Source: The Regents of University of California submitted to
RECOVERY OF NITROGEN, PHOSPHORUS, ENERGY AND WATER FROM FOOD PROCESSING WASTEWATER USING ELECTROCHEMICAL MEMBRANE BIOREACTORS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
1014012
Grant No.
2017-67022-26135
Cumulative Award Amt.
$480,843.00
Proposal No.
2016-08036
Multistate No.
(N/A)
Project Start Date
Feb 15, 2017
Project End Date
Jul 14, 2021
Grant Year
2017
Program Code
[A1531]- Biorefining and Biomanufacturing
Project Director
Wheeldon, I.
Recipient Organization
The Regents of University of California
200 University Office Building
Riverside,CA 92521
Performing Department
Chem & Environ Engineering
Non Technical Summary
This project will produce fundamental scientific knowledge and engineering innovations to enable the recovery of high-quality water, nutrients (nitrogen (N) and phosphorus (P)), and energy from agricultural wastewater. We propose to characterize, for the first time, the speciation and fate of N- and P-containing molecules during anaerobic electrochemical membrane bioreactor (AEMBR) treatment. With this knowledge we will be able to integrate AEMBR processes to realize our long-term vision of developing highly efficient engineering systems capable of transforming concentrated waste streams to fertilizer, energy, and clean water. In this research project, we will (1) Develop and optimize integrated AEMBR systems using novel electrically conductive membrane electrodes tailored for different applications for the combined recovery of clean water (membrane permeate), liquid fertilizer (membrane retentate), and energy (biogas, H2, electricity). (2) Use a system approach to understand the transformation of N and P as they pass through the AEMBR system, and evaluate how the different forms interact with the electrically charged membrane surface, so the formation and recovery of nutrient containing chemicals can be optimized. (3) Investigate the interactions between carbon, nitrogen, phosphorus, and electron cycles within the AEMBR system using real waste streams, generated from food processing activities, to guide system development.This project addresses the Bioprocessing and Bioengineering program's priority of advancing or expanding the utilization of waste and byproducts generated in agricultural and food systems, as well as engineering new or improved products and processes that make use of materials from agricultural origin.
Animal Health Component
25%
Research Effort Categories
Basic
50%
Applied
25%
Developmental
25%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
40253702020100%
Knowledge Area
402 - Engineering Systems and Equipment;

Subject Of Investigation
5370 - Sewage and waste disposal facilities and systems;

Field Of Science
2020 - Engineering;
Goals / Objectives
Our long-term goal is to develop highly efficient engineering systems capable of transforming concentrated waste streams to fertilizer, energy, and clean water. This project is based on the central hypothesis that reducing the amount of nitrogen and phosphorous bound to DOM in AEMBR reactors will increase both nutrient recovery in the membrane system and energy production. The rationale behind this project is that increasing the amount of bio- and electrochemically-available nitrogen and phosphorous in agricultural waste streams will enhance energy production and nutrient recovery from AEMBR systems, enhancing agricultural sustainability while reducing the environmental burden of current treatment processes. We intend to test our hypotheses, listed below, by pursuing the following specific Objectives:Objective 1. Develop electroactive membrane materials for water, gas, and nutrient separation and recovery (UC Riverside (UCR))Objective 2. Integrate electroactive membrane materials into AEMBRs and demonstrate capability of converting concentrated waste streams to fertilizer, energy and clean water (UC Boulder (UCB) and UCR)Objective 3. Identify and characterize N- and P- containing species in the different stages of the AEMBR treatment train (Cal State University East Bay (CSUEB))
Project Methods
Ultrafiltration MembranesAqueous suspensions of these CNTs will be prepared by sonicating 0.1 mg CNTs/ml of deionized water (DIW) in the presence of an ionic surfactant [39, 58, 59, 61]. The CNT suspension will then be pressure-deposited onto a commercially available polysulfone UF membrane (NanoStone, Oceanside, CA), and rinsed with DIW to remove any residual surfactant. To increase the electrical conductivity of the CNT network, we will use two established methods to horizontally align the CNT network. In the first method, we will use an electrical field generated between two aluminum electrodes placed on either side of the deposited CNTs; CNTs have been demonstrated to align along the electrical field lines [68, 69]. In the second method, we will utilize electrostatic forces generated between a moving sheet of aluminum foil and the deposited CNTs, which align the CNTs in the direction of the foil motion [70]. To cross-link the CNTs and further enhance the electrical conductivity, we will electropolymerize conducting polymers (polyaniline or polypyrrole) onto the CNT network. Here, the CNT-coated UF membrane will be soaked in an acidic solution containing H2SO4 and monomer (aniline or pyrrole) [71]. The CNTs will be connected to a potential source (as anode), and a titanium plate will be used as a counter electrode (cathode). The reaction time and potential will be varied with the goal of creating an electrically conducting CNT/polymer porous film.Gas Separation MembranesThe electrically conductive coating will be fabricated based on the method described in Objective 1. For the hydrophobic support, we will test a range of commercially available hydrophobic MF membranes, e.g. PTFE polypropylene and PVDF. To reduce the probability of liquid water intrusion through the hydrophobic membrane, different pore sizes of the hydrophobic membranes will be tested, as it has been demonstrated that smaller membrane pore sizes reduce the passage of liquid water through hydrophobic materials during pressurized MD processes [75]. The conductive and hydrophilic CNT/conducting polymer coating will be fabricated in a manner similar to that described in Section 3.1.1. To increase the electrocatalytic properties of the membranes, we will electrochemically decorate the conducting membrane surface with metallic NPs [57]. In this method, the membrane, acting as a cathode, is immersed into a solution of metal salts, with a titanium wire acting as the counter electrode. The electrode pair (and a reference Ag/AgCl electrode) are connected to a power supply providing constant current conditions; when sufficient potential is applied, metal ions in the solution are reduced on the CNT surface, forming metallic NPs that are well attached. We will test a range of NP compositions that have been demonstrated to be effective at facilitating the hydrogen evolution reaction, including combinations of iron, molybdenum, and nickel [57, 76]. To keep the process economically viable, we will avoid using precious metals such as platinum.NF membranesElectrically conducting NF membranes will be fabricated by modifying our previously published method [39, 40]. The process begins by depositing a CNT suspension on a UF support (see Section 3.1.1). Then, the membrane is dipped into a 2% aqueous solution of polypiperazine, slightly dried, immersed into a 0.15% solution of trimesoyl chloride in Isopar G, and finally dried at 90°C and stored in DIW.Anaerobic MBRs Since all the membranes will be in flat sheet configuration, we will use them as tubular separators and cathodes. Carbon brushes will be used as the anode to ensure sufficient surface area and electron supply through anodic oxidation, so the cathode properties can be characterized without anode limitations. Both synthetic and actual wastewater samples will be used in the systems. For gas separation membrane AEMBRs, we will compare gas production rates between passive diffusion and active harvesting. Traditional passive gas diffusion in MxCs and AnMBRs leads to multiple problems, including low production rate, dissolved methane in solution, and H2 consumption by methanogens. By using active gas harvesting via the new membranes, where an intermittent vacuum or pressure difference is applied to drive gas out of the solution, high rate gas production has been accomplished, fouling is expected to be mitigated, and gas purity can be improved. We can also choose to produce H2 or CH4 by changing retention time, applied potential, and harvesting methods.Membrane properties and fouling will be characterized using a suite of advanced analytical techniques in addition to operating data such as ion removal, COD degradation, pH, conductivity, ORP, and power production in the reactors. Inorganic scales will be probed by X-ray diffraction (XRD), and organic fouling and membrane deterioration will be characterized by attenuated total reflection Fourier transform infrared spectrometer (ATR-FTIR). Foulant deposition and change of surface morphology will be characterized through environmental scanning electron microscopy (ESEM). Biofilm formation will be stained using LIVE/DEAD staining and analyzed using confocal scanning laser microscope (CSLM). Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) will be performed to characterize the conductive membrane electrochemical performance under different conditions.N and P TransformationsSolution analysis (UCR and UCB) A suite of standard analytical techniques will be used to characterize N and P in the solution phase at different points in the reactor. Total N, total P, nitrate-N, ammonium-N, and inorganic P will be measured using standard analytical methods (Standard Method 4500-P, 4500-NH3, 4500-Norg, 4500-NO3), and a total nitrogen analyzer (OI Analytical) [79]. Organic P and N will be estimated by calculating the difference between total P and inorganic P, and total N and inorganic N, respectively.3.3.2 Solid phase analysis (CSUEB) Solid P pools will be characterized generally by chemical extraction/dissolution/hydrolysis followed by solution analysis, as described above. This will provide estimates of total N, total P, nitrate-N, ammonium-N, inorganic P, and organic P and N. Water content will also be estimated. In addition to this general, pool-based aqueous chemistry approach, samples will be collected from various points in the reactor, and dried for synchrotron analysis. XANES spectroscopy will be used to directly investigate P and N speciation and transformations in the solid phase. For P speciation, sample preparation is minimal: bulk measurements are conducted on finely-ground, homogenized powder painted on ultra-low impurity carbon tape. Micro-scale measurements (generating images of P distribution with a pixel size of 2-10 micrometers, and P speciation of spots ~2 micrometers in diameter) are obtained from cut and lightly polished heterogeneous solid samples encased in epoxy. Speciation of N is more challenging due to the low X-ray energies involved, which necessitates the use of vacuum; preparation of samples for N analysis will be performed in consultation with the beamline scientists, according to the specific needs of the beamline in question (e.g., beamline 5.3.2.2 at ALS, Lawrence Berkeley National Laboratory).

Progress 02/15/17 to 07/14/21

Outputs
Target Audience:The work targeted stakeholders that work on waste stream management, including agricultural and food processing wastewater treatment systems. The technologies developed enabled nutrient recovery from wastewater which increased the value proposition of the treatment process and enabled new market development. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A postdoctoral scholar and a graduate student weresupported by this project. The researchersreceived interdisciplinary trainings by working with the PIs and have been productive in research. How have the results been disseminated to communities of interest?The subaward PI developed a new course called ENE321 Resource Recovery for a Circular Economy, which was the first class on circular economy at Princeton University. Students not only learn state-of-the-art technologies and processes that enable a circular economy, they also participate in lab activities and visit companies that practice resource recovery. In addition to perform lab research, give conference presentations, and publish research articles to disseminate our findings to the community. The group also reached out to companies that may have interest in technology development and explored entrepreneurship opportunities. The presentation from this work include: Ren, et al. Novel Electroactive Membranes for Resource Recovery, The 8th International Symposium on water Environment Systems, Tohoku University (online), November 8th, 202 Ren, et al. Using Low-Cost Renewable Energy for Waste Resource Recovery, MIT A+B 2020 Conference, MIT (Online), August 13-14th, 2020 Ren, et al. Wastewater Treatment for Carbon & Nutrient Valorization, ACS 2019 Spring National Meeting, Orlando, March 31- April 4, 2019. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? The reserach in this projectworked towaerd anaerobic nutrient removal and recovery from wastewater and sludge using novel microbial electrochemical processes. Recently we have made great progress on developing electroactive membranes to recover ammonia in situ from digestion centrate and other waste streams, and we developed novel natural wood-based membranes to enable clean water production. We also studied extensively on how to use electrochemical tuning to regulate product distribution in electrofermentation that allow us to produce high value VFAs and other products compared to biogas. In addition, this project developed membranes for the specific extraction of ammonia and phosphate from waste stream. The ammonia extraction membranes were based on the use of electroactive porous hydrophobic materials, where water electrolysis at the membrane/water interface increased the local pH, converted ammonium to ammonia, and enabled the transport of pure ammonia across the membrane at high efficiency and low energy consumption. Phosphate extraction membranes were fabricated by growing MnO2 nanoparticles inside cation exchange membranes. The MnO2 particles provided a pathway specific for phosphate to cross the membrane (a result of specific outer-sphere interactions between phosphate and MnO2), while the fixed negative charges in the ion exchange polymer rejected the passage of other anions. The result is the production of nearly pure phosphate from a mixed ion stream.

Publications

  • Type: Journal Articles Status: Published Year Published: 2020 Citation: Iddya, A.; Hou, D.; Miang, K. C.; Ren, Z. J.; Tester, J.; Posmanik, R.; Gross, A.; Jassby, D., Efficient Ammonia Recovery from Wastewater using Electrically Conducting Gas Stripping Membranes. Environmental Science: Nano 2020
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Dianxun Hou, A. I., Xi Chen, Mengyuan Wang, Wenli Zhang, Yifu Ding, David Jassby, and Zhiyong Jason Ren, Nickel Based Membrane Electrodes Enable High Rate Electrochemical Ammonia Recovery. Environmental Science & Technology 2018, 52, (15), 8930-8938
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Hou, D., Jassby, D., Nerenberg, R., Ren, ZJ. Hydrophobic Gas Transfer Membranes for Wastewater Treatment and Resource Recovery, Environmental Science & Technology, 2019, 53, 20, 11618-11635.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Hou, D., Li, T., Chen, X., He, S., Dai, J., Mofid, S.A., Hou, D., Iddya, A., Jassby, D., Yang, R. and Hu, L., Ren, ZJ. Hydrophobic nanostructured wood membrane for thermally efficient distillation. Science Advances, 2019. 5(8), eaaw3203.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Hou, D., Iddya, A., Chen, X., Wang, M., Zhang, W., Ding, Y., Jassby, D., Ren ZJ. Nickel Based Membrane Electrodes Enable High Rate Electrochemical Ammonia Recovery, Environmental Science & Technology, 2018, 52 (15), 89308938
  • Type: Journal Articles Status: Submitted Year Published: 2021 Citation: Arpita Iddya, Piotr Zarzycki, Ryan Kingsbury, Charmaine Khor, Shengcun Ma, Jingbo Wang, Ian Wheeldon, Zhiyong Jason Ren, Eric M. V. Hoek, David Jassby; A Reverse-Selective Ion Exchange Nanocomposite Membrane: Selective PhosphateRecovery via an Outer Sphere Complexation-Diffusion Pathway


Progress 02/15/20 to 02/14/21

Outputs
Target Audience:The work targeted stakeholders that work on waste stream management, including agricultural and food processing wastewater treatment systems. The technologies developed enabled nutrient recovery from wastewater which increased the value proposition of the treatment process and enabled new market development. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A postdoctoral scholar was partially supported by this project. Prior a full time PhD student was supported by the project. The students received interdisciplinary trainings by working with the PIs and have been productive in research. At UCLA, a graduate student was supported on this award. How have the results been disseminated to communities of interest?The subaward PI developed a new course called ENE321 Resource Recovery for a Circular Economy, which was the first class on circular economy at Princeton University. Students not only learn state-of-the-art technologies and processes that enable a circular economy, they also participate in lab activities and visit companies that practice resource recovery. In addition to perform lab research, give conference presentations, and publish research articles to disseminate our findings to the community. The group also reached out to companies that may have interest in technology development and explored entrepreneurship opportunities. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? This project worked toward anaerobic nutrient removal and recovery from wastewater and sludge using novel microbial electrochemical processes. Recently we have made great progress on developing electroactive membranes to recover ammonia in situ from digestion centrate and other waste streams, and we developed novel natural wood-based membranes to enable clean water production. We also studied extensively on how to use electrochemical tuning to regulate product distribution in electrofermentation that allow us to produce high value VFAs and other products compared to biogas. In addition, the team developed membranes for the specific extraction of ammonia and phosphate from waste stream. The ammonia extraction membranes were based on the use of electroactive porous hydrophobic materials, where water electrolysis at the membrane/water interface increased the local pH, converted ammonium to ammonia, and enabled the transport of pure ammonia across the membrane at high efficiency and low energy consumption. Phosphate extraction membranes were fabricated by growing MnO2 nanoparticles inside cation exchange membranes. The MnO2 particles provided a pathway specific for phosphate to cross the membrane (a result of specific outer-sphere interactions between phosphate and MnO2), while the fixed negative charges in the ion exchange polymer rejected the passage of other anions. The result is the production of nearly pure phosphate from a mixed ion stream.

Publications


    Progress 02/15/19 to 02/14/20

    Outputs
    Target Audience:During the last period of performance, we have presented our findings in departmental seminars (City University of Hong Kong, Ben Gurion University) and at a professional conference (ACS, NAMS). People attending the lectures were primarily scientists and engineers working on water treatment and membrane material development. Changes/Problems:Due to the Covid-19 global pandemic, all wet-lab research has been paused since Feburary 2020. During the stay-at-home orders, students and faculty have been working at home on data analysis and manuscript preparation. Due to this delay we will request a no cast extension so that the work can continue as planned. What opportunities for training and professional development has the project provided?Over the course of this project two graduate students have been trained in multidisciplinary reserach. How have the results been disseminated to communities of interest?During the last period of performance, we have presented our findings in departmental seminars (City University of Hong Kong, Ben Gurion University) and at a professional conference (ACS, NAMS). People attending the lectures were primarily scientists and engineers working on water treatment and membrane? What do you plan to do during the next reporting period to accomplish the goals?For objective 1 we will continue to develop membranes for the targeted extraction of phosphorus and volatile fatty acids from anaerobic digestion treating agricultural waste. For objective 2 all membranes will be integrated into anaerobic reactors treating real wastewater samples. For objective 3, we are continually evaluating the transformation of nitrogen and phosphorus species during anaerobic digestion. In addtion, we plan to continue dessminating our work through publication and professional conferences.

    Impacts
    What was accomplished under these goals? Objective 1: The research team has successfully applied electroactive membranes for the effective extraction of ammonia and hydrogen from anaerobic reactors. Membranes were optimized by electro-depositing a thin layer of nickel nanoparticles to the surface of the CNT membrane, which dramatically enhanced the electrical conductivity and transport properties of the membrane. The resulting membranes have been demonstrated to have the best performance, to date, in terms of ammonia extraction performance, both in terms of maximal ammonia flux and minimal energy consumption. Critically, these membranes have been applied to complex waste streams, and we are exploring methods to reduce the capital costs of these membranes by eliminating the use of ion exchange membranes in the process, which will also reduce process complexity and fouling. In addition to ammonia, we are in the middle of developing a membrane for the targeted extraction of phosphate from waste streams - this would be the first of its kind. Preliminary data shows the promise of our approach. However, the interruption of research due to the COVID-19 outbreak has temporarily stalled our work. On another front, recent reports (including from our team) have identified the potential of extracting volatile fatty acids (VFAs) from anaerobic digestors, as an alternative to letting the process proceed all the way to methanogenesis and methane production. Considering the low cost of methane (due to the abundance of natural gas), it is unlikely that biogas production will ever be economically viable. However, the generation and extraction of VFAs (which are formed earlier in the anaerobic digestion process, and serve as precursors to biogas production) addresses the waste management issue, as well as generates a valuable commodity. VFAs are desirable feed-stock for many bioprocesses, including for the production of bioplastics and alcohols. We have begun developing electrothermal membranes that can extract VFAs from complex waste stream, with very encouraging preliminary data. The results of these research efforts have yielded a review article published in 2019 in ES&T (Hydrophobic Gas Transfer Membranes for Wastewater Treatment and Resource Recovery), a manuscript describing how hydrophobic membranes suitable for resource extraction can be made from waste woody materials published in 2019 in Science Advances (Hydrophobic nanostructured wood membrane for thermally efficient distillation), and a manuscript published in early 2020 describing the optimization of ammonia extraction membranes, published in ES:Nano (Efficient Ammonia Recovery from Wastewater using Electrically Conducting Gas Stripping Membranes). Objective 2: All the membranes described in Objective 1 are continuously integrated into anaerobic MBRs, and tested for their performance. Importantly, we are exploring the integration of membranes without the use of commercially available (and expensive) ion exchange membranes that dramatically increase the capital costs of the process. Objective 3: We are determining the availability and quality of nutrients (N and P) in anaerobic reactors, as part of our ongoing analysis of membrane performance.

    Publications

    • Type: Journal Articles Status: Published Year Published: 2019 Citation: Hou, D.; Jassby, D.; Nerenberg, R.; Ren, Z. J., Hydrophobic Gas Transfer Membranes for Wastewater Treatment and Resource Recovery. Environmental science & technology 2019.
    • Type: Journal Articles Status: Published Year Published: 2019 Citation: Hou, D.; Li, T.; Chen, X.; He, S.; Dai, J.; Mofid, S. A.; Hou, D.; Iddya, A.; Jassby, D.; Yang, R., Hydrophobic nanostructured wood membrane for thermally efficient distillation. Science advances 2019, 5, (8), eaaw3203.
    • Type: Journal Articles Status: Awaiting Publication Year Published: 2020 Citation: Iddya, A.; Hou, D.; Miang, K. C.; Ren, Z. J.; Tester, J.; Posmanik, R.; Gross, A.; Jassby, D., Efficient Ammonia Recovery from Wastewater using Electrically Conducting Gas Stripping Membranes. Environmental Science: Nano 2020.


    Progress 02/15/18 to 02/14/19

    Outputs
    Target Audience:During the last reporting period with have primarily focused on disseminating our research through publications. Specifically, two manuscripts were published in peer-reviewed journals. In addition to these publications, presentations were made at an American Chemical Society meeting in Orlando, FL. in March of 2019. Changes/Problems:Both Drs. Jassby and Ren have recently moved institutions. Dr. Jassby is now at UCLA. Dr. Ren is now at Princeton University. The PI of the project is Dr. Wheeldon at UCR. What opportunities for training and professional development has the project provided?To date, two graduate students have been supported using this funds from this grant. How have the results been disseminated to communities of interest?Two manuscripts were published in peer-reviewed journals. Presentations were made at an American Chemical Society meeting in Orlando, FL. What do you plan to do during the next reporting period to accomplish the goals?Objective 1: Continue to optimize membrane materials, particularly in terms of electrical conductivity and catalytic properties (water electrolysis). Objective 2: Integrate water treatment (ultrafiltration) membranes into the biological reactor to simultaneously recover nitrogen and phosphorous.

    Impacts
    What was accomplished under these goals? Objective 1: The team has successfully fabricated hydrophobic, electrically conducting membranes, and used them to effectively recover NH3from a concentrated waste stream. The associated energy requirements were very low, and the membrane has the potential of radically transforming anaerobic treatment systems, by enabling the removal of nitrogen-bearing contaminants, which is a major limitation of this technology. The work on this objective has resulted in a publication in ES&T. A new class of hydrophobic membrane materials suitable for gas stripping were developed by transforming a natural wood substrate. The new membrane material exhibited excellent surface and transport properties, and because they are made from wood, represent a step-change in the way membrane materials are fabricated. This work resulted in a paper submitted to Science Advances. Objective 2: Gas separation membranes were integrated into biological reactors treating high-strength wastewater, and successfully used to recover ammonia. Objective 3: Co-PI Michael Massey (from Cal-State East Bay) quit the university, and is no longer involved in the project.

    Publications

    • Type: Journal Articles Status: Published Year Published: 2018 Citation: Hou, D., Iddya, A., Chen, X., Wang, M., Zhang, W., Ding, Y., Jassby, D., Ren ZJ. Nickel Based Membrane Electrodes Enable High Rate Electrochemical Ammonia Recovery, Environmental Science & Technology, 2018, 52 (15), 89308938.
    • Type: Journal Articles Status: Accepted Year Published: 2019 Citation: Hou et al., Hydrophobic Nanostructured Wood Membrane for Thermally Efficient Distillation, Science Advances, 2019, accepted.


    Progress 02/15/17 to 02/14/18

    Outputs
    Target Audience:During the last period of performance, we have presented our findings in departmental seminars (Oregon State University, University of Washington), and at a professional conference (ICOM in San Francisco). People attending the lectures were primarily scientists and engineers working on water treatment and membrane material development. Changes/Problems:The PI of the project (Jassby), has recently moved to UCLA. As such, project funds are requested to be transfered to the new institution (from UCR to UCLA). The sub-contracts to Boulder and CSEB remain unchanged. What opportunities for training and professional development has the project provided?To date, two graduate students have been supported using this funds from this grant. How have the results been disseminated to communities of interest?Some of the results (membrane fabrication and characteriztion) have been shared at professional conferences (ICOM in San Francisco - August, 2017). What do you plan to do during the next reporting period to accomplish the goals?Objective 1: Continue to optimize memrbane materials, particularly in terms of electrical conductivity and catalytic properties (water electrolysis). Objective 2: Integrate water treatment (ultrafiltration) membranes into the biological reactor to simultaneously recver nitrogen and phosphorous. Objective 3: Begin characterizing N- and P-containing species using EXAFS.

    Impacts
    What was accomplished under these goals? Objective 1: The UCR group has successfully fabricated and characterized gas stripping and ultrafiltration membranes that can recover nutrients from concentrated waste stream. The membranes were characterized in terms of electrical conductivity and activity, transport properties, and surface and chemical properties. Membranes for gas stripping were fabricated by depositing a layer of carbon nanotubes (CNTs) on a hydrophobic porous support through a process of spray-coating, and were cross-linked using poly(vinyl alcohol) (PVA). Then, nickel/molybdate nanoparticles were grown on the surface of the CNTs using an electro-reduction process. In addition, in some iterations, a layer of conducting polyaniline (PANI) was grown electrochemically on the surface of the CNTs before the nanoparticles were grown. For liquid separation membranes, the same coating (CNT + PVA + PANI) was deposited on the surface of a hydrophilic support (polysulfone). Membranes werecharacterized using linear sweep voltammetry and cyclic voltammetry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, bubble point entry (for the gas separation materials), and surface hydrophilicity/hydrophobicity. Objective 2: Gas separation membranes have begun to be intergrated into biological reactors treating high-strength wastewater. In this first period of work, a potential was applied to the memrbane surface (with membrane as cathode) while a small vacuum was used as the driving force. As a result of the applied potential, hydroxide generation was facilitated along the membrane surface (due to water electrolycis). The elevated pH along the membrane leads to the transformation of ammonium in the wastewater to poorly-soluble ammonia, which is is readily stripped from the water into the membrane's permeate stream (due to the applied vacuum). Along witht he ammonia, hydrogen and water vapor also penetrate through the membrane (hydrogen is formed during the water electrolysis reaction). In the permeate stream, ammonia is re-disslolved back to ammonium, which leads to the a highly purified stream of ammonium hydroxide that can be used for multiple applications. The hydrogen (which is poorly soluble in water) can either be vented or harvested. Based on our preliminary data, we have demonstrated ammonium recovery rates equivalent to 36 g N/m2of membrane area at a current density of 4 A/m2?.

    Publications