Membrane Bioreactor Plant Research Articles

Reproducibility and applicability of the flux step test for a hollow fibre membrane bioreactor

Results from flux step tests conducted on a pilot-scale hollow fibre immersed membrane bioreactor plant (HF iMBR) are reported. Trials combined a classic flux-step test, each step incorporating six backflush cycles, with an extended (15-h) test to evaluate trends in fouling. Both fouling rate, i.e. the rate of increase in transmembrane pressure (dTMP/dt) at a constant flux, and mean permeability were calculated and reproducibility assessed through the standard deviation. Applied nominal fluxes between 5 and 35Lm−2h−1 (LMH) were employed for the flux-step trials, and all experiments were (i) triplicated through simultaneous application across three central membrane elements in the seven-element membrane module, and (ii) repeated four times. Reproducibility was quantified as standard deviation (SD), and assessed with reference to both the mean permeability across the backflush cycle and the irreversible fouling rate across the three modules – the latter both for the short-term and long-term trials.Results indicated greatly reduced fouling (by 80–88% with respect to fouling rate) for the longer-term study compared with the flux-step data. Fouling rate SD values were slightly lower for the flux step data at 20–27% for the four highest flux steps compared with 30% for the longer trial conducted at 20LMH, based on quadruplicated data. Mean permeability data, on the other hand were much more reproducible, with SD values below 8%. It was concluded that significant variations in hydrodynamics can arise across a module comprising a number of elements, accounting for a 20–40% change in fouling rate. However, this cannot account for the differences recorded between the short-term and long-term fouling measurements, which are a facet of the flux step test conditions.

The IFAS-MBR process: a compact combination of biofilm and MBR tecnnology as RO pretreatment

An advanced treatment for wastewater reclamation has been studied for nine months in a pilot plant in the south of Spain. This consisted in a combination of integrated fixed-film activated sludge (IFAS) and membrane bioreactor (MBR) technology (called here IFAS-MBR) with posterior reverse osmosis (RO) for the achievement of a high-quality effluent. The pilot plant was obtained from a former MBR plant, where plastic carriers for the support of the biology were introduced in the second aerobic chamber. The system consisted of two parallel lines, one working with a hollow fibre module and the other with a flat sheet module. After the hollow fibre line, an RO system treated the effluent. The permeability of the process decreased gradually along the experimentation period and after six months, the membrane modules of both lines were chemically cleaned. The RO membranes showed a stable permeability working with the IFAS-MBR permeate and chemically cleaned after four months of operation. The studied system combined the advantages of both IFAS and MBR technologies and it is an interesting choice when the footprint is limited or a high effluent quality is required and it is an attractive pretreatment for reverse osmosis systems.

Design and Performance of the First Full Scale Membrane Bioreactor Plant Treating Oil Refinery Effluent in Brazil

Design and Performance of the First Full Scale Membrane Bioreactor Plant Treating Oil Refinery Effluent in Brazil

Physical and statistical model for predicting a transmembrane pressure jump for a membrane bioreactor

Membrane bioreactors (MBRs) have been widely used to purify wastewater for reuse. However, MBRs are subject to fouling, which is the phenomenon whereby foulants absorb or deposit on the membrane. After long-term operation of MBRs under a condition of constant-rate filtration, transmembrane pressure (TMP) increases rapidly. This TMP jump is one factor making the operation of MBRs difficult. We therefore propose the construction of a model that predicts the timing of a TMP jump. First, a nonlinear function for determining whether a TMP jump will happen was derived from physical knowledge. We then analyzed the nonlinear function statistically with measurement data and constructed a model that detects a TMP jump. The performance of the proposed method was confirmed through the analyses of two data sets obtained from the literature and a data set recorded for a real industrial MBR plant.

Elimination of trace organics in an MBR/RO system for water reuse

An intensive programme for detection of trace organics was performed in a membrane bioreactor (MBR) plant in Almuñécar (south of Spain) over 1 year. The compounds investigated included 15 pharmaceutically active compounds, 12 polycyclic aromatic hydrocarbons and eight other compounds (nonylphenols, linear alkylbenzene sulphonates and phthalates). The MBR operated with two lines in parallel using a hollow fibre and a flat sheet membrane respectively. Additionally, a reverse osmosis (RO) plant treated the MBR permeate over 1 month and the elimination of trace organics by the MBR/RO system was assessed. The elimination efficiency of trace organics by the MBR was similar to that found in a conventional activated sludge plant treating the same influent. The concentration of trace organics was reduced after the MBR to a great extent and no significant differences were found between the two lines operating in parallel. The elimination efficiency increased up to 80–100% after passing the RO system. The results indicated that the MBR effluent reached the standard required by the Spanish Royal Decree for Water Reuse and can therefore be reused for multiple purposes, but advanced treatment like RO is necessary when the highest effluent quality is required.

Stable operation of MBR under high permeate flux

Permeate flux plays a critical role on the stable operation of membrane bioreactor (MBR) system for municipal wastewater treatment. The current commercially available submerged MBR systems, Zenon, Kobota, and Huber, etc. maintained their permeate fluxes at about 20–30 LMH to minimize the fouling potential of the membranes. A pilot scale MBR plant using HYDRASub®/Sterapore SADF® PVDF membrane module was stably operated at flux as high as 35 LMH for about 1 year by optimizing the operating condition of MBR system. The applied high permeate flux also resulted in low specific energy consumption per unit product water. This paper introduced the performance of membrane operated at high flux and discussed the factors affecting the stable operation of MBR. By applying the operating condition to an actual MBR plant, the specific energy consumption could reach a very low level, about 0.46 kWh/m3.

Membrane Bioreactor Process Modeling and Optimization: Ulu Pandan Water Reclamation Plant

AbstractThe operating energy efficiency of the Ulu Pandan membrane bioreactor plant is optimized by artificial neural network (ANN) and bioprocess models. The ANN model mines historical plant data to uncover optimal operating settings. Historical plant data indicate that adjusting the membrane scouring aeration cycle will lead to direct energy savings. The ANN model concurs and shows the same correlation. Changes to plant operations carry substantial risks to the stability of the plant and place limitations on the range of operational variations. A plant risk assessment is conducted to ascertain the risk proposition for the adjustment of operating parameters. The bioprocess model investigates the underlying biological treatment mechanisms to identify the impact of the solids retention time on the volatile suspended solids, soluble microbial products, and endogenous decay coefficient. Results of the modeling show qualitatively good agreement with measured operating data. The concentrations of volatile susp...

Are centralized MBRs coping with the current transition of large petrochemical areas? A pilot study in Porto-Marghera (Venice)

The operation of a pilot scale membrane bioreactor (MBR) provided feedback for the world’s largest centralized MBR plant treating petrochemical wastewater, located in the industrial area of Porto-Marghera, Venice. The main objective was to study the robustness of MBR technology under variable operating conditions of the petrochemical industry. We aimed to reduce the idle volumes of biological reactors and to enhance biomass activity. Five runs were conducted, initially aiming to represent the operating conditions of the full scale MBR and then alternations were introduced, including the addition of more external carbon source, the reduction of the anoxic compartment volume, changes in configuration and an increase of influent load. Ammonification was not effective in the pre-denitrification configurations, since the average organic nitrogen removal ranged from 29% to 60%. Nitrification was very satisfactory since ammonium concentration was usually lower than 0.5mgNH4–NL−1. Increased acetic acid addition was effective, as it enhanced oxidation activity and denitrification rate. The reduction of the anoxic reactor volume and the abolition of internal recycling resulted in a decrease of denitrification rate. Petrochemical wastewater composition affected the biological processes of ammonification and denitrification. The low denitrification during the nitrification, post-denitrification configuration was attributed to the low organic carbon to total nitrogen ratio of influent wastewater. The doubling of inflow rate did not significantly compromise permeate quality. The MBR demonstrated to safeguard the effluent quality even under sudden and drastic transient conditions. Caustic soda caused inhibition of nitrifiers by 56% and refinery wastewater up to 60%.

Winery wastewater treatment for water reuse purpose: Conventional activated sludge versus membrane bioreactor (MBR): A comparative case study

A comparative study was carried out in order to evaluate the winery wastewater treatment by a MBR pilot plant and compare it to a full-scale conventional activated sludge system. The MBR pilot plant was constructed and operated by Hera-Amasa and continuously fed with real winery wastewater generated in wine-making process in Bodegas Torres facilities (Catalonia, Spain). The influent and effluents were monitored and controlled in order to reach the quality determined by the Spanish legislation as well as the international guidelines and regulations for wastewater reuse and reclamation. After 6months of continuous operations the physico-chemical and microbial parameters of the MBR plant achieved the specifications defined for urban service, agricultural and recreational uses. The MBR plant showed a quite stable and flexible operation during the experiment. A significant correlation between EPSc and permeability confirmed the influence of the hydrophilic fraction on the membrane fouling potential.

Comparison of a conventional municipal plant, and an MBR plant with and without MPE: A comparison of the environmental and financial performance of a conventional activated sludge (CAS) plant, membrane bio-reactor (MBR), and MBR treated with Nalco Membrane Performance Enhancer (MPE technology, in the treatment of municipal wastewater

Wastewater treatment using submerged membranes has become an industry standard treatment technology over the last 15 years. Initially, membrane bio-reactor (MBR) plants were often built in regions with the highest effluent quality requirements or in areas of water scarcity. MBR systems have increasingly gained acceptance as one of the best wastewater treatment technologies available. Globally, MBR technology is the fastest growing wastewater treatment technology available, with an annual growth rate (depending upon the country) of between 10 and 20%.

Operational experience with a seasonally operated full-scale membrane bioreactor plant

A seasonally operated full-scale membrane bioreactor plant (flat sheet, 0.03μm) treating municipal wastewater from a recreation facility was monitored for 2years. In particular, membrane bioreactor operation characteristics and development and changes in extracellular polymeric substances and soluble microbial product concentrations were observed, which were both dependent on volume and quality of incoming wastewater. Microbiological effluent quality, nutrient removal efficiency and activated sludge characteristics were analysed on a regular basis. Correlations between activated sludge quality, extracellular polymeric substance and soluble microbial product concentrations were identified. Pathogen related changes in effluent quality during plant operation were also observed. Nutrient removal efficiency was very good, despite fluctuations in influent flow.

Characterization of soluble microbial products in 10 large-scale membrane bioreactors for municipal wastewater treatment in China

In order to fill the knowledge gaps between lab/pilot-scale and full-scale operations and contribute basic information to long-term and stable operation of large-scale membrane bioreactors (MBRs), a systematic investigation was first conducted focused on soluble microbial products (SMPs) in 10 large-scale MBRs (capacity over 10,000 m3/d) for municipal wastewater treatment distributed in 4 different areas of China from fall to winter. The majority of these MBR plants had been operated stably for at least 1 year. Fundamental properties of SMPs were investigated, including composition, molecular weight distribution, hydrophobicity, fluorescent characteristics and fouling potential. The results showed that the concentration of SMPs ranged roughly from 5 to 25 mg TOC/L, with the major component being polysaccharides (ca. 3–18 mg/L) followed by humic substances (ca. 2–10 mg/L); while the protein concentration was relatively low (<5 mg/L). The SMPs presented a broad molecular weight distribution from smaller than 1 kDa to over 100 kDa. About half of the SMPs were hydrophilic substances mainly contributed by polysaccharides; humic substances were concentrated in hydrophobic fractions while proteins showed a relatively wide distribution. The fluorescent properties were found to be affected appreciably by the influent quality. The batch fouling tests indicated that the initial fouling rate correlated significantly with SMPs concentrations, which was particularly the case for hydrophilic and large-molecular-weight fractions. These findings may contribute to better understanding of membrane fouling in engineering conditions and assist in long-term and stable operation of full-scale MBRs.

Comparative effectiveness of membrane bioreactors, conventional secondary treatment, and chlorine and UV disinfection to remove microorganisms from municipal wastewaters

Log removals of bacterial indicators, coliphage, and enteric viruses were studied in three membrane bioreactor (MBR) activated-sludge and two conventional secondary activated-sludge municipal wastewater treatment plants during three recreational seasons (May–Oct.) when disinfection of effluents is required. In total, 73 regular samples were collected from key locations throughout treatment processes: post-preliminary, post-MBR, post-secondary, post-tertiary, and post-disinfection (UV or chlorine). Out of 19 post-preliminary samples, adenovirus by quantitative polymerase chain reaction (qPCR) was detected in all 19, enterovirus by quantitative reverse transcription polymerase chain reaction (qRT-PCR) was detected in 15, and norovirus GI by qRT-PCR was detected in 11. Norovirus GII and Hepatitis A virus were not detected in any samples, and rotavirus was detected in one sample but could not be quantified. Although culturable viruses were found in 12 out of 19 post-preliminary samples, they were not detected in any post-secondary, post-MBR, post-ultraviolet, or post-chlorine samples. Median log removals for all organisms were higher for MBR secondary treatment (3.02 to >6.73) than for conventional secondary (1.53–4.19) treatment. Ultraviolet disinfection after MBR treatment provided little additional log removal of any organism except for somatic coliphage (>2.18), whereas ultraviolet or chlorine disinfection after conventional secondary treatment provided significant log removals (above the analytical variability) of all bacterial indicators (1.18–3.89) and somatic and F-specific coliphage (0.71 and >2.98). Median log removals of adenovirus across disinfection were low in both MBR and conventional secondary plants (no removal detected and 0.24), and few removals of individual samples were near or above the analytical variability of 1.2 log genomic copies per liter. Based on qualitative examinations of plots showing reductions of organisms throughout treatment processes, somatic coliphage may best represent the removal of viruses across secondary treatment in both MBR and conventional secondary plants. F-specific coliphage and Escherichia coli may best represent the removal of viruses across the disinfection process in MBR facilities, but none of the indicators represented the removal of viruses across disinfection in conventional secondary plants.

Control of Membrane Biofouling in MBR for Wastewater Treatment by Quorum Quenching Bacteria Encapsulated in Microporous Membrane

Recently, enzymatic quorum quenching has proven its potential as an innovative approach for biofouling control in the membrane bioreactor (MBR) for advanced wastewater treatment. However, practical issues on the cost and stability of enzymes are yet to be solved, which requires more effective quorum quenching methods. In this study, a novel quorum quenching strategy, interspecies quorum quenching by bacterial cell, was elaborated and proved to be efficient and economically feasible biofouling control in MBR. A recombinant Escherichia coli which producing N-acyl homoserine lactonase or quorum quenching Rhodococcus sp. isolated from a real MBR plant was encapsulated inside the lumen of microporous hollow fiber membrane, respectively. The porous membrane containing these functional bacteria (i.e., "microbial-vessel") was put into the submerged MBR to alleviate biofouling on the surface of filtration membrane. The effect of biofouling inhibition by the microbial-vessel was evaluated over 80 days of MBR operation. Successful control of biofouling in a laboratory scale MBR suggests that the biofouling control through the interspecies quorum quenching could be expanded to the plant scale of MBR and various environmental engineering systems with economic feasibility.

Full‐scale Applications of Membrane Filtration in Municipal Wastewater Treatment Plants

AbstractThe performance of one pilot‐scale and two full‐scale membrane bioreactors (MBR) were evaluated based on the control of main operational parameters, composition of microbial community and pathogens concentration in the treated outlet. Plants were designed for 0.75 m3/day (A), 60 m3/day (B) and 30 m3/day (C). Inlet and outlet samples were monitored for chemical oxygen demand (COD), biological oxygen demand, total suspended solids, ammonia nitrogen concentration (NH4–N), nitrate nitrogen concentration, total Kjeldahl nitrogen, total phosphorus and phosphate phosphorus concentration concentrations. Plants showed good COD removal: 91.9% for Plant A, 97.8% for Plant B and 94.2% for Plant C. The targeted nitrogenous ion was NH4–N due to the requirements for outlet limits. NH4–N removal was moderate for Plant A (73.3%) and Plant B (86.1%) and excellent for Plant C (&gt;99%). Excellent phosphorus removal was achieved by Plant A (average outlet concentration was 0.7 mg/L, efficiency 84.7%). Unsatisfactory results for phosphorus removal were achieved at the full‐scale plants due to operational problems. The dependency between the extracellular polymeric substances increase and decreasing mixed liquor volatile suspended solids for both lab and full‐scale plants was confirmed. Soluble microbial product concentrations were reduced by 65–68% after coagulant dosage for Plant A. Outlets from the MBR plants were monitored for the presence of pathogens (thermotolerant coliforms, Escherichia coli, intestinal Enterococci and culturable microorganisms at 22 and 37°C). The treated effluent from Plant A, B and C met Czech national legislation regarding reuse criteria (standards) for environment, irrigation and swimming purposes. Plants B and C were not able to achieve requirements for potable water and personal hygiene quality standards.

Comparison of phenomenological membrane bioreactor activated sludge biological models with alternative versions based on time series input-output approaches

Data was taken from a full scale sidestream membrane bioreactor (MBR) plant that has been treating industrial wash water from a salad processing factory based in Worcestershire. Various online and offline measurements were taken during an intensive sampling period for the complete flow train. Offline tests included measuring extra-cellular polymeric substance (EPS) and soluble microbial product (SMP) levels in the sludge water which are the main foulants on the associated membrane [1]. Two modified phenomenological Activated Sludge models based upon the ASM1 and ASM3 that included EPS/SMP concentrations were calibrated and validated using these offline and online measurements [2–6]. In order to see whether a simpler model structure could be formulated for advanced control purposes that was based wholly upon measured historical data sets, further conceptual models were developed based on system identification procedures and input-output times series analysis methods [7]. These model forms utilised autoregr...

Removal of endocrine disrupting chemicals in a large scale membrane bioreactor plant combined with anaerobic-anoxic-oxic process for municipal wastewater reclamation

The removal of eight typical endocrine disrupting compounds (EDCs) in a full scale membrane bioreactor combined with anaerobic-anoxic-oxic process (A(2)/O-MBR) for municipal wastewater reclamation located in Beijing was investigated. These EDCs, including 4-octylphenol (4-OP), 4-n-nonylphenol (4-n-NP), bisphenol A (BPA), estrone (E1), 17α-estradiol (17α-E2), 17β-estradiol (17β-E2), estriol (E3) and 17α-ethinylestradiol (EE2), were simultaneously analyzed by gas chromatography/mass spectrometry after derivatization. The concentrations of eight EDCs were also measured in sludge of anaerobic, anoxic, oxic and membrane tanks to measure sludge-water distribution coefficients (K(d) values) as the indicator of adsorption propensity of target compound to sludge. The removal efficiencies of EDCs reached above 97%, except for 4-n-NP removal efficiency of 72%, 4-OP removal efficiency of 75% and EE2 removal efficiency of 87% in the A(2)/O-MBR process. The high K(d) values indicated that the sludge had a large adsorption capacity for these EDCs, and significantly contributed to removal of EDCs. Yeast estrogen screen assay was performed on samples to assess the total estrogenic activity by measuring the 17β-E2 equivalent quantity (EEQ), expressed in ng-EEQ/L. The measured EEQ value was markedly reduced from 72.1 ng-EEQ/L in the influent to 4.9 ng-EEQ/L in the effluent. Anoxic tank and anaerobic tank contributed to 80% and 37% in total EEQ removal, respectively.

Monitoring the variations of the oxygen transfer rate in a full scale membrane bioreactor using daily mass balances

Oxygen transfer in biological wastewater treatment processes with high sludge concentration, such as membrane bioreactor (MBR), is an important issue. The variation of alpha-factor versus mixed liquor suspended solids (MLSS) concentration was investigated in a full scale MBR plant under process conditions, using mass balances. Exhaustive data from the Supervisory Control And Data Acquisition (SCADA) and from additional online sensors (COD, DO, MLSS) were used to calculate the daily oxygen consumption (OC) using a non-steady state mass balance for COD and total N on a 24-h basis. To close the oxygen balance, OC has to match the total oxygen transfer rate (OTRtot) of the system, which is provided by fine bubble (FB) diffusers in the aeration tank and coarse bubbles (CB) in separate membrane tanks. First assessing OTR(CB) then closing the balance OC = OTRtot allowed to calculate OTR(FB) and to fit an exponential relationship between OTR(FB) and MLSS. A comparison of the alpha-factor obtained by this balance method and by direct measurements with the off-gas method on the same plant is presented and discussed.

Online monitoring of membrane fouling in submerged MBRs

Membrane fouling is the most serious problem affecting membrane bioreactors (MBR). It decreases membrane permeability and consequently increases energy consumption. Various methods and techniques to measure fouling rates (FR) can be found in the literature, but few provide online data, and most are expensive or too invasive. The aim of this short communication is to present a new online method for monitoring and estimating the fouling in an MBR, based on the use of the derivative of the transmembrane pressure (TMP) per cycle, for which hourly and daily mean values can be obtained. This online method (FR per cycle) was experimentally evaluated at a lab-scale MBR plant, where fouling conditions were induced by the addition of a protein (albumin) and a polysaccharide (glucose). Finally, we compared the new method to standard methods, such as the flux-step method. Similar results for fouling rates were found, but the new method showed increased sensitivity. At the same time, the method seems to be useful in characterizing the nature of fouling.

Determination of MBR fouling and chemical cleaning interval using statistical methods applied on dynamic index data

Membrane fouling is a serious problem in membrane bioreactor (MBR) processes which limits the widespread application of MBRs. Therefore, importance of prediction of MBR fouling and determination of membrane chemical cleaning interval has been increased in recent years. In this study, procedures for (1) prediction of MBR fouling using dynamic index data obtained by recursive least squares (RLS) method and (2) determination of membrane chemical cleaning interval using statistical quality control (SQC) methods applied on the dynamic index data are proposed. Traditional techniques to determine the membrane chemical cleaning interval cannot capture the dynamics of membrane filtration and fouling as there are developed based on steady-state assumption of MBRs. The newly proposed methods based on the recursive least-squares (RLS) and SQC are expected to overcome the limitations posed by traditional techniques, since these techniques can capture the dynamics of MBR filtration. Proposed methods have been tested with the data obtained from pilot-scale MBR plant. In this study, intercept ( b) and coefficient ( κ) of the traditional fouling model are updated using RLS method with respect to the MBR operational time, and are proposed as new indexes for determining membrane chemical-cleaning interval.