Hybrid Membrane Bioreactor Research Articles

Removal of organic compounds of real textile dyeing wastewater by pilot scale combination process of anoxic baffled reactor-hybrid membrane bioreactor

A pilot-scale combination process of anoxic baffled reactor -hybrid membrane bioreactor for the real textile dyeing wastewater treatment was investigated. Anoxic baffled reactor as a hydrolysis process pre-treatment was performed well, which achieved 35.6 % COD removal efficiency when hydraulic retention time (HRT) was 16 h. The total COD removal efficiency of the combined process was 83.8 %. GC-MS analysis results demonstrated that the main component of raw influent was alkanes including 13 types. After hydrolysis process, the types of alkanes decreased to 5. In subsequent aerobic treatment phase, alkanes of supernatant of HMBR increased to 19, but total organic compounds category decreased to 24. New intermediate CholestaN-3β-ol production demonstrated that some complicated structures or large molecules substances in raw wastewater could be decomposed. GC-MS quantitative analysis results further showed that some toxic and hazardous substances, such as toluene, styrene, 1,2-dichlorobenzene were still in the final effluent. However toxic compounds e.g. phenols could be removed in the subsequent aerobic process. Therefore, most organic pollutants could be removed using the combined process. There were still some amounts of toxic compounds present in the final effluent.

A step-feed hybrid membrane bioreactor process for advanced wastewater treatment

A step-feed anaerobic-(oxic/anoxic) n -membrane bioreactor [An-(O/A) n -MBR] process was developed to treat synthetic domestic wastewater. Characteristics of nutrient removal and membrane fouling at three hydraulic retention time (HRT) settings were investigated on a lab-scale system. Results showed that COD removal in the An-(O/A) n -MBR process was high and stable (up to 98%) throughout the operation. At the constant sludge retention time condition, MLSS concentration increased with the decrease of HRT. Removal efficiencies of the total nitrogen (TN) and the total phosphorus (TP) demonstrated the same trend. When the HRT was at 8.70, 6.96 and 4.97 h, the average removal efficiencies of TN and the TP were 73.15%, 79.76% , 81.98% and 67.79%, 80.99%, 92.16%, respectively. However, analysis of membrane fouling showed that the short HRT obtained by high flux operation resulted in the acceleration of membrane fouling.

Membrane Fouling Control of Hybrid Membrane Bioreactor: Effect of Extracellular Polymeric Substances

A hybrid membrane bioreactor (HMBR) was developed by adding biofilm carriers into a conventional membrane bioreactor (CMBR), and a study was conducted on the characteristics of the activated sludge in the HMBR and CMBR with attention paid to the effect of extracellular polymeric substances (EPS) on membrane fouling. As a result, lower EPS concentrations were detected from the HMBR than the CMBR, bringing about a substantial improvement in the sludge properties. The larger particle size, more compact particle structure, and better settleability of the sludge in the HMBR resulted in lower cake layer resistance and much slower TMP increase.

Performance of a hybrid membrane bioreactor in municipal wastewater treatment

A pilot-scale hybrid membrane bioreactor (HMBR) was developed by introducing biofilm carriers into a conventional membrane bioreactor (CMBR) and operated for about one year for municipal wastewater treatment. Experiments were conducted to investigate the performances of the HMBR for organic removal, nutrients removal and membrane fouling control comparing with the CMBR. The comparative study results indicated that at a constant hydraulic retention time (HRT) of 10 h and sludge retention time (SRT) of 10 d, the HMBR apparently improved the organic removal. To be specific, the effluent COD in the CMBR averaged 44 mg/L, but it dropped to 24.5 mg/L in the HMBR. Correspondingly, the COD removal rate increased from 90.4% to 94.2%. Regarding NH 4 +–N, TN and TP, the HMBR improved the removal rate by 4.2%, 13.7% and 1.7%, respectively. Another eye-catching feature of the HMBR was that the increase of transmembrane pressure (TMP) was slowed down during the operation at a constant flux of 10 L/m 2 h. In CMBR, the duration for TMP to reach the prescribed maximum of 20 kPa after chemical washing was 57–65 days, while in the HMBR it was prolonged to 92 days or longer. This indicated a favorable condition of membrane fouling control by HMBR operation.

Ozonation effect on natural organic matter adsorption and biodegradation – Application to a membrane bioreactor containing activated carbon for drinking water production

More stringent legislation on dissolved organic matter (DOM) urges the drinking water industry to improve in DOM removal, especially when applied to water with high dissolved organic carbon (DOC) contents and low turbidity. To improve conventional processes currently used in drinking water treatment plants (DWTPs), the performances of a hybrid membrane bioreactor containing fluidised activated carbon were investigated at the DWTP of Rennes. Preliminary results showed that the residual DOC was the major part of the non-biodegradable fraction. In order to increase the global efficiency, an upstream oxidation step was added to the process. Ozone was chosen to break large molecules and increase their biodegradability. The first step consisted of carrying out lab-scale experiments in order to optimise the necessary ozone dose by measuring the process yield, in terms of biodegradable dissolved organic carbon (BDOC). Secondly, activated carbon adsorption of the DOC present in ozonated water was quantified. The whole process was tested in a pilot unit under field conditions at the DWTP of Rennes (France). Lab-scale experiments confirmed that ozonation increases the BDOC fraction, reduces the aromaticity of the DOC and produces small size organic compounds. Adsorption tests led to the conclusion that activated carbon unexpectedly removes BDOC first. Finally, the pilot unit results revealed an additional BDOC removal (from 0.10 to 0.15 mg L −1) of dissolved organic carbon from the raw water considered.

Filtration characteristics of activated sludge in hybrid membrane bioreactor with porous suspended carriers (HMBR)

The suspended carriers were efficient in controlling membrane fouling in hybrid membrane bioreactor with porous suspended carriers (HMBR). The purpose of this study consisted in investigating the effect of suspended carriers on the sludge suspension, especially the filterability of sludge suspension. The filterability of sludge suspension in HMBR and general membrane bioreactor (MBR) were investigated and compared in parallel conditions by dead-end filtration for better evaluating the influence of suspended carriers on the sludge suspension. Several aspects of sludge suspension such as filtration resistance, specific cake resistance and particle size were discussed. During long-term operation the filtration resistances rose gradually in the early stage (about 100 days) and then increased rapidly, but there was a slight difference between MBR and HMBR with the prolongation of operation time. The granulometric analysis revealed that the mean particle size of sludge suspension of HMBR decreased more sharply than that of MBR, because the fluidized carriers in HMBR would impose shear stresses on sludge flocs and induce the destruction of the network of sludge zoogloea. Dead-end filtration experiments indicated that the resistance-increasing rates of three portions of sludge suspension were in the order of supernatant > dissolved organics > microbial flocs. In order to further understand the filterability of sludge suspension, the specific cake resistance (α or α.C) of sludge suspension and supernatant in HMBR and MBR were determined. During long-term operation the α and α.C increased with operation time. These results revealed that the suspended carriers in HMBR had appreciably negative effect on the biological characteristics and filterability of the sludge suspension, but they were efficient in controlling membrane fouling during continuous operation of HMBR.

Hybrid membrane bioreactor technology for small water treatment utilities: Process evaluation and primordial considerations

A hybrid membrane bioreactor (MBR) technology was investigated for treatment of natural waters containing natural organic matter (NOM), nitrate, alachlor and viruses. The NOM are precursors to disinfection byproducts (DBPs) such as trihalomethanes, and potential cause for microbial growth in distribution systems. Batch bioreactor studies optimized the carbon-to-nitrogen (C/N) ratio, temperature and pH for biological denitrification. Mini-pilot MBR studies with ethanol as electron donor were conducted under three scenarios: no powder activated carbon (PAC) or biomass, biomass alone, and combination of PAC and biomass. The removals of nitrate, alachlor, total organic carbon (TOC), trihalomethane formation potential (THMFP) and MS-2 virus were revaluated. Nitrite and ethanol residuals were well below their detection limits in the MBR effluent under steady-state conditions. Using biomass alone, the removal efficiencies for NOM (as TOC), alachlor, and THMFP were 60, 36 and 61%, respectively; whereas, on combining PAC and biomass they increased to 84, 99.8 and 98%. The virus rejection mechanisms postulated were size exclusion, sorption to membrane surface, attachment to bio-particles, and sorption onto foulant or cake layers. The MS-2 removals exceeded 3.8-logs under optimal process conditions. Membrane fouling and flux decline patterns under the three experimental scenarios were well described by the resistance model. The flux decline was characterized by three distinct stages, namely, initial conditioning fouling, rapid fouling, and slow fouling. The Tustin groundwater was associated with lower organic fouling but higher inorganic fouling than the Fountain Valley groundwater.

Application of chemical precipitation and membrane bioreactor hybrid process for piggery wastewater treatment

This study was conducted to investigate the chemical precipitation (CP) and membrane bioreactor (MBR) hybrid process for the treatment of piggery wastewater. Average removal efficiencies for BOD, COD and turbidity in CP process were 64.3%, 77.3% and 96.4%, respectively. CP process had a moderate effect on NH 3–N removal (40.4%) which improved up to 98.2% mainly due to nitrification and filtration processes in MBR. The average removal efficiencies of BOD, COD and turbidity in MBR were 99.5%, 99.4% and 99.8%, respectively. Monod equation was used to explain the microbial activities in terms of specific growth rate. The specific growth rate of bacteria in aeration tank (N-batch) and anoxic tank (D-batch) were 0.013 and 0.005 d −1 with a biomass yield of 0.78 and 0.43 mg MLSS produced/mg COD utilized, respectively. Microorganisms from the N-batch and D-batch showed a low-level of nitrifying and moderate-level of denitrifying capabilities which were 1.08 mg NH 3–N/(g MLVSS.h) and 2.82 mg NO 3–N/(g MLVSS.h), respectively. Carbohydrates were the main component in extracellular polymeric substance (EPS) compounds that could be attached to the membrane surface easily and led to membrane biofouling. The increase of MLSS, EPS and sludge viscosity concentration, decrease of sludge floc size and incomplete chemical cleaning procedure resulted in the increase of membrane resistance. Total membrane resistance increased from 3.19 × 10 12 m −1 to 5.43 × 10 14 m −1.

New process for alleviation of membrane fouling of modified hybrid MBR system for advanced domestic wastewater treatment

A pilot-scale hybrid membrane bioreactor using a submerged flat panel membrane was designed and applied for advanced treatment of domestic wastewater. The new process adapted to the hybrid membrane bioreactor exhibits substantial decrease in membrane fouling and much easier cleaning. In this study, the new process configurations including the addition of anoxic/anaerobic zones, the package of synthetic fibrous fabric carrier for biofilm attached growth, activated sludge recycling and modified dosage of polished diatomite with high activity and multi-functions were investigated to select the optimal operational parameters for the hybrid membrane bioreactor system. The carrier package in the aerobic zone contributed 3.65 g/L (maximum) of fixed biomass to the system, thus reducing the suspended biomass, and has decreased the membrane cleaning cycle remarkably. The operation performance at the sludge recycle rate 0, 100%, 200% and 300% showed that, the trans-membrane pressure of flat panel membrane declined sharply with the increase of sludge recycling rate within a certain range, and 200% was decided to be optimal for in the membrane bioreactor system. EPS concentration in each sludge recycling rate was 135 mg/L, 92 mg/L, 68 mg/L and 55 mg/L respectively. The addition of anoxic and anaerobic zones degraded some large molecular organic compounds, which facilitated the biodegradation and removal of organic substances in aerobic zone. The modified dosage of polished diatomite has played a major important role for both preventing of membrane from fouling and its much easier cleaning when it formed.

Effect of ferric chloride on fouling in membrane bioreactor

Membrane fouling has been the main obstacle to the wide application of membrane bioreactors (MBRs). The aim of this study was to investigate the effects of ferric chloride on retarding membrane fouling in MBRs. Changes in the modified fouling index (MFI) and the zeta potential of sludge flocs were used to determine the optimal concentration of Fe(III). The optimal Fe(III) concentration of 1.2 mM significantly improved the filterability of mixed liquor. Fe(III) supplied positive charges for soluble macromolecular substances and sludge flocs, and enhanced the function of charge neutralization. The effects of the optimal concentration of Fe(III) on the molecular weight (MW) distributions of soluble microbial products (SMP) and the particle size distributions of the flocs in the hybrid MBR (HMBR) were also tested. The addition of Fe(III) at the optimal concentration reduced both SMP with MW > 10 kDa in the supernatant and the fraction of small particles in the range 1–10 μm in the flocs. Elemental analysis of the extracellular polymeric substances (EPS) in the activated sludge indicated that Fe(III) added to the HMBR system interacted with the negatively charged groups on the EPS and enhanced the bioflocculation of small particles in the activated sludge. The cleaning efficiency achieved by physically and chemically washing the membrane in the HMBR was compared with that in the conventional MBR. Cleaning with deionized water followed by a metal-chelating agent (ethylenediaminetetraacetic acid) was highly effective for the fouled membrane of the HMBR.

Use of a hybrid membrane bioreactor for the treatment of saline wastewater from a fish canning factory

A new pilot scale hybrid biofilm-suspended biomass membrane bioreactor was used to treat two wastewater streams generated in a fish canning factory. During a first stage, wastewater generated during tuna cooking with brine was treated. COD and N content were between 7.8–11.8 g COD/L and 1.2–1.8 g N/L, respectively. Salt concentration was up to 84 g/L. COD removal efficiency was affected by salinity, but after 73 operating days adaptation of the sludge to the hypersaline conditions took place. COD efficiency of 92% was obtained after adaptation of the sludge to the salinity. During a second stage, wastewaters generated during tuna cooking by steam injection were treated. HRT was fixed at 5 d. Organic loading rate was up to 4 kg COD/m 3 d. COD concentration in the permeate was lower than 100 mg/L throughout this period. Salt concentration below 15 g/L did not affect nitrification. NLR was gradually increased up to 0.7 kg N/m 3 d. Total nitrogen concentration in the permeate was lower than 100 mg N/L, and nitrate was below 65 mg N/L during the whole experimental period. Moreover, very low nitrate concentrations of less than 1 mg N/L were observed during the period in which a NLR up to 0.55 kg N/m 3 d was applied.

Characteristics of Membrane Fouling in an Anaerobic-(Anoxic/Oxic)n-MBR Process

Abstract The characteristics of membrane fouling and cleaning, in a hybrid MBR process, was investigated. Under the condition of sub-critical flux operation, a characteristic three-stage trans-membrane pressure (TMP) profile is observed as time passes. The initially extended period of slow pressure rise, followed by a somewhat faster rise, is then supplanted by a sudden transition to rapid pressure rise. Membrane cleaning experiments and SEM examination make it apparent that the rapid TMP rise is mainly caused by the accumulation of a surface cake layer, which is a reversible fouling that can be removed by tap water washing. Fouling caused by a gel layer, which is an irreversible fouling, can be removed efficiently by chemical cleaning. NaClO can oxidize the gel layer, which is formed mainly of macro-molecular organic substances. The HCl can remove inorganic particles formed by Ca 2+ , Mg 2+ ions etc. The sequence of chemicals used in membrane cleaning has an influence on the cleaning result. The effect of the NaClO+HCl cleaning procedure is superior to that of the HCl+NaClO one. Particle size distribution measurements (PSD) reveal that fine particles are inclined to deposit or attach on the membrane surface, or in the membrane pores, and caused rapid fouling.

NORIT AirLift MBR: side-stream system for municipal waste water treatment

The Ootmarsum wastewater treatment plant (WWTP) is owned by the water authority Regge & Dinkel (WRD) and is situated in the municipality of Dinkelland (eastern part of The Netherlands). The WWTP must be modernised, because it discharges the treated wastewater into a water system with considerable ecological vulnerability. In the restructuring plan the urban water chain/cycle was integrated into an ecological water management approach. In cooperation with Grontmij engineering consultants a design study was carried out resulting in the choice for a so-called hybrid system. Such a system combines a conventional system followed by a sand filter with a membrane bioreactor (MBR). With a hybrid MBR, the costs can be reduced relatively to those of a complete MBR plant without making concessions in terms of effluent quality. After an intensive selection procedure NORIT Membrane Technology (NMT) was selected with the novel NORIT AirLift MBR system. The construction work of the 650 m 3/h plant started in mid-2005 and will be completed by late 2006; start-up of the full scale will be early 2007. As preparation for the full scale plant operation an intensive pilot study is currently being performed in order to develop a start-up protocol, to train operators, to check control philosophies, and to optimise the overall processing.

Study of a hybrid process: Adsorption on activated carbon/membrane bioreactor for the treatment of an industrial wastewater

The aim of this study is to compare a membrane bioreactor (MBR) and a hybrid membrane bioreactor (HMBR) coupling membrane separation, biological activity and adsorption on powdered activated carbon (PAC) in order to remove a toxic compound. The two processes were compared in terms of water treatment efficiency, membrane fouling and biological sensitivity to the toxic compound. Experiments were performed with synthetic wastewater and 2,4-dimethylphenol (DMP) was chosen as a molecule representative from toxic compounds present in effluents from the oil industry. This study showed the interests of the hybrid process in comparison with a conventional MBR, due to the positive effects of PAC adjunction: results pointed out that addition of activated carbon could structure the biomass, then the deposit at the membrane surface, and decrease proteins and carbohydrates concentrations in the HMBR supernatant, that allows a reduction of membrane fouling. Results show that PAC adjunction slightly reduces sludge production in the HMBR. Toxic injection inhibits the biological activity in the MBR whereas the biological activity is maintained in the HMBR, with a biodegradation of the toxic compound after an acclimation period.

Hybrid membrane bioreactor for water recycling and phosphorus recovery

This paper deals with the performance of hybrid membrane bioreactor (MBR) combining the precoagulation/sedimentation and membrane bioreactor. The hybrid MBR not only produces the treated water with excellent permeate quality but also shows much lower membrane fouling than the conventional MBR. It may come from its extremely low F/M ratio to maintain the low viscosity even in the high MLSS concentration range of about 20,000 mg/L. Some results of microbial community analysis in MBRs was conducted to demonstrate the other reason for its lower membrane fouling. Hybrid MBR has a high potential to be used for the recycling use of the municipal wastewater. Coagulated sludge produced in the hybrid MBR is a promising phosphorus resource. This paper also contains a recent progress of phosphorus recovery technology, which uses a new phosphoric acids absorbent, i.e. the hexagonal mesostructured zirconium sulfate (ZS). The ZS has the extremely high adsorption capacity of phosphoric acids through anion exchange. The adsorbed phosphoric acids are released from the ZS in a high pH range of about 13.

Membrane fouling control in a submerged membrane bioreactor with porous, flexible suspended carriers

Membrane fouling has been the main obstacle to the wide application of membrane bioreactors (MBR). A hybrid membrane bioreactor (HMBR) with porous, flexible suspended carriers was explored that was efficient in controlling membrane fouling, especially cake layers. In order to investigate the influence of suspended carriers on the filtration performance of the HMBR, two kinds of bioreactors—MBR and HMBR—were tested in parallel processing. In the short-term trials, the critical flux of HMBR increased by 20% and the cake resistance of HMBR decreased by 86% in comparison with MBR. During the long-term experiments, the increase rate of suction pressure for HMBR accounted for 30% of that for MBR, indicating that the degree of membrane fouling for HMBR was far lower than that for MBR. These observations revealed that suspended carriers play an important role in governing the filtration conditions and decreasing fouling resistance. In order to understand the influence of suspended carriers better on the system performance, several parameters such as cake layers of membrane surface, characteristics of the mixed liquor and filterability of the supernatant and the activated sludge suspension were investigated.

Performance improvement of hybrid membrane bioreactor with PAC addition for water reuse

A study was carried out on a hybrid (AS-SBF) membrane bioreactor (HMBR) for the municipal wastewater reclamation and reuse at Chengfengzhuang WWTP in Daqing City, Heilongjiang Province. It was found that the effects of DO and water temperature on performance of the HMBR was significant. Under the conditions of water temperature in range of 10-14 degrees C, pH of 6.6- 7.0, DO of 4-6 mg/l and HRT of 7 h, the HMBR exhibited removal efficiencies for CODcr, BOD5, NH3-N and TN of 96.7%, 98.9%, 93.7% and 60.5% respectively. The turbidity of effluent from HMBR was below 1 NTU. The effluent of HMBR meets the standard of wastewater reclamation for oil exploitation. PAC was added into the bioreactor at the second operating stage, in order to further research parameters variation. The flux was improved by 53.2%, compared to the membrane without PAC-addition, due to formation of a PAC pre-coat layer on the membrane surface, with lots of advantages such as larger granules, higher porosity, non-compressibility, higher filterability and easy removal, compared with pure biomass layer. In addition, the performance of HMBR was further improved, due to adsorption and degradation of SMPs, the average removal of CODcr and TN was further improved by 5.1% and 13.5% respectively. Biomass in the HMBR was quantitatively measured, of which the biofilm played a major role in pollutants removal.

The BIOREK® concept: a hybrid membrane bioreactor concept for very strong wastewater

The BIOREK® manure and/or organic waste treatment process based on anaerobic digestion and subsequent treatment of the effluent with conventional and novel membrane technologies is presented. The process consists of a mesophilic anaerobic digester coupled to a cross-flow tubular ultrafiltration membrane (ADUF). The clear, sterile effluent, rich in ammonium (N), soluble phosphates (P) and potassium (K) is processed into saleable fertiliser products and potable, demineralised water. Compared to conventional solid–liquid treatment technologies available, the proposed technology not only alleviates organic waste-handling problems, but also retains biomass, thus enabling more complete conversion of the organic substances in the feed. The present work investigates the use of a thermophilic (50–55°C) as opposed to a mesophilic digester (30–37°C). It will be shown that the UF flux increases rapidly when increasing the feed temperature mainly due to a decrease in viscosity. Further the investigation will show that the removal of volatile ammonia with membrane contactor (CM) technology is far superior to that expected by conventional steam stripping. It is found that proper UF-permeate decarbonisation and pH adjustment lead to improved ammonia transfer rates. Ammonia removal efficiencies of up to 99.9% are reached at ambient feed temperatures.

An innovative biofilm-suspended biomass hybrid membrane bioreactor for wastewater treatment

An innovative membrane-assisted hybrid bioreactor for wastewater treatment was developed in our laboratory. This system was composed by a hybrid circulating bed reactor coupled in series to an ultrafiltration membrane module. Biomass was maintained growing both in suspension and in biofilms onto small rough plastic particles. The growth of nitrifiers in the hybrid system was promoted into biofilms while heterotrophs were in suspension. This made it feasible to operate the unit at higher SRT for nitrifiers than for heterotrophs, which resulted in the presence of a higher fraction of nitrifiers in the reactor. The hybrid bioreactor was used to treat two industrial wastewaters—from a tannery and a fish-canning factory—with high nitrogen and organic matter content. COD removals of around 99% were obtained at an organic loading rate (OLR) of 6.5 kg COD/m 3·d and an NLR of 1.8 kg N-NH + 4/m 3·d during the treatment of the fish canning wastewater. Between 50–60% of the nitrifying capacity of the reactor was located in the biofilm. During the treatment of the tannery wastewater, OLR and ALR were stepwise increased up to 4.5 kg COD/m 3·d and 1.2 kg N-NH + 4/m 3·d, respectively. COD removal efficiency was 95%, while up to 97% of ammonia removal was obtained, the concentration of ammonia in the effluent being low, 10 mg N-NH + 4/L. For both industrial wastewaters, the biofilm nitrifying activity was not affected by the variations in the organic loading rates, COD concentration in the influent or characteristics of the influent. Most of the dissolved COD was consumed by suspended biomass in the reactor, avoiding the competition between nitrifiers and heterothophs in the biofilm. Moreover, the membrane filtration unit made it feasible to operate the reactor at high OLR without problems related to either the settling properties of the sludge or the drop in the nitrogen conversion, which usually occurs in other hybrid biological reactors operated at high OLR or NLR.

Performance of membrane bioreactor combined with pre-coagulation/sedimentation

This paper deals with the performance of a hybrid membrane bioreactor (MBR) combined with pre-coagulation/sedimentation. Primary clarifier effluent in a municipal wastewater treatment plant was fed into the hybrid MBR to investigate its performance during long-term operation. Pre-coagulation/sedimentation process efficiently removed the suspended solids including organic matter and phosphorus. Comparison of the hybrid MBR and conventional MBR was made in terms of the permeate quality and membrane fouling. As the organic loading to the MBR was significantly reduced by the pre-coagulation/sedimentation, production and accumulation of extracellular polymeric substances (EPS) may be limited. Therefore, the mixed liquor viscosity in the hybrid MBR was much lower than that in the conventional MBR. These effect caused by pre-coagulation/sedimentation brought a remarkable improvement in both permeate quality and membrane permeability.