Overview of In Situ and Ex Situ Bioremediation of Perchlorate in Groundwater
Paul B. Hatzinger, Shaw Environmental, Inc., Lawrenceville, NJ
A. Paul Togna, Ph.D., Shaw Environmental, Inc., Lawrenceville, NJ 
Jay Diebold. P.E., Shaw Environmental, Inc., Peuwaukee, WI
William J. Guarini, Shaw Environmental, Inc., Lawrenceville, NJ 

Perchlorate Reduction in Soils amended with PAC, HA and Peat
Ellen Pyatt, University of California Davis, Davis, CA
Alan Jackman, University of California Davis, Davis, CA

Update of Remedial Technologies for Perchlorate-Impacted Sites
Harry Van Den Berg, P.E., ENSR International, Camarillo, CA
Kent Baugh, Ph.D., P.E., ENSR International, Alameda, CA  

The Determination of Perchlorate Anion in High Total Dissolved Solids Water Using LC/MS/MS

Jim Krol, Senior Applications Chemist, Waters Corp, 34 Maple St., Milford, MA 01757, Tel: 508-482-2131, Email: Jim_Krol@Waters.com

Using the EPA Information Collection Rule as a data base, drinking water facilities have been reporting higher than anticipated concentrations of perchlorate anion in environmental waters in 22 states. This is a cause for concern because of potential adverse health effects that can occur at low ppb concentrations (mg/L), including interference with iodine thyroid uptake, fetal nervous system development, and a potential carcinogen.  Due to its toxicity, perchlorate has an action limit of 4 ppb in Texas and California drinking water.  EPA may propose a 1 ppb action limit.   DoD and DoE are also interested in prechlorate, an ingredient in many munitions, from a soil contamination perspective.

The current EPA method 314.0 (Determination of Perchlorate Using Ion Chromatography…) uses anion exchange chromatography with suppressed conductivity detection.  This method works well but becomes limiting as the total dissolved solids concentration increases, especially sulfate.  Sample preparation to remove chloride and sulfate is necessary and the most difficult problem; requires the use of a O¹⁸ perchlorate internal standard to account for recovery.

This presentation will describe an LC/MS/MS method for perchlorate without the requirement for sample preparation.  The key to solution is the chromatography of perchlorate relative to sulfate.  As organic modifier concentration increases, perchlorate elutes faster than sulfate allowing the chromatographer to place perchlorate baseline separated between high chloride and high sulfate.  With the direct injection of 100 mL of a solution containing 1000 ppm each of bicarbonate, chloride, and sulfate, MS/MS detection can obtain a perchlorate detection limit (3:1 S/N ) of 0.2 ppb.  Larger injection volumes can be used to increase sensitivity.

Overview of In Situ and Ex Situ Bioremediation of Perchlorate in Groundwater

Paul B. Hatzinger, Shaw Environmental, Inc., Princeton Research Center, 4100 Quakerbridge Road, Lawrenceville, NJ  08648, Tel: 609-936-9300, Fax: 609-936-9221, Email: Paul.hatzinger@shawgrp.com                            
A. Paul Togna, Ph.D., Shaw Environmental, Inc., Princeton Research Center , 4100 Quakerbridge Road, Lawrenceville, NJ  08648, Tel: 609-936-9300, Fax: 609-936-9221, Email: Paul.togna@shawgrp.com
Jay Diebold. P.E., Shaw Environmental, Inc., 2835 N. Grandview Boulevard, Peuwaukee, WI 53072, Tel: 262-549-6898, Fax: 262-549-6938, Email: Jay.diebold@shawgrp.com
William J. Guarini, Shaw Environmental, Inc., Princeton Research Center, 4100 Quakerbridge Road, Lawrenceville, NJ  08648, Tel: 609-936-9300, Fax: 609-936-9221, Email:  William.guarini@shawgrp.com

Bioremediation represents one of the most effective and economical approaches for treating perchlorate in groundwater. This presentation will describe current data from both ex situ and in situ biological treatment systems for perchlorate. Laboratory and pilot-scale tests have been performed by several groups to evaluate the efficiency of different biological reactor designs for the ex situ treatment of perchlorate in groundwater.  These tests have revealed that fluidized bed reactors (FBRs) and packed bed reactors (PBRs) can provide effective treatment of the oxidant. Three full-scale FBR systems are presently in operation, and additional systems are under construction. These FBRs are currently treating more than 5 million gallons of groundwater per day from influent perchlorate concentrations ranging from 2 to 35 mg/L to effluent concentrations of less than 4 μg/L.  The data from both pilot and full-scale bioreactor systems will be presented.  In situ biological treatment has shown great promise in laboratory studies and field demonstrations.  Laboratory studies have revealed that perchlorate-reducing bacteria are naturally occurring in many environments, including groundwater aquifers, and that these bacteria can be stimulated to biodegrade perchlorate to below current regulatory levels with the addition of a variety of organic substrates, including lactate, acetate, and ethanol.  Subsequent field demonstrations have verified the potential for in situ treatment. Data from a recently completed field project at a US Navy facility in Maryland will be presented along with the design and progress of ongoing field projects at sites in California and Texas.  The presentation will provide an overview of the most current biological approaches for remediation of perchlorate in groundwater.

Perchlorate Reduction in Soils amended with PAC, HA and Peat

Ellen Pyatt, University of California, Davis, Hydro Sci Graduate Group, 3124 Bainer Hall, Chemical Engineering, University of California Davis, One Shields Avenue, Davis, CA 95616, Tel: 530-219-4953, Email: elpyatt@ucdavis.edu
Alan Jackman, PhD, Chemical Engineering, University of California Davis, One Shields Avenue, Davis, CA 95616, Tel: 530-752-8777, Email: apjackman@ucdavis.edu

Recently, activated carbons and humic acids have been examined with respect to enhancing microbial reduction of contaminants.  To examine carbon amendment effects on microbial reduction of perchlorate (ClO^4-), microcosm experiments were performed using powdered activated carbon (PAC), humic acid (HA) and highly reduced Twitchell Island Peat (peat).  Carbon amendments were equal to 5, 15 and 50 percent of total mass mixed with Yolo Silt Loam.  H₂ or N₂ continuously purged O₂ from the microcosms.  H₂ microcosms were also supplied with acetate as an electron donor.  Active microcosms were inoculated with microbial communities in soil medium, and in sterile systems soil microbial medium was present during sterilization.  ClO^4- was extracted with .3 M NaOH.   Solutions low in dissolved humic acids (15% and 50% PAC) were analyzed using Dionex 500DX Ion Chromatography with AS16 and AG16 IonPac columns.  All other solutions (100% soil, 5% PAC, peat and HA) were neutralized and analyzed using a Phoenix PER1503 combination electrode.  Microcosms were sampled at 10, 20, 27, 37 and 54 days.  In 5, 15 and 50% additions of PAC and peat, 5% HA, and 100% soil in the H2/acetate microcosms 95% reductions in ClO^4- concentrations were observed over the duration of the experiment.  15 and 50% HA microcosms exhibited poor ClO^4- reduction.  In peat microcosms using N₂, reduction was slow in comparison to the H₂/acetate microcosms, although similar ClO^4- reduction was achieved after 54 days.  In the N₂ system, ClO^4- reduction was poor in 15 and 50% PAC microcosms as opposed to the H₂ systems.  ClO^4- reduction was observed in the N₂ 5% PAC microcosm, however final ClO4- concentrations were an order of magnitude greater than those observed in the H₂/acetate system.  In 100% soil, reduction of ClO^4- was not appreciably different in the H₂ and N₂ systems.

Update of Remedial Technologies for Perchlorate-Impacted Sites

Harry Van Den Berg, P.E., Sr. Program Manager, ENSR International, 1220 Avenida Acaso, Camarillo, California 93012-8727, Tel: 805-388-3775 Ext. 299, Fax: 805-388-3577, E-mail: hvandenberg@ensr.com
Kent Baugh, Ph.D., P.E., Sr. Program Manager, ENSR International, 1420 Harbor Bay Parkway, Suite 120, Alameda, CA 94502, Tel: 510-847-9747, Fax: 510-748-6799, E-mail: kbaugh@ensr.com

Perchlorate salts, such as ammonium, sodium and potassium perchlorate are widely used as a strong oxidizer in various industries and consumer products (e.g., road flares).  Dissolution of perchlorate salts yields the perchlorate anion, which is highly stable and mobile in surface and groundwater systems.  Due to its mobility and stability in an aqueous solution, perchlorate impacts in groundwater can be found at large distances from their source.  The inhibitory effect of perchlorate on the uptake of iodide by the thyroid gland combined with improvements in analytical detection methods since 1997 have prompted the regulatory community to propose increasingly stringent action levels as low as 1 microgram per liter (µg/L) in some states. 

Although perchlorate is a powerful oxidizer when used in solid form, e.g. ammonium perchlorate in solid rocket fuel, it resists abiotic reduction by strong reducing agents when dissolved in water due to unfavorable reaction kinetics.  However, perchlorate can be degraded via biologically mediated reduction and it can be removed from groundwater via membrane processes or sorption onto positively charged media.  Several in-situ and ex-situ perchlorate treatment technologies have been developed or are currently under development that are typically based on either biological reduction, which destroys perchlorate, or sorption processes (anion exchange) where perchlorate is removed from the water-phase.  Similar to other contaminants, the applicability, effectiveness and cost of these technologies are highly dependent upon site specific conditions, such as hydrogeology, geochemistry, depth to groundwater, perchlorate distribution and the presence of other contaminants.

This paper provides an update of the criteria affecting the selection process and of innovative and established perchlorate treatment technologies and their typical applicability, development status, advantages and limitations, as well as a presentation of relative cost. Innovative technologies that will be highlighted include in-situ bioremediation and the emergence of biological permeable barrier technology for addressing perchlorate. Design and performance criteria of the more proven technologies, such as in-situ and ex-situ bioremediation and selective anion exchange, will be discussed based on actual test and/or operating data. In addition, hands-on operational experience with full-scale ex-situ treatment systems for water impacted by perchlorate and other contaminants will also be discussed.

The selection of currently available ex-situ treatment technologies for perchlorate-impacted water depends mainly on the concentration of perchlorate and, if present, other contaminants. A cost comparison chart based on the authors’ experience with perchlorate treatment, encompassing field demonstrations and full-scale systems, will be presented that can be used as a general guide for the selection of ex-situ treatment technologies.

Top