhanced capacity to favor biofilm formation (OD595 = 1.0–2.5, categorized as highly positive), thus potentially aggravating biofouling. This work advances our knowledge on the effect of particle size on communities and underlying fouling behavior of microbes associated with fine particles in AnMBRs. Image 1 • Sub-visible particles, an often-overlooked particle (0.45–10 μ m) were the main foulants in AnMBRs. • Microbial diversity of three size fractions (5–10, 1–5, and 0.45–1 μ m) was first studied in AnMBRs. • Colloidal particles (0.45–1 μm) are related to genus DCE29 of family Thermodesulfovibrionaceae. • Filamentous microbes associated with micro-particles (5–10 μm) led to higher cake resistances. • Free living cells in the form of colloidal particles (0.45–1 μm) induced severer pore blocking. [ABSTRACT FROM AUTHOR]

Lab-scale membrane bioreactors (MBRs), with aerated activated sludge and internal microfiltration module, were used for the treatment of municipal wastewater containing high, yet environmentally relevant, concentrations of benzothiazole (BT) and benzotriazole (BTA). These high production volume compounds are commonly used in the industry and households, and therefore occur ubiquitously in municipal wastewater and the aquatic environment. The aim of this study was to assess the removal of BT and BTA from synthetic municipal wastewater in MBRs and to estimate the contribution of elimination processes and to identify potential biotransformation products. The overall removal of BT and BTA was high, and after the adaptation period, it reached 99.8% and 97.2%, respectively, but recurring periods of unstable BTA removal occurred. The removal due to biotransformation was 88% for BT and 84% for BTA and the disposal with waste sludge accounted for only <1% of the removed load. The remaining fraction of the removed load of BT and BTA was attributed to be retained by phenomena associated with membrane fouling. The adaptation process was reflected in multifold increase in biodegradation kinetic coefficient (k biol) for BT (reported for the first time) and BTA. Biodegradation was attributed to catabolic mechanism rather than to cometabolism. Hydroxylation was observed to be the main transformation reaction for BT, whereas for BTA hydroxylation, methylation and cleavage of benzene ring were noted. This study has shown the feasibility of treating municipal wastewater with high concentrations of BT and BTA in MBRs and identified potential challenges for the removal of BTA. • MBRs offered high removal of benzothiazole (BT) and benzotriazole (BTA). • Sludge adaptation led to multi-fold increase in biodegradation kinetics. • Main removal mechanism was catabolic biotransformation. • Membrane fouling improved the retention of the compounds. • Biotransformation reactions for BT and BTA were identified. [ABSTRACT FROM AUTHOR]

• Biological and photocatalysis treatments in-series enabled high TOC removal (ca. 95%). • High photocatalysis performance was achieved because of the MBR pre-treatment. • The addition of K 2 S 2 O 8 reduced the necessity of cumulative impinging energy (60 E). • Membrane fouling mechanisms were the "cake layer deposition" and the "pore blocking". This study investigated the treatment of a shipboard slop containing commercial gasoline in a pilot plant scale consisting of a membrane biological reactor (MBR) and photocatalytic reactor (PCR) acting in series. The MBR contributed for approximately 70% to the overall slop purification. More precisely, the biological process was able to remove approximately 40%, on average, of the organic pollution in the slop. Nevertheless, the membrane was capable to retain a large amount of organic molecules within the system, amounting for a further 30% of the influent total organic content removal. However, this affected the membrane fouling, thus resulting in the increase of the pore blocking mechanism that accounted for approximately 20% to the total resistance to filtration (2.85∙1013 m−1), even if a significant restoration of the original membrane permeability was obtained after chemical cleanings. On the other hand, the biological treatment produced a clear solution for the photocatalytic system, thereby optimizing the light penetration and generation of highly oxidizing active oxygen species that enabled the degradation of bio-recalcitrant compounds. Indeed, low total organic carbon (TOC) values (<10 mg L−1) were achieved in the output of the photocatalytic reactor by means of only 60 Einstein (E) of cumulative impinging energy after the addition of K 2 S 2 O 8. Overall, coupling the two processes enabled very high TOC removal (ca. 95%). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Removal of PPCPs in MBR under limited and infinite SRT condition were studied. • High (>80%) DCF, TMP, NPX, IBP, TCS but low (<20%) CBZ removals were observed. • Removals via biodegradation, adsorption onto coarse and fine particles were quantified. • Adsorption onto fine particles and gel-like substances were important for PPCP removals. • Increased biomass under long SRT condition enhanced the removals of several PPCPs. Abstract Removals of 10 pharmaceutical compounds by microbial sludge in membrane bioreactors (MBR) operated under infinite and limited solid retention time (SRT) were investigated. High removal (>80%) of DCF, TMP, NPX, IBP, and TCS were achieved but CBZ removals were low (<20%). The residual pharmaceutical compounds leftover from the biodegradation in different sludge particle size fractions was quantified through physical separation and filtration in series. The results revealed that hydrophobic compounds were mainly adsorbed onto the coarse particles (>0.45μm) where majority of adsorption site was available. Meanwhile, hydrophilic and moderate hydrophobic compounds were less associated with particles and they were retained in fine particles and gel-like substances (1 kDa–0.45μm). Most of the studied pharmaceutical compounds associated with fine particles and gel-like substances was subsequently rejected by membrane filtration in the MBRs. The operation of the MBR at high mixed liquor suspended solids concentration under long sludge age conditions could enhance the removals of pharmaceutical compounds through increased adsorption site on the sludge particles. [ABSTRACT FROM AUTHOR]

This work reports on the use of a bench-scale chemostat (CSTR) in continuous mode and of a pilot-scale membrane bioreactor (MBR) in fed-batch mode to intensively produce acetic and butyric acids using C. butyricum grown on synthetic media. These studies were then used to perform a cost estimation study of the MBR system to assess the potential economic impact of this proposed methodology, regarding the production of carboxylic acids. The MBR system was found to be highly productive, reaching 37.88 g L-1 h-1 of acetic and 14.44 g L-1 h-1 of volumetric cell productivity, favoring acetic acid production over butyric acid at a ratio of 3 moles to 1. The cost of preparation and production of carboxylic acid using this system was found to be 0.0062 £PS/kg with up to 99% carbon recovery. [ABSTRACT FROM AUTHOR]

This research investigates the fouling behavior of reverse osmosis (RO) membranes in an integrated membrane bioreactor (MBR)-RO system for landfill leachate treatment. In a long-term operation under natural alkaline condition (pH 8.0–8.5), a full-scale integrated MBR-RO system achieved high treatment efficiencies (>95%) but suffered RO membrane fouling as a result of calcium scaling. Specifically, in the study, the mixed liquor pH in MBR was varied between 5.5, 6.5, 7.5, and 8.5, and the effect on RO membrane fouling examined in laboratory-scale experiments. The results showed that pH influenced the removal of dissolved organic matters in the MBR and the characteristics of MBR permeates. At pH 5.5, the deposition of protein-like substances substantially reduced the RO flux, and calcium scaling on the RO membrane was clearly visible under pH 8.5. The RO flux slightly decreased under pH 6.5 and 7.5. The optimal pH for treating landfill leachate using the integrated MBR-RO system was between 6.5 and 7.5. [ABSTRACT FROM AUTHOR]

This review, for literature published in 2017, contains information related to membrane processes for municipal and industrial applications. This review is a subsection of the Treatment Systems section of the annual Water Environment Federation literature review and covers the following topics: membrane bioreactor (MBR) configuration, design, nutrient removal, operation, industrial treatment, anaerobic membrane systems, reuse, microconstituents removal, membrane technology advances, membrane fouling, and modeling. Other sub-sections of the Treatment Systems section that might relate to this literature review include: Biological Fixed-Film Systems, Activated Sludge and Other Aerobic Suspended Culture Processes, Anaerobic Processes, and Water Reclamation and Reuse. The following sections might also have related information on membrane processes: Industrial Wastes, Hazardous Wastes, and Fate and Effects of Pollutants. [ABSTRACT FROM AUTHOR]

Water supply was vital to people's life, especially inside Controlled Ecological Life Support System (CELSS) for long-term space exploration. A platform of 4-person-180-day integrated experiment inside a CELSS including 6 cabins called ‘SPACEnter’ was established in Shenzhen, China. Based on this platform, a Membrane Bio-Reactor (MBR) system configuring post advanced purification, including I-MBR, II-MBR, nanofiltration (NF), reverse osmosis (RO), ion-exchange (IE), polyiodide disinfection (PI) and mineralization (MC) stages, used as a Domestic Water Supply System (DWSS) to guarantee crew's daily life was constructed. The performance of DWSS to treat the real plant cabin's condensate water was examined during continuously 180-day experiment. The long-term operation results showed that, though the influent pollutant load changed as the experiment processing, the system exhibited stable performance on pollutants removal with average effluent TOC＜0.5 mg/L, NH 4 + -N＜0.02 mg/L, NO 3 − -N＜0.25 mg/L, NO 2 − -N＜0.001 mg/L, and displayed good capacity for controlling the trace metal ions and microorganism. The effluent through such modified MBR system was sufficiently allocated as hygiene water and potable water, and the average value was 39.69 and 10.93 L/d, respectively. The consumption of the modified MBR process was within the designed allowable scope. The outcomes of this study will be helpful for facilitating future applications of MBR as bio-based water supply technology in the CELSS. [ABSTRACT FROM AUTHOR]

Environmental deterioration together with the need for water reuse and the increasingly restrictive legislation of water quality standards have led to a demand for compact, efficient and less energy consuming technologies for wastewater treatment. Aerobic granular sludge and membrane bioreactors (MBRs) are two technologies with several advantages, such as small footprint, high-microbial density and activity, ability to operate at high organic- and nitrogen-loading rates, and tolerance to toxicity. However, they also have some disadvantages. The aerobic granular sludge process generally requires post-treatment in order to fulfill effluent standards and MBRs suffer from fouling of the membranes. Integrating the two technologies could be a way of combining the advantages and addressing the main problems associated with both processes. The use of membranes to separate the aerobic granules from the treated water would ensure high-quality effluents suitable for reuse. Moreover, the use of granular sludge in MBRs has been shown to reduce fouling. Several recent studies have shown that the aerobic granular membrane bioreactor (AGMBR) is a promising hybrid process with many attractive features. However, major challenges that have to be addressed include how to achieve granulation and maintain granular stability during continuous operation of reactors. This paper aims to review the current state of research on AGMBR technology while drawing attention to relevant findings and highlight current limitations. [ABSTRACT FROM AUTHOR]

The biotoxicity of industrial effluents has attracted much concern in the wastewater treatment process. This research performed the biological treatment of the wastewater generated from food waste fermentation by anaerobic/anaerobic/anoxic/aerobic-membrane bioreactor (A3-MBR) system aiming at the meet of discharge standards and elimination of ecological risks to aquatic environment. The results showed that the A3-MBR could effectively remove pollutants such as COD, TN, ammonia, and TP in the wastewater. The study of biotoxicity revealed that the acute toxicity was mainly contained in the polar and mid-polar fractions of the wastewater, and the remained acute toxicity was less than 0.6 TU, much lower than the secondary effluent of domestic wastewater treatment plant. The genotoxicity was found abundantly in the polar fractions and less in mid-polar fractions, and a relatively low genotoxicity (0.086 μg 4-NQO/L) was obtained in the final effluent of the treatment system. The fulvic acid-like compounds and humic acid-like compounds were the main cause of the acute toxicity, while the aromatic proteins and soluble microbial by-products mainly resulted in the genotoxicity in the wastewater. [ABSTRACT FROM AUTHOR]

The performance of a pilot ceramic membrane bioreactor for the bioconversion of H 2 and CO 2 to bioCH 4 was evaluated in thermophilic conditions. The loading rate was between 10 and 30 m 3  H 2 /m 3 reactor  d and the system transformed 95% of H 2 fed. The highest methane yield found was 0.22 m 3  CH 4 /m 3  H 2 , close to the maximum stoichiometric value (0.25 m 3  CH 4 /m 3  H 2 ) thus indicating that archaeas employed almost all H 2 transferred to produce CH 4 . k L a value of 268 h −1 was reached at 30 m 3  H 2 /m 3 reactor  d. DGGE and FISH revealed a remarkable archaeas increase related to the selection-effect of H 2 on community composition over time. Methanothermobacter thermautotrophicus was the archaea found with high level of similarity. This study verified the successful application of membrane technology to efficiently transfer H 2 from gas to the liquid phase, the development of a hydrogenotrophic community from a conventional thermophilic sludge and the technical feasibility of the bioconversion. [ABSTRACT FROM AUTHOR]

Quorum quenching (QQ) has been used to control biofouling in membrane bioreactors (MBRs), but the effect of QQ on the performance of MBR has not been systematically studied. This study investigated the effect of QQ on ammonia removal in MBR especially in some stressful conditions. The results showed that membrane fouling was effectively alleviated by QQ in all conditions. For the short HRT (3.94 h), the ammonia removal in QQ-MBR was fluctuating. In the presence of nitrification inhibitors (acetonitrile and allylthiourea) or at low temperature (10 °C), QQ induced much more significant suppression on nitrification in batch test and MBR. The number of the ammonia oxidizing bacteria (AOB) was not decreasing in these situations, which indicated that QQ only suppressed the activity of AOB. In all, comprehensive considerations should be taken into account when applying a QS tuning strategy to a bioreactor. [ABSTRACT FROM AUTHOR]

Submerged membrane bioreactor (MBR) is currently believed to be an efficient biological treatment for reusing and recovering wastewater to extenuate the ever increasing water scarcity crisis. To mitigate the main problem, membrane fouling, in MBR systems, we propose a solution that avoids usage of chemicals, and allows uninterrupted operation using a novel concept of obstacle dielectrophoresis (oDEP). The utilization of obstacles, insulator or metal (floating) electrodes, between electrically excited electrodes, can extend the DEP force field to move suspended particles away from membranes without having to increase voltage, for suppressing fouling with low energy consumption. Experimental investigation verified our theoretical simulation prediction and demonstrated that insulator membrane modules provide longer membrane service time for maintaining normalized permeate flux of 55% than those by floating electrode membrane modules, with a maximum intensification factor of 7.8 when applied 220 V voltage and 50 Hz as well as the transmembrane pressure of 0.1 bar. Although stronger DEP force and hence better performance of fouling suppression can be generated by higher voltage, 50 V insulator membrane module demonstrated to be the most energy efficient process with a specific energy consumption of 0.295 kWh/m 3 product and 13 times higher efficient factor than the 220 V. [ABSTRACT FROM AUTHOR]

Despite that anaerobic ammonium oxidizing (anammox) bacteria are key players in the global nitrogen cycle, no pure cultures are still available. Planktonic cell culture with high purity is, therefore, essential for physiological and biochemical studies of anammox bacteria. However, development of such planktonic cell cultures requires an enormous amount of time and effort. Here we developed a novel rapid method for cultivating free-living planktonic anammox cells. First, anammox granules were physically dispersed, immobilized in 6% polyvinyl alcohol–4% sodium alginate (PVA-SA) gel beads, and then pre-cultured in an up-flow column reactor. Anammox bacteria grew rapidly as loosely flocculated micro-clusters in the gel beads. After 18 days of pre-cultivation, mature gel beads were harvested, physically dispersed by vortex and inoculated into a membrane bioreactor (MBR). The MBR was then continuously operated at a low nitrogen loading rate (<0.9 kg-TN m −3 d −1 ). After 17 days of operation, active free-living planktonic anammox cells with purity >95% were successfully developed in the MBR. Total culture time (gel beads and MBR) to accomplish free-living planktonic anammox cells was only 35 days, which was significantly shorter than the previous reports. This new cultivation technique could greatly facilitate various microbial, physiological and biochemical studies of anammox bacteria. [ABSTRACT FROM AUTHOR]

The removal of 10 organic micropollutants (OMPs) was studied in two MBRs using different types of membrane (flat sheet microfiltration, MF, and hollow fiber ultrafiltration, UF) operated under aerobic conditions with direct dosing of powdered activated carbon (PAC) in the mixed liquor. In both reactors high COD degradation and nitrification were achieved (>95%), while nitrate removal was only observed after PAC addition. The adsorbent improved the operation of both systems (sludge properties and microbial diversity) which resulted in an enhancement of the quality of the final effluent. The operation with both types of membrane was feasible being the UF system slightly better in terms of the quality of the final effluent. The strategy of 250 mg/L of PAC additions every 35 days was validated according to the results obtained for the removal of the most recalcitrant OMPs, such as diclofenac and carbamazepine. Concerning the type of membrane, only significant differences were observed for diclofenac and roxithromycin, which were better removed in the UF configuration. These differences were attributed to sorption and/or further biotransformation processes occurring in the cake layer. [ABSTRACT FROM AUTHOR]

In this study, the anaerobic baffled reactor contained sediment microbial fuel cell (MFC) was combined with anaerobic/aerobic membrane bioreactor (AnMBR/MBR). The brewery wastewater treatment and membrane fouling mitigation strategies were studied comprehensively. During anaerobic treatment process in this study, the chemical oxygen demand (COD) removal ratio of brewery wastewater could be maintained at 73.87% when the hydraulic retention time (HRT) was reduced from 42.44 h to 22.60 h. For membrane fouling mitigation in AnMBR, regular aeration was more effective than back flush, and the fouling could be inhibited further when both controlling ways were adopted at the same time. For membrane fouling mitigation in AnMBR of this study, only 0.52%–0.99% of electric energy was required for fouling mitigation, but 31.80% of energy was needed in MBR. [ABSTRACT FROM AUTHOR]

This review, for literature published in 2016, contains information related to membrane processes for municipal and industrial applications. This review is a subsection of the Treatment Systems section of the annual Water Environment Federation literature review and covers the following topics: membrane bioreactor (MBR) configuration, design, nutrient removal, operation, industrial treatment, anaerobic membrane systems, reuse, microconstituents removal, membrane technology advances, membrane fouling, and modeling. Other sub-sections of the Treatment Systems section that might relate to this literature review include: Biological Fixed-Film Systems, Activated Sludge and Other Aerobic Suspended Culture Processes, Anaerobic Processes, and Water Reclamation and Reuse. The following sections might also have related information on membrane processes: Industrial Wastes, Hazardous Wastes, and Fate and Effects of Pollutants. [ABSTRACT FROM AUTHOR]

The research compares four types of different designs of membrane bioreactors: (1) with 295-mm draft tube and without plastic carriers; (2) plastic carriers and 295-mm draft tube; (3) plastic carriers and 235-mm draft tube with two meshes around the bottom and top of a draft tube; and (4) plastic carriers without a draft tube. The feed for the reactors was artificial wastewater made from domestic wastewater and chicken manure, and membrane test data were based on a hollow fiber membrane module under ambient desert conditions. Process operation type D is the optimal choice. Mathematical analysis using total ranking methods, multi-indicator decision-making, and Hasse diagram support this choice. Concerning analysis by the different tools, inconsistencies between the rankings are noticed. Partial order ranking, as a method without any pre-assumptions concerning the possible relation between the single parameters, proves to be an elegant ranking method. [ABSTRACT FROM PUBLISHER]

Organized industrial zone (OIZ) wastewater is a mixed wastewater that is contributed by both municipal use and from different industrial sectors. Since MBR has advantages over conventional treatment plants, membrane types and fouling become the most important parameters in the treatment of this kind of wastewater. In this study, six different membrane types were used to find the most suitable membrane with the least resistivity to fouling. Three different microfiltration (MF) and ultrafiltration (UF) membranes were operated to estimate their (i) membrane, (ii) cake, (iii) pore, and (iv) total resistances. The highest total resistance was observed in a polyethersulfone (PES) membrane (3.8 × 1010 m-1), while the lowest one was a UF polyvinylidene fluoride (PVDF) membrane with approximately 20 times lower resistance than the highest one. PVDF membranes showed lower total resistances than PES membranes. An MF or a 250 kDa UF membrane could be operated long-term in a membrane bioreactor with the least fouling potential. [ABSTRACT FROM AUTHOR]

The fouling control mechanisms were elucidated in the membrane bioreactor (MBR) by investigating the cake layer specifications in the different hydraulic retention times (HRTs). In this study, petrochemical wastewater was used. The sludge particle size distribution (PSD), excitation-emission matrix (EEM) fluorescence spectra, compressibility cake layer, Fourier transform infrared spectroscopy (FTIR) profile and extracellular polymeric substance (EPS) were measured to determine cake layer characteristics. The results showed that the particle size in the cake layer decreased with reduction in HRT while EPS concentration and transmembrane pressure (TMP) slope increased by time. The EEM florescence spectra of the cake layer showed the existence of two obvious protein-like substance peaks at the wavelength of Ex/Em of 290/355 and Ex/Em of 230–240/355 nm at different HRTs. Furthermore, a feed forward artificial neural network (ANN) was trained using back propagation algorithms for prediction effluent chemical oxygen demand (COD) and TMP. The best structure was a trainlm network with two layers including 17 and 2 neurons in the hidden layer and output layer, respectively. Sensitivity analysis showed that the most and the least sensitive parameters on TMP were mixed liquor suspended solid (MLSS) and time, respectively. [ABSTRACT FROM AUTHOR]

The laboratory scale of the two-stage membrane bioreactor (2S-MBR) was investigated to find the optimal hydraulic retention times (HRT) in treatment of selected 10 antibiotics in real hospital wastewater. It showed that elimination of the antibiotics varied, depending upon antibiotic types and HRT. High biodegradation attributed to amoxicillin and clarithromycin. Fluoroquinolones/tetracycline adsorbed highly on anoxic (ANX) sludge, but tended to be biodegraded in the aerobic tank. Sulfamethoxazole/trimethoprim were mainly accumulated in the ANX/aerobic sludge. In order to increase biodegradation, 2S-MBR was upgraded to a three-stage MBR (3S-MBR) using the polyvinyl alcohol and sodium alginate (PVA/SA) beads of Pseudomonas putida (TISTR1522) in an entrapped cells reactor (ECR) as a pretreatment unit. Ciprofloxacin (CIP) in a synthetic wastewater was a refractory antibiotic for this feature investigation. It showed improvement of CIP degradation reached to 90% in 3S-MBR as compared to 58% of 2S-MBR. As a result, 24 CIP-transformed products (TPs) were detected. Additionally, 3S-MBR showed better efficacy of nitrogen removals. The SEM and FISH techniques revealed bacterial consortium in the system showing that the beads were well supported P. putida growth as well as synchronizing volume available for other bacteria. This feature makes P. putida being a potential microorganism for CIP biodegradation via bioaugmentation in 3S-MBR. [ABSTRACT FROM AUTHOR]

The antifouling efficiency and mechanisms of a novel membrane surface modification strategy, namely lipophilic bismuth dimercaptopropanol nanoparticle (BisBAL-NP) coating, were evaluated by using a lab-scale nitrification membrane bioreactor. Filtration performance, bismuth leaching, extracellular polymeric substances (EPS) composition, microbial community structure and function were compared for the control and BisBAL-NP coated ultrafiltration membranes. The coated membrane resulted in up to 17.5% higher flux, 33.0% lower biofilm thickness, and 47.0% less cell volume than the control membrane during 1-, 3-, and 5-day filtration tests operated under constant transmembrane pressure. Bismuth leached into bioreactor suspension after the 5-day filtration was about 10% of the total coated materials, and was not detected in the filtration permeate. High-throughput sequencing revealed that the community composition of suspended sludge differed significantly from the membrane biofilm community. Heterotrophic Xanthomonas spp. were identified as the major surface colonizer on the coated membrane, indicating its low sensitivity to BisBAL NPs. Based on the predicted functional traits of the membrane biofilm communities, antioxidant and DNA repair pathways were among the major molecular targets of BisBAL NPs. Overall, lipophilic BisBAL-NP coating could be a novel, safe, and effective solution to membrane biofouling, offering improved filtration efficiency and extended membrane lifespan. [ABSTRACT FROM AUTHOR]

The nanofiltration (NF) membrane fouling characteristics and cleaning strategies were investigated through a laboratory-scale NF fouling test treating membrane bioreactor (MBR) effluent and MBR-granular activated carbon (GAC) effluent of an antibiotic production wastewater by DK and NF90 membranes, respectively. Results showed that organic fouling is the main NF membrane fouling for treating both the MBR effluent and MBR-GAC effluent. Soluble microbial by-product (SMP)-like and aromatic protein-like substances were the dominant components in the foulants, whereas humic-like substances had little contribution to the NF fouling. The fouling of DK was more severe than that of NF90. However, foulants respond by UV were more easily to foul NF90 membrane. It could get satisfactory effect using combined cleaning of acid (HCl, pH 2.0∼2.5) and alkali (NaOH + 0.3 wt% NaDS, pH 10.0∼10.5). The favorable cleaning strategy is 'acid + alkali' for treating MBR-GAC effluent, while it is 'alkali + acid' for treating MBR effluent. [ABSTRACT FROM AUTHOR]

In this study, a lab-scale biological anaerobic/anaerobic/anoxic/membrane bioreactor (A³-MBR) was designed to treat wastewater from the ethanol fermentation of food waste, a promising way for the disposal of food waste and reclamation of resources. The 454 pyrosequencing technique was used to investigate the composition of the microbial community in the treatment system. The system yielded a stable effluent concentration of chemical oxygen demand (202 ± 23 mg/L), total nitrogen (62.1 ± 7.1 mg/L), ammonia (0.3 ± 0.13 mg/L) and total phosphorus (8.3 ± 0.9 mg/L), and the reactors played different roles in specific pollutant removal. The exploration of the microbial community in the system revealed that: (1) the microbial diversity of anaerobic reactors A1 and A2, in which organic pollutants were massively degraded, was much higher than that in anoxic A3 and aerobic MBR; (2) although the community composition in each reactor was quite different, bacteria assigned to the classes Clostridia, Bacteroidia, and Synergistia were important and common microorganisms for organic pollutant degradation in the anaerobic units, and bacteria from Alphaproteobacteria and Betaproteobacteria were the dominant microbial population in A3 and MBR; (3) the taxon identification indicated that Arcobacter in the anaerobic reactors and Thauera in the anoxic reactor were two representative genera in the biological process. Our results proved that the biological A³-MBR process is an alternative technique for treating wastewater from food waste. [ABSTRACT FROM AUTHOR]

Membrane fouling is an important issue for membrane bioreactor (MBR) operation. This paper aims at the investigation and the controlling of reversible membrane fouling due to cake layer formation and foulants deposition by optimizing MBR hydrodynamics through the combination of computational fluid dynamics (CFD) and design of experiment (DOE). The model was validated by comparing simulations with measurements of liquid velocity and dissolved oxygen (DO) concentration in a lab-scale submerged MBR. The results demonstrated that the sludge concentration is the most influencing for responses including shear stress, particle deposition propensity (PDP), sludge viscosity and strain rate. A medium sludge concentration of 8820 mg L −1 is optimal for the reduction of reversible fouling in this submerged MBR. The bubble diameter is more decisive than air flowrate for membrane shear stress due to its role in sludge viscosity. The optimal bubble diameter was at around 4.8 mm for both of shear stress and PDP. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the potential use of ozonation with pharmaceutical compounds on membrane bioreactor (MBR). The result has shown that high concentrations of pharmaceutical contaminants have caused destruction of cell wall, thereby reducing mixed liquor suspended solids (MLSS). It also resulted in high amounts of biopolymers in the presence of non-biodegradable pharmaceutical compound in MBR. As a result, biological removal decreased and membrane fouling happened. Ozonation treatment reached a chemical Oxygen Demand (COD) removal of 99.9% and caused better effluent quality. The MBR-ozonation process could achieve an acetaminophen and fluoxetine removal of around 98.4 and 57.83%, respectively. [ABSTRACT FROM AUTHOR]

Foam formation in the excess sludge treatment facilities of biological wastewater treatment plants (WWTPs) may represent a critical issue as it could lead to several operative problems and reduce the overall plant performance. This trouble also affects a novel technology recently proposed for sludge minimization, the thermophilic membrane reactor (TMR), operating with alternate aeration/non-aeration cycles. This technology, which has proven to be extremely resilient and suitable for treating industrial wastewater of different nature, demonstrated a high potential also as a solution for integrating existing WWTPs, aiming at the 'zero sludge production.' In this work, an experimental study was conducted with a TMR pilot plant (fed daily with thickened sewage sludge) by adjusting the duration of aeration/non-aeration alternate cycles. Extracellular polymeric substance (EPS) concentration (and its soluble and bound fractions) has been monitored along with foaming power indices. The results highlight that foaming can be correlated to the presence of soluble protein fraction of EPS. Moreover, EPS production seems to be reduced by increasing the duration of the non-aeration cycles: optimal operating conditions resulted 2 h of aeration followed by 6 h of non-aeration. These conditions allow to obtain an EPS concentration of 500 mg L with respect to 2300 mg L measured at the beginning of experimental work. [ABSTRACT FROM AUTHOR]

The nitrogen content in treated wastewater is a key issue when considering discharge in sensitive areas or reuse targets as standards are getting increasingly stringent. In this study, a Membrane Biological Reactor (MBR), mainly dedicated to nitrogen removal through a nitrification-denitrification process was investigated in order to identify the minimum amount of organic matter that allows complete denitrification. Thus, the Minimum COD/N Ratio, referred to as MR, was assessed using activated sludge modeling (ASM3). Both lab-scale experiments and modeling results pointed out that endogenous denitrification could have a major role in nitrate removal. This role can be strengthened at high Solid Retention Times (SRT). Furthermore, the dissolved oxygen, provided by mixed liquor recirculation between aerobic and anoxic compartments, hindered the denitrification rate. An analytical expression for an apparent Minimum Ratio (MRA) was developed, taking into account previously described processes. This allowed the influent COD to be adjusted to ensure complete denitrification. MRA depends on main design characteristics and operating parameters, mainly the SRT, the anoxic compartment volume, the dissolved oxygen in the aerobic tank and the recirculation rate. For an SRT ranging from 40 to 60 d, laboratory experiments showed that, contrary to a COD/N ratio of 5, a value of 3.5 led to non-stable nitrate removal performances. This was consistent with the assessed MRA, estimated at approximately 4, for identical operating conditions and design characteristics. [ABSTRACT FROM AUTHOR]

Modeling and optimization tools play a key role in membrane fouling control in membrane bioreactor (MBR) systems by delineating the more important variables involved. In this study, the influence of sludge retention time (SRT), aeration rate and filtration mode on hollow fiber membrane fouling was investigated. Using the response surface methodology (RSM) for modeling and central composite rotatable design (CCRD) for design of experiments, mathematical models were developed for fouling rate and protein (PI, P2) and carbohydrate (Cl, C2) concentrations in two layers of fouling. Results showed that sludge retention time (SRT) was the most important variable in most models followed by aeration rate. Aeration showed a more effective role on the models of the rinsed layer (PI, Cl) than backwashed layer (P2, C2). Backwashed layer had more influence on total fouling rate than rinsed layer. The optimal point for MBR operation was: SRT = 30 days, aeration = 10.7 L/min, relaxation interval = 8.8 minutes, and relaxation duration = 41.8 seconds. Water Environ. Res., 88, 2198 (2016). [ABSTRACT FROM AUTHOR]

BACKGROUND The presence of dissolved methane is an important environmental problem related to greenhouse gas emissions from wastewater treated in methanogenic bioreactors. Methane has a global warming potential of 28. For low-strength wastewaters, such as sewage, dissolved methane could account for up to 50% of the total methane produced. Dissolved methane is easily desorbed from effluents when released into the environment or post-treated in aerobic bioreactors. The use of dissolved methane as a carbon source for biological denitrification has been proposed as an alternative for reducing both greenhouse gas emissions and nitrogen concentrations in treated wastewater. RESULTS The effluent of a methanogenic reactor operating at ambient temperature was post-treated in a two-compartment biological membrane bioreactor ( MBR). The first compartment consisted of an anoxic denitrification reactor in which dissolved methane was oxidized. The second compartment was an aerobic membrane filtration reactor. Up to 60% nitrogen removal and 95% methane consumption were observed. Batch experiments indicated the presence of microorganisms that were capable of denitrification using dissolved methane. CONCLUSIONS Denitrification using dissolved methane as a carbon source was feasible in an anoxic-aerobic MBR system. Denitrification resulted from a mixture of aerobic and anaerobic methane oxidizing bacteria, anammox and heterotrophic bacteria activity. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Organic micro-pollutants (OMPs) are contaminants of emerging concern in wastewater treatment due to the risk of their proliferation into the environment, but their impact on the biological treatment process is not well understood. The purpose of this study is to examine the effects of the presence of OMPs on the core microbial populations of wastewater treatment. Two nanofiltration-coupled membrane bioreactors (aerobic and anaerobic) were subjected to the same operating conditions while treating synthetic municipal wastewater spiked with OMPs. Microbial community dynamics, gene expression levels, and antibiotic resistance genes were analyzed using molecular-based approaches. Results showed that presence of OMPs in the wastewater feed had a clear effect on keystone bacterial populations in both the aerobic and anaerobic sludge while also significantly impacting biodegradation-associated gene expression levels. Finally, multiple antibiotic-type OMPs were found to have higher removal rates in the anaerobic MBR, while associated antibiotic resistance genes were lower. [ABSTRACT FROM AUTHOR]

Sludge dewatering represents, nowadays, one of the greatest operational cost to wastewater treatment cycle. Physical–chemical and biological parameters are recognized to influence the sludge dewaterability. However, many authors agree in identifying the sludge origin as one of the main aspect involved in sludge dewaterability. Indeed, the sludge origin such as the processes involved in liquid–solid separation, seriously affect the sludge features. In order to elucidate the key factors influencing the dewaterability process, the present work is aimed to investigate the influence of the treatment plant lay-out on sludge dewaterability. The analyzed sludge samples were derived from four conventional activated sludge and two membrane bioreactor wastewater treatment plants. Experimental investigation was focused to highlight difference in sludge dewaterability derived from the application of European Standards adopted for sludge characterization. The achieved results confirmed the complexity of the inter-relationships between many factors affecting the sludge dewaterability. [ABSTRACT FROM PUBLISHER]

The production of high quality effluent from membrane bioreactors (MBRs) arguably requires less supervision than conventional activated sludge (CAS) processes. Nevertheless, the use of membranes brings additional issues of activated sludge filterability, cake layer formation and membrane fouling. From a practical standpoint, process engineers and operators require simple tools which offer timely information about the biological health and filterability of the mixed liquor as well as risks of membrane fouling. To this end, a range of analytical tools and biological assays are critically reviewed from this perspective. This review recommends that Capillary Suction Time (CST) analysis along with Total Suspended and Volatile Solids (TSS/VSS) analysis is used daily. For broad characterisation, total carbon and nitrogen analysis offer significant advantages over the commonly used chemical and biological oxygen demand (COD/BOD) analyses. Of the technologies for determining the vitality of the microbial biomass the most robust and reproducible, are the second generation adenosine-5′-triphosphate (ATP) test kits. Extracellular polymer concentrations are best monitored by measurement of turbidity after centrifugation. Taken collectively these tools can be used routinely to ensure timely intervention and smoother operation of MBR systems. [ABSTRACT FROM AUTHOR]

The behaviour and fate of carbamazepine (CBZ) in urban wastewater treatment by a membrane bioreactor (MBR) and its possible effects on the system's efficiency, and on mixed microbial communities, has been studied. The experimental microfiltration MBR system, with capacity to treat 10.8 m3d−1of urban wastewater, operated with a pre-denitrification configuration with high sludge and hydraulic retention time. The CBZ concentration assayed was higher than in the usual urban wastewater, in order to provoke a strong biomass reaction. Influent, effluent, and all bioreactors of the MBR system were analysed in order to calculate a CBZ balance. Bench-scale experiments and respirometric analyses were performed, with and without the presence of CBZ, to evaluate its influence on the bacterial activity. The respirometric assays showed variations in the oxygen uptake rate (OUR) in the presence of CBZ. Negative effects were detected in the MBR bacterial community during the initial period of dosing. However, the effects were not permanent and the biomass spiked with CBZ had behaviour similar to that of the biomass without CBZ after a few hours. Biodegradation was not detected during the MBR treatment. The system showed an inefficient elimination of CBZ (less than 10%) with a high concentration in the effluent. The small percentage of CBZ removal was associated with the sludge retention and eliminated by the purge. All CBZ present in the influent was accounted for, and even an increase in the total amount of CBZ was registered in the permeate. During and after the experimental process, CBZ did not significantly affect the efficiency of the MBR system, and the quality of the effluent was not affected by the dosing of CBZ in terms of COD and nitrogen removal. [ABSTRACT FROM PUBLISHER]

In the last years, biological treatment plants for the previously separated organic fraction from municipal solid wastes (OFMSW) have gained importance. In these processes a liquid effluent (liquid fraction from the digestate and leachate from composting piles), which has to be treated previously to its discharge, is produced. In this paper, the characteristics of the mixed liquor from two full-scale membrane bioreactors treating the effluents of two OFMSW treatment plants have been evaluated in view to study their influence on membrane fouling in terms of filterability. For that, the mixed liquor samples have been ultrafiltrated in an UF laboratory plant. Besides, the effect of the influent characteristics to MBRs and the values of the chemical and physical parameters of the mixed liquors on the filterability have been studied. Results showed that the filterability of the mixed liquor was strongly influenced by the soluble microbial products in the mixed liquors and the influent characteristics to MBR. Permeate flux of MBR mixed liquor treating the most polluted wastewater was considerable the lowest (around 20 L/m 2 h for some samples), what was explained by viscosity and soluble microbial products concentration higher than those measured in other MBR mixed liquor. [ABSTRACT FROM AUTHOR]

In this study, two times more serious membrane fouling was found in anammox membrane bioreactor, compared to partial nitrification membrane bioreactor (PN–MBR) operated at the same nitrogen loading rate. By protein, polysaccharide, amino acids and functional groups analysis, it was found that the discrepancy in membrane fouling was virtually due to the difference in microbial products of nitrifiers and anammox bacteria. Protein and polysaccharide were main foulants on membrane surface; meanwhile theirs content and ratio in the EPS, supernatant and membrane surface were significantly different in PN–MBR and anammox–MBR. The anammox metabolism products contained much more hydrophobic organics, hydrophobic amino acids, and hydrophobic functional groups than nitrifiers. A mass of anammox bacteria as well as hydrophobic metabolism products deposited on the hydrophobic membrane surface and formed serious fouling. In further, hydrophilic modification is more urgently needed to mitigate membrane fouling when running anammox–MBR, than PN–MBR. [ABSTRACT FROM AUTHOR]

Advanced oxidation processes (AOP) can be combined with biological treatments for recalcitrant organic pollutant decomposition. However, there has been no thorough investigation on the coupling of AOPs and membrane bioreactors (MBR) to treat polymer organic pollutants. This study proposes a new AOP that couples electron beam (EB) radiation and MBR treatment. This method was applied to treat real textile effluents containing polyvinyl alcohol (PVA). During the stable operation stage, 31 ± 7% (n = 28) COD was removed by the EB-MBR process. COD removal was enhanced to 45% at the end of the research period without process optimization. In addition, both the membrane flux and activated sludge system exhibited good stability. Only a 2% membrane flux decreased was observed after a 46 d operation period. PVA radiolysis and biofacies analysis mechanisms are also discussed. By contrast, PVA degradation using only the MBR treatment was ineffective in this study. This ineffectiveness was caused by membrane interception and floccule formation by PVA and activated sludge. [ABSTRACT FROM AUTHOR]

Pilot-scale membrane bioreactor (MBR) was operated at a short hydraulic retention time (HRT) of 3 h for the treatment of hospital wastewater. The removals of eleven pharmaceutical compounds in MBR operated at different mixed liquor suspended solids (MLSS) level were investigated during which nitrification degree was differed. The results experiments revealed the importance of immediate adsorption onto the colloidal particles in supernatant of MBR sludge and subsequently removed by membrane filtration for the recalcitrant pharmaceutical compounds. Nevertheless, the removals through biodegradation during short HRT were also found significant for some compounds. DGGE profile revealed the development of pharmaceutical degrading microorganisms in MBR. [ABSTRACT FROM AUTHOR]

Aniline aerofloat (DDA) is a widely used material in China and has become a main pollutant in floatation wastewater. In this study, a membrane reactor (MBR) was constructed to continuously treat simulated wastewater contaminated with DDA. The study investigated the hydraulic retention time (HRT) and the impact of influent DDA concentration on MBR performance, and analyzed intermediates from the DDA biodegradation pathway and activated sludge transfer pathway. The results showed that a 3 h HRT was an efficient and economical time period for MBR to remove 95±5 mg/L DDA from the simulated wastewater; the chemical oxygen demand reduction rate was 89.9%. DDA concentration negatively impacted MBR performance. MBR performance fluctuated slightly when HRT was 3 h, dissolved oxygen ranged from 4.8 to 5.3 mg/L, pH was between 6.5 and 7.0, and DDA concentrations were at 95±5 mg/L DDA. The transfer pathway in the activated sludge of DDA was through soluble microbial products, loosely bound extracellular polymeric substances, tightly bound extracellular polymeric substances, and finally cell biodegradation. DDA initially degraded to aniline; the aniline was further biodegraded to other organic compounds and was finally mineralized through the tricarboxylic acid cycle. This study offers a new continuous biological treatment technology to address DDA. [ABSTRACT FROM AUTHOR]

In this study, we employed a bench scale A 2 O-MBR (anaerobic–anoxic–oxic membrane bioreactor) system to systematically investigate the behavior and distribution of silver nanoparticles (AgNPs) in the activated sludge. The results showed that AgNPs would aggregate and form Ag–sulfur complexes in the activated sludge, and the dissolved silver only reached 13.6 μg/L when AgNPs of 5 mg/L was spiked into the A 2 O-MBR. The long-term mass balance analysis showed that most of the silver contents were accumulated in the bioreactor and wasted excess sludge. Only a small fraction (less than 0.5%) of silver could get across the hollow fiber membranes with 0.1 μm nominal pore size in the effluent. In addition, the comparison between total AgNP concentration in aerobic sludge supernatant and effluent suggested that the membrane modules played a role in controlling the discharge of AgNPs into the effluent, especially under a higher influent concentration of AgNPs. Our results also showed that the adsorbed AgNPs or silver complexes in activated sludge still could release dissolved silver at the ambient pH. Thus, since activated sludge could be a sink for AgNPs, the risks of AgNPs in wasted excess sludge during utilization and disposal should be further studied. [ABSTRACT FROM AUTHOR]

In order to prevent hydrocarbon discharge at sea from ships, the International Maritime Organization (IMO) enacted the MARPOL 73/78 convention in which any oil and oil residue discharged in wastewater streams must contain less than 5 ppm hydrocarbons. Effective treatment of this petroleum-contaminated water is essential prior to its release into the environment, in order to prevent pollution problem for marine ecosystems as well as for human health. Therefore, two bench scale membrane bioreactors (MBRs) were investigated for hydrocarbon biodegradation. The two plants were initially fed with synthetic wastewater characterised by an increasing salinity, in order to enhance biomass acclimation to salinity. Subsequently, they were fed with a mixture of synthetic wastewater and real shipboard slops (with an increasing slops percentage up to 50% by volume). The results indicated a satisfactory biomass acclimation level in both plants with regards to salinity, providing significant removal efficiencies. The real slops exerted an inhibitory effect on the biomass, partially due to hydrocarbons as well as to other concomitant influences from other compounds contained in the real slops difficult to evaluate a priori . Nevertheless, a slight adaptation of the biomass to the new conditions was observed, with increasing removal efficiencies, despite the significant slops percentage. [ABSTRACT FROM AUTHOR]

Air sparging is extensively used to mitigate membrane fouling in membrane bioreactors (MBRs), which represents an important operation cost in submerged MBR. In this work, the effect of intermittent aeration mode on the membrane fouling has been studied by analysing the influence of the aeration cycle duration in a submerged MBR treating cosmetic wastewater. The long-term filtration at a permeate flux of 8.0 L m−2 h−1and a constant specific air demand (SAD) of 1.5 m3 m−2 h−1led to a significant increase in the transmembrane pressure (TMP) after 10 d. The tangential shear showed a limited effect on preventing the deposition of small particles, since carbohydrates and proteins present in the fouling layer were mainly smaller than 1 μm. Flocs showed a low stability under shear stress, which limits the increase in the SAD to avoid undesirable effects over the mixed liquor permeability. The intermittent aeration operation allowed the operation of the MBR under low aeration intensity (low SAD) without compromizing the fouling of the membranes. The use of aeration cycles shorter than 1 min led to an efficient control of fouling, which resulted in a negligible increase in the TMP after 2 h, operating at a permeate flux of 12.0 L m−2 h−1. [ABSTRACT FROM PUBLISHER]

Incorporation of moving beads into membrane bioreactor (MBR) has been suggested as an effective membrane fouling control because moving beads can mechanically remove bio-cakes on the membrane surface without additional equipment and energy input. As the efficiency of fouling control is dependent on factors associated with moving beads, however, the design of experiment was applied to find optimum condition for the effective mechanical cleaning with moving beads in MBR. Bead diameter (mm), bead number, and aeration rate (m3/h) were selected as independent design parameters. Based on batch test results, the correlation between the detachment efficiency of bio-cakes and three design parameters was established using Box–Behnken methodology. When all three design parameters at their optimal conditions (beadopt) were extended to the continuous lab-scale MBR, membrane filterability increased by three times, compared with that in the control MBR without bead. On the other hand, each of five experimental sets with two optimal and one random parameter (beadrandom) showed less membrane filterability by 9–80%, respectively, compared with beadopt. The parameterC(aeration rate) affected most significantly as it is associated with not only bead movement but also shear induced by air bubbles. [ABSTRACT FROM AUTHOR]

This paper proposes a structure of an integrated mathematical model of a membrane bioreactor (MBR) and describes the links between two main parts of a MBR model: the bioreactor and the membrane. In case of an immersed MBR three types of links are considered: a relationship between specific cake resistance (SCR) and extracellular polymeric substances (EPS) in the bioreactor, a relationship between air scour rate and shear stresses on the membrane surface, and a relationship between concentration of soluble microbial products (SMP) in the bioreactor and rate of pore constriction. While SMP concentration features directly in the equations of pore constriction, EPS are assumed to affect SCR which in turn has an effect on cake filtration. The relationship between EPS and SCR is described with a linear algebraic equation. Shear stresses on the membrane surface are calculated as a function of air scour rate with a one-dimensional slug flow model. [ABSTRACT FROM AUTHOR]