CA2327443A1

CA2327443A1 - Dnapl geo-remedial chemical compound

Info

Publication number: CA2327443A1
Application number: CA 2327443
Authority: CA
Inventors: James Damianoff
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-11-27
Filing date: 2000-11-27
Publication date: 2002-05-27

Abstract

In-situ remedial geo-chemical compound compositions with migratory controls, based on novel surfactant /co-solvent technology, for aquifers contaminated with dense non-aqueous phase liquids are disclosed.

Description

TTTLE:
DNAPL Geo-Remedial Chemical Compound BACKGROUND OF THE INVENTION:
Dense non-aqueous phase liquids (DNAPL) are present at numerous commercial and government sites. Examples of such liquids include chlorinated solvents, creosotes, and coal tars. DNAPL have the potential to migrate to great depths below the water table as they are denser than water. Two characteristics of common DNAPL components, low aqueous solubilities and high interfacial tensions with water, result in the persistence of a non-aqueous phase and very irregular distribution of DNAPL in the subsurface.
This in turn presents significant difficulties for site remediation. Remediation efforts also may risk mobilizing DNAPL and hence spreading contamination to previously clean regions.
Accidental and intentional release of these hazardous wastes threatens environmental sustainability and human health. The capacity of soils to detoxify waste has been well documented. This capacity is limited however, and natural detoxification processes often require years to restore impacted sites.
Remediation of these contaminants has been the interest of the environmental sector.
These remediation efforts have primarily focused on mechanical and physical removal of contaminants, contaminated soils, rocks and backfill materials to approved landfill sites.
More recently, interest has shifted to in-situ prpcedures to remediate these sites and avoid groundwater contamination.
The potential to enhance the recovery of non-aqueous phase liquids (NAPL) from porous media using chemical surfactant and co-solvent flushing is widely recognized and has been applied in petroleum reservoirs since the mid-1920s (Beckstrom and Van Tuyl, 1927). Since the late 1970s, a growing interest has developed in the use of similar chemical systems to mitigate risk posed by subsurface DNAPL (API, 1979). This interest reflects, in large part, the ineffectiveness of currently available remedial technologies to restore NAPL zones in aquifers to typical concentration-based drinking water standards (NRC, 1994 ; Pankow and Cherry, 1996). Investigation of the potentials for surfactant and co-solvent applications of in-situ remediation is well documented by Jafvert, C. T.
( 1996).

The use of surfactants and co-solvents will lead to a lowering of DNAPL-water interfacial tension, which may in turn lead to vertical remobilization of the DNAPL. The risk of downward DNAPL mobilization can be reduced and even eliminated through the use of upward hydraulic gradients. Through proper surfactant/co-solvent selection, it is be possible to reduce the density of the target DNAPL to below that of water, thereby eliminating the threat of downward DNAPL mobilization. A surfactant/co-solvent injection may result in a micro-emulsion that is more dense than water, which may be difficult to recover if its density becomes greater than that of water.
Conversely, a reduced density micro-emulsion of DNAPL may migrate horizontally with groundwater flow spreading contaminants laterally and into the groundwater.
PRIOR ART:
Kammeraad (US Patent No. 5634983) describes a process of mixing contaminated soil with a blend of non-ionic and anionic surfactants in conjunction with an amphoteric surfactant as a chelating agent, in a hopper, to encapsulate the hydrocarbon contaminants.
This method requires the removal of the contaminated soil from the ground and does not address the issues of contaminated groundwater.
From Varadaraj's US Patent No. 5436160, bioremediation of hydrocarbon contaminated soil, we learn of an improved method of enhancing bioremediation via the injection of a blend of surfactants composed of sorbitan esters and alkyl glucosides to assist in making hydrocarbons more available to micro-organisms, followed by the separate injection of microbial nutrients, such as nitrogen and phosphorous containing compounds, to enhance biodegradation of the contaminated hydrocarbons. Varadaraj's invention does not address the need to control downward vertical or horizontal migration of dense non-aqueous phase liquids.
Bartlett et al, in United States Patent S,370,478 describes a zone beneath the water table which prevents both lateral and down-ward movement of contaminants or contaminated water by use of vertical barner walls of low permeability grout. Bartlett's approach is a physical barrier concept to maintain contaminated water.
Lessage, in United States Patent S,64S,374, teaches us how to dehalogenate contaminated ground water or effluents and/or soils that are contaminated with halogenated organic compounds, by using a titanium carboxylic acid derivative and a corrin or porphyrin catalyst. This dehalogenation process of DNAPL does not address the horizontal or vertical migration of DNAPL, or the direct solubilization for contaminated effluent extraction.
Pugh, in United States Patent 5,976,348, describes an invention relating to the in situ decontamination of soils using electric fields to transport strong oxidants, preferably peroxymonosulfate or peroxydisulfate, through the soil. Pugh's invention does not address migrational controls of in-situ DNAPL.

Taciuk, Canada Patent 2054122, describes a innovation for dechlorinating soils contaminated with PCBs andlor chlorinated compounds using rotary kiln, and a reaction of alkali metal hydroxide and a glycolate surfactant. Taciuk's innovation relies on physical removal of contaminated soils.
Clark, in United States Patent 5,824,162, describes the use of terpenes as an industrial solvent and their effectiveness compared to typical chlorinated solvents such as trichloroethylene, perchloroethylene, methyl chloroform and methylene chloride. These chlorinated solvents are characterized as dense non-aqueous phase liquids when emitted into the aquifer.
Shook et al, in United States Patent 5,993,660 teaches us a method for controlling vertical migration of contaminants in an aquifer includes introduction of a solubilizing solution having a surfactant and an alcohol or other light co-solvent. The surfactant is selected to solubilize the contaminant. The alcohol or other solvent is selected to provide the micro-emulsion with a substantially neutral buoyancy with respect to groundwater.
The neutral buoyancy of the micro-emulsion prevents the normal downward movement which is typical of the solubilized dense non-aqueous phase liquid in surfactant-enhanced aquifer remediation. Shook's method relies on adjusting the density of the DNAPL to effect downward vertical migrational controls, but does not effect a horizontal migrational control.
In view of what has been previously proposed in the prior art, it is clear that there exists a need and that it would be both desirable and advantageous to have an effective chemical preparation that could remove large amounts of DNAPL in a relatively short period of time. It would also be desirable and advantageous to have a chemical preparation that could remove DNAPLs found as residual pools, both in the soil and in the groundwater.
It would also be desirable and advantageous to have a chemical preparation that can reduce the density of the contaminant DNAPL to reduce downward vertical migration. It would be further desirable and advantageous to have a chemical preparation that would have inherent horizontal migratory controls. It would again be desirable and advantageous to have a chemical preparation of low toxicity, based primarily upon a solvent that is naturally occurring in nature. It would be additionally desirable and advantageous to have a chemical preparation that could be mixed with water on site. It again would be desirable and advantageous to have a chemical preparation that is readily biodegradable and supports microbiological activity in the contaminated soil or groundwater.
Previous methods of in-situ treatments for petroleum hydrocarbons included hydrogen peroxide, aqueous solutions of micro-organisms, alcohols, toxic solvents or surfactants.
Peroxide treatments would oxidize these hydrocarbons but provide no solubility, were dangerous to handle and difficult to control reaction rates. Micro-organisms, also known as bio-remediation, is a slow process of metabolism of petroleum hydrocarbons to carbon dioxide and water. Short comings in bio-remediation treatments are control of soil pH's, lack of year round moderate temperatures, other toxic soil contaminants and availability of specific nutrients. Alcohols, such as isopropyl or methyl alcohol used as in-situ treatments as solubilizing agents are highly flammable, dangerous to handle and can be toxic to indigenous micro-organisms. Toxic solvents such as toluene, used as solubilizing agents are extremely toxic, highly flammable, dangerous to handle and can often worsen existing contaminant profiles, by adding unwanted toxins if the procedures are not finely controlled. Surfactants alone lack solubilities for wide ranges of DNAPL and require large pore volumes of water to stimulate a pump and treat technology or extraction technology.
SPECIFICATION:
This invention relates to the effective aquifer DNAPL remedial composition, and method of its manufacture.
It is another objective of this embodiment to provide an aquifer DNAPL geo-chemical remedial composition, that can effectively decontaminated a large volume of soil, a large area of land or a large volume of water that contains DNAPL.
It is also another objective of this embodiment to provide an aquifer DNAPL
geo-chemical remedial composition that can reduce the high cost of soil and water removal and excavation, by being used in-situ.
It is further another objective of this embodiment to provide an aquifer DNAPL
geo-chemical remedial composition that can reduce the density of the contaminant DNAPL to reduce downward vertical migration.
It is an additional objective of this embodiment to provide an aquifer DNAPL
geo-chemical remedial composition that is based primarily upon a naturally occurring solvent as a co-solvent.
It is again a further objective of this embodiment to provide an aquifer DNAPL
geo-chemical remedial composition that uses a monoterpene, a naturally occurring non-polar hydrocarbon solvent, as a co-solvent to co-solubilize with the contaminated DNAPL in the aquifer, to create or effect a combined monoterpene-DNAPL of lower density than the original contaminating DNAPL, which will reduce the tendency of the combined monoterpene-DNAPL to migrate vertically downwards in an aquifer.
It is yet another objective of this embodiment to provide an aquifer DNAPL geo-chemical remedial composition that can be mixed or diluted on site, with either hard or soft water.
It is yet further the objective of this embodiment to provide an aquifer DNAPL
geo-chemical remedial composition to form a micro-emulsion of the combined monoterpene-DNAPL, in-situ, with the non-ionic surfactant, in the presence of water provided by preparing aquifer DNAPL remedial composition, or by groundwater, or by pore volumes of water added to the contaminated aquifer.
It is yet an additional objective of this embodiment to provide an aquifer DNAPL geo-chemical remedial composition that may be able to control horizontal migration of the said formed micro-emulsion in-situ, by negating the surfactant properties of the said non-ionic surfactant, through a process of splitting the hydrophilic head from the hydrophobic tail of the said non-ionic surfactant by hydrolysis, rendering the non-ionic surfactant into a water soluble hydrophilic head and a non-water soluble hydrophobic tail portion.
It is again an objective of this embodiment to provide an aquifer DNAPL geo-chemical remedial composition that can be stopped from horizontally migrating of DNAPL
in the soil or groundwater.
It is further another objective of this embodiment to provide an aquifer DNAPL
geo-chemical remedial composition that will be readily biodegradable and support microbiological activity in the contaminated aquifer.
It is a further objective of this embodiment to provide a method for preparing an aquifer DNAPL geo-chemical remedial composition containing the steps of:
Adding with agitation, from about a 0.01 % to 5.00 % volume of ethylene diamine tetraacetic acid-sodium salt, to water a 5.00 % to 25.00 % volume, to create a substantially homogeneous resultant mixture.

2. Then adding with agitation, from about 0.01 % to 10.00 % volume of a phosphate, to the first homogeneous mixture to create a substantially second homogeneous resultant mixture.
Then again with agitation the addition from about 0.50 % to 95.00 % volume of non-ionic surfactant to the second resultant mixture to obtain a third substantially homogeneous resultant mixture.
4. Following, still with agitation, an addition from about 0.50 % to 80.00 %
volume of a monoterpene, to the third homogeneous mixture to create a fourth substantially homogeneous mixture.
5. Water forms the remainder of the geo-chemical solvent remedial composition of this invention. It can be present from about 10 to about 95% volume, based on the total weight of the final aquifer DNAPL geo-chemical remedial composition .
Preferably it should be present from about 5.0 to 75.0 volume % Most preferably, it should be present in a total amount of about 56.73 volume %.

This invention precludes the use of toxic solvents, oxidizers, aicohols or flammable materials and does not require physical or mechanical removal of contaminated soils, or contaminated groundwater.
DETAILED DISCUSSION:
Broadly, the aquifer DNAPL geo-chemical remedial composition of this invention contains from 0.01 % to 10.0 % volume of a chelant, from about 0.01 % to about 10.0 volume of a phosphate, , from about 0.50 % to about 95.0 % volume of an non-ionic surfactant, from about 0.50 to about 80.0 % volume of a monoterpene and the remainder water.
The first two ingredient used in this invention are a chelant and water. A
chelant or chelating agent is an organic chemical compound used in formulations to assist the formulated compound to withstand precipitating effects of commonly present precipitating and scaling agents.
Common precipitating and scaling agents are, among others, alkaline earth metals such as calcium and magnesium, divalent metals such as copper, and amphoteric metals such as aluminum. The removal of undesirable metal ions is often difficul and it is usually easier to inactivate them with a chelating agent. Undesirable metal ions may be found present in water used for formulating or held and/or commercial dilution purposes of the final aquifer DNAPL geo-chemical remedial composition. Amino acid chelating agents are known to be stable in acid or alkaline solutions and at elevated temperatures.
Amino acid chelating agents securely bind metal ions to form stable complexes, which remain very soluble in this form. They are also quite resistant to the action of oxidizing or reducing agents and exhibit low toxicity.
For this invention, the most preferred chelant is the sodium salt of ethylenediamine tetraacetic acid. This is a commercially available compound from chemical vendors. The sodium salt of ethylenediaminetetraacetic acid in this invention is present at a level from about 0.01 % to 10.00 % volume, based upon the total volume of the aquifer DNAPL
geo-chemical remedial composition. Preferably, the ingredient should be present at a volume from about 0.15 % to 2.00 % volume. Most preferably about 0.20 % volume of this ingredient should be used.
Water is used as the diluant and carrier in this geo remedial composition.
Water is initially present at a level from about 5.0 % to 25.0% based upon the total volume Preferably water is initially present at a level of 7.0 % to 20.0% of the total volume and most preferably, water is initially present at a level of 20.0 % of the total volume.

The next ingredient of this aquifer DNAPL geo-chemical remedial composition is a phosphate. Soluble phosphate salts are commercially available produced from the neutralization of orthosphosphoric acid with an alkali. Another member of the commercial phosphate compounds are the molecularly dehydrated phosphates.
Phosphates have been used in many types of detergents, cleaning compounds, industrial boiler water and cooling treatments. Certain phosphates also been used for many years in controlling scale deposition in potable water systems and as buffers in propylene glycol based antifreeze compounds. Thus, they find application in water conditioning and cleansing operations. Phosphates not only soften water, but have other properties such as the ability to deflocculate and suspend insoluble materials, emulsify oils, etc., which aid in the desorption and removal of DNAPLs from soil substrates. Phosphates also act as a basic nutrient source for many species of micro-flora. While not wishing to be bound by theory, it is believed that the incorporation of phosphate as an ingredient into this invention will assist in the desorption and removal of DNAPL from soil substrates and contribute to the stimulation and growth of naturally occurring hydrocarbon assimilating microflora.
For this invention, the most preferred phosphate is sodium hexametaphosphate.
This is a commercially available compound from industrial and commercial chemical vendors.
Sodium hexametaphosphate in this invention is present at a level from about 0.01 % to 10.00 % volume, based upon the total volume of the final aquifer DNAPL geo-chemical remedial composition. Preferably, the ingredient should be present at a volume from about 1.00 % to 2.50 % volume. Most preferably this ingredient should be present about 1.17 % volume.
The next ingredient in this invention is a surfactant. Surfactants are organic compounds consisting of two parts: ( I ) A hydrophilic portion, usually including a long chain hydrocarbon; and (2) a hydrophilic portion which renders the compound sufficiently soluble in water or other polar solvents. This combination of the two parts, hydrophilic and hydrophobic portions in a surfactant render the surfactant surface-active and thus able to concentrate at the interface between a substrate to be cleansed. Two properties of surfactants are central to contaminated aquifer remediation technologies are the ability to lower interfacial tension and the ability to increase solubility of hydrophobic organic compounds.
Both properties arise from the fact that surfactant molecules have a hydrophobic portion and a hydrophilic portion. As a result, when water containing surfactant and DNAPL
come into contact, surfactant molecules will concentrate along the interface, with their polar ends in the water and their non-polar ends in the DNAPL; this lowers the interfacial tension between the two immiscible fluids. When present in sufficient concentration the critical miCellar concentration (CMC), surfactant molecules form oriented aggregates, termed micelles. In water, the molecules in a micelle are arranged with their polar ends outwards and their non-polar ends inwards, forming a non-polar interior to the micelle.
Micelles can incorporate hydrophobic molecules in their interior, producing an apparent increase in solubility. The process of dissolving by incorporation into micelles is termed solubilization. Once solubilized, a compound is transported as if it were a typical dissolved phase. Micellar solutions may either be a single phase system in which micelles containing solubilized contaminant are transported as a dissolved phase in the groundwater, or a separate phase, termed a middle phase micro-emulsion, in which a separate phase containing approximately equal volumes of surfactant and contaminant is formed.
The extent of increase of solubility (solubilization) produced depends upon the contaminant, the surfactant, the salinity and the surfactant concentration.
Increases in solubility of more than five orders of magnitude and solubilities in the hundreds of thousands of mg/L have been reported for common DNAPL components (Baran et al, 1994). Early surfactant field trials used surfactants that produced modest increases in solubility (one or two orders of magnitude) and extracted the DNAPL through slow dissolution. This approach required multiple pore volumes (more than 10) (Fountain et al, 1996). More recent work has emphasized higher performance systems that produce solubilizations above 100, 040 mg/L (Brown et al., 1997).
Surfactants are additionally categorized as anionic, cationic or non-ionic. An anionic surfactant' hydrophilic molecule portion contains a negative charge. A
cationic surfactant's hydrophilic portion contains a positive charge. A non-ionic surfactant does not dissociate but derive their hydrophilic portions from polyhydroxy or polyethoxy structures. Additional categorization of surfactants is amphoteric and zwitterionic. These are less common than the anionic, cationic and non-ionic surfactants.
It is known that avionics, cationics, and amphoteric surfactants which contain charged ions can be neutralized (i.e., lose surfactant properties) by adjusting the pH
of the mixtwe. However, this does not work for conventional nonionic surfactants, other than certain amine-based surfactants, since they do not carry a charged moiety.
For this invention the preferred type of non-ionic surfactant is an acetyl based non-ionic surfactant and more preferably the surfactant for this invention is an acetyl based non-ionic surfactant manufactured by Union Carbide under the trade name "Triton SP
series surfactants". Accordingly, the Union Carbide Triton SP series surfactants are manufactured from certain cyclic acetals having a pendant hydroxyl goup that function as the hydrophobe portion of a pH-splittable surfactant. This series of Union Carbide Triton SP series surfactants which have been alkoxylated or otherwise modified, are surfactants with a wide range of HLBs and having performance properties which are surprisingly superior to those exhibited by other surfactants of related chemical structure.
This actual bond-breaking process, which affords a hydrophobe portion and a hydrophile portion, is splittable and referred to as splittable. Moreover, contrary to the prior amine-based surfactants, which are generally regarded as "reversibles," Union Carbide Triton SP
series surfactants do not re-form into surfactants when the pH is again raised to the alkaline range. These Union Carbide Triton Sp series surfactants act as nonionic surfactants in an alkaline or high pH environment. (n an acidic environment, these surfactants undergo, due to the presence of the acetal chemical functionality, a chemical splitting of the hydrophobe portion of the surfactant from the hydrophile portion, which destroys their surfactant properties, thereby breaking down their association with the hydrophobic constituents, and allowing them to more easily separate from the aqueous phase.
In broad terms, the this provides the splittable, nonionic surfactant portion of this invention, conforming to the deactivation of the surfactant to release the monoterpene-DNAPL contaminant mixture from association with the surfactant, by adjusting the pH of the aqueous stream to an acidic pH sufficient to split the surfactant irreversibly into a relatively water-insoluble fraction and a relatively water-soluble fraction.
The released monoterpene-DNAPL and the water-insoluble fraction of the surfactant form a relatively water-insoluble phase The catalyzed hydrolysis of acetals has been extensively studied in the art.
For example, T. H. Fife, Accounts of Chemical Research, Volume S {1972), pp. 264-272; and, E. H.
Cordes and H. G. Bull, Chemical Reviews, Volume 74(1974) pp. S81-603. From these, it is apparent that the rate and reaction conditions necessary to cause carbon-oxygen bond rupture of the acetal are complex. While not wishing to be bound by theory, the splittable, nonionic surfactants of this invention may be split over a wide range of pressures ranging from atmospheric or sub-atmospheric pressures to super-atmospheric pressures.
The splittable, nonionic surfactant in this final aquifer DNAPL geo-chemical remedial composition is split into a relatively water-insoluble fraction (hydrophobic) and a relatively water-soluble (hydrophilic) fraction. The water-insoluble fraction comprises an aldehyde and the water-soluble fraction comprises an alkoxylated polyol.
Neither fraction produced from the hydrolysis is surface-active, so the monoterpene-DNAPLs are released from association, e.g., emulsion, with the surfactant. The monoterpene-DNAPL
and the hydrophobic fraction of the surfactant form a relatively water-insoluble phase in the aqueous stream. At least a portion of this phase in the spent aqueous stream can recovered by conventional methods such as filtration, skimming, and the like.
A
substantial portion of the water-insoluble phase can be recovered. The recovered water-insoluble phase can be disposed in accordance with regulatory requirements.
The remaining aqueous stream can be discharged to a water treatment effluent system after a final pH adjustment to a relatively non-acidic pH that conforms the waste effluent to environmental regulations, Suitable acids for splitting the surfactant in this final aquifer DNAPL geo-chemical remedial composition, are for example, sulfuric acid, hydrochloric acid, acetic acid, etc.
Preferably, the pH of the adjusted solution is from about pH 3 to about pH 6.
The amount of acid to be added is an amount sufficient to cause splitting of the surfactant.

The surfactants useful in this invention have been broadly described in the art, particularly U.S. Pat. Nos. 3,948,953 and 3,909,460, as well as Polish Temporary Pat.
Nos. 115,527 and 139,977.
The Triton SP 140 surfactant in this invention is present at a level from about 0.10 % to 95.0 % volume, based upon the total volume of the final aquifer DNAPL geo-chemical remedial composition. Preferably, the ingredient should be present at a volume from about 3.00 % to 25.00 % volume. Most preferably about 17.00 % volume of this ingredient should be used.
The next ingredient in this invention is a monoterpene . Terpenes are a classification of biogenic compounds; monoterpenes are a subgroup of terpenes, some of which have stntctures which be thought as being loosely based on that of two isoprene molecules.
Terpenes are the most abundant and widely distributed class of natural products. Many play important biological roles and numerous of them are used by humans and as components of spices and flavours. (ane very important group includes vitamins A, D and E, and hormones (cortisone, estrogen and testosterone).
Monoterpenes can be either acyclic (e.g. myrcene), or contain one ring, called monocyclic (limonene), or two ring structures (alpha and beta-pinene, 3-carene). The emissions from deciduous (hardwood/broadleaf) trees such as oak, poplar, aspens and willows comprise mainly of isoprene, whereas coniferous (softwood) woodland such as pine trees, cedars, redwood and firs emit predominantly monoterpene.
Monoterpenes are found in essential oils of many plants, including fruits, vegetables and herbs. They prevent the carcinogenisis process at both the initiation and promotion/progression stages. In addition, monoterpenes are effective in treating early and advanced cancers. Monoterpenes such as limonene and perillyl alcohol have been shown to prevent mammary, liver, lung and other cancers. They have also been used to treat rodent cancers, including breast and pancreatic carcinomas. In addition, in vitro data suggest that they may be effective in treating neuroblastomas and leukemias.
(Gould, 1997) For this invention, the most preferred monoterpene is d-limonene. This is a commercially available compound from industrial and commercial chemical vendors. d-Limonene has a flash point of approximately I 15 degrees F., categorizing it as a combustible liquid not flammable, a specific gravity of approximately 0.84, and is characterized being non-polar and insoluble in water.
Limonene (C6Hlo) has the properties of optical rotation. There are two optically differing types of limonene, d and 1. c~ limonene rotates to the right and l-limonene rotates to the left. d-Limonene is one of the naturally occurring monoterpenes, and is found in high concentrations in citrus fruits. Because of its pleasant citrus fragrance, it is widely used as a flavor and fragrance additive in perfumes, soaps, foods, chewing gum and beverages.
Also, because d-limonene is a relatively safe and highly effective organic solvent, it is finding increasing use in household and industrial cleaning products, replacing dangerous petroleum-based solvents and environmentally hazardous hydrocarbon solvents.
Another application of d-limonene has been as an odorant in sewage treatment plants.
Additionally, the manufacture of d-limonene is ecologically sound since discarded citrus pulp and peels from the citrus juice industry are used as the source material for this chemical.
It is well established that d-limonene, in man and in other species of mammals, is rapidly broken down by the liver. Considering its natural origin, it is generally believed that d-limonene and related products are readily degraded. Indirect evidence for this belief can be found in publications by several investigators who have demonstrated the ability of certain types of bacteria, called Pseudomonads, to totally degrade d-limonene-like compounds. Other types of bacteria, such as Enterobacteria are capable of transforming d-limonene into other by-products, such as dihydroperillic acid and perillic acid.
d-Limonene is easily degraded by microorganisms found in forest soil, and Bacillus stearothermophilus can grow on and degrades d-limonene.
t~Vhen used in or on food, d-limonene is regulated by the United States, Food and Drug Administration (FDA) Title 21 of the Code of Federal Regulations lists d-limonene (and its variant forms 1-limonene, and dl-limonene) as a Generally Recognized as Safe (GRAS) food additive.
The USEPA regulates the use of limonene when used in cleaning agents and pesticides.
Aside from regulatory requirements regarding product registration, research into other applicable regulations revealed that d-limonene is not specifically listed as a regulated waste by the Resource Conservation and Recovery Act (RCRA), Title III of the Superfund Authorization and Reclamation Amendments (SARA), or the Clean Air Act Amendments of 1990 (CAAA). In addition, neither the National Institute of Occupational Safety and Health (NIOSH) nor the American Conference of Governmental Industrial Hygienists (ACGIH) have developed "Permissible Exposure Limits" (PELs) for this material. From these above human safe and ecologically sound perspectives, one can see that d-limonene is a viable alternative to dangerous petroleum based solvents.
SEAR is the acronym for Surfactant Enhanced Aquifer Remediation. SEAR-NB is a concept of SEAR at neutral buoyancy, where neutral buoyancy is an effective resultant density of the combined co-solvent and DNAPI.,, which resists downward vertical migration. SEAR-NB is well documented by Shook ( 1998) and by Kostarelos ( 1998).
The SEAR-NB method comprises adjusting at least one of the following design parameters:
a (i) the density of the micro-emulsion;
(ii) distance between injection of the chemicals and extraction of the micro-emulsion;
(iii) the rate of injection of the chemicals and (iv) the viscosity of the micro-emulsion which minimizes the vertical mobility of the micro-emulsion and improves extraction.
The method further includes sampling the aquifer for at least one of the following environmental factors of the aquifer:
(i) horizontal permeability;
(ii) vertical permeability;
(iii) aquifer thickness;
(iv) relative permeability to the micro-emulsion phase (v) relative permeability to the water phase, and adjusting at least one of the design parameters to reduce vertical migration of the contaminant. The density of the micro-emulsion is adjusted by injecting chemicals in the form of a chemical composition which is sufficiently less dense than the dense non-aqueous phase liquid to reduce the density of the resulting micro-emulsion. To accomplish this reduction in effectual density of the DNAPL, water miscible alcohol has been proposed by Shook (United States Patent 5,993,660) as the co-solvent and is thus mixed with an undefined surfactant. The alcohol co-solvent is miscible with the DNAPL
and the resultant density of the alcohol-DNAPL is lowered and an undefined surfactant creates a micelle.
Ternary phase diagrams for various alcohol-DNAPL systems have been developed by a number of researchers { Peters and Luthy, 1993; Brandes 1997; Falta, et al 1996; Lunn and Keeper 1996, 1997) and have shown that ternary phase diagrams can predict performance. If alcohol concentrations are kept below the binodal curve, the primary removal mechanism is DNAPL dissolution. If it is increased above the binodal curve, the interfacial tensions reduce towards zero, resulting in complete miscibility, and therefore complete mobilization in water. Whether the miscible mixture of alcohol mixture will be more or less dense than water will depend upon the initial DNAPL density and the relative proportion of components in the system.
One of the inventive ideas of this invention is specifically avoiding the use of an alcohol and instead, using d-limonene to avoid the binodal curve phenomena associated with an alcohol when reducing the effective density of the DNAPL. d-Limonene is a non-polar substance, whereas alcohols are polar substances and as such, d-limonene does not reduce interfacial tensions of DNAPL-water towards zero, thus does not result in miscibility of the DNAPL in water, as alcohols do. This provides an extra measure of safety in-situ, by not promoting the mobilization of the DNAPL in water and eliminates the potential of an alcohol-DNAPL downward vertical migration or horizontal migration in the aquifer.
lz d-Limonene compares favourably with alcohols as a neutral buoyancy enhancer (or density lowering agent). The inherent problems of lowered interfacial DNAPL-water tensions associated with an alcohol is alleviated. As d-limonene is a non-aqueous phase liquid, it is strongly preferential to the DNAPL, causing swelling of the DNAPL and lowering the effective density. The chart below illustrates the specific gravity of three common remedial alcohols, methanol, isopropyl alcohol, and ethanol as opposed to d-limonene and a common DNAPL such as trichloroethylene.
Chemical Com ound S ecific Gravi Trichloroeth lene 1.456 TCE

Ethanol 0.790 Tso ro 1 Alcohol 0.786 Methanol 0.792 d-Limonene 0.840 Based upon d-limonene's low toxicity, its ability to reduce the effective density of DNAPL for SEAR-NB type systems in contaminated aquifers, and owing to its biodegradability, d-limonene is a superior and desirable co-solvent.
d-Limonene in this invention is present at a level from about 0.50 % to 80.00 % volume, based upon the total volume of the final aquifer DNAPL geo-chemical remedial composition. Preferably, the ingredient should be present at a volume from 5.00 % to 40.00 % volume. Most preferably this ingredient should be present about 25.0 volume.
Water forms the remainder of the final ingredient of this final aquifer DNAPL
geo-chemical remedial composition invention. As water was added a diluant with the chelant in the first stage of manufacture of this invention at a most preferable range of 20.0 % to volume of the final aquifer DNAPL geo-chemical remedial, water is added as the balance to comprise 100.00% of the final aquifer DNAPL remedial composition . Water can be present from about 10 to about 95% volume, based on the total weight of the final aquifer DNAPL geo-chemical remedial composition. Preferably it should be present from about 5.0 to 85.0 volume %. Most preferably, it should be present in a total amount of about 56.73 volume %.

METHOD OF MANUFACTURE:
Broadly, the aquifer DNA.PL geo-chemical remedial composition of this invention contains from 0.01 % to 10.0 % volume of a chelant, from about 0.10 % to about 10.0 volume of a phosphate, , from about 0.50 % to about 95.0 % volume of an non-ionic surfactant, from about 0.50 to about 80.0 % volume of a monoterpene and the remainder water.
The aquifer DNAPL geo-chemical remedial composition of this invention was manufactured from the following steps:
First a chelant, of ethylene diamine tetraacetic acid-sodium salt was added about 0.20%
to an initial volume of water about 20.0 %, under agitation to create the first resultant substantially homogeneous mixture.
Then about 1.17% by volume of the second ingredient, sodium hexametaphosphate was added under agitation to the first substantially homogeneous mixture to create the second resultant substantially homogeneous mixture.
Then under agitation, about 17.00 % by volume of the third ingredient, an acetyl non-ionic surfactant, was added to the second substantially resultant homogeneous mixture to create a resultant third substantially homogeneous mixture.
Then again under agitation the fourth ingredient, d-limonene, was added about 25.00 volume, to the third substantially resultant homogeneous mixture to create a substantially resultant fourth homogeneous mixture.
Finally the final ingredient, water was added, about 36.63 % volume to the substantially resultant fourth homogeneous mixture to create the final substantially resultant homogeneous mixture of this aquifer DNAPL gea-chemical remedial composition invention.
COMPOSITION
The following composition is representative of this innovation.
Component Ethylenediamine tetraacetic acid 0.20 (% by volume) (sodium salt) Water 20.00 (% by volume) Sodium Hlexametaphosphate 1.17 (% by volume) Non-ionic surfactant 17.0 (% by volume) d-limonene 25.00 (% by volume) Water 36.30 ~% by volume) This aquifer DNAPL geo-chemical remedial composition is stable. It can de diluted in hard or soft water to form an aqueous dilution. It effectively solubilizes and emulsifies DNAPL contaminants from soil and from groundwater. The d-limonene co-solvent portion is miscible with DNAPL and effects a lower density of the non-polar, non-aqueous phase liquid portion, thus resisting downward vertical migration in the aquifer.
The non-ionic surfactant can be split into a resultant water-insoluble fraction comprising an aldehyde and the water-soluble fraction comprising an alkoxylated polyol.
Neither fraction produced from the hydrolysis is surface-active, therefore micelle formation is removed and migrational controls in the aquifer are instituted. The surfactant, terpene and chelant portion of this embodiment are all biodegradable, while the phosphate portion assists in stimulating micro-flora.
ENVIRONMENTAL REMEDIATION APPLICABILITY
EXAMPLE I : Feeding Neat into an Area of Contaminated Ground Generally, the geo-chemical solvent remedial composition of the present invention can be used to remedy an area of ground contaminated with DNAPL as follows:
Administering through one or more perforated pipes that have been injected into the ground, aquifer DNAPL geo-chemical remedial composition of this invention can be slowly introduced into the perforated pipes to allow the composition to slowly penetrate into the contaminated soil. Several pore volumes of water are then added to the perforated pipes to follow behind the aquifer DNAPL geo-chemical remedial composition. Through one or more injected perforated pipes at an extraction location down flow from the contaminated zone, the resultant solubilized DNAPL-monoterpene that has a lowered density from that of the original DNAPL, with the aquifer DNAPL geo-chemical remedial composition of this invention and the pore volumes of water can be extracted through a suction pump mechanism or a submersible pump system. The resultant solubilized DNAPL resists downward vertical migration into lower levels of the aquifer.
EXAMPLE 2 : Feeding an Aqueous Dilution into an Area of Contaminated Ground Generally, the geo-chemical solvent remedial composition of the present invention can be used to remedy an area of ground contaminated with DNAPLs as follows: The geo-chemical solvent remedial composition of this invention can be diluted from one part geo-chemical solvent remedial composition, to one part water up to 1 one part geo-chemical remedial solvent composition to twenty parts water to make an aqueous solution. This resultant solution of water and aquifer DNAPL geo-chemical remedial composition can be administering through one or more perforated pipes that have been injected into the ground, the geo-chemical solvent remedial composition of this invention can be slowly introduced into the perforated pipes to allow the composition to slowly penetrate into the contaminated soil. Through one or more injected perforated pipes at an extraction location down flow from the contaminated zone, the resultant solubilized DNAPL with the aquifer DNAPL geo-chemical remedial composition of this invention -water solution can be extracted through a suction pump mechanism or a submersible pump system. The resultant solubilized DNAPL resists downward vertical migration into lower levels of the aquifer.
EXAMPLE 3: Feeding an Aqueous Solution into an Area of Contaminated Ground and Splitting the Surfactant.
Generally, the geo-chemical solvent remedial composition of the present invention can be used to remedy an area of ground contaminated with DNAPL as follows:
Administering through one or more perforated pipes that have been injected into the ground aquifer DNAPL geo-chemical remedial composition of this invention can be slowly introduced into the perforated pipes to allow the composition to slowly penetrate into the contaminated soil. Several pore volumes of water are then added to the perforated pipes to follow behind the aquifer DNAPL geo-chemical remedial composition. Through one or more injected perforated pipes at an extraction location horizontally or vertically down flow from the contaminated zone, an acid may be injected either in concentrated form or as a diluted aqueous acid, to form a reactive chemical barner. The acid of this injected chemical barrier will hydrolyze the non-ionic surfactant portion of this aquifer DNAPL
geo-chemical remedial composition of this invention, splitting the hydrophilic head of the non-ionic surfactant away from the hydrophobic tail, of the non-ionic surfactant. The resultant water-insoluble fraction comprising an aldehyde and the water-soluble fraction comprising an alkoxylated polyol. Neither fraction produced from the hydrolysis is surface-active, so the monoterpene-DNAPL created by the aquifer DNAPL geo-chemical remedial composition are released from association with the surfactant of the aquifer DNAPL geo-chemical remedial composition. The monoterpene-DNAPL and the hydrophobic fraction of the surfactant form a relatively water-insoluble phase in the aqueous stream that has a density lower than that of the original contaminating DNAPL.
The resultant relatively water-insoluble phase DNAPL-monoterpene that has a lowered density than that of the original DNAPL, is resistant to downward vertical migration in the aquifer.

EXAMPLE 4: Feeding Neat or an Aqueous Dilution into Contaminated Groundwater, and Splitting the Surfactant.
Generally, the geo-chemical solvent remedial composition of the present invention can be used to remedy an area of groundwater contaminated with DNAPL as follows:
Administering through one or more perforated pipes that have been injected into the ground, the aquifer DNAPL geo-chemical remedial composition of this invention can be slowly introduced as the neat form or in an aqueous dilution into the perforated pipes to allow the composition to slowly penetrate into the groundwater without the addition of pore volumes of water. Through one or more injected perforated pipes at an extraction location horizontally or vertically down flow from the contaminated zone, an acid may be injected either in concentrated form or as a diluted aqueous acid, to form a reactive chemical barrier. The acid of this injected chemical barrier will hydrolyze the non-ionic surfactant portion of this aquifer DNAPL geo-chemical remedial composition of this invention, splitting the hydrophilic head of the non-ionic surfactant away from the hydrophobic tail, of the non-ionic surfactant. The resultant water-insoluble fraction comprising an aldehyde and the water-soluble fraction comprising an alkoxylated polyol.
Neither fraction produced from the hydrolysis is surface-active, so the monoterpene-DNAPL created by the aquifer DNAPL geo-chemical remedial compositior~,are released from association with the surfactant of the aquifer DNAPL geo-chemical remedial composition. The monoterpene-DNAPL and the hydrophobic fraction of the surfactant form a relatively water-insoluble phase in the aqueous stream that has a density lower than that of the original contaminating DNAPL. The resultant relatively water-insoluble phase DNAPL-monoterpene that has a lowered density than that of the original DNAPL, is resistant to downward vertical migration in the aquifer.
The invention now being fully described, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as defined in the following claims.

Claims

1. A aquifer DNAPL geo-chemical remedial composition comprising from about 0.01 % to 10.00% volume of a chelant, from 0.01% to 10.00 % volume of a phosphate, from 0.50 % to 95.00 % volume of a non-ionic surfactant and from 0.50 % to 80.00% volume of a monoterpene and the remainder water.

2. The aquifer DNAPL geo-chemical remedial composition of claim 1 wherein said chelant is ethylenediamine tetraacetic acid (sodium salt).

3. The aquifer DNAPL geo-chemical remedial composition of claim 1 wherein said phosphate is sodium hexametaphosphate.

4. The aquifer DNAPL geo-chemical remedial composition of claim 1 wherein said non-ionic surfactant is an acetyl based non-ionic surfactant.

5. A aquifer DNAPL geo-chemical remedial composition comprising from about a 0.01 % to about a 10.00 % volume of ethylenediamine tetraacetic acid (sodium salt), from about a 0.01 % to about a 10.00 % volume of sodium hexametaphosphate, from about a 0.50 % to about a 95.00 % volume of an acetyl based non-ionic surfactant, from about a 0.50 % to about a 80.00 % volume of d-limonene, and the remainder water.

6. The aquifer DNAPL geo-chemical remedial composition of claim 5 wherein said ethylenediamine tetraacetic acid (sodium salt) is about 0.20 % volume of the final resultant product.

7. The aquifer DNAPL geo-chemical remedial composition of claim 5 wherein said sodium hexametaphosphate is about 1.17 % volume of the final resultant product.

8. The aquifer DNAPL geo-chemical remedial composition of claim 5 wherein said acetyl based non-ionic surfactant is about 17.00 % volume of the final resultant product.

9. The aquifer DNAPL geo-chemical remedial composition of claim 5 wherein said d-limonene is about 25.00 % volume of the final resultant product.

10. The aquifer DNAPL geo-chemical remedial composition of claim 8 wherein said the acetyl based non-ionic surfactant is a Union Carbide Triton SP 140 surfactant, and is present at about 17.00 % volume of the final resultant product.

11. The aquifer DNAPL geo-chemical remedial composition comprising about 0.02 % volume ethylenediamine tetraacetic acid (sodium salt), about 1.17 %
volume sodium hexametaphosphate, about 17.00 % Triton SP 140 surfactant, about 25.00 % volume d-limonene and the remainder water.

12. The method for preparing aquifer DNAPL geo-chemical remedial composition comprising the steps of: adding under agitation from about a 0.01 % to about a 10.00 % volume of ethylenediamine tetraacetic acid (sodium salt) with about a 5.0 % to about a 25.0 % volume of water to produce a first substantially homogeneous mixture, then adding with agitation from about a 0.01 % to about a 10.00 % volume of sodium hexametaphosphate to obtain a substantially second homogeneous resultant mixture; then with agitation, adding from about a 0.50 %
to about a 95.00 % volume of Triton SP 140 surfactant to create a substantially homogeneous resultant third mixture; subsequently still with agitation adding about a 0.50 % to about a 80.00 % volume of d-limonene to create a substantially homogeneous resultant fourth mixture and finally a volume of water to the fourth substantially homogeneous resultant mixture to create the final resultant aquifer DNAPL geo-chemical remedial composition.

13. The aquifer DNAPL geo-chemical remedial composition of claim 12 wherein said ethylenediamine tetraaeetic acid (sodium salt) to act as a chelating agent or sequestering agent in the invention to assist the formulated compound to withstand precipitating effects of commonly present precipitating and scaling agents when used in field or commercial dilution purposes.

14. The aquifer DNAPL geo-chemical remedial composition of claim 12 wherein said sodium hexametaphosphate provides the formulated compound properties such as the ability to deflocculate and suspend insoluble materials, emulsify oils, etc., which aid in the desorption and removal of DNAPLs from soil substrates and additional properties to the formulated compound to promote microbiological growth in the aquifer by acting as a nutrient source.

15. The aquifer DNAPL geo-chemical remedial composition of claim 12 wherein said Triton SP 140 surfactant will form micelles with DNAPL and d-limonene in contaminated aquifers.

16. The aquifer DNAPL geo-chemical remedial composition of claim 15 wherein said Triton SP 140 surfactant micelles with DNAPL and d-limonene can be split into a relatively water-insoluble fraction (hydrophobic) and a relatively water-soluble (hydrophilic) fraction. The water-insoluble fraction comprises an aldehyde and the water-soluble fraction comprises an alkoxylated polyol, and where neither fraction produced from the hydrolysis is surface-active.

17. The aquifer DNAPL geo-chemical remedial composition of claim 16 wherein said Triton SP 140 surfactant micelles with DNAPL and d-limonene can be split into a relatively water-insoluble fraction (hydrophobic) and a relatively water-soluble (hydrophilic) fraction using acids.

18. The aquifer DNAPL geo-chemical remedial composition of claim 16 wherein the micelles foamed by the Triton SP 140 surfactant with DNAPL and d-limonene that are split into a relatively water-insoluble fraction (hydrophobic) and a relatively water-soluble (hydrophilic) fraction using acids, will stop or impede the DNAPL and d-limonene from horizontal migration in the aquifer.

19. The aquifer DNAPL geo-chemical remedial composition of claim 12 wherein d-limonene acts to mix, blend or solubilize with the DNAPL to effectively lower the density of the DNAPL and d-limonene mixture to being lower than that of the original contaminating DNAPL in the aquifer.

20. The aquifer DNAPL geo-chemical remedial composition of claim 19 wherein d-limonene mixing, blending or solubilizing with the DNAPL in the aquifer and the resultant lowering of the combined density can be of sufficient buoyancy to resist or impeded the downward vertical migration of the DNAPL in the aquifer.

21. The aquifer DNAPL geo-chemical remedial composition of claim 12 where d-limonene does not reduce the interfacial tension of water and DNAPL to any substantial extent as to result in the miscibility of the DNAPL in water and not promoting the mobilization of the DNAPL in water

22. The aquifer DNAPL geo-chemical remedial composition of claim 12 wherein water can be used as a diluant for remediation of contaminated aquifers.

23. The aquifer DNAPL geo-chemical remedial composition of claim 12 wherein the components can be used to treat contaminated soils or groundwater in the aquifer.