SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM
PHYTOREMEDIATION OF ORGANICS ACTION TEAM
TCE IN GROUND WATER SUBGROUP
CONFERENCE CALL

November 24, 1999
1:00 p.m.–2:30 p.m.

On November 24, 1999, the following members of the Remediation Technologies Development Forum’s (RTDF’s) Phytoremediation of Organics Action Team, Trichloroethylene (TCE) in Ground Water Subgroup, met in a conference call:

Linda Fiedler, Environmental Protection Agency (EPA), Technology Innovation Office (TIO)
Milton Gordon, University of Washington
Lee Newman, University of Washington
Steve Rock, EPA
Keith Rose, EPA
Bob Tossell, GeoSyntec Consultants

Also present was Christine Hartnett of Eastern Research Group, Inc. (ERG).

INTRODUCTION

The TCE in Ground Water Subgroup is in the process of refocusing their goals and activities. Conference calls were held on October 13, 1999, and November 10, 1999, to discuss these topics. The latter call served as a brainstorming session; Subgroup members identified a draft mission statement, discussed the Subgroup’s organizational structure, and listed ideas for potential activities and areas of research. At the end of the November 10 conference call, Subgroup members agreed to hold another call on November 24, 1999, to refine some of their ideas. The proceedings from this call are summarized below.

MISSION STATEMENT

Keith Rose noted that the following had been recommended as a mission statement during the November 10, 1999, conference call:

Rose asked participants whether this mission statement was acceptable. Milton Gordon recommended broadening the contaminant classification to "halogenated solvents" so that bromated compounds are included under the Subgroup’s mission statement. Conference call participants discussed Gordon’s suggestion, but decided not to make any changes to the mission statement.

SUBGROUP ORGANIZATIONAL STRUCTURE

Subgroup members agreed that the Subgroup should be led by four co-chairs: Keith Rose, Bob Tossell, Milton Gordon, and Lee Newman. (Co-chairs were assigned so that all sectors participating in the Subgroup are represented. Rose represents the government. Tossell represents industry. Gordon and Newman, who plan to split their co-chairing responsibilities, represent academia.) In addition to having co-chairs, conference call participants agreed that a Steering Committee should be formed. Tossell recommending assigning seven to nine people to the Committee. Those who serve, he said, should be willing to promote phytoremediation studies, pool resources for research efforts, and advance the understanding of the scientific processes that underlie phytoremediation. Tossell asked conference call participants to send him names of potential Steering Committee candidates by the end of the year. He agreed to compile the names into one list and to distribute this to the Subgroup members. After the list is created, the Subgroup members will identify the most ideal candidates and will formally invite them to serve on the Steering Committee.

RESEARCH QUESTIONS

During the November 10 conference call, Rose said, the Subgroup identified six research questions that they wanted to address: (1) How effective is phytoremediation? (2) What role do plants and microbes play in the remedial process? (3) How are chemicals degraded and transported, and what is their eventual fate? (4) What kind of monitoring needs to be performed? (5) What analytical methods should be used? (6) What protocols should be used for bench-scale studies, pilot studies, and full-scale implementation?

Conference call participants revisited some of these questions and discussed them in greater detail. Much of the call was dedicated to determining the efficacy of phytoremediation. Major points from this discussion were:

• There are multiple ways to measure effectiveness. Conference call participants said that a technology’s efficacy can be measured by its ability to remove contaminants from a medium. When ground water is the medium being evaluated, however, it may not be possible to reduce contaminant concentrations if the remedial technology is located downgradient of the contaminant source. (If the source is not cleaned up, Tossell said, contaminants will continue to migrate to downgradient locations.) Newman and Gordon stressed that a ground-water technology may still be considered successful even if contaminant concentrations are not reduced. Success can be achieved, they said, if a technology can achieve hydraulic control so that contaminant migration is halted or curtailed. Conference call participants said that trees can be used to achieve hydraulic control. (Tossell likened trees to pumping wells, noting that the difference between the two is simply that the former are alive.)

• The Office of Solid Waste and Emergency Response (OSWER) directive on Monitored Natural Attenuation (MNA) may serve as a good model for evaluating phytoremediation’s efficacy. Tossell said that phytoremediation and MNA share some similarities. Elaborating on this point, he recommended, using the OSWER directive—which gives guidelines on when MNA is appropriate, including lines of evidence—as a model for evaluating phytoremediation’s efficacy. Tossell said that the OSWER directive outlines three lines of evidence that can be used to demonstrate the efficacy of MNA: (1) prove that there has been a reduction in contaminant concentrations, (2) document the presence and distribution of geochemical and biochemical indicators, and (3) use laboratory studies to show that the site contains microbes that can degrade contaminants. Tossell said that a phytoremediation’s efficacy could be assessed using a modified version of the OSWER directive. For example, he said, the paradigm could be made applicable to phytoremediation if (1) the second line of evidence is modified to incorporate an evaluation of hydraulic control, and (2) the third line of evidence is changed so that laboratory studies focus on plant uptake rather than microbial degradation. Steve Rock thought that Tossell’s suggestions made sense, noting that many regulators are already comfortable using the OSWER directive’s framework. Rose was inclined to agree, although he said that he would like to give the suggestion more thought before deciding whether to go forth with this approach. Linda Fiedler expressed interest in using the OSWER directive as a model, but cautioned participants against advertising phytoremediation as a technology that is very similar to MNA. Rose agreed that MNA and phytoremediation should be advertised as two distinct technologies, but stressed that some of the concepts used to assess MNA can be applied to phytoremediation.

• The goals for phytoremediation may differ across sites depending on whether the technology is used as a stand-alone treatment or as part of a treatment train. Conference call participants noted that phytoremediation can be used as a stand-alone treatment or in combination with other technologies. For example, Rose and Tossell said, some investigators are combining phytoremediation with MNA. Using this approach, they said, contaminant concentrations are reduced using phytoremediation and then MNA takes over and remediates the contaminants to levels that meet regulatory standards. When phytoremediation is used in combination with another technology, Tossell said, it is important to assess the overall efficacy of the entire treatment system as well as the efficacy of the individual technology components.

• Seasonal variability will impact effectiveness. For sites that are located in northern climates, Fiedler noted, the efficacy of phytoremediation will fluctuate throughout the year. (The system will not be as effective during the winter months.)

• Time may play a crucial role in determining efficacy. Conference call participants noted that it can take several decades or centuries to clean up sites. If a site affects public health, Rose said, the length of time that a technology requires to achieve cleanup or hydraulic control may play a large role in determining whether a technology will be considered effective enough for a site. At other sites, where risk is not as imminent, less focus may be placed on the length of time a technology takes to remediate a site. Fiedler said that EPA is writing guidance on determining reasonable time frames for cleanup using MNA.

Conference call participants also spent some time talking about what must be done to gain a better understanding of the different roles that plants and microbial communities play in phytoremedial processes. Newman noted that the roles may differ from site to site. For example, she said, researchers may find that plants are primarily responsible for chemical degradation at one site, but that the same processes are driven mostly by microbes at a different site. Newman said that she is currently working on a project at the Savannah River site that is using phytoremediation and bioremediation in combination. Newman said that the activities at this site would probably interest the Subgroup. Additionally, she said, the site owners would probably welcome the Subgroup’s input on experimental design, monitoring, and sample analysis.

DESIGNING A FIELD STUDY PROGRAM

Conference call participants decided that they would like to develop a field study program to answer the research questions that they have identified. They agreed to create a protocol so that guidance is available to help answer these questions. They agreed that the protocol should be written to accommodate a broad array of applications.

Conference call participants noted that several phytoremediation protocols already exist. They agreed to evaluate these, along with the Bioremediation Consortium’s protocol, and to identify the components that would be useful for their Subgroup. Conference call participants agreed to identify protocols before the end of the year and to forward these to ERG. Upon receipt, ERG will forward these protocols to all of the Subgroup members.

Once the Subgroup’s field study design is more clearly established, Rose said, a proposal will be written that summarizes the Subgroup’s goals and field study program. This will be distributed to site owners who are interested in conducting phytoremediation field studies.

CREATING A DECISION TREE

During the November 10, 1999, conference call, Subgroup members talked about creating a decision tree to help site managers determine if their sites are candidates for phytoremediation. Tossell said that he distributed a generic phytoremediation decision tree after the conference call. Rose said that he made some modifications to Tossell’s version; he agreed to convert his version to a PDF file and to send it to all of the conference call participants. Rock agreed to distribute a decision tree that was created by the Interstate Technology Regulatory Cooperation (ITRC) Working Group.

OTHER AREAS OF RESEARCH

Conference call participants also expressed some interest in developing some modeling programs. Such programs, they explained, could help investigators predict phytoremediation’s efficacy at different sites, the number of trees that should be used, how far capture zones will extend, and how ground-water flow rates will be impacted by phytoremediation systems. Conference call participants said that creating modeling programs will help promote the use of phytoremediation; they agreed, however, not to pursue this goal at the present time.

ACTION ITEMS

• Conference call participants agreed to send Tossell the names of potential candidates for the Subgroup’s Steering Committee.

• Conference call participants agreed to send ERG information about protocols that have already been developed for phytoremediation test studies. This information will be submitted to ERG by December 31, 1999. ERG will then distribute the information to all of the conference call participants.

• Rock agreed to distribute a copy of ITRC’s phytoremediation decision tree.

• Rose said that he has made some modifications to an existing decision tree. He agreed to convert the tree to a PDF file and to distribute it to conference call participants.

• ERG agreed to talk to Environmental Management Support, Inc. (EMS) about setting up an FTP area on the RTDF Web site.

• ERG agreed to set up the next conference call for December 8, 1999, between 1:00 and 2:30 EST.