Grantee Research Project Results
2013 Progress Report: Sustainable Sorbents and Monitoring Technologies for Small Groundwater Systems
EPA Grant Number: R835175Title: Sustainable Sorbents and Monitoring Technologies for Small Groundwater Systems
Investigators: Westerhoff, Paul , Hristovski, Kiril D , Dotson, Aaron
Institution: Arizona State University , University of Alaska - Anchorage
EPA Project Officer: Packard, Benjamin H
Project Period: December 1, 2011 through November 30, 2015
Project Period Covered by this Report: January 1, 2013 through December 31,2013
Project Amount: $500,000
RFA: Research and Demonstration of Innovative Drinking Water Treatment Technologies in Small Systems (2011) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Objective:
Because groundwaters frequently serve as water supplies for many small systems throughout the United States, we focus on inorganic (arsenic, chromium, nitrate, fluoride) and organic chemicals (total organic carbon (TOC) as a precursors for disinfection by-products, herbicides) that ubiquitously occur in groundwaters, pose health hazards to residents served by small systems, and/or have recent regulatory significance. Small systems increasingly have to address treatment of multiple pollutants in groundwater, and therefore we approach this challenge as a simultaneous compliance issue of pollutants in groundwater. Goals for this project have not substantively changed from those originally proposed.
The goal is to develop innovative treatment and monitoring technologies for small drinking water treatment systems to remove common groundwater constituents in extreme environments which can then be applied to other locations. Working in two extreme environments (Arizona and Alaska) with challenging local issues allows our findings to be applied to other locations throughout the USA. The project has three research objectives: (1) develop innovative and sustainable treatment technologies to remove mixtures of inorganic (arsenic, chromium, nitrate, fluoride) and/or organic (TOC, herbicides) pollutants from groundwater; (2) demonstrate lab-scale approaches for testing and comparing innovative treatment technologies for use by small systems; and (3) demonstrate simple spectrometric on-line monitoring systems capable of multi-parameter sensing capable of supporting remote operation and optimization of groundwater sorbent treatment systems.
Progress Summary:
In Year 1 we found that hybrid ion exchange (HIX) media had high potential for simultaneously removing multiple pollutants from groundwater, but that commercial sorbents did not perform well at low environmentally relevant concentrations. Thus, in Year 2 we focused on HIX media with high capacity for multiple pollutants at low concentrations. HIX using ferric hydroxide or titanium dioxide/oxide have been created using strong-base and weak-base ion exchange resins plus granular activated carbon and biochar. We developed a novel microwave-based synthesis method for some of these, that significantly reduces waste and energy requirements.
The new HIX materials have been characterized using surface area analysis, water and metal content, energy dispersive x-ray (EDX) for elemental mapping, and scanning electron microscopy for particle form and location. HIX sorbent performance has assessed in batch and column tests using deionized water or challenging synthetic groundwater matrices spiked with multiple pollutants at low environmentally relevant concentrations. Results show that metal oxide nanoparticle addition to a sorbent can augment the capacity to sorb an additional pollutant without sacrificing the starting capacity for the original target pollutant. A means to quantify HIX performance to remove multiple contaminants has been developed, and termed the “Simultaneous Removal Score”. The impact of these findings is to small systems that are currently using one of the parent resins for treatment of a specific pollutant. These systems can now add treatment for another pollutant of concern while still using the same capital equipment and operation.
In Year 1, preliminary testing of biochar produced by gasification and pyrolysis using commercial wood pellets produced mixed results on contaminant remove. Fluoride was not removed, but achieved approximately 30% removal of dissolved organic carbon (DOC) at a biochar dose of 100 mg/L. Initially pyrolysis created char was not suitable for evaluation as significant DOC leaching was observed. This issue was likely due to biochar coking during pyrolysis process exacerbated by lack of a gas sweep flow to convey the smoke from the reactor. In Year 2, modifying the pyrolysis system with argon sweep gas flow control led to enhanced smoke removal and notably less condensation and biochar coking in the reactor. Four biochars were created from pelletized white spruce sustainably harvested and produced in Alaska by Alaska Pellet Mill (Delta Junction, AK). These chars included short (5 min) and long (84 min) residence times at 450 °C and 550 °C in an auger fed heated fixed-bed reactor with a gas sweep flow of 10 SCFH of argon. Produced chars were then ground and dry sieved to 100 x 200 mesh (at least 75% passing the 100 mesh). This material was subsequently wet sieved to remove fines and ash. It was apparent during wet sieving through periodic measurement of rinse water conductivity dissolved ions were being washed from the biochar and their tendency to be washed from the char was influence by pyrolysis conditions. These washed chars were subjected to post-pyrolysis-preparation to either stabilize the surface organics or remove them. Post-pyrolysis-preparation techniques explored have been lab grade water, 1 M NaCl, 1 M NaOH, 1 M HCl, freeze/thaw and 1:6 toluene/methanol. This prepared biochars are being characterized to glean their potential for application in drinking water. The most suitable post-pyrolysis-prepared chars will then be evaluated using NSF challenge water in small scale column tests in the laboratory mimicking operation conditions of a point-of-use treatment device.
Additionally, during the summer of 2013 three black spruce trees were harvested, bark removed, chipped, then ground. While of the same species, these three trees were affected by different events during their life. One tree was harvested under healthy conditions, one tree was harvested that had previously died from a forest fire and one tree was harvested that had previously died due to bark beetle infestation. These trees will be evaluated in the coming year for the character of char produced and how the produce product is influenced by growth environment. We anticipate processing these trees using a top-lit updraft gasifier to produce a low yield produce with low concentrations of surface organics.
Researchers on this project have participated in an educational outreach event aimed at informing elementary school teachers about the value of clean drinking water and the challenges faced in small communities. A booth was hosted in conjunction with collaborators at Arizona Water and Value of Water Coalition at the Arizona Forward Earthfest Educators Night on October 29th, 2013 in Phoenix, Arizona. Over 100 teachers were presented with valuable drinking water information to share with many young students.
Challenges encountered during this period include collaboration with a native American community in Arizona as well as obtaining online spectrophotometric monitoring equipment. Presentations were made with clear goals outlined at multiple public meetings in various levels of government at the native American community. Initially support for testing the HIX media at a contaminated well in one town was supported by the community and the district, but then support was withdrawn at the federal level due to questions about intellectual property of the developed sorbents and royalties associated with possible future commercial viability. While negotiations continue, approval to perform the testing in the planned venue is now unlikely within the timeframe of this project. New collaborative relationships have been established with Arizona American Water company, a private local water utility which operates multiple wells with multiple pollutant contamination. Pilot testing may be performed with them starting summer 2014.
We have made progress on developing novel sensors. Single-particle ICP-MS is now being used to monitor for corrosion products in drinking water distribution systems. Additionally, use of isotopes to monitor copper in a small system has been explored to find drinking water derived inputs of copper into the wastewater collection system in a system struggling to meet copper discharge regulation (Girdwood, AK).
All other expenditures to date are on largely on track with projected budget.
Quality Assurance documents were prepared and all appropriate measures are being monitored.
Future Activities:
The project is progressing as scheduled. We are attempting to develop a cooperative agreement with EPA researchers to expand the impact of our work by performing column tests with additional waters and testing our new analytical techniques to track corrosion by-products. While high-tech monitoring of water quality parameters is an exciting market, our team has identified that monitoring tools may not be the most appropriate devices for very small water systems to use and understand or maintain. Linked other efforts outside this project that have been working on stand-alone monitoring devices for civil infrastructure, we anticipate adapting these devices to measure basic aspects in small water systems (e.g., pressure, flow, pump status, tank level, temperature and potentially some chemical parameter (i.e., pH, conductivity, or ORP). These monitoring devices will utilize open-source hardware and plans be made available freely upon completion. These tools have the opportunity to bring technology and online monitoring to a small treatment plant for ideally less than $150 per sensor without any network fees or contracts (using Google Drive to aggregate and publish data). Discussion is on-going with a consulting firm about potential to install these at a small system recently upgraded located in a remote part of the Cook Inlet off the road system. A sustainability analysis by life cycle environmental impact of the hybrid resins will be conducted. The current work is being incorporated into multiple peer reviewed journal papers. Graduate students being funded by this project are expected to achieve significant educational milestones within the next year, including a masters thesis defense and doctoral proposal defense.
Journal Articles:
No journal articles submitted with this report: View all 24 publications for this projectSupplemental Keywords:
Drinking water, chemicals, VOC, volatile organic compounds, organics, nitrogen oxides, innovative technology, oxidation, engineering, environmental chemistry, southwest, nanoparticlesProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.