Tools and Methods to Reduce Tools and Methods to Reduce - PowerPoint PPT Presentation

Tools and Methods to Reduce Tools and Methods to Reduce Uncertainties Associated with Uncertainties Associated with the Use of In Situ Remediation the Use of In Situ Remediation Techniques for Organic Contaminants Techniques for Organic Contaminants in Soil and Groundwater in Soil and Groundwater by Jean Paré, P. Eng. by Jean Paré, P. Eng. Toronto, ON Toronto, ON July 15 th , 2017 July 15 th , 2017

The Chemistry works but the The Chemistry works but the geology screws it up … geology screws it up … by Jean Paré, P. Eng. by Jean Paré, P. Eng. Toronto, ON Toronto, ON July 15 th , 2017 July 15 th , 2017

Presentation Agenda � In Situ Technology Review and Limitations � Field application challenges and contact issue � Tools, testing and tricks • Before you get to the field • When you’re in the field • Follow up After injection events � Case Study Presentation Chemco-inc.com

In Situ Technology – Key Drivers � Time versus Money � Contaminant Accessibility (infrastructures, utilities) � Sustainability Contribution (remote disposal site, landfilling without treatment, Energy Output) � Polishing steps to achieve Risk Based Criteria � Improvement of contaminant removal rate versus natural attenuation Chemco-inc.com

Chemical Oxidation – Technology Review � Oxidants are introduced or mixed into the soil and groundwater to attack the organic contaminants � Chemical oxidation treatments are commonly used in potable and wastewater applications � Oxidants are non-specific and will react with the targeted contaminants AND with the soil organic content a value called Soil Oxidant Demand - SOD. � Chemical oxidation reactions involve the transfer of electrons and the breaking of chemical bonds � Water is the carrier for the oxidants used in chemical oxidation (except for ozone) � If you have enough oxidant present and sufficient time you will push reaction to FULL mineralization (CO2, H2O, Cl-) of the contaminant of concern � Chemical oxidation can slow down the biological activity but will NOT sterilize the soil completely (potential benefit because of lower toxicity after the Chemical Oxidation is completed)

Chemical Oxidation – Technology Review Common Chemical Oxidants Potassium or sodium permanganate � Hydrogen Peroxide alone � Catalyzed Hydrogen Peroxide � • Hydrogen Peroxide with iron (regular Fenton reagent reaction) • Need to establish acidic conditions (ideal pH between 4 and 6) • Modified Fenton Reagent with chelated metals (neutral pH) Ozone � • Ozone is a gas and must be produced on site • The gas must be injected into the soil Persulfate � • Requires activation to generate free sulphate radicals. • Heat, chelated metal, high pH, surface, organic or hydrogen peroxide can be used to activate the persulphate. Activation method can be adapted to site conditions. Percarbonate � • Requires activation to generate free radicals SAFETY NOTE: ALL THESE PRODUCTS REQUIRE ADEQUATE HANDLING PRATICES AND SAFETY EQUIPMENT.

Chemical Oxidation – Limitations (1) � All chemical oxidation reactions occur in the WATER or moisture phase (except for ozone) � Kinetics of the chemical oxidation reaction is thus influence by the contaminant of concern solubility and availability in the groundwater or moisture phase � Sorbed phase contamination might be challenging to remediate (less available) � In NAPL containing sites, contamination can persist because of the highly hydrophobic properties of the chemicals that make up the NAPLs � Injection technique must induce proper contact between the contaminant and the oxidant for a proper duration for the required reaction to occurs (kinetics)

Chemical Oxidation – Limitations (2) � All oxidants can change the oxidation state of metals and thus increase their solubility and mobility � Metals of particular concern are: chrome, lead, uranium, selenium, vanadium � In most of these cases, the metals will come back in their reduced state once all of the oxidant has been consumed by the environment � Impurities contained in the oxidant must be evaluated � In the case of arsenic, oxidation will help immobilizing the metal by reducing its solubility

Conditions for Selecting Chemical Oxidation Chemical Limitation / Possible Oxidation Disadvantage Alternative Applicability s Options Mobile NAPL Probably not High oxidant Liquid Extraction the best requirement Thermal degradation choice ($) Residual NAPL Yes, but High oxidant Extraction with (10,000’s mg/kg) difficult requirement air/steam injection ($) Thermal degradation High conc. in Yes, good Normal Extraction with soil/groundwater conditions considerations air/steam injection Bioremediation (10’s – 10000’s mg/kg) Dissolved plume Yes, but could Higher cost Bioremediation, be costly due to SOD Reactive barriers (< 1 mg/kg) NAPL: Non-Aqueous Phase Liquid Source : ITRC 2004

Compatibility oxidant/contaminant S 2 O 8 SO 4* Fenton’s Contaminant/Oxydant MnO 4 Ozone Petroleum Hydrocarbon L G/E E E E BTEX L G G/E E E E 1 Phenols G L/G G/E E Polycyclic Aromatic L G E E E Hydrocarbon (PAH) MTBE L L/G E G G Chlorinated Ethenes E G E E E (PCE, TCE, DCE, VC) Carbon Tetrachloride L G L/G L/G L/G Chlorinated Ethanes L G G/E G/E G (TCA, DCA) G 1 Polychlorinated L L L G/E Biphenyls (PCB) Energetics (RDX, HMX) E G E E E L=Low G=Good E=Excellent 1=Perozone Source: Carus Chemical Company

Enhanced Bioremediation Advantages � Enhances natural in-situ processes already at play (typically uses natural groundwater gradient, naturally occurring biodegradation. � Low energy and cost effective � Relatively easy to manage and handle. � Can be used in tandem with other remedial technologies that address small amounts of residual soil and groundwater contamination

Parameters to consider for a successful enhanced bioremediation � Temperature, pH � Nutrients Balance (C:N:P ratio) � Site geology and hydrogeology consideration � Proper micro-organisms presence � Aerobic or anaerobic conditions to support bioremediation in soil and groundwater.

Chemical Reduction Principles In situ // Ex situ • In Situ Chemical Reduction (ISCR) is defined as “a process that combines biotic and abiotic reactions to treat contaminants by creating reducing conditions” • ISCR can be enhanced by anaerobic bioremediation • ISCR also provides abiotic/chemical degradation component if a metal (zero valent iron or other) is present

Chemical Reduction Compatibility reductant/contaminant Chlorinated Compounds � • PCE, TCE, cDCE, 11DCE, VC • 1122TeCA, 111TCA, 12DCA • CT, CF, DCM, CM � Herbicides, Pesticides • Toxaphene, Chlordane, Dieldrin, Pentachlorophenol Energetics � TNT, DNT, RDX, HMX, Perchlorate � Metals and metalloids As, Cr, Pb, Zn, Cd, Hg, Cu, Cr, Ni, Sb, Co � Under aerobic conditions you can target HAP, phtalates, perchlorate, petroleum hydrocarbon In Red: need to have an organic substrate and/or a ZVI/carbon combination

Common Chemical Reducing Agents • Sugars • Molasses • high fructose corn syrup • whey • Fatty acids • Lactate • Butyrate • propionate • Emulsified Vegetable Oils • Soybean Oil • Complex Fermentable Carbon complex • lecithine • polylactate • Zero Valent Iron (ZVI) • Soluble Iron Compounds

Selection Factors – Chemical Reductant • ORP of the aquifer • Hydrogen vs. Acidity produced • Biodegradation rate / longevity • Ease of injection and distribution

Soil Washing – Technology Review � Organic Contaminants (Petroleum hydrocarbon, PCB, Dioxin, Furans, etc.) are entrapped as pure product (free phase) or at high concentration in various soil matrix. � Highly contaminated soils are bringing challenges for an effective low cost remediation. � Soil Washing using co-solvent and/or surfactant offers the benefit to treat effectively and economically these high contaminant concentration that allow for soil to be re-used or dispose at a lower cost.

Activated Carbon – Technology Review � Contaminants sorb to activated carbon � Decreases groundwater mass immediately � Disrupts groundwater/soil mass equilibrium to help drive desorption � Concentrated mass accelerates degradation rates � Various degradation mechanisms are used to treat• Bioremediation (aerobic/anaerobic) � Chemical reduction/oxidation Source: AST

Field application challenges and contact issue � Good treatment require good contact � Application challenges � Geology (Silts and Clays, Sands, gravel and other) � Heterogeneity � Low GW Velocity � < Fracture Pressures � High Volumes to inject � Reagent Kinetics � Depth - Shallow environment - Deep environment

Tools, testing and tricks Before you get to the field � Validating the qualification and quantification of the selected amendment with bench scale lab study Soil and Groundwater amendment validation and treatability study are ALWAYS recommended (If it doesn't work in the lab in ideal contact conditions it WON’T work in the field) � Make sure you have all the necessary data and your injection plan is set properly Chemco-inc.com

Tools, testing and tricks Before you get to the field