WO1999019257A2

WO1999019257A2 - Processes and systems for treating wastewater effluent

Info

Publication number: WO1999019257A2
Application number: PCT/US1998/021477
Authority: WO
Inventors: Chrispin Reyna; Martin J. Plishka
Original assignee: Waste Water Reclamation Technologies, Inc.
Priority date: 1997-10-09
Filing date: 1998-10-09
Publication date: 1999-04-22
Also published as: AU1078799A

Abstract

The present invention is directed to a process for treating wastewater effluent, specifically from industrial processes. Contaminated wastewater effluent is treated acidified to a pH value below 7. The acidified wastewater effluent is then treated with a paste-type mixture containing magnesium hydroxide, activated carbon and water to form insoluble magnesium salts and simultaneously remove organics from the wastewater. The wastewater effluent is treated with a precipitating agent to precipitate contaminants from the wastewater effluent. A flocculating agent is then used to treat the wastewater effluent to reduce the colloidal and finely divided solids in the wastewater effluent. The substantially contaminant-free liquid effluent is separated from the contaminants by settling or filtering techniques. The substantially contaminant-free liquid effluent can be recycled back through the industrial process or discarded into a municipal sewer system with little or no municipal surcharge.

Description

PROCESSES AND SYSTEMS FOR TREATING WASTEWATER EFFLUENT

BACKGROUND OF THE INVENTION 1. The Field of the Invention

The invention relates generally to the treatment of wastewater effluent from industrial processes. More particularly, the invention relates to methods for decontaminating wastewater containing inorganic contaminates, organic contaminates, or both inorganic and organic contaminates.

2. Relevant Technology

Treatment of wastewater effluent from industrial processing has long been the subject of technical investigation and practical application due to the need for clean water. Until recently, wastewater effluent has been typically discharged into municipal water systems with little or no treatment. However, with more and more municipalities charging surcharge fees on industrial wastewater discharges the cost of simply dumping wastewater effluent has sharply increased. Hence, in addition to the long felt environmental interest, there is an increased economical emphasis on effective industrial wastewater treatment processes that allow for the discharge of effluent into municipal sewer systems with little or no surcharge. Even further there is an increased emphasis on the ability to recycle industrial effluent, thereby avoiding the cost of municipal discharge as well as decreasing industrial water demand.

Accordingly, numerous physical, chemical, and biological methods for the removal of various contaminates from solutions have been purposed. For example, U.S. Patent No. 5,360,551 issued to Weber, discloses a process for removing color from dye wastewater through acidification with subsequent use of a cationic flocculant. Weber further teaches the optional use of a reducing agent to produce a desired oxidation- reduction potential. The reducing agent disclosed in Weber is an alkali metal hydrosulfite, an alkaline earth hydrosulfite, and mixtures thereof, or combinations of an alkali metal bisulfite, an alkaline earth bisulfite, an alkali metal borohydride and mixtures thereof. While Weber provides an effective process for removing dyes, there are typically many more contaminants that need to be removed from wastewater effluent. Hence, other burdensome processed must be used either before or after the process in Weber to remove other contaminants, such as other organics, inorganics, as well as decreasing the biological oxygen demands and the chemical oxygen demands.

Likewise, U.S. Patent No. 5,611,934 issued to Shepperd, III et al., teaches a process for dye removal from wastewater effluent. The process in Shepperd, III et al. comprises treating dye containing effluent containing dye with a reducing agent, reducing the pH of the liquid effluent to a value in a range of 2.0 to 7.0, treating the liquid effluent with a charge neutralization mixture, adjusting the pH a second time to a pH value of greater than or equal to 5.0, and subjecting the mixture to a flocculant. The charge neutralization mixture taught in Shepperd, III et al. includes aluminum salts and cationic polymers. Here again, a problem is that Shepperd, III et al. does not remove a broad spectrum of organic and inorganic contaminants. Furthermore, Shepperd, III et al. require heating for all their process which increases the time and the cost of the decontamination process.

U.S. Patent No. 5,330,658 issued to Grant et al., discloses a method for decontamination of effluents contaminated with metals, organics, and radionuclides. The process disclosed in Grant et al. provides a separate treatment of the liquid effluent with ferrous sulphate and hydroxide, preferably sodium hydroxide, calcium hydroxide or ammonium hydroxide. The precipitate formed is treated with a flocculant and/or a coagulant to form a dewaterable sludge. Although Grant et al. decontaminate effluents containing metals, organics and radionucleotides, Grant et al. use sodium hydroxide, calcium hydroxide and ammonium hydroxide which produce a waste sludge by-product which requires expensive disposal. Furthermore, over addition of sodium hydroxide, calcium hydroxide and ammonium hydroxide can increase the pH of the effluent to excessive by high levels which require the pH of the wastewater effluent to be readjusted.

While other wastewater decontamination processes have been attempted, these processes have many of the same problems exhibited by the above-mentioned processes. Other wastewater decontamination processes include U.S. Patent No. 5,529,696 issued to Tibbits; U.S. Patent No. 5,529,697 issued to Braasch; U.S. patent No. 5,529,698 issued to Timmons; U.S. Patent No. 5,529,699 issued to Kuole; U.S. Patent No. 5,429,747 issued to Carr et al.; U.S. Patent No. 5,639,379 issued to Stogner; and U.S. Patent No. 5,076,937 issued to Montgomery et al.

In view of the above-mentioned drawbacks of the presently used wastewater decontamination processes, it is readily apparent there exists a need for a simple, inexpensive decontamination process that provides a substantially contaminate free liquid and a low volume precipitate material containing the contaminates which is easily separated from the decontaminated liquid. It is further apparent that there is a need for a versatile, decontamination process that is capable of removing a broad spectrum of contaminates from wastewater effluents from a wide range of industries.

SUMMARY AND OBJECTS OF THE INVENTION

It is, therefore, an object of the present invention to provide an inexpensive process for treating industrial wastewater effluent containing a wide range of organic and inorganic contaminants as well as wastewater effluents with high biological oxygen demands (BOD) and chemical oxygen demands (COD).

It is another object of the present invention to provide a simple, efficient process for treating industrial wastewater effluent that produces a low- volume sludge waste that can be sold as a nutrient rich fertilizer.

It is a further object of the present invention to provide a process for treating wastewater effluent which produces a substantially contaminant-free liquid effluent that can be recycled back into the industrial processes or safely discarded into a municipal sewer system with little or no surcharge. By recycling the effluent or discharging a substantially contaminant-free effluent into a municipal sewer system, expensive water discharging fees are avoided. To achieve the foregoing objects, and in accordance with the invention as embodied and broadly described herein, the present invention is directed to a process for treating wastewater effluent that uses a mixture of magnesium hydroxide and activated carbon to remove a wide range of organic and inorganic contaminants. The activated carbon provides a means for the adsorption of common organic materials, such as dyes, halogenated hydrocarbons (i.e., Trihalomethanes (THM's), volatile organic chemicals

(VOC's) and pesticides. The magnesium hydroxide precipitates inorganic materials as insoluble salts.

When magnesium hydroxide and activated carbon are mixed together with a small amount of water to form a high surface area paste-type mixture, the magnesium hydroxide and the activated carbon have a synergistic effect demonstrating a greater ability to decontaminate a wide range of organic and inorganic materials. Additionally, the paste-type mixture containing magnesium hydroxide and activated carbon lowers the BOD and COD of the wastewater effluent and provides a cite of nucleation for precipitation. The cumulative effect of the decontamination of the mixture containing magnesium hydroxide and activated carbon is the production of substantially contaminant-free effluent which results in an economical savings in both the disposal of the effluent and recycling of the effluent.

In accordance with the present invention, and contrary to conventional knowledge, it has been discovered that a broad spectrum of cont.amin.ants can be removed from an industrial wastewater effluent by adjusting the pH of the wastewater effluent so that the wastewater effluent has a pH value below 7; treating the acidified wastewater effluent with a mixture comprising magnesium hydroxide and activated carbon; and treating the wastewater effluent with a flocculating agent. The result of this treatment process is that the organic contaminants and the inorganic contaminants are either adsorbed by the activated carbon, precipitated from the wastewater effluent as insoluble salts or precipitated from the solution by the flocculating agent, to form a waste sludge material. The waste sludge material is easily separated from the liquid effluent by filtration or settling of the waste sludge material. The waste sludge material can then be discarded or sold as a magnesium rich soil supplement or fertilizer. The substantially contaminant-free liquid effluent can be either discharged into a municipal sewer system with little or no municipal surcharge or recycled back into the industrial processing system.

These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and other advantages and objects of the invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawing. Understanding that this drawing depicts only a typical embodiment of the invention and is not therefore to be considered to be limiting in its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawing in which:

Figure 1 is a diagrammatic representation of a wastewater effluent treatment system used with the inventive wastewater effluent treatment process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a process for treating a liquid effluent containing a broad-spectrum of contaminants, such as organics, such as grease and oils, and inorganics metals and total suspended solids (TSS). The present invention further provides a process for treating effluents having high biological oxygen demands (BOD) and high chemical oxygen demands (COD). Each of these contaminants are taken into account and are significant contributors when calculating municipal surcharges.

While the present invention is useful in treating effluent from a wide range of industries including food processing, electronics manufacturing, metals plating, pulp and paper and the like, the present invention is particularly useful for decontaminating and recycling water from liquid effluent produced from textile and dye plants including the processing of stonewashed and/or sandblasted garments wherein detergents, enzymes, surfactants, silicates, dyestuffs, cotton lint, synthetic fibers, bleach, coloring and particulates that must be removed from the liquid processing effluent, so that the water is sufficiently contaminate free to be discarded into a municipal sewer system with little or no municipal surcharge fee or recycled back through the industrial process for reuse. The present process allows the reclaimation of greater than 95% of the water originally present in the industrial process. The substantially contaminant-free liquid effluent removed from the process may be reused many times over before a need exists to discharge any wastewater. The present invention is inexpensive to practice and systems necessary for its practice are also inexpensive to practice and operate.

For the purposes of this application, the terms "flocculant," or "flocculating agent" are defined as a high-molecular weight polymer which bridges from particle to particle and "coagulant" is a mixture of low-molecular weight cationic polymer(s) bearing high charge.

Generally, the present invention is a multi-step decontamination process wherein the pH value of the wastewater effluent is adjusted to have a pH value in a range up to about a pH of 7. The acidified wastewater effluent is then treated with a mixture comprising magnesium hydroxide and activated carbon, also referred to as activated charcoal, to form insoluble magnesium salts and to reduce the organic contaminant concentration in the wastewater effluent. The activated carbon adsorbs the organic contaminants in the wastewater effluent and provides a site of nucleation. The wastewater effluent is then treated with a precipitating agent to form a precipitant containing inorganic contaminants. Finally, the stream is treated with a flocculating agent to reduce the colloidal and finally divided solids in the liquid effluent by binding the floes into tight, easily-settled masses. The solids, which includes the precipitated materials and the activated carbon, are then removed by any suitable separation technique known in the art, including settling or filtration. The effluent stream can then be discarded into a municipal sewer system or recycled back into the particular manufacturing operation.

Some of the advantages of this inventive process over the previously attempted wastewater decontamination processes are the ability of the present process to remove a wide range of contaminants from a wide range of industries in a simple, efficient and inexpensive process. Furthermore, the use of magnesium hydroxide produces a magnesium-rich sludge which can be resold as a nutrient rich fertilizer, rather than paying to have the solids hauled off as waste. These advantages result in substantial savings in manufacturing and disposal costs.

In a preferred embodiment of the present invention for treating wastewater effluent from industrial processes, the wastewater effluent can optionally be filtered prior to subsequent chemical treatment. Filtration is especially useful in treating wastewater effluents in such industries as "jeans" "stonewashing" processes. Since the present inventive processes envision continuous flow treatment of effluent of only a few gallons and up to millions of gallons daily, initial filtration may not be desirable. As long as the particulate material which may be removed by initial filtration is not converted to dissolved materials by subsequent chemical treatments, whereby the nearly dissolved materials would be difficult to remove by subsequent chemical treatments, the filtration step may be omitted.

Initial filtration can be affected by passage of the wastewater effluent through a shaker with a mesh size (J size) of 120 microns to remove large particles, such as pumice or similar abrasive or other contaminants which are large enough to be trapped by filtration.

The preferred inventive processes include the step of acidification subsequent to the optional initial filtration step, so that the pH of the wastewater effluent has a pH value up to about 7, and preferably has a pH in the range between 2 and 7. Any suitable acid can be used to adjust the pH of the wastewater effluent below a pH of 7. Sulfuric acid (preferably 66° Baume typically having an activity of 93%) is the preferred acid used in the step of adjusting the pH of the wastewater effluent. The acidified wastewater effluent is further treated with a mixture comprising magnesium hydroxide and activated carbon (also commonly referred to as activated charcoal). The acidified wastewater effluent is contacted with the mixture of magnesium hydroxide and activated carbon. The magnesium hydroxide and activated carbon are preferably mixed with an amount of water to form a paste-type mixture to provide a high surface area for the wastewater effluent to contact. The activated carbon removes color and a broad range of organics from the wastewater effluent by a physical adsorption means. Magnesium hydroxide forms insoluble magnesium salts as the wastewater effluent flows in an around the paste-type mixture formed from the magnesium hydroxide and activated carbon. A portion of the paste can be cycled to a subsequent settling tank for further reaction with the wastewater effluent.

Although it is preferred to remove the precipitated magnesium salts at the completion of all the chemical treatment steps, the insoluble magnesium salts can be removed at any time during the treatment process. Separation of the precipitated magnesium salts can be accomplished by any known means of separation, including, but not limited to, settling or filtration prior to addition of other chemical substances used in the inventive process.

The paste-type mixture is preferably formed by addition of magnesium hydroxide in a range from about 5% to about 85% by weight (commercially available as MAG-50 and MHT-50 available from Dow Chemical, Midland, Michigan. It should be noted that

MAG- 50 and MHT-50 are a 50:50 mixture of magnesium hydroxide and water) with about 5% to about 95% by weight of activated carbon. In a preferred embodiment, the magnesium hydroxide concentration is in a range between about 40% and about 80% and is more preferably about 67%. In a preferred embodiment, the activated carbon concentration is in a range between about 20% and about 75%, and is more preferably about 33%. The relative concentrations of the magnesium hydroxide and the activated carbon used in the paste-type mixture will be dependent upon the type of industrial wastewater effluent that is being treated and the type of contaminants to be removed. It should be noted that although magnesium hydroxide provides many advantages and is, thus, preferred in the invention, other hydroxides, such as sodium hydroxide, calcium hydroxide, ammonium hydroxide, or aluminum hydroxide can be used in the present invention. However, some of the significant advantages of using magnesium hydroxide over other hydroxides include the following: the waste sludge precipitated from the wastewater effluent is useful as a magnesium rich fertilizer and can be sold as a marketable product as opposed to requiring disposal as with the other hydroxides; magnesium hydroxide generates a waste sludge that is more dense and, thus, lower in volume than the other comparable hydroxides; magnesium hydroxide is safer and easier to handle than other hydroxides and, thus, requires less expensive handling equipment; and an additional economic advantage of magnesium hydroxide is that the over addition of the paste-type mixture of magnesium hydroxide and activated carbon does not excessively increase the pH of the waste stream as do sodium hydroxide and calcium hydroxide, thus the waste streams do not have to be readjusted with acid prior to disposal into municipal sewer systems. In certain situations, such as when chlorine bleach is present in the wastewater effluent, it may be desirable to include sodium hydroxide in an amount up to about 5% by weight of the paste-type mixture, and preferably about 0.5% by weight of the paste- type mixture.

In an alternative embodiment of the present invention, the magnesium hydroxide and the activated carbon can be added individually without forming a mixture. When the magnesium hydroxide and the activated carbon are added to the wastewater effluent separately, the order in which the magnesium hydroxide and the activated carbon are added to the wastewater effluent is irrelevant.

In a preferred embodiment, the magnesium hydroxide and the activated carbon are mixed with water to form a paste-type mixture. When the magnesium hydroxide and the activated carbon are mixed to form a paste-type mixture, the combination of the magnesium hydroxide and the activated carbon exhibit a synergistic effect. For example, the activated carbon will adsorb a broad range of organics and the magnesium hydroxide will form insoluble magnesium salts with inorganic contaminants, however, the combination of the magnesium hydroxide and the activated carbon will result in the decontamination, whether it be by adsoφtion or precipitation of a broader range of decontaminants than when the magnesium hydroxide and the activated carbon are used separately. Not wishing to be bound by theory, it is believed that this synergistic effect is a result of the precipitation or co-precipitation of materials which bind or otherwise included with contaminants being removed from the wastewater effluent. This synergistic could be due to the longer time period that the wastewater effluent is in contact with both the magnesium hydroxide and the carbon. Furthermore, the activated carbon acts as a nucleating site for precipitation. As the activated carbon adsorbs contaminants, the size of the activated carbon and thus the nucleating sites increases, facilitating precipitation.

The wastewater effluent is then preferably treated with a precipitating agent to form a precipitant comprising undesirable contaminants. Suitable precipitating agents include ferric sulfate, ferric chloride and sodium aluminate. The precipitating agent may be used singly, in mixtures of the precipitating agents, or in combination with carbonates, lime and alum. The precipitating agents are used to precipitate other ionic materials from the solubilized state which were not removed by the magnesium hydroxide.

The wastewater effluent is then treated with a flocculating agent. Suitable flocculating agents include polyacryonitrile, polyacrylamide, epichlorohydrin polymers, ammonium chlorides, polydimethylammonium chlorides, amines and mixtures or derivatives thereof. Flocculating agents may be anionic, cationic, non-ionic, or be a mixture thereof. In a preferred embodiment, polyacrylamide is used to flocculate materials which are not absorbed by the activated carbon or precipitated by the precipitating agents referred to above. Colloidal and finely dispersed suspended matter is effectively removed from the wastewater effluent by treatment with flocculating agents and the precipitating agent disclosed herein. The precipitated materials and the flocculated materials can then be separated from the substantially contaminant-free liquid effluent using any separation technique known in the art, such as settling and filtration. The resultant high purity water can then be recycled back through the industrial process, such as a stonewashing process or other wastewater effluent-producing process, or the high purity water can be discharged as a system effluent which meets applicable environmental regulations. Using the present process, the water can be recycled through the industrial processing system multiple times prior to the need for discharge. The inventive wastewater effluent-treating process can be used in conjunction with other conventional filtration methods, including, but not limited to dissolved air- floatation (DAF), Shaker filters, screen filters, paper/cellulose carbon and the like.

It is also understood that the final pH of the effluent can be adjusted to comply with municipal, state or federal disposal regulations. In addition, the final pH of the effluent can be adjusted to meet specific industrial recycling criteria.

The temperature of the wastewater effluent can be between 0°C to 100°C. In a preferred embodiment, a temperature of about 45°C to about 55°C should be maintained in the wastewater effluent to aid the rate of the chemical treatment. It should be noted that higher temperatures can adversely affect solubilization, the formation of complexes or flocculation within the wastewater effluent.

In another embodiment of the present invention, a wastewater recovery system for treating a liquid wastewater effluent is illustrated in Figure 1. Wastewater recovery system 10 illustrates one particular system architecture which can be utilized in accordance with the present invention to practice the treatment processes of the present invention. Wastewater effluent enters system 10 at entrance 12. The wastewater effluent being from an industrial process such as from a garment stonewashing process, wherein such effluent typically includes abrasives such as pumice, bleach, detergents and enzymes, as well as lint, fibers, dissolved silicates, paniculate solids and organics including dyestuffs removed from the garment during stonewashing or added during the stonewashing process in order to affect a desired appearance of the processed garments. Wastewater effluents from garment washing processes such as stonewashing processes also typically include soluble surfactants. Here again, although the preferred embodiment illustrates the wastewater effluent from as stonewashing garment process, it is appreciated that wastewater effluents from other industries such as hide-processing, food processing, particularly beef slaughterhouse waste processing, pulp and paper processing, railcar and locomotive washing, metals and plating, mining, semiconductor and manufacturing and other textile and dye applications can used with the present system. The wastewater effluent is optionally filtered or subjected to a physical separation process for the removal of particularits including large pieces of pumice. A filter (not shown) is an example of a separation means that can be used with the present inventive system. Other conventional separatory processes including shaker filtration and screen filters with mesh sizes of approximately 100 to 120 microns are preferred. If the filtration step is not necessary, the wastewater effluent is directed into tank 14 without being subjected to a filtration or other separatory process. The wastewater within tank 14 is acidified with a suitable acid from acid storage unit 16 causing the pH of the wastewater to have a pH value up to about a pH of 7. The acid is charged into tank 14 from storage unit 16 by known automated control systems. A paste-type mixture of magnesium hydroxide and activated carbon is discharged into tank 14 from paste storage unit 18. The paste-type mixture is formed by mixing magnesium hydroxide, activated carbon and a sufficient amount of water to maintain a fluidity of the paste-type mixture. In one embodiment of the present invention, sodium hydroxide is added to the paste-type mixture in about V2% by weight of the paste-type mixture. By way of example, a mixture of magnesium hydroxide and activated carbon is formed on an industrial scale by adding about 600 lbs. of MAG-50 magnesium hydroxide with 100 lbs. of activated carbon.

The wastewater effluent contacts the magnesium hydroxide/activated carbon paste-type mixture within the interior of tank 14 preferably in a continuous flow process.

The activated carbon removes coloring agents as well as other organic contaminants from the wastewater in an absoφtion type manner. Magnesium hydroxide in the paste-type mixture forms insoluble magnesium salts and precipitates dissolved materials from the wastewater effluent. The wastewater effluent is then pumped from tank 14 to tank 20 by means of a suitable pump 22. The wastewater entrains in its flow the insoluble salts produced in tank 14 as well as colloidal materials. In tank 20, precipitating agents such as ferric sulfate, ferric chloride and aluminum sulfate and mixtures thereof are added to the wastewater to precipitate material which were not precipitated by the magnesium hydroxide in tank 14. Carbonates, lime and alum can be combined with the precipitating agents to enhance precipitation of solubilized contaminants.

A flocculating agent, such as water soluble polyacrylonitrile polymer is charged into the interior of tank 20. A polyacrylamide, specifically NOVAFLOC™ PHA, can be added at a level of 0.25% to 0.50% by weight of the effluent wastewater to cause flocculation of materials which have either not been adsorbed by the activated carbon, precipitated by the ferric or ferric-based compounds, or precipitated by the magnesium hydroxide. The precipitating agent and respective flocculating agents are preferably added from storage units 24, 26 and 28, respectively such as by automated control apparatus 30. Control apparatus 30 in a conventional embodiment is capable of controlling wastewater flow and material flow throughout system 10.

The treated contents of tank 20 are moved to clarification tank 34 by means of pump 36, where clarification occurs, removing haze from the wastewater effluent through settling of precipitated materials and extraction of the precipitated materials in later stages through filtration or other separatory processes. The treated aqueous contents of clarification tank 34 are preferably moved via pump 32 to settling tank 38 to further remove precipitated solids and other contaminants. At least a portion of the contents of settling tank 38 can be recycled from tank 38 to a process water makeup location (not shown) where water is stored for use in an industrial process which produces the wastewater effluent treated according to the present invention. The paste-type mixture can be cycled into tank 34 to provide additional reaction time between the paste-type mixture and the wastewater effluent. Settled materials removed from tank 4 are preferably taken to a filter press 40 by means of a pump 42. The filter press typically uses diatomaceous earth as a filter medium to produce a waste sludge 44 which is removed from system 10 and discarded as solid waste.

Reclaimed water in tank 46 can be recycled or discharged as desired respectively through plumbing at 48 and 50, wherein the reclaimed water is moved by pump 52. Control of the pH of the reclaimed water is effected at 54 by means of appropriate pH control equipment and chemical agents contained in storage unit 56. Approximately 95% of the treated water within clarification tank 34 is taken directly to reclaimed water tank 46, wherein the water is sufficiently pure to recycle the water or discharge the water. Purified water from the settling tank 38 is typically recycled to a process water makeup location (not shown) or recycled to tank 20 by means of pump 58. Particular note is taken of the paste-type mixture composed of magnesium hydroxide and activated carbon involved in the wastewater effluent treatment in tank 14. The paste-type magnesium hydroxide/activated carbon mixture preferably exists in tank 14 in the form of a bed having a higher specific gravity than the wastewater effluent which is introduced into tank 14. Accordingly, the bed of magnesium hydroxide/activated carbon lies at the bottom of tank 14 with the wastewater effluent flowing therethrough .and into contact therewith over surfaces of the bed of material. During this treatment, both magnesium hydroxide and carbon are being sacrificed in order to clarify and precipitate materials from the wastewater effluent.

Depending upon the capacity of system 10, the present processes intends to be continuous in nature and to process from 1,000 to 1,000,000 gallons per day of wastewater effluent. The capacity of the pump units and the size of the tanks chosen for the present system 10 allow high efficiency within a low cost treatment system.

Physical separatory processes including filtration and settling remove precipitated and flocculated materials. Water may thus be reclaimed and reused many times over prior to discharging from system 10. System 10 can further include monitoring and control modules such as control 30 to support fully automatic operation of system 10. System architecture can include a filtration apparatus, such as a shaker filtration apparatus, that is capable of filtering the wastewater effluent in the initial optional filtration step. Alternatively, filtration can be accomplished using a filter press apparatus utilizing diatomaceous earth, or bag filters, as well as other filtration devices known in the art.

Tanks used for the acidification of the wastewater effluent as well as other chemical treatment steps, including clarification can be tanks having conical lower portions which facilitate settling of the waste sludge and subsequent removal of the waste sludge.

The present inventive system can be automated to include pH monitoring and pH control. In addition, all the system plumbing, including pumps, inlets, drains and other connections which involve charging of treating materials into the wastewater effluent are also automated.

The processes of the invention can be practiced other than as explicitly described herein with system architecture being other than as particularly shown in the drawing. It is further to be understood that wastewater effluents emanating from differing industrial processes can be treated according to the invention without substantial departure from the process explicitly described hereinabove for the treatment of wastewater emanating from a garment washing or stonewashing process. Accordingly, the scope of the invention is to be determined from the scope of the claims appended hereto.

EXAMPLES

The following examples are presented in order to more specifically teach the process for treating wastewater effluent according to the present invention. The examples include various mix designs and results from various test runs.

EXAMPLE 1

The mixture of magnesium hydroxide and activated carbon was optimized for wastewater effluents contaminated with blue dye and liquid detergent. Thirteen different magnesium hydroxide/activated carbon mixtures were prepared, wherein each of the different mixtures was prepared having a different magnesium hydroxide/activated carbon mixture.

In the present process, the pH of thirteen different contaminated wastewater effluent samples were adjusted have a pH between about 3 to about 4 using sulfuric acid. Each of the different combinations of the magnesium hydroxide/activated carbon mixtures were added to different acidified wastewater effluent samples. The pH was adjusted to about 10 to about 11 with the introduction of magnesium hydroxide and an anionic polymeric flocculating agent was added to each of the contaminated wastewater effluents to floe out the precipitate.

Ultraviolet visable (UV-VIS) spectra were recorded on each of the wastewater effluent samples. The relative intensities of the spectra were compared at 208 and 580 nm. The 208 nm measurement represented the total organic content, and the 508 nm measurement represented the dye intensity.

The results indicate (for wastewater contaminated with blue dye and liquid detergent) that a higher activated carbon ratio and a low magnesium hydroxide ratio provided the most effective decontamination. The best magnesium hydroxide/activated carbon paste-type mixture was composed of activated carbon in about a 95 % concentration and magnesium hydroxide in about a 5 % concentration (i.e., a ratio of 50% carbon/5% magnesium hydroxide MAG-50; and 45% water were used to form the paste- type mixture).

EXAMPLE 2 A sample of wastewater effluent from a cheese process plant was obtained for an analysis. The water was milky- white and opaque as received. About a 400 mL of sample of the wastewater effluent was used to determine the effectiveness of the inventive process. The pH of the wastewater effluent was adjusted to a pH of between about 3 and about 4 with sulfuric acid. About 0.5 g of a paste-type magnesium hydroxide/activated carbon mixture (not optimized) was added to the wastewater effluent and stirred for about 1 minute. The pH of the wastewater effluent was then adjusted to a pH value between about 10 and about 11. Then about 20 n L of a 100 ppm anionic polymer (NOVAFLOC PHA™) was added and stirred for about 1 minute. Then about 5 mL of AGEFLOC™ WT20HV was added to the wastewater effluent and stirred. A complete separation occurred leaving a heavy dark precipitate and a very clear supernatant liquid. The clear supernatant liquid was separated by decanting clear liquid off the heavy dark precipitate.

EXAMPLE 3 The recyclibility of wastewater effluent was determined using the present inventive process. A paste-type mixture of magnesium hydroxide and activated carbon was formed by mixing about 36% DOW MHT-50 (DOW MHT-50 comprises about 50

% water and about 50 % magnesium hydroxide) with 9% activated carbon and diluted to 100% with water.

One hundred (100) mL of water was placed in a 250 mL beaker and two drops of concentrated blue dye (RIT dye) was added along with 2 mL of laundry detergent to form a simulated wastewater effluent. The pH of the wastewater effluent was acidified by adding sulfuric acid. Two mL of 0.1 ppm ferric sulfate was added to the wastewater effluent along with 0.5 g of the paste-type mixture of magnesium hydroxide and carbon paste. The pH of the wastewater effluent was raised to a pH value between about 11 and about 12. Ten mL of anionic polymer NOVAFLOC PHA™ was added to the wastewater effluent .and stirred until a precipitate formed and settled and a clear supernatant resulted.

The supernatant was decanted off and the re-contaminated. The present process was repeated by adding approximately 10% make-up water and re-dying the solution. This procedure was repeated successfully seven times until the same water could not be recycled any longer. A four- variable, three-level experimental design was run later to optimized the conditions of the present process for the dye experiment. Spectral absorbances at 208 nm and 508 nm confirmed the absence and the presence of dye and other organics compared with standards that were also analyzed. EXAMPLE 4 Two types of actual laundry wastewater effluents were tested using the inventive process used in Example 3. The results of this process resulted in reductions in oil and grease from 65 to 2, and 824 to 3 respectively. Chemical oxygen demands for the laundry wastewater effluents were likewise reduced from 1280 to 261; 654 to 140; 870 to 287; and 1890 to 41; and bacterial oxygen demands were reduced from 9000 to 560; and 121 to 7. Total suspended solids were also dramatically reduced. Removal of these contaminants results in a significant reduction in municipal surcharge fees.

EXAMPLE 5 The process in Example 3 was repeated on wastewater effluent having the following contaminants to give the following results:

SAMPLE DESCRIPTION: Before After

ANALYSIS Pretreatment Pretreatment

COD, Chemical Oxygen Demand, mg/L 2800 140

Total Suspended Solids, mg/L 370 10

Oil and grease, mg/L 380 <2

Cadmium, mg/L as cd 0.14 0.026

Copper, mg/L as Cu 0.58 0.07

Lead, mg/L as Pb 1.9 0.2

Zinc, mg/L as Zn 0.75 <0.01

Methylene chloride, ug/L (Dichloromethane) 58 13

Chloroform, ug/L <5.0 <0.5

1, 1, 1-Trichloroethane, ug/L 55 0.9

Trichloroethane, ug/L <4.0 <0.4

Tetrachloroethane, ug/L 20 <0.3

Toluene, ug/L 700 2.7

Ethylbenzene, ug/L 120 0.3

Total Xylene, ug/L 660 1.6 pH, standard units 8.7 9.3

These results illustrate the effectiveness of the present process in removing a broad spectrum of contaminants from wastewater streams.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrated and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

What is claimed and desired to be secured by United States Letters Patent is:

Claims

1. A process for treating a liquid effluent having an inorganic contaminant, an organic contaminant or an inorganic contaminant and an organic contaminant, the process comprising the steps of: adjusting the pH of the liquid effluent to a pH value up to about 7; treating the liquid effluent with a mixture comprising magnesium hydroxide and activated carbon; and treating the liquid effluent with a flocculating agent.

2. A process as recited in claim 1, wherein the steps of treating the liquid effluent with the mixture of magnesium hydroxide and activated carbon and treating the liquid effluent with a flocculating agent, reduce and precipitate the contaminant in the effluent, and the process further comprising separating the liquid from the contaminant.

3. A process as recited in claim 1, further comprising treating the liquid effluent with a precipitating agent.

4. A process as recited in claim 3, wherein the precipitating agent is selected from the group consisting of ferric sulfate, ferric chloride and sodium aluminate.

5. A process as recited in claim 3, wherein the step of treating the liquid effluent with a flocculating agent is performed after the step of treating the liquid effluent with the mixture of magnesium hydroxide and activated carbon.

6. A process as recited in claim 1, further comprising filtering the liquid effluent before the liquid effluent is mixed with the mixture of magnesium hydroxide and activated carbon.

7. A process as recited in claim 1 , further comprising the step of treating the liquid effluent with a caustic soda after the step of adjusting the pH of the effluent to have a pH in a range up to about a pH of 7 and before the step of treating the liquid effluent with the mixture of magnesium hydroxide and activated carbon.

8. A process as recited in claim 1 , wherein the step of adjusting the pH of the liquid effluent comprises the addition of an acid to result in the liquid effluent to have a pH value in a range between about 2 and about 7.

9. A process as recited in claim 8, wherein the acid is sulfuric acid.

10. A process as recited in claim 1, wherein the mixture of magnesium hydroxide and activated carbon comprises magnesium hydroxide in a range between about 30% and about 95%, and activated carbon in a range between about 5% and about 70%.

11. A process as recited in claim 10, wherein the mixture of magnesium hydroxide and activated carbon further comprises sodium hydroxide in a range below about 5%.

12. A process as recited in claim 1, wherein the process for treating a liquid effluent produces a precipitate and wherein the precipitate comprising magnesium and wherein the precipitate is separated from the liquid effluent and used as a fertilizer.

13. A process as recited in claim 1 , wherein the flocculating agent comprises a polyacrylonitrile polymer.

14. A process as recited in claim 1, wherein the flocculating agent comprises a polyacrylamide.

15. A process as recited in claim 1 , wherein the flocculating agents selected from the group consisting of amines, polyacrylamides, ammonium chlorides and polydimethylammonium chloride.

16. A process for treating a liquid effluent having an inorganic contaminant, an organic contaminant or an inorganic contaminant and an organic contaminant, the process comprising the steps of: adjusting the pH of the liquid effluent to a pH value up to about 7; treating the liquid effluent with magnesium hydroxide; treating the liquid effluent with activated carbon; and treating the liquid effluent with a flocculating agent.

17. A process for treating a liquid effluent having an inorganic contaminant, an organic contaminant or an inorganic contaminant and an organic contaminant, the process comprising the steps of: adjusting the pH of the liquid effluent to a pH value in a range between about 2 and about 7; treating the liquid effluent with a mixture comprising magnesium hydroxide and activated carbon to form insoluble salts and to reduce the organic contaminant concentration in the liquid effluent; treating the liquid effluent with a precipitating agent to form a precipitate comprising an inorganic contaminant; treating the liquid effluent with a flocculating agent to reduce colloidal and finely divided solids in the liquid effluent; and separating the liquid effluent from the precipitated materials.