Treatment of Emerging Contaminants with Activated Persulfate. Philip Block, PhD FMC Corporation

Transcription

1 Treatment of Emerging Contaminants with Activated Persulfate Philip Block, PhD FMC Corporation

2 Agenda Brief overview of persulfate chemistry PFOA and PFOS 1,4-dioxane Metals (mercury and arsenic)

3 Activated Persulfate Chemistry Activated persulfate has been used for over twelve years to treat contaminated soil and groundwater activation needed to form highly reactive radical species S 2 O activator SO4 - + (SO4 - or SO 4-2 ) Heat Iron H 2 O 2 High ph 2.6 ev One of strongest oxidants available.

4 Activated Persulfate Chemistry Reactive species sulfate radical SO 4 - hydroxyl radical OH - superoxide O 2 - robust, multi-prong attack on contaminant can treat a wide range of organic contaminants

5 PFOA / PFOS PFOS is a recalcitrant xenobiotic which is persistent, bio-accumulative & toxic Use in fire fighting foams (AFFF), Scotchguard etc. ISCO developed as aggressive solution for in situ destruction of PFOS

6 PFOA / PFOS Peer-Reviewed Literature Chen, et al, Photodegradation of Perfluorooctanooic Acid in Water Under Irradiation of 254 nm and 185 nm Light by Use of Persulfate, Water Science and Technology 54, p 317, 2006 Hori, et al, Efficient Decomposition of Environmentally Persistent Perfluorocarboxylic Acids by Use of Persulfate as a Photochemical Oxidant, Environ Sci Technol 39, p 2383, Liu, et al, Effect of Temperature on Oxidative Transformation of Perfluorooctanoic Acid (PFOA) by Persulfate Activation in Water Separation and Purification Technology, in print, Lee, et al, Microwave-hydrothermal Decomposition of Perfluorooctanoic Acid in Iater by ironactivated Persulfate Oxidation Water Research 44, p 886, Hori, et al, Persulfate-induced Photochemical Cecomposition of a Fluorotelomer Unsaturated Carboxylic Acid in Water, Water Research 41, p 2962, Kingshott, Remedial Approaches for Perfluorooctane Sulfonate, master s thesis, Imperial College London, 2008.

7 Study Outcomes UV activated persulfate destruction of PFOA Chen PFOA rapidly destroyed by UV activated persulfate. Intermediates observed.

8 Study Outcomes Hori UV activated persulfate destruction of PFOA PFOA rapidly destroyed by UV activated persulfate. Intermediates observed.

9 Study Outcomes Lee Modest results on PFOA using heat and microwave radiation. Increased performance upon addition of ZVI.

10 Study Outcomes Kinshott Heat and high ph activated persulfate destruction of PFOS Heat and hydrogen peroxide activated persulfate rapidly destroyed PFOS. Alkaline activation had much slower kinetics.

11 % PFOS Reduction FMC Lab Data on PFOS Destruction 21 Day Results PFOS Reduction PEN Value = % contaminant destroyed / % persulfate used FeEDTA Fe + H2O2 high ph heat Low Medium High Low: 1 x Medium: 2 x High: 10 x Control PFOS concentration: 985 mg/l Klozur persulfate dosing: 1, 2, 10 x stoichiometric amount Room temperature, DI water

12 1,4-dioxane primary use as a stabilizer for 1,1,1-TCA highly water soluble (miscible) resulting 1,4-dioxane plume may be larger than TCA plume analytical detection is difficult US EPA lists as probable carcinogen Prop 65 (California) lists as a cancer causing agent

13 1,4-dioxane US EPA Listed Health Advisory for Dioxane at a Drinking Water Concentration of 3 ppb (µg / L) Several EPA Regions and States Have Developed Guidelines for Dioxane In 2004, Colorado First State to Establish Enforceable Standard for Dioxane in Groundwater State or Region Type of Guidance Matrix Concentration EPA Region 3 Risk based Conc s Tap water 6.1 ppb EPA Region 6 EPA Region 9 California Colorado Delaware Florida Maine Human health medium specific screening levels Preliminary remediation goals Health based advisory levels Water quality standard Uniform risk based remediation standards Soil cleanup target levels Maximum exposure guideline Tap water Tap water DW GW & surface water GW GW DW 6.1 ppm 6.1 ppb 3 ppb 6.1 ppb (3.2 ppb March 10) 6 ppb 3.2 ppb 3.2 ppb Massachusetts DW 3 ppb State or Region Michigan Type of Guidance Matrix Concentration Generic cleanup criteria and screening levels DW Missouri Target Conc. GW 3 ppb New Hampshire DW 3 ppb North Carolina GW 7 ppb Pennsylvania South Carolina Texas Medium specific concentrations for organic regulated substances in groundwater Drinking water regulation and health advisory Protected concentration levels GW DW GW 350 ppb - Ind 85 ppb - Res 5.6 ppb (A) 24 ppb (B) 56 ppb (C) 240 ppb (D) 70 ppb 18.6 ppb - Ind 8.3 ppb - Res West Virginia Risk based Conc s DW 6.1 ppb A = used aquifer / residential; B = used aquifer / non residential; C = nonuse aquifer / residential; D = nonuse aquifer / non residential

14 Study Outcomes Site: Contaminants: Treatment train: active warehouse in Piedmont of NC vadose and saturated zones in sand / silt / clay TCA (200 ppm), DCE (82 ppm), 1,4-dioxane (50 ppm) combination of steam (target 45 C) and lime 30 injection points inside building 60 injection points outside injected 100,000 lbs of Klozur Monitoring Wells Site Location: North Carolina 1,4 Dioxane Treatment by Catalyzed Sodium Persulfate Dioxane concentration (ug/l) Pre Treat Post Treat % Reduction John Haselow MW-1 50,000 < % MW < % MW < % MW Non Detect 100%

15 Study Outcomes Paul Dombrowski

16 Study Outcomes 180,400 lb of Klozur persulfate injected over 3 events High ph activation (followed by peroxide application)

17 Metals oxidants generally are thought to have a negative impact on nascent metals in groundwater changes in groundwater quality (ph, ORP, DO) can change metal mobility however, long term change in mobility is not observed post ISCO application once groundwater returns to background conditions can activated persulfate be used to reduce soluble metal concentrations?

18 Example for Mercury W. Michigan Lab Study Prof. Dan Cassidy contaminated sediments from Kalamazoo River initial contaminant loadings 7720 mg/kg PCB 9063 mg/kg PAHs 175 ug/kg total Hg study incorporated 3 dosages: persulfate activated with calcium peroxide 4 g / kg sediment 10 g / kg sediment 20 g / kg sediment Stirred tank reactor

19 log MPN/g soil Example for Mercury MPN of Sulfate Reducing Bacteria (SRB) Time (weeks) Control Dose 1 Dose 2 Dose 3

20 Sulfide Conc. (mg/l as S) Example for Mercury Sulfide Production Time (weeks) Control Dose 1 Dose 2 Dose 3

21 Example for Mercury HgS formation after 30 weeks Dose [HgS] (μg/kg)* % total Hg Control Dose Dose Dose *[HgS]=203 μg/kg if all Hg precipitated as cinnabar.

22 Example for Arsenic Laboratory study investigating combination of persulfate and zero valent iron (ZVI) to reduce soluble arsenic DI water containing mg/l As(III) was spiked into silty sand soil under nitrogen. ~ 30% of As spike was lost due to adsorption onto soil after 60 hours of contact time water to soil ratio: 50 g soil to 100 ml of spiked water Grams of Reagent Addition to 300 g of Soil Sample Id. Sodium Zero valent persulfate iron Na 2 PO 4 CTL R1L R1H R2L R2H :1 persulfate : ZVI wt% active to soil

23 Example for Arsenic

24 Summary activated persulfate can treat a wide range of contaminants emerging contaminants can readily be treated with activated persulfate PFOS / PFOA 1,4-dioxane MTBE (not presented here) Nitrosamines (not presented here) pharmaceuticals / endocrine disrupters (not presented here) activated persulfate has been shown to have a positive effect on the reduction of aqueous concentrations of certain metals

25 Questions Philip Block, PhD FMC Global Peroxygens