LA-UR- Researchers at LANL are demonstrating a multi-layered permeable reactive barrier (PRB), for in situ treatment of groundwater bearing mixed contaminants. A biobarrier layer removes dissolved oxygen and promotes anaerobic microbial reduction of nitrate and perchlorate. The location in Mortandad Canyon was selected because of the directed flow of alluvial groundwater, a large network of existing monitoring wells, and a well-documented contaminant history. The PRB uses a funnel-and-gate system with four sections to immobilize or destroy contaminants, including perchlorate, nitrate, 90 Sr, 238,239,240 Pu, and 241 Am. The four cells, ordered by sequence of contact with the groundwater, consist of a colloid barrier, a mineral apatite layer, a biobarrier, and a “polishing” layer. The biobarrier maintains a one-day average residence time. Four monthly data sets were collected. Collaborators at the University of California at Berkeley conducted a series of microbial analyses to evaluate function of the biobarrier. Water was obtained from 3 sampling wells across each cell, and from wells located up- and down-gradient. Overall, results show microbial reduction of nitrate and perchlorate to levels below detection. Field parameters include DO, pH, redox (ORP), and others. The laboratory microbial methods include enumeration by Most Probable Number (MPN) analysis of nitrate- and perchlorate-reducers, assays for metabolite organic acids (acetate, propionate, etc.), ferrous/ferric iron, DNA- specific probes for known perchlorate-reducer genera, and a new RNA-based assay for chlorite dismutase activity. Additional results show moderate numbers of both dissimilatory perchlorate- and nitrate-reducing populations, production of acetate and propionate, and reduced DO and pH levels. The dominant group of perchlorate reducers present was from the previously described Dechloromonas genus, in the beta subclass of the Proteobacteria, which together with Dechlorosoma are considered to be the primary genera in circum-neutral mesophilic environments. The performance of the PRB will be evaluated through its lifetime, projected to be ~10 years. Final report of PRB installation can be found at URL: ABSTRACT: Principles of Microbial Perchlorate Reduction Perchlorate-reducing bacteria are apparently ubiquitous in soil Process enzymatically reduces perchlorate to chlorate, then chlorite, with subsequent dismutation to chloride and oxygen Organisms “respire” using perchlorate as an electron acceptor in place of oxygen or nitrate, organic carbon acts as electron donor Microorganisms are facultative anaerobes from several different genera, primarily Dechloromonas and Dechloromusa Nitrate can be an inhibitor of perchlorate reduction, mechanism of inhibition is unclear, although is probably related to redox potential Anoxic conditions required for perchlorate reduction, redox potential required for reduction to proceed is lower than for nitrate reduction Principles of Biological Denitrification “True” denitrification is a reductive process that yields energy for microbial cell growth Process sequentially reduces nitrate to nitrite, nitric oxide, nitrous oxide and nitrogen gas Organisms “respire” using nitrate as an electron acceptor in place of oxygen, organic carbon acts as electron donor Microorganisms are facultative anaerobes from many different genera, e.g. Pseudomonas, Bacillus, etc. Both carbon and phosphorus may be limiting in natural ground waters, preventing the timely destruction of nitrate Introduction Perchlorate and nitrate are growing worldwide problems, existing as highly mobile anionic groundwater contaminants = large plumes Biological reduction of perchlorate and nitrate in groundwater is under development as a technology to address these problems EPA drinking water limit may be as low as 1 цg/L (ppb) perchlorate Maximum Contaminant Level (MCL) is 10 mg/L nitrate-N Perchlorate contamination is primarily from DoD propellant production and disposal (ammonium perchlorate) Major sources of nitrate are over-fertilization, animal farms/dairies and nitric acid use in mining and weapons programs Use of nitric and perchloric acid at LANL without removal during water treatment resulted in significant groundwater contamination (Per)chlorate Reduction Reactions Microbial Denitrification Reactions Overall metabolic reduction reaction: 3Ac - + 4ClO H > 6CO Cl - + 6H 2 O *Ac = acetate Enzymatic reduction reactions: ClO 4   ClO 3   ClO 2   Cl  + O 2 (per)chlorate reductase*chlorite dismutase ([per]chlorate) (chlorate) (chlorite) (chloride) *Both (per)chlorate and chlorate appear to be substrates of the same enzyme Metabolic denitrification reaction: 0.625Ac - + NO > 1.25HCO N 2 Cell component synthesis reaction: 3.5Ac + NO > C 5 H 7 O 2 N + 2HCO 3 Combined reaction: 0.712Ac + NO > 0.485N C 5 H 7 O 2 N HCO 3 Ac = acetate; C 5 H 7 O 2 N = representative cellular material composition Atmospheric Nitrogen O rganic nitrogen A mmonium Nitrogen Fixation N itrite Nitrate Ammonification Oxidation Fertilizer Nitrate Contamination Water Table Leaching Plant Uptake Plant Decay Animal & Human Waste Industry Atmospheric Nitrogen Ground Water Ground Water Nitrate Contamination Oxidation Denitrification N 2 Gas The Environmental Nitrogen Cycle Multiple Layered In Situ PRB for Groundwater Remediation Time (days) Sr and ClO 4 Conc. (mg/L) NO 3 Conc. (mg/L) Sr data ClO4 (mg/L) NO3 data PRB Laboratory Results Designed to remove radionuclides (e.g. Sr, Am, Pu, U), metals (e.g. Pb, Co, Cr), nitrate and perchlorate Four sections with unique purpose: colloid barrier, apatite, biobarrier, gravel polishing section Bench-scale batch studies, column studies in 1- and 2- dimensions to demonstrate effectiveness of each section Bench-scale mock-up of full-scale system in final design sequence, actual groundwater used over ~one year period Demonstration PRB installed in January 2003 PRB Laboratory Mock-up Microbiology of a Biobarrier for In Situ Remediation of Nitrate and Perchlorate B.A. Strietelmeier 1*, J.D. Coates 2, J. Pollock 2, J.P. Kaszuba 1, T.P. Taylor 1, and P. Longmire 1 1 Los Alamos National LaboratorySession 260*Corresponding author: Phone: (505) University of California, BerkeleyPoster Q-338Fax: (505) , LA-UR

Microbial Characterization of PRB Water Samples Monitoring Results PRB Design – Funnel and Gate PRB Installation –Post Construction, Wing Walls View of Completed PRB Wing Wall Installation Detailed Hydrologic Cross-Section of PRB Hydrogeologic cross-section from west to east through the PRB and PRB monitor wells 1 and 2 in Mortandad Canyon. The contact between bedrock and alluvium and the bottom of the PRB are also shown. Only the lowermost portion of the PRB is depicted, as elements extend to ground surface at an elevation of 6882 feet. The positions of individual cells within the PRB are shown schematically. The elevation of groundwater in the alluvial aquifer for mid-May through mid-September is plotted. Groundwater levels lying below the alluvium- bedrock contact are interpreted as residual groundwater in well bottoms. Acknowledgements Acknowledgements Ferrous iron production in the biobarrier indicates iron- reducing conditions are present Dominant group or perchlorate reducers was Dechloromonas, and members were most closely related to D. aromatica, strain RCB Continued monitoring, potentially including tracer studies, is necessary to understand the system more fully A scientific study of the Mortandad Canyon PRB would be of great benefit to assist in the understanding of similar systems at other sites, funding is being pursued for such a study A lot more needs to be learned about the radionuclide and metal interactions with the PRB materials Metabolic by-products: organic acids - acetate, propionate, butyrate IC analysis of full suite of anionic species Total ferric and ferrous iron Identification of dominant perchlorate-reducing species Test for nitrate reduction by perchlorate-reducing species Microbial Analyses Conducted Microbial Analyses Conducted Initial results from monitoring and microbial studies in May and August 2003 show that reduction of perchlorate and nitrate is occurring in the apatite and biobarrier sections of the PRB Results also indicate that insufficient water was present in this time period for appreciable flow to occur through the PRB MPN results indicate that both ClRB and DNB populations are increasing in the biobarrier during this time period Measures that indicate viable populations include reduction of oxygen, perchlorate and nitrate, production of metabolic by-products, and decrease in pH and ORP A multi-layered PRB designed to remove Pu, Am, Sr, nitrate and perchlorate from flowing alluvial groundwater has been successfully emplaced in Mortandad Canyon at LANL Department of Energy (DOE) Pollution Prevention program for funding PRB development and installation DOE Fire Recovery program for partial funding of installation Shaw Environmental and Infrastructure, Inc. for design and installation, hydrologic modeling and field support Laboratory studies team – S.D. Ware, P.A. Leonard, E.M. Hodge, B.A. Martinez, M.L. Espinosa and J.D. Adams, N. Lu, J. Conca and J. Wright University of California, Berkeley, Department of Plant and Microbial Biology Ernest Orlando Lawrence Berkeley National Laboratory, Earth Sciences Division Conclusions Conclusions UC Berkeley team performed full characterization of two sample sets, 5/03 and 8/03 Identification of Dominant Perchlorate-Reducing Species Results – May 2003 and August 2003* *Results were the same for both May and August 2003 pH and Dissolved Oxygen Perchlorate (ClO 4 - ), Chlorate (ClO 3 - ), Chlorite (ClO 2 - ), and Bromide (Br - ) Concentrations Monitoring Wells in PRB MCO-4BGRAVELAPATITEBIO BARRIERLIMESTONEMCO-5 WELL OR PRB CELL Figure C-2. Distributions of perchlorate (ClO4-1), chlorate (ClO3-1), chlorite (ClO2-1), and bromide (Br) in wells and in the PRB installed in Mortandad Canyon. Detection limits (DL) for ClO4-1, ClO3-1, and ClO2-1 are 2, 10, and 100 ppb, respectively, using ion chromatography. Br (08/03) ClO2 (08/03) ClO3 (08/03) ClO4 (08/03) Br (07/03) ClO2 (07/03) ClO2 (05/03) ClO3 (07/03) ClO3 (05/03) ClO4 (07/03) ClO4 (05/03) Mortandad Canyon Location Mortandad Canyon In Situ Perchlorate And Nitrate Reduction Demonstration 2D Mock-up of PRB Design Site Characteristics and Design Parameters Design Parameters Target alluvial groundwater, minimize surface erosion/infiltration Optimize hydraulic capture, minimize reactive volume Minimize excavated soil requiring waste disposal Residence time in biobarrier, 1 day minimum Lifetime = ~10 years Install ports for access to solids and aqueous fluids Mortandad Canyon Hydrologic funnel Hydraulic floor Groundwater flow  surface water flow Low-level rad in soil Geotechnically feasible Demonstration multi-layered PRB system installed in Mortandad Canyon in path of large plume resulting from contaminated water discharged from wastewater treatment plant Wastewater plant treatment system not designed initially to remove perchlorate and nitrate, discharged for over 40 years Recent addition of ion exchange system has removed the perchlorate source contamination PRB operational since January 2003, drought has resulted in low water conditions and no flow through PRB for most of this period Monitoring began in May 2003 and continues to present