Andrea Achilli

Interests

Research

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

Teaching

Environmental EngineeringWater and Wastewater TreatmentPhysicochemical ProcessesMass and Heat Transfer

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
• 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., 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, 103761.
• 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, 116241.
• 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, 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.
• 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., O'Toole, G., & Achilli, A. (2021). Evidence of solution-diffusion-with-defects in an engineering-scale pressure retarded osmosis system. Journal of Membrane Science, 119135.
• 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.
• 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, 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.
• 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).
• 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.
• 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.
• 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.
• Achilli, A. (2013). Standard Methodology for Evaluating Membrane Performance in Osmotically Driven Membrane Processes. Desalination.
• 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, 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. (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. (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., & 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.
• 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.