Andrea Achilli

Interests

Teaching

Environmental EngineeringWater and Wastewater TreatmentPhysicochemical ProcessesMass and Heat Transfer

Research

Membrane Processes in Environmental ApplicationsWater and Wastewater TreatmentWater ReuseDesalinationProcess Design and Intensification

Courses

Scholarly Contributions

Books

• Achilli, A. (2016). Pressure retarded osmosis: Applications.

Chapters

• Achilli, A., & Hickenbottom, K. L. (2016). Pressure retarded osmosis. In Sustainable Energy from Salinity Gradients. doi:10.1016/b978-0-08-100312-1.00003-1
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  This chapter presents typical applications and process configurations for both open- and closed-loop pressure retarded osmosis (PRO) systems, summarizing the current state of PRO technology at the pilot and industrial scale, and discussing future perspectives for salinity gradient energy from PRO. The first PRO configuration explored has been river-to-sea water and although this configuration has the potential to be a reliable source of base-load renewable energy, the low-energy density associated with this salinity gradient makes commercialization of PRO in this configuration unlikely. Additional PRO configurations include reverse osmosis (RO)–PRO and osmotic heat engines (OHE). The higher salinity gradient available for power production in RO–PRO systems and energy conversion in OHE is likely to make them a more promising component of an alternative energy portfolio.
• Achilli, A., & Holloway, R. W. (2016). Aerobic Membrane Bioreactor. In Encyclopedia of Membranes. doi:10.1007/978-3-662-44324-8_7
• Achilli, A. (2014). Aerobic Membrane Bioreactor. In Encyclopedia of Membranes. doi:10.1007/978-3-642-40872-4_7-1
• Childress, A. E., Achilli, A., Achilli, A. L., & Hickenbottom, K. L. (2013). Pressure-Retarded Osmosis. In Encyclopedia of Membrane Science and Technology. John Wiley & Sons, Inc. doi:10.1002/9781118522318.EMST082
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  This chapter presents typical applications and process configurations for both open- and closed-loop pressure retarded osmosis (PRO) systems, summarizing the current state of PRO technology at the pilot and industrial scale, and discussing future perspectives for salinity gradient energy from PRO. The first PRO configuration explored has been river-to-sea water and although this configuration has the potential to be a reliable source of base-load renewable energy, the low-energy density associated with this salinity gradient makes commercialization of PRO in this configuration unlikely. Additional PRO configurations include reverse osmosis (RO)–PRO and osmotic heat engines (OHE). The higher salinity gradient available for power production in RO–PRO systems and energy conversion in OHE is likely to make them a more promising component of an alternative energy portfolio.

Journals/Publications

• Alhussaini, M. A., Souza-Chaves, B. M., Felix, V., & Achilli, A. (2025). Tailored divalent-monovalent selectivity of nanofiltration and reverse osmosis membranes through controlled oxidation. Desalination and Water Treatment, 323(Issue). doi:10.1016/j.dwt.2025.101252
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  The implementation of membrane technologies, especially nanofiltration (NF) and reverse osmosis (RO), has proven to be highly effective in water treatment applications where ion rejection is required. Extensive research has been made to demonstrate membranes with high water-solute selectivity. However, the rising need for sustainable and economically efficient processes has led to an increasing interest in solute-solute selectivity for targeted and precise separation applications such as resource recovery and extraction. Expanding beyond the traditional limitations of the permeability-selectivity trade-off contributes to the broader goal of selective separation. In this study, utilizing ultra-filtered treated wastewater, pristine and oxidized NF and RO membrane coupons were used to study the influence of oxidation through chlorination on solute-solute selectivity. The cation and anions monovalent/divalent separation factor initially increased with increasing the chlorine dose for both NF and RO membranes and then decreased when the chlorine dose increased beyond 8 K ppm-h. For monovalent-divalent ions/organics, the separation factor remained relatively consistent for both membranes. Interestingly, both membranes maintained high rejection rates for bulk organics and trace organics up to 10 K ppm-h chlorine dose. The results highlight the opportunities of controlled oxidation for tailoring the solute-solute selectivity.
• Chung, K. J., Albright, A. G., Goad, D. W., Page, A. E., Souza-Chaves, B. M., Achilli, A., Hegetschweiler, M. J., Shulman, L. M., & Betancourt, W. Q. (2025). Influence of virus analytical methods on the estimation of virus reductions by ultrafiltration. Journal of Virological Methods, 338(Issue). doi:10.1016/j.jviromet.2025.115208
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  This study evaluated the influence of analytical methods on the quantitative estimation of viruses in recycled waters and their reductions by an ultrafiltration (UF) engineering-scale system. Adenoviruses, crAssphage, Pepper mild mottle virus (PMMoV), culturable male-specific and somatic coliphages selected through a comparative quantitative analysis were evaluated in UF feed and UF permeate using a combination of analytical methods for virus concentration and absolute quantification of virus genomes and infectious coliphages by digital PCR and plaque assays, respectively. Both methods of virus concentration, centrifugal ultrafiltration and the InnovaPrep CP Select™ Concentrating Pipette (CP), demonstrated similar performance for the recovery of viruses from UF feed and UF permeate, however the CP approach allowed more rapid sample filtration than centrifugal ultrafiltration. Procedures commonly applied for the detection of viruses in water generated different quantitative outcomes that were influenced by the type of virus and other natural sources of variation associated with UF feed and UF permeate water. These quantitative outcomes in virus measurements led to highly variable estimations of virus reductions ranging from no apparent reduction to a maximum of 2-log10. These results indicate that more accurate estimations of virus levels and reductions in water purification processes require adjustments in analytical procedures under the wide variety of water characteristics associated with each stage of treatment. A thorough understanding of the interactions between structural features of natural occurring viruses in recycled waters and water quality characteristics is crucial for improving virus recoveries and for the assessment of membrane-based treatment systems as barriers against microbial targets of environmental and public health concern.
• Presson, L. K., Hegetschweiler, M. J., Felix, V., Shingler, J., Hickenbottom, K. L., & Achilli, A. (2025). Targeted chemical cleaning preserves high water flux and water quality in long-term pilot-scale membrane distillation for potable water reuse. Desalination, 608(Issue). doi:10.1016/j.desal.2025.118839
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  Long-term, continuous operation of membrane distillation (MD) is limited by the lack of knowledge on scaling and wetting resistance. In this study, a pilot-scale vacuum-assisted air gap MD (V-AGMD) system with 25.92 m2 of membrane area is used to purify reclaimed water from a membrane bioreactor. The V-AGMD system produced 600–700 L/day with a 75 % recovery rate of water for approximately three months. A decline in water flux from the initial value of 1.1 LMH was observed and routine chemical cleaning procedures were employed in response. Cleaning with hydrochloric acid (HCl) was effective at recovering water flux, but after one month of weekly acid cleaning, some evidence of fouling and scaling remained. Additional chemical cleaning procedures were tested, including chlorination and the use of chelating agents. Chlorination was ineffective because minimal organic fouling was present, and, without rinsing procedures, generated disinfection byproducts that were detected in the distillate. The chelating agent (Ethylenediaminetetraacetic acid, EDTA) recovered water flux by the removal of gypsum. Despite evidence of membrane scaling, the water quality of the distillate remained high. Rejection of dissolved contaminants temporarily decreased during the second month of operation but was recovered by cleaning with EDTA. The cleaning procedures were also critical in maintaining the energy efficiency of the V-AGMD system as they lowered the channel backpressure and improved the heat recovery after fouling and scaling. This study demonstrates that high water quality and water flux can be maintained in long-term MD operation through chemical cleaning that targets specific foulants and scalants.
• Souza-Chaves, B. M., Alejandri, D. S., Betancourt, W. Q., & Achilli, A. (2025). Total fluorescence as a surrogate for organic carbon measurement: Implications for rapid water and wastewater quality assessment. The Science of the total environment, 999, 180260.
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  This study investigates total fluorescence (TF) as a surrogate for measuring total organic carbon (TOC) and dissolved organic carbon (DOC) in water samples. Three analytical instruments - TOC analyzer, size-exclusion chromatography with organic carbon detector (SEC-OCD), and three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy - are used to analyze samples from various wastewater sources. The research establishes correlations among these methods for determining organic matter concentrations. Results indicate a robust linear relationship between TF and DOC, with a correlation coefficient (R) of 0.997 for DOC concentrations exceeding 0.5 mg/L. However, at concentrations below this threshold, TF tends to underestimate DOC due to sensitivity limitations, which restricts its direct application in ultra-pure or reverse osmosis-treated waters unless appropriately calibrated. Clustering analysis of fluorescence data revealed distinct groupings of samples based on organic content, further supporting the use of TF as an indicator of water quality and treatment efficiency. Rapid fluorescence measurements enable high-throughput analysis with minimal delays, streamlining water quality assessments. Historical data from engineering-scale, demonstration-scale, and full-scale treatment facilities support TF's usefulness as a surrogate for TOC/DOC measurement. The proposed fluorescence method demonstrated greater sensitivity than traditional DOC measurements at specific sites, with a minimum detection limit of approximately 0.05 mg/L for DOC in certain water matrices. For broader applications involving different water sources, TF provides a general indication of organic concentrations, while calibration is needed for high-sensitivity requirements, such as trace organic carbon detection. These findings suggest that TF holds promise for expedited evaluation of water quality, pollution levels, and treatment effectiveness across diverse treatment trains, offering a new tool in water and wastewater treatment practices and enhancing environmental quality management.
• Wilson, A. M., Hasan, M., Jung, Y., Larkin, L., Zhan, Y., Morrison, D., & Achilli, A. (2025). Knowledge gaps and education opportunities on direct potable reuse: Interviews with customers of a large, southwestern United States water utility. The Science of the total environment, 1002, 180603.
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  Water scarcity is a global public health threat that has increased urgency in implementing new sustainable practices to protect water supplies, such as the use of direct potable reuse, or "advanced water purification (AWP)". The study objective was to use interviews to characterize knowledge gaps and community outreach strategies to increase successful AWP implementation in an arid city in the southwestern United States. Through partnership with a water utility in an urbanized area of Arizona, 6000 individuals were emailed for invitation to participate in interviews. Interviews were conducted over Zoom and transcribed verbatim. Transcripts underwent inductive thematic analysis. Twenty-two individuals participated in interviews, and saturation of themes was reached. Five main themes emerged: 1) Conflation of filters with all treatment and the influence of residential technologies, 2) individual-level control over decisions to use advanced purified water, 3) desire for regulation, testing, and transparency about testing results, 4) concerns about specific chemicals, 5) educational resources to strengthen community engagement. Participants expressed lack of knowledge about how water is delivered to their residences by expressing the desire for opting in or out of system-wide treatment approaches. They also expressed wanting more support in interpreting testing results and having access to multiple outreach modalities. There is a growing body of evidence supporting increased outreach from utilities and governmental entities for water reuse adoption. This work provides insights into why the public may be in support or not of AWP and what information they need to form an opinion.
• Wilson, A. M., Jung, Y., Shafae, M., Amoh-Asante, N. A., Ashraf, A., Quon, H., Hamilton, K. A., Morrison, D., Larkin, L., Hickenbottom, K., Sáez, A. E., Ikner, L. A., Betancourt, W., Norwood, R. A., & Achilli, A. (2025).

  Public risk perceptions of advanced water purification in an arid urban region of the U.S. southwest: A mixed methods study

  . The Science of the total environment, 1002, 180558.
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  As water utilities implement potable reuse technology, there is a need to understand how to increase public acceptance and trust in public water supplies. The study objective was to use surveys and interviews in a large metropolitan area in Arizona to characterize tap water and advanced purified water acceptability, and factors contributing to (un)acceptability. Participants were recruited through a water utility email listserv for participation in an online REDCap survey and/or 1-hr Zoom interview. Surveys and interviews inquired about perceptions of tap water safety, familiarity with water reuse terms, acceptability of direct potable reuse (called "advanced water purification" in our study for consistency with state messaging), and rationales related to acceptance. Four hundred seventy-nine individuals participated in the survey, and twenty-two individuals participated in the interviews, with roughly comparable demographics for our city of interest but with slightly higher levels of household income and education. Only 36 % of survey respondents use their tap water for drinking water supplies, but (42 %) would be open to drinking advanced purified water. Semi-structured interviews were conducted in 2024 on risk-based thinking to evaluate how advanced purified water may compare to current drinking water safety and analyzed with inductive thematic analysis. Survey and interview participants wanted more reassurances (e.g., third party testing and opportunities for hands-on testing). Water utilities should prioritize transparent communication strategies, including sharing detailed third-party testing data and direct community engagement initiatives, to enhance public acceptance. Utilities can build trust through clear comparisons between advanced purified water and current tap water quality.
• Wilson, A. M., Jung, Y., Shafae, M., Amoh-Asante, N. A., Ashraf, A., Quon, H., Hamilton, K. A., Morrison, D., Larkin, L., Hickenbottom, K., Sáez, A. E., Ikner, L. A., Betancourt, W., Norwood, R. A., & Achilli, A. (2025). Public risk perceptions of advanced water purification in an arid urban region of the U.S. southwest: A mixed methods study. Science of the Total Environment, 1002(Issue). doi:10.1016/j.scitotenv.2025.180558
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  As water utilities implement potable reuse technology, there is a need to understand how to increase public acceptance and trust in public water supplies. The study objective was to use surveys and interviews in a large metropolitan area in Arizona to characterize tap water and advanced purified water acceptability, and factors contributing to (un)acceptability. Participants were recruited through a water utility email listserv for participation in an online REDCap survey and/or 1-hr Zoom interview. Surveys and interviews inquired about perceptions of tap water safety, familiarity with water reuse terms, acceptability of direct potable reuse (called “advanced water purification” in our study for consistency with state messaging), and rationales related to acceptance. Four hundred seventy-nine individuals participated in the survey, and twenty-two individuals participated in the interviews, with roughly comparable demographics for our city of interest but with slightly higher levels of household income and education. Only 36 % of survey respondents use their tap water for drinking water supplies, but (42 %) would be open to drinking advanced purified water. Semi-structured interviews were conducted in 2024 on risk-based thinking to evaluate how advanced purified water may compare to current drinking water safety and analyzed with inductive thematic analysis. Survey and interview participants wanted more reassurances (e.g., third party testing and opportunities for hands-on testing). Water utilities should prioritize transparent communication strategies, including sharing detailed third-party testing data and direct community engagement initiatives, to enhance public acceptance. Utilities can build trust through clear comparisons between advanced purified water and current tap water quality.
• Alhussaini, M., Souza-Chaves, B., Felix, V., & Achilli, A. (2024). Comparative analysis of reverse osmosis and nanofiltration for the removal of dissolved contaminants in water reuse applications. Desalination, 586. doi:10.1016/j.desal.2024.117822
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  The increasing demand for drinking water has led to the adoption of unconventional water sources, such as water reuse. Reverse osmosis (RO) and nanofiltration (NF) membranes are effective barriers against trace organic contaminants in potable water reuse applications. However, the use of RO is being challenged by NF, primarily due to NF's potential to achieve similar contaminant removal as RO but with higher productivity and lower energy requirements. This study compares NF and RO membranes in terms of contaminant removal and energy consumption for potable water reuse applications. RO (BW30XFR) and dense and loose NF (NF90 and NF270) membranes were tested in bench-scale systems, and RO (TW30) and NF (NF9) membrane elements were tested in an engineering scale system utilizing UF-filtered reclaimed wastewater. The highest solute passage was observed using NF270 membrane. There was no difference between NF90 and BW30XFR in terms of divalent ion passage, but NF90's total organic carbon and monovalent ion passages were higher. Both NF90 and BW30XFR highly rejected negatively charged trace organic contaminants (TOrCs), though rejections were lower for neutral and positively charged compounds. Furthermore, all compounds were highly rejected in the engineering-scale system by NF9 and TW30. These results highlight the potential of dense NF membranes as an energy-efficient barrier for contaminant removal.
• Crosson, C., Pincetl, S., Scruggs, C., Gupta, N., Bhushan, R., Sharvelle, S., Porse, E., Achilli, A., Zuniga-Teran, A., Pierce, G., Boccelli, D. L., Gerba, C. P., Morgan, M., Cath, T. Y., Thomson, B., Baule, S., Glass, S., Gold, M., MacAdam, J., , Cole, L., et al. (2024). Advancing a Net Zero Urban Water Future in the United States Southwest: Governance and Policy Challenges and Future Needs. ACS ES&T Water, 4(5), 1966-1977. doi:10.1021/acsestwater.4c00031
• Malaguti, M., Presson, L., Tiraferri, A., Hickenbottom, K., & Achilli, A. (2024). Productivity, selectivity, and energy consumption of pilot-scale vacuum assisted air-gap membrane distillation for the desalination of high-salinity streams. Desalination, 582. doi:10.1016/j.desal.2024.117511
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  The implementation of air gap membrane distillation systems is limited by a lack of overall performance predictions which rely on few available pilot-scale studies. This study evaluates the productivity, energy consumption, and selectivity of a pilot-scale air gap membrane distillation system by combining experiments and modeling activities. The effect of operating conditions, i.e., applied vacuum, feed flow rate, and feed stream salinity, was investigated to identify regulating factors and quantify dependencies. Response surface methodology was applied to model the phenomena and provide statistical analysis. Increasing flow rates produced a near linear increase of productivity within the investigated range. Operating at higher applied vacuum also translated into enhanced productivity, though the distillate flux increased by a maximum of 10 % when vacuum increased from −100 mbar to −500 mbar. Flow rate and vacuum also governed the observed salt flux by a similar magnitude because salt flux resulted mainly from liquid pore flow phenomena. The trans-membrane pressure regulated the membrane rejection: increasing the pressure difference led to a lower rejection. Moreover, high feed stream salinity lowered both the productivity and the distillate quality. The productivity gains were typically achieved at the expense of an increase in specific thermal energy consumption; however, an interesting relation was observed with feed stream salinity, with a minimum of specific thermal energy consumption of roughly 300kWhth⋅m−3 identified in the treatment of a stream with a salinity of 150g/L.
• Alhussaini, M. A., Binger, Z. M., Souza-Chaves, B. M., Amusat, O. O., Park, J., Bartholomew, T. V., Gunter, D., & Achilli, A. (2023). Analysis of backwash settings to maximize net water production in an engineering-scale ultrafiltration system for water reuse. Journal of Water Process Engineering, 53(Issue). doi:10.1016/j.jwpe.2023.103761
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  Ultrafiltration (UF) has been widely utilized as water pretreatment for different applications especially in water reuse. The UF system operation is characterized by a filtration phase, where particles accumulate on the membrane surface resulting in an increase in the transmembrane pressure (TMP) and a cleaning phase, where foulants are removed through cleaning cycles including physical backwash and chemical-enhanced backwash (CEB). In this study, data from an engineering-scale UF system treating reclaimed wastewater were used to assess the impact of backwashing on the filtration process. TMP backwash trigger, backwash duration, and CEB frequency were purposely varied for a cycle-by-cycle investigation on the net water production, water recovery, initial operating TMP, and filtration cycle duration. As the TMP backwash trigger was varied between 62 and 145 kPa, the maximum net water production (63 m3/d) was achieved at 103 kPa and water recovery remained relatively constant at approximately 92 %. Backwash durations of 45, 65, and 85 s were performed where both net water production and water recovery yielded similar results (~63 m3/d and ~ 91 %) compared with 103 kPa TMP backwash trigger. The CEB frequency was also lowered from one every three backwashes (1/3) to 1/6 and 1/12 and resulted in decreased net water production and water recovery while the initial TMP increased. Interestingly, the total number of CEBs remained approximately constant regardless of their frequency. Results suggest that CEB is an important fouling control process to maximize water production.
• Binger, Z. M., & Achilli, A. (2023). Surrogate modeling of pressure loss & mass transfer in membrane channels via coupling of computational fluid dynamics and machine learning. Desalination, 548(Issue). doi:10.1016/j.desal.2022.116241
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  Spacers are integral to the operation of membrane systems for both structural purposes and improving mass transfer dynamics that drive water permeation at the cost of increased pressure losses. 321 computational fluid dynamics (CFD) simulations were performed to provide high-fidelity data on hydrodynamic and mass transport behavior of spacer-filled membrane channels. CFD simulations were used to investigate the impact of the geometric parameters of spacers on pressure loss and concentration polarization in membrane channels. Spacer designs were characterized using six parameters that were varied in simulations to sample the domain of commercially available designs. Machine learning models were trained on CFD data to produce surrogate models for predicting pressure loss and mass transfer coefficients. These surrogate models consider more geometric parameters than existing empirical equations resulting in more representative and flexible models that can be integrated into existing module-scale or system-scale modeling software. Surrogate models were coupled with a particle swarm optimization algorithm and found that spacer designs with a diameter of 0.3 mm, length of 3.6 mm, angle between 42 and 46°, and moderate diameter necking (~60 %) best balances the trade-off between reduced concentration polarization and increased pressure losses in membrane channels with channel velocities between 0.05 and 0.35 m/s.
• Hardikar, M., Felix, V., Presson, L., Rabe, A., Ikner, L., Hickenbottom, K., & Achilli, A. (2023). Pore flow and solute rejection in pilot-scale air-gap membrane distillation. Journal of Membrane Science, 676. doi:10.1016/j.memsci.2023.121544
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  Membrane distillation (MD) is a desalination technology with promising applications in treating brines generated by reverse osmosis. Theoretically, MD can achieve 100% rejection of non-volatile contaminants such as organic and inorganic solutes and pathogens because only the vapor phase permeates through the membrane. However, polymeric membranes are subject to a wide distribution of pore sizes that may result in pore flow or liquid flux through even a new membrane resulting in poor contaminant rejection. In pilot-scale MD systems, a larger membrane area increases the hydraulic pressure in the flow channel and the transmembrane hydraulic pressure difference, thus increasing the probability of pore flow of non-volatile contaminants through the membrane and providing enhanced resolution of contaminant detection. This work reports membrane rejection of organic and inorganic non-volatile solutes in a pilot-scale air-gap MD (AGMD) element and quantifies, for the first time, transport of non-volatile solutes through the membrane because of pore flow. Pathogen rejection in the pilot-scale MD system was also measured using enteric virus surrogates MS2 and PhiX174 as tracers. Organic and inorganic solutes and both viruses were detected in the distillate, suggesting the presence of pore flow. No difference between organic and inorganic solute rejection was observed, and both decreased (from 2.5-log10 to 1.5-log10) with an increase in air-gap vacuum (from 50 to 500 mbar). At 50 mbar and low evaporator inlet temperature (40 °C), virus rejection (2.4 -log10) was higher than organic and inorganic solute rejection (1.7-log10).
• Hardikar, M., Felix, V., Rabe, A., Ikner, L., Hickenbottom, K., & Achilli, A. (2023). Virus rejection and removal in pilot-scale air-gap membrane distillation. Water Research, 240. doi:10.1016/j.watres.2023.120019
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  Membrane distillation (MD) is a thermally-driven process that can treat high concentration streams and provide a dual barrier for rejection and reduction of pathogens. Thus, MD has potential applications in treating concentrated wastewater brines for enhancing water recovery and potable water reuse. In bench-scale studies, it was demonstrated that MD can provide high rejection of MS2 and PhiX174 bacteriophage viruses, and when operating at temperatures greater than 55 °C, can reduce virus levels in the concentrate. However, bench-scale MD results cannot directly be used to predict pilot-scale contaminant rejection and removal of viruses because of the lower water flux and higher transmembrane hydraulic pressure difference in pilot-scale systems. Thus far, virus rejection and removal have not been quantified in pilot-scale MD systems. In this work, the rejection of MS2 and PhiX174 at low (40 °C) and high (70 °C) inlet temperatures is quantified in a pilot-scale air-gap MD system using tertiary treated wastewater. Both viruses were detected in the distillate which suggests the presence of pore flow; the virus rejection at a hot inlet temperature of 40 °C for MS2 and PhiX174 were 1.6-log10 and 3.1-log10, respectively. At 70 °C, virus concentrations in the brine decreased and were below the detection limit (1 PFU per 100 mL) after 4.5 h, however, viruses were also detected in the distillate in that duration. Results demonstrate that virus rejection is lower in pilot-scale experiments because of increased pore flow that is not captured in bench-scale experiments.
• Achilli, A., Felix, V., Hardikar, M., Hickenbottom, K. L., & Presson, L. (2022). Fouling Characterization and Treatment of Water Reuse Concentrate with Membrane Distillation: Do Organics Really Matter. Social Science Research Network. doi:10.2139/ssrn.4279583
• Chaves, B., Alhussaini, M., Felix, V., Presson, L., Betancourt, W. Q., Hickenbottom, K., & Achilli, A. (2022). Extending the life of water reuse reverse osmosis membranes using chlorination. Journal of Membrane Science, 119897.
• Hardikar, M., Marquez, I., Phakdon, T., Sáez, A. E., & Achilli, A. (2022). Scale-up of membrane distillation systems using bench-scale data. Desalination, 530(Issue). doi:10.1016/j.desal.2022.115654
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  A procedure to design full-scale air gap membrane distillation (AGMD) processes is presented. A mathematical model was then developed for both direct contact membrane distillation (DCMD) and AGMD. The model is centered on solving local mass and energy balances using a finite difference approach. The full-scale model was calibrated by utilizing the membrane distillation coefficient (MDC) determined by DCMD bench-scale experiments, as the sole adjustable parameter. The MDC was then used to model the water production and energy efficiency of a spiral-wound AGMD full-scale element. The model yields accurate representation of full-scale AGMD elements using polytetrafluoroethylene (PTFE) and polyethylene (PE) membranes. Full-scale experimental results obtained over a wide range of feed flow rates (2 to 4.5 L/min), temperatures (40 to 80 °C), and salinities (0 to 200 g/L NaCl) confirmed that the developed procedure can be applied to model and design large-scale AGMD elements. Furthermore, the model guides the selection of specific temperature and flow conditions at a given salinity and element geometry to maximize water production and energy efficiency. This methodology is suitable for rapid evaluation of novel MD membranes performance in field AGMD applications.
• Hardikar, M., Marquez, I., Phakdon, T., Sáez, A. E., & Achilli, A. (2022). Scale-up of membrane distillation systems using bench-scale data. Desalination, 530, 115654.
• Marquez, I., Saez, A. E., Ogden, K. L., & Achilli, A. (2022). A hands-on course on intensified membrane process for sustainable water purification. Chemical Engineering Education.
• Souza-Chaves, B. M., Alhussaini, M. A., Felix, V., Presson, L. K., Betancourt, W. Q., Hickenbottom, K. L., & Achilli, A. (2022). Extending the life of water reuse reverse osmosis membranes using chlorination. Journal of Membrane Science, 642(Issue). doi:10.1016/j.memsci.2021.119897
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  Numerous efforts have been made over the years to extend the lifespan of reverse osmosis (RO) membranes. End-of-life RO membranes are periodically replaced and usually discarded in landfills. Periodic membrane modification using chlorination may be an alternative to recover their productivity without compromising process safety. In this research, RO membranes from an engineering-scale ultrafiltration-RO system treating reclaimed water were exposed five times to 2000 ppm-h of chlorine immediately after chemical cleaning. Water, conductivity, ion, and organic permeability coefficients and rejection were related to the chlorine dose. The breakthrough of six naturally occurring viruses with different levels of persistence to wastewater treatment was also monitored. After five chlorine doses, the apparent water permeability was recovered to 1.0–1.5 L m−2 h−1 bar−1, a 3.1-fold increase compared to the end-of-life membranes, with only a 2% decrease in observed salt rejection. Interestingly, apparent conductivity and ion permeability slightly decreased after the first and second chlorine dose, likely because the chlorine removed irreversible fouling/scaling and thus reduced concentration polarization. After the third chlorine dose, as the RO membrane surface oxidized, more monovalent ions permeated through the membrane, while observed divalent ion rejection remained relatively high and constant (>97%). Similarly, the RO permeate dissolved organic carbon concentration and total fluorescence intensity decreased between end-of-life membrane and the second chlorine dose, followed by an increase after the third dose, and only humic substances and building block compounds (
• Xu, J., Phakdon, T., Achilli, A., Hickenbottom, K., & Farrell, J. (2022). Pretreatment of Reverse Osmosis Concentrate from Reclaimed Water for Conventional and High-Efficiency Reverse Osmosis and Evaluation of Electrochemical Production of Reagents. ACS ES and T Water, 2(Issue 6). doi:10.1021/acsestwater.2c00015
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  The primary goal of this research was to investigate several water treatment unit operations for converting RO concentrate produced from treated municipal wastewater into potable water. The secondary goal was to evaluate the use of an electrochemical cell for producing the reagents needed to operate a fluidized bed crystallization reactor (FBCR), regenerate ion exchange media, and produce a ferric iron coagulating agent. The effectiveness of the pretreatment processes to prevent membrane fouling were evaluated for conventional and high-efficiency reverse osmosis (HERO). Fluidized bed crystallization removed 93 to >97% of hardness ions, 42% of silica, and 6.5% of total organic carbon. Membrane fouling during HERO was lower than that for conventional RO for pretreatment using fluidized bed crystallization and ion exchange. However, conventional RO with ferric iron coagulation following fluidized bed crystallization and ion exchange showed the least membrane fouling and increased recovery in the second stage RO by 470%. The use of an electrochemical cell for generating the reagents needed for the pretreatment processes was evaluated. Energy costs for operating the electrochemical cell for making acid, base, and ferric iron coagulant were 4.1 kWh per m3 of RO concentrate. The use of electrochemically generated reagents combined with fluidized bed crystallization produces no waste solutions from the pretreatment processes.
• Xu, J., Phakdon, T., Achilli, A., Hickenbottom, K., & Farrell, J. (2022). Pretreatment of Reverse Osmosis Concentrate from Reclaimed Water for Conventional and High-Efficiency Reverse Osmosis and Evaluation of Electrochemical Production of Reagents. ACS ES&T Water, 2(6), 1022-1030.
• Achilli, A., Albrecht, T. R., Boccelli, D. L., Cath, T. Y., Crosson, C., Daigger, G. T., Duan, J. G., Lansey, K. E., Mack, E. A., Meixner, T., Pincetl, S., Scott, C. A., Shrestha, P. P., & Zuniga-teran, A. A. (2021). Net Zero Urban Water from Concept to Applications: Integrating Natural, Built, and Social Systems for Responsive and Adaptive Solutions. ACS EST Water, 1(3), 518-529. doi:10.1021/acsestwater.0c00180
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  Innovation in urban water systems is required to address drivers of change across natural, built, and social systems, including climate change, economic development, and aged infrastructure. Water ...
• Binger, Z. M., O'Toole, G., & Achilli, A. (2021). Evidence of solution-diffusion-with-defects in an engineering-scale pressure retarded osmosis system. Journal of Membrane Science, 625(Issue). doi:10.1016/j.memsci.2021.119135
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  An engineering-scale seawater reverse osmosis-pressure retarded osmosis (SWRO-PRO) system was designed and deployed to evaluate the energy recovery during seawater desalination through salinity gradient energy. Experimental data on energy recovery and consumption were collected from a PRO system composed of up to five 4040 spiral-wound membrane elements, utilizing freshwater and RO concentrate to drive permeation. During experimental testing, specific energy recoveries as high as 0.14 kW h/m3 were achieved; however, energy consumption due to pressure losses in the system reduced the net specific energy recovery to a maximum of −0.07 kW h/m3. A 100% increase in energy recovery or 50% decrease in energy consumption would be necessary to yield a positive net energy recovery. Also, a combined approach of simultaneously increasing energy recovery and decreasing energy consumption would be a more desirable path for SWRO-PRO to become an energy positive technology. Experimental data were then paired with modeling software utilizing a solution-diffusion-with-defects model to demonstrate the presence and extent of defects in the membrane structure that allow for pressure-driven pore flow. The solution-diffusion-with-defect model explains the lower than expected water permeability and salt rejection often seen in experimental PRO results. Integrating this model into future software will allow for more accurate simulation of larger systems and aid in investigations of PRO scale-up.
• Crosson, C., Achilli, A., Zuniga-Teran, A., Mack, E., Albrecht, T., Shrestha, P., Boccelli, D., Cath, T., Daigger, G., Duan, J., Lansey, K., Meixner, T., Pincetl, S., & Scott, C. (2021). Net Zero Urban Water from Concept to Applications: Integrating Natural, Built, and Social Systems for Responsive and Adaptive Solutions. ACS ES and T Water, 1(3). doi:10.1021/acsestwater.0c00180
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  Innovation in urban water systems is required to address drivers of change across natural, built, and social systems, including climate change, economic development, and aged infrastructure. Water systems are complex socio-technical systems that interact with biophysical systems to supply and reclaim water. We present a vision for enhancing urban water system resilience through a net zero urban water (NZUW) approach, which meets the needs of a given community with a locally available and sustainable water supply, without detriment to interconnected systems or long-term water supply. NZUW is an integrative approach with progressive targets assessed using a quantitative framework to expand adaptive and responsive solutions for urban water self-sufficiency. Decision makers can use NZUW to understand trade-offs between future interventions to urban water systems across spatial and temporal scales. We present the overall NZUW approach, drivers of change, applications, and research gaps.
• Hardikar, M., Ikner, L. A., Felix, V., Presson, L. K., Rabe, A. B., Hickenbottom, K. L., & Achilli, A. (2021). Membrane Distillation Provides a Dual Barrier for Coronavirus and Bacteriophage Removal. Environmental Science and Technology Letters, 8(Issue 8). doi:10.1021/acs.estlett.1c00483
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  The persistence of pathogenic microorganisms in treated wastewater effluent makes disinfection crucial to achieve wastewater reuse. Membrane processes such as ultrafiltration and reverse osmosis (RO) have shown promising results for virus and other contaminant removal from treated wastewater effluents for reuse application. However, RO produces a concentrate stream which contains high concentrations of pathogens and contaminants that often requires treatment and volume reduction before disposal. Membrane distillation (MD) is a treatment process that can reduce RO concentrate volume while augmenting the potable water supply. MD is also a dual barrier approach for virus removal as it operates at a high temperature and permeates only the vapor phase through the membrane interface. The effects of temperature on viable virus concentration and membrane rejection of viruses in MD are investigated in this study using two nonenveloped phages frequently used as enteric virus surrogates (MS2 and PhiX174) and an enveloped pathogenic virus (HCoV-229E). At typical MD operating temperatures (greater than 65 °C), viable concentrations of all three viruses were reduced by thermal inactivation by more than 6-log10 for MS2 and PhiX174 and more than 3-log10 for HCoV-229E. Also, membrane rejection was greater than 6-log10 for MS2 and PhiX174 and greater than 2.5-log10 for HCoV-229E.
• Hardikar, M., Ikner, L. A., Felix, V., Presson, L. K., Rabe, A. B., Hickenbottom, K. L., & Achilli, A. (2021). Membrane Distillation Provides a Dual Barrier for Coronavirus and Bacteriophage Removal. Environmental science & technology letters, 8(8), 713-718.
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  The persistence of pathogenic microorganisms in treated wastewater effluent makes disinfection crucial to achieve wastewater reuse. Membrane processes such as ultrafiltration and reverse osmosis (RO) have shown promising results for virus and other contaminant removal from treated wastewater effluents for reuse application. However, RO produces a concentrate stream which contains high concentrations of pathogens and contaminants that often requires treatment and volume reduction before disposal. Membrane distillation (MD) is a treatment process that can reduce RO concentrate volume while augmenting the potable water supply. MD is also a dual barrier approach for virus removal as it operates at a high temperature and permeates only the vapor phase through the membrane interface. The effects of temperature on viable virus concentration and membrane rejection of viruses in MD are investigated in this study using two nonenveloped phages frequently used as enteric virus surrogates (MS2 and PhiX174) and an enveloped pathogenic virus (HCoV-229E). At typical MD operating temperatures (greater than 65 °C), viable concentrations of all three viruses were reduced by thermal inactivation by more than 6-log for MS2 and PhiX174 and more than 3-log for HCoV-229E. Also, membrane rejection was greater than 6-log for MS2 and PhiX174 and greater than 2.5-log for HCoV-229E.
• Rabe, A., Presson, L., Felix, V., Hardikar, M., Hickenbottom, K., Achilli, A., & Ikner, L. A. (2021). Membrane distillation provides a dual barrier for coronavirus and bacteriophage removal. Environmental Science & Technology Letters.
• Tow, E. W., Hartman, A. L., Jaworowski, A., Zucker, I., Kum, S., AzadiAghdam, M., Blatchley, E. R., Achilli, A., Gu, H., Urper, G. M., & Warsinger, D. M. (2021). Modeling the energy consumption of potable water reuse schemes. Water research X, 13, 100126.
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  Potable reuse of municipal wastewater is often the lowest-energy option for increasing the availability of fresh water. However, limited data are available on the energy consumption of potable reuse facilities and schemes, and the many variables affecting energy consumption obscure the process of estimating energy requirements. By synthesizing available data and developing a simple model for the energy consumption of centralized potable reuse schemes, this study provides a framework for understanding when potable reuse is the lowest-energy option for augmenting water supply. The model is evaluated to determine a representative range for the specific electrical energy consumption of direct and indirect potable reuse schemes and compare potable reuse to other water supply augmentation options, such as seawater desalination. Finally, the model is used to identify the most promising avenues for further reducing the energy consumption of potable reuse, including encouraging direct potable reuse without additional drinking water treatment, avoiding reverse osmosis in indirect potable reuse when effluent quality allows it, updating pipe networks, or using more permeable membranes. Potable reuse already requires far less energy than seawater desalination and, with a few investments in energy efficiency, entire potable reuse schemes could operate with a specific electrical energy consumption of less than 1 kWh/m, showing the promise of potable reuse as a low-energy option for augmenting water supply.
• Aghdam, M. A., Achilli, A., Snyder, S. A., & Farrell, J. (2020). Increasing water recovery during reclamation of treated municipal wastewater using bipolar membrane electrodialysis and fluidized bed crystallization. Journal of Water Process Engineering. doi:10.1016/j.jwpe.2020.101555
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  This research investigated the effectiveness of bipolar membrane electrodialysis coupled with fluidized bed crystallization and coagulation/flocculation with FeCl3 for removing potential membrane foulants from reverse osmosis (RO) concentrate solutions produced during reclamation of municipally treated wastewater. The goal of the treatment process was to produce water with low concentrations of potential foulants that could be subjected to a high recovery secondary RO process. Effluent from the secondary clarifier at a municipal wastewater treatment plant was treated by ultrafiltration and RO at a recovery of 60–65 %. The RO concentrate solution was then fed into a fluidized bed crystallization reactor operating at a pH value of 11.5. Calcium, magnesium, silica and dissolved organic matter were removed from the RO concentrate via precipitation of mineral solids on 60 mesh garnet sand. The acid and base utilized in the fluidized bed crystallization reactor was produced using bipolar membrane electrodialysis from the treated RO concentrate solution after polishing with coagulation/flocculation with FeCl3. The treatment system was able to remove 84 % of Ca2+, 93 % of Ba2+, >99 % of Mg2+, 80 % of total organic carbon (TOC), and 68 % of dissolved silica from the RO concentrate solutions. The product water produced by the system contained mostly Na+, Cl− and SO42- ions, with ≤ 10 mg/L Ca2+ and SiO2, ≤ 2 mg/L TOC, and ≤ 1 mg/L Mg2+. The electrical energy for operating the bipolar membrane electrodialysis cell amounted to 110 kW h per kmol of acid and base produced, which translates to 3.5 kW h/m3 of treated RO concentrate.
• AzadiAghdam, M., Park, M., Lopez-Prieto, I. J., Achilli, A., Snyder, S. A., & Farrell, J. (2020). Pretreatment for water reuse using fluidized bed crystallization. Journal of Water Process Engineering, 35(Issue). doi:10.1016/j.jwpe.2020.101226
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  This research investigated the use of fluidized bed crystallization for removing scale forming species and natural organic matter (NOM) from treated municipal wastewater prior to water reclamation. The effect of pH on Ca2+, Mg2+, silica and NOM removal in a fluidized bed crystallization reactor (FBCR) was determined. NOM removal in the FBCR was compared to that for the conventional treatments, ultrafiltration and ferric chloride coagulation/flocculation. Under optimized conditions, fluidized bed crystallization was able to remove more than 99.9 % of Mg2+, 97 % of Ca2+ and 42 % of silica. The FBCR was also able to remove 25 % of NOM, which was intermediate between NOM removal by ferric chloride (56 %) and ultrafiltration (13 %). Size exclusion chromatography-organic carbon detection (SEC−OCD) indicated that the majority of NOM removal occurred via co-precipitation with Mg(OH)2. Excitation emission matrix-parallel factor (EEM-PARAFAC) analysis was used to investigate the types of NOM removed. The FBCR was able to remove all five NOM components (three humic acids, one fulvic acid and one protein-like substance), including 100 % of the autochthonous fulvic acids. Ferric chloride was also able to remove all five NOM components, but only one third of the autochthonous fulvic acids, while ultrafiltration was able to remove only 11 % of the protein-like NOM.
• AzadiAghdam, M., Park, M., Lopez-Prieto, I. J., Achilli, A., Snyder, S. A., & Farrell, J. (2020). Pretreatment for water reuse using fluidized bed crystallization. Journal of Water Process Engineering.
• Binger, Z. M., & Achilli, A. (2020). Forward osmosis and pressure retarded osmosis process modeling for integration with seawater reverse osmosis desalination. Desalination, 491(Issue). doi:10.1016/j.desal.2020.114583
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  Osmotically driven membrane processes such as forward osmosis and pressure retarded osmosis may hold key advantages when integrated with seawater reverse osmosis to form hybrid FO-RO and RO-PRO systems. In this work, module-scale modeling of these two processes was improved by accurately representing the features of a spiral-wound membrane. The model captures important characteristics such as the cross-flow stream orientation, membrane baffling, and channel dimensions unique to spiral-wound membranes. The new module-scale model was then scaled to the system-level to compare various system designs for FO-RO and RO-PRO systems, most notably, a multi-stage recharge design was defined. Results indicate that the multi-stage recharge design leads to an increase in wastewater utilization, as high as 90%, when compared to the single-stage designs. Additionally, the multi-stage recharge configuration can increase the specific energy recovery of pressure retarded osmosis by over 75%. The multi-stage recharge design is found to be not only advantageous but may be also necessary to the integration of osmotically driven membrane processes with seawater reverse osmosis.
• Binger, Z. M., & Achilli, A. (2020). Forward osmosis and pressure retarded osmosis process modeling for integration with seawater reverse osmosis desalination. Desalination.
• Crosson, C., Achilli, A., Zuniga Teran, A. A., Mack, E. A., Albrecht, T., Shrestha, P. P., Boccelli, D., Cath, T. Y., Daigger, G. T., Duan, J. G., Lansey, K. E., Meixner, T., Pincetl, S., & Scott, C. A. (2020). Net Zero Urban Water from Concept to Applications: Integrating Natural, Built, and Social Systems for Responsive and Adaptive Solutions. ACS ES&T Water.
• Hardikar, M., Marquez, I., & Achilli, A. (2020). Emerging investigator series: membrane distillation and high salinity: analysis and implications. Environmental Science: Water Research & Technology.
• Wei, X., Binger, Z. M., Achilli, A., Sanders, K. T., & Childress, A. E. (2020). A modeling framework to evaluate blending of seawater and treated wastewater streams for synergistic desalination and potable reuse. Water Research, 170(Issue). doi:10.1016/j.watres.2019.115282
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  A modeling framework was developed to evaluate synergistic blending of the waste streams from seawater reverse osmosis (RO) desalination and wastewater treatment facilities that are co-located or in close proximity. Four scenarios were considered, two of which involved blending treated wastewater with the brine resulting from the seawater RO desalination process, effectively diluting RO brine prior to discharge. One of these scenarios considers the capture of salinity-gradient energy. The other two scenarios involved blending treated wastewater with the intake seawater to dilute the influent to the RO process. One of these scenarios incorporates a low-energy osmotic dilution process to provide high-quality pre-treatment for the wastewater. The model framework evaluates required seawater and treated wastewater flowrates, discharge flowrates and components, boron removal, and system energy requirements. Using data from an existing desalination facility in close proximity to a wastewater treatment facility, results showed that the influent blending scenarios (Scenarios 3 and 4) had several advantages over the brine blending scenarios (Scenarios 1 and 2), including: (1) reduced seawater intake and brine discharge flowrates, (2) no need for second-pass RO for boron control, and (3) reduced energy consumption. It should be noted that the framework was developed for use with co-located seawater desalination and coastal wastewater reclamation facilities but could be extended for use with desalination and wastewater reclamation facilities in in-land locations where disposal of RO concentrate is a serious concern.
• Wei, X., Binger, Z. M., Achilli, A., Sanders, K. T., & Childress, A. E. (2020). A modeling framework to evaluate blending of seawater and treated wastewater streams for synergistic desalination and potable reuse. Water research, 170, 115282.
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  A modeling framework was developed to evaluate synergistic blending of the waste streams from seawater reverse osmosis (RO) desalination and wastewater treatment facilities that are co-located or in close proximity. Four scenarios were considered, two of which involved blending treated wastewater with the brine resulting from the seawater RO desalination process, effectively diluting RO brine prior to discharge. One of these scenarios considers the capture of salinity-gradient energy. The other two scenarios involved blending treated wastewater with the intake seawater to dilute the influent to the RO process. One of these scenarios incorporates a low-energy osmotic dilution process to provide high-quality pre-treatment for the wastewater. The model framework evaluates required seawater and treated wastewater flowrates, discharge flowrates and components, boron removal, and system energy requirements. Using data from an existing desalination facility in close proximity to a wastewater treatment facility, results showed that the influent blending scenarios (Scenarios 3 and 4) had several advantages over the brine blending scenarios (Scenarios 1 and 2), including: (1) reduced seawater intake and brine discharge flowrates, (2) no need for second-pass RO for boron control, and (3) reduced energy consumption. It should be noted that the framework was developed for use with co-located seawater desalination and coastal wastewater reclamation facilities but could be extended for use with desalination and wastewater reclamation facilities in in-land locations where disposal of RO concentrate is a serious concern.
• Armstrong, N. R., Shallcross, R. C., Ogden, K., Snyder, S., Achilli, A., & Armstrong, E. L. (2018). Challenges and opportunities at the nexus of energy, water, and food: A perspective from the southwest United States. MRS Energy & Sustainability, 5, E6.
• Morrow, C. P., Furtaw, N. M., Murphy, J. R., Achilli, A., Marchand, E. A., Hiibel, S. R., & Childress, A. E. (2018). Integrating an aerobic/anoxic osmotic membrane bioreactor with membrane distillation for potable reuse. DESALINATION, 432, 46-54.
• Morrow, C. P., Furtaw, N. M., Murphy, J. R., Achilli, A., Marchand, E. A., Hiibel, S. R., & Childress, A. E. (2018). Integrating an aerobic/anoxic osmotic membrane bioreactor with membrane distillation for potable reuse. Desalination, 432(Issue). doi:10.1016/j.desal.2017.12.047
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  A novel osmotic membrane bioreactor-membrane distillation (OMBR-MD) system was designed and fabricated to treat wastewater for potable reuse. Before longer-term operation to evaluate water flux and biological treatment of the pilot-scale OMBR subsystem, two forward osmosis (FO) membranes were evaluated at the bench-scale. There was no statistical difference between cellulose triacetate and thin-film composite membrane performance for activated sludge feed solution. Also, FO water flux during long-term operation was the same for 20 and 35 g/L NaCl draw solutions; however, the 35 g/L NaCl draw solution resulted in greater reverse salt flux and higher conductivity in the bioreactor. The OMBR subsystem was integrated with an MD subsystem to reconcentrate the draw solution and produce high quality product water. Results from long-term testing using a high-strength wastewater showed 98.4% COD removal and 90.2% NH4+-N could be achieved with a single bioreactor by alternating aeration on/off cycles to control the redox environment. An automated dosing and transfer system was developed to maintain constant FO draw solution concentration and prevent heat from being transferred to the bioreactor, which is critical for maintaining biological nitrogen removal.
• Rodman, K. E., Cervania, A. A., Budig-Markin, V., Schermesser, C. F., Rogers, O. W., Martinez, J. M., King, J., Hassett, P., Burns, J., Gonzales, M. S., Folkerts, A., Duin, P., Virgil, A. S., Aldrete, M., Lagasca, A., Infanzon-Marin, A., Aitchison, J. R., White, D., Boutros, B. C., , Ortega, S., et al. (2018). Coastal California Wastewater Effluent as a Resource for Seawater Desalination Brine Commingling. WATER, 10(3).
• Rodman, K. E., Cervania, A. A., Budig-Markin, V., Schermesser, C. F., Rogers, O. W., Martinez, J. M., King, J., Hassett, P., Burns, J., Gonzales, M. S., Folkerts, A., Duin, P., Virgil, A. S., Aldrete, M., Lagasca, A., Infanzon-Marin, A., Aitchison, J. R., White, D., Boutros, B. C., , Ortega, S., et al. (2018). Coastal California Wastewater effluent as a resource for seawater desalination brine commingling. Water (Switzerland), 10(Issue 3). doi:10.3390/w10030322
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  California frequently experiences water scarcity, especially in high population areas. This has generated increased interest in using the Pacific Ocean as a water resource, with seawater desalination becoming a popular solution. To mitigate the environmental impacts of the high salinity brine from seawater desalination, California recommends commingling brine with wastewater effluent before ocean discharge. Results reveal that throughout the California coast, approximately 4872 MLD (1287 MGD) of treated wastewater are discharged into the ocean and might be available as dilution water. Most of this dilution water resource is produced in Southern California (3161 MLD or 835 MGD) and the San Francisco Bay Area (1503 MLD or 397 MGD), which are also the areas with the highest need for alternative water sources. With this quantity of dilution water, in principle, over 5300 MLD (1400 MGD) of potable water could be produced in California through seawater desalination. Furthermore, this study provides a survey of the treatment levels and typical discharge violations of ocean wastewater treatment facilities in California.
• Warsinger, D. M., Chakraborty, S., Tow, E. W., Plumlee, M. H., Bellona, C., Loutatidou, S., Karimi, L., Mikelonis, A. M., Achilli, A., Ghassemi, A., Padhye, L. P., Snyder, S. A., Curcio, S., Vecitis, C. D., Arafat, H. A., & Lienhard, J. (2018). A review of polymeric membranes and processes for potable water reuse. PROGRESS IN POLYMER SCIENCE, 81, 209-237.
• Achilli, A. (2016). A stepwise model of direct contact membrane distillation for application to large-scale systems: Experimental results and model predictions. Desalination.
• Achilli, A. (2016). River-to-sea pressure retarded osmosis: Resource utilization in a full-scale facility. Desalination.
• Gustafson, R. D., Murphy, J. R., & Achilli, A. (2016). A stepwise model of direct contact membrane distillation for application to large-scale systems: Experimental results and model predictions. Desalination, 378(Issue). doi:10.1016/j.desal.2015.09.022
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  A model of mass and heat transfer in direct contact membrane distillation (DCMD) is presented. The distributions of water flux, temperature, and concentration in membrane module channels are modeled to provide cumulative water flux and outlet temperatures and concentrations. The membrane distillation coefficient (MDC)-a membrane-specific mass transfer coefficient-for a well-characterized PTFE membrane was shown to be accurately modeled as a constant value. The MDC was used with a stepwise modeling approach, in which the membrane area is discretized into multiple steps, to provide the distribution of process variables parallel to the membrane surface. A new generalized spacer modeling method was used to account for the presence of complex woven spacers in the flow channels, addressing a significant gap in the DCMD modeling literature. Model predictions showed good agreement with experiments in co-current and counter-current flow modes for different operating conditions and membrane sizes. The stepwise modeling approach was shown to be necessary for providing accurate mass and heat transfer predictions for large-scale DCMD modules, providing a useful tool for the design of large-scale DCMD systems.
• O'Toole, G., Jones, L., Coutinho, C., Hayes, C., Napoles, M., & Achilli, A. (2016). River-to-sea pressure retarded osmosis: Resource utilization in a full-scale facility. Desalination, 389(Issue). doi:10.1016/j.desal.2016.01.012
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  Pressure retarded osmosis (PRO) is a technology that could be utilized to recover energy from the mixing of freshwater with seawater. This source of renewable energy is sizeable and in the past decade several investigations analyzed its potential. The vast majority of studies focused on mass transfer problems across the membrane in order to improve membrane productivity and just recently studies started to look at membrane module efficiencies and parasitic loads within the PRO facility. In this article, the net specific energy production from a facility-scale PRO system was determined and optimized by using a novel simulation method that integrates parasitic loads and efficiencies of the PRO facility components and combines the model with an optimization software in a linked system optimization scheme. It was found that the overall net specific energy that may be recovered by a river-to-sea PRO facility is approximately 0.12 kWh per m3 of permeate. Furthermore, a sensitivity analysis was performed to elucidate the relationship between net specific energy and power density as functions of membrane area, flow rates, and operating pressures. In general, in order to maximize resource recovery, a low power density, thus a low membrane productivity, must be accepted.
• Warsinger, D. M., Chakraborty, S., Tow, E. W., Plumlee, M. H., Bellona, C., Loutatidou, S., Karimi, L., Mikelonis, A. M., Achilli, A., Ghassemi, A., Padhye, L. P., Snyder, S. A., Curcio, S., Vecitis, C., Arafat, H. A., & Lienhard, J. H. (2016). A review of polymeric membranes and processes for potable water reuse. Progress in polymer science, 81, 209-237.
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  Conventional water resources in many regions are insufficient to meet the water needs of growing populations, thus reuse is gaining acceptance as a method of water supply augmentation. Recent advancements in membrane technology have allowed for the reclamation of municipal wastewater for the production of drinking water, i.e., potable reuse. Although public perception can be a challenge, potable reuse is often the least energy-intensive method of providing additional drinking water to water stressed regions. A variety of membranes have been developed that can remove water contaminants ranging from particles and pathogens to dissolved organic compounds and salts. Typically, potable reuse treatment plants use polymeric membranes for microfiltration or ultrafiltration in conjunction with reverse osmosis and, in some cases, nanofiltration. Membrane properties, including pore size, wettability, surface charge, roughness, thermal resistance, chemical stability, permeability, thickness and mechanical strength, vary between membranes and applications. Advancements in membrane technology including new membrane materials, coatings, and manufacturing methods, as well as emerging membrane processes such as membrane bioreactors, electrodialysis, and forward osmosis have been developed to improve selectivity, energy consumption, fouling resistance, and/or capital cost. The purpose of this review is to provide a comprehensive summary of the role of polymeric membranes in the treatment of wastewater to potable water quality and highlight recent advancements in separation processes. Beyond membranes themselves, this review covers the background and history of potable reuse, and commonly used potable reuse process chains, pretreatment steps, and advanced oxidation processes. Key trends in membrane technology include novel configurations, materials and fouling prevention techniques. Challenges still facing membrane-based potable reuse applications, including chemical and biological contaminant removal, membrane fouling, and public perception, are highlighted as areas in need of further research and development.
• Achilli, A. (2015). Factors contributing to flux improvement in vacuum-enhanced direct contact membrane distillation. Desalination.
• Achilli, A. (2015). The osmotic membrane bioreactor: A critical review. Environmental Science: Water Research and Technology.
• Rao, G., Hiibel, S. R., Achilli, A., & Childress, A. E. (2015). Factors contributing to flux improvement in vacuum-enhanced direct contact membrane distillation. Desalination, 367(Issue). doi:10.1016/j.desal.2015.04.002
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  Low water flux in membrane distillation (MD) is a concern for full-scale application. In the past decades, attempts have been made to improve water flux in MD and vacuum-enhanced direct-contact MD (VEDCMD) has been proven to be an effective configuration to achieve this. However, only qualitative assessments of the factors that might improve water flux have been reported in the literature. In this study, a mechanistic investigation of the factors contributing to higher water flux in VEDCMD was performed. Direct-contact MD (DCMD) and pressure-enhanced DCMD (PEDCMD) configurations were also investigated for comparison. Less membrane compaction was identified as one dominant factor contributing to improved water flux in VEDCMD as very little compaction occurred in VEDCMD compared to that which occurred in DCMD and PEDCMD. Lower air pressure inside the membrane pores was found to be the other dominant factor contributing to improved water flux in VEDCMD; the air pressure was calculated as the average of the feed and distillate pressures in VEDCMD and as the distillate pressure in DCMD and PEDCMD. Pressure difference, as is present in both PEDCMD and VEDCMD, was found to have a minimal effect on water flux.
• Achilli, A. (2014). Experimental results from RO-PRO: A next generation system for low-energy desalination. Environmental Science and Technology.
• Achilli, A. (2014). RO-PRO desalination: An integrated low-energy approach to seawater desalination. Applied Energy.
• Achilli, A., Prante, J. L., Hancock, N. T., Maxwell, E. B., & Childress, A. E. (2014). Experimental Results from RO-PRO: A Next Generation System for Low-Energy Desalination. Environmental Science and Technology. doi:10.1021/es405556s
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  A pilot system was designed and constructed to evaluate reverse osmosis (RO) energy reduction that can be achieved using pressure-retarded osmosis (PRO). The RO-PRO experimental system is the first known system to utilize energy from a volume of water transferred from atmospheric pressure to elevated pressure across a semipermeable membrane to prepressurize RO feedwater. In other words, the system demonstrated that pressure could be exchanged between PRO and RO subsystems. Additionally, the first experimental power density data for a RO-PRO system is now available. Average experimental power densities for the RO-PRO system ranged from 1.1 to 2.3 W/m2. This is higher than previous river-to-sea PRO pilot systems (1.5 W/m2) and closer to the goal of 5 W/m2 that would make PRO an economically feasible technology. Furthermore, isolated PRO system testing was performed to evaluate PRO element performance with higher cross-flow velocities and power densities exceeding 8 W/m2 were achieved with a 28 g/L NaCl draw solution. From this empirical data, inferences for future system performance can be drawn that indicate future RO-PRO systems may reduce the specific energy requirements for desalination by ∼1 kWh/m3.
• Achilli, A., Prante, J. L., Hancock, N. T., Maxwell, E. B., & Childress, A. E. (2014). Experimental results from RO-PRO: a next generation system for low-energy desalination. Environmental science & technology, 48(11), 6437-43.
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  A pilot system was designed and constructed to evaluate reverse osmosis (RO) energy reduction that can be achieved using pressure-retarded osmosis (PRO). The RO-PRO experimental system is the first known system to utilize energy from a volume of water transferred from atmospheric pressure to elevated pressure across a semipermeable membrane to prepressurize RO feedwater. In other words, the system demonstrated that pressure could be exchanged between PRO and RO subsystems. Additionally, the first experimental power density data for a RO-PRO system is now available. Average experimental power densities for the RO-PRO system ranged from 1.1 to 2.3 W/m2. This is higher than previous river-to-sea PRO pilot systems (1.5 W/m2) and closer to the goal of 5 W/m2 that would make PRO an economically feasible technology. Furthermore, isolated PRO system testing was performed to evaluate PRO element performance with higher cross-flow velocities and power densities exceeding 8 W/m2 were achieved with a 28 g/L NaCl draw solution. From this empirical data, inferences for future system performance can be drawn that indicate future RO-PRO systems may reduce the specific energy requirements for desalination by ∼1 kWh/m3.
• Prante, J. L., Ruskowitz, J. A., Childress, A. E., & Achilli, A. (2014). RO-PRO desalination: An integrated low-energy approach to seawater desalination. Applied Energy, 120(Issue). doi:10.1016/j.apenergy.2014.01.013
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  Although reverse osmosis (RO) is currently the most energy efficient desalination technology, it still requires a great deal of energy to create the high pressures necessary to desalinate seawater. An opposite process of RO, called pressure retarded osmosis (PRO), utilizes the salinity gradient between a relatively fresh impaired water source and seawater to produce pressure and hence, energy. In this paper, PRO is evaluated in conjunction with RO, in a system called RO-PRO desalination, to reduce the energy requirement of seawater RO desalination. RO-PRO specific energy consumption was modeled using RO conditions at the thermodynamic restriction and a newly developed module-based PRO model. Using a well-characterized cellulose triacetate (CTA) membrane, the minimum net specific energy consumption of the system was found to be approximately 40% lower than state-of-the-art seawater RO. A sensitivity analysis was performed to determine the effects of membrane characteristics on the specific energy production of the PRO process in the RO-PRO system. The sensitivity analysis showed that the minimum specific energy consumption using virtual membranes is approximately 1.0kWh per m3 of RO permeate at 50% RO recovery and that a maximum power density of approximately 10W/m2 could be achieved. © 2014.
• Achilli, A. (2013). Standard Methodology for Evaluating Membrane Performance in Osmotically Driven Membrane Processes. Desalination.
• Cath, T. Y., Elimelech, M., McCutcheon, J. R., McGinnis, R. L., Achilli, A., Anastasio, D., Brady, A. R., Childress, A. E., Farr, I. V., Hancock, N. T., Lampi, J., Nghiem, L. D., Xie, M., & Yip, N. Y. (2013). Standard Methodology for Evaluating Membrane Performance in Osmotically Driven Membrane Processes. Desalination, 312(Issue). doi:10.1016/j.desal.2012.07.005
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  Osmotically driven membrane processes (ODMPs) such as forward osmosis (FO) and pressure retarded osmosis (PRO) are extensively investigated for utilization in a broad range of applications. In ODMPs, the operating conditions and membrane properties play more critical roles in mass transport and process performance than in pressure-driven membrane processes. Search of the literature reveals that ODMP membranes, especially newly developed ones, are tested under different temperatures, draw solution compositions and concentrations, flow rates, and pressures. In order to compare different membranes, it is important to develop standard protocols for testing of membranes for ODMPs. In this article we present a standard methodology for testing of ODMP membranes based on experience gained and operating conditions used in FO and PRO studies in recent years. A round-robin testing of two commercial membranes in seven independent laboratories revealed that water flux and membrane permeability coefficients were similar when participants performed the experiments and calculations using the same protocols. The thin film composite polyamide membrane exhibited higher water and salt permeability than the asymmetric cellulose-based membrane, but results with the high permeability thin-film composite membrane were more scattered. While salt rejection results in RO mode were relatively similar, salt permeability coefficients for both membranes in FO mode were more varied. Results suggest that high permeability ODMP membranes should be tested at lower hydraulic pressure in RO mode and that RO testing be conducted with the same membrane sample used for testing in FO mode. © 2012 Elsevier B.V.
• Achilli, A. (2012). Organic ionic salt draw solutions for osmotic membrane bioreactors. Bioresource Technology.
• Bowden, K. S., Achilli, A., & Childress, A. E. (2012). Organic ionic salt draw solutions for osmotic membrane bioreactors. Bioresource Technology, 122(Issue). doi:10.1016/j.biortech.2012.06.026
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  This investigation evaluates the use of organic ionic salt solutions as draw solutions for specific use in osmotic membrane bioreactors. Also, this investigation presents a simple method for determining the diffusion coefficient of ionic salt solutions using only a characterized membrane. A selection of organic ionic draw solutions underwent a desktop screening process before being tested in the laboratory and evaluated for performance using specific salt flux (reverse salt flux per unit water flux), biodegradation potential, and replenishment cost. Two of the salts were found to have specific salt fluxes three to six times lower than two commonly used inorganic draw solutions, NaCl and MgCl2. All of the salts tested have organic anions with the potential to degrade in the bioreactor as a carbon source and aid in nutrient removal. Results demonstrate the potential benefits of organic ionic salt draw solutions over currently implemented inorganics in osmotic membrane bioreactor systems. © 2012 Elsevier Ltd.
• Bowden, K. S., Achilli, A., & Childress, A. E. (2012). Organic ionic salt draw solutions for osmotic membrane bioreactors. Bioresource technology, 122, 207-16.
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  This investigation evaluates the use of organic ionic salt solutions as draw solutions for specific use in osmotic membrane bioreactors. Also, this investigation presents a simple method for determining the diffusion coefficient of ionic salt solutions using only a characterized membrane. A selection of organic ionic draw solutions underwent a desktop screening process before being tested in the laboratory and evaluated for performance using specific salt flux (reverse salt flux per unit water flux), biodegradation potential, and replenishment cost. Two of the salts were found to have specific salt fluxes three to six times lower than two commonly used inorganic draw solutions, NaCl and MgCl(2). All of the salts tested have organic anions with the potential to degrade in the bioreactor as a carbon source and aid in nutrient removal. Results demonstrate the potential benefits of organic ionic salt draw solutions over currently implemented inorganics in osmotic membrane bioreactor systems.
• Achilli, A. (2011). A performance evaluation of three membrane bioreactor systems: Aerobic, anaerobic, and attached-growth. Water Science and Technology.
• Achilli, A., Childress, A. E., & Marchand, E. A. (2011). Alternative Membrane Bioreactors: Anaerobic and Attached-Growth. Proceedings of the Water Environment Federation, 2011(11), 4942-4947. doi:10.2175/193864711802765381
• Achilli, A., Marchand, E. A., & Childress, A. E. (2011). A performance evaluation of three membrane bioreactor systems: Aerobic, anaerobic, and attached-growth. Water Science and Technology, 63(Issue 12). doi:10.2166/wst.2011.559
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  Water sustainability is essential for meeting human needs for drinking water and sanitation in both developing and developed countries. Reuse, decentralization, and low energy consumption are key objectives to achieve sustainability in wastewater treatment. Consideration of these objectives has led to the development of new and tailored technologies in order to balance societal needs with the protection of natural systems. Membrane bioreactors (MBRs) are one such technology. In this investigation, a comparison of MBR performance is presented. Laboratory-scale submerged aerobic MBR (AMBR), anaerobic MBR (AnMBR), and attached-growth aerobic MBR (AtMBR) systems were evaluated for treating domestic wastewater under the same operating conditions. Long-term chemical oxygen demand (COD) and total organic carbon (TOC) monitoring showed greater than 80% removal in the three systems. The AnMBR system required three months of acclimation prior to steady operation, compared to one month for the aerobic systems. The AnMBR system exhibited a constant mixed liquor suspended solids concentration at an infinite solids retention time (i.e. no solids wasting), while the aerobic MBR systems produced ∼0.25 g of biomass per gram of COD removed. This suggests a more economical solids management associated with the AnMBR system. Critical flux experiments were performed to evaluate fouling potential of the MBR systems. Results showed similar critical flux values between the AMBR and the AnMBR systems, while the AtMBR system showed relatively higher critical flux value. This result suggests a positive role of the attached-growth media in controlling membrane fouling in MBR systems. © IWA Publishing 2011.
• Achilli, A. (2010). Pressure retarded osmosis: From the vision of Sidney Loeb to the first prototype installation - Review. Desalination.
• Achilli, A. (2010). Selection of inorganic-based draw solutions for forward osmosis applications. Journal of Membrane Science.
• Achilli, A., Cath, T. Y., & Childress, A. E. (2010). Selection of inorganic-based draw solutions for forward osmosis applications. Journal of Membrane Science, 364(Issue 1-2). doi:10.1016/j.memsci.2010.08.010
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  In this investigation, a protocol for the selection of optimal draw solutions for forward osmosis (FO) applications was developed and the protocol was used to determine the most appropriate draw solutions for specific FO applications using a currently available FO membrane. The protocol includes a desktop screening process and laboratory and modeling analyses. The desktop screening process resulted in 14 draw solutions suitable for FO applications. The 14 draw solutions were then tested in the laboratory to evaluate water flux and reverse salt diffusion through the FO membrane. Internal concentration polarization was found to lower both water flux and reverse salt diffusion by reducing the draw solution concentration at the interface between the support and dense layers of the membrane. Draw solution reconcentration was evaluated using reverse osmosis (RO) system design software. Analysis of experimental data and model results, combined with consideration of the costs associated with the FO and RO processes showed that a small group of seven draw solutions appeared to be the most suitable. The different characteristics of these draw solutions highlighted the importance of considering the specific FO application and membrane types being used prior to selecting the most appropriate draw solution. © 2010 Elsevier B.V.
• Achilli, A. (2009). Power generation with pressure retarded osmosis: An experimental and theoretical investigation. Journal of Membrane Science.
• Achilli, A. (2009). The forward osmosis membrane bioreactor: A low fouling alternative to MBR processes. Desalination.
• Achilli, A., Cath, T. Y., & Childress, A. E. (2009). Power generation with pressure retarded osmosis: An experimental and theoretical investigation. Journal of Membrane Science, 343(Issue 1-2). doi:10.1016/j.memsci.2009.07.006
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  Pressure retarded osmosis (PRO) was investigated as a viable source of renewable energy. In PRO, water from a low salinity feed solution permeates through a membrane into a pressurized, high salinity draw solution; power is obtained by depressurizing the permeate through a hydroturbine. A PRO model was developed to predict water flux and power density under specific experimental conditions. The model relies on experimental determination of the membrane water permeability coefficient (A), the membrane salt permeability coefficient (B), and the solute resistivity (K). A and B were determined under reverse osmosis conditions, while K was determined under forward osmosis (FO) conditions. The model was tested using experimental results from a bench-scale PRO system. Previous investigations of PRO were unable to verify model predictions due to the lack of suitable membranes and membrane modules. In this investigation, the use of a custom-made laboratory-scale membrane module enabled the collection of experimental PRO data. Results obtained with a flat-sheet cellulose triacetate (CTA) FO membrane and NaCl feed and draw solutions closely matched model predictions. Maximum power densities of 2.7 and 5.1 W/m2 were observed for 35 and 60 g/L NaCl draw solutions, respectively, at 970 kPa of hydraulic pressure. Power density was substantially reduced due to internal concentration polarization in the asymmetric CTA membranes and, to a lesser degree, to salt passage. External concentration polarization was found to exhibit a relatively small effect on reducing the osmotic pressure driving force. Using the predictive PRO model, optimal membrane characteristics and module configuration can be determined in order to design a system specifically tailored for PRO processes. © 2009 Elsevier B.V. All rights reserved.
• Achilli, A., Cath, T. Y., Marchand, E. A., & Childress, A. E. (2009). The forward osmosis membrane bioreactor: A low fouling alternative to MBR processes. Desalination, 239(Issue 1-3). doi:10.1016/j.desal.2008.02.022
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  A novel osmotic membrane bioreactor (OsMBR) is presented. The system utilizes a submerged forward osmosis (FO) membrane module inside a bioreactor. Through osmosis, water is transported from the mixed liquor across a semi-permeable membrane, and into a draw solution (DS) with a higher osmotic pressure. To produce potable water, the diluted DS is treated in a reverse osmosis (RO) unit; the by-product is a reconcentrated DS for reuse in the FO process. Preliminary results from experiments conducted with a flat-sheet cellulose triacetate FO membrane demonstrated high sustainable flux and relatively low reverse transport of solutes from the DS into the mixed liquor. Membrane fouling was controlled with osmotic backwashing. The FO membrane was found to reject 98% of organic carbon and 90% of ammonium-nitrogen; the OsMBR process (bioreactor and FO membrane) was found to remove greater than 99% of organic carbon and 98% of ammonium-nitrogen, respectively; suggesting a better compatibility of the OsMBR with downstream RO systems than conventional membrane bioreactors. © 2008 Elsevier B.V. All rights reserved.
• Achilli, A., Cath, T. Y., Childress, A. E., & Marchand, E. A. (2008). THE NOVEL OSMOTIC MEMBRANE BIOREACTOR FOR WASTEWATER TREATMENT. Proceedings of the Water Environment Federation, 2008(9), 6210-6221. doi:10.2175/193864708790893468
• Achilli, A. (2007). Treatment of dilute wastewater using an anaerobic membrane bioreactor. 2007 Membrane Technology Conference and Exposition Proceedings.
• Achilli, A., Cath, T. Y., Childress, A. E., & Marchand, E. A. (2007). The Forward Osmosis Membrane Bioreactor for Domestic Wastewater Treatment. Proceedings of the Water Environment Federation, 2007(11), 6520-6530. doi:10.2175/193864707787223637

Proceedings Publications

• Binger, Z. M., Hardikar, M., Josefik, N., Guy, K., Marchand, E. A., Hiibel, S. R., Childress, A. E., & Achilli, A. (2022). Biological Removal, Membrane Separation, and Thermal Destruction: A Multi-Barrier Approach to Potable Water Reuse and Waste Heat Recovery. In WEFTEC 2022.
• Morrow, C. P., Furtaw, N. M., Achilli, A., Marchand, E. A., Hiibel, S. R., & Childress, A. E. (2018, March). Potable reuse with engineered osmosis; integrating an osmotic membrane bioreactor with membrane distillation. In AWWA/AMTA 2018 Membrane Technology Conference & Exposition.
• Furtaw, N. M., Ahmadiannamini, P., Morrow, C. P., Murphy, J. P., Dash, S., Park, C., Achilli, A., Childress, A. E., Marchand, E. A., & Hiibel, S. R. (2017, July). Application of a submerged forward osmosis membrane bioreactor paired with membrane distillation utilizing waste heat. In 11th IWA International Conference on Water Reclamation and Reuse.
• Jones, L., & Achilli, A. (2017, February). California's Desalination Amendment: Opportunities from the colocation of desal facilities with wastewater treatment plants. In AWWA/AMTA 2017 Membrane Technology Conference & Exposition.
• Jones, L., & Achilli, A. (2016). A module-scale computational fluid dynamics model to evaluate hybrid osmotically-driven desalination systems. In 26th Annual Meeting of the North American Membrane Society, NAMS 2016.
• Murphy, J., Rowe, J., & Achilli, A. (2016). The validation of a stepwise model of direct contact membrane distillation for large-scale applications. In 26th Annual Meeting of the North American Membrane Society, NAMS 2016.
• Zirkel, G., Villanueva, J. L., & Achilli, A. (2016). Exploring water reuse with a novel FO-DCMD hybrid membrane process. In 26th Annual Meeting of the North American Membrane Society, NAMS 2016.
• Achilli, A. (2014). Integration of reverse osmosis and pressure retarded osmosis to decrease energy expenditures in seawater desalination. In AWWA/AMTA 2014 Membrane Technology Conference and Exposition.

Presentations

• Achilli, A. (2017, May). Integrated membrane processes for water reuse and desalination. Workshop: Water Reuse Monitoring and Treatment Technologies.
• Achilli, A., & Hiibel, S. R. (2017, November). A Fully Integrated Membrane Bioreactor System for Wastewater Treatment in Remote Applications. Wastewater treatment technology project meeting (environmental restoration program area), SERDP-ESTCP Symposium 2017.
• Ahmadiannamini, P., Furtaw, N. M., Murphy, J. P., Morrow, C. P., Achilli, A., Marchand, E. A., Childress, A. E., & Hiibel, S. R. (2017, August). An integrated membrane pilot system for direct potable reuse. ICOM 2017.
• Furtaw, N. M., Ahmadiannamini, P., Morrow, C. P., Murphy, J. R., Dash, S., Park, C., Achilli, A., Childress, A. E., Hiibel, S. R., & Marchand, E. A. (2017, April). Application of a submerged forward osmosis membrane bioreactor paired with membrane distillation utilizing waste heat. 2017 Nevada Water Environment Association Annual Conference.
• O'Toole, G., & Achilli, A. (2017, August). Optimizing operating parameters for minimum net energy consumption in a pilot-scale SWRO-PRO system. ICOM 2017.

Poster Presentations

• Childress, A. E., Achilli, A., Hiibel, S. R., Marchand, E. A., & Park, C. (2017, November). A Fully Integrated Membrane Bioreactor System for Wastewater Treatment in Remote Applications. SERDP-ESTCP Symposium 2017.