Grantee Research Project Results
2014 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: December 1, 2013 through November 30,2014
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 USA, we focus on inorganic (arsenic, chromium, nitrate, fluoride) and organic chemicals (total organic carbon (TOC) as a precursor 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.
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 then can 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:
- Develop innovative and sustainable treatment technologies to remove mixtures of inorganic (arsenic, chromium, nitrate, fluoride) and/or organic (TOC, herbicides) pollutants from groundwater;
- Demonstrate lab-scale approaches for testing and comparing innovative treatment technologies for use by small systems;
- Select and demonstrate simple spectrometric on-line monitoring systems capable of multi-parameter sensing, supporting remote operation, and optimization of groundwater sorbent treatment systems.
Progress Summary:
This year has seen the development of multiple hybrid sorbents as these demonstrated great potential to simultaneously remove multiple pollutants. These hybrid sorbents may have a parent material made of weak base ion exchange (WBAX) good for chromium removal, strong base ion exchange (SBAX) good for nitrate or phosphate removal, or organic material (GAC, biochar) good for organic pollutant removal. These are made hybrid by the addition of metal nanoparticles like iron or titanium, which are good for arsenic removal. Each created sorbent has been characterized and performance tested to understand the creation process and its connection to performance. Typical characterization tests include digestion for metal content and analysis for total surface area and pore size distribution. Typical performance testing included batch equilibrium testing, short bed adsorber tests, and packed bed column testing.
One developed sorbent aimed to remove chromium and arsenic. An outcome of the described protocol has been to optimize the sorbent recipe. This optimization included exploration of four parent WBAX resins, comparison of iron impregnation against titanium impregnation, concentration of metal precursor solutions, and requisite heating hydrolysis time. After characterization and performance testing, it was found that impregnation of the metal into the WBAX can add a high affinity and capacity for arsenic without substantial loss in capacity for chromium. Further, we found that a high metal precursor concentration used during the sorbent synthesis did cause an increased metal content of the finished sorbent. However, this did not correlate to a higher surface area or to a higher pollutant removal capacity. This indicates that the metal can clog the sorbent pore structure and interfere with water treatment. The outcome of this set of experiments has been a synthesis method that is optimized for water treatment of both chromium and arsenic.
Several other hybrid sorbents using ion exchange, granular activated carbon and biochar also have been synthesized and tested. For example a hybrid titanium–anion exchange resin has been synthesized for phosphate selectivity. Biochar was synthesized using corncob material. It currently is being characterized and tested for sorption of model chemicals (methyl red and methylene blue). Additionally, a novel synthesis method using microwave heating for Ti-HIX and Ti-GAC media was developed and media were synthesized; the media currently are being characterized.
To quantify the environmental impacts and the sustainability of the developed sorbents, a preliminary life cycle assessment framework has been developed. A life cycle inventory of a hybrid resin has been gathered using real data from the optimized synthesis protocol. Impacts associated with the use of the sorbent have been estimated using the EPA’s Tool for the Reduction and Assessment of Chemical Impacts (TRACI). The outcome of this study has been to optimize the synthesis protocol not just for pollutant removal but also for all environmental impacts associated with its deployment. This model will be further developed but we hope this is effective in informing the water industry of larger impacts associated with the use of any treatment technology.
The suitability of several on-line monitors for groundwater pollutants is being assessed. We have begun utilizing open-source hardware and software to make our modular low power sensor for measurement of conventional water treatment parameters. A bridge mounted creek depth and temperature sensor has been installed near the UAA engineering building. The installed device measures distance from the sensor to the water with an ultrasonic sensor and air temperature with a thermistor. Each of these sensors take three measurements every 22 minutes, averages them, and stores the values. Every 4 hours the sensor sends the data via text. We store all collected data in a spreadsheet for record keeping. This sensor operates on only four standard AA batteries. The outcome of this demonstration is that semi-real time sensor data can be managed remotely at a low cost of energy and time.
The educational impacts of this project are continuing with multiple students nearing completion of their graduate degrees. Liena Murdoch, has completed creating and performing analytics on pyrolysis prepared biochar. Another student, Michael Cliggett, has finished preliminary testing to illustrate the capacity for gasified biochar to quench chlorine; he also has presented our work and has prepared what is needed to perform small-scale column tests with our biochar. Mac Gifford is a fourth year doctoral candidate synthesizing sorbents and optimizing pollutant removal performance and environmental impact.
Quality Assurance documents were prepared and all appropriate measures are being monitored.
Future Activities:
The project is progressing as scheduled. Over the next year we expect to complete further testing of the multiple sorbents that have been developed. This will include batch testing and short bed column testing. It will include a variety of waters such as groundwater and standard challenge water, for which we expect the sorbents to have lower but more realistic capacity. We also plan to conduct regeneration experiments on the synthesized sorbents to assess the regeneration potential for multiple pollutants.
We expect to continue to develop innovative sorbents capable of multiple pollutant removal. One is a hybrid titanium–ion exchange resin capable of enhanced fluoride removal. This will be done by an undergraduate student to enhance the educational impact associated with this project. Another will evaluate three parent trees for biochar character difference (fresh, fire burned, and beetle kill). A third will use in-situ gasification for titanium modified biochar.
While we have made a number of public presentations this year regarding this project, we expect a number of publications over the next year headed up by several graduate students supported by this project. Mac Gifford will submit an evaluation of commercial media for simultaneous removal, and another describing the mechanism of nanoparticle impregnation for hybrid media. Liena Murdoch is preparing a paper for submission to Water Research for biochar characteristics after post-pyrolysis preparation. Michael Cliggett will be preparing a paper for submission to Water Research on chlorine quenching by gasified biochar.
Journal Articles:
No journal articles submitted with this report: View all 24 publications for this projectSupplemental Keywords:
Drinking water, chemicals, VOC, organics, nitrogen oxides, innovative technology, oxidation, engineering, environmental chemistry, southwest, water monitoring;Progress 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.