Composition and Method for Purifying Water

1. Field of the Invention

The present invention relates to compositions which are useful for purifying turbid and/or polluted water to clarify and make such water suitable for drinking. In particular, the present invention is directed toward a formulation and use thereof which is advantageously formulated for purifying small quantities of water for personal use, such as would be necessary in emergency situations encountered by campers, military personnel and other who find themselves in a situation where the only drinking water available is contaminated with turbidity causing materials and other pollutants.

2. Background of the Invention

Various types of water purification ingredients are known for removing particular types of pollutants from water. Typically, such ingredients are utilized in large scale water purification facilities to remove specific pollutants encountered in a particular source of water. For example, flocculants or coagulants are known to be useful for removing particulate contaminants found in some sources of water before such water can be discharged into a lake or stream. Likewise, various types of adsorbants are available for removing certain types of pollutants.

Typical procedures for using conventional water purification chemicals require operation under carefully controlled conditions and generally involve operation of expensive equipment which can be complicated to operate. The useful chemicals for purifying the water are generally not combined with each other since they typically require conditions during the purification process which may not be suitable for the other ingredients. Thus, many operations require sequential use of each ingredient as needed and the physical conditions for each sequential step are adapted to meet the functional or physical limitations of each ingredient.

In some instances a combination of ingredients has been formulated into a single composition. However, the combination of ingredients in these compositions is very limited and such compositions are often in a physical form which makes them unsuitable for convenient use under typical field conditions encountered by campers, military personnel, etc. Furthermore, such compositions are not complete for purifying water and they thus require additional materials and process steps for acceptable clarification and removal of pollutants. In addition, such compositions often require a long processing time which is impractical for certain applications, especially military applications where the need to quickly provide potable water may be critical.

In order for a water purification composition to be suitable for field applications in which water can be clarified and made pollutant free, such a composition should be effective in a small quantity, have a long shelf life and be in a solid dry form for easy packaging and convenient use and operable under a wide range of environmental conditions. More importantly, such a composition should contain all of the effective ingredients in a single composition and such ingredients should be formulated in a manner so that they do not interfere with one another. In addition, the individual ingredients should be quickly dispersible when placed into water so that the composition is quickly activated. It is also very important that the composition can purify and clarify the water quickly.

Prior art compositions have never contained all of the essential ingredients in a single composition for water purification because of certain obstacles associated with making such a combination of ingredients. In particular, it has never been possible to combine all of the essential ingredients in a single composition because the individual ingredients tend to interfere with one another when blended together. Also, from a theoretical point of view, the chemical characteristics of the individual ingredients suggests that such a combination would not be possible if you expect each ingredient to function without interfering with each other in purifying the water.

Currently nothing exists on the market for manual purification except for I.sub.2 tablets which are only effective as a biocide. These tablets do not clarify or sorb metals or organics unless filters or other mechanical devices are employed. Even then broad range pollutant removal is incomplete.

U.S. Pat. No. 2,345,827 (Olin) teaches clarification of water using bentonite clay. The clay must first be formed into a slurry with water and then the slurry is added to the water to be purified. When forming the slurry, care must be taken to avoid ionizing substances or coagulants. Thus, Olin teaches against incorporating a coagulant into the slurry. Small amounts of ionizing substances or coagulants are tolerated for forming the slurry, but the amount is limited to an amount normally found in water. In rare instances, where insufficient ionizable substances are found in water being purified, then these substances may be added to the water being purified, either before or after addition of bentonite slurry to the water. However, the coagulants or ionizing substances must not be added to the bentonite slurry before it is added to the water. Thus, Olin goes to great lengths to avoid combining a coagulant with the clay in a single composition which is to be added to the water. Thus, Olin fails to provide a complete composition for purifying the water. Furthermore, Olin's slurry is inconvenient to use in the field.

U.S. Pat. No. 3,524,811 (Tsuk) discloses the use of certain polymeric flocculants to promote settling of solids suspended in water. Tsuk emphasizes that when two treating agents are combined, they are formulated into an acid solution having a pH below 3. Such a harsh pH would be expected to interfere with zeolites which require a pH of 6-11. Thus, Tsuk's composition effectively precludes the use of zeolites therein. Furthermore, Tsuk does not provide a convenient dry formulation which could quickly remove all of the pollutants from water.

It has been noted by Bacon in U.S. Pat. No. 3,350,304 that bentonite, especially expandable or swellable bentonite should be avoided in a coagulant composition which is used for flocculating finely divided solids in water. Bacon observes that bentonites are associated with an undesirable carry-over of colloidal material into the filter bed.

Bentonite clay has been combined with polymeric flocculants in the composition described in U.S. Pat. Nos. 3,388,060 (Clark); 3,338,828 (Clark); 3,130,167 (Green); 4,415,467 (Piepho); 4,332,693 (Piepho); and 4,765,908 (Monick). However, none of these compositions have overcome the problems associated with a complete combination of essential water purification ingredients and thus these compositions fail to provide a single formulation having the characteristics described above which are necessary for personal water purification in the field. In particular, none of these patents use attapulgite clay and zeolite to clarify and remove pollutants from water in a single composition. Furthermore, none of these patents include a biocide which is compatible with the other ingredients.

Attapulgite clay is known for use in water purification procedures. For example, U.S. Pat. No. 4,116,828 (Sawyer) discloses a water purification method which uses attapulgite clay and sepiolite. However, the clay does not result in clarification and, in fact, it contributes to turbidity. Consequently, cumbersome sedimentation and/or filtration techniques must be employed to remove the clay or sepiolite from the water.

Attapulgite clay is used in a coagulating agent described by Cocks in U.S. Pat. No. 3,342,742. Cocks uses the attapulgite clay and a nucleating agent which is impregnated in an alkali metal aluminate coagulant. Thus, the clay, being impregnated in the coagulant, cannot be freely dispersed in the water for effective removal of contaminants.

Zeolites have been described for use in water purification in U.S. Pat. Nos. 1,793,670 (Borrowman) and 2,004,257 (Tschirner). However, neither of these patents suggest how the zeolite can be combined with other essential ingredients to form a complete water purification composition wherein the numerous ingredients do not interfere with each other.

U.S. Pat. Nos. 3,860,526 (Corbett); 4,450,092 (Huang); 4,610,801 (Matthews); and 4,746,457 (Hassick) describe various types of materials which are suitable for treating water. An article published in Chemical & Engineering News entitled "Water Treatment Chemicals: Tighter Controls Drive Demand"; Mar. 26, 1990, use an overview of chemical technology involved in water purification. However, these references also fail to disclose a single convenient composition having all the necessary ingredients for making polluted water suitable for drinking and which can be quickly used in the field.

It is also known to use a biocide in water treating compositions to kill germs. However, bentonite and attapulgite clay contain water of hydration which is known to interact with biocidal materials such as chlorine dioxide. For example, a well known biocidal material is available which contains chlorine dioxide stabilized on diatomaceous earth. This biocide would ordinarily be considered to be an excellent biocide for use in drinking water because no toxic by-products exist after hydrolysis in water. However, even though bentonite is capable of removing diatomaceous earth, contact with the bentonite liberates chlorine dioxide even in dry formulations. The liberated chlorine dioxide would degrade organic flocculants and coagulants. Furthermore, the biocide will be spent prior to use thus giving the composition a short shelf life. For these reasons, effective compatible biocides have not been formulated with a single complete water treating composition which has a long shelf life which does not produce products which are toxic to humans.

Chlorine and iodine releasing biocides are also avoided in complete water treating formulations because chlorine and iodine ions readily react with a wide variety of organic compounds. Thus, these ions are avoided in compositions containing polymeric flocculants since the latter would be expected to become inactive in the presence of chlorine or iodine ions.

Clays also present certain problems with respect to compatibility with other ingredients. For example, bentonite clay and attapulgite clay are known to have exchangeable cations (Mg, Ca and NH.sub.4.sup.30) in their lattice structure. These ions would be expected to interfere with the proper functioning of zeolite, if zeolite is added to remove toxic metals and the like from the water. Also, since bentonite and attapulgite clays both develop negative charges, it would be expected that the bentonite would not function to remove the attapulgite clay from the solution because of expected repulsive forces between the two like-charged materials. Furthermore, attapulgite clay is known to be a powerful sorbant of polar organic materials due to its fine particle size and porosity. Thus, it would be expected that attapulgite would effectively sorb organic polymers such as organic flocculants and coagulants and thereby render them inactive. Thus, one would avoid combining attapulgite clay with polymeric flocculants and coagulants, especially adsorbed on a dry formula.

Typically, polymeric flocculants and coagulants require predissolving them in water or at least further dilution before adding them to the water. The predissolution is required to fully hydrate or expand the polymer molecule before it is added to the system to which flocculation or coagulation is desired. Mixing is required to accomplish the desired predissolution and when mixing solid polymers, 30-60 minutes or more is recommended. Thus, use of these polymers in solid dry form would not be expected to be useful for effective water purification, especially purification which can be quickly accomplished.

It is also known that bentonite clay in dry form should not be added to the water all at once since doing so results in the formation of a gelatinous blob which can only be broken up by vigorous stirring. Thus, it would not be expected that a complete water purification composition could be formulated with bentonite having all of the bentonite contained in the composition so that it does not have to be added to the water in more than one dose.

In view of the above, a long felt need remains in the art for providing a single dry formulation composition which can remove pollutants and turbidity and disinfect the water to make it safer for drinking.

It is an object of this invention to provide a composition which contains the effectiveness of numerous water treating materials in a single dry mixture without the individual components interfering with each other.

It is a further object to provide a method of treating water to make it safer for drinking by means of a single dry composition which is added to the water being treated.

It is a further object to provide visually clean water in a short period of time which also inactivates germs and reduces the level of metal and organic contaminants.

It is a further object to provide a composition having rapid coagulation and settling times for quick treatment by means of the simultaneous or one step addition of the composition to the water.

It is a further object to provide a formulation for treating water which does not require complicated equipment or operator skill for effective water purification.

It is a further object to provide a water purification composition having a broad range of ingredients which are compatible with each other and which cooperate with each other in a synergistic manner for enhanced purification.

It is a further object to provide a water treating composition in the form of a tablet having all of the ingredients contained therein for quick and easy reduction of turbidity, metal and organic contaminants and harmful germs.

It is a further object to provide a water treating composition with ingredients which are approved for use in potable water.

It is a further object to provide a formula capable of functioning in a broad range of temperatures which could be encountered from tropical to polar climates.

It is a further object to provide a composition and method for treating water wherein turbidity, metal and organic contaminants and harmful germs or bacteria are removed by being quickly settled out of solution without the necessity of a separate filtration step.

These and other objects are met by providing a dry composition containing bentonite, zeolite and polymeric flocculant and/or coagulant. The bentonite may be either swelling bentonite (sometimes called western bentonite) or acid activated bentonite. If swelling or western bentonite is used, then the composition should additionally contain attapulgite clay. However, attapulgite clay may also be added to compositions containing acid activated bentonite or acid activated bentonite may be added to compositions containing swelling bentonite. When attapulgite clay is used in a composition containing polymeric flocculant (without any polymeric coagulant being present) then it is desirable to observe a ratio of bentonite to attapulgite wherein sufficient bentonite is contained in the composition so that a minimum ratio of bentonite to attapulgite is about 1.5:1. In those instances there is no upper limit to the amount of bentonite (i.e. higher ratios may be tolerated) which the composition may contain relative to the amount of attapulgite clay. Ratios of about 2-3 are preferred. Of course, extremely large amounts of bentonite would be undesirable since this could lead to the formation of a large amount of settled floc which would essentially take up an undesirable large amount of water and thereby leave little water available for drinking.

The above mentioned ingredients are blended together to form a dry composition which is used in the form of a powder or tablet. The coagulant, flocculant and bentonite clay (particularly the western or swelling bentonite) form flocs in the water which aid in the removal of turbidity. The attapulgite and zeolite function as adsorbents for removing contaminants such as metal and organic pollutants from the water. It has been discovered that all of these ingredients can be combined without each ingredient interfering with each other when the composition is formulated as a dry composition. It has also been discovered that the dry composition has enhanced dispersibility which is not observed in the individual ingredients.

It will be readily appreciated by those skilled in the art that various sources of water will have differing amounts of turbidity and pollutants contained therein. Thus, the relative amount of each ingredient used in the present composition can vary considerably, given the wide variation of pollutants and turbidity causing materials contained in many sources of water. Thus, the benefits of the present invention can be achieved by using the individual ingredients in effective amounts to remove the turbidity and pollutants or contaminants in the water being treated. Also, with respect to turbidity, it should be observed that some of the ingredients which may be included in the present invention, will actually contribute to the turbidity. Thus, the turbidity removing ingredients should be added in effective amounts to not only remove the naturally occuring turbidity in the water, but to also remove the turbidity causing ingredients (such as attapulgite clay) which may be included in the composition.

The adsorbants, such as zeolite and attapulgite clay, are used in the form of a fine powder to provide a large surface area for quick adsorption. As stated above, this actually contributes to the undesirable turbidity. However, it has been discovered that it is not necessary to use larger particles of adsorbent to avoid this turbidity if the coagulants and/or flocculants are selected so that they can remove the fine particles of adsorbent suspended in the water. Thus, fine particles of adsorbents can be used which remain in suspension for enhanced adsorption during the purification process but which are then removed along with contaminants or pollutants entrained therein as the coagulants and flocculants cause the suspended particles to form aggregates or flocs which quickly settle out of solution. Consequently, particle sizes of the adsorbents are used which form a suspension in the water and which can then be removed with the flocs.

It will generally be desired to include a biocide in the composition. However, the biocide, like all the ingredients used in the invention, must be in a dry form in the final composition. Certain biocides such as chlorine dioxide are to be avoided since they interfere with the polymeric materials contained in the composition and require very low pH for effectiveness.

Optional ingredients include silica gel, acidulant, buffer, sodium bicarbonate, binder, flavorant, colorant, CaO, Ca(OH).sub.2, alumina, kaolin (kaolinitic clays or kaolinite), fullers earth, alum, sericitic clays, semetic clays, sodium phosphate (NaH.sub.2 PO.sub.4), KH.sub.2 PO.sub.4, natural ion exchange clays, montmorillonite, bleaching clays or earth activated charcoal, and diatomaceous earth.

The composition may be formulated into a tablet by conventional techniques. Suitable binders which are well known for making pharmaceutical tablets or pills can be used for this purpose.

It is desirable to include a small amount of acidulent to the composition so that the pH of the treated water is brought into the optimum range required by the biocide. When the composition is in the form of a tablet or the like, an effective amount of sodium bicarbonate is desirably added to create a "fizz" or bubbling action which functions as an aid in tablet dissolution in water particularly when the composition contains an acidulent. However excessive bicarbonate should be avoided which could neutralize the acidity produced by the acidulant. This is especially important if alkaline water is being treated which would consume some acidity from the acidulant.

The composition of the present invention is used by dispersing the powder or tablet into the water and gently agitating it for a brief period of time whereupon the adsorbents are released into the water and are then eliminated along with the other turbidity causing materials as flocs begin to form. Care should be taken to avoid vigorous agitation or stirring so that the developing flocs do not break up. The flocs trap the turbidity causing materials along with the added adsorbents which, by the time the flocs form, have already trapped metals and organic pollutants therein. Additionally, when a biocide is present, it is released into the water to inactivate the germs before the flocs form in the water.

The purification action of this invention is obtained by the use of the several ingredients which cooperate with each other for enhanced water treatment and purification. The composition works by dispersing a variety of active materials into the water which rapidly adsorb the various impurities. Then, by a process of selfflocculation or coagulation, all of the impurities are gathered into a heavy floc which rapidly settles out, leaving clean, clear water. Only milligrams of the formula are required for treatment of the water.

Once the floc has settled out of the solution, the remaining water may be collected by decantation without any filtration step being absolutely essential. However, it may be desirable to use a coarse filter to remove the flocs from the water since this could result in the availability of more water for drinking which would not be the case if the water was simply decanted. When using a filter, it is not necessary to use a fine filter such as would be necessary if the turbidity causing materials were not trapped in the large flocs. Thus, a coarse filter such as cheese cloth, which is fine enough to trap the flocs but which is not fine enough to trap the suspended particles before flocculation, can be effectively used.

The composition of the present invention is a complete formulation, preferably in the form of a single tablet, which effectively removes particulates (turbidity), metals (lead, zinc, cadmium and others), organic contaminants such as solvents, and herbicides and pesticides, in a single convenient operation which does not require expensive equipment or skilled operators. Furthermore, the ingredients are compatible with each other and result in enhanced distribution in the water for quick and easy purification. Also, unlike other compositions, the present invention provides a composition containing a variety of adsorbents, flocculants and biocides which cooperate simultaneously with each other and thus, no follow-up or sequential steps are required for complete purification and clarification.

The present invention also uses attapulgite clay in combination with other ingredients in a manner which has never before been possible. Unlike prior art compositions, the complete formulation is usable as a dry formulation without any pre-mixing being required and thus has the added benefit of having a long shelf-life.

The present invention also produces unexpected large flocs when bentonite and attapulgite clay are combined with polymeric flocculant and/or coagulant. For example, it is not possible to form an acceptable large floc when using attapulgite clay with polymeric coagulant and/or flocculant when bentonite is not also present. Large floc is needed to promote rapid settling, filtration etc. If a filter is too fine, unacceptably long filtrations will be required. Likewise, suitable flocs will not form when zeolite is combined with polymeric flocculant in the absence of bentonite. It is surprising that the bentonite and attapulgite clay can not cooperate in this manner since they both develop negative charges. As a result of these negative charges on the both the bentonite and attapulgite, it is surprising that bentonite can cooperate with the attapulgite to form suitable flocs which additionally removes the attapulgite.

The composition of the present invention is formed by blending the dry ingredients in the form of a powder. Very fine powders of the adsorbants are preferred to further increases the dispersion in water and to provide high surface area and rapid sorption of impurities so that the formulas work well within a few minutes. Preferably the polymeric ingredients (polymeric flocculant and coagulant) can be sorbed on the attapulgite clay, then dried and ground to a fine powder prior to the actual blending. It has been discovered that when polymers are sorbed on the attapulgite clay in this manner, sufficient polymer will desorb and be available for flocculation of the remainder of the formulation.

It has been observed that zeolite powder will not blend easily with bentonite and attapulgite clay even though the latter two materials will blend with each other. If these three materials are to be properly mixed with each other to form a uniform, homogeneous powder, some method must be employed which will break up the loose clumps of zeolite and cause it to be dispersed in the clays; otherwise pockets of zeolite remain and are visually apparent in the formula. Any mechanical method may be used. However, this is preferably accomplished in a tumbling operation which uses ceramic pellets to aid in the break up and mixing.

It is important that the biocide not be incorporated during the tumbling or grinding step since this would result in further reduction of the particle size of the biocide in the final formula. Reduction in the particle size of the biocide results in an increase in surface area that becomes available for reaction with the water of hydration in the clays. This may result in liberation of halogen which will react with the polymeric ingredients and thereby inactivate them. Thus the shelf life will be shortened. Likewise, acidulents should also not be added until after the grinding step since a decrease in the particle size of the acidulent would allow it to hydroscopically draw more moisture from the air during processing, with a subsequent reduction in storage or shelf life of the product.

Swelling bentonite is preferred over acid-activated bentonite for the clarification of water and for removing other ingredients from the composition after they have performed their respective functions in the water. However, when it is desired to remove organic contaminants it is preferable to use acid-activated bentonite. The attapulgite clay augments the formulas which use the swelling bentonite for organic removal. It has been discovered that swelling bentonite helps remove acid activated bentonite from the water and thus is useful when combined with compositions containing acid activated bentonite. Also, with respect to the acid activated bentonite, it has been observed that it has very low ion exchange capacity in comparison to zeolite. In particular, it has been observed that zeolite has almost 100 times more ion exchange capacity than acid activated clay.

Both acid activated and swelling bentonite (also called sodium bentonite, Wyoming bentonite or Western bentonite) are well known materials which are commercially available. Acid activation of bentonite is a well known procedure wherein the bentonite is treated with mineral acid to yield a modified clay of high surface area and acidity that exhibits enhanced adsorptive and catalytic properties. Both swelling bentonite and acid activated bentonite are described in an article entitled "Acid Activated Clays" published by the Society of Mining Engineers of AIME; Transactions, volume 282, pages 1901-1909; which is herein by reference.

Different types of bentonite may be combined if desired to achieve the select adsorption of a variety of pollutants. The bentonite, as well as other ingredients used in the composition, should be free from harmful or toxic ingredients which could enter the water being purified.

Both natural and synthetic zeolites are useful in this invention. Useful zeolites include mordenite powder (sodium form and hydrogen form). The ammonium of mordenite powder is not preferred.

The sodium form of mordenite powder is available from PQ Corporation which is sold under the trademark "VALFOR" C 500-11 zeolite. The C 500-11 zeolite has the following properties:

The hydrogen form of mordenite powder is available from PQ corporation which is sold under the trademark "VALFOR" C 505-20 zeolite. The C 505-20 zeolite has the following properties:

A number of suitable zeolites are sold under the trademark "ZEOLON" which are sold by the Norton Company. Suitable zeolites in the "ZEOLON" series include "ZEOLON 400", "ZEOLON 500", "ZEOLON 700", "ZEOLON 900 Na" and "ZEOLON 900 H". The physical characteristics and chemical analysis of the above mentioned "ZEOLON" zeolites are shown below in Tables 1 and 2:

Another suitable zeolite is synthetic type A zeolite in the sodium form. Such a zeolite is available from PQ corporation sold under the trademark "VALFOR" G 100. The "VALFOR" G 100 has the following properties:

It has also been discovered that zeolites can be useful for removing radionucleides from water. The above mentioned "VALFOR" G100 in the alkaline earth series or the "VALFOR" C500-11 or "VALFOR" C505-20 are preferred for this purpose.

The attapulgite clay should have low solubility in water and should resist degradation since excessive cloudiness can occur in the water if the attapulgite breaks down. Pharmaceutical or cosmetic grades of attapulgite are suitable. A suitable attapulgite clay is available from Englehard Minerals which is sold under the trademark "PHARMASORB". "PHARMASORB" is sold in both colloidal and regular form. The regular form is preferred. The regular "PHARMASORB" has the properties shown below in Table 3.

Another suitable attapulgite clay is Floridin attapulgite (Florida-Georgia fuller's earth). As noted above, the attapulgite should resist water breakdown. LVM (low volatile matter) grades of attapulgite are known to resist disintegration in water. A suitable LVM attapulgite is available from Floridin Corporation under the trademark "FLOREX" LVM attapulgite. The chemical analysis and physical properties of "FLOREX" LVM attapulgite is shown below in Tables 4 and 5:

Conventional polymeric flocculants and polymeric coagulants which are known for use in treating water may be used in this invention. The coagulants are generally low molecular weight, high charge polymers whereas the flocculants are high molecular weight, low charge polymers. The coagulants are better at charge neutralization of the clays than the flocculants but the flocculants are better for building larger and heavier flocs which settle rapidly. The coagulant and flocculent are added in amount to neutralize the charge of the bentonite and attapulgite clay. Amounts of coagulant and flocculent in excess of the amount needed for charge neutralization are not necessary and should be avoided since an excess will cause a dispersal effect.

Neutralization need not be absolutely precise since it is only necessary that the charge on the clay be sufficiently neutralized to form flocs containing the clay and polymeric coagulant or polymeric flocculent. The amount of polymer needed will depend upon the amount of clay in the composition and the charge neutralization capacity of the polymer being utilized. For example, the charge neutralization capacity of "CLARIFLOC" C 358 P is 6.31 milliequivalents per gram whereas the charge neutralization capacity for "CLARIFLOC" C 319 P is higher at 7.37 milliequivalents per gram. Thus the amount of C 358 P necessary to produce the equivalent charge neutralization achieved with C 319 P can be readily calculated.

Cationic polymers are used to neutralize the charge when the composition contains swelling bentonite whereas anionic polymers are used with compositions containing acid activated bentonite. Neutral polymer coagulants and flocculants may be used where no further neutralization is needed.

Coagulants are preferred over flocculants especially because the chemical structure of the coagulants are more stable against degradation caused by halogen biocides which may be included in the composition. Also coagulants are preferred because of their higher charge neutralization capacity over flocculants. In both coagulants and flocculants, higher molecular weight polymers are preferred over lower molecular weight polymers.

Suitable polymeric flocculants include polyacrylamide polymers or copolymers thereof having acrylic acid or acrylate co-monomers. Suitable polymeric coagulants include quaternary condensation polymers of epichlorohydrin and dimethyl amine; quaternary ammonium compounds of vinyl polymers; amine polycondensates and polydiallyl dimethyl ammonium chloride. Other useful polymer coagulants and flocculants are described in U.S. Pat. No. 4,415,467, the specification of which is incorporated herein by reference.

Preferably the coagulants and flocculants should be chosen so as not to impart any objectionable taste to the water. Ideally, the coagulant and flocculant should be one which functions in a wide temperature range which approaches the freezing point of water. Also, when using acid activated bentonite it is prefered to use an anionic polymer and when using swelling bentonite, it is preferred to use a cationic polymer.

A preferred coagulant is polydiallyldimethyl ammonium chloride which has the formula [CH.sub.2 CHCH.sub.2)N(CH.sub.3).sub.2 Cl].sub.x. The value for X is not critical. However, it is preferred that X be chosen so that the polymer has a molecular weight of about several thousand. A suitable polydiallyldimethyl ammonium chloride polymer has a CAS number which is CAS 26062-79-3 (polymer). One such polymer is commercially available in the form of an aqueous solution from Polypure Inc. under the trademark "CLARIFLOC" C-308 P polymer. The C-308 P is a light amber color liquid which is completely soluble in water. It has a boiling point of 100.degree. C., a melting of 0.degree. C., a specific gravity of 1.03-1.05 and a pH of 5-7.

Another polydiallyldimethyl ammonium chloride coagulant is available from Polypure Inc. under the trademark "CLARIFLOC" polymer C-358 P. The C-358 P polymer is sold as an aqueous solution. It has the same formula as the "CLARIFLOC" C-308 P but has a higher molecular weight. The C-358 P polymer has a CAS number which is CAS 26062-79-3 (polymer). The C-358 P is a light amber clear viscous liquid having a cationic ionic nature. It has a density of 8.7 lbs/gal; a pH of 5-7, a flashpoint greater than 100.degree. C., a freezing point of -15.degree. C., a boiling point of approximately 100.degree. C., a melting point of approximately 0.degree. C., a specific gravity of 1.03-1.05 and is completely soluble in water.

Another preferred coagulant is a quaternary condensation polymer of epichlorohydrin and dimethylamine which has the formula [(CH.sub.2 CHOHCH.sub.2)N(CH.sub.3).sub.2 Cl].sub.x. The value for X is not critical but it is preferred that X be chosen so that the polymer has a molecular weight of about several thousand. A suitable polymer having the above formula has a CAS number which is CAS 42751-79-1(polymer). Such a polymer is commercially available from Polypure Inc. under the trademark "CLARIFLOC" C-319 P polymer. The C-319 P polymer is sold as an aqueous solution. The C-319 P polymer is a clear amber-red liquid which is highly cationic. It has a density of 9.42 lbs/gal, a pH of 6, a viscosity of 4,500-7,500 cps, a freezing point of -9.degree. C., a boiling point of 100.degree. C., a melting point of 0.degree. C., a specific gravity of 1.13 and is completely soluble in water.

Another suitable polymeric coagulant is a highly charged cationic liquid polymer (quaternary ammonium compound vinyl polymer) available from Ashland Chemical Company (Drew Industrial Division) a division of Ashland Oil Inc. under the trademark "AMERFLOC" 482. The "AMERFLOC" 482 is a clear to pale yellow liquid which has a specific gravity of 1.04 (at 25.degree. C.), a viscosity of 120 cps (at 25.degree. C.), a pH of 6 and a freezing point of -6.degree. C.

In the polypure "CLARIFLOC" polymer series, the C-358 P is the most preferred coagulant. No maximum molecular weight is specifically required for the coagulants or flocculants used in this invention.

Any activated carbon can be used which is in the form of a fine powder. A suitable activated carbon is available from ICI Americas Inc. which is sold under the trademark "HYDRODARCO" B. The "HYDRODARCO" B has the following properties which are shown below in Table 6:

A suitable silica gel is available from Amicon Corp. (a division of WR Grace and Co.) which is sold under the trademark "MATREX" Silica. The "MATREX" Silica is available in nominal pore sizes of 60 .ANG. and 100 .ANG. with 60 .ANG. being preferred. The physical characteristics of the 60 .ANG. and 100 .ANG. "MATREX" silicas are shown below in Table 7:

Suitable biocides include tetraglycine hydroperiodide and sodium dichloroisocyanurate. Suitable buffer includes disodium pyrophosphate. Preferably the buffer is added in an amount to buffer the pH of the water at about a pH of 6.

The composition is made by blending the ingredients in the form of a powder to form a homogeneous mixture. Therefore, starting materials such as the coagulants which are in the form of a liquid, are preferably adsorbed on a solid ingredient and allowed to dry before blending into a final product. For example, the polymeric coagulants or flocculants which may initially be in the form of an aqueous solution, may first be sorbed on the attapulgite clay. The clay containing the coagulant or flocculant is then dried using an air dryer, vacuum oven or other suitable drying device. The dried clay containing the sorbed coagulant or flocculant is then ground to a powder using a ball mill or similar technique.

The grinding may be accomplished in a conventional tumbler device with the use of ceramic balls or pellets. The use of ceramic pellets during the tumbling operation helps blend and break up any loose clumps of zeolite to aid in the formation of a homogenous blend with the bentonite and attapulgite clay and other ingredients. However, if a biocide is to be added, it should be added after the tumbling or grinding step with the ceramic pellets removed. Likewise, acidulant should not be added until after the tumbling or grinding step with the ceramic pellets removed.

Tablets or the like may be formed by conventional tableting procedures. Preferably a binder such as microcrystalline cellulose or carboxy methyl cellulose is added to form the tablets. Other conventional binders for forming pharmaceutical tablets can be used.

It has been observed that coagulants hydrate more rapidly than solid flocculants. Using this difference in hydration rate, it is possible to add both types of polymers (coagulant and flocculant) to obtain an advantage in building the floc. More particularly, the cationic coagulant can rapidly hydrate and neutralize the charge on the clays. When complete, a non-ionic flocculant can take over and pull all of the smaller floc together to obtain a large floc than might ordinarily be

It has also been observed that pretreating the bentonite, attapulgite and/or zeolite with a strong solution of biocide helps kill microorganisms that become lodged in the lamella of bentonite or the pore structure of the attapulgite or within the zeolite during its actual use in water treatment. The biocide is pre-adsorbed on the bentonite so that the pores become filled with the biocide before the bacteria or other germs have a chance to become lodged in the pores and thereby become protected from the biocide released in the water. The bentonite does not necessarily have bacteria or other germs in it before being added to the water. The pretreatment step is desirable since the bacteria or other germs may not all be killed during the clarification procedure due to the fact that they become hidden within the structure of the above mentioned solid materials. One would not ordinarily think that this type of sorbtion could occur since it is not the typical material bentonites adsorb in their structure.

The pretreatment involves preparation of a strong solution of biocide and soaking the bentonite, attapulgite and/or zeolite for a few minutes in the solution. The excess liquid is filtered off and the treated material is dried. After drying, the pretreated material may then be blended into the product. Additional biocide may or may not be required in the final formula.

In a first embodiment, Western bentonite is mixed with attapulgite clay, zeolite, activated charcoal, tetraglycine hydroperiodide (TGHPI) and polymeric flocculant. The amount of each ingredient combined with bentonite is given below in Table 8 with the amount of each ingredient being expressed in term of weight % relative to the amount of bentonite.

An example of the first embodiment contains 201 mg. Western bentonite, 77.5 mg attapulgite clay, 201 mg zeolite (synthetic Type A--sodium form), 2.1 mg TGHPI, 1.0 mg polyacrylamide polymer flocculant. The formulation of Example 1 is in the form of a powder. The powder of Example 1 may be formed into a tablet by using about 50 mg of microcrystalline cellulose binder to make a formulation which is 610.1 mg/tablet.

In a second embodiment, acid activated bentonite is combined with attapulgite clay, zeolite, sodium phosphate, sodium bicarbonate, sodium dichloroisocyanurate, polymeric flocculant (polyacrylamide/acrylate copolymer) and binder. The amount of each ingredient mixed with the bentonite is given below in Table 9 with the amount of each ingredient being expressed in terms of weight % relative to the amount of bentonite.

An example of the second embodiment is a tablet containing 252 mg acid activated clay, 150 mg attapulgite clay, 170 mg zeolite (synthetic type A-sodium form), 5.0 mg sodium phosphate, 10 mg sodium bicarbonate, 15 mg sodium dichloroisocyanurate, 1 mg polyacrylamide/acrylate flocculant, 50 mg microcrystalline cellulose. Each tablet weighs 653 mg.

In a third embodiment acid activated bentonite is combined with silica gel, sodium dichloroisocyanurate, sodium bicarbonate polymer flocculant and binder. The amount of each ingredient mixed with the bentonite is given below in Table 10 with the amount of each ingredient being expressed in terms of weight % relative to the amount of bentonite.

An example of the third embodiment is a tablet containing 365 mg acid activated bentonite, 180 mg silica gel, 15 mg sodium dichloroisocyanurate, 50 mg sodium bicarbonate, 1 mg polyacrylamide/acrylate flocculant and 50 mg. sodium carboxymethylcellulose. Example 3 is in the form of a tablet weighing 661 mg/tablet.

In a fourth embodiment, acid activated bentonite is combined with zeolite, silica gel, disodium pyrophosphate, sodium dichloroisocyanurate, polymer flocculent and sodium bicarbonate. The amount of each ingredient combined with the bentonite is given below in Table 11 with the amount of each ingredient being expressed in terms of weight percent relative to the amount of bentonite.

An example of the fourth embodiment contains 399 mg acid activated bentonite, 160 mg zeolite (synthetic Type A--sodium form), 100 mg silica gel, 100 mg disodium pyrophosphate, 15 mg sodium dichloroisocyanurate, 1 mg polyacrylamide/acrylate copolymer flocculant, and 50 mg sodium bicarbonate. The powder of Example 4 is formed into a tablet by using 50 mg of sodium carboxymethylcellulose binder to make a tablet which is 875 mg/tablet.

In a fifth embodiment swelling bentonite is combined with attapulgite clay, zeolite, sodium dichloroisocyanurate, polyacrylamide flocculant, sodium bicarbonate, and disodiumpyrophosphate. The amount of each ingredient mixed with the bentonite is given below in Table 12 with the amount of each ingredient being expressed in terms of weight % relative to the amount of bentonite.

An example of the fifth embodiment of the invention contains 350 mg swelling bentonite, 150 mg attapulgite clay, 150 mg zeolite, 15 mg biocide (TGHPI), 20 mg polyacrylamide flocculant, 100 mg sodium bicarbonate and 100 mg disodium pyrophosphate. The formulation of Example 5 is in the form of a powder. The powder of Example 5 is formed into a tablet by using 50 mg of microcrystalline cellulose binder to form tablets which are 925 mg/tablet.

A preferred embodiment of the invention contains 325 mg swelling bentonite, 150 mg attapulgite clay, ("PHARMASORB" regular), 130 mg zeolite (synthetic type A-sodium form "VALFOR" G100), 12 mg polydiallyldimethyl ammonium chloride ("CLARIFLOC" polymer C-358 P), 15 mg sodium dichloroisocyanurate, 100 mg. sodium bicarbonate, 100 mg sodium pyrophosphate and 50 mg microcrystalline cellulose. The microcrystalline cellulose binder may be omitted if the formulation is not to be formed into a tablet. This preferred embodiment may also include 1.0 mg polyacrylamide or polyacrylamide/acrylate copolymer as a flocculant. The "CLARIFLOC" C-358 P is added in the form of an aqueous solution containing 80 wt. % water and 20 wt. % polymer. 60 Mg of the solution is sorbed on the attapulgite clay and the water is evaporated to result in 12 mg of polymer (dry weight) in the product.

When making the above preferred composition in bulk quantities, the ingredients are used in the following amounts expressed in terms of wt. % relative to the amount of bentonite contained in the composition:

The preferred formulation described above can be used to purify one liter of water by adding one or two tablets to the water (or an equivalent amount of the powder) and agitating the water by swirling or gently shaking it for three minutes. The water is then allowed to settle, which takes about 10 minutes at 25.degree. C. (about 18 minutes at 15.degree. C.-5.degree. C.). After settling, the clarified water may be decanted or passed through a paper or cloth filter. The decanted or filtered water is ready for drinking.

A composition was prepared containing 145 mg swelling bentonite, 72 mg attapulgite clay, 108 mg zeolite (synthetic type A--sodium form) 44 mg activated charcoal ("HYDRODARCO" B), 28 mg TGHPI, 3 mg polyacrylamide flocculant. The material of Example 6 was used to purify water. The results are summarized below in Table 13.

The composition used in Example 6 may be made in bulk quantities by using the following ingredients in the amounts specified in terms of wt. % relative to the amount of bentonite contained in the composition:

A composition was prepared containing 287 mg Western bentonite, 110 mg attapulgite clay, 287 mg zeolite (synthetic type A--sodium form), 110 mg activated charcoal ("HYDRODARCO" B), 3 mg TGHPI, and 0.14 mg polyacrylamide/acrylate copolymer flocculant. Contaminated water was treated with the composition of Example 7 with the results summarized below in Table 14.

429 mg of the composition shown by Example 2 was used to treat water. The results of the treatment are shown below in Table 15.

600 mg of the composition shown in Example 3 was used to treat contaminated water. The results of the treatment are summarized below in Table 16.

600 mg of the formula shown in Example 4 were used to treat contaminated water. The results of the treatment are summarized below in Table 17.

831 mg of the preferred embodiment was used to treat 1 liter of contaminated water. The results are summarized in Table 18 below: