Membrane Bioreactor Wastewater Research Articles

Phytoremediation capability of Anabaena sp. for high organic and chromium-loaded wastewater in membrane bioreactors.

The efficiency of Anabaena sp. was analyzed for the phytoremediation of wastewater loaded with organic matter and heavy metals like chromium. Simulated wastewater was contaminated with chromium. A side-stream membrane bioreactor was used for the treatment of wastewater. A feed tank of 20 L capacity was used with a stirring arrangement. A ceramic microfiltration membrane composed of clay and alumina was obtained from Johnson & Johnson. The removal efficiency of chemical oxygen demand, biochemical oxygen demand, and chromium was evaluated. The process was used for algae harvesting and wastewater treatment. About 92% of chemical oxygen demand (COD), 98% chromium, and oil and grease were completely removed. Membrane fouling was explained by the pore blocking and cake resistance model. Stress in algal cells was determined from the superoxide dismutase (SOD) and catalase (CAT) analysis. The lipid content of algal cells was measured.

Enhancing removal of pollutants from pharmaceutical wastewater using ferrites in Membrane Bioreactor: A promising technology for environmental sustainability

Industrial wastewater contains various toxic and hazardous pollutants that require effective treatment to meet environmental regulations. In recent years, silver-doped ferrites have gained attention as promising materials for the treatment of industrial wastewater in membrane bioreactor (MBR). In this abstract, we will discuss the potential of silver-doped nickel ferrite (AgNiFe2O4) and silver-doped potassium ferrite (AgKFe2O4) was synthesized by sol-gel technique for the removal of pollutants from industrial wastewater. AgNiFe2O4 and AgKFe2O4 nanoparticles have been found to be effective for the removal of various pollutants, including heavy metals, organic compounds, and dyes, from industrial wastewater. Several studies have reported the successful application of silver-doped ferrites for the treatment of industrial wastewater. X-ray diffraction (XRD) pattern reveals the single phase cubic spinel structure with space group Fd-3m and Scanning electron microscope (SEM) confirmed the surface morphology of the synthesized nanoferrites. The use of AgNiFe2O4 and AgKFe2O4 has been found to significantly reduce the concentration of pollutants in wastewater, making it suitable for safe discharge into the environment. Furthermore, the regeneration of silver-doped ferrites has been found to be simple and cost-effective, making them an attractive alternative to conventional wastewater treatment methods. In conclusion, silver-doped nickel ferrite and silver-doped potassium ferrite have shown great potential for the treatment of pharmaceutical wastewater in MBR technique and ferrite materials make them promising candidates for future wastewater treatment technologies.

Hastane Atıksularının Membran Biyoreaktör’de (MBR) Farklı İşletme Koşullarında Arıtımının Yaşam Döngüsü Etki Analizi ile Karşılaştırılması

Bu çalışmada, tam aerobik ve düşük oksijen konsantrasyonlarında eş zamanlı nitrifikasyon-denitrifikasyon (SND) koşullarında, hastane atıksularını arıtan MBR sisteminin çevresel etkileri Yaşam Döngüsü Etki Analizi (YDEA) ile araştırılmıştır. Çalışma sonucunda, her iki koşulda da en yüksek çevresel etki tuzlusu ötrofikasyonunda gerçekleşmiştir. Tam aerobik koşullardan SND şartlarına geçildiğinde tatlısu ve tuzlusu ötrofikasyonu için çevresel etkide sırasıyla %30 ve %31 azalma tespit edilmiştir. Enerji tüketiminde %25 azalma gözlenirken, SND şartlarında reaktörden kaynaklanan hava emisyonlarından dolayı küresel ısınma etkisinde %13 artış olabileceği tespit edilmiştir. Tüm etki kategorileri birlikte değerlendirildiğinde, tam aerobik koşullardan SND şartlarına geçişte çevresel etkilerde %30 azalma olacağı tahmin edilmiştir.

Machine learning reveals the complex ecological interplay of microbiome in a full-scale membrane bioreactor wastewater treatment plant

Membrane bioreactor (MBR) systems are one of the most widely used wastewater treatment processes for various municipal and industrial waste streams. The present study aimed to advance the understanding of ecologically important keystone taxa that play an important role in full-scale MBR systems. A machine-learning (ML) modeling framework based on microbiome data was developed to successfully predict, with an average accuracy of >91.6%, the operational characteristics of three representative full-scale wastewater systems: an MBR, a conventional activated sludge system, and a sequencing batch reactor. ML-based feature-importance analysis identified Ferruginibacter as a keystone organism in the MBR system. The phylogeny and known ecophysiology of members of Ferruginibacter supported their role in metabolizing complex organic polymers (e.g., extracellular polymeric substances) in MBR systems characterized by high concentrations of mixed liquor suspended solids and a high solid retention time. ML regression modeling also revealed temporal patterns of Ferruginibacter in response to water temperature. ML modeling was thus successfully employed in the present study to investigate complex/non-linear relationships between keystone taxa and environmental conditions that cannot be detected using conventional approaches. Overall, our microbiome-data-enabled ML modeling approach represents a methodological advance for identifying keystone taxa and their complex ecological interactions, which has implications for the sustainable and predictive management of MBR systems.

ОСОБЛИВОСТІ СПУХАННЯ АКТИВНОГО МУЛУ В МЕМБРАННИХ БІОРЕАКТОРАХ

Membrane bioreactor (MBR) technology, the practical application of which is growing steadily, is a combination of classical technology of biological treatment with activated sludge with a membrane system of micro- or ultrafiltration. MBR are an alternative to the widely used method of separating activated sludge from wastewater in secondary settling tanks used in traditional biological treatment systems. MBR exclude large-scale negative consequences, as in system with traditional aeration tanks and secondary settling tanks in the "swelling of activated sludge". But "swelling of activated sludge" can affect the nitrification process and minimize the efficiency of ammonium nitrogen removal. The purpose of the work is to study the swelling of activated sludge swelling on the existing membrane bioreactor. The research was carried out by hydrochemical analysis of wastewater in MBR and determination of technological properties of activated sludge in the bioreactor. The negative effect of activated sludge swelling in MBR on nitrification activity in the system was established, which caused a decrease in the efficiency of ammonium nitrogen removal. Filamentous bacteria were identified according to the classification of D. Eickelbum, which caused swelling of activated sludge in the studied MBR, Type 021N.

Characteristics of a novel heterotrophic nitrification and aerobic denitrification bacterium and its bioaugmentation performance in a membrane bioreactor

A novel bacteria with heterotrophic nitrification and aerobic denitrification ability was obtained from a membrane bioreactor (MBR) and identified as Acinetobacter sp. TSH1. The nitrogen removal characteristics, nitrogen balance analysis, kinetic characteristics, and enhanced biological treatment in MBR of the novel isolated strain TSH1 were determined. Results showed that strain TSH1 could remove approximately 96.6% of NH4+-N, 82.9% of NO2−-N and 98.7% of NO3−-N in 24 h, and the corresponding maximum removal rates were 3.64 mg-N/(L·h), 1.77 mg-N/(L·h) and 3.94 mg-N/(L·h). The nitrogen balance analysis indicated that most of NH4+-N (62.6%) and NO3−-N (71.9%) were transformed to gaseous nitrogen. The kinetic experiments showed that strain TSH1 had a high Km of 151.64 mg-NH4+-N/L and 203.25 mg-NO3--N/L. The enhanced biological treatment of synthetic wastewater in MBR showed that the strain TSH1 can significantly improve the nitrogen removal efficiency.

The Removal of Selected Inorganics from Municipal Membrane Bioreactor Wastewater Using UF/NF/RO Membranes for Water Reuse Application: A Pilot-Scale Study.

Membrane technology has advanced substantially as a preferred choice for the exclusion of widespread pollutants for reclaiming water from various treatment effluent. Currently, little information is available about Ultrafiltration (UF)/Nanofiltration (NF)/Reverse Osmosis (RO) performance at a pilot scale as a practical engineering application. In this study, the effluent from a full-scale membrane bioreactor (MBR) municipal wastewater treatment works (MWWTWs) was treated with an RO pilot plant. The aim was to evaluate the effect of operating conditions in the removal of selected inorganics as a potential indirect water reuse application. The influent pH, flux, and membrane recovery were the operating conditions varied to measure its influence on the rejection rate. MBR/RO exhibited excellent removal rates (>90%) for all selected inorganics and met the standard requirements for reuse in cooling and irrigation system applications. The UF and NF reduction of inorganics was shown to be limited to meet water standards for some of the reuse applications due to the high Electron Conductivity (EC > 250 μS·cm−1) levels. The MBR/NF was irrigation and cooling system compliant, while for the MBR/UF, only the cooling system was compliant.

Onsite Non-potable Reuse for Large Buildings: Environmental and Economic Suitability as a Function of Building Characteristics and Location

Onsite non-potable reuse (NPR) is a way for buildings to conserve water using onsite sources for uses like toilet flushing, laundry and irrigation. Although early case study results are promising, aspects like system suitability, cost and environmental performance remain difficult to quantify and compare across broad geographic contexts and variable system configurations. In this study, we evaluate four NPR system types – rainwater harvesting (RWH), air-conditioning condensate harvesting (ACH), and source-separated graywater and mixed wastewater membrane bioreactors (GWMBR, WWMBR) – in terms of their ability to satisfy onsite non-potable demand, their environmental impacts and their economic cost. As part of the analysis, we developed the Non-potable Environmental and Economic Water Reuse Calculator (NEWR), a publicly available U.S. EPA web application that allows users to generate planning-level estimates of system cost and environmental performance using location and basic building characteristics as inputs. By running NEWR for a range of scenarios, we find that, across the U.S., rainfall and air-conditioner condensate are only able to satisfy a fraction of the non-potable demand typical of large buildings even under favorable climate conditions. Environmental impacts of RWH and ACH systems depend on local climate and were comparable to the ones of MBR systems where annual rainfall exceeds approximately 10 in/yr or annual condensate potential exceeds approximately 3 gal/cfm. MBR systems can meet all non-potable demands but their environmental impacts depend more on the composition of the local energy grid, owing to their greater reliance on electricity inputs. Incorporation of thermal recovery to offset building hot water heating requirements amplifies the influence of the local grid mix on environmental impacts, with mixed results depending on grid composition and whether thermal recovery offsets natural gas or electricity consumption. Additional environmental benefits are realized when NPR systems are implemented in water scarce regions with diverse topography and regions relying on groundwater sources, which increases the benefits of reducing reliance on centralized drinking water services. In terms of cost, WWMBRs were found to have the lowest cost under the largest range of building characteristics and locations, achieving cost parity with local drinking water rates when those rates were more than $7 per 1000 gallons, which occurred in 19% of surveyed cities.

Integrated powdered activated carbon and quorum quenching strategy for biofouling control in industrial wastewater membrane bioreactor

Microbial quorum quenching (QQ) has been shown as a promising technology for biofouling control in membrane bioreactors (MBRs). However, QQ technology has never been applied in the industrial wastewater MBR due to the complex water properties. In this study, a type of novel alginate (polyvinyl alcohol)-powdered activated carbon-quorum quenching bacteria beads (APQ beads) was introduced, and the anti-biofouling potential was investigated in an MBR treating semi-conductor wastewater (rich in ethanolamine and diethylene glycol butyl ether). The results show that APQ strategy could significantly alleviate MBR biofouling by extending 4.5 times operating period as compared to the Control-MBR (R1) without APQ beads. The APQ strategy effectively reduced the extracellular polymeric substance (EPS) content and N-acyl homoserine lactones (AHL) concentration in biocake. EPS concentration was reduced by 33.8% and AHLs almost disappeared, probably retarded the adhesion rate of biofilm on the membrane surface, thus displayed a high biofouling mitigation potential. With APQ addition, cake layer membrane resistance was also greatly reduced by 37.22% compared to that of Control-MBR (R1). The QQ activity batch tests confirmed that the used APQ beads still displayed a high AHL-degrading activity and can be employed for long-term operation.

Biodegradation of Evercion Blue P-GR and Ostazin Black H-GRN in synthetic textile wastewater by membrane bioreactor system using Trametes versicolor

In this study, the decolorization of Evercion Blue P-GR (EBP) and Ostazin Black H-GRN (OBH) was investigated using white-rot fungi named as Trametes versicolor (T. versicolor) by Membrane Bioreactor (MBR) system. This study involved experiments employing synthetic textile wastewater in Membrane Bioreactor (MBR) system (170 ml), initially inoculated with a pure culture of fungi, but operated, other than controlling pH (4.5±0.2) and temperature (25±1oC), under non-sterile conditions. The effect of dye concentrations on fungal biodegradation was also investigated. The decolorization efficiencies were 98%, 90%, and 87% respectively, for EBP when the initial dye concentration of 50, 100, and 200 mg L-1 were used. However, the decolorization percentages for OBH dye were obtained 95% for 50 mg L-1 dye solution in 2 days and 66% for 100 mg L-1 dye solution in 5 days. Possible interactions between dye molecules and the fungal surface were confirmed by SEM, EDX, and FTIR analyses.

Relationship between fluorescence excitation-emission matrix properties and the relative degree of DOM hydrophobicity in wastewater treatment effluents

Excitation-emission matrix (EEM) fluorescence spectroscopy is a powerful tool for the characterization of dissolved organic matter (DOM) in wastewater systems. It is of particular value if its utility could be extended by connecting the spectral features to hydrophobicity, one of the fundamental physicochemical properties of DOM. In this study, we employed a DAX-8 resin column to fractionate the hydrophobic/philic components of DOM and determine the relative degree of hydrophobicity by adjusting the critical retention factor (k’cr, the ratio of treated water sample volume to column volume). A higher k’cr would result in a higher hydrophobicity of the column effluent. At different k’cr values (5, 10, 25, 50, 100, and 200), the EEM characteristics of the obtained DOM components were inspected, including overall properties (average fluorescence per total organic carbon and UV absorbance), regional properties (fluorescence regional integration (FRI) and its secondary parameters), and energy-related properties (energy level of the excited states, Stokes shift for relaxation of the excited states, and fluorescence lifetime). In case studies of a wastewater membrane bioreactor and an oxidation ditch, plenty of the EEM properties varied significantly with logk’cr (r > 0.9, p < 0.05). The average fluorescence per UV absorbance (reflecting quantum yield), fluorescence proportion at Stokes shift ≥ 1.1 μm−1, and some secondary FRI parameters presented the best linear fitting with logk’cr, suggesting a smooth variation of the π-conjugated structures with the relative degree of DOM hydrophobicity. This may help to further understand the relationship between EEM fingerprints and DOM hydrophobicity.

Co-Treatment of Municipal Landfill Leachate with Dairy Wastewater in Membrane Bioreactor

Abstract The aim of the study was to determine the effectiveness of leachates from municipal landfill co-treatment with the dairy wastewater in an aerobic membrane bioreactor. It was working in MSBR (sequential membrane bioreactor) systems twice daily and was equipped with the immersed membrane module installed inside what enabled its back-washing performance. The system was working. The concentration of activated sludge in the membrane bioreactor was equal to 4.0 g/dm3. However, the sludge load was at the level of 0.06 g COD/(g d.m. · d). The oxygen concentration was at the level of 3.0 g O2/m3. The share of leachate was varied in a range of 5 to 15 % vol. The evaluation of the effectiveness of the treatment process was based on the change of parameters characterizing the crude sewage and treated sewage. All analysis was carried out according to standards. Following parameters were determined: COD, BOD5, TOC and concentrations of phosphate phosphorus, total nitrogen and ammonium nitrogen. Chemical analysis is often not enough to define the degree of wastewater treatment. It was used toxicological research to determine the effect on the environment. Toxicity of wastewaters was measured using biotests with Vibrio fischeri and Daphnia magna. The results revealed that the volume of leachate in the treated mixture should not exceed 10 % vol. The following conclusion can be drawn from the present research - co-treated wastewater was not toxic. Landfill co-treatment with the dairy wastewater impacts on the effectiveness of biological wastewater treatment. Leachate includes substances which have low susceptibility to biodegradation; on the other hand, dairy wastewaters provide a lot of organic compounds, which can help to treat them.

Fate of antibiotics, antibiotic-resistant bacteria, and cell-free antibiotic-resistant genes in full-scale membrane bioreactor wastewater treatment plants

The removal of antibiotics, antibiotic-resistant bacteria (ARB), and cell-free antibiotic-resistant genes (ARGs) and the microbial community of ARB were investigated in detail to understand their fate and provide valuable information on the feasibility of full-scale membrane bioreactor (MBR). The potential risks of cell-free ARGs to the receiving environment were discovered. High influent antibiotic concentration could inhibit the microbial activity of MBR sludge, whereas good antibiotic removal could be maintained because of relatively long solid retention time and high biomass retention. Approximately 61.8%–77.5% of the total antibiotics were degraded, and 22.5%–38.2% of the total antibiotics were adsorbed by MBR sludge on average. The individual antibiotic removal presented intense discrepancy because of the chemical construction and distribution coefficient of antibiotics. Aeromonas exhibited specific antibiotic resistance to ampicillin and erythromycin, Escherichia became the predominant genera in kanamycin-ARB and tetracycline-ARB, and Klebsiella and Bacteroides were the particular genera that exhibited distinct antibiotic resistance to ciprofloxacin. A significant correlation was found between cell-free ARG abundance and ARB content, and relatively high effluent cell-free ARG abundance facilitated the proliferation and transmission of ARB. The impacts of the receiving environment to eliminate the ecological risks and severe threats to human health should be investigated because of the low decay ratio and long-term persistence of cell-free ARGs.

Effects of carrier addition on water quality and pharmaceutical removal capacity of a membrane bioreactor – Advanced oxidation process combined treatment

This research was performed to assess the production of reclaimed water from urban wastewater in membrane bioreactor – advanced oxidation process (MBR-AOP) and moving bed biofilm reactor – membrane bioreactor – advanced oxidation process (MBBR-MBR-AOP) combined treatments to study the effect of biofilm incorporation. Both combined treatments were operated at the same conditions (10 h of hydraulic retention time, 6500 mg/L of mixed liquor suspended solids and 25 mg/L of hydrogen peroxide dosage over 15 min). Additionally, the removal capacity of some pharmaceuticals (carbamazepine, ciprofloxacin and ibuprofen) and their impact on the kinetic behaviour of the biomass in both systems were evaluated. From the results, it was found a membrane-based bioreactor can achieve both wastewater secondary treatment and pre-treatment for advanced oxidation process, so both MBR-AOP and MBBR-MBR-AOP treatments have a great potential to produce high quality reclaimed water (biological oxygen demand <0.5 mgO2/L, suspended solids <1 mg/L, turbidity <1 NTU and no presence of E. coli), according to European Commission proposal 2018/0169/COD. The addition of carriers improved the biodegradation of the most persistent pharmaceuticals in the biological treatment (from 69.20 ± 1.54% to 75.14 ± 2.71% for carbamazepine and from 60.41 ± 2.16 to 63.14 ± 2.70% for ciprofloxacin). It had, as a consequence, the MBBR-MBR-AOP system showing a complete degradation of pharmaceuticals after 5 min AOP treatment compared to the MBR-AOP system. The loss of biomass in the MBR-AOP (from 5233.45 to 4451.92 mg/L) and the increase of the substrate degradation rate for organic matter in both treatments (from 37.27 to 41.42 and from 30.25 to 33.19 mgO2/(L·h) in MBR-AOP and MBBR-MBR-AOP, respectively) are some of the consequences of pharmaceuticals in urban wastewater.

Removal and transformation pathways of benzothiazole and benzotriazole in membrane bioreactors treating synthetic municipal wastewater

Lab-scale membrane bioreactors (MBRs), with aerated activated sludge and internal microfiltration module, were used for the treatment of municipal wastewater containing high, yet environmentally relevant, concentrations of benzothiazole (BT) and benzotriazole (BTA). These high production volume compounds are commonly used in the industry and households, and therefore occur ubiquitously in municipal wastewater and the aquatic environment. The aim of this study was to assess the removal of BT and BTA from synthetic municipal wastewater in MBRs and to estimate the contribution of elimination processes and to identify potential biotransformation products. The overall removal of BT and BTA was high, and after the adaptation period, it reached 99.8% and 97.2%, respectively, but recurring periods of unstable BTA removal occurred. The removal due to biotransformation was 88% for BT and 84% for BTA and the disposal with waste sludge accounted for only <1% of the removed load. The remaining fraction of the removed load of BT and BTA was attributed to be retained by phenomena associated with membrane fouling. The adaptation process was reflected in multifold increase in biodegradation kinetic coefficient (kbiol) for BT (reported for the first time) and BTA. Biodegradation was attributed to catabolic mechanism rather than to cometabolism. Hydroxylation was observed to be the main transformation reaction for BT, whereas for BTA hydroxylation, methylation and cleavage of benzene ring were noted. This study has shown the feasibility of treating municipal wastewater with high concentrations of BT and BTA in MBRs and identified potential challenges for the removal of BTA.

Zeolite Ion Exchange to Facilitate Anaerobic Membrane Bioreactor Wastewater Nitrogen Recovery and Reuse for Lettuce Fertigation in Vertical Hydroponic Systems

Abstract Ammonia-nitrogen recovered from synthetic anaerobic membrane bioreactor (AnMBR) permeate facilitated by natural zeolite (clinoptilolite) ion exchange was released during regeneration with ...

Calibration and validation of an activated sludge model for membrane bioreactor wastewater treatment plants

ABSTRACTA mathematical model to simulate the biological processes occurring in a membrane bioreactor (MBR) is presented. The model accounts for different MBR technical features by introducing specific permeability parameters for the applied membrane system. The model considers for the heterotrophic storage process and the formation of soluble microbial products. The introduction of an inhibition coefficient influencing the anoxic kinetics enables the model to simulate the particular operating conditions of the plant, such as a high or low dissolved oxygen concentration in the denitrification tank. The model was applied at the MBR wastewater treatment plant of Vila Nova do Ceira (Portugal) which uses a classic pre-denitrification cycle. Data for calibration and validation were sampled at the same wastewater treatment plant. Calibration was achieved by varying the kinetic parameters of the model to match the simulation results to the experimental data. The values of the kinetic parameters were similar to those found in the literature. The validation was performed by two different methodologies to analyse the model response to diverse operating conditions, and to evaluate the resilience of the MBR. Calibration and validation results were evaluated with mean average error, root mean square error and fractional mean bias as performance indexes. In most cases, these indexes confirmed the high accuracy of the model. Overall, the results of the calibration and validation steps enriched the proposed model by providing an effective biological description of the processes characterizing the MBR. Thus, the model is a reliable tool for the management and designing of MBR.

Performance of a submerged membrane bioreactor for wastewater mimicking fish meal processing effluent

The objective of this work was to analyze organic matter removal, nitrification, biomass growth and membrane fouling in a submerged flat-sheet membrane bioreactor, fed with synthetic wastewater, of similar composition to the effluents generated in a fish meal industry. After biomass acclimatization with saline conditions of 12 gNaCl/L and COD/N ratio of 15 in the bioreactor, results showed that the organic matter removal was higher than 90%, for all organic loading rates (0.8, 1, 1.33 and 2 gCOD/L∙d) and nitrogen loading rates (0.053, 0.067, 0.089 and 0.133 gN/L∙d) tested during the study. However, nitrification was only carried out with the lowest OLR (0.8 gCOD/L∙d) and NLR (0.053 gN/L∙d). An excessive concentration of organic matter in the wastewater appears as a limiting factor to this process\'operating conditions, where nitrification values of 65% were reached, including nitrogen assimilation to produce biomass. The analysis of membrane fouling showed that the bio-cake formation at the membrane surface is the most impacting mechanism responsible of this phenomenon and it was demonstrated that organic and nitrogen loading rates variations affected membrane fouling rate.

Energy analysis and optimization of hollow fiber membrane contactors for recovery of dissolve methane from anaerobic membrane bioreactor effluent

This work presents an energy analysis and optimization of the hollow fiber membrane contactors for the recovery of dissolved methane (CH4) in effluents of anaerobic membrane bioreactor wastewater treatment processes. The obtained CH4 could be merged with biogas for further purification or used with a micro-turbine for electricity generation to achieve an energy self-sufficient wastewater treatment process. A mathematical model considering simultaneous CH4 and carbon dioxide (CO2) desorption was used to estimate the membrane area required to remove the dissolved CH4, as well as quality of the outlet gas from the membrane contactor. Energy balance between electrical energy obtained from the recovered CH4 and energies consumed by vacuum and liquid pumps for the operation of membrane contactor were investigated and reported as a Net Electricity obtained per m3 of effluent or simply Net E. Results revealed that a combination of a high strip gas flow rate and slightly low vacuum condition closed to the atmospheric pressure can provide the highest Net E at 0.178 MJ/m3. This value is 85.37% of the total electrical energy that can generated from a 90% recovery of dissolved CH4 using an effluent saturated with a 60 vol% CH4 biogas and flow rate at 2 m3/day. The calculation was made based on the assumptions that 1) the membrane contactor is operated in a non-wetting mode where membrane properties remain constant, 2) flux decline due to the membrane fouling is not considered and 3) the energy required for membrane cleaning and other relevant activities are not factored into the energy analysis. Based on our results, to obtain a high CH4 mole fraction at the gas outlet, a low strip gas flow rate is recommended, however, the operating gas pressure needs to be lowered by applying a vacuum condition to improve the Net E. In addition, it was found that the Net E could be improved by increasing the number of membrane fibers, and lowering the liquid flow rate. The CH4 recovery efficiency could also be optimized to obtain an optimal Net E.

Application of monochloramine for wastewater reuse: Effect on biostability during transport and biofouling in RO membranes

The rising demand for clean and safe water has increased the interest in advanced wastewater treatment and reuse. Reverse osmosis (RO) can provide reliable and high-quality water from treated wastewater. Biofouling inevitably occurs, certainly with wastewater effluents, resulting in RO performance decline and operational problems. Chlorination of feed water has been commonly applied to limit biological growth. However, chlorine use may lead to a loss of membrane integrity of RO systems. In this study the potential of monochloramine as an alternative for chlorine was studied by (i) evaluating the biological stability of a full-scale wastewater membrane bioreactor (MBR) effluent during transport over 13 km to a full-scale RO plant and (ii) assessing the biofouling control potential in membrane fouling simulator (MFS) and pilot-scale RO installation. Microbial water analysis was performed on samples taken at several locations in the full-scale water reuse system (MBR effluent, during transport, and at the RO inlet and outlet) using a suite of tools including heterotrophic plate counts (HPC), adenosine triphosphate (ATP), flow cytometry (FCM), and 16 S rRNA gene pyrosequencing. Growth potential tests were used to evaluate the effect of monochloramine presence and absence on bacterial growth. Results showed limited changes in the microbial water quality in the presence of monochloramine. MFS studies showed that membrane biofouling could be effectively repressed by monochloramine over prolonged time periods. The normalized salt passage in a pilot RO system with monochloramine dosage was constant over a one year period (data of last 130 days presented), demonstrating that no membrane damage occurred. From this study, it can be concluded that monochloramine dosage in wastewater applications is effective in controlling biofouling in RO systems and maintaining a monochloramine residual during water transport provides biologically stable water.