4. In Situ Treatment

Table 10-1. Use of in situ technologies for sediments (field demonstrations at full or pilot-scale conducted)
In situ Technology and References	Treatment	Technical Basis	Contaminant Applicability	Application	Development Stage	Comments
Amendments
Biostimulation (oxidation) (Golder Associates 2003)	Biological - Biostimulation	Aerobic degradation of organic contaminants through introduction of oxidants such as calcium nitrate or sodium nitrate	PAHs, BTEX compounds and TPH	Marine and Freshwater	Several pilot scale and full scale projects implemented
AC Amendments (Ghosh, Zimmerman, and Luthy 2003; Cho et al. 2009; Beckingham and Ghosh 2011; Ghosh et al. 2011; Patmont 2013)	Physical – Sorption	Deployment of various carbon options including AC, coke, black carbon/charcoal that strongly sorb organics and inorganics	Hydrophobic organics and metals: PCBs, PAHs, dioxins, pesticides, mercury	Marine and Freshwater	Laboratory studies and field pilots; several full-scale applications currently underway
Organophilic clay (Knox Et al 2011; Arias-Thode and Yolanda 2010)	Physical - Sorption	Sorbing amendment for organic compounds and organically complexed metals	Sorption of organics and organically complexed metals (such as methylmercury)	Marine and Freshwater	Laboratory studies; has been incorporated into sediment caps full scale; may also be used as an amendment in situ
Apatite (calcium phosphate mineral) (Knox et al. 2008 ; Williams et al. 2011; Scheckel et al. 2011)	Chemical Reaction - Transformation	Apatite reaction with metals to form phosphate minerals that sequester the divalent metals and reduce toxicity to aquatic organisms by reducing bioavailabilityThe relationship between external (or applied) dose and internal (or resulting) dose of the chemical(s) being considered for an effect (NRC 2003).	Cd, Co, Hg, Ni, Pb, Zn, and U	Marine and Freshwater	Pilot test in Chopawamsic Creek, VA, sediments. multiple successful laboratory studies	Short reaction time (on the order of weeks); can enhance desorption of As, Se, and Th; reactions sensitive to redox conditions
Delivery systems
Limnofix In situ Sediment Treatment Technology (Golder Associates 2003)	Mechanically mixed/injected	Amendments introduced through a series of tines and nozzles on an injection boom	Generally used to apply oxidative amendments (calcium nitrate) for biodegradation of PAHs, BTEX, TPH or to mitigate acute sulfide toxicity	Freshwater and Marine	Full scale applications and Field Pilots	Has been used to treat sediment to a depth of 0.5 meters (into the sediment) with water depths of 3 to 24 meters
SediMite (Menzie-Cura and UMBC) (Menzie, personal communication, 2011; Ghosh et al. 2009)	Surface placement/biologically mixed	Pelletized AC with a binding amendment tailored to contaminant of concern. Binding adds weight for emplacement on sediment bed. Benthic organisms and natural processes mix SediMite into sediments where binding eventually breaks down increasing surface area of AC	PCBs, methylmercury and other hydrophobic chemicals	Freshwater and Marine particularly in areas of sensitive environments or in hard to reach areas such as around pier structures	Small full scale, Field Pilot Scale, and Laboratory Studies	Initial thickness of application is generally less than 1 cm
AquaGate (AquaBlok patented) (ESTCP program, Aberdeen Proving Ground, Canal Creek, Bremerton Naval Shipyard)	Low impact AC, organoclay and other mineral delivery system	Composite particle of powder AC or other coating material tailored to a contaminant of concern. Coating materials are delivered to sediments by a high density core. Density of particle provides for mixing with sediments (mixing occurs due to gravity)	Used to date on PCBs, range of PAH, pesticides, and a range of metals.	Freshwater and Marine	Laboratory Studies and Field Pilot Scale. Full Scale applications of materials as component of active capA covering over material (contaminated sediment) used to isolate the contaminants from the surrounding environment. design	Allows for placement of materials at greater depths; proven full-scale placement

Table 10-2. Use of in situ technologies (laboratory demonstrations only)
In situ Technology and References	Type	Technical Basis	Contaminant Applicability	Application	Stage	Comments
Amendments
Ozonation (biostimulationModification of the environment to stimulate existing bacteria capable of bioremediation.) (Hong 2008)	Biological - Biostimulation Chemical - Degradation	Introduction of ozone to sediments may degrade organic compounds through first abiotic and then aerobic degradation mechanisms.	PCBs and PAHs	Marine and Freshwater	Laboratory Studies	Pressure-assisted introduction of ozone appears to be more effective than conventional ozonation.
Zero Valent Iron (ZVI) (Hadnagy and Gardener, personal communication, 2011)	Chemical - Transformation	Reductive dehalogenation using zero valent iron usually with a bimetal catalyst. Mg or Zn instead of Fe has also been shown to be effective.	Abiotic destruction of halogenated aromatic organics (such as PCBs, PCDD/F and chlorinated pesticides)	Marine and Freshwater	Laboratory Studies	Achieves destruction of contaminants. Incomplete reactions could potentially produce compounds that are more toxic than parent compounds.
Zeolites (Knox et al. 2008)	Physical - Sorption	Hydrated aluminosilicate minerals with a large open framework that forms large “cages” in the mineral structure. Cages can trap cations and even molecules.	Pb, Cu, Cd, Zn, Cr, Co, Ni	Freshwater	Laboratory Studies	Preferential exchange with Na ions over metals occurs.
Bauxite/ Bauxite Residues/“Red Mud” (Lombi et al. 2002; Gray et al. 2006; Peng et al. 2009)	Physical - Sorption	Bauxite residue (red-mud) contains both Al oxides and Fe oxides. Experiments suggest chemisorption of heavy metals to Fe oxides in the red-mud.	Heavy metals and metalloids Cd, Cu, Pb, Ni, Zn		Laboratory Studies and Soil Pilot Study
Iron Oxides/Hydroxides (Lombi et al. 2002)	Physical - Sorption	Fe minerals such as limonite and goethite adsorb metals reducing bioavailability	Heavy metals Cd, Cu, Zn, and As	Marine and Freshwater	Laboratory Studies
Cement with Lime or Fly Ash (Gray et al. 2006; Peng et al. 2009)	Physical- Solidification/Stabilization	Physical solidificationTo make solid, compact, or hard, to make strong or united, or to become solid or united. of the media and precipitation1) The formation of a solid in a solution or inside another solid during a chemical reaction or by diffusion in a solid; or 2) rain, sleet, hail, snow and other forms of water falling from the sky. of metal carbonates or increases pHA measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity. The pH scale commonly in use ranges from 0 to 14. to allow oxide formation onto which metals can sorb (stabilization)	Heavy metals Cd, Cu, Ni, Pb, and Zn		Laboratory Studies and soil pilot study

Publication Date: August 2014

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