Grantee Research Project Results
2012 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, 2012 through December 31,2012
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 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.
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) select and 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:
A conceptual model for the selection of hybrid sorbents using a ternary plot has been developed, where the required sorption capacity for up to three co-occurring pollutants can be plotted and used to guide selection of new sorbent media. Initially the mixture of arsenic and hexavalent chromium in groundwater was selected to investigate techniques for simultaneous removal of these pollutants because the reported mechanisms are quite different. Existing, commercially available metal oxide media used for arsenic removal, weak base anion exchange medial used for hexavalent chromium removal and a hybrid ion exchange media (HIX) impregnated with iron for arsenic removal. Experiments were conducted in buffered distilled water, NSF challenge groundwater and a groundwater from a community in California all with consistent results. The arsenic sorption media removed arsenic well, but hexavalent chromium poorly and vice versa for the weak base anion exchange (WBAX) resin. The HIX media worked achieved moderate removal of arsenate and hexavalent chromium. This provided proof of concept for the potential marketability of HIX general. A pilot test of the existing commercially available material was performed, but unfortunately achieved rather poor performance of hexavalent chromium removal using the commercially available HIX designed for arsenic removal compared against the WBAX. Now, HIX using WBAX has been impregnated with nano-iron in the hopes of achieving high arsenic and hexavalent chromium removal. New non-spherical designs of ion exchange media that might provide additional functionality are also being explored which may be more easily tailored with nano-iron. Quality Assurance documents were prepared and all appropriate measures are being monitored.
Methods for inexpensive synthesis of Titanium Dioxide impregnated Granular Activated Carbon (Ti-GAC) and Titanium dioxide impregnated hybrid ion-exchange media (Ti-HIX) have been developed. Currently, activities related to Ti-GAC characterization, synthesis optimization, and performance evaluations for simultaneous removal of arsenic and model organic contaminant are conducted. In parallel, batch and short bed column testing is being conducted with the Ti-HIX media to assess its performance in removal weak (arsenic, phosphate) and strong (nitrate) oxy-anions from water.
Hybrid media has been produced using biochar created by fast pyrolysis or gasification of black spruce or commercial wood pellets to remove fluoride, arsenic and disinfection by-product precursors. Testing for the wettability of the material and leaching potential of organics from the biochar have been conducted. Based upon the synthesis procedures, it appears possible to create biochar suitable for drinking water applications. Small scale column tests using crushed biochar are now beginning to be operated to assess the sorption and release of disinfection by-product precursors. Batch tests are underway to identify sorption rate and sorption equilibrium capacity. Furthermore, post-pyrolysis/gasification preparation techniques are being assessed to limit the release of polar pyrolysis products.
The team has intensively pursued collaboration with a native American community for installation of a proof-of-concept / pilot test in southern Arizona. Presentations have been made to various councils and documents provided for review. Approvals were making good progress, until an unexpected non-technical line of question arouse related to intellectual property. If the native American community allowed testing with their water or on their lands, then they wanted partial ownership of the intellectual property (IP). The IP was not just to license the produced material, but to benefit from any royalties related to the tested material. We are attempting to work through this issue with our institutional lawyers, but confirms the premise of this project that the stakeholders believe there is significant economic potential for new treatment processes targeting small, rural drinking water systems. Similarly, efforts are on-going in Alaska to pilot test the biochar system in a point-of-use application in a native community. The team has made strong inroads with the Alaskan Native Tribal Health Consortium (ANTHC) that currently installs full-scale water and wastewater systems in these communities. It is anticipated that a system will be installed during the late second year or during the third year of this study.
Future Activities:
The project is progressing as scheduled. Several hybrid ion exchange, granular activated carbon and biochar media are currently being synthesized and tested. The suitability of several on-line monitors for groundwater pollutants are being assessed and hopefully one will be purchased by late summer 2013.
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, southwestProgress 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.