Method for removing contaminants from water with the addition of oil droplets

A method for removing a contaminant from water includes mixing droplets of a substantially non-water soluble oil with water to combine with the contaminant. The oil can include polar or ionic functional groups. A chemical destabilizer is added to the water to coagulate and aggregate the oil-contaminant mixture. The mixture is then separated from the water by gravity settling, filtration, or dissolved air flotation, thereby removing the contaminant.

BACKGROUND OF THE INVENTION
 There is an increased need to reduce levels of organic contaminants in
 treated industrial wastewater and drinking water. Increased need for
 treatment of industrial wastewater discharge is the result of the National
 Pollution Discharge Elimination System (NPDES) which was established as a
 result of the Clean Water Act of 1972. NPDES controls discharges from
 point sources of water pollution, and focuses its efforts on monitoring,
 enforcing and permitting industries that produce waste water. Two organic
 contaminant classes regulated by NPDES are contaminants leading to
 biochemical oxygen demand (BOD), and fats, oils and greases (FOG). Both
 classes of contaminants can be toxic to humans and the environment, and
 interfere with biologic water treatment systems. Examples of sources of
 FOG and BOD are petroleum and chemical manufacturing, metal-finishing,
 food processing, paper-making and textiles.
 Additionally, new rules proposed by the Environmental Protection Agency,
 under the Safe Drinking Water Act, can lead to increased monitoring and
 regulation of trace organic contaminants in drinking water. Drinking-water
 purification plants throughout the United States and Europe utilize
 chlorine as a primary means of disinfection. However, the chlorine reacts
 with organic contaminants to produce small but significant amounts of
 compounds such as methylene chloride, methyl chloride, methyl bromide,
 bromoform, and dichlorobromomethane, collectively called trihalomethanes
 (THMs). Most THMs are carcenogenic and their concentrations in municipal
 drinking waters must be closely monitored.
 Other organic contaminants in drinking water may be toxic to living
 organisms, or impart unwanted characteristics to water like taste, odor,
 color or turbidity. In addition, contaminants may be biologically active
 pathogenic microorganisms, such as Giardia cysts and Cryptosporidium.
 Sources of contaminants can be, for example, petroleum from rainwater
 run-off or leaf-debris or other natural decaying organic matter.
 Organic contaminants of this type are generally in the size ranges of about
 10.sup.-7 to 10.sup.-2 cm in diameter and are too small to be removed by
 physical filtration. They also resist settling out by gravity. They can
 include a wide range of organic debris with different molecular weights,
 and abilities to form dispersion, polar, hydrogen bonding or other
 inter-molecular interactions. Some can dissolve in water completely,
 others can show partial solubilities due to these polar or hydrogen
 interactions. In addition, there can also be significant amounts of
 surface-active molecular debris that contain hydrophobic and hydrophilic
 components. This debris tends to absorb onto other contaminants and impart
 to them slight but significant polar characteristics, promoting formation
 of meta-stable colloidal suspensions.
 The most economical treatment method for removing these contaminants from
 drinking and waste water is typically chemical destabilization followed by
 gravity settling, filtration or dissolved air flotation. Because
 destabilization chemistry depends on the interactions between polar
 functional groups contained on the contaminants to achieve coagulation and
 flocculation, those that do not carry polar groups are not appreciably
 removed by this chemistry. Additionally, destabilization chemistry can
 only remove contaminants that are not dissolved in water. These two
 factors leave the majority of BOD, FOG, and organic contaminants currently
 outside of the reach of this treatment method.
 SUMMARY OF THE INVENTION
 This invention is a method for treating drinking water and industrial waste
 water using small hydrophobic oil droplets that provides an alternative
 and improved means for removing dissolved and particulate contaminants in
 water treatment systems where chemical destabilization is part of the
 treatment protocol. Additionally this invention enhances the removal of
 contaminants from water when using dissolved air flotation (DAF).
 The method includes adding droplets of a substantially non-water soluble
 oil to contaminated water to form a mixture and to combine with the
 contaminant. A chemical destabilizer is added to the water to further form
 a mixture to aggregate the oil droplets. The oil droplets are then
 separated from the water, thereby removing the contaminant.
 In another embodiment of the method, a substantially non-water soluble oil
 is added to water having a contaminant. A destabilizer is added to the
 water. The oil, water, contaminant and destabilizer are mixed to form
 small oil droplets in the water, wherein the oil droplets combine with the
 contaminant. The oil droplets are separated from the water, thereby
 removing the contaminant.
 A substantially non-water soluble oil is selected, such as an aliphatic
 oil, that has a low solubility in water and a high affinity for the
 contaminants, so that it combines with them, making them effectively
 insoluble in water. The oil is also selected so that it can attain a
 higher affinity for the contaminants when broken into small droplets or
 formed into colloidal structures within the water phase. The oil is also
 selected so that the oil-contaminant mixture can be substantially
 coagulated and aggregated by use of chemical destabilization. The oil is
 further selected so that it coats particulate or droplet contaminants,
 giving these contaminants the ability to be substantially coagulated and
 aggregated by use of coagulation chemistry. The oil is also selected so
 that after chemical destabilization, the oil-contaminant mixture can be
 removed by gravity settling, filtration or DAF. The oil is further
 selected so that it coats particulate or droplet contaminants, making
 their surface more hydrophobic thus making them more susceptible to air
 bubbles attaching to them thus enhancing their removal by DAF. The oil can
 be derived from petroleum sources or from natural sources such as, for
 example, soy beans, coconuts or rapeseeds.
 In a preferred embodiment, the oil used is a C.sub.16-18 Ester derived from
 a natural source. The quantity of oil added to the water is about the same
 as or less than the quantity of contaminant in the water. The oil and
 water mixture is agitated or stirred sufficiently to cause the oil to
 break into droplets that are less than about 0.1 millimeter in diameter.
 The water is then treated with, for example, aluminum sulfate to coagulate
 the oil-contaminant mixture, and, for example, a flocculant, such as
 Magnifloc to aggregate the mixture. This mixture is then removed from the
 water by use of DAF, effectively removing the contaminants from the water.
 DETAILED DESCRIPTION OF THE INVENTION
 While this invention has been particularly shown and described with
 references to preferred embodiments thereof, it will be understood by
 those skilled in the art that various changes in form and details may be
 made therein without departing from the spirit and scope of the invention
 as defined by the appended claims. All percentages and parts are by weight
 unless otherwise indicated.
 An objective of water treatment is to remove contaminants from water so
 that it is biologically and chemically safe for its intended use. Water
 intended for drinking must, of course, be purified to a much greater
 extent than wastewater that is to be discharged to the environment.
 However, even this water must be purified to the extent that the remaining
 contaminants are not toxic to the environment.
 When chemical destabilization is used to purify water, contaminants that
 are either dissolved in the water or that do not carry polar functional
 groups or that have hydrophilic surfaces are not appreciably removed. It
 is the purpose of this invention to extend the capability of chemical
 destabilization to remove these contaminants. These capabilities are
 realized by adding oil to the water that is easily removed by
 destabilization. The oil is selected to combine with or capture the
 contaminants and therefore impart to the contaminants those physical
 quantities that allows them to be removed by use of chemical
 destabilization. Therefore, dissolved contaminants, after combination with
 the oil, become water-insoluble, the surfaces of particles or droplets of
 contaminants in combination with the oil acquire attributes of polar
 functional groups, and also become sufficiently hydrophobic so that air
 bubbles readily attach to them, allowing their removal by DAF or other
 suitable means.
 Mechanisms for the Oil to Combine with or Capture Contaminants Solvent
 Extraction Mechanism
 A feature of this invention is that an oil is added to the contaminated
 water that is substantially insoluble in the water. One purpose of the oil
 addition is to combine with a dissolved organic contaminant to make the
 contaminant become insoluble. In order for this to take place, the
 contaminant must have a higher solubility or affinity for the oil than it
 does for water. Organic compounds dissolve into water because the affinity
 of their polar functional groups for water is stronger than the repulsion
 of their non-polar groups from water. It is also known that increasingly
 longer carbon chain molecules are increasingly more insoluble in water. It
 has been found in this invention that addition of a small amount of
 longer-chain oil to water which contains some types of dissolved organic
 contaminants results in the oil mixing with the contaminants sufficiently
 to make the contaminants insoluble in water. A possible mechanism is that
 the longer chain oils co-dissolve with the dissolved contaminants, giving
 their non-polar portions sufficient repulsion for water to overcome the
 strength of their hydrophilic groups. If insufficient oil is added or if
 the oil does not contain sufficient hydrophobic groups, the contaminant
 can instead make the oil become soluble in water after combination with
 it.
 Droplet Formation Mechanism Surface Area Mechanism
 Another feature of this invention is the ability to break the oils into
 sufficiently small droplets in order to increase the affinity of the oil
 for contaminants. Droplets can be generated through, for example, gentle
 agitation of the oil-water mixture. The oil formed into small droplets
 provides a large area of interface surface between the contaminated water
 and oil, and also provides the opportunity for a substantial majority of
 the oil molecules to come into close proximity and combine with the
 contaminants. Organic contaminants that have some combination of
 hydrophilic and hydrophobic areas of their molecular structure can be held
 along this surface because they are in a lower overall energy state
 residing at a water/oil interface rather than in the bulk water or oil.
 The smaller the oil droplets, the more surface area is generated,
 providing for an increased carrying capacity for contaminants.
 Polar Zone Mechanism
 When the oil droplets are sufficiently small and contain polar
 (hydrophilic) functional groups, it is believed that the oil molecules
 come to be oriented so that their polar groups are closer to surface of
 the droplet, and their hydrophobic groups are closer to the less
 hydrophilic center of the droplet. In droplets that are not more than
 several molecule widths in diameter, the hydrophobic groups or tails of
 the oil molecules may mix together to form a purely hydrophobic droplet
 center while the polar groups form an outer polar shell around the
 droplet.
 This molecular orientation may have a stronger capability for combining
 with the organic contaminants than oils with no polar groups because zones
 of varying polarity are available to compete with the polar groups in
 water for forming more stable, lower energy polar associations with the
 contaminants. These varying polar zones are also available to hold
 contaminants with different ratios of polarity to aliphatic structure. For
 example, the inner hydrophobic core may hold non-polar aliphatic
 hydrocarbons. Semi-polar compounds, such as alcohols and amines, may be
 held near the outside edge of the droplets, and aromatic hydrocarbons,
 such as benzene and toluene, that are strongly hydrophobic yet have strong
 polar sites may be held at both the surface and in the center of the
 droplet.
 Polar portions can consist of a hydrophilic chemical group or combinations
 thereof. Examples of suitable groups are alcohols, glycerides, sterols,
 esters, ethers, aldehydes, ketones, carboxylates, sulfates, and
 sulfonates. Polar groups may be either non-ionic, anionic, cationic, or
 carry both charges, in which case they are called amphoteric.
 A preferred oil containing polar groups is one that has a carbon chain as
 long as possible yet remains liquid, and that has polar groups that are as
 strong as possible without causing the oil to dissolve in water. More
 specifically, a preferred oil would be one with a carbon chain of over 10
 carbon atoms which contains ester functional groups.
 Ionic Mechanism
 Another mechanism proposed for making oils combine with contaminants is to
 use oils with polar ionic functional groups of the opposite charge than
 the contaminants. Organic contaminants that would normally co-dissolve
 with oils would be expected to be rejected by these oils if each had
 strong ionic groups of the same charge. Some level of co-dissolving would
 be expected to take place if the oil had no ionic charge. However, where
 the oil and contaminant have ionic groups that were of the opposite
 charge, the polar ionic groups are expected to form strong associations
 with each other, effectively competing with polar groups in water, and
 thus enhance the preferential combination of the contaminant with the oil.
 While experiments were not performed using oil droplets that contained
 polar ionic groups, it is expected that these droplets will attract ionic
 contaminants of the opposite charge based on experiments reported in the
 literature. For example, in the paper, Antonio Lopes et aL,
 "Multiequilibria of 2-(2-Furanyl)-1H-benzimidazole Neutral and Protonated
 Forms in the Presence of Amphiphillic Aggregates", Environ. Sci. Technol
 26, 2448-2453 (1992), the teachings of which are incorporated herein by
 reference, the solubility of a contaminant containing cationic functional
 groups in an anionic microdispersed organic media is much higher than the
 solubility of the same contaminant with no cationic functional groups. The
 microdispersed organic media consisted of an ionic surfactant, sodium
 dodecyl sulfate, which is soluble in water but forms micellular structures
 when sufficient surfactant is added to the water.
 Retaining and Removing the Droplet Structure
 Another aspect to this invention is the ability to provide the oil with
 sufficiently strong polar groups to allow stabilization of small droplets
 and capture of contaminants, but not so strong as to prevent removal of
 the oil by use of chemical destabilization. These two requirements are
 generally in conflict. If aliphatic oils are agitated in water, the small
 droplets that are formed will quickly coalesce back into large droplets
 and finally to a separate single phase. Addition of water-soluble
 surfactants, such as those used in soaps allows stabilization of these
 small droplets and possibly capture of contaminants. However, chemical
 destabilization has been found to be ineffective at separating these
 mixtures from water.
 Surprisingly, it has been found that use of non-water-soluble surfactants
 allows stabilization of small droplets, capture of contaminants, and
 removal of the oil and contaminants by use of chemical destabilization. To
 achieve this effect, either the oil itself can have functional polar
 groups, or a non-water soluble surfactant can be dissolved into the oil to
 give the mixture polar properties.
 Surfactants can be classified by their hydrophile-lipophile balance (HLB),
 which refers to the relative strengths of their hydrophilic and
 hydrophobic parts. HLB values range from 1 to 40. Surfactants with HLB
 values in the 1 to 4 range are very insoluble in water. Surfactants with
 HLB values in the 5 to 7 range are more soluble in water. When these
 surfactants are added to water, they do not disperse, but remain a
 separate phase. Gentle agitation usually transforms the surfactant into a
 metastable mixture of droplets. Surfactants with HLB values above 10
 generally spontaneously dissolve in water. Surfactants used to emulsify
 water in oil have HLB ranges from 1 to 6; those used to emulsify oil in
 water have HLB values from 8 to 18. Soaps and detergents generally have
 HLB values from 13 to 15.
 Low HLB surfactants are essentially non-water-soluble oils that contain
 polar groups. These oils can be used as is for contaminant removal from
 water according to the method taught in the invention. Surfactants can
 also be mixed with oils to give them increased polar groups resulting in
 an increased capability to combine with contaminants, and to promote the
 capability to form semi-stable suspensions of small droplets in water.
 However, the resulting surfactant-oil-contaminant mixture must be
 substantially less water soluble than the contaminants targeted for
 removal, and the droplets, emulsions or colloidal suspensions formed by
 this mixture must be removable to a substantially greater extent by
 chemical destabilization than the contaminant alone.
 As a guide for retaining the utility of an oil-surfactant mixture to remove
 contaminants from water, the HLB value of the mixture should be less than
 about 10, and preferably less than 6. As a guide for predicting the
 resulting HLB values of mixtures, the effect on HLB values of mixing oils
 and surfactants is generally additive. For example, a first surfactant
 having an HLB value of one and a second surfactant of equal amount having
 an HLB value of 10 would result in a mixture having an HLB value of 5.5.
 This guideline can be used to predict the proper dosages of oil and
 surfactant to use to produce a mixture with the desired HLB value. This
 guideline also suggests that for removal of organic contaminants that have
 a high solubility in water, an oil with a lower HLB value should be used.
 This promotes a sufficiently low enough HLB value of the overall
 surfactant-oil-contaminant mixture to be successfully removed by
 destabilization chemistry.
 An example of a commercially-available group of surfactants is the
 following. The Triton "X-" products, from Union Carbide are alkylaryl
 polyether alcohols, and can be purchased with varying lengths of
 polyoxyethylene chains. The "X" values represent the average number of
 ethylene oxide units. The higher the X number, the higher the HLB value
 and the more soluble the compounds are in water. Triton X-15 has an HLB
 value of 3.6, and is insoluble in water. Triton X-45 has an HLB value of
 10.4 and is borderline in oil or water solubility. Triton X-114 has an HLB
 value of 12.4, and is soluble in water at room temperature.
 In experimental results reported in this invention, oil consisting of
 substantially C16 to C18 aliphatic chains containing methyl ester polar
 groups was used to demonstrate removal of contaminants from water. The
 methyl ester has an HLB value of approximately one, and a water solubility
 of about one part per billion (ppb). While experimental results presented
 herein are based on this single surfactant, it is expected that most low
 HLB surfactants will work with a similar mechanism, and different
 surfactant groups with different polar and ionic functional groups will be
 found to work better for different classes of contaminants.
 Use of Chemical Destabilization to Remove the Combined Oil-Contaminant
 Colloidal Suspensions from Water
 Chemical destabilization as practiced in this invention is the adding of
 chemistry to water to allow the oil-contaminant particles to agglomerate
 into larger groups that can be removed by standard physical means.
 Destabilization is generally a two-step process consisting of first
 coagulation then flocculation. Each step requires separate chemical
 additives, and both can often be enhanced by the use of additional
 chemistries referred to as coagulant or flocculant aids. Once
 destabilization has taken place, the contaminants can be removed by
 physical means, such as sedimentation, filtration, or DAF.
 Definition of Coagulation
 Coagulation uses the addition of water-soluble salts to the water to
 overcome repulsive forces between colloidal particles. These salts are
 often multi-valent metal cations that disassociate in water and are either
 adsorbed directly onto the surface of the colloidal particles or which
 coordinate around them in diffuse electrical layers. The purpose of these
 counter ions is to directly reduce the surface charge or polar strength of
 the colloidal particles, thus reducing the repulsive forces between them.
 This allows coalescing or agglomeration of the particles into larger
 structures, which can then be more easily removed by physical means. In
 this invention, it has been found that these salts can be used to
 destabilize suspensions of oil droplets and their associated contaminants,
 effectively capturing the contaminants in the agglomerated oil mixtures.
 Examples of inorganic chemicals used for coagulation are the polyvalent
 cations of aluminum and iron, and calcium hydroxide. Many natural
 coagulants, such as starch, cellulose, chitosan, polysaccharide gums, and
 proteinaceous materials also act as coagulants. Examples of inorganic
 coagulants include the following: liquid aluminum sulfate, (Al.sub.2
 (SO.sub.4).times.H.sub.2 O) and liquid sodium aluminate, (Na.sub.2
 Al.sub.2 O.sub.4.times.2H.sub.2 O) both available from Holland Chemical,
 Adarns, Mass. Another inorganic coagulant is liquid Ferric Chloride
 (FeCl.sub.3.times.H.sub.2 O) available from Aldrich Inc., Milwaukee, Wis.
 Amounts in the range of 1 to 10 milligrams of coagulant per liter of water
 or parts per million (ppm) are generally sufficient to cause coagulation,
 but the exact dosage for a given water sample must be determined by
 laboratory testing.
 Definition of Flocculation
 Particles agglomerated by coagulation chemistry alone can produce weak
 aggregates that are easily upset during attempts at their physical removal
 from the water. Therefore, flocculants are used to mechanically bring
 together the coagulated particles, and enmesh them in a matrix
 sufficiently strong to withstand the contaminant removal process.
 Flocculants are large, high-molecular weight water-soluble polymers
 containing many polar groups, such as polyacrylamide. The polymers react
 with the particles by attaching to ionic or polar adsorption sites found
 on them. A bridge is formed when two or more particles become adsorbed
 along the length of the polymer. Bridged particles become intertwined with
 other bridged particles during the flocculation process. The size of the
 three-dimensional particle grows and water is moved out of the structure.
 These polymers can also serve to lower the charge or polar strength of
 coagulant particles, thus further facilitating the
 coagulation-flocculation process.
 After the flocculant is added to water, the water must be physically
 agitated in some way to bring together the coagulated particles to form
 the larger agglomerated particles. This can be accomplished by simple
 stirring, or by bubbling air through the water.
 Examples of polymer flocculants include Magnifloc 496C, Magnifloc 1555C,
 Magnifloc 1839A, Magnifloc 835A, Percol LT 22S, Percol LT 20, and Betz
 713. The Magnifloc products are available from Cytech Chemical, Wayne,
 N.J., the Percol products from Allied Colloids, Suffolk, Va., and Betz 713
 product from Betz Paperchem, Inc., Rindge, N.H. Dosages of flocculants in
 the range of one to ten ppm are generally sufficient, but the exact dosage
 for a given water sample must be determined by laboratory testing.
 Definition of Destabilization Aids
 It has also been found that both coagulation and flocculation of droplets
 and their associated contaminants can often be enhanced by the use of
 chemistries referred to as coagulant aids or flocculant aids. These
 chemistries can act as coagulants or flocculants themselves, but in
 combination with the primary coagulants and flocculants, a stronger and
 more robust removal of contaminants is realized.
 An example of a coagulant aid is Bentonite clay, which is a hydrated
 aluminum silicate having the generalized formula Al.sub.2 O.sub.3
 SiO.sub.2 -XH.sub.2 O. This is available under the trade name Altafloc
 from Closed Systems, Inc., Trussville, Ala. Other types of coagulant aids
 include Kaolinite Clay available from Kaopolite Inc, Union, N.J.;
 Montmorillonite Clay available from Nalco Chemical, Naperville, Ill.;
 Carboxymethylcellulose available from Closed Systems, Inc.; Activated
 Silica available from Aldrich Inc., Milwaukee, Wis.; and Activated
 Bentonite available from Allied Colloids Inc., Fairfield, N.J. Clay
 dosages in the range of 10 to 50 ppm are generally sufficient, but the
 exact dosage for a given water sample must be determined by laboratory
 testing.
 Use of Flotation to Remove Coagulated Contaminants
 Dissolved Air Flotation (DAF) as practiced in this invention is the
 introduction of water with a high concentration of dissolved, air into the
 bottom of a column of the water and oil-contaminant suspension. The air is
 released from the water causing small air bubbles to be formed. The air
 bubbles as they rise up are attracted to and attach to the surfaces of the
 oil droplets, thus making them buoyant, and lifting them to the surface of
 the water column for removal by, for example, skimming.
 Advantages of Contaminant Removal by this Invention
 An advantage of the present method is that it can be used with existing
 water treatment systems where the capability of the system to remove
 organic contaminants is dramatically increased at the cost of only adding
 the additional chemistry. As an example, in potable water treatment in
 many facilities, alum or other conventional coagulants are added to reduce
 color and trace organic contaminants before chlorinating to reduce levels
 of trihalomethanes. Carbon bed filters are often used downstream to remove
 additional organic contaminants. Use of a non-water soluble aliphatic oil
 with polar groups, as taught by this invention, can remove substantially
 all color and turbidity, and also can provide a more effective and less
 expensive approach than carbon beds to remove organic contaminants that
 lead to THM's. The oil is added to the water in an initial treatment step,
 where it combines with the trace organics. The oil, water and contaminant
 are subjected to a destabilizer. The destabilizer can include a
 flocculant, coagulant or coagulant aid, where it combines with other
 coagulated contaminants in a hydrophobic phase. In one embodiment, the oil
 can be added to the water first and then the destabilizer can be added.
 Alternatively, the destabilizer can be added to the water first and then
 the oil can be added. In another embodiment, the oil and the destabilizer
 can be mixed with one another and then added to the water. All methods
 result in a hydrophobic phase forming in the water. The hydrophobic phase
 is separated from the water, such as by sedimentation or a downstream sand
 bed or other filtration media to remove the contaminants.
 While not tested, it is believed that biologically active pathogenic
 material, which is organic in nature, may also be removed by the methods
 taught in this invention. Biologic contaminants may include for example
 bacterial, viral, DNA, and RNA material. Bacterial and viral particles are
 not considered dissolved in water, however because of their small size (10
 microns and below) and high water content, they easily remain suspended in
 water, do not settle out with gravity and cannot be easily removed by
 physical filtration. DNA and RNA fragments can be as small as 20
 nucleotides in length and still contain biologically active gene sites.
 These particles carry hydrophilic phosphate ester functional groups, which
 render them soluble in water. Adding oxidants to water like chlorine,
 permanagante or ozone can inactivate most of these biologic contaminants,
 however some, like Giardia cysts and Cryptosporidum can withstand exposure
 to these oxidants and still retain pathogenic activity.
 As these contaminants are substantially made up of long-chain hydrocarbon
 molecules, it is expected that they can be removed from water using the
 methods taught in this invention. Oils with or without functional polar
 groups would be added to water to combine with these types of
 contaminants, making them less soluble in water, more susceptible to being
 captured and agglomerated by destabilization chemistry, and removable from
 water by DAF.
 Use of the Partition Coefficient for Measuring the Efficiency of the
 Contaminant Removal Process.
 In a traditional solvent-extraction process, the efficiency of removal of a
 solute from one solvent to another solvent is related only to its
 solubility in the two solvents. If the solubility is the same in both
 solvents, equal volumes of solvents will hold equal volumes of solute. If
 the solubility of the solute is ten times higher in the first solvent,
 then that solvent can hold ten times the solute as an equal volume of the
 second solvent, when both solvents are mixed together.
 A useful measure for the efficiency of contaminant removal by solvent
 extraction is the Partition Coefficient. This coefficient is defined as
 the ratio of the solubilities of the solute in the first and second
 solvents of interest, and is a physical constant for a given pressure and
 temperature. The larger the value of the partition coefficient, the less
 volume of the first solvent is needed to extract solute from the second
 solvent. Thus the partition coefficient is a strong indicator of the
 efficiency at which a solvent extraction process can be performed.
 This same concept can be used to evaluate the efficiency of contaminant
 removal in this invention. The volume of contaminant that is removed by
 the treatment process is divided by the volume of contaminant remaining in
 the water after treatment. This ratio multiplied by the ratio of water
 volume to oil volume gives an apparent partition coefficient or ratio of
 the apparent solubility of the contaminant in the oil to the apparent
 solubility of the contaminant in the water. This coefficient is not a
 physical constant and for a given oil will vary not only with temperature
 and pressure, but will also vary with oil droplet size, destabilization
 chemistry, and parameters of the DAF process. It can, however, be used to
 compare types of oils and chemistry schemes for their contaminant removal
 efficiency. Also it can be used to compare the contaminant removal process
 described in this invention with traditional solvent extraction
 efficiencies.

EXPERIMENTAL RESULTS
 A series of qualitative screening tests were performed on a selection of
 non-soluble oils of varying HLB values and polar functional groups for
 their abilities to remove organic contaminants from water. Examples of
 oils tested are C6 to C24 fatty acids, unsplit fats and oils, mono-, di-
 and triglycerides, sterols and phenolic organic compounds. All these oils
 were found to preferentially combine with organic contaminants in water.
 Additionally, it was shown that these oils and their associated
 contaminants could be removed by use of destabilization chemistry.
 Then a C16 to C18 carbon chain length oil containing ester polar groups
 (methyl ester) was tested for its capability to remove organic
 contaminants from a wide range of natural and industrial wastewater
 sources. Some of the results of these experiments are reported here.
 Three protocols were used in this testing, which are given below. The first
 details how the ester was added, or spiked into the contaminated water.
 The second details the coagulation and flocculation procedures. The third
 details the procedure used for Dissolved Air Flotation of the oil and
 contaminants out of the water.
 Spiking Procedure
 All oils were spiked neat (no dilutions prior to administration). A
 standard spiking process was performed as follows:
 1. 20 mls of test water sample was transferred into a 100 ml disposable
 aluminum weighing dish.
 2. The weighing dish was then transferred to a digital Mettler AC 100
 balance (readability 0.1 milligram, (mg)).
 3. The oil was then added in a drop-wise fashion using a 1 ml pipette until
 the desired weight was obtained.
 4. The aluminum weighing tin was then removed from the balance and was
 slowly decanted into a 1,000 ml amber glass container with a threaded cap
 and seal.
 5. The aluminum dish was then rinsed with additional sample to ensure
 quantitative transfer. All rinses were decanted into the 1,000 ml amber
 glass container with threaded cap and seal.
 6. The amber container was sealed and agitated by gentle shaking (i.e., one
 shake per second for 90 seconds) or by vigorous shaking (i.e., three
 shakes per second for 60 seconds), depending on the requirements for a
 given experimental item.
 7. After complete mixing, the sample was immediately utilized for a given
 procedure. Spiked samples were not stored prior to experimentation.
 8. 1,000 ml amber mixing containers were first cleaned with detergent,
 scrubbed with a tubular cleaning brush, and rinsed six times with hot tap
 water, then rinsed six times with distilled water and allowed to air dry.
 9. After drying each container, cap and seal were rinsed with virgin Freon
 113 and allowed to dry. Containers were then visually inspected for any
 visible signs of dirt or oil droplets. If containers were visually
 suspect, the cleaning process was then repeated.
 Coagulation Procedure (25 ml test level)
 1. 25 mls of test sample were decanted into a 75 ml culture tube with a
 screw cap and Teflon.TM. seal.
 2. A 1% solution (by weight) (using Milli-Q water as the diluent) of given
 coagulant was then drawn up into a 1 ml calibrated pipette and slowly
 dosed into the 75 ml culture tube containing the test sample. The culture
 tube was inverted at a rate of one agitation per second and periodically
 inspected over a 100 watt light source.
 3. A sufficient quantity of coagulant caused the particulate matter within
 the sample to agglomerate, thereby producing a visible precipitate. An
 overall improvement in sample clarity was also observed at this point.
 Flocculation Procedures (15 ml test level)
 1. The coagulated sample was then evaluated for shear resistance by
 utilizing vigorous shaling. If the precipitate appeared only moderately
 stable after vigorous agitation the sample was then treated with
 flocculants to further increase shear resistance.
 2. All flocculants were dosed in diluted form. Typically 1.0% solutions (by
 weight) (using Milli-Q water as the deluent) were utilized for standard
 bench testing. Flocculants can be extremely viscous materials therefore
 care was taken to ensure that complete delivery into the testing sample
 had been accomplished.
 3. Flocculant dosages were generally kept within 2-5 ppm dosing range. The
 overall goal was to add just enough flocculant to the destabilized
 solution to further agglomerate the destabilized particles.
 4. The flocculant was introduced into the 75 ml culture tube which had been
 previously treated with the predetermined amount of coagulant. The
 flocculant was dosed into solution via a 1 ml disposable plastic pipette.
 5. The sample was then inverted at a rate of once per second until the
 aggregate participate size was maximized and optimum shear resistance was
 achieved.
 Coagulation and Flocculation Procedures (1,000 ml test level)
 1. Having found the proper combination of coagulant/flocculant, the system
 was now scaled up to the 1,000 ml test level.
 2. 1,000 mls of test sample was placed on a Bird-Phipps paddle mixing
 apparatus with illuminated fluorescent base and was paddle mixed at 100
 revolutions per minute (rpm) until all suspended matter was uniformly
 distributed.
 3. Once uniformity had been achieved, the samples mixing velocity was
 increased to 300 rpm and a dosage of coagulant, as determined in the 25 ml
 test level, was transferred via a 10 ml plastic pipette to the mixing
 sample.
 4. The mixture was allowed to flash mix at 300 rpm for 60 seconds and the
 mixing velocity was then reduced to 30 rpm.
 5. The sample was now visually inspected for the formation of the
 precipitate. Once the precipitate had formed, the sample was ready for the
 addition of the flocculant which was also determined in the 25 ml test
 level.
 6. The mixing velocity of the destabilized sample was then increased to 300
 rpm.
 7. The flocculant was dispensed into the mixing system via a 1 ml plastic
 pipette and allowed to flash mix for 5 seconds. After the five second
 interval had lapsed, the mixing velocity was reduced to 30 rpm and the
 sample was allowed to react for an additional 25-30 seconds.
 8. The optimum precipitate morphology should be virtually identical to that
 developed in the 25 ml test level. The sample was now ready to be
 submitted to the dissolved air flotation simulation.
 Dissolved Air Flotation Procedures
 1. 800 mls of the treated sample was then transferred to a 1,000 ml
 Nalgene.TM. graduated cylinder which had been fitted with a 1/4 inch
 barbed end with pinch clamp.
 2. The sample was transferred into the graduated cylinder as rapidly as
 possible. 25% recycle pressurization was achieved by the introduction of
 200 mls of aerated water via a brass introduction wand.
 3. The recycle water was produced in the following manner: A two-gallon
 metal pressure canister was filled with 4 liters of Milli-Q water. The
 canister was then pressurized with compressed atmospheric air to 60 pounds
 per square inch (psi). The pressure canister was then manually shaken
 until a pressure drop of 10 psi was obtained. The system was then
 pressurized once again with compressed air until the pressure once again
 read 60 psi. The canister was manually shaken a second time until a
 pressure drop of about 5-10 psi was obtained. The canister discharge hose
 was then bleed until the resulting discharge was milky white in color. The
 recycle water was then ready for introduction into the flotation cylinder.
 4. The recycle stream was allowed to contact the chemically treated sample
 for approximately 3-4 minutes.
 5. A flotation rate was then determined by observing the distance at which
 the precipitate traveled in the first minute of flotation. Excellent
 flotation rates were normally of the order of 10-12 inches the first
 minute after complete introduction of the recycle stream.
 6. After the 4-5 minute contact time had lapsed, the resulting sludge layer
 volume was measured and approximately 100 mls of subnatent was wasted from
 the pinch value at the bottom of the cylinder. The first 100 mls of
 treated sample was wasted to insure that no solids became trapped in the
 barbed end during the flotation process.
 7. The remaining sample was then drawn from the system into clean glass
 (I-Chem.TM.) storage containers.
 8. The following volumes of sample and recycle water constituted 25% and
 33% recycle pressurization. 800 mls of chemically treated sample to 200
 mls of recycle water equaled 25% recycle pressurization, 750 mls of
 chemically treated sample to 250 mls of recycle water equaled 33% recycle
 pressurization.
 9. For samples that had been treated by means of "DAF only", it was
 understood that no chemical treatment steps were completed prior to the
 DAF simulation.
 Analytical Test Procedures
 The following laboratory procedures were used to quantify the amount of
 contaminants present in the water being tested, before and after
 treatment. Fats, Oil & Grease (FOG) measured in mg/liter, EPA method 413.1
 Total Petroleum Hydrocarbons (TPH) measured in mg/liter, EPA method 418.1
 Apparent Color, measured in PCU units, EPA method 110.2 Turbidity,
 measured in NTU units, EPA method 180.1 Trihalomethane Formation Potential
 (THMFP), measured in mg/liter, EPA method 602.2
 Study 1--Removal of Methyl Ester from Distilled Water by Gravity, DAF, and
 Destabilization Chemistry with DAF
 In the use of this invention it is important to have the capability to
 quickly and easily remove the combined oil and contaminant mixture from
 the water being treated. This step was modeled by testing the ability of
 gravity, DAF and DAF combined with destabilization chemistry to remove
 1,000 ppm of methyl ester from water. FOG measurements were performed on
 the water samples to determine the levels of methyl ester remaining in the
 water after treatment.
 The results are shown in Table 1. In the first test, 15 minutes of gravity
 settling removed 65% of the ester from the water. In the second test, DAF
 alone removed 85% of the ester.
 TABLE 1
 Comparison of Gravity Settling, DAF, and Destabilization
 Chemistry with DAF to Remove Methyl Ester from Water.
 Gravity DAF DAF
 15 min Only and Destabilizer
 ppm in 1,000 1,000 1,000
 ppm out 346 152 75
 % Removal 65.4% 85% 92.5%
 In the third test, DAF in combination with destabilization chemistry
 removed 92% of the ester within two minutes. The coagulant dosage was
 fifty ppm of Altafloc, and the flocculant dosage was 2 ppm of Magnifloc
 496C.
 These results show that a meta-stable colloidal structure was formed by the
 ester in the water that resisted settling out by gravity. When DAF was
 applied, much more ester was removed. However, the greatest amount removed
 was by use of destabilization chemistry which prepared the ester for
 removal by DAF by agglomerating the ester into droplets large enough to be
 captured and removed by the DAF process.
 Study 2--Removal of Non-Polar Oils and Methyl Ester from Distilled Water by
 Destabilization Chemistry with DAF
 This study explored the importance of polar groups in oils for their
 efficient removal by destabilization and DAF. Several oils made up of
 aliphatic carbon chains approximately 10 to 20 carbons long were compared
 to the 16 to 18 aliphatic carbon chain oil containing ester polar groups
 for removal efficiencies from distilled water. The procedure used was the
 same as that of Study 1, except that the coagulant was 100 ppm of
 Altafloc, and the flocculant was 3 ppm of Magnifloc 496C.
 These results are disclosed in Table 2. The petroleum, olive oil, and
 vegetable oil contained no polar groups, and were only partially removed
 by destabilization. The methyl ester was almost completely removed. These
 results strongly support the importance of polar groups in the oils for
 their removal by destabilization chemistry.
 TABLE 2
 Comparison of Non-Polar Oils and Methyl Ester from
 Distilled Water by Destabilization Chemistry with DAF
 Methyl Olive Vegetable
 Ester Petroleum Oil Oil Oil
 ppm in 100 100 100 100
 ppm out 6 32 79 77
 % removal 94% 68% 21% 23%
 Study 3--Removal of Oils Combined with a Polar Oil from Potable Water by
 Destabilization Chemistry with DAF
 In this study the effects of mixing 1 part of a polar oil with 10 parts of
 a non-polar oil were studied in order to determine the effect of adding
 polar functional groups to the oils. The oils, ester, destabilization
 chemistry type, and dosages were the same as in Study 2. As is shown in
 Table 3, In every case, there is a dramatic increase in the removal of the
 oil when ester is mixed with the oil. The water used was raw potable water
 drawn from the eastern Lenox Mountain reservoir in Lenox, Mass.
 TABLE 3
 Comparison of Removal of Oils Combined with a Polar Oil
 from Potable Water by Destabilization Chemistry with DAF
 Oil Oil Ester Oil Percent
 Type initial ppm ppm final ppm Removed
 Petroleum 100 0 55 45%
 Oil 100 10 &gt;1 99%
 1,000 0 234 77%
 1,000 100 &gt;1 100%
 Olive Oil 100 0 68 43%
 100 10 12 88%
 1,000 0 263 74%
 1,000 100 &gt;1 100%
 Vegetable 100 0 67 33%
 Oil 100 10 &gt;1 99%
 1,000 0 148 85%
 1,000 100 &gt;1 100%
 Study 4--Use of Non-Polar and Polar Oils to Remove Contaminants from Water
 by Destabilization Chemistry with DAF
 In Studies 1-3, it was shown that oils containing polar groups (ester) are
 removed from water much better than non-polar oils when using
 destabilization with DAF. In this study, the capability of polar and
 non-polar oils to remove contaminants from water was explored.
 Two aliphatic oil types with no polar groups were used. The first was a
 light volatile mid-range naphtha solvent. The second was a medium-weight
 non-volatile petroleum oil, similar in chemical characteristics to
 vegetable oil. The oils were added to paper mill waste water and
 industrial metal fabrication wash water, then gently shaken. The
 contaminants in the paper mill water were mostly natural-based fats and
 oils. The contaminants in the metal fabrication wash water were mostly
 petroleum-based cleaning solvents and oils. For the mill samples, the
 flocculant dosage was 5 ppm of Magnifloc 1555, and no coagulant was used.
 For the industrial samples, the coagulant dosage was 400 ppm of aluminum
 sulfate and 200 ppm of sodium aluminate. The flocculent dosage was 5 ppm
 of Magnifloc 496. The same process was repeated where the oils were first
 mixed with ester in the proportion of 10 parts oil to 1 part ester, before
 addition to the water. All samples were then subjected to DAF. For the
 light oil, total petroleum hydrocarbons (TPH) were measured. For the heavy
 oil, fats oils and greases (FOG) were measured.
 The results, disclosed in Table 4, display a dramatic increase in
 contaminant removal, and partition coefficient when ester is added to the
 oils. For the Mill waste and light oiL the partition coefficient is almost
 ten times higher. For the heavy oil, the partition coefficient is almost
 fifty times higher. Similar values were obtained for the industrial water.
 Several conclusions can be drawn from the exceptionally high partition
 coefficients. Firstly, partition coefficients quoted in the literature for
 conventional solvent extraction are generally in the range of tens to
 hundreds. Those measured in this experiment are much higher, even for the
 straight oils. This provides strong evidence that the droplet mechanism
 used in this invention can reach much higher partition coefficients than
 conventional solvent extraction systems. When the ester is added to the
 oils, partition coefficients go up into the millions, which is unheard of
 in conventional solvent-extraction practice. This provides strong evidence
 that the polar groups in the oil specifically significantly increase the
 amount of contaminant that associates with the oil droplets.
 TABLE 4
 Comparison of Use of Non-Polar and Polar Oils to Remove
 Contaminants from Water by Destabilization Chemistry with DAF
 FOG/ FOG/
 Oil ester TPH TPH % FOG/ Partition
 Water Oil added added initial final TPH Co-
 type Type ppm ppm ppm ppm removed efficient
 Mill Light 100 0 33.3 26 23% 2,910
 Heavy 100 0 74 65 12% 1,380
 Light 100 10 33.3 10 70% 21,200
 Heavy 100 10 74 9 88% 65,700
 Indus- Light 100 0 1430 144 90% 89,300
 trial Heavy 100 0 548 65 88% 74,300
 Light 100 10 1430 7 100% 1,990,000
 Heavy 100 10 548 1 100% 4,960,000
 Study 5--Removal of Petroleum Contaminants from Groundwater
 Table 5 discloses the results of tests performed using ester,
 destabilization chemistry and DAF to remove the remains of a fuel oil
 spill from ground water. The spill was near the seashore, and experienced
 influx and outflux of seawater. The fuel oil had probably lost most of its
 volatiles leaving only heavy oils behind. The petroleum was fully
 dissolved in the water, and the water appeared clear. The samples were
 coagulated with 250 ppm of Altafloc, and flocculated with 5 ppm of
 Magnifloc 496C.
 The results are shown as a function of increasing amounts of ester used to
 remove the contaminants. Use of destabilization chemistry and DAF alone
 removed 46% of the contaminants. This is typical of levels of petroleum
 contaminant removal achievable with destabilization chemistry in general
 waste water treatment applications. Adding ester enhanced the contaminant
 removal capability, lowering remaining contaminant levels down to below 5
 ppm, which is an EPA limit for discharge of waste water to the
 environment. Levels of the ester and contaminants in the water were
 determined by measuring FOG.
 TABLE 5
 Comparison of Removal of Petroleum Contaminants from Groundwater
 Con- Con- Ratio of
 taminant Ester taminant Contaminant Partition Ester to
 initial ppm ppm final ppm Removed Coefficient Contaminant
 72.5 0 38.8 46%
 72.5 10 15.8 78% 359,000 0.14
 72.5 100 6.1 92% 109,000 1.38
 72.5 1,000 2.4 97% 29,200 13.79
 The partition coefficient again is much higher than found in conventional
 solvent extraction processes. However, it dropped off as increased levels
 of ester were added to the water, indicating less affinity of the
 contaminant for the ester with increasing levels of ester.
 It is believed that the cause of this drop in partition coefficient is due
 to a water-in-oil emulsion being formed within the ester droplets, when
 the ratio of ester to contaminant is high. As the ester has a low HLB, it
 forms water-in-oil emulsions when mixed with water. When there is a high
 level of contaminant present, it is believed that it drives out the water
 in the ester, making the center of the ester droplets more hydrophobic,
 making the solvent partition coefficient higher. This implies that in this
 experiment a higher partition coefficient could have been maintained if a
 straight aliphatic oil were mixed with the ester, to lower the amount of
 water emulsifying in the oil, but still retain the capability to remove
 the oil with destabilization. Thus less ester may have been required for
 equivalent contaminant removal.
 Study 6--Removal of Organic Contaminants from Industrial Laundry Wastewater
 #1
 Table 6 discloses the results of tests performed using destabilization
 chemistry and ester to remove industrial laundry contaminants from water
 by DAF. The contaminants were generally petroleum-based cleaning solvents,
 heavy oils and greases, and printing inks, in combination with soap
 residuals from the cleaning process. The soap residuals were water-soluble
 surfactants. Even though these contaminants had gone through a hot water
 washing operation, a substantial quantity of volatile organic residuals
 remained in the water, mostly in a stable emulsion form. The coagulant
 dosage was 1,000 ppm of aluminum sulfate, the coagulant aid dosage was 500
 ppm of Altafloc, and the flocculant dosage was 5 ppm of Magnifloc 496C.
 Levels of the ester and contaminants in the water were determined by
 measuring FOG.
 The results are shown first with no ester added, then with increasing
 amounts of ester added. While the contaminants were substantially not
 soluble in water, only 57% could be removed with destabilization chemistry
 alone. Adding only 10 ppm of ester to the water allowed substantial
 removal of the contaminant, producing a partition coefficient in the
 hundred million range. The ester may have assisted the contaminant removal
 in several different ways. For example, it may have countered the effect
 of the residual water-soluble surfactants (soaps) allowing coagulation to
 take place. It may have provided a sufficient number of polar groups to
 the contaminant to allow the flocculant to work more effectively, or it
 may have added sufficient hydrophobicity to the contaminants to allow the
 DAF bubbles to more easily attach to them for increased removal. Addition
 of 100 ppm of ester to the water did not result in as good removal as 10
 ppm of ester. It is believed that the amount of ester present in the water
 became too high to be adequately removed by the levels of chemistry used
 in these experiments.
 TABLE 6
 Comparison of Removal of Organic Contaminants from
 Industrial Laundry Wastewater #1
 Contam Ester Contam Contam Coll. Part.
 initial ppm ppm final ppm Removed Coefficient
 1630 0 700 57%
 1630 10 &gt;1 100% 163,000,000
 1630 50 &gt;1 100% 32,600,000
 1630 100 17 99% 949,000
 Study 7--Removal of Organic Contaminants from Industrial Laundry Wastewater
 #2
 Table 7 discloses the results of tests performed using destabilization
 chemistry and ester to remove contaminants from a second sample of
 Industrial Laundry Waste Water. The laundry used a similar washing
 process, as that in Study 6, but used different soap chemistries. The
 initial coagulant dosage was 600 ppm of aluminum sulfate, the initial
 coagulant aid dosage was 300 ppm of Altafloc, and the initial flocculant
 dosage was 53.5 ppm of Magnifloc 496C. Levels of the ester and
 contaminants in the water were determined by measuring FOG.
 The test protocol first increased the amount of ester added to the waste
 water while holding the amount of destabilzation chemistry added constant.
 Then the amount of destabilization chemistry was increased while holding
 the amount of ester added constant. In the first set of experiments the
 addition of low amounts of ester resulted in an initial increase in the
 amount of residual contaminants remaining in the water after treatment.
 When the amount of ester reached a sufficient level, the amount of
 residual contaminant began to decrease. This break point may have been the
 result of remaining water soluble surfactants (soaps) in the water. At low
 levels of ester addition, these surfactants may have co-dissolved with the
 ester, possibly interfering with the capability of the ester to promote
 removal of the contaminants. When sufficient ester was added, the
 surfactant-ester combination may have finally become insoluble enough or
 polar enough to be acted upon by the destabilization chemistry.
 In the second set of experiments it was demonstrated that the amount of
 contaminant removed increases up to a point with amount of coagulation
 chemistry added. However, a limit is reached where larger doses of
 chemistry do not increase contaminant removal.
 TABLE 7
 Comparison of Removal of Organic Contaminants from
 Industrial Laundry Wastewater #2
 Percent of initial Contam Contam.
 Destabilization initial Ester Final Contam Partition
 Chemistry ppm ppm Ppm Removed Coefficient
 100% 2497 0 625 75%
 100% 2497 30 842 66% 65,500
 100% 2497 40 438 82% 118,000
 100% 2497 50 17 99% 2,920,000
 20% 2497 50 867 65% 37,600
 50% 2497 50 771 69% 44,800
 75% 2497 50 575 77% 66,900
 100% 2497 50 17 99% 2,920,000
 200% 2497 50 17 99% 2,920,000
 Study 8--Removal of Trihalomethanes, Color and Turbidity from Drinking
 Water
 Table 8 discloses the results of tests performed using destabilization
 chemistry and ester to remove contaminants from potable water. Potable
 water treatment is usually performed by addition of alum, followed by
 gravity settling, mechanical filtration, or treatment with dissolved air
 flotation. One significant contaminant group tested was trihalomethanes
 (THMs) formed by the reaction of chlorine added to the water on dissolved
 organic contaminants present in the water. THMs are known carcinogens, and
 their levels in drinking water are regulated to be below 100 parts per
 billion (ppb) by the USEPA. Examples of THMs are methylene chloride,
 methyl chloride, methyl bromide, bromodichloromethane, bromoform,
 chlorodibromomethane, and chloroform. Another type of contaminant tested
 was Apparent Color, measured in PCU units, which is often a result of
 tannic, humic and fulvic acids present in the water, which form as a
 result of the breakdown of soils and vegetation. A third contaminant
 tested was turbidity, measured in NTU units, which is colloidal material
 that may be a combination of organic and mineral material.
 The water used in the first set of experiments was raw potable water drawn
 from the eastern Lenox Mountain reservoir in Lenox, Mass. The coagulant
 dosage was 100 ppm of Altafloc. The flocculant dosage was one ppm of
 Percol LT22S. Removal of the ester-contaminant mixture was by DAF. The
 addition of flocculant without ester resulted in an increase in THM's,
 because the flocculant itself is an organic contaminant not fully removed
 by DAY. An increase in THM's as a result of flocculant addition in
 municipal drinking water treatment plants is a well known phenomenon.
 Flocculant is added to reduce turbidity and color. In most cases a balance
 must be sought between the level of turbidity and color removed versus the
 increase in THM's that can be afforded by dosing with a flocculant.
 However, addition of ester with the flocculant caused a reduction rather
 than increase in THM's. One ppm of ester reduced the THM's to below 2 ppb,
 and 5 ppm of ester reduced the THM's to below 1 ppb.
 The water used in the second set of experiments was raw potable water drawn
 from the Merrnmac River water inlet to the Lawrence, Mass. Potable Water
 Treatment plant. The coagulant dosage was 30 ppm of aluminum sulfate, and
 no flocculant was used. Physical filtration through a bed of granular
 activated carbon (GAC) was used to remove the ester-contaminant
 combination from the treated water. These treatment methods were chosen to
 simulate water treatment procedures used at most potable water treatment
 facilities. Coagulation and GAC filtration alone achieved a THM removal
 level of 31%. Addition of one ppm of ester resulted in THM removal of only
 17%. However, addition of 5 and 10 ppm of ester increased the THM removal
 levels over the initial treatment to 39% and 45% respectively.
 Two things worked against the ester being as effective as with DAF. First,
 no flocculant was used to agglomerate the ester droplets. Second, GAC was
 used to remove the ester, rather than DAF. Therefore, microscopic ester
 droplets may not have become agglomerated into larger droplets, and those
 small droplets could have slipped through the GAC filter without being
 trapped.
 TABLE 8
 Comparison of Removal of Trihalomethanes, Color and Turbidity from Drinking
 Water
 Contam. Contam.
 Removal Contam. Initial Ester final Contam. Partition
 Method Type ppm ppm ppm Removed Coefficient
 Dissolved THMs 0.0897 0 0.099 -10%
 Air 0.0897 1 0.0019 98% 46,200,000
 Flotation 0.0897 5 0.0008 99% 22,200,000
 GAC THMs 0.0489 0 0.0336 31%
 Filtration 0.0489 1 0.0407 17% 201,000
 0.0489 5 0.0298 39% 128,000
 0.0489 10 0.027 45% 81,100
 Turbidity 1.6 0 1.7 -6%
 (NTU) 1.6 1 0.3 81% 4,330,000
 1.6 5 0.3 81% 832,000
 1.6 10 0.3 81% 433,000
 Color 31 0 20 35%
 (PCU) 31 1 6 81% 4,170,000
 31 5 7 77% 686,000
 31 10 4 87% 675,000
 The ability of coagulation and filtration in combination with the ester to
 remove color and turbidity from the potable water samples was also tested.
 Both of these were reduced by 81% by the addition of one ppm of ester.
 This out-performed the ability of the GAC to remove these contaminants by
 a substantial margin. The Environmental Protection Agency guideline for
 color in drinking water is not more than 5 PCU. The water treatment
 without use of ester only reduced color to 20 PCU, while with ester it was
 reduced to 6 PCU. The Environmental Protection Agency strictly enforced
 guideline for turbidity is 0.5 NTU. The water treatment without use of
 ester actually increased turbidity from 1.6 to 1.7 NTU. Use of 1 ppm of
 ester reduced turbidity to 0.3 NTU, well under the federally mandated
 guideline.
 Currently when Potable Water Treatment Plants are above federal limits for
 THMs in their treated water, they must resort to costly pre and post
 treatment options. These steps can be costly, requiring potential addition
 of new contact basins, new hazardous chemicals, such as ozone, and
 additional process and monitoring equipment. An alternative method for
 lowering THMs in the treated water, suggested by the results of these
 experiments, is to use, for example, methyl ester, as part of the chemical
 treatment package.