Fouling In Membrane Bioreactors Research Articles

Evaluation of soluble microbial products (SMP) on membrane fouling in membrane bioreactors (MBRs) at the fractional and overall level: a review

Membrane fouling by soluble microbial products (SMP) remains one of the limitations for widespread applications of membrane bioreactor (MBR) systems. Over the past two decades, the characteristics and behaviors of SMP have attracted much attention, and efforts have been dedicated to clarify their role in membrane fouling in MBRs. However, to date, there are only few reviews directly relating this area, and the objective of previous reviews is to concentrate on SMP and their implications in biological treatment systems and their effluents. This brief review relating only to SMP-caused membrane fouling evaluation at the fractional level (SMP key components, sub-fractions and hydrophilic and hydrophobic fractions) and at the overall level (SMP overall roles, characteristics and factors) is presented, which could greatly help researchers and engineers to better understand SMP actual contribution to membrane fouling and adopt effective measures to avoid SMP-caused fouling in MBRs.

Prediction of membrane fouling using artificial neural networks for wastewater treated by membrane bioreactor technologies: bottlenecks and possibilities.

Membrane fouling is a major concern for the optimization of membrane bioreactor (MBR) technologies. Numerous studies have been led in the field of membrane fouling control in order to assess with precision the fouling mechanisms which affect membrane resistance to filtration, such as the wastewater characteristics, the mixed liquor constituents, or the operational conditions, for example. Worldwide applications of MBRs in wastewater treatment plants treating all kinds of influents require new methods to predict membrane fouling and thus optimize operating MBRs. That is why new models capable of simulating membrane fouling phenomenon were progressively developed, using mainly a mathematical or numerical approach. Faced with the limits of such models, artificial neural networks (ANNs) were progressively considered to predict membrane fouling in MBRs and showed great potential. This review summarizes fouling control methods used in MBRs and models built in order to predict membrane fouling. A critical study of the application of ANNs in the prediction of membrane fouling in MBRs was carried out with the aim of presenting the bottlenecks associated with this method and the possibilities for further investigation on the subject.

Sızıntı Suyu Arıtımı Yapan Membran Biyoreaktörlerde Membran Kirlenmesine Etki Eden Faktörler ve Tıkanma Kontrolü

Kati atiklarin arazide depolanmasi yuksek kirlilikte sizinti suyu olusumuna neden oldugu icin yuzeysel ve yeralti su kaynaklari icin onemli bir tehdit olusturmaktadir. Diger biyolojik aritma yontemleriyle karsilastirildiginda, membran biyoreaktorler (MBR) ile yuksek kalitede aritilmis su elde edilebildiginden, MBR’lerin sizinti suyu aritiminda son yillarda daha cok tercih edildigi gorulmektedir. Bu calismanin amaci sizinti suyu aritimi yapan MBR’lerde tikanma nedenlerinin ortaya konulmasi ve tikanmayi azaltmak icin en uygun metodun belirlenmesidir. Sizinti suyu aritimi yapan tam olcekli iki MBR tesisi (MBR-1 ve MBR-2) kiyaslandiginda; karbonhidrat bazli cozunmus mikrobiyal urunler (CMUk) degeri MBR-2 tesisinde MBR-1’e gore yaklasik 5 kat daha fazladir. Her iki tesis icin hucre disi polimerik maddeler (HPM) miktarinda CMU miktari kadar fark olmamakla birlikte, MBR-2’de MBR-1’e gore HPM miktari daha yuksektir. Bu durum MBR-2’de gorulen tikanma problemlerinde, CMU’nun baslica rol oynadigini gostermektedir. Tikanma kontrolu ile ilgili deneysel sonuclar dikkate alindiginda, membran tikanmasini azaltacak en uygun yontemin 50 mg/L konsantrasyonda toz aktif karbon (TAK) eklenmesi oldugu belirlenmistir.

Membrane fouling in a submerged membrane bioreactor: An unified approach to construct topography and to evaluate interaction energy between two randomly rough surfaces

Quantitatively evaluating interaction energy between two randomly rough surfaces is the prerequisite to quantitatively understand and control membrane fouling in membrane bioreactors (MBRs). In this study, a new unified approach to construct rough topographies and to quantify interaction energy between a randomly rough particle and a randomly rough membrane was proposed. It was found that, natural rough topographies of both foulants and membrane could be well constructed by a modified two-variable Weierstrass-Mandelbrot (WM) function included in fractal theory. Spatial differential relationships between two constructed surfaces were accordingly established. Thereafter, a new approach combining these relationships, surface element integration (SEI) approach and composite Simpson’s rule was deduced to calculate the interaction energy between two randomly rough surfaces in a submerged MBR. The obtained results indicate the profound effects of surface morphology on interaction energy and membrane fouling. This study provided a basic approach to investigate membrane fouling and interface behaviors.

Impact of sludge retention time on MBR fouling: role of extracellular polymeric substances determined through membrane autopsy

The impact of sludge retention time (SRT) on the biofouling of a membrane bioreactor (MBR) by extracellular polymeric substances (EPS) was investigated. The MBR was operated at 60 and 20 d SRT. The gel layer (recovered through optimized membrane autopsy methods) and the cake layer were analyzed for their content and profile of EPS proteins and polysaccharides. The change to a shorter SRT led to decreased membrane filterability, concomitant with a higher expression of EPS proteins in the cake layer, which were identified as being mainly related with biosynthesis and stress functions. The gel layer was more substantial in internal fibers, with polysaccharides being the major component in this layer. With the decrease in SRT (and filterability decrease), the overall polysaccharide content and sugar variety increased. In conclusion, SRT impacted not only on the quantity but also the composition of EPS molecules, and both were shown to be important in biofouling.

Physicochemical correlations between membrane surface hydrophilicity and adhesive fouling in membrane bioreactors

36 membrane material cases used in membrane bioreactors (MBRs) covering wide range of hydrophilicity/hydrophobicity were used to calculate thermodynamic interactions between membranes and foulants. It was found that adhesive fouling can be represented by the total interaction energy at minimum separation distance (h0). No functional relationship between membrane hydrophilicity and adhesive fouling can be deduced. However, membrane hydrophilicity, in terms of water contact angle or interaction energy between two identical surfaces at h0 in water (ΔGsws), had high statistical correlations with adhesive fouling. This statistical correlations should be attributed to the major role of acid-base interaction in total interaction associated with adhesion in most of membrane cases. Moreover, the statistical correlations were independent of the changes in membrane surface roughness or hydrophilicity/hydrophobicity of foulants. These findings satisfactorily explained the inconsistent conclusions in the literature regarding effects of membrane hydrophilicity on adhesive fouling, giving implications for membrane fouling mitigation.

Recycling of Reverse Osmosis Concentrates to the Membrane Bioreactor in the MBR-RO Process for Water Reuse: effect on mbr performances

Wastewater effluents can be treated by an integrated membrane system combining membrane bioreactor (MBR) and reverse osmosis (RO) for effective removal of micropollutants in the field of high-quality water reuse. However, discharging the RO concentrate waste stream directly into the natural environment could lead to serious problems due to the toxic components contained in the concentrates (micropollutants, salts, organic matter). A possible solution could be the recirculation of RO concentrate waste to the MBR. However, such an operation should be studied in detail since the recirculation of non-biodegradable organic matter or high concentrations of salts and micropollutants could directly or indirectly contribute to MBR membrane fouling and modification of the biodegradation activity. In this context, the work reported here focused on the recirculation of such concentrates in an MBR, paying specific attention to MBR membrane fouling. Lab-scale experiments were performed on a continuous MBR-RO treatment line with RO concentrate recirculation. The main goal was to determine the recovery of the RO unit and of the global process that maintained good process performance in terms of biodegradation and MBR fouling. The results demonstrate that the impact of the toxic flow on activated sludge depends on the recovery of the RO step but the same trends were observed regardless of the organic matter and salt contents of the concentrates: the concentration of proteins increased slightly. Size-exclusion high performance liquid chromatography (HPLC-SEC) was employed to study the effects of RO concentrate on the production of protein-like soluble microbial products (SMPs) and demonstrated a significant peak of protein-like substances corresponding to 10-100 kDa and 100-1 000 kDa molecules in the supernatant. Thus a significant increase in the propensity for sludge fouling was observed, which could be attributed to the increased quantity of protein-like substances. Finally, the effect of the concentrate on sludge activity was studied and no significant effect was observed on biodegradation, indicating that the return of the concentrate to the MBR could be a good alternative.

Effects of hydraulic retention time on adsorption behaviours of EPS in an A/O-MBR: biofouling study with QCM-D

Extra-cellular polymeric substances (EPS) are a major cause of membrane fouling in membrane bioreactors (MBRs). In this study, an anoxic–oxic membrane bioreactor (A/O-MBR) was run continuously for 98 days. The runs were divided into three stages according to hydraulic retention time (HRT) (11.8, 12.5 and 14.3 h, respectively). EPS were extracted from the reactor under the different HRTs. A quartz crystal microbalance with dissipation monitoring (QCM-D) and Fourier transform infrared (FT–IR) were used to study the adherence layer structures and the adsorption behaviours of EPS on the membrane surface. The results indicated that the removal rate of TN was more susceptible to HRT than NH3-N. The observations in the QCM-D suggested that at the lowest HRT (11.8 h), the structure of the adsorption layer is loose and soft and the fluidity was better than for HRTs of 12.5 or 14.3 h. It is likely one of the major reasons for the rapidly blocking of the membrane pores. Furthermore, the higher EPS adherence as analyzed in the QCM-D and EPS concentration could induce a higher osmotic pressure effect, leading to a rapid membrane-fouling rate.

Impact of feed carbohydrates and nitrogen source on the production of soluble microbial products (SMPs) in anaerobic digestion

Six stirred fill-and-draw batch reactors with a range of carbohydrate feeds (glucose, fructose and sucrose), and nitrogen sources (NH4Cl, urea) at various concentrations were used to investigate the effect of feed composition on the production of soluble microbial products (SMPs) during anaerobic digestion (AD). To gain greater insights into the SMPs produced, the composition of various fractions was analyzed, while the low molecular weight (MW) SMPs generated with different feeds and nutrients were collected and chemically analyzed using GC-MS. Other organic solutes such as free amino acids were determined using HPLC, and this level of chemical analysis has never been carried out in past work because of analytical limitations. It was found that the presence of ammonium salts rather than urea at 200 mg/L stimulated the production of not only volatile fatty acids, but also SMPs of different MW fractions, and reduced the production of biogas significantly. The study also revealed that the type of SMP that dominates in a particular system depends on the chemical characteristics of the feed, and this insight has implications on the composition of the effluent from anaerobic digesters (and their potential chlorination by-products), and membrane fouling in membrane bioreactors.

Robust biochar-assisted alleviation of membrane fouling in MBRs by indirect mechanism

Abstract Biochar is a low-cost by-product of biomass pyrolysis to obtain renewable energy, and is composed of carbon skeleton, oxygen-containing functional groups, and minerals. Herein a new environmental application of biochar is detailed, namely, alleviating membrane fouling in a membrane bioreactor (MBR) process by dosing the bioreactor with quantities of various modified biochars (alkali washed (AW-BC), hydrophobic (HB-BC), hydrophilic (HL-BC), and activated biochars (AC-BC)). Results of trans-membrane pressure (TMP) tests showed that with the exception of HB-BC, all the other modified biochars exhibited robust antifouling capability and the TMP was decreased by as much as 36.8% and 31.4% at 24 h and 10 d respectively for AW-BC (most easily prepared) compared to a control. This was comparable to the results obtained in the use of expensive activated carbon (AC). Instead of dealing with the large surface area and scouring effects of AC, it was found that the indirect effects of biochar on sludge may be the basis for the antifouling mechanism, where the hydrophilicity of the biochar improved the settling of sludge. In addition, it was speculated that the abundant functional groups of the biochar increased the adsorption of Extracellular polymeric substance (EPS) based on the characterizations of N 2 -adsorption-desorption, fourier transform infrared spectroscopy (FTIR), X–ray photoelectron spectroscopy (XPS), Raman, scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM). Compared to traditional antifouling materials, the results of this study may offer a low-cost alternate for alleviating membrane fouling in MBRs.

A New Approach to Modeling Operational Conditions for Mitigating Fouling in Membrane Bioreactor.

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 (P1, P2) and carbohydrate (C1, 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 (P1, C1) 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.

Biofouling control based on bacterial quorum quenching with a new application: Rotary microbial carrier frame

Bacterial quorum quenching (QQ) is a new approach for controlling of membrane fouling in membrane bioreactors (MBRs). In this study, a novel bacterial immobilization medium named rotary microbial carrier frame (RMCF) was applied to inhibit biofilm formation in an MBR. RMCF was prepared by entrapping QQ bacteria (Rhodococcus sp. BH4) onto polycarbonate frame covered with microfiltration membrane. RMCF was submerged into the MBR using a rotational axle and rotated independently of the filtration module. QQ effect was examined with short- and long-term MBR operations. In MBRs operated with RMCF, transmembrane pressure (TMP) increasing rate was decreased with 65% efficiency. The prevention of biofouling resulted from both physical (shear forces) and biological (quorum quenching) effects of RMCF, and it was seen that RMCF could sustain its QQ effect over long-term operations. Biofilm formation inhibition by RMCF was confirmed visually using Confocal Laser Scanning Microscopy (CLSM). In addition, microbial population dynamics in MBRs were examined and it was found that RMCF had an effect on microbial diversity. The novelty of RMCF is to immobilize QQ bacteria into a rotating apparatus. With the application of RMCF, the anti-biofouling effect in an MBR had been investigated.

Novel indicators for thermodynamic prediction of interfacial interactions related with adhesive fouling in a membrane bioreactor

This study focused on developing indicators to predict adhesive membrane fouling in a membrane bioreactor (MBR). Thermodynamic interactions between membrane surface and foulants in various interaction scenes were comprehensively evaluated. It was revealed that, the total interaction energy in contact could be considered as a critical value affecting adhesion of foulants. Surface hydrophilicity cannot be simply represented by water contact angle. Statistical analysis showed that membrane acid-based (AB) surface tension, Lifshitz-Van der waals (LW) surface tension, total tension, zeta potential and water contact angle had no apparent correlation with adhesive fouling, suggesting the infeasibility of these parameters as fouling predictors. It was found that, interaction between two identical membrane surface in water (ΔGsws) and membrane surface electron donor tension (γ−) strongly correlated with adhesive fouling, and could be reliable indicators to predict adhesive fouling. This study identified the relationships of series membrane surface properties with adhesive fouling in MBRs.

Modeling three-dimensional surface morphology of biocake layer in a membrane bioreactor based on fractal geometry

While the adsorptive fouling in membrane bioreactors (MBRs) is highly dependent of the surface morphology, little progress has been made on modeling biocake layer surface morphology. In this study, a novel method, which combined static light scattering method for fractal dimension (Df) measurement with fractal method represented by the modified two-variable Weierstrass-Mandelbrot function, was proposed to model biocake layer surface in a MBR. Characterization by atomic force microscopy showed that the biocake surface was stochastic, disorder, self-similarity, and with non-integer dimension, illustrating obvious fractal features. Fractal dimension (Df) of sludge suspension experienced a significant change with operation of the MBR. The constructed biocake layer surface by the proposed method was quite close to the real surface, showing the feasibility of the proposed method. It was found that Df was the critical factor affecting surface morphology, while other factors exerted moderate or minor effects on the roughness of biocake layer.

Integrated approach to characterize fouling on a flat sheet membrane gravity driven submerged membrane bioreactor

Fouling in membrane bioreactors (MBR) is acknowledged to be complex and unclear. An integrated characterization methodology was employed in this study to understand the fouling on a gravity-driven submerged MBR (GD-SMBR). It involved the use of different analytical tools, including optical coherence tomography (OCT), liquid chromatography with organic carbon detection (LC-OCD), total organic carbon (TOC), flow cytometer (FCM), adenosine triphosphate analysis (ATP) and scanning electron microscopy (SEM). The three-dimensional (3D) biomass morphology was acquired in a real-time through non-destructive and in situ OCT scanning of 75% of the total membrane surface directly in the tank. Results showed that the biomass layer was homogeneously distributed on the membrane surface. The amount of biomass was selectively linked with final destructive autopsy techniques. The LC-OCD analysis indicated the abundance of low molecular weight (LMW) organics in the fouling composition. Three different SEM techniques were applied to investigate the detailed fouling morphology on the membrane.

Comparison of ferric chloride and aluminum sulfate on phosphorus removal and membrane fouling in MBR treating BAF effluent of municipal wastewater

A membrane bioreactor (MBR) was used for treating biological aerated filter effluent in a municipal wastewater plant, and chemical phosphorus removal was accomplished in the MBR. The results showed that ferric chloride of 20 mg/L and aluminum sulfate of 30 mg/L were the optimal dosages for total phosphorus (TP) removal, and the TP removal efficiency was over 80%. In long-term continuous operations, both ferric chloride and aluminum sulfate effectively mitigated membrane fouling, with the corresponding growth rate of transmembrane pressure decreased to 0.08 and 0.067 kPa/d, respectively. Sludge particle sizes analysis demonstrated that the decrease of particle sizes lower than 50 μm was the main reason for membrane fouling control. Simultaneously, the proteins and polysaccharide (PS) concentrations in the MBR supernatant were analyzed, and the PS concentration significantly decreased to 2.02 mg/L at aluminum sulfate of 30 mg/L, indicating the flocculation of aluminum sulfate on PS was the main reason for mitigation of membrane fouling.

Assessment of genomic rearrangements in Chinese Hamster Ovary (CHO) cells

Evolution of irreversible fouling in pilot-scale membrane bioreactors (MBRs) treating municipal wastewater was studied. Three membrane modules were sacrificed to analyze foulants after they had been used for different durations (1 day, 8 days, 24 days). The module used for 1 day reflected fouling occurring at the initial stage, whereas the module used for 24 days reflected the later stage of fouling. After each module had been used for the predetermined period, it was disassembled and subjected to powerful chemical analysis such as Fourier transform infrared (FTIR) analysis. It was clearly shown that components involved in evolution of irreversible fouling gradually changed depending on the duration. The initial fouling (conditioning of membrane) was caused by humics, whereas later fouling was mainly caused by polysaccharides. A model for evolution of irreversible fouling in MBRs and implications for fouling control are discussed.

A novel In-situ Enzymatic Cleaning Method for Reducing Membrane Fouling in Membrane Bioreactors (MBRs)

A novel in-situ enzymatic cleaning method was developed for fouling control in membrane bioreactors (MBRs). It is achieved by bringing the required enzymes near the membrane surface by pulling the enzymes to a magnetic membrane (MM) surface by means of magnetic forces, exactly where the cleaning is required. To achieve this, the enzyme was coupled to a magnetic nanoparticle (MNP) and the membrane it self was loaded with MNP. The magnetic activity was turned by means of an external permanent magnet. The effectiveness of concept was tested in a submerged membrane filtration using the model enzyme-substrate of Bacillus subitilis xylanase-arabinoxylan. The MM had almost similar properties compared to the unloaded ones, except for its well distributed MNPs. The enzyme was stable during coupling conditions and the presence of coupling could be detected using a high-performance anion-exchange chromatography (HPAEC) analysis and Fourier transform infrared spectroscopy (FTIR). The system facilitated an in-situ enzymatic cleaning and could be effectively applied for control fouling in membrane bioreactors (MBRs).

Effect of solid retention time on membrane fouling in membrane bioreactor: from the perspective of quorum sensing and quorum quenching.

Solid retention time (SRT) is one of the most important operational parameters in membrane bioreactor (MBR), which significantly influences membrane fouling. It is widely recognized that SRT mainly changes biomass characteristics, and then, influences membrane fouling. Effect of SRT on quorum sensing (QS) in MBR, which could also influence fouling by coordinating biofilm formation, has not been reported. In this study, fouling, QS, soluble microbial products (SMP), and extracellular polymer substances (EPS) in MBRs operated under SRTs of 4, 10, and 40days were investigated. The results showed that as SRT increased, the abundance of quorum quenching (QQ) bacteria increased, the quorum signal degradation activity of activated sludge increased, the concentrations of signal molecules in MBR decreased, the excretion of SMP and EPS decreased, and thus membrane biofouling was alleviated. Therefore, besides altering the biomass physiochemical properties, SRT also changed the balance between QS and QQ in MBR, and in this way, influenced membrane biofouling.

FRONT MATTER

<p><strong>PREFACE</strong></p><p>Indonesian Journal of Science and Technology (IJoST) is a peer-reviewed journal that aims to publish and disseminate innovative research articles on the latest developments in all fields of science and technology. The journal publishes original papers in English, which contribute to the understanding of science and improvement of the science and technology. Papers may be theoretical explanation (including computational), experimental observation and analysis, or combination from both theoretical and experimental analysis. The contribution should be unpublished before and not under consideration for publication in elsewhere. IJoST maintains a standard double-blind peer review process. The review process means that the identity with the author, and the reviewer are not known to each other. IJoST is an open-access journal, and in this issue IJoST does not charge for readers, authors, or their institutions for access to the journal articles. This journal was firstly be published on April 30, 2016, and issued every April and October in each year, published by Tim Pengembang Jurnal at Universitas Pendidikan Indonesia.</p><p>In this issue, we published eight papers, including six original research articles and two review papers. In this issue, we received papers from remarkable researchers in several countries in the world, including Belgium, Japan, Singapore, Malaysia, The Netherlands, and Indonesia. The first paper discussed enzymatic cleaning method for reducing membrane fouling in membrane bioreactor. The next paper presented about application of artificial neural network for predicting biodiesel production. In the third paper, authors discussed about comparison of air temperature under global climate change in Japan. In the fourth paper, authors discussed about kinetics and thermodynamic studies the adsorption of phenol on activated carbon. The fifth article presented sludge dewatering process control using principal component analysis and partial least square. The next paper discussed the use of process simulation for plant debottlenecking. The sixth paper is a review article regarding the use of agricultural waste for silica source material. The final paper is a review of high-temperature oxidation of steel in steam condition. We believe that this issue will give benefits for the improvement and the development of science and technology.</p><p> </p><p align="right">Bandung, April 2006</p><p align="right"> </p><p align="right">Editor</p><p align="right"> </p><p> </p>