Ceramic Membrane Bioreactor Research Articles

High Loaded Synthetic Hazardous Wastewater Treatment Using Lab-Scale Submerged Ceramic Membrane Bioreactor

Submerged ceramic membrane bioreactors (SCMBRs) are more efficient combinations of traditional activated hazardous sludge and new membrane separation processes in wastewater treatment. Suspended solids are separated from hazardous effluent using microfilter ceramic membranes in SCMBRs. A high loaded wastewater was treated using an SCMBR employing a homemade tubular ceramic membrane in laboratory scale. Hydraulic Retention Time (HRT) was 32 h and COD range was varied from 2000 to 5000 mg/l. COD removal was evaluated to be more than 90% after a week and the lab scale SCMBR showed desired performance for the wastewater treatment. Mixed Liquor Suspended Solid (MLSS) was increased from 2000 to 4000 mg/L during the SCMBR operation time.

Rapid establishment of phenol- and quinoline-degrading consortia driven by the scoured cake layer in an anaerobic baffled ceramic membrane bioreactor.

Although toxic and refractory organics, such as phenol and quinoline, are decomposed by anaerobic bacteria, the establishment of specific degrading consortia is a relatively slow process. An anaerobic membrane bioreactor allows for complete biomass retention that can aid the establishment of phenol- and quinoline-degrading consortia. In this study, the anaerobic digestion of phenol (500mgL-1) and quinoline (50mgL-1) was investigated using an anaerobic baffled ceramic membrane bioreactor (ABCMBR). The results showed that, within 30days, 99% of phenol, 98% of quinoline and 88% of chemical oxygen demand (COD) were removed. The substrate utilisation rates of the cake layer for phenol and quinoline, and specific methanogenic activity of the cake layer, were 7.58mgphenolg-1mixed liquor volatile suspended solids (MLVSS)day-1, 8.23mgquinolineg-1MLVSSday-1 and 0.55gCODCH4g-1MLVSSday-1, respectively. The contribution of the cake layer to the removals of phenol and quinoline was extremely underestimated because the uncounted scoured cake layer was disregarded. Syntrophus was the key population for phenol and quinoline degradation, and it was more abundant in the cake layer than in the bulk sludge. The highly active scattered cake layer sped up the establishment of phenol- and quinoline-degrading consortia in the ABCMBR.

Effects of bamboo charcoal on fouling and microbial diversity in a flat-sheet ceramic membrane bioreactor

Membrane fouling is a problem in full-scale membrane bioreactors. In this study, bamboo charcoal (BC) was evaluated for its efficacy in alleviating membrane fouling in flat-sheet membrane bioreactors treating municipal wastewater. The results showed that BC addition markedly improved treatment performance based on COD, NH4+-N, total nitrogen, and total phosphorus levels. Adding BC slowed the increase in the trans-membrane pressure rate and resulted in lower levels of soluble microbial products and extracellular polymeric substances detected in the flat-sheet membrane bioreactor. BC has a porous structure, and a large quantity of biomass was detected using scanning electron microscopy. The microbial community analysis results indicated that BC increased the microbial diversity and Aminomonas, Anaerofustis, uncultured Anaerolineaceae, Anaerolinea, and Anaerotruncus were found in higher abundances in the reactor with BC. BC addition is an effective method for reducing membrane fouling, and can be applied to full-scale flat-sheet membrane bioreactors to improve their function.

Evaluating the feasibility of pyrophyllite-based ceramic membranes for treating domestic wastewater in anaerobic ceramic membrane bioreactors

This study laid great emphasis on anaerobic ceramic membrane bioreactor (AnCMBR) treatment of domestic wastewater for facile and enhanced energy recovery. To this end, the performance of the natural-based ceramic (i.e., pyrophyllite-based) membranes was mainly explored in this study by evaluating filtration and treatment performances. 92.9±5.5% chemical oxygen demand (COD) removal and stable methane production were successfully achieved in a bench-scale AnCMBR while maintaining a slightly long hydraulic retention time (HRT). Comparative filtration experiments with commercialized ceramic membranes suggested that the pyrophyllite-based membrane separation in AnCMBR treatment of wastewater at long HRT is feasible. However, short HRT operations resulted in substantial levels of sludge washout. Future improvements of AnCMBR technology in cost-effective ceramic membrane development, increased flux, and harsh environmental conditions would make AnCMBR competitive with anaerobic membrane bioreactor (AnMBR) technology.

Treatment of food waste recycling wastewater using anaerobic ceramic membrane bioreactor for biogas production in mainstream treatment process of domestic wastewater

A bench-scale anaerobic membrane bioreactor (AnMBR) equipped with submerged flat-sheet ceramic membranes was operated at mesophilic conditions (30–35 °C) treating domestic wastewater (DWW) supplemented with food wasterecycling wastewater (FRW) to increase the organic loading rate (OLR) for better biogas production. Coupling ceramic membrane filtration with AnMBR treatment provides an alternative strategy for high organic wastewater treatment at short hydraulic retention times (HRTs) with the potential benefits of membrane fouling because they have a high hydrophilicity and more robust at extreme conditions. The anaerobic ceramic MBR (AnCMBR) treating mixture of actual FRW with DWW (with an influent chemical oxygen demand (COD) of 2,115 mg/L) was studied to evaluate the treatment performance in terms of organic matter removal and methane production. COD removal during actual FRW with DWW operation averaged 98.3 ± 1.0% corresponding to an average methane production of 0.21 ± 0.1 L CH4/g CODremoved. Biogas sparging, relaxation and permeate back-flushing were concurrently employed to manage membrane fouling. A flux greater than 9.2 L m−2 h−1 (LMH) was maintained at 13 h HRT for approximately 200 days without chemical cleaning at an OLR of 2.95 kg COD m−3 d−1. On day 100, polyvinyl alcohol (PVA)-gel beads were added into the AnCMBR to alleviate the membrane fouling, suggesting that their mechanical scouring effect contributed positively in reducing the fouling index (FI). Although these bio-carriers might accelerate the breaking up of bio-flocs, which released a higher amount of soluble microbial products (SMP), a 95.4% SMP rejection was achieved. Although the retention efficiency of dissolved organic carbons (DOC) was 91.4% across the ceramic membrane, a meaningful interpretation of organic carbon detection (OCD) fingerprints was conducted to better understand the ceramic membrane performance.

Use of a ceramic membrane bioreactor (CMBR) to treat wastewater at Guilin University of Technology

A ceramic membrane bio-reactor (CMBR) process was first used to treat wastewater collected from a campus of Guilin University of Technology (GUT). A CMBR with a submerged flat-sheet ceramic membrane module was designed for a Qmax of 300 m3/d. With a stable flux at about 33 L/m2 h, the transmembrane pressure was maintained at −10 kPa until the end of the experiment. The results showed that the CMBR process is a robust system capable of producing high-quality service water from campus wastewater. By using the CMBR process, the treated water met the Chinese national standards for landscaping irrigation.

Low energy single-staged anaerobic fluidized bed ceramic membrane bioreactor (AFCMBR) for wastewater treatment

An aluminum dioxide (Al2O3) ceramic membrane was used in a single-stage anaerobic fluidized bed ceramic membrane bioreactor (AFCMBR) for low-strength wastewater treatment. The AFCMBR was operated continuously for 395days at 25°C using a synthetic wastewater having a chemical oxygen demand (COD) averaging 260mg/L. A membrane net flux as high as 14.5–17L/m2h was achieved with only periodic maintenance cleaning, obtained by adding 25mg/L of sodium hypochlorite solution. No adverse effect of the maintenance cleaning on organic removal was observed. An average SCOD in the membrane permeate of 23mg/L was achieved with a 1h hydraulic retention time (HRT). Biosolids production averaged 0.014±0.007gVSS/gCOD removed. The estimated electrical energy required to operate the AFCMBR system was 0.039kWh/m3, which is only about 17% of the electrical energy that could be generated with the methane produced.

Alkali-assisted membrane cleaning for fouling control of anaerobic ceramic membrane bioreactor

In this study, a chemically enhanced backflush (CEB) cleaning method using NaOH solution was proposed for fouling mitigation in anaerobic membrane bioreactors (AnMBRs). Ex-situ cleaning tests revealed that NaOH dosages ranging from 0.05 to 1.30mmol/L had positive impacts on anaerobic biomass, while higher dosages (>1.30mmol/L) showed inhibition and/or toxic impacts. In-situ cleaning tests showed that anaerobic biomass could tolerate much higher NaOH concentrations due to the alkali consumption by anaerobic process and/or the buffering role of mixed liquor. More importantly, 10–20mmol-NaOH/L could significantly reduce membrane fouling rates (4–5.5 times over the AnMBR with deionized water backflush) and slightly improve methanogenic activities. COD removal efficiencies were over 87% and peaked at 20mmol-NaOH/L. However, extremely high NaOH concentration had adverse effects on filtration and treatment performance. Economic analysis indicated that 12mmol/L of NaOH was the cost-efficient and optimal fouling-control dosage for the CEB cleaning.

Biological performance and trace organic contaminant removal by a side-stream ceramic nanofiltration membrane bioreactor

This study evaluated the performance of a side-stream ceramic nanofiltration membrane bioreactor (NF-MBR) system with respect to basic water quality parameters as well as trace organic contaminant (TrOC) removal efficiency. The results show a stable biological performance of the continuous NF-MBR system with high effluent quality (total organic carbon < 4 mg L−1 and NH4+–N below the detection limit). Significantly higher performance by this NF-MBR in comparison to the conventional microfiltration/ultrafiltration MBR regarding the removal of a large number of TrOCs was observed. TrOC removal efficiency depended on their hydrophobicity and molecular features. All hydrophobic compounds (LogDpH=6 > 3) were well removed (>85%), except diazinon (59 ± 7%). Hydrophilic compounds containing electron donating groups were also well removed (>90%). By contrast, hydrophilic compounds containing electron withdrawing groups were poorly removed (8–54%). Most of the 40 TrOCs investigated in this study did not accumulate in the sludge. Only three hydrophobic compounds, namely amitriptyline, triclosan and triclocarban showed considerable accumulation in sludge (>500 ng g−1). Mass balance indicated biodegradation/transformation as the most significant TrOC removal mechanism by this NF-MBR.

Characterization of membrane fouling in submerged ceramic membrane photobioreactors fed with effluent from membrane bioreactors

The effect of hydraulic retention time (HRT) on the membrane fouling behavior of submerged ceramic membrane photobioreactors (SCMPBRs) fed with effluent from a submerged ceramic membrane bioreactor (SCMBR) was investigated. The effluent from a SCMBR was continuously fed to three SCMPBRs operated at different HRTs (72, 24, and 6.5h) for a period of 100d. Results of the effect of mixed liquors characteristics on fouling showed that mixed liquor suspended solids (MLSS), zeta potential and extracellular polysaccharides (EPS) were not the key factors leading to various fouling behaviors for the SCMPBRs. Membrane fouling rates increased with lower operating HRTs through increased production of carbohydrates in soluble microbial product (SMP). The transmembrane pressure (TMP) value of SCMPBR6.5h exceeded 30kPa after 68d of operation, while the TMP of SCMPBR72h and SCMPBR24h were relatively constant throughout the 100d. Different membrane fouling phenomena were observed at different HRTs. It was noted that biological reactions (e.g., hydrolysis) were induced on the biofilm/biocake layer formed on the membrane surface when operating SCMPBR at long HRT (i.e., 72h). For SCMPBR operating at short HRT (i.e., 6.5h), fouling layer and active layer developed on the membrane surface facilitated sieving of colloidal particles and organics. The detailed composition of the organic compounds on membrane foulants in the SCMPBR6.5h showed that carbohydrates and proteins were the major foulants. The finding of much higher organic in non-filtered membrane foulant samples as compared to filtered samples together with the findings from membrane fouling resistance distribution, molecular weight distribution (MWD) and particle size distribution (PSD) indicated that macromolecular compounds contributed more to membrane fouling than those small molecular compounds or soluble compounds.

Treatment of domestic wastewater with an anaerobic ceramic membrane bioreactor (AnCMBR).

In this study, a ceramic membrane with a pore size of 80 nm was incorporated into an anaerobic membrane bioreactor for excellent stability and integrity. Chemical oxygen demand (COD) removal efficiencies by biodegradation reached 78.6 ± 6.0% with mixed liquor suspended solids (MLSS) of 12.8 ± 1.2 g/L. Even though the total methane generated was 0.3 ± 0.03 L/g CODutilized, around 67.4% of it dissolved in permeate and was lost beyond collection. As a result, dissolved methane was 2.7 times of the theoretical saturating concentration calculated from Henry's law. When transmembrane pressure (TMP) of the ceramic membrane reached 30 kPa after 25.3 d, 95.2% of the total resistance was attributed to the cake layer, which made it the major contributor to membrane fouling. Compared to the mixed liquor, cake layer was rich in colloids and soluble products that could bind the solids to form a dense cake layer. The Methanosarcinaceae family preferred to attach to the ceramic membranes.

Effects of dissolved organic matters (DOMs) on membrane fouling in anaerobic ceramic membrane bioreactors (AnCMBRs) treating domestic wastewater

Anaerobic membrane bioreactors (AnMBRs) have been regarded as a potential solution to achieve energy neutrality in the future wastewater treatment plants. Coupling ceramic membranes into AnMBRs offers great potential as ceramic membranes are resistant to corrosive chemicals such as cleaning reagents and harsh environmental conditions such as high temperature. In this study, ceramic membranes with pore sizes of 80, 200 and 300 nm were individually mounted in three anaerobic ceramic membrane bioreactors (AnCMBRs) treating real domestic wastewater to examine the treatment efficiencies and to elucidate the effects of dissolved organic matters (DOMs) on fouling behaviours. The average overall chemical oxygen demands (COD) removal efficiencies could reach around 86–88%. Although CH4 productions were around 0.3 L/g CODutilised, about 67% of CH4 generated was dissolved in the liquid phase and lost in the permeate. When filtering mixed liquor of similar properties, smaller pore-sized membranes fouled slower in long-term operations due to lower occurrence of pore blockages. However, total organic removal efficiencies could not explain the fouling behaviours. Liquid chromatography-organic carbon detection, fluorescence spectrophotometer and high performance liquid chromatography coupled with fluorescence and ultra-violet detectors were used to analyse the DOMs in detail. The major foulants were identified to be biopolymers that were produced in microbial activities. One of the main components of biopolymers – proteins – led to different fouling behaviours. It is postulated that the proteins could pass through porous cake layers to create pore blockages in membranes. Hence, concentrations of the DOMs in the soluble fraction of mixed liquor (SML) could not predict membrane fouling because different components in the DOMs might have different interactions with membranes.

Biodegradation of olive mill wastewater in a membrane bioreactor: acclimation of the biomass and constraints

In order to overcome the toxic effect of olive mill wastewater (OMWW) on biomass during biological treatment, this work will test OMWW biodegradation in a membrane bioreactor (MBR) using an acclimation procedure and will study its constraints. Special focus will be put on soluble microbial products (SMP) analysis in MBR and their impact on membrane fouling. The study was realized in an external ceramic ultrafiltration MBR which offers more flexibility than the other biological treatments (i.e. independence between both hydraulic and sludge retention time) and a smaller footprint. Fed with a mass ratio of 40% OMWW/60% glucose, MBR biomass showed efficient chemical oxygen demand and polyphenols removal rates of, respectively, 90 and 65% despite a low activity of 3.2 mgO2 gMLVSS−1 h−1 due to the harsh and toxic environment. Moreover, HPLC analysis has showed a removal from the permeate of the major phenolic compounds including hydroxytyrosol, tyrosol, and caffeic acid. The monitoring of SMP concentrations has contributed to identify the presence of an environmental stress during OMWW input. Polysaccharide and protein are the main SMP fractions released with, respectively, 10 ± 0.1–20 ± 0.5 mg gMLVSS−1 and 4 ± 0.01–8 ± 0.01 mg gMLVSS−1. These SMP and higher molecular weight compounds brought by OMWW were found to be partially responsible for the intensive membrane fouling obtained. The feasibility of biomass acclimation directly to OMWW composed of multi-phenolic compounds was proved in MBR and its constraints were discussed. Microfiltration membrane would be suggested to overcome the constraints observed when ultrafiltration membrane was used (150 kDa).

Effects of step-feeding and internal recycling on nitrogen removal in ceramic membrane bioreactors, and their hydraulic backwashing characteristics

Both lab-scale (50L/day) and pilot-scale (10m3/day) ceramic membrane bioreactors (CMBRs), equipped with two additional implements (step-feeding and internal recycling), have been tested for the removal of nitrogen and organic matter from municipal wastewater. During the 180days of operation, 0.5Q of step-feeding increased the removal rate of total nitrogen by 46.2% in the lab-scale CMBR, whereas a 59.0% increase was observed with the additional 3Q internal recycling in the pilot-scale CMBR. This was presumably due to the supply of insufficient carbon source as an electron donor in the denitrification stage. The ceramic membrane also exhibited high rigidity sufficient for periodic backwashing using the highly-pressurized permeate. A constant flux test with 30s of backwashing after every 9.5min of filtration successfully removed foulants from the pores of the ceramic membrane, and instantaneously restored the trans-membrane pressure (TMP). During the test, the TMP in case of without the hydraulic backwashing steadily increased (20–80kPa) for 40min, whereas it took more than two times to reach the same TMP in the case of with the hydraulic backwashing, which eventually doubled the time span between required chemical washings.

Biodiesel production by microalgae cultivated using permeate from membrane bioreactors in continuous system.

Microalgae in three submerged ceramic membrane photobioreactors (SCMPBRs) with different hydraulic retention times (HRTs) were fed with permeate of a submerged ceramic membrane bioreactor for a period of 3 months to investigate the lipid content and also the biodiesel quality produced at different HRTs. The lipid content, lipid productivity and fatty acid compositions for all three SCMPBRs were not significantly different at the 95% confidence level. These results suggested that insignificant change in the amount of fatty acids was observed at different HRTs that supplied varying concentration of nitrate in the medium. Among the fatty acids, palmitic acid, palmitoleic acid, oleic acid and linoleic acid were the main components, whereas stearic acid was a minor fatty acid. Since there was insignificant effect of HRT on lipid content, lipid productivity and fatty acid compositions, the optimum HRT for SCMPBRs can then be designed based on optimum nutrient removal performance and low membrane fouling propensity.

Phenolic Shock Load in a Submerged Ceramic Membrane Bioreactor for the Degradation of Aqueous Phenol

Laboratory-scale experiments were conducted to study the treatment of phenol contaminated wastewater using submerged ceramic membrane bioreactor (SCMBR) with flat-sheet-type ceramic membrane module. The effects of organic loading rate on the phenol degradation were studied using Polyseed bacteria containing a mixed culture of microorganisms with and without acclimatization. The experimental results showed that the phenol removal efficiency was over 75% at phenol concentrations of 400 mg/l with the COD removal efficiency of greater than 80%. For phenol concentrations of 800 mg/l, the removal efficiency dropped to about 40%, however, the system returned to its previous treatment efficiency once the phenol load was removed. As a result, it was observed that the bacteria survived at the high load phenol concentration of 800 mg/l

Fouling control mechanism by suspended biofilm carriers addition in submerged ceramic membrane bioreactors

Membrane fouling has been the main concern deterring widespread applications of membrane bioreactors. In this study, porous suspended biofilm carriers were introduced to submerged ceramic membrane bioreactors (SCMBR) treating domestic wastewater to explore its effectiveness in alleviating membrane fouling. Results showed that biofilm carriers addition was effective in mitigating cake formation on the membrane surface that, in turn, helped to retard membrane fouling in SCMBR. The SCMBR without carriers had 2.7 times higher cake resistance and 1.5 times higher total resistance than the corresponding values observed in the SCMBR with carriers, indicating that the addition of biofilm carriers in SCMBR decreased the cake resistance by 72.7% over a similar period of operation. Both higher concentration of biomass and inorganic matters in the cake layer facilitated a more rapid TMP increment in the SCMBR without carriers. The liquid chromatography–organic carbon detector (LC–OCD) results indicated that a higher concentration of low molecular weight compounds (less than 1000) in the cake layer contributed to the faster fouling development observed in the SCMBR without carriers. The excitation–emission matrix florescence spectra of the cake layer showed the existence of two obvious protein-like substance peaks at the wavelength of Ex/Em=250–270/380–390nm and Ex/Em=250–260/420–430nm in both SCMBRs. However, relative dominance of the protein-like substance was relatively higher in the SCMBR without carriers, with an intensity of 284.9 occurring at the first peak and an intensity of 244.7 at the second peak, which confirmed that higher biopolymer contents were detected in the cake layer of the SCMBR without carriers. Other characteristics of the cake as well as the biomass suspensions were also evaluated in this study.

Comparison of fouling characteristics in different pore-sized submerged ceramic membrane bioreactors

Membrane fouling, the key disadvantage that inevitably occurs continuously in the membrane bioreactor (MBR), baffles the wide-scale application of MBR. Ceramic membrane, which possesses high chemical and thermal resistance, has seldom been used in MBR to treat municipal wastewater. Four ceramic membranes with the same materials but different pore sizes, ranging from 80 to 300 nm, were studied in parallel using four lab-scale submerged MBRs (i.e., one type of ceramic membrane in one MBR). Total COD and ammonia nitrogen removal efficiencies were observed to be consistently above 94.5 and 98%, respectively, in all submerged ceramic membrane bioreactors. The experimental results showed that fouling was mainly affected by membrane’s microstructure, surface roughness and pore sizes. Ceramic membrane with the roughest surface and biggest pore size (300 nm) had the highest fouling potential with respect to the TMP profile. The 80 nm membrane with a smoother surface and relatively uniform smaller pore openings experienced least membrane fouling with respect to TMP increase. The effects of the molecular weight distribution, particle size distribution and other biomass characteristics such as extracellular polymeric substances, zeta potential and capillary suction time, were also investigated in this study. Results showed that no significant differences of these attributes were observed. These observations indicate that the membrane surface properties are the dominant factors leading to different fouling potential in this study.

Olive mill wastewater treatment in a membrane bioreactor: process stability and fouling aspects

An external ceramic membrane bioreactor was used to carry out an experimental study of process stability and fouling aspects for olive mill wastewater (OMW) treatment. Three diluted OMW solutions were used to continuously feed the reactor. An acclimated biomass was employed and the process stability was followed on the basis of the permeate quality and some operating parameters (pressure, temperature, mass flow and dissolved oxygen). Several backpulse combinations were tested to determine the best filtration and backwash time. It appeared that a short backpulse duration was sufficient and that the behaviour, in terms of the permeate flux versus time, stabilized. In terms of increased permeate flux, the effect of the backpulsing depended on the nature of the solution. This improvement was limited, but, in the long‐term, backpulsing makes it possible to maintain a constant permeate flux over a period of several days.

Performance and fouling characteristics of different pore-sized submerged ceramic membrane bioreactors (SCMBR)

The membrane bioreactor (MBR), a combination of activated sludge process and the membrane separation system, has been widely used in wastewater treatment. However, 90% of MBR reported were employing polymeric membranes. The usage of ceramic membranes in MBR is quite rare. Four submerged ceramic membrane bioreactors (SCMBRs) with different membrane pore size were used in this study to treat sewage. The results showed that the desirable carbonaceous removal of 95% and ammonia nitrogen removal of 98% were obtained for all the SCMBRs. It was also showed that the ceramic membranes were able to reject some portions of the protein and carbohydrate, whereby the carbohydrate rejection rate was much higher than that of protein. Membrane pore size did not significantly affect the COD and TOC removal efficiencies, the composition of EPS and SMP or the membrane rejection rate, although slight differences were observed. The SCMBR with the biggest membrane pore size fouled fastest, and membrane pore size was a main contributor for the different fouling potential observed.