MXPA99004291A - Water treatment process - Google Patents

Abstract

A process for the treatment of waste waters containing chemically reducible dissolved organic and inorganic pollutants and suspended matter in particulate or colloidal form. The process comprises contacting the water with metallic iron or ferrous ions (Fe2+), or mixtures thereof, in the presence of promoter metals, such as Cu, Pd, Pt, Au, Ag, and Ni, or oxides, sulfides and other insoluble compounds of these metals, which catalyze the redox reductions carried out by the iron or ferrous reagents. The production of ferric ions (Fe3+) as a final iron oxidation product allows for the simultaneous coagulation and precipitation of suspended colloidal and particulate solids out of the aqueous phase. In addition to the main reductive reaction scheme, the system performs a multitude of secondary reactions involving the ferrous and ferric ions produced in-situ which allows for the simultaneous removal of specific target polluants, such as phosphate and hydrogen sulfide. The net effect of a treatment in accordance to this invention is the decrease in a wide range of carbonaceous, nitrogenous and other targeted pollutants present in a waste water stream in a dissolved, colloidal or particulate form and the chemical conversion, commonly referred to as"softening", of non-readily biodegradable pollutants through a generally complex set of reactions and physical processes. As a result, the implementation of the process prior to or in parallel to conventional biological treatment makes the latter more feasible, more efficient, more economical in terms of both capital investment and operating cost and, also, the finally discharged water more compatible with environmental demands.

Description

WATER TREATMENT PROCESS FIELD AND BACKGROUND OF THE INVENTION "" This invention relates to a water treatment process, in particular, to a process for the treatment of waste water containing organic and inorganic contaminants, dissolved, which can be chemically reduced, and suspended matter in the form of particles or in colloidal form. The process of the invention is particularly useful for the treatment of waste water from the wood industry, wood based panel, pulp and paper industries, as well as tannery effluents, oil waste such as engine oil or olive oil waste, dry cleaners, fiber industries, textile industries and other industries, which among other pollutants contain large concentrations of complex organic pollutants of high molecular weight, which are commonly referred to as macromolecules, together with big REF. : 30286 concentrations of suspended particles and, consequently, are difficult to completely treat through the use of standard biocal processes. An additional specific application of the process is the reductive decomposition of organic nitrogenated and hanated contaminants that can then be easily removed through conventional biocal methods. Another application of the process is the elimination of inorganic species such as nitrate, nitrite and phosphate, through their chemical uptake in the form of insoluble compounds that can be easily removed by precipitation. The net eoflect of the treatment proposed here is the decrease in the global load of contaminants present in a given wastewater stream and the chemical conversion, commonly referred to as "softening", of non-biodegradable contaminants, through a set of oxidation-reduction reactions, generally complex, in such a way that the current is subsequently treated more completely, more effectively and at a lower cost, through conventional anaerobic and aerobic biocal treatment processes, such as Denitrification and activated sludge systems. In the different stages of industrial manufacturing processes, such as wood treatment and papermaking, large amounts of water are used. Although significant improvements have been made in the conservation or reuse of water, in these processes, it is still necessary to discharge a certain amount of wastewater from the system. The effluent of process water from process and manufacturing plants is often a colored, turbid, odoriferous liquor consisting of water, dissolved contaminants and suspended matter, in the form of particles. Disposal of large quantities of these process effluents to adjacent streams and bodies of water can result in contamination of the latter, causing, among other things, the water to acquire an objectionable color and odor. The composition of industrial wastewater is typically quite complex and often comprises tens or even hundreds of different chemical species in a dissolved, colloidal or particulate form. As a result, the overall quality of a certain waste water stream is conventionally measured by the combined use of concentrated composition parameters denoting the overall concentration of whole groups of contaminants with a common characteristic (eg, carbonaceous compounds, organic nitrogen, solids). suspended, color, odor, hanated organic compounds, total phosphorus, total phenols, etc.) and the actual concentrations of individual pollutants (eg, various heavy metals, etc.) to which attention is specifically focused due to the effects particularly harmful to living species. Among these quality markers, the global load of carbonaceous organic pollutants, which can be oxidized (the so-called "hardness of waste water"), comprises most of the time the main interest with respect to water pollution and is therefore regulated quite strictly in most areas. The total concentration of carbonaceous organic pollutants, which can be oxidized, in a certain stream of wastewater, is conventionally characterized by its Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). The Chemical Oxygen Demand (COD) of an aqueous sample is a measure of the oxygen consumption during the chemical oxidation of its organic carbonaceous components, by a strong chemical oxidant, under standard reaction conditions that assure the oxidation of at least 95% of existing total carbonaceous or organic contaminants. When precautions are taken to minimize interference by the oxidation of inorganic species, the COD can be used to describe relatively accurately the total concentration of organic carbon present in a given aqueous stream. The Biochemical Oxygen Demand (BOD) of an aqueous sample, is a measure of the oxygen consumption during the biological oxidation of its carbonaceous organic components, by an aerobic microbial culture and is determined using standardized laboratory procedures by which the aqueous sample is contact with an appropriate microbial culture, for a predetermined period of time. Since biological oxidation is a relatively slow process, the resulting BOD value depends on the contact time used. Conventionally a contact period of five days is used, hence the nomenclature "BOD of 5 days or DB05". When precautions are taken to minimize interference due to the concurrent biological oxidation of certain inorganic species, such as sulfides, and ferrous iron, and reduced forms of nitrogen (Nitrogenized Oxygen Demand), BOD can be used as a measure of the concentration total of the biologically degradable organic carbon, present in the given aqueous stream. Based on the above definitions, the DQ0: DB05 ratio of a given wastewater denotes the ratio of the total, carbonaceous organic pollutants to the biodegradable, and can thus be used as a measure of their biodegradability. High COD ratios: DB05 suggest a high concentration of carbonaceous organic compounds, not easily biodegradable, that can not be treated through biological, aerobic, conventional treatment processes, such as with activated sludge. Typical COD values for industrial untreated wastewater range from 400 to 15,000 mg / L while the corresponding DB05 values vary from 80 to 4,000 mg / L. On the other hand, the typical values of COD for municipal wastewater, untreated, vary from 400 to 800 mg / L and the BOD values vary from 150 to 400 mg / L. It is clear that the DQOzDBOs ratio of typical wastewater is well above 2: 1 which is the corresponding value for municipal wastewater and thus provides a goal or objective for the pre-t of industrial process water effluents, to allow an additional, effective treatment, through aerobic, conventional biological processes. The treated municipal effluents typically have COD values around 60 mg / L and DB05 values of 15 mg / L (COD /: DB05 =: 1).

Several physicochemical processes have been proposed for the treatment of water coming from industrial manufacturing processes, apart from conventional biological treatments. These non-biological processes for the treatment of effluents, such as filtration methods, advanced oxidation using ultraviolet light, peroxide and ozone, reverse osmosis, precipitation with ecolol polyalum, quicklime or alum, flotation with dissolved air, adsorption on carbon and others, are effective in removing dissolved and particulate contaminants from these streams, but they are often effective, either partially, being able to remove only a relatively narrow range of pollutants or are prohibitively expensive to use. in industrial processes for the treatment of water effluents, especially in processes that generate large quantities of wastewater, such as pulp and paper mills. The cost of large quantities of chemical reagents, high maintenance costs and expensive facilities, together with their often limited scope, has made these proposed solutions unattractive. Therefore, a process for water treatment has been sought, which has a high level of efficiency, which is capable of eliminating a wide spectrum of pollutants and which still requires low investment and low operating costs. EP-A-0 151 120 describes a method for the removal of heavy metals from an aqueous solution. The method comprises the co-precipitation of the heavy metal ions with a carrier precipitate which is formed in the aqueous solution. In the field of dye manufacturing, proposals have been made to purify contaminated water through the precipitation of ferric hydroxide, to "trap contaminants". Metallic iron was used in the 1950s to produce ferric hydroxide insitu as a coagulant (Dr. H. Jung, Viersen, Ein Beitrag zur Reinigung der Ab asser der Textil und Leder indus trie (Ni er s see f ahren). Verwal 3 (1952) 95; HL Bendel, Gerf Das PISTA-i sungve rf ahren zur Wasser und Abwas serreinigung 72 (1951) 231). This method was abandoned later. In Korrespondenz Abwasser 3/87, page 238 onwards, a process for the decolorization of effluents from the textile industry is described, using Fe (II) and calcium hydroxide at a pH of 9. In "LAWQ 1996, 2nd Specialized Conference on "PRETRATMENT OF INDUSTRIAL WASTEWATERS", Oct. 16-18, 1996, Athens, GREECCE, H. Chua, etc. "Decolor izat ion of textile dyeing and finishing wasterwater using electro-coagulation sequence pipe- reac tors" is done Reference is made to the sentence of coloring matter in waste water, by means of electrolytic cells with metallic iron electrodes.The mechanism of electrolysis uses electric current for the co-operation.United Patent No. 5,198,118 reports a treatment in which waste water passes through a reactor containing brass (Cu, Zn) and then through an ion exchange column, followed by reverse osmosis US Patent No. 4,548,718 describes the combined use of iron and sulfur, to treat complexes of metal cyanide and free cyanide. U.S. Patent No. 5,575,919 proposes a water treatment to remove ethers and TOC at a pH of 5 to 8.5, using sulfur-modified iron catalyst, in the presence of peroxide. U.S. Patent No. 5,411,664 describes a biological process for reducing and degrading halogenated organic compounds, in the presence of multivalent metals such as Mg, Cu, Ni and Fe. US Pat. No. 4,194,973 uses Fe (II) produced i n s i t u by the oxidation of metallic iron of a pH of 5 to 6.5 to reductively break the aryl-azo or aryl-nitro chromophores. The method also precipitates chromium. The method is applied as a pretreatment prior to biological treatment, to eliminate the color but not the organic load of the waste water. WO 96/20137 describes a method for dechlorinating a chlorinated organic compound present in an effluent, in which the effluent is contacted with a bimetallic system of iron treated with palladium. As previously mentioned, these different processes for effluent treatment are not efficient enough, and more often focus specifically on target or target contaminants, such as color, cyanide and metals, and / or are too expensive to be employed. on a commercial industrial scale.

DESCRIPTION OF THE INVENTION According to the invention there is provided a process for the treatment of waste water containing dissolved organic and / or inorganic contaminants, and / or suspended matter in the colloidal form and / or in the form of particles, which comprises the steps of (a) contacting water with iron in the form of solid metal, natural mineral containing ferrous ions and / or Fe (II), and subsequently (b) separating suspended solids from the aqueous phase, and the process is characterized in that in step (a) the waste water is contacted with iron in the presence of a promoter metal which promotes the transfer rate of electrons from the iron to the dissolved contaminants, and in step (b) the Suspended, separated solids include solids formed during step (a) and any suspended matter originally present in the waste water. In this way, a process is provided for the treatment of contaminated water, particularly one containing organic and inorganic contaminants, dissolved, that can be chemically reduced, and suspended matter in the form of particles or in the colloidal form, the process comprises putting in contact the water with metallic iron or ferrous ions (Fe2 +), or mixtures thereof, in the presence of a promoter metal, such as Cu, Pd, Pt, Au, Ag and Ni that functions as a promoter agent, for example as a catalyst, for the oxidation-reduction reductions carried out by the iron or the ferrous reagent. The process of the invention is particularly relevant for the treatment of water containing macromolecular materials that can be reduced. The promoter metal may be present in the form of a pure solid metal, such as chips, pellets and pellets, or as an insoluble metal compound, such as an oxide and sulfide, to minimize its formation of complexes with contaminants present in the metal. waste water and / or dissolution in the aqueous phase, and therefore lose it from the reactor. The promoter metals can also be deposited as a thin coating layer on the surface of the metallic iron, pretreating the latter with an aqueous solution containing appropriate concentrations of metal cations such as Cu2 + and Ag2 +. Iron can be used in the form of elemental iron, iron compounds or ores or natural minerals that contain iron. This invention provides an efficient and practical process for the treatment of waste water containing dissolved organic and inorganic contaminants, which can be treated by chemical reduction, and suspended matter in the form of particles or in the colloidal form. Examples of such wastewater include effluents from process water from tanneries, dry cleaners, fiber industries and textile industries, wood and paper industries, and water streams contaminated with oil (for example with engine oil, olive oil , etc.) . Due to the chemical structure, often complex, the high molecular weight and the oxidized nature of the dissolved pollutants present in these effluents, these currents are usually not easily treated by biological methods of wastewater treatment. On the other hand, the elimination of the commonly high charge of particulate matter, of these effluents, by filtration or sedimentation, typically requires the use of costly coagulation aids to facilitate the aggregation of small particles in large agglomerates that can then be more effectively separated from the aqueous phase a. The treatment of these effluents in accordance with the present invention results in the chemical reduction of the dissolved, complex and highly oxidized contaminants, and the simultaneous coagulation of the suspended contaminants, in the colloidal and particulate form, which are subsequently removed, from Easy way, by sedimentation or filtration without the use of additional coagulation aids. The overall result of the treatment is the production of an aqueous stream with a carbonaceous and nitrogenous charge, total, substantially lower, a concentration of suspended solids, substantially lower, and almost always a COD ratio: BOD typically lower, which suggests a higher biodegradability of the residual pollutant load. Occasionally, a stream of process water, treated by the process described herein, is of an adequate quality to be recycled and reused in the manufacturing process, without further treatment. This is particularly significant for the paper industry which uses large amounts of water and where the recycling of process water is often done using energy-intensive treatment methods, such as dissolved air flotation (FAD). However, when it is desired to perform the final disposal of the waste water stream, to a natural mass of water, additional treatment is typically required through conventional biological treatment methods. In those cases, the application of a process according to this invention, to a waste water stream, before the biological treatment or parallel to it, makes the latter more feasible, more efficient, more economical in terms of both the investment of capital as of the cost of operation and, also, the water finally discharged is compatible with environmental requirements. Without being limited to a particular theory of the operation of the invention, it is believed that the process involves an oxidation-reduction system in which metallic iron is a reducing agent that is oxidized to ferrous ions (Fe2 +) and then to ferric ions (Fe3 + ) while certain electronical sites ("electron acceptors") that are found on polluting molecules, function as electron acceptors, thus being reduced and providing a mechanism for a partial decomposition of the contaminants, by means of the simultaneous addition of hydrogen ions (H +) and electrons. It is also believed that the presence of promoter metals that are in contact with iron or ferrous ions, reduces the activation energy required for the transfer of electrons from the latter to a contaminant that can be reduced, thus accelerating the reaction rate. - - The global reaction scheme can be represented in figure form as follows: Fe2 + Fe "(2) R1R2 2e" 2H + = RiH + RH (3) where R1R2 is an organic molecule susceptible to reductive decomposition between the two groups Ri and R2 • Ferrous ions (Fe2 +) produced in excess as an intermediate product of iron oxidation, can promote further reduction of dissolved materials and, In fact, ferrous salts such as ferrous sulfate can be used in the presence of a promoter metal as an initial material for the chemical reduction of contaminants by themselves. In the method according to this invention the metallic iron is used mainly for the reductive decomposition of organic contaminants that can be reduced, in the waste water. The production of ferric ions (Fe3 +) is merely a secondary effect of the reducing action of metallic iron, but the ferric ions thus produced conveniently find use in the removal of suspended matter, in colloidal and particulate form, present in the waste water. Examples of such suspended particles include wood and paper particles, when the effluent comes from the wood processing and papermaking industries, or particulate material from other industries such as the leather industry, from materials dyes, fibers and textiles. Particularly significant is the reduction of macromolecular co-binders. The elimination of this suspended matter is carried out by a combination of the coagulation of particles, through the neutralization of charges and / or the uptake by ferrous and ferric hydroxides, insoluble, as well as insoluble hydroxides of other metals present in the waste water. which easily form at a pH of 7 to 8.5 and precipitate in the solution. As a result, unwanted metal ions, particularly unwanted heavy metal ions, can also be removed from the system as a side effect. The promoter metals that can be used in the invention are those usually identified with the term noble metal, which include silver, nickel, gold, platinum and palladium, but an important metal is copper, which although belongs to the The same group of the Periodic Table is not usually considered as "noble". Other "noble metals" for example, ruthenium, or rhodium can be used but are probably too expensive for practical use. Other metals can also promote the reaction. It can be analyzed if another metal is convenient or not by first checking that it does not adversely affect the reaction and usually the metal should not be significantly reactive. The addition of a possible metal to iron / iron ions will then indicate whether a superior result is obtained compared to the addition of iron alone. The promoter or activating metal can be included either in the form of individual particles of the individual metal or, as will be discussed later, or by depositing it on the surface or at least part of the surface of the iron, or it can be included as a compound of the invention. metal. Activating metal compounds, which can be used for the purposes of promoting iron activity, can be many of those commonly available. However, the compounds are, most preferably, insoluble compounds, particularly oxides and sulfides. A person skilled in the art will know perfectly the probability that a particular compound form, of a metal, is capable of activating iron, but if there is any doubt this can easily be verified through a simple analysis. Generally only one promoter metal will be used since two or more promoter metals in contact with one another as well as with iron, would result in the dissolution of the metals, except for the one with the lowest polarization potential. However, different promoter metals can be used in different sections of the reactor systems or even in the same reactor vessel. The proportion of the activation metal, with respect to iron, it can depend on whether the metal promoter is in the elemental form or in the form of a compound. Usually this will be measured by the ratio of metal content, measured as elemental form, to iron as it is in the system, that is, in the context of the metal compound and the ferrous compound, the ratio of metal ion to ferrous ion . The amount of metal promoter, measured as elemental metal, by weight of elemental iron, can vary from very little (catalytic amounts) up to amounts above 50% by weight of iron, including up to 1: 1. Where the compounds are in the solid form (eg, in the elemental form) a relevant factor may be the degree of contact, ie the surface area of the iron that is in contact with the promoter metal. Whichever is the upper limit, there must clearly be a significant amount of iron in the final system. As stated, the precise function of the metal promoter is not completely clear. The effect may be partially in the intensification of the reducing effect of iron and partially the intensification of the reaction of elemental iron - > ferrous - > ferric. The important point is that the presence of the promoter increases the efficiency of ferrous metals to eliminate contaminants. The treatment according to this invention involves a two-step sequence, that is, a reaction phase followed by the separation of the coagulated solid particles, which can be applied in a spatial or time sequence (continuous or batch treatment, respectively ). The removal of solid particles is carried out more often by sedimentation. However, alternative embodiments of the invention may also employ other technologies suitable for the separation of solids, such as filtration or flotation. As will be described, the process of the invention can be applied to a wide range of water streams that originate from different industrial processes also to waste water from sewage systems, etc. For example, the process of the invention can be used to treat municipal sewage, effluents from lumber or wood-based panels, from paper and pulp industries, dye treatments, fiber industries or textiles, tanneries, the production of natural or synthetic lubricants or products based on petroleum, or products of edible oils. The process of the invention may not be equally successful in the treatment of all contaminated waters, depending on the nature of the contaminant and physical form. Also, the ratio of the promoter metal to iron can affect the particular success of one of these systems. However, in general, the system of the invention will be more successful in the treatment of waste or contaminated water than, for example, than the use of ferrous or metallic iron by themselves. Clearly, for any particular wastewater it may be necessary to perform a simple analysis to determine the most successful conditions for it to achieve the best possible decontamination. In the case that the waste water may contain suspended inert matter, in the colloidal or particle form, this can also be eliminated by carrying out the operation of the process together with the particular material that results from the effective chemical reduction by the process of the invention. Due to the chemical nature of the treatment in this invention, the set of operating conditions employed, such as the pH during the reaction and the solid separation steps, operating temperature and the duration of the reaction and the separation steps of solids, can have a significant effect on the overall efficiency of the treatment. In fact, the working parameters used would have to be adjusted for the particular effluent that is being treated. The pH used during the reaction step can vary from highly acidic to highly alkaline, for example from 4 to 11, depending on the nature of the waste water stream being treated. A pH of 9 for the current reduction can be particularly useful. However, during the solid separation stage, a pH between 7 and 8.5 should preferably be applied, where it is known that the iron exhibits the lowest solubility in the aqueous phase, during the separation phase of solids. The contact times for the reaction and for the removal of solids depend on the precise nature and concentration of dissolved and suspended contaminants in the incoming wastewater. Contact times between 1 and 180 minutes have been used during the reaction stage, and the average contact time is 4 to 20 minutes. The retention times used for the subsequent separation of solids can vary between 5 and 180 minutes, depending on the actual technology used. In the specific embodiment of this invention, where sedimentation is employed, the separation technology of solids, the typical sedimentation times, employed, are between 20 and 60 minutes. The working temperature affects the kinetics of the different chemical reactions, the solubility of the species, the speciation of iron and other metals in solution and the kinetics of the coagulation and separation of solid particles, and is mainly determined by the temperature of the incoming waste water stream. Working temperatures between 2 and 80 ° C have been successfully used. Although it is desirable to exclude oxygen from the reactor, to the extent possible, to ensure that metallic iron and ferrous ions are used completely for the reduction of dissolved contaminants that can be reduced, it is not necessary to take special measures to exclude totally oxygen, since any of those measures would greatly increase the cost of the treatment process. Although for certain applications, such as the processing water treatment of papermaking, before its recycling, the process of this invention may be sufficient as a single treatment, in most applications and, certainly in those where the waste water stream is going to be discarded in a natural stream or mass of water, the treatment through biological, aerobic and anaerobic, conventional methods, is the one most likely to be required subsequently (either on-site or off-site). same in a nearby facility for the treatment of municipal sewage) or in parallel to the process of this invention. In the typical embodiment of the invention, the process of this invention is applied for the pre-treatment of a waste water stream, before the biological treatment. The exact implementation of the treatment, in terms of the mode of operation or work (continuous or batch flow) and the configuration of the system, depends on the nature of the incoming wastewater and the objectives of the pret ra t ami ent. In general, there are a multitude of system configurations that can be applied. The invention will now be illustrated with reference to the accompanying drawings in which Figure 1 presents a schematic illustration of a continuous flow plant, in accordance with a preferred embodiment of the invention, for the pretreatment of waste water, before the biological treatment Figure 2 presents a diagrammatic illustration of the effect of a treatment according to the invention, in the Speed of Oxygen uptake (VCO) (Comparative example ) . The waste water which is to be treated in accordance with the present invention can originate from different sources in an industrial manufacturing process. The combination of partial waste water streams is generally carried out in equalization tanks where the circulation of the water ensures complete mixing. The pH of the waste water after the leveling step is generally between 8 and 10. In the particular treatment mode, shown in Figure 1, the water A from an equalization tank (not shown) is directed towards a sequence of 4 tanks 10, 11, 12, 13 consisting of two reactors 10 and 12 each followed by a settling tank 11 and 13, for the separation of the coagulated solids in the preceding reactor, by sedimentation. To simplify the following discussion, reference will be made to the sequence of the first reactor reactor 10, 11 as the primary treatment stage or stage 1, while to the second 12, 13 as to the main treatment stage or stage 2 As shown in Figure 1, the main reactor 12 in stage 2 involves a fixed bed tower with metallic iron. The feed is first directed to a primary reactor 10 (Step 1) where it is contacted with ferric and ferrous ions recycled from the bottom of the final clarifier 13 in Step 2 and with the promoter (usually in the elemental metal form) in a solid form, which is preloaded in the tank. The incorporation, in the treatment sequence, of a primary reaction stage where the fresh waste water is brought into contact, in the presence of a promoter metal, with ferrous and ferric ions recycled from the main reactor 12 (Stage 2) allows the initiation of reducing reactions that lead to the chemical softening of incoming contaminants that can be reduced, to the coagulation and elimination of colloidal and particulate matter, suspended, in fresh wastewater, and to the elimination of certain Inorganic contaminants, such as hydrogen sulphide and phosphate, which can react with ferrous or ferric ions, form insoluble compounds and are removed by sedimentation in clarifier 11 in Step 1. In this way, the configuration of the given system avoids unnecessary loss of the ferrous and ferric ions produced in the main reactor 12 (Stage 2) and, thus, make full use of the capacity reducing and coagulating the metallic iron supplied in Stage 2 which is then predominantly used for the reductive decomposition of the reducible organic contaminants which enter the main reactor instead of being partially lost in secondary reactions and in the coagulation of matter in the form of particles, which can often be of secondary importance. The outlet of the primary reaction tank 10 is directed to the first clarifier 11 where the largest fraction of the coagulated solids is sedimented and removed from the system in the form of sludge while the clear, liquid supernatant is decanted in the main reactor. (Stage 2) . The main contact of the pollutants with the iron / promoter mixture takes place in the fixed bed tower, in the main reactor 12 (Stage 2). The fixed bed contains metallic iron particles in the form of chips, pieces, pills or other types of pellets. The use of that waste material, iron, minimizes the cost of the water treatment process. However, the iron particles should be relatively pure. Also, appropriate amounts of the promoter are in contact with the metallic iron in the bed, in such a way that they are elastically distributed evenly throughout the bed. The liquor from the main reactor is pumped continuously through the iron bed to achieve contact of the contaminants with the iron / catcher mixture. The bed is designed in such a way as to ensure good contact and a sufficiently large interface between the iron bed and the aqueous phase, to achieve high proportions of iron electron flux to the contaminants that can be reduced. The water that leaves the tower contains, among other reaction products, ferrous and ferrous ions as well as small amounts of unreacted metallic iron and solid particles of the promoter that are separated from the bed due to friction and that are washed and expelled from tower. These iron species that have reacted partially or that have not reacted at all can - in turn promote reactions of reduction of contaminants in the liquid mass. As a result of its reactive dissolution in the tower, the metallic iron needs to be replenished or supplied at regular intervals of time, for example from the seed tanks 14 and 15. The outlet of the main reactor 12 is directed towards the final clarifier 13 in wherein the suspended coagulated solids, and the insoluble hydroxides, are sedimented and recycled to the primary reactor 11 (Stage 1) while the clear supernatant stream 13 is directed to the subsequent biological treatment. Despite the different operating advantages of the treatment configuration shown schematically in Figure 1, this is only one possible implementation of the process of this invention. Stage 2 shown in Figure 1, which consists of the main reactor followed by sedimentation, can also be used to simplify the engineering of the system. Additional specific embodiments of the invention may involve the use of a single or multiple fixed-bed towers with iron / pestle-recycling the liquor from the equalizing tank, or the use of a cascade of those towers, in series, followed of a single clarifier. Other process configurations can -involve the use of alternative technologies for the removal of particles, such as filtration, flotation, etc., and combinations thereof. Finally, the process of the invention can also be applied in a cyclic batch manner where the waste water is periodically fed to the reactor tank and subjected to a chemical treatment achieved by the recirculation of liquor through the tower, certain period of time. At the end of the reaction stage, the pumping of the liquor to the tower is stopped and the sedimentation of the solids in the same tank is allowed, for a certain period of time, after which the sludge is removed from the tank bottom and the clear supernatant of the upper part, thus ending a complete cycle. In a specific, additional embodiment of the invention, the process can be applied in parallel to conventional biological treatment methods, in the same unit. As in the application of p retra t ami or separate before biological treatment, which was discussed at the beginning, there are a multitude of possible system configurations, depending on the nature of the incoming waste water and the treatment objectives. In a specific embodiment of this invention, the fixed bed may contain, in addition to the iron and the promoter, an appropriate packaging material, with a sufficient surface area, which can provide a substrate for the fixation and growth of microbial biological films. The functioning of the system under anaerobic conditions will promote the growth of anaerobic microbial cultures capable of reducing complex and oxidized contaminants, thus taking advantage of the simultaneous, chemical, and biological reducing mechanisms that work in the same unit. The operation of this tower under aerobic conditions will promote the growth of aerobic microbial cultures and, thus, allows a simultaneous, reductive decomposition of the pollutants, by the iron / promoter system and the biological oxidation of the resulting pollutants, which are more easily biodegradable, in the same unit. In a specific, additional embodiment of this invention, where activated charcoal or other porous adsorbents are used, as a microbial support medium, complex contaminants such as lignin and cellulose will tend to be adsorbed on the adsorbent surface and will be thus retained in the tower for prolonged periods of time, resulting in prolonged contact with the iron / promoter mixture and with the microbial culture, allowing a more complete degradation, possibly up to final oxidation products such as CO2 and water. A further specific embodiment of this invention, for the chemical and biological degradation, simultaneously, of the contaminants present in a waste water stream, is the use of a fixed bed tower with iron / promoter, to treat by recycling , liquor from a certain stage in a conventional biological treatment sequence such as denitrification or tanks with activated l two. The invention will now be illustrated in a series of examples. Based on the points illustrated in them, these examples can be grouped into four different classes: I. Comparison with the results of the relevant prior art II. Possibility of treatment for different types of industrial wastewater III. Possibility of the process under a range of working conditions IV. Implement ation of the process to intensify the biological treatment for the current or downstream.

A summary of the Examples discussed below is shown in the following Table: I. Comparison with the results of the prior art This class of Examples illustrates that the incorporation of a promoter metal catalyst, in a solid metal form or an insoluble compound containing it, in standard water purification technologies, widely used, in which ferrous salts are used ( Fe2 +) for reduction / coagulation, and where ferric salts (Fe3 +) are used only for coagulation, improves the efficiency of the process both in terms of the elimination of the COD and the biodegradability of the waste water treated. The results of the treatment are also compared to those obtained using only metallic iron which, however, in the art is not used as a standard method of generic water purification, but only for the reductive degradation of the specific contaminants, so that can be subsequently removed by biological pesticide oxidation.

EXAMPLE 1 The effluent of process water from a paper mill, after the standard primary treatment by filtration on a drum filter, has a COD of 1,500 mg / L. A sample of this waste water stream was treated in accordance with the present invention, as described below: Samples of 200 mL of this waste water were placed in three identical containers and different amounts of an amount were added to each container. ferrous salt (Fe2 +) and metallic copper shavings (see the Table of results below). The containers were covered and shaken for 5 minutes. Subsequently, the pH of the solution in each container was adjusted to 8.5, and the treated samples were allowed to stand for 20 minutes, with which the sedimentation occurred. E J. Analysis of the supernatant layer of each treated sample yielded the following results: From Example 1 it is evident that a conformance treatment according to this invention, in which a mixture of ferrous and metallic copper ions (Container No. 2) is used, results in a substantially greater removal of the COD from the Original waste water, when using only ferrous ions or metallic copper (Containers No. 1 and 3).

EXAMPLE 2 The effluent of water - from a process from a newspaper factory that uses 100% recycled paper as initial material, has, after being filtered in a drum filter, a cloudy gray color, a strong odor and a COD of 1, 650 mg / L. A sample of this waste water stream was treated in accordance with the present invention and with metallic iron only as described below: The pH of this waste water was first adjusted to 5.5. Subsequently, 200 mL samples were placed in four identical closed containers, each of which contained 200 g of iron chips together with a different metal promoter or metal sulfide, selected from the Cu, CuS, Ag, and Ni group. An additional sample of 200 L was placed in an identical fifth container containing only 200 g of iron shavings. The five containers were covered and shaken for 20 minutes after which the pH of the solution found in each of the containers was adjusted to 8.5, and the treated samples were allowed to stand for 20 minutes, which occurred the sedimentation At the end of the sedimentation period, the supernatant layer in all the samples was odorless, transparent and almost colorless. The following efficiencies in the elimination of COD were achieved in each vessel: As shown, the addition to the reactor of a promoter metal according to this invention (Containers No. 1-4) always results in a higher efficiency in the elimination of the COD compared to that obtained only with the use of metallic iron (Container No. 5). The increase with the current treatment, produced by the addition of the promoter, varies from the marginal for Ni (Container No. 4) to the substantial for Cu and CuS (Container No. 1-2). Thus, the nature of the promoter employed is also important. It should also be noted that the use of Cu as pure metal (Container No. 1) and as a sulfide (Container No. 2) produced identical results. However, CuS is more insoluble in water and more resistant to the effects of solubilization and complex formation, by the contaminants present in the waste water.

EXAMPLES 3 The combined effluent from a factory that produces wood-based panels (plywood, board made of wood particles, wood in rolls, etc.) is a very dark red-colored solution with a COD of 14,480 mg / L. Samples of this effluent were treated with a process according to this invention as well as with standard treatment methods based on the prior art.

EXAMPLE 3.1 First the pH of the wastewater was adjusted to 9.5 and then 200 mL samples were placed in a vessel containing 200 g of iron shavings together with 100 g of Cu chips. The container was capped and stirred for 5 minutes, after which the pH of the solution was adjusted to 8.5 and the treated sample was allowed to stand for 20 minutes to allow settling of solid particles. At the end of the sedimentation period, the supernatant solution had a COD of 3,100 mg / L for a 79% removal compared to that of the crude sample.

COMPARATIVE EXAMPLE 3.2 The pH of the waste water was adjusted to 9.5 and samples of 200 mL were placed in three containers identical to those of Example 3.1 but without metallic iron or copper. 90 mg / L of FeCl3 were added to the first container, 90 mg / L of FeS04 in the second and 100 g of metallic iron chips to the third. The containers were closed and agitated for five minutes after which the pH of the solution was adjusted to 8.5 and the solids in the treated samples were allowed to settle for 20 minutes. At the end of the sedimentation period, the supernatant solution of the three vessels had the following COD values: Comparing the results obtained in Examples 3.1 and 3.2 it is clear that a process according to this invention produces a significantly higher COD removal of the original waste water than when iron is used in any of its standard forms by the reduction and / or coagulation in the absence of the promoter. Furthermore, it becomes evident, from the Oxygen Capture Rates (VCO) measurements for each sample separately, that the sample that was treated in the presence of a promoter exhibited a much more intense biological activity than those treated in the absence of the promoter, indicating a higher concentration of easily biodegradable contaminants in the preceding ones (see Example 5). This is of great importance for the subsequent treatment of waste water through standard biological methods before disposal or final discharge, since the pretreatment of the sample, in accordance with this invention, will not only require biological treatment plants. but girls will also allow the easier assimilation of the residual contaminants by the biomass and, in this way, a higher quality of the current finally discharged.

EXAMPLE 4 It was treated, in accordance with the present invention, a mixed sample, waste from a paper mill, with the following characteristics: COD 1,500 mg / L BOD 475 mg / L COD: BOD 3.1: 1 EXAMPLE 4.1 The pH of this sample was adjusted to 10.5. The sample was introduced to a 7 m3 tank, in a fixed 160 L tower that contained 50 kg of iron chips mixed with 15 kg of copper chips and the waste water was recycled through the tower or He used a contact time of approximately 25 minutes. The sample was then aerated (contact time) for approximately 25 minutes, until the color of the solution turned brown due to Fe3 + formation. The solution was allowed to settle, with which the sedimentation occurred. The upper phase was colorless and odorless transparent, and possessed the following characteristics: COD 470 mg / L (69% elimination) BOD 160 mg / L (67% elimination) COD: BOD 3: 1 COMPARATIVE EXAMPLE 4.2 An amount of 250 mL of the brown, odorless, raw waste water sample was adjusted to a pH of 10.5. 90 mg / L FeS04 were then added to this sample. The mixture was stirred for 25 minutes and then aerated for an additional 25 minutes with air. Then the mixture was left to settle, with which the sedimentation occurred, and then the upper phase was brought together. The resulting characteristics of the upper phase are as follows: COD 1,133 mg / L (25% elimination) BOD 130 mg / L (73% elimination) COD: BOD 8.7: 1 This upper phase also had a yellow color.

From this Example it is obvious that, when compared against the application of Fe (II), which is the most widely used form of iron, in the purification of water, and which is capable of both reduction and coagulation, the method according to the invention, produced a greater elimination of the COD but lower efficiencies in the elimination of the BOD. This indicates that it has eliminated, either fewer biodegradable organic components than the preceding one, or that has chemically transformed a large fraction of the non-biodegradable COD present in the original waste water into biodegradable organic components. In any case, since both methods are used as a prerequisite of biological treatment, the sample treated in accordance with this invention will not only have a lower global charge of carbonaceous organic pollutants (COD) but will also contain a larger fraction. of biodegradable organic components (lower COD: BOD ratio) before proceeding with biological treatment, than the sample treated through the standard method, using Fe salts (11). This in turn translates into smaller biological treatment plants and a more effective functioning of the biomass found in them.

EXAMPLE 5 A mixed sample of waste from a plant for the manufacture of panels based on wood, is dark brown, odoriferous and has the following characteristics: COD 14,480 mg / L BOD 4,530 mg / L and it was treated in accordance with the present invention: EXAMPLE 5.1 The pH of this sample was adjusted to 10.5. The sample was placed in a closed vessel containing 200 g of iron shavings mixed with 100 g of copper shavings and stirred for 25 minutes. The sample was then aerated for 25 minutes and allowed to settle, resulting in sedimentation. This upper phase was colorless, transparent and odorless.

COMPARATIVE EXAMPLE 5.2 Quantities of 250 mL of an odoriferous, dark brown sample were adjusted to a pH of 10.5 and placed in two empty containers identical to those in Example 5.1 that did not contain iron or copper. An amount of 45 mg / L of FeS04 was added to the first container and 45 mg / L of FeCl3 to the second. The solution that was found was the two vessels stirred for 25 minutes, then mixed for an additional 25 minutes with air and finally allowed to stand for 20 minutes, resulting in sedimentation, and the supernatant layer, in the two containers, it was collected. The same number of samples, treated in Examples, 5.1 (i.e., by a mixture of Fe / Cu) and 5.2 (i.e., either only with Fe 'with Fe .3+ were added to three containers (a sample pretreated differently in each container) each of which contained 20 mL of municipal waste water, precl. municipal, local wastewater treatment plant, with a culture of biologically active microorganisms. A fourth vessel containing only 200 mL of the municipal, preciated sewage was used as a standard or standard for the experiment. Four additional containers were not added to the four containers, so that the biomass found in each sample could grow by consuming only the contaminants present in the municipal wastewater as well as in the three samples of industrial water, pretreated, added. The experiment was carried out over a period of 4 days during which the respiration rate of the biomass, in each reactor, was determined every day, using standard techniques that measured the Oxygen Capture Rate (VCO) by the microorganisms that They grew in each sample. The method consists of oxygenate the liquid phase found in each reactor, up to a predetermined level of dissolved oxygen (DO) (approximately 6 mg / L) and then verify the DO consumption as a consequence of the biological activity in the aqueous phase s ~ a, through time. The VCO "Oxygen Uptake Speed" is then calculated as follows: VCO [mg of OD / (mg of M / Q * h)] = Consumption of OXYGEN [mg of OD / L] Time [h] x concentration (mg / L) of the microorganism (M / O) The results of these measurements are illustrated in Figure 2 which illustrates the effect of the pre-test for the VCO. The curve corresponds to the parameter VCO obtained for waste water treated in accordance with the present invention (Example 5.1) while Curves Ib and show the VCO parameter achieved for the sample treated through conventional treatment with Fe (II) and Fe (III), respectively, for reduction / coagulation (Comparative Example 5.2). Finally, the shaded area corresponds to the VCO parameter measured for the municipal mud activated only on the target. It is easily observed that the VCO obtained after the treatment according to the present invention, which includes the reductive decomposition with metallic iron in the presence of a catalyst and the precipitation with Fe (III) produced insitu is greater than for the waste water treated only with Fe (11) or Fe (III). Clearly, the treatment of the waste water, in accordance with the process of the invention, results in a greater activation of the microorganisms. This is a reflection of the nutrient that was most readily available to the microorganisms, as a result of the preceding chemical degradation (reductive decomposition) of the macromolecular waste material.

II. Possibility of treatment for different types of waste water This group of Examples demonstrates that a process according to the present invention can be used as a general treatment technology for the removal of a broad spectrum of organic and inorganic, dissolved and suspended contaminants (some of which, such as organic compounds). halogenated, dyes, etc., are too complex in structure or are too oxidized to degrade easily through the standard aerobic biological treatment technologies) of a range of industrial wastewater of different origin.

EXAMPLE 6 Amounts of 200 mL of wastewater from various sources were added to identical containers containing, each, 200 g of iron shavings mixed with 100 g of copper shavings. The containers were closed and shaken for 5 minutes after which the pH of the solution in each container was adjusted to a value of 8, and the treated samples were allowed to stand for 20 minutes whereupon sedimentation occurred. At the end of the sedimentation period, the supernatant layer of three samples was analyzed, producing the results discussed in the following examples.

EXAMPLE 6.1 Effluent of raw process water from a newspaper factory that uses 100% recycled paper as an initial material.

EXAMPLE 6.2 Effluent of raw process water from the manufacture of wood products.

EXAMPLE 6.3 Washes from a gas station contaminated with engine oil, synthetic and petroleum derived.

EXAMPLE 6.4 Effluent from a wool cleaners EXAMPLE 6.5 Effluent process, crude, from a dairy processing plant.

For comparison purposes it is important to note that the application, in the particular crude process effluent, of Fe (II) which is the most commonly used form of iron for both reduction and coagulation purposes, had no effect on the absolute, in terms of the precipitation of fats and proteins from the aqueous phase. Rather, the process of this invention was able to produce a substantial precipitation of proteins and fats, which is evident by the large decrease in suspended solids, after the treatment.

EXAMPLE 6.6 Combined effluent, to a municipal wastewater treatment plant.

As demonstrated collectively in Examples 6.1-6.6, through the simultaneous action of a complex network of chemical reactions and physical mechanisms, such as sedimentation, a process according to the invention is capable of removing a broad spectrum of dissolved and suspended carbonaceous contaminants from the aqueous phase, such as Indicates the substantial decrease in COD after treatment (Examples 6.1-6.3 and 6-5-6-6), increasing the fraction of easily biodegradable organic carbonaceous compounds, as suggested by the COD: significantly lower BOD ratio, after the treatment (Examples 6.1, 6.3, 6.5, 6.6), removing the suspended solids (Examples 6.1-6.6), color (Ex ep 6.1, 6.2, 6.4, 6.6), odor (Examples 6.1), halogenated organic compounds (AOX) ( Example 6.2), nitrite and nitrate (Examples 6.1, 6.5, 6, 6) and phosphate (E j e p 6.1, 6.2, 6.3, 6.5 and 6.6). Of particular importance is the high efficiency of the process to remove all previous contaminants, many of which are quite difficult to remove, thus requiring special treatment (eg color, AOX, nitrite and nitrate, phosphate, etc.). In addition, the process is able to eliminate phenols with high efficiency (50-90%), which are quite difficult to treat at room temperature through biological methods due to their toxicity to most microorganisms and therefore are regulated quite strictly in most areas around the world.

EXAMPLE 7 The effluent from process waters, combined, from a newspaper mill using 100% recycled paper as an initial material, after primary treatment by filtration in a standard drum filter, has been treated additionally by a process according to this invention at three different pH values during the reaction step. Three 200-mL samples of the waste water were placed in identical containers, each containing 200 g of iron shavings mixed with 100 g of copper shavings. The pH in the first container was adjusted to 5.5, in the second to 7 and in the third to 10.5. The three containers were capped and agitated for 5 minutes after which the pH of the solution in each of the containers was adjusted to 8 and the treated samples were allowed to stand for 20 minutes, whereupon sedimentation occurred. At the end of the sedimentation period, the supernatant layer of the three samples was analyzed, producing the following results: As is evident, regardless of the pH value employed during the reaction phase, the treatment in accordance with this invention is capable of eliminating a substantial fraction of COD, BOD and color present in untreated wastewater and decreasing the COD ratio. : BOD, in other words, is able to increase the fraction of easily biodegradable pollutants found in wastewater. In fact, the observed treatment efficiencies are unexpectedly high considering that the initial sample used was pretreated by drum filter filtration which had already eliminated the largest fraction of the suspended solids present in the crude effluent, which greatly contributes to the measured COD value (suspended solids in the crude effluent = 1450 mg / L and after filtration in a drum filter = 260 mg / L). Thus, in this particular example, the process of this invention has acted mainly on the pollutants released.

EXAMPLE 8 The process water effluent from a medium density agglomerate (ADM) manufacturing plant (COD = 12.710 mg / L) was treated by a process according to this invention, using three different contact times during the stage of reaction . Three 200 mL samples of the given waste water were placed in identical containers, each of which contained 200 g of iron shavings mixed with 100 g of copper shavings. The three containers were covered and shaken, the first for 5 minutes, the second for 25 minutes and the third for 1.5 hours. At the end of the contact period, the pH of the solution in the containers was adjusted to 8 and the treated samples were allowed to stand for 20 minutes to allow the separation of solids by sedimentation. At the end of the sedimentation period, the supernatant layer of the three samples was analyzed, producing the following results: As it becomes clear, from the previous results, the efficiency of the treatment increases, as expected, with the contact time used in the reaction phase. However, COD elimination efficiencies greater than 50% are obtained even with very short contact times which is, in fact, surprising, considering that the contact times used for the reduction and / or coagulation by iron in its form metal or ionic, in the absence of a metal promoter, are typically in the order of hours or days. This is of great importance for the engineering of applications in industrial scale since the process can be implemented in configurations of smaller plants and much more versatile.

EXAMPLE 9 The raw effluent from a newspaper mill using 100% recycled paper as an initial material (COD = 2,890 mg / L) was treated by a process according to this invention, using three different iron ratios: i zador, during the reaction stage. The pH of the waste water was first adjusted to 10.5. Subsequently three samples of 200 mL were placed in identical containers each containing 200 g of iron chips, mixed with a different amount of copper chips, such that the ratio of Fe: Cu was 1.3: 1 p. / p in the first container, 2: 1 p / p in the second and 4.1 in the third. Then the three containers were covered and stirred for 5 minutes. At the end of the contact period, the pH of the solution in the containers was adjusted to 8 and the treated samples were allowed to stand for 20 minutes to allow the separation of solids by sedimentation. At the end of the sedimentation period, the supernatant layer of the three samples was analyzed, producing the following results: As it becomes clear, from the previous results, regardless of the relationship of the hero: promoter, used during the reaction, the efficiency of elimination of COD observed, at the end of the treatment - the same. Thus, the efficiency of the treatment is not limited by the relationship of hero: promoter, employed, which, in fact, supports the theory regarding the promoter, that is, the catalytic function of the promoter metal in the system.

I: Implementation of the process to intensify biological treatment in parallel or current downstream This class of examples demonstrates the use of the proposed treatment in conjunction with aerobic biological degradation, downstream or in parallel, and discusses the advantages of implementing a combination thereof for the total treatment of industrial wastewaters or of different origin.

EXAMPLE 10 The plant for the treatment of effluents, in a plant for the processing of food that manufactures, among others, several dairy products, consists of an equalization tank followed by the conventional biological treatment carried out in a line with activated sludge consisting of a 85 m3 aeration tank, followed by a sedimentation tank of 15 m3. The treatment plant has worked at its maximum capacity of 10 m3 / day for several years, with an average quality of incoming wastewater from COD = 3,800 mg / L BOD = 1, 430 mg / L producing an average quality of effluent from COD = 65 mg / L BOD = 50 mg / L.

A recent increase in the production of the plant resulted in double the waste water flow directed to the effluent treatment plant, up to 20 m3 / day. Since the plant was designed far below for the new workflow, the quality of the wastewater treated deteriorated substantially and, indeed, the treatment could no longer comply with the permitted limits for local effluents, for disposal in a neighbor river. To solve the problem, a process according to this invention was reconverted or readjusted in the existing treatment plant to provide a pretreatment of the incoming wastewater before the biological treatment. The pre-treatment was achieved by installing a 1.5 m3 tower that contained a mixture of iron and copper shavings after the equalization tank and recycling the last liquor to the tower at a rate of 6 m3 / h. The effluent from the equalization tank was sent to a sedimentation tank to separate the solids produced and the clarified stream was then fed to the existing biological treatment stage. The application of this wastewater pretreatment resulted in the elimination of 60% of the incoming COD load before the biological treatment stage, and the final quality of the effluent produced by the plant was: COD = 50 mg / L BOD = 40 mg / L which was once again below the permitted limits for the effluents and, surprisingly, slightly better than the quality previously achieved with half the flow of the influent.

In conclusion, the reconversion of a process according to this invention, in a plant for the treatment of effluents that is working poorly, to provide a chemical pretreatment before the biological treatment, allowed to duplicate the flow of waste water that entered to the plant, and at the same time, allowed to produce a quality of treated effluent, similar, and, in fact, something better, without resorting to extensions, more expensive and occupying space, of the existing biological treatment stage. In this particular embodiment on an industrial scale, of this invention, the configuration of the process consisted solely of a reactor followed by a settling tank, that is, only Stage 2 of Figure 1, where the reaction tank was replaced by the existing equalization tank of the plant. - It should be noted that the particular waste water, treated in this Example, is the one discussed above under Example 6.5, and the difference between the two Examples is the scale of the applications, the former being a working table scale (Example 6.5) and the other an actual industrial scale (present example). In comparison with the successful application of this invention, the application of the standard treatment, with Fe (II) in the particular application for the treatment of waste water, had a negligible effect on the suspended solids which contained mainly protein and fat conglomerates. , in suspension.

EXAMPLE 11 Instead of being used as a pretreatment prior to biological treatment, this invention can be used, at some point, within an existing biological treatment line, to provide a chemical sidestream parallel to biological degradation. In a series of pilot plant studies, with continuous flow, the process water effluent from a plywood manufacturing plant and boards made of wood particles, after primary clarification by sedimentation, was treated in a line of completely conventional biological treatment consisting of denitrification, activated sludge / cyclization, or tri fi cation and, finally, filtration in sand, where an anaerobic denitrifying culture had been allowed to grow. The same studies were repeated under identical working conditions after installing a torore containing a mixture of iron and copper shavings inside the denitrification tank and the liquor that was in the tank was continuously recycled through the tower, to provide simultaneous chemical and biological treatment. The quality of the final effluent that comes out of the sand filter, with and without the chemical treatment tower present in the denitrification stage, is compared to that of the influent stream, in the following Table: It is evident, from these results, that the incorporation of a process according to this invention, in an existing conventional treatment plant, to provide the simultaneous chemical and biological degradation, of the contaminants present in the waste water. incoming, results in a significant improvement in the final effluent quality produced by the plant. In particular, the elimination of phenols and NH4_N, which are strictly regulated pollutants and on which the greatest attention is placed, which commonly requires special treatment, is overwhelmingly superior when incorporating this invention into a conventional biological treatment method, than using the last one alone. In this particular embodiment of this invention, the configuration of the implemented process was the simplest possible, consisting only of one reaction tower. The trip tank served as the reaction tank. further, because the influent waste water stream was preclarified by classical primary sedimentation, the additional non-biological mud load, produced by the incorporation of the chemical treatment into the biological treatment sequence, was marginal compared to the biological sludge in the system , thus not requiring the incorporation of an additional clarifier in the existing treatment sequence.

EXAMPLE 12 Papermaking involves the use of extremely large amounts of water, which typically vary from 40 to 75,000 m3 / day. The fresh water used in the production is typically taken from rivers or nearby lakes that, at the same time, also receive the effluent from process water coming from the production lines of the same plants. As a result, recycling process water after an intermediate treatment becomes of paramount importance to this industry, in order to minimize the operating costs associated with the supply of fresh water and at the same time alleviate the contamination of those bodies of water which serve as sources of fresh water for their production. Water treatment for this purpose of recycling, typically involves expensive treatment technologies such as reverse osmosis and adsorption. A 200 L sample of the raw process water effluent from a newspaper mill using 100% recycled paper as an initial material was allowed to stand for several hours to achieve primary clarification by sedimentation of the solids. The sample was then fed at a rate of 0.5 L / ha to a pretreatment in accordance with this invention, in a configuration identical to that shown in Figure 1 and then to a conventional biological treatment line involving denitrification, activated sludge. This was achieved through the creation of a trialling, trialling, and finally, sand filtration, where a denitrifying, anaerobic culture had been allowed to grow. Each of the four tanks (two reactors and two sedimentation tanks) shown in Figure 1 had a volume of 4 L, while the tower that was in the main reaction tank was 1 L and contained approximately 600 g. of iron shavings mixed with 200 g of copper shavings. The results of the complete treatment, obtained, are shown in the following Table: As is evident, the implementation of a pretreatment in accordance with this invention, in a conventional effluent treatment plant (primary clarification followed by secondary treatment) between the primary clarifier and the secondary biological treatment, allows the system to produce a water Extremely high quality effluent, which can really be recycled to the production process. In this way, final effluent refining techniques, which expend a lot of energy and are generally more expensive, are not usually required to allow the recycling of the water effluent from the biological treatment stage.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (10)

1. A process for the treatment of waste water containing dissolved organic and / or inorganic contaminants and / or suspended matter in the colloidal and / or particulate form, comprising the steps of (a) contacting water with iron in the solid metal form, ferrous ions and / or natural mineral containing Fe (II), and subsequently (b) separating the suspended solids, from the aqueous phase, the process is characterized in that in step (a) the waste water it is contacted with iron in the presence of a metal promoter which promotes the electron transfer rate of the iron to the dissolved contaminants and in step (b) the suspended solids, separated, include solids formed during step (a) and any suspended matter originally present in the waste water.

2. A process according to claim 1, characterized in that the solid metallic iron is in the form of chips, cuttings, filings, pieces, dust, pills, pellets or any other form of particulate, porous or non-porous iron, of regular or irregular form.

3. A process according to claim 1 or claim 2, characterized in that the metal promoter is one of copper, silver, nickel, gold, platinum or palladium.

4. A process according to any of claims 1 to 3, characterized in that the metal promoter is used in the form of metal, in the form of particles, in contact with iron or with ferrous ions, or as a metal layer deposited on the surface of metallic iron.

5. A process according to any of claims 1 to 4, characterized in that the metal promoter is used in the form of a sulfide, oxide or other insoluble compound containing the promoter metal element.

6. A process according to any one of claims 1 to 5, characterized in that a stream of waste water undergoes a pretreatment with ferrous and / or ferric ions in the presence of a promoter metal, before contacting with it. metallic iron in the presence of a metal promoter.

7. A process according to claim 6, characterized in that the ferrous and / or ferric ions are derived from the effluent of the reaction with the elemental iron in the presence of a promoter metal.

8. A process according to any of claims 1 to 7, characterized in that the water is municipal sewage.

9. A process according to any of the rei indications from 1 to 7, characterized because the water comes from paper and pulp industries, industries of wood or wood based panels, dry cleaning treatments, fiber industries and textile industries, tanneries, production of natural or synthetic lubricants or industries based on petroleum, or edible oil production plants.

10. A process in accordance with the rei indication 1, characterized in that the waste water contains macromolecular materials that can be reduced and brought into contact with iron in the presence of a promoter metal that is in the elemental form or a compound . SUMMARY OF THE INVENTION The present invention relates to a process for the treatment of waste waters containing dissolved organic and inorganic contaminants, which can be chemically reduced, and suspended matter in the form of particles or in the colloidal form. The process comprises contacting the water with metallic iron or ferrous ions (Fe2 +), or mixtures thereof, in the presence of promoter metals, such as Cu, Pd, Pt, Au, Ag, and Ni, or oxides, sulfides and other insoluble compounds of these metals, which catalyze the oxidation-reduction reactions carried out by iron or ferrous reagents. The production of ferric ions (Fe3 +) as a final product of the oxidation of iron allows the simultaneous coagulation and precipitation of suspended solids in colloidal form and particles, in the aqueous phase. In addition to maintaining the scheme of reducing reactions, the system carries out a multitude of secondary reactions involving the ferrous and ferric ions produced i n s i t u w which allows the simultaneous elimination of specific target pollutants such as phosphate and hydrogen sulfide. The net effect of a treatment in accordance with this invention is the reduction of a wide range of carbonaceous, nitrogenous and other target contaminants, present in a waste water stream, which are in the dissolved, colloidal or particulate form, and the chemical conversion, which is commonly referred to as "softening", of contaminants that are not easily biodegradable, through a set of reactions and physical processes, generally complex. As a result, the implementation of the process before, or in parallel with, the conventional biological treatment, makes the latter more possible, more efficient, and more economical in terms of capital investment and operating costs, and also, the water finally discharged It is more compatible with environmental demands.