Performance Of Membrane Bioreactor Research Articles

Linking feed, biodiversity, and filtration performance in a Self-Forming Dynamic Membrane BioReactor (SFD MBR) treating canning wastewater

A bench-scale self-forming dynamic membrane bioreactor (SFD MBR) treating canning wastewater showed instable filtration performance, with a worsening in correspondence of a change in the influent quality. To unveil the possible reasons for such behaviour, a microbial investigation was carried out to complement conventional filterability and settleability tests. The microbial communities of the influent wastewater, the activated sludge, and the filtering sludge cake (dynamic membrane) were characterised through metagenomic and differential abundance analyses. In parallel, the production of exopolymers was measured. The outputs indicate that under the tested conditions the canning wastewater promoted the development of a very peculiar microbial ecosystem, with a strong selection of the genus Thiothrix (relative abundance above 90 %). The Shannon index values in activated sludge were below 2, indicating a very low bacterial diversity. This may have limited the ecosystem resilience towards changes of external conditions, causing instability in the process of the dynamic membrane formation. Furthermore, the diversity analysis showed that the bacterial compositions of the feed and the sludge resulted not significantly linked to each other, confirming the main role of the chemical composition of the influent wastewater on overall process performances. When treating agro-industrial streams, in-depth feed characterisation is recommended in order to prevent the factors that may generate instability in SFD MBR performance.

Enhanced Performance of Membrane Bioreactor in Sewage Treatment through Integrated Control Strategy

Enhanced Performance of Membrane Bioreactor in Sewage Treatment through Integrated Control Strategy

Impact of feeding regimes on the performance of anaerobic sequencing batch membrane bioreactor treating wastewater from an urban drain

ABSTRACT This work evaluated an anaerobic sequencing batch membrane bioreactor (AnSBR-MBR) equipped with waste-based ceramic membranes for treating low-strength real drain wastewater. Two feeding regimes, viz. settled feed (Phase 1) and mixed feed (Phase 2) were compared. The biological performance (chemical oxygen demand (COD) and phosphate (PO43-) removal) and filtration performance (total suspended solids (TSS) removal and membrane fouling) were investigated. The reactor characteristics in terms of solids content, sludge settling behaviour, and extracellular polymeric substances (EPS) were also assessed. In Phase 1, the settled feed (with the absence of particulate organic matter) resulted in low volatile suspended solids (VSS; 0.23 ± 0.15 g/L), causing low COD removal (28.38 ± 8.14%). In the mixed feed regime in Phase 2, VSS increased (1.82 ± 0.60 g/L) due to the organic content in the particulate matter, which gave microorganisms additional food, resulting in increased COD removal (47.42 ± 2.81%); this phase was also characterised by lower membrane fouling because of the lower EPS content. Marginally higher TSS removal was obtained as well in Phase 2 (96.72 ± 3.26%) than in Phase 1 (90.48 ± 8.14%). This work demonstrates that AnSBR-MBR performance is superior with mixed drain wastewater containing suspended solids and thus pre-settling is not recommended.

Filtration performance of biofilm membrane bioreactor: Fouling control by threshold flux operation

Membrane fouling is the major factor that restricts the furtherly widespread use of membrane bioreactor (MBR). As a new generation of MBR, biofilm membrane bioreactor (BF-MBR) demonstrates high treatment efficiency and low sludge growth rate, however the filtration performance improvement and membrane fouling control are still the challenges for its further development. This work investigated the filtration performance using resistance in series model and membrane fouling control via threshold flux for BF-MBR. At first, the flux behavior and filtration resistance under various operating conditions, including agitation speed, membrane and TMP, were explored by resistance in series model. Because of the desirable anti-fouling capacity, UP100 and UP030 had the high threshold flux (100 and 90 L m−2 h−1) and low irreversible fouling resistance (1 and 1.3 × 10−10 m-1). Higher shear stress produced by higher agitation speed could reduce membrane fouling, while greatly promote the threshold flux (138 L m−2 h−1) and membrane cleaning efficiency (96%). Moreover, increasing shear stress or selecting membrane with large pore size could decrease the fouling rate and raise the threshold flux. As for TMP, high TMP reduced the removal rate for organic and nutrient, and enhanced the irreversible fouling. Besides, the aerobic-BF-MBR (101 L m−2 h−1 and 1.3 × 10−10 m-1) with lower foulant concentration had a better filtration performance than anoxic-BF-MBR (90 L m−2 h−1 and 1.5 × 10−10 m-1). Additionally, the long-term tests with 10 cycles were conducted to evaluate the industrial application value of BF-MBR (45–58 L m−2 h−1). This work provides the technical support for sustainable filtration performance of BF-MBR.

Role of biochar addition to improve anaerobic membrane bioreactors to resist oil stress in synthetic food wastewater treatment

This study investigated biochar addition to improve the performance and stability of anaerobic membrane bioreactor (AnMBR) to resist different oil contents in food wastewater treatment. Results show that an increase in oil content in synthetic food wastewater from 2 to 4 g/L of oleate-Na aggravated AnMBR performance in terms of methane (CH4) production and membrane fouling as showed by an obvious increase in transmembrane pressure (TMP). The reduced performance was caused by the accumulation of volatile fatty acids (VFAs) to inhibit the growth and activity of Methanobacterium in response to increased oil content. Nevertheless, biochar addition improved AnMBR resistance to against oil increase. The dominance of Methanobacterium and their potential mutualism with genus T78 were enhanced by biochar to sustain CH4 yield. Moreover, biochar reduced the production of extracellular polymeric substance (EPS) to alleviate membrane fouling.

A comparative study on performance of the conventional and fixed-bed membrane bioreactors for treatment of Naproxen from pharmaceutical wastewater

Here, a comparative study was designed to survey the treatment efficiency of pharmaceutical wastewater containing Naproxen by Membrane bioreactor (MBR) and MBR with fixed-bed packing media (FBMBR). To this end, the performance of MBR and FBMBR in different aeration conditions including average DO (1.9–3.8 mg/L), different organic loading (OLR) (0.86, 1.14 and 1.92 kg COD per cubic meter per day), and Naproxen removal efficiency. The BOD5 removal efficiency, effluent quality and membrane fouling were monitored within 140 days. The results obtained from the present study indicated that COD removal efficiency for FBMBR (96.46%) was higher than that for MBR (95.33%). In addition, a high COD removal efficiency was experienced in both MBR and FBMBR in operational conditions 3 and 4, even where OLR increased from 1.14 to 1.92 kgCOD/m3 d and DO decreased from 4 to < 1 mg/L. Furthermore, the higher Naproxen removal efficiency was observed in FBMBR (94.17%) compared to that for MBR (92.76%). Therefore, FBMBR is a feasible and promising method for efficient treatment of pharmaceuptical wastewater with high concentrations of emerging contaminant, especially, the Naproxen.

Performance of a novel hybrid membrane bioreactor (HMBR) treating synthetic dairy wastewater: assessment of coupled mechanical removal sections and MBR

Performance of a novel hybrid membrane bioreactor (HMBR) treating synthetic dairy wastewater: assessment of coupled mechanical removal sections and MBR

Permeate flux recovery and removal foulant performances of hollow fiber polyvinylidene fluoride membrane bioreactor with peroxodisulfate activated iron (II) sulfate as a chemical cleaning agent

The main challenge with membrane bioreactors is fouling, which leads to decreased flux performance and a shortened membrane lifespan. This study aims to provide a solution for the flux recovery and removal of irreversible fouling on Polyvinylidene Fluoride (PVDF) membranes without damaging their structure using sulfate radicals. Sulfate radicals are formed via peroxodisulfate precursors that are activated by Fe2+. The membrane flux recovery and irreversible fouling ratio were 88.45-99.04% and 11.60-0.96%, respectively, at operating temperatures of 298-308 K. The PVDF membrane has been tested for microfiltration and washed up to 6 times per cycle. The mechanical properties, XRD, SEM-EDX, and ATR-FTIR characterization of the PVDF membrane after washing with PDS/Fe2+ did not show a negative effect on the PVDF structure. Additionally, the results of the kinetic and thermodynamic studies showed that washing with PDS/Fe2+ inhibited the formation of fouling particles on the membrane surface. Based on this study, sulfate radical oxidants with PDS precursors activated by Fe2+ can be applied as cleaning chemicals for PVDF membranes without damaging their structures.

How high salt shock affects performance and membrane fouling characteristics of a halophilic membrane bioreactor used for treating hypersaline wastewater

In the present study, the effect of short-term salt shocks (13% and 20%) on the performance of a halophilic MBR bioreactor used to treat a hypersaline (5% salt) synthetic wastewater was considered. 13% and 20% salt shocks resulted in a transient and permanent decrease in chemical oxygen demand removal efficiency, respectively which could be correlated with soluble microbial products (SMP) concentration and specific oxygen uptake rate values of the halophilic population. DNA leakage tests suggested that both 13% and 20% short-term salt shocks resulted in some cell structural damage. During both 13% and 20% salt shocks mixed liquor SMP, extracellular polymeric substances (EPS), zeta potential and endogenous respiration increased while relative hydrophobicity, EPSp/EPSc and exogenous respiration decreased; in both cases, however, the pre-shock values for these parameters were restored after the removal of the salt shock. 13% salt shock resulted in a transient increase in the membrane fouling rate and a permanent rise in total membrane resistance (Rt). On the other hand, both membrane fouling rate and Rt increased during 20% salt shock. Membrane fouling rate initially reduced after the 20% salt shock removal but after 5 days a “TMP jump” occurred. The latter was caused by the higher steady state SMPc and SMPp concentrations after removal of 20% salt shock compared to pre-shock values. This might have either resulted in a decrease in critical flux or an increase in local flux above critical flux in some parts of the membrane. The contribution of cake layer resistance to overall membrane resistance increased after the 13% and 20% salt shocks. The findings of the present study reveal the robustness of halophilic MBRs against salt shocks in the treatment of hypersaline wastewater. However, in cases of very high salt shocks, appropriate membrane fouling reduction strategies should be carried out during its operation.

Performance of Fe-dosing membrane bioreactor and evaluation of phosphorus recovery as vivianite after long-term operation

In this study, the influence of high concentration of iron on the nutrient removal, membrane fouling and microbial diversity of membrane bioreactor for wastewater treatment were systematically investigated. Moreover, the potential of phosphorus recovery in the form of vivianite was assessed after the long-term operation. The results show that TP concentration in effluent was decreased to 1.07 ± 0.47 mg/L (without Fe addition), 0.41 ± 0.23 mg/L (Fe/P = 2), 0.20 ± 0.12 mg/L (Fe/P = 4). Compared with control group, the TN concentration in effluent was higher at the high concentration of iron, which was due to the decreased nitrite-oxidizing bacteria (NOB) by microbial population analysis. Membrane fouling was alleviated by enlarging floc size and reducing supernatant COD via adding iron. Besides, it was detected that the amorphous ferric oxide and Fe(III) bound phosphorus were the main Fe and P speciation and vivanite (ca. 29 %). The anaerobic environment was conducive to the formation of vivianite and the phosphorus recovery as vivanite was recommended based on the results of current study.

Optimum quorum quenching bacteria concentration in the better-quality cell entrapping beads to control biofouling in membrane bioreactor

Quorum quenching (QQ) by cell entrapping beads (CEBs) is known to inhibit biofouling by its biological and physical cleaning effect. Although there are better QQ media reported, due to the ease of fabrication of QQ-CEBs, this study focused on improving the quality of CEBs by comparing two distinct bead-making methods – polyvinyl alcohol-alginate (PVA-alginate) and phase inversion – and on finding the optimum concentration of QQ bacteria in the CEBs. The evaluation of PVA-alginate bead showed better uniformity, and higher mechanical and chemical strength in comparison with the phase inversion bead. Through the operations of two control membrane bioreactors (MBRs) (no bead, vacant bead) and four QQ-MBRs with different Rhodococcus sp. BH4 concentrations (2.5–15 mg cell ml−1) in PVA-alginate CEBs, the maximum QQ effect was observed by 5 mg ml−1 BH4 concentration beads. This implies that an optimum cell concentration of QQ-CEBs is crucial to economically improve MBR performance using QQ.

Interrelation between extracellular polymer substances (EPSs) and MPs in an MBR

Nowadays, microplastics (MPs), as ubiquitous pollutants in aquatic ecosystems, present a major emerging threat. Wastewater treatment plants (WWTPs) are considered a hotspot of MP contamination. In this context, membrane bioreactors (MBRs), which combine conventional activated sludge processes with filtration, serve as an effective technology to remove MPs from wastewater. One of the main factors that affect MBR performance is the amount and composition of extracellular polymeric substances (EPSs) in the mixed liquor (ML). In previous studies carried out at lab-scale with model MPs, it has been found that the presence of MPs in wastewater treatment processes affect the EPS characteristics. In this work, the inter-relationship between EPSs and MPs has been investigated in a MBR at an industrial scale. Samples of the ML were taken from a WWTP during a six-month period and EPSs and MPs were analysed. It was observed that the higher the concentration of MPs, the higher the amount of EPSs were secreted by microorganisms, which seems to indicate that MPs act as an environmental stressor. Additionally, ML samples were centrifuged and the retention of MPs in the centrifuged solid (CS), which mainly depends on the size and morphology of MPs, was evaluated in relation to the amount and composition of EPSs. Remarkably, the concentration of humic acids showed a linear correlation with respect to the percentage of MPs retained in the CS. According to this, a possible mechanism based on hydrophobic interactions has been proposed as being responsible for the retention of MPs in sludge flocs.

Predicting Anaerobic Membrane Bioreactor Performance Using Flow-Cytometry-Derived High and Low Nucleic Acid Content Cells.

Having a tool to monitor the microbial abundances rapidly and to utilize the data to predict the reactor performance would facilitate the operation of an anaerobic membrane bioreactor (AnMBR). This study aims to achieve the aforementioned scenario by developing a linear regression model that incorporates a time-lagging mode. The model uses low nucleic acid (LNA) cell numbers and the ratio of high nucleic acid (HNA) to LNA cells as an input data set. First, the model was trained using data sets obtained from a 35 L pilot-scale AnMBR. The model was able to predict the chemical oxygen demand (COD) removal efficiency and methane production 3.5 days in advance. Subsequent validation of the model using flow cytometry (FCM)-derived data (at time t - 3.5 days) obtained from another biologically independent reactor did not exhibit any substantial difference between predicted and actual measurements of reactor performance at time t. Further cell sorting, 16S rRNA gene sequencing, and correlation analysis partly attributed this accurate prediction to HNA genera (e.g., Anaerovibrio and unclassified Bacteroidales) and LNA genera (e.g., Achromobacter, Ochrobactrum, and unclassified Anaerolineae). In summary, our findings suggest that HNA and LNA cell routine enumeration, along with the trained model, can derive a fast approach to predict the AnMBR performance.

Studying the Effect of HRT, SRT, and MLSS on Membrane Bioreactor Performance for Wastewater Treatment

Studying the Effect of HRT, SRT, and MLSS on Membrane Bioreactor Performance for Wastewater Treatment

A novel γ-Fe3O4-N-BC combined membrane bioreactor for wastewater treatment: Performance and mechanism

In this study, a new type of iron–nitrogen doped biochar (γ- Fe3O4-N-BC) was developed to improve nutrient removal efficiency and mitigate membrane fouling in combination with MBR. The characteristion of γ-Fe3O4-N-BC, N-BC, and BC revealed that the BET surface area (SBET) of γ-Fe3O4-N-BC, which was 1320.86 m2/g, was greater than that of N-BC (702.75 m2/g) and BC (1033.63 m2/g). The excellent SBET exhibited by γ-Fe3O4-N-BC compared to that of the other biochars is attributed to hydrogen bonding and electrostatic interactions. Compared to the addition of N-BC or BC or the absence of biochar, the addition of γ-Fe3O4-N-BC in the membrane bioreactor (MBR) resulted in superior wastewater treatment performance, for which the average removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total phosphorus (TP) were 94.65 %, 82.56 %, and 65.90 %, respectively. Moreover, after inoculation with γ-Fe3O4-N-BC, the TMP increase rate and time required to reach 42.37 kPa were 2.35 kPa/d and 18 d, respectively. The investigation of the effect of the γ-Fe3O4-N-BC concentration on MBR performance showed that the nutrient removal efficiency in the 500-MBR greater than that in the 350-MBR, 650-MBR, and 800-MBR, and that the membrane fouling was more ameliorative. A mechanistic investigation demonstrated that the 500-MBR had a beneficial influence on sludge biomass growth and helped to improve the nutrient removal capacity of the MBR. The 500-MBR improved the flocculability and stability of the sludge flocs in the MBR by increasing particle size and zeta potential. Changes in the extracellular polymeric substance (EPS) concentration and the smaller protein (PN) / polysaccharide (PS) ratio in 500-MBR also had significant impacts on alleviating the adhesion and accumulation of fouling layers on the improved membrane surface. Consequently, this study provides a new method for nutrient removal and membrane fouling mitigation in the MBR process.

Harnessing diurnal dynamics: Deciphering the interplay of light cycles on algal-bacterial membrane bioreactors

Light profoundly modulates the algal-bacterial membrane bioreactor (algal-bacterial MBR) performance. Yet, its outdoor deployment grapples with the inherent diurnal cycle of sunlight, engendering suboptimal light conditions. The adaptability of such systems to these fluctuating light conditions and their implications for practical outdoor applications remained an under-explored frontier. In response, this study meticulously scrutinized two laboratory-scale algal-bacterial MBRs under varying light regimes: a 24-h continuous and a 12-h cyclic illumination. Over 70 days, continuous illumination was observed to yield superior biomass production and total nitrogen and total phosphorus removal efficiencies compared to its cyclic counterpart. Contrarily, when focusing on membrane fouling, the 12-h cyclic illumination exhibited lower membrane fouling. The spectral analyses coupled with adhesion ability evaluation, traced the enhanced membrane fouling under continuous illumination to the elevated organics and heightened adhesive properties of the flocs. Given the tangible benefits of reduced membrane fouling and the potential harnessing of solar radiation, the 12-h cyclic illumination emerges as an economically astute operational paradigm for algal-bacterial MBRs. The significance of this study is to promote the application of algal-bacterial MBR in sewage treatment and provide robust support for the development of green technology in the future.

Evaluating the performance and membrane fouling of a submerged membrane bioreactor (MBR) treating plywood industry wastewater.

This study evaluates the performance of a membrane bioreactor (MBR) for treating wastewater from the laminated plywood industry. To this end, a pilot-scale MBR was operated for 60 days with a hydraulic retention time of 20 h and a solid retention time of 20 days. The reactor's performance was assessed based on the removal of chemical oxygen demand (COD), phenol, turbidity, and apparent color. Furthermore, we monitored the solids content, dissolved oxygen concentration, and pH of the mixed liquor, as well as the progression of the transmembrane pressure (TMP). The wastewater exhibited a COD/biochemical oxygen demand (BOD) ratio of 5.5, suggesting low biodegradability, usually when this ratio is higher than 4.0. Nevertheless, it was observed that the MBR's performance was stable and satisfactory, with average removal efficiencies of 98% for COD, 70% for phenol, 99% for turbidity, and 93% for true color. The evolution of TMP indicated gradual membrane fouling; however, the operational limit of 0.6 bar was not reached during the study period. In conclusion, the utilization of MBR presents a promising approach to mitigate the environmental impacts associated with wastewater from the laminated plywood industry.

Improved performance of single-stage partial nitritation-anammox membrane bioreactor (PN/A MBR) by adding biofilm carriers: start-up, membrane operation and microbial structure

Serious sludge washout is a bottleneck in the partial nitritation-anammox (PN/A) process that needs to be addressed urgently. A membrane bioreactor (MBR) is suitable for the PN/A process because of its 100 % biomass retention ability. Therefore, this study establishes a single-stage PN/A MBR and a PN/A moving bed membrane reactor (PN/A MB-MBR) for investigating the operation performance, membrane fouling behavior, and effect of biofilm carrier addition. The results demonstrate that the PN/A MB-MBR achieves a significantly shorter start-up time and substantially higher maximum nitrogen removal rate (NRR) of 17 days and 1.02 g N/L/d, respectively, compared to that of PN/A MBR (61 days and 0.19 g N/L/d, respectively). Further, the PN/A MB-MBR exhibits a lower membrane fouling of 0.023 kPa/L compared to that of 0.050 kPa/L in PN/A MBR because of the integration of the biofilm carrier. The biofilm in PN/A MB-MBR shows a higher relative abundance of Candidatus Kuenenia (18.90–25.10 %), which is a major AnAOB, compared to that observed in the suspended sludge of PN/A MB-MBR (10.30–14.32 %). Furthermore, the relative abundance of Candidatus Kuenenia absorbed on the membrane surface of PN/A MB-MBR (8.6 %) was lower than that on PN/A MBR (15.5 %). This study presented a promising method for enhancing the performance of PN/A MBR, which can serve as a valuable reference for its extensive implementation.

Evaluation of the Effect of Microalgae Chlorella vulgaris on the Performance of Membrane Bioreactor for Industrial Wastewater Treatment

Water pollution, especially from industry, is a problem that continues to emerge and even get worse. Rising sludge events often occur in industrial wastewater treatment processes. Process engineering with the addition of microalgae is proposed in this study to overcome the occurrence of rising sludge and improve wastewater quality based on dissolved oxygen levels. The control variables used were MLSS 1000 mg/L, microalgae Chlorella vulgaris 106 L, and urea and TSP 1,75 kg each. The dependent variable is rising sludge and DO levels while the independent variable is time. This research went through several stages, namely seeding microalgae, seeding microalgae into activated sludge in MBBR, experimenting with combining microalgae and activated sludge in MBBR, and installing ultrafiltration membranes with a WWTP capacity of 150 m3/day. The addition of microalgae in the MBBR process has a positive impact in improving the quality of industrial wastewater, which is characterized by the absence of rising sludge and DO levels exceeding the minimum threshold.

Effects of MgCl2 on sludge anaerobic digestion: Hydrolysis, acidogenesis, methanogenesis, and microbial characteristics

Back diffused draw salt affects the anaerobic digestion performance in a forward osmosis membrane bioreactor. Previous studies have established the influence of MgCl2 on sludge anaerobic digestion; however, its effects on individual phases, such as hydrolysis, acidogenesis, and methanogenesis remain unclear. This study investigates the influence of different concentrations of MgCl2 on these stages of anaerobic digestion and compares variations in methane production under different substrates. The findings demonstrate that adding MgCl2 significantly enhances sludge hydrolysis. At a concentration of 50 g/L, the soluble chemical oxygen demand increases by 265.2 %, although with unstable reactions. MgCl2 significantly affects the production of fatty acids. Specifically, the production of acids was enhanced when the concentration of MgCl2 was below 20 g/L, while it was inhibited when the concentration exceeded 50 g/L. The highest concentration of acetic acid recorded is 1991.28 mg/L, which represents an 83.5 % increment. In contrast, methane production shows a higher susceptibility to MgCl2, experiencing inhibition at concentrations exceeding 1 g/L. The inhibitory concentration for methane production is lower than for acid production. The study also observes significant differences in microbial structure, particularly in Methanogen. When using different substrates, the predominant orders of methanogen are Methanobacteriales for tests with acid solution as a feed and Methanosarcinales for tests with waste sludge as a feed, respectively. Analyses of metabolic pathways reveal that carbon dioxide and acetic acid are the most prevalent pathways in terms of abundance. In summary, MgCl2 has varying effects on various stages of anaerobic digestion of sludge.