Full-Scale Alkaline Hydrolysis of TNT and DNT in Soil

Transcription

1 Full-Scale Alkaline Hydrolysis of TNT and DNT in Soil June 17 th, 2010 Presented by: Ronnie Britto, PhD, PE Mikael Spangberg, PE, LEP

2 PRESENTATION OVERVIEW The Alkaline Hydrolysis Process Case Study Site Description Bench-Scale Study Field Implementation

3 ALKALINE HYDROLYSIS PROCESS Destroys contaminants via nucleophillic substitution Strong nucleophile (hydroxide ion) attacks electrophile Displacement of a leaving (functional) group Electron density of the ring SN2 mechanism Alkaline reagents Response of organic compounds to AH

4 ALKALINE HYDROLYSIS PROCESS Ring Cleavage Intermediate and end-products Polymer and anion formation Catalysts Temperature Effects Other factors

5 SITE BACKGROUND Volunteer Army Ammunition Plant in Chattanooga, TN Built in 1941 to 1943 in support of World War!! Effort, then Korean and Vietnam conflicts; production ceased in 1977 Facility used primarily for production and storage of trinitrotoluene (TNT) Past operations impacted both soil and groundwater TNT and DNT concentrations in soils were as high as 100,000 milligram per kilogram (mg/kg) Shallow soil impacted from 0 to 20 feet below ground surface

6 TECHNOLOGY IMPLEMENTATION CMS recommended excavation, stabilization, and offsite disposal Remedial goals required innovation Effective treatment of large quantity of soil Cost and schedule constraints Treatment approach derived from previous experience and research Implemented in-house laboratory bench-scale tests to evaluate chemical treatment using: Chemical oxidants (traditional) Alkaline hydrolytic and catalytic agents (innovative)

7 BENCH-SCALE OBJECTIVES Evaluate chemical amendments Estimate time required for treatment Approximate chemical dosages Examine by-products and end-products Evaluate moisture and mixing requirements for scaleup

8 BENCH-SCALE SET-UP Baseline samples Pan studies Varying quantities of selected chemical amendments Water added to achieve saturation Mixing Effectiveness sampling included: ph (SW9040) and moisture content Nitrates and nitrites (E300) Explosives (SW8330B)

9 RESULTS OF BENCH-SCALE STUDIES Bench-scale results indicated: High levels of explosives could be treated rapidly (within a week) using an alkaline hydrolytic agent Material Balance indicated complete treatment with no accumulation of organic daughter products Nitrites are the largest identifiable end product (denitrification could be required) Treatment in the field would be feasible and economical

10 Concentration (mg/kg) RESULTS OF BENCH-SCALE STUDIES BS-6 Trial: Concentration Time Series for Dinitrotoluenes ,4-Dinitrotoluene 2,6-Dinitrotoluene 6000 Treatment Start Date Note: 24DNT Soil Cleanup Level is 25.4 mg/kg /7/07 7/12/07 7/17/07 7/22/07 7/27/07 8/1/07 Time (m/d/yy)

11 Concentration (mg/kg) RESULTS OF BENCH-SCALE STUDIES BS-6 Trial: Concentration Time Series for 2,4,6-Trinitrotoluene ,4,6-Trinitrotoluene Treatment Start Date Note: 2,4,6-Trinitrotoluene soil cleanup level is 57 mg/kg /7/07 7/12/07 7/17/07 7/22/07 7/27/07 8/1/07 Time (m/d/yy)

12 FIELD PILOT STUDY Small-scale field demonstration 300 yd3 excavated soil in bermed area (~100 ft by 50 ft) Mix design amounts of an alkaline agent and catalyst Based on results of bench-scale tests Previous chemical handling and soil mixing experience Implemented a soil mixing, moisture addition, analytical, and evaluation schedule Daily mixing Watering as-needed after initial saturation Composite sampling (30 point) was conducted at baseline and seven days post-treatment

13 FIELD PILOT STUDY Pilot Study - Initial Treatment Pile Pilot Study - Addition of Chemicals

14 FIELD PILOT STUDY Pilot Study -Mixing of Chemicals Pilot Study - Watering Treatment Pile

15 FIELD PILOT STUDY RESULTS COC Baseline (July 31, 2007) August 6, 2007 (mg/kg) 1,3,5-TNB ,4-DNT ,6-DNT ,4,6-TNT Amino-DNTs ND 0.82 Nitrotoluenes ND 0.48 Soil ph of 13.0 attained; reduced to 12.2 after one week Nitrite accumulation noted Denitrification bench-scale study

16 DENITRIFICATION BENCH-SCALE STUDY Nitrate and nitrite highly oxidized forms of nitrogen available for consumption by many groups of microorganisms Denitrification process reduction of nitrate and nitrite into gaseous nitrogen Along with saturation, soil containing high organic matter required An organic acid would provide the organic content needed and lower the ph to normal conditions following post-alkaline hydrolysis treatment Before treated soils can be backfilled into the excavation, nitrate and nitrite concentrations could need reduction

17 DENITRIFICATION BENCH-SCALE STUDY Soil pan tests conducted to test the denitrification process Nitrite concentrations decreased from 511 mg/kg to non-detect levels during the first 12 days

18 FULL-SCALE TREATMENT Full Scale Ex-Situ Treatment Soils excavated and treated within asphalt-lined pond 300 cubic yard increments Alkaline and catalytic reagents evenly spread Conventional construction equipment In-house moisture and mixing design ph primary indicator for uniform physical and chemical mixing of chemicals

19 FULL-SCALE TREATMENT Water Application & Mixing Soil Mixing

20 FULL-SCALE TREATMENT Ex-Situ Soil Treatment Area Treated Soil Awaiting Confirmation Results

21 FULL-SCALE TREATMENT Full Scale Ex-Situ Treatment Results 112,500 yd3 (ex-situ) completed treatment (100%) 75 tons total nitroaromatic mass removed (>94%) Treated soils below cleanup targets for DNT (25.4 mg/kg) 42% < 2.54 mg/kg for 2,4-DNT (20x rule) Average 2,4-DNT in remaining piles 6.9 mg/kg TCLP analysis: 20% ND (<0.012 mg/l) 80% < mg/l (0.069 mg/l average)

22 FULL-SCALE TREATMENT Remaining contaminated soils were treated in situ Results indicate in situ treatment is effective and comparable to ex situ treatment To date, approximately 11,000 yd3 of contaminated soil has been successfully treated in situ

23 QUESTIONS Contacts: Ronnie Britto, PhD, PE Mikael Spangberg, PE, LEP 23