# Presentation: 773341

## Microbiology of a Biobarrier for In Situ Remediation of Nitrate and Perchlorate

**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: **_[http://www-](http://www-emtd.lanl.gov/P2/Barrier/Mortendad.html)__[emtd](http://www-emtd.lanl.gov/P2/Barrier/Mortendad.html)__[.](http://www-emtd.lanl.gov/P2/Barrier/Mortendad.html)__[lanl](http://www-emtd.lanl.gov/P2/Barrier/Mortendad.html)__[.gov/P2/Barrier/](http://www-emtd.lanl.gov/P2/Barrier/Mortendad.html)__[Mortendad](http://www-emtd.lanl.gov/P2/Barrier/Mortendad.html)__[.html](http://www-emtd.lanl.gov/P2/Barrier/Mortendad.html)_**.**

**ABSTRACT:**

**Multiple Layered***** In Situ***** PRB for Groundwater Remediation**

**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 Laboratory****	****	****	****Session 260****	****	****	*****Corresponding author: Phone: (505) 665-9986**
**	****2****University of California, Berkeley****	****	****Poster Q-338****	****	****Fax: (505) 665-4955, E-mail: bastriet@lanl.gov**

**LA-UR-04-3226**

## Monitoring Results

**Microbial Characterization of  PRB Water Samples**

**Monitoring Results**

** ****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**

- • 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**

**UC Berkeley team performed full characterization of two sample sets, 5/03 and 8/03**

** ****pH and Dissolved Oxygen**

**Perchlorate (ClO****4****-****), Chlorate (ClO****3****-****), Chlorite (ClO****2****-****), and Bromide (Br ****-****) Concentrations**

** ****Monitoring Wells in PRB**