MXPA99001573A - Method for removing toxic substances in water - Google Patents

Abstract

Arsenic and TOC are removed from drinking water or wastewaters by use of a finely-divided metallic iron in the presence of powdered elemental sulfur or other sulfur compounds such as manganese sulfide, followed by an oxidation step. A premix may be produced for this process, by adding the iron, sulfur and oxidizing agent to water in a predetermined pH range. The iron and sulfur are mixed for a period of time dependent upon the temperature and pH of the water and the presence of complexing or sequestering minerals and organic acids in the water. An oxidizing agent is added to the mixture and agitating is continued. In a preferred embodiment the oxidizing agent is hydrogen peroxide. Water is decanted from the mixture after a sufficient reaction time, to produce a concentrated premix. This premix can be added to water intended for drinking or to industrial effluents containing toxic materials.

Description

METHOD FOR REMOVING TOXIC WATER SUBSTANCES BACKGROUND OF THE INVENTION This invention is directed to a method and system that removes various toxic and regulated organic and mineral precursor substances from drinking water or wastewater causing them to be adsorbed and adsorbed onto sulfur-activated sponge iron particles, which may be called " iron modified with sulfur ". Specifically, the method and system removes residual amounts of dissolved (1) arsenic, selenium and lead, colloidal and particulate from the water; (2) organic compounds that occur naturally (TOC, total organic carbon in water), which, when oxidized, form "disinfection byproducts" and (3) other potentially harmful minerals. The subject of this invention is related to some extent with that of the US patents. Nos. 4,940,549 and ,200,082, which are directed to the selenium removal of agricultural drainage water and refinery effluents and other indusrial wastewater. The process of the present invention is particularly related to the removal of arsenic and other toxic metals, and to the decrease of the TOC level of drinking water, using some of the same steps that were effective in the removal of selenium in the patents above. mentioned. Recent scientific research by the United States Environmental Protection Agency (EPA) and others has suggested that arsenic in drinking water causes cancer in humans; that no amount of arsenic in drinking water is a safe quantity; that arsenic might not be an essential human nutrient as previously repossessed by science and that the risk of cancer from ingesting arsenic at the levels currently allowed in drinking water could equal the caused by smoking cigarettes. The? PA currently negotiates the ^ content of the regulations for arsenic in drinking water and project that the new limitation will be between 2 and 5 micrograms per liter (μg / L), most likely 2 μg / L. Many existing water systems will have to treat it 15 to reduce the concentration of arsenic. Here are three examples: (a) The California State Water Project that has naturally occurring arsenic in the amount of 2 to 6 μg / L provides water to several million families; 20 (b) The city of Hanford, California obtains drinking water for more than 20,000 people from underground water wells. Some of the wells have arsenic concentrations of almost the current limit of 50 μg / L; (c) The Kern Water Bank is a project built to store water in underground reservoirs in times of shortage for use when water is not available.

Some of the Water Bank wells have naturally occurring arsenic. In summary, the concentration of arsenic approaches 200 μg / 1. Water providers are in immediate need of an economical and effective method to remove arsenic from drinking water. Current methods, systems and technologies have proven each to be non-economic or ineffective to meet the proposed 2 μg / L standard. The test for economic water service is as follows: is the water cost less than two percent of a family's gross income at the poverty level? Existing technologies for the removal of arsenic include the following: (a) adsorption on activated alumina within a fixed-bed contactor; (b) complex arsenic with anhydrous metal floccules, mainly hydroxides or oxyhydroxides of aluminum and iron, in conventional water treatment plants; (c) sieving the metal of the water by membrane technologies such as reverse osmosis and (d) electrodynamic processes such as electrodialysis. The present invention described below can exhibit a cost advantage of 5 to 15 times compared to these prior methods. Similarly, since the mid-1970s, the EPA has warned that certain classes of byproducts formed by oxidizing organic acids that occur naturally during disinfection are potentially carcinogenic. These compounds they are regulated as "disinfection byproducts" (DBPs) to limit consumption. There are many DBP compounds of interest to the EPA. Not all have been described or fully investigated with respect to their potential effects on human health or the frequency of their occurrence in domestic water systems. In addition, the epidemiological impact of BPDs is uncertain. Therefore, there is a concerted national effort to develop data on the formation of BPDs and to better define their potential impact on human health. The EPA currently requires more water systems to disinfect its water and limit the occurrence of waterborne diseases, while at the same time EPA seeks to reduce the impacts of DBPs on human health; these can be conflicting purposes. Most hydraulic systems disinfect your water. In this way, many water systems will have to initiate or modify water treatment systems to reduce DBPs and meet proposed tri-halogenomethane limitations that may vary from 40 to 60 μg / L. Other DBPs, such as halogenated acids and various bromine compounds, will be subjected to numerous concentration limits. Conventional treatment systems for surface water sources can meet many of the proposed standards if influential precursors, ie TOCs, can be limited to 4 mg / L before disinfection with chlorine.

Thus, throughout the United States, water suppliers are in immediate need of an economic and safe method to reduce the occurrence of DBPs in drinking water. Current methods, systems and technologies have each proven to be inefficient or ineffective in meeting the proposed 40 to 60 μg / L standard. The EPA has proposed strict limitations on the class of DBPs known as trihalogenomethanes, mentioned above, since 1975. Water suppliers have commonly failed to meet the most basic requirement that trihalogenomethanes represent less than 100 μg / L. As mentioned above, the main strategy currently used to reduce DBPs is to control precursor chemicals at the beginning of the water treatment process so that smaller quantities of disinfection byproducts are formed during disinfection. Current alternative strategies include the use of unconventional disinfectants, the treatment of water to reduce the formation of DBPs (in the presence of conventional disinfectants) and the removal of DBPs after training. Existing technologies for reducing the concentration of DBPs include the following: (a) adsorption of DBPs or precursors onto granulated activated carbon within a fixed bed contactor or adsorption onto powdered activated carbon during various stages of the treatment process; (b) complex DBPs or precursors with anhydrous metal flocs, mainly aluminum and iron hydroxides, in conventional water treatment plants after adjusting the pH of the influencing water; (c) sieving the relatively larger organic molecules of water by membrane technologies such as ultrafiltration and (d) electrodynamic processes such as electrodialysis. An important object of the present invention is to remove efficiently and very economically arsenic, TOCs and other contaminating metals from drinking water. The The described procedures can reduce the cost of removing these contaminants by a factor of five to fifteen, particularly in comparison to reverse osmosis or nanofiltration. A further object of the present invention is to provide a method and system for removing arsenic, TOCs and others. polluting metals that can be introduced in existing water treatment facilities. These and other objects of the invention will be apparent to those skilled in the art. in the art from the detailed description of the invention contained herein and from the drawings annexes.

BRIEF DESCRIPTION OF THE INVENTION "The method of the present invention removes residual amounts of certain toxic substances in drinking water, specifically: (1) dissolved, colloidal and particulate arsenic, selenium and lead; (2) organic compounds that occur naturally (total organic carbon or "TOC"), which, when oxidized, form disinfection byproducts and (3) other potentially harmful minerals. The invention uses a solid medium with a finely divided metallic elemental iron of very high surface area or "sponge" iron. The medium is manufactured by forming an oxidized surface in water in the presence of finely divided elemental sulfur or other sulfur-bearing compounds such as manganese sulfide. The solid medium, which can be called "iron modified with sulfur" and is sometimes called that in the present, is made by mixing the ^ constituents in water according to predetermined proportions. In a preferred embodiment of the present According to the invention, these proportions can be about, by weight: 200 parts of iron, 100 parts of sulfur and 1,000 parts of water. The mixture is produced in water at a predetermined pH level, which for a preferred embodiment is on a pH scale between about 5.0 and 8.5. The normal processing temperatures can vary from 1.1 ° C to almost boiling. This combination is mixed during approximately two hours while the active agent is formed. The mixing time depends on the temperature of the mixture, the pH of the water and the presence of complexing or sequestering minerals and organic acids in the water. The lower temperature, higher pH and presence of such complexing minerals will generally require longer mixing time. In a preferred embodiment, an oxidizing agent is added to the mixture after the pH is raised and stabilized, and stirring is continued. In a specific embodiment, the oxidizing agent is hydrogen peroxide. The solid iron modified with sulfur can be removed from the water in which it is manufactured and used to treat water. The treatment can be by means of intermittent or flow-through procedures. The sulfur-modified iron can be removed from the process stream by means of gravity separation processes, centrifugal force or magnetic separation processes. In the intermittent treatment process, the untreated water and the components of iron modified with sulfur or iron modified with preformed sulfur are mixed vigorously for a variable period of time. The duration of mixing can be as short as 5 minutes or as long as 2 hours depending on how complete the sulfur-modified iron is and the physical constants of the water to be treated. The mixing can be supplied by means of air pumps, hydraulic mixing, the action of a fluidized bed, mechanical mixers or by other means. Note that the intermittent treatment procedure may employ a premix of sulfur-modified iron, or that the iron and sulfur may be mixed separately in the untreated water. The parameters such as mixing time will vary depending on the procedure used. In the flow step process, the preferred process, the sulfur-modified iron is pre-prepared and resides in an upflow fluidized bed reactor or other completely mixed reactor vessel for a suitable period of time. The sulfur modified iron remains in the reactor by virtue of its relatively high specific gravity, 2.61 ±, while the untreated water flows further in turbulent mixing. The necessary residence time in the. reactor is approximately 5 minutes, depending on different processing variables. Alternatively, the process can take place in a flint flocculator or contact clarifier apparatus in which the sulfur-modified iron is fixed to the surface of the treatment medium within the container or recirculated within the reaction zone of the process. Another alternative is to introduce the sulfur modified iron in the central well of a rapidly mixed contact clarifier of a water treatment plant or wastewater. It is believed that the ability of the sulfur-modified iron to adsorb and absorb toxic substances from the water will be exhausted after approximately 100,000 pore volumes have been treated, more or less. At that time, it can be restored by removing the toxic substances. It may be that the sulfur-modified iron is restored and reused by washing it with a properly selected basic or acid liquid. The choice of restoration fluid will be governed by the economy of the specific installation in which it is used. The characteristics of the untreated water can allow the recovery of resources from regeneration fluids. The removal, regeneration and replacement can be a continuous or periodic intermittent flow procedure.

DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a reactor according to an embodiment of the present invention for producing the sulfur-modified iron. Fig. 2 is a schematic flow chart of a prior art water treatment process / plant that indicates the vision of a through flow treatment reactor according to the present invention. Figure 3 is a schematic flow diagram of the use of the preparation of the modified iron with sulfur according to an intermittent manufacturing process of the present invention.

DESCRIPTION OF THE PREFERRED MODALITIES As mentioned above, the method of the present invention removes residual amounts of certain toxic substances or precursors of toxic substances in drinking water. This procedure depends on the creation or use of a medium solid with a very high surface area produced from »Finely divided metallic elemental iron called here" the modified iron with sulfur ", as explained above. The medium is generated by forming an oxidized iron surface in the water in the presence of finely divided elemental sulfur or other sulfur-bearing compounds such as manganese sulfide. Consequently, Figure 1 illustrates a method - preferred for the creation of the modified iron with sulfur. A reaction vessel 10 is filled with water at 12. Then, A fluid is introduced at 14 to bring the mixture to a predetermined pH level, which for a preferred embodiment is on a pH scale of between 5.0 and 8.5. In addition, heat can be introduced or recovered by means of the heat exchanger 30 as appropriate to bring the water to a scale of acceptable temperature. Normal processing temperatures vary from 1.1 ° C to almost boiling.

The sulfur-modified iron can be manufactured by premixing the constituents in water according to predetermined proportions, as explained above. First, "sponge iron" is added at 16 and agitated by a mixer 20 for a period of time, for example one hour in a preferred embodiment. Sponge iron with particle sizes of 325 mesh or slightly larger is preferred. Then, sulfur is added in 18 and the mixture is again stirred by the mixer 20 for 45 minutes in the preferred embodiment described above. In addition to elemental sulfur, it is believed that sulfur compounds such as manganese sulfide can be substituted. In a preferred embodiment of the present invention, for preparing a premix of sulfur-modified iron, the proportions of the reactants are approximately, by weight: 200 parts of iron, 100 parts of sulfur and 1,000 parts of water. This combination is mixed while the active agent is formed. The mixing time depends on the temperature of the mixture, the pH of the water and the presence of minerals and organic acids complexing or sequestering in the water, as mentioned above. Then, in the preferred embodiment described, an oxidant can be added at 22 after the pH of the suspension containing sulfur, iron and water is stabilized. In the preferred embodiment described above, a part of hydrogen peroxide is introduced and the mixture is stirred by the mixer. for about 15 minutes. Finally, the resulting modified solid sulfur iron can be removed in large part from the water in which it is manufactured, and can be used to treat the water. The preferred use of the sulfur-modified iron is in a step flow process in the water treatment system as described above. In this step flow process, the sulfur-modified iron is pre-prepared and is in a flow reactor rising or another reactor vessel completely mixed. As described above, in this system the sulfur modified iron is retained in the reactor by gravity while at the same time the completely mixed contact takes place as the water flows upwards. The resulting mixture of toxic substances and sulfur-modified iron is removed and removed from the water cleaned by gravity, centrifugal force or magnetic separation. The modified iron with sulfur can be recirculated by regeneration using an appropriate basic or acidic rinse solution. Said reactor can be introduced into an existing water treatment plant as shown in figure 2. First, a valve 122 is inserted between the chemical feed vault 120 and the influential pumps 140. New pipes 124 and 126 are introduced for transport the water inside and outside of, respectively, the new reactor 130. The sulfur-modified iron can be introduced from the feed inlet 132 and be removed by outlet 134. Sulfur-modified iron will normally remain in reactor 130 by virtue of its relatively high specific gravity, 2.61 ±, while untreated water flows further in turbulent mixing. The residence time required in the reactor 130 is approximately 5 minutes, depending on different processing variables. Alternatively, the process can take place in a flint flocculator or contact clarifier apparatus in which the sulfur-modified iron is fixed to the surface of the treatment medium within the container or recirculated within the reaction zone of the process. Another alternative is to introduce the sulfur-modified iron into the central well of a rapidly mixed contact clarifier from a wastewater or wastewater treatment plant. The ability of the sulfur-modified iron to adsorb and absorb toxic substances from the water will be exhausted after a number of pore volumes have been treated (believed to be approximately 100,000). At that time, as described above, it can be restored by removing toxic substances. It is believed that sulfur-modified iron can be restored and reused by washing it with selected acidic or basic liquids, such as caustic soda, to remove organic compounds from the surface of the iron. The choice of restoration fluid will be governed by the economy of the specific installation in which it is used. The characteristics of the untreated water can allow the recovery of resources from regeneration fluids. The removal, regeneration and replacement may be a continuous or periodic intermittent flow procedure. Figure 3 illustrates an alternative method for producing the sulfur-modified iron and for treating the influencing water in the same process. In this intermittent treatment procedure, the untreated water and the iron and sulfur or iron modified with sulfur are mixed • vigorously for a variable period of time. The duration of mixing can be as short as 5 minutes or as long as two hours depending on how complete the formation of the sulfur-modified iron and of the physical constants of the water that will be treated, including temperature and pH. Mixing can be provided by means of air pumps, hydraulic mixers or by other ^ means. First, untreated water enters the reactor passing first by a conventional filter, shown at 208. Water enters and is stored in a surge tank at 212, and a fluid is introduced at 214 to bring the mixture to a predetermined pH level, which for the preferred embodiment It is on a pH scale between about 3.5 and 8.5. A scale of Acidic pH generally causes the process to work more efficiently. However, considerations economic indicators indicate that acidification should be avoided if practicable. Drinking water is usually on a pH scale of 7.5 to 9.5 (to avoid corrosion of pipes). An efficient pH scale is from 5.0 to 8.5, but a slightly higher pH may be acceptable, depending on the water content. In addition, heat can be introduced into the water as appropriate to bring the water to an acceptable scale. Normal processing temperatures can vary from 1.1 ° C to almost boiling, but temperatures above the room temperature tend to produce a reaction time " faster. Of course, it is more economical not to heat the water if this can be avoided within practical time constraints. Then, in a first step 218, iron is added sponge in 222 and stirred by a mixer. You can use sponge iron or iron modified with partially pre-assembled sulfur. Then, if only iron has been added, it is added ^ Sulfur in 220 and the mixture is stirred again for an additional period of time. As mentioned above, it is believed that sulfur compounds such as manganese sulfide can be substituted. Next, an oxidant at 224 is added to the mixture in the second step 226, after the pH of the suspension containing sulfur, iron and water is stabilized. From Once again, in the preferred embodiment described above, a part of hydrogen peroxide is introduced (relative to 200 parts of iron and 100 parts of sulfur by weight) and the mixture is stirred. Finally, the iron modified with solid and reacted sulfur can be removed from the water by magnetic separation, gravity or centrifugal force, as indicated in 228. The treated water 234 can then be subjected to an additional treatment as conventional. In addition to the form described above, the sulfur-modified iron can be fixed to a solid substrate material such as silica, alumina, ceramics or other materials. This approach has the disadvantage that the use of the substrate decreases the effectiveness of the sulfur-modified iron by reducing its surface area, and the advantage of being easier to suspend in the water than the particulate iron. Another potential advantage is to allow a combination with other catalysts. Application techniques exist in which the less movable substrate (suspended less easily) is more practical and desirable, such as in a point-of-use water filter. The science of water treatment has examined many of the reactions associated with the removal of toxic substances from water, including (a) chemical and biological oxidation and reduction phenomena; (b) formation of metal and non-metallic hydroxides or oxyhydroxides in conventional water treatment processes; (c) chemical precipitation procedures; (d) molecular sieve procedures such as reverse osmosis and ultrafiltration and (e) electromotive force procedures such as electrodialysis. The family of sulfur-modified iron processes developed according to the invention and described herein has not been described at atomic level 5 by water treatment researchers, nor have the performance characteristics of the process been defined independently of the work performed before this invention. Possibly the most closely related procedures are the reagent procedure of Fenton and WF ferric sulphide coagulation procedures that do not use particular chemicals. Recent experiments in the science of corrosion have produced photographs with atomic-level resolution of the formation of rust on the iron particles in the water. This work, reported by Roger C. Newman in "Science", vol. 263, 1708 and 1709, states that "the passive oxide film on the iron is not any of the hydroxides or ^ Oxihydroxides. "He further reports that" the iron in the film is surrounded by six oxygen atoms in an arrangement octahedron distorted, and these octahedrons share edges and faces, perhaps formed sheets or chains. "It is believed, according to this invention, that the oxide film that is formed on the porous and elemental iron in the presence of sulfur causes that one or more of the oxygen atoms are replaced with sulfur, causing the formation of the only surfactant treatment agent: sulfur-modified iron.

Through the procedures described herein, treatment with sulfur modified iron has removed flk precursors of DBPs, analyzed as Total Organic Carbon, from natural water sources at a concentration of 4 mg / L or less The concentration of Total Organic Carbon in the untreated water of test samples ranged from 6 to 20 mg / L. In the case of a paper mill acid channel effluent, the COD was reduced from 3080 to 2100 only with a reaction time of 15 minutes. 10 The modified iron with sulfur has also been removed ^ F in a consistent form arsenic from natural water sources to less than 5 μg / L (the practical quantitative limit of the test equipment used for analysis). The concentration of arsenic in the untreated water ranged from 34 to 170 μg / L. 15 Several examples of the results of the arsenic removal procedure are presented in examples 1 to 4, 6 and below. The examples demonstrating the results of the TOC removal procedure are presented in Examples 5 to 9 and 11 below. In the examples reported below, the amount of particulate iron used, compared to the amount by weight of arsenic contaminating the water, is commonly in a ratio of approximately 1000: 1, sometimes less, sometimes more. The amounts of iron powder varied in most cases from approximately .15 grams to .5 grams. However, it is believed that the amount of iron would be reduced to approximately .01 g / L, or even .005 g / L, for the effective removal of most of the contaminating arsenic in the sample amounts described. The amount of sulfur is generally maintained at about 5 weight percent of the iron quantity, which is believed to be congruent with the smaller amounts of iron projected above. The examples set out below used all granulated and powdered iron or "sponge iron", and the experience with the tests is believed that an effective scale of V iron particle sizes are approximately -20 to approximately -400 meshes. However, iron in any particle size will have some efficacy, in combination with the steps and other reagents described, to remove arsenic, TOC and AOX of water. One procedure for removing these contaminants, not described in the examples below, is to form a bed of modified iron particles with ^^ Sulfur, but with a larger particle size, up to about% of 2.54 cm. This bed, disposed of the In the manner of a granulated filter or contact bed, it provides a stable medium through which contaminated water is directed, by gravity or pumping. This arrangement can serve efficiently in a water treatment system.

EXAMPLE 1 ARSENIC IN WELL WATER A sample was obtained from the Water Agency of the Kern County as a part of the normal sampling carried out in the wells of the Kern Water Bank. The well is owned by the California Department of Water Resources. This well, designated 32N2, has naturally occurring arsenic. The sample was stored at approximately 1.1 ° C. In the water sampled during this test, the arsenic concentration was 170 μg / L. Except for the high concentration of arsenic, this well water is the typical well water used throughout the central California valley for domestic water service. This sample was treated for the removal of arsenic by intermittent treatment by the method and system of this invention. The starting temperature of the 1,000 mL sample was 15.5 ° C and the pH was 8.8. The sample was acidified to pH 4.3 with 3 mL of sulfuric acid to IN. To the sample of acidified water was added 0.3 grams of finely divided sponge iron and 0.1 gram of finely divided elemental sulfur (no premixture of iron modified with sulfur was prepared). The previously clear mixture became turbid. After about 1 hour and 20 minutes, one drop of hydrogen peroxide was added to the mixture; the pH was 6.1 before E-2O2 and 5.5 after. The mixture was stirred rapidly for a total time of 1 hour and 53 minutes after the iron was added, after which a sample of the decanted mixture was sent to a water quality certification laboratory for an analysis of the arsenic content. . The reported arsenic concentration was less than the practical quantification limit of 5 μg / L.

EXAMPLE 1 MARCH 28, 1994 • fifteen twenty ND = Not detected. Practical quantification limit = 5 μg / L.

EXAMPLE 2 ARSENIC IN WELL WATER Example 2 uses the same sample water source and treatment dynamics of Example 1 and is a confirmation of the methods of Example 1. The amounts of reagent and procedures varied slightly. EXAMPLE 2 APRIL 4, 1994 EXAMPLE 3 ARSENIC IN WELL WATER Example 3 uses the same sample water source and treatment dynamics of Examples 1 and 2. It is a confirmation of the methods of Examples 1 and 2, with slightly different amounts of reagent and procedures, including amounts of acid and iron . Note that the initial pH in Examples 1-3 is 8.8 to 9.3, with essentially complete arsenic removal. EXAMPLE 3 APRIL 17, 1994 EXAMPLE 4 ARSENIC IN WELL WATER Example 4 uses the same source of sample water and treatment dynamics of examples 1, 2 and 3, but no sulfur is added (except that present in sulfuric acid) .. It is a confirmation of the methods of the previous examples , but indicating that the removal of arsenic is not so complete without the addition of sulfur.

EXAMPLE 4 APRIL 17, 1994 EXAMPLE 5 TOC IN SURFACE WATER A sample of water, gallons, was taken from the ROCK Slough Bridge (Br. # RSB5 / 28), Contra Costa County, California, at the same point that the Contra Costa County Water District (California) samples its water for your water treatment plant. The sampling time was coordinated with the District's sample test. The purpose of This test and sample is to demonstrate the removal of total organic carbon from surface water. The treatment is essentially the same as that described in example 1. The main difference is that the treated water was rich in organic mineral chemicals that tend to bind to the iron and reduce its effectiveness in the treatment. It should be kept in mind that the TOC content in the samples will decrease somewhat with the time that passes after taking the sample, without any treatment, because a part of the TOC content is volatile.

EXAMPLE 5 APRIL 28, 1994 EXAMPLE 6 TOC AND ARSENIC IN SURFACE WATER This example used the same sample as the example , but "splashed" with arsenic by mixing 800 mL of surface water with 200 mL of water from well 32N2 from the Bank of Water of Kern, described in Example 1. " EXAMPLE 6 APRIL 29, 1994 EXAMPLE 7 TOC IN SURFACE WATER The same surface water from Rock Slough, a source of drinking water before treatment, was treated alone, without the addition of water containing arsenic. Tests were carried out using the method of the invention, to thereby reduce the concentration of TOC in water.

EXAMPLE 7 MAY 7, 1994 EXAMPLE 8 TOC IN SURFACE WATER The surface water sample was taken from the same point in Rock Slough as the previous examples three hours before this test. A short test period was used to develop the maturation data of the active agent. This experiment was carried out to determine the influence of the pH adjustment on the effectiveness of the active agent. The procedure appeared to remain effective at a higher pH, all other variables remaining the same, except the oxidizing agent, which was sodium hypochlorite in this test. This test also shows that the procedure works in the presence of alum, which is commonly used in municipal treatment plants.

EXAMPLE 8 MAY 10, 1994 EXAMPLE 9 TOC IN SURFACE WATER The surface water sample was taken from the same point in Rock Slough as the previous examples one hour and 40 minutes before this test. This sample was taken to investigate the performance of the active agent during severe deterioration in water quality. EXAMPLE 9 JUNE 1, 1994 EXAMPLE 10 ARSENIC IN WELL WATER TREATED WITH PREMIX OF IRON MODIFIED WITH SULFUR In this example, a premix of reagents in distilled water was prepared, before its introduction into the water well to be treated with arsenic. This shows that the reaction in the premix can be achieved, enough to form a mixture of concentrated and reactive reagent for its direct addition to the water to be treated, without the need for direct application of the individual unreacted reactants (iron, sulfur, oxidizing agent) to well water.

The advantage is that a much smaller reaction vessel and much less mixing energy is used to achieve the treatment compared to not using the premix. To one liter of distilled water was added powdered iron (sponge iron), elemental sulfur and 3% hydrogen peroxide solution. The quantities were as follows: grade B iron, 0.5 g; elemental sulfur, 0.2 g; per. { Hydr oxide { Ogen, 0.5 mL. No acid was included. These reagents were stirred in one liter of water for one hour. After the agitation, 980 mL of water were decanted from the sedimented mixture, leaving 20 mL of concentrated reagent mixture, that is, iron modified with sulfur. The concentrated reagent was then added to one liter of well water from the County of Kern with arsenic content of 40 μg / L. The procedure is shown in the following table: EXAMPLE 10 SEPTEMBER 10, 1994 This example shows that an effective mixture can be prepared and that removal of arsenic from drinking water will be achieved in substantially the same manner as with the previous examples which included the separate addition of each of the individual reagents. The example also shows that a considerable removal of arsenic is achieved, using the previous premix, at a very early stage of the procedure. More than 50% removal was carried out in the first ten minutes; 60% in the first twenty minutes. It is projected that the Removal would be complete to the extent that it remained less than 5 μg, if the reaction were to take approximately 45 minutes. Likewise, it is believed that the reaction would be accelerated if the peroxide were added to the complete well water pool, at a time subsequent to the addition of iron and sulfur. It is also believed that the process would be accelerated if acid were added to reduce the pH to an acid scale.

EXAMPLE 11 TOC REMOVAL (AOX) OF PAPER MILL ACID CHANNEL LIQUID In this test, procedures similar to the previous one applied to "acid channel" liquid effluent from a paper mill of James River Corporation. Example 11 involved the preparation of a premix of iron, sulfur and peroxide in distilled water, introducing the premix then into the acid channel liquid sample. The premix was prepared using a chemical laboratory mixer. The following table 11 reports the results of example 11, the different components of the acid channel liquid being quantified both before and after the treatment by the procedure of example 11.

EXAMPLE 11 JULY 31, 1994 EXAMPLE 11 Comb was noted, the results reported in Table 11 were taken from a JR2.2 sample, only after 15 minutis of reaction time of the iron premix modified with sulfur with the James River acid channel liquid sample. Table 11 shows dramatic results during this short reaction time. The COD was only reduced from 3080 mg per liter to 2100 mg per liter. AOX (purgeable organic halides) was reduced by 80, 000 to 58,900 μ / L. The tendency of the above examples and additional experience with the method of the invention have indicated that similar results will be obtained if the oxidizing agent, e.g., hydrogen peroxide, is added later in the reaction, ie not as part of the premix prepared, but after a certain reaction time of the iron and sulfur with the liquid. The described method and system removes a range of toxic substances in an economical and effective way in any municipal-sized large drinking water treatment plant or in smaller individual or industrial home units. The method and system can be applied as an individual treatment or in conjunction with other procedures. The original source of untreated domestic water or wastewater can be groundwater, surface water or certain industrial effluents. The preferred embodiments described above are designed to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to these preferred embodiments will be apparent to those skilled in the art and can be made without departing from the spirit and scope of the present invention.

Claims (5)

1. NOVELTY OF THE INVENTION ^ CLAIMS 5 1. - A method for removing arsenic from the water that is desired to purify, which comprises: establishing the pH of the water generally within a predetermined pH range including adjusting the pH if necessary; add elemental iron powder to the water; add sulfur to water; shake the water 10 to keep the iron and sulfur dispersed in the water; the ^ Amounts of powdered iron and sulfur are selected in combination to allow the recovery of arsenic with the additional steps of: continuing to shake the suspension; after a period of time in which the pH of the suspension is It then elevates and then generally stabilizes, oxidizing the suspension sufficiently to achieve recovery of arsenic as a precipitate, and continuing with the agitation of the suspension in substantially continuous form, and separating the recovered and precipitated arsenic to produce a treated water. 20 low in arsenic.
2. 2. The method according to claim 1, further characterized in that the predetermined pH scale is from about 3.5 to 8.5.
3. 3. The method according to claim 1, 25 further characterized in that the powder iron has a particle size on the scale of about -20 a approximately -400 meshes and is added in an amount of more than 100: 1 compared to the arsenic content of the water by weight.
4. 4. The method according to claim 3, further characterized in that the iron has a particle size at least as small as approximately 80% -325 mesh.
5. 5. The method according to claim 1, further characterized in that the oxidation step comprises adding hydrogen peroxide solution to the suspension. 6 - The method according to claim 1, further characterized in that the predetermined scale is from about 5.0 to about 8.5. 7. The method according to claim 1, further including, after the reaction with the powdered iron and sulfur, using a magnetic separator to remove any non-combined iron particle from the suspension. 8. The method according to claim 1, further characterized in that the amount of iron by weight is more than 1000: 1 and the amount of sulfur by weight is at least 500: 1 compared to the amount by weight of arsenic in solution in the water just before the addition of iron and sulfur. 9.- A method to reduce the total organic carbon (TOC) content in water that is desired to make drinkable, which includes: establishing the pH of the water, generally within a Default pH scale including adjusting the pH if necessary; add elemental iron powder to the water; add sulfur to the water, - stir the water to keep the iron and sulfur dispersed in the water; the amounts of powdered iron 5 and sulfur are selected in combination to allow the recovery of TOC with the additional steps of: continuing to stir the suspension; after a period of time in which the pH of the suspension rises and then generally stabilizes, oxidize the suspension enough to 10 achieve the recovery of OCD as a precipitate, and continue ^ stirring the suspension in a substantially continuous manner, and separating the recovered and precipitated TOC substances to produce a water treated with low TOC content. 15 10.- The method according to the claim 9, further characterized in that the predetermined pH scale is from about 3.5 to 8.5. ^^ 11. - The method according to the claim 9, further characterized because the iron has a size of 20 particle at least as small as approximately 80% -325 mesh. 12. - The method according to claim 9, further characterized in that the predetermined scale is from about 5.0 to about 8.5. 25 13.- A method to reduce COD (chemical oxygen demand), AOX (purgeable organic halides) and other potentially toxic reactive substances of water, comprising: establishing the pH of the water generally within a ^ Default pH scale, including adjusting the pH if necessary; add elemental iron powder to the water; Add 5 sulfur to water; stir the water to keep the iron and sulfur dispersed in the water; the amounts of the powdered iron and sulfur are selected in combination to allow the reduction of COD and AOX with the additional steps of: continuing to stir the suspension; after a period of time in the 10 which the pH of the suspension rises and then stabilizes ™ Generally, oxidize the suspension sufficiently to achieve recovery of the precipitates, and continue agitation of the suspension in substantially continuous form, and separate the recovered precipitates to produce a water 15 treated with reduced content of COD and AOX. 14. - The method according to claim 13, further characterized in that the predetermined pH scale is from about 3.5 to 8.5. 15. - The method according to claim 20 13, further characterized in that the powder iron has a particle size in the range of about -20 to about -400 mesh and is added in an amount of more than 100: 1 in comparison with the arsenic content of water by weight. 25 16.- The method according to the claim 15, further characterized in that the iron has a size of particle at least as small as approximately 80% -325 mesh. 17. The method according to claim 13, further characterized in that the predetermined scale is from about 5.0 to about 8.5. 18. - A method for producing a premix of sulfur-modified iron for use in the treatment of water to remove contaminants, comprising: adding water to a container; set the pH of the water generally at a predetermined pH scale, including adjusting the pH of the water if necessary; add elemental iron powder to the water; add sulfur to water; shake the water to keep the iron and sulfur dispersed in the water and remove the water from the suspension to form a concentrated premix of iron modified with sulfur. 19. The method according to claim 18, further characterized in that the pre-specified pH scale is from about 5.0 to 8.5. 20. The method according to claim 18, further characterized in that the iron has a particle size at least as small as about 80% -325 mesh. 21. The method of compliance with the claim 18, which further includes, after the step of stirring and after a period of time in which the pH of the suspension is raised and then stabilized, adding an oxidizing agent to the suspension. 22. - The method according to claim 21, further characterized in that the step of adding the oxidation agent comprises adding hydrogen peroxide solution to the suspension. 23. - The method according to claim 21, which further includes using the concentrated premixture of sulfur-modified iron to treat water subject to eventual human consumption, by the additional steps of: adding the concentrated premix of sulfur-modified iron to the water Subject to human consumption, stir the water to maintain the premix of modified iron with sulfur dispersed in the water, for a period of time sufficient to achieve the recovery of a precipitate with pollutants attached to the iron modified with sulfur and separate the recovered precipitate to produce a treated water. 24. The method according to claim 23, further characterized in that contaminants in the water subject to eventual human consumption include arsenic. 25.- The method of compliance with the claim 23, further characterized in that the contaminants in the water subject to eventual human consumption include TOC. 26. The method according to claim 18, which further includes using the concentrated premix of iron modified with sulfur to treat water subject to eventual human consumption, by the additional steps of: adding the Concentrated premix of sulfur-modified iron to water subject to eventual human consumption, shake the water to keep the premix of modified iron with sulfur dispersed in the water, the amount of premixture of sulfur-modified iron is selected to allow the recovery of one or more contaminants with the additional steps of: continuing to shake the suspension; after a period of time in which the pH of the suspension rises and then generally stabilizes, oxidize the suspension sufficiently to achieve the recovery of contaminants as a precipitate with the contaminant bound to the sulfur-modified iron, and continue the agitation of the suspension in substantially continuous form, and separating the recovered precipitate to produce a treated water.