WO1997047561A1

WO1997047561A1 - Biological process for purifying liquid residues with high contaminating content and/or high toxicity, particularly liquid manures and dregs of oil

Info

Publication number: WO1997047561A1
Application number: PCT/ES1997/000146
Authority: WO
Inventors: Joan Vila Reyes
Original assignee: Bio Specific Systems, S.L.
Priority date: 1996-06-12
Filing date: 1997-06-06
Publication date: 1997-12-18
Also published as: ES2108658B1; ES2108658A1

Abstract

The purification is carried out through bacteria adapted to the residue externally to the reactors involved in the process, said bacteria being fixed to support means which are immersed in the reactors. The process comprises first and second preliminar physical treatments, a physical-chemical treatment, a treatment in at least one aerobic biological reactor, a treatment in at least one anoxic biological reactor arranged upstream of the first aerobic reactor, a treatment in at least one clarification pool, at least one recirculation of a portion of the slurry generated in the biological reactors to at least one of them, backfeeding from at least one of the aerobic biological reactors to the same, a second refeeding phase from the outlet of the first aerobic reactor to the interior of the anoxic reactor and a treatment in a refining reactor which operates alternatively in anoxic and aerobic conditions.

Description

D E S C R I P C I Ó N

"BIOLOGICAL PROCEDURE FOR THE CLEANING OF LIQUID WASTE OF HIGH CONTAMINATING LOAD AND / OR HIGH TOXICITY, IN SPECIAL PURINES AND ALPECHINES"

Technical sector of the invention. -

The present invention relates to a biological method of purification of liquid residues of high pollutant load and / or high toxicity.

In particular, the present invention relates to a biological method of purification of the type in which the elimination of contamination of the liquid residue is carried out by metabolic and physical-chemical, aerobic and / or anoxic action of bacteria adapted to the liquid residue. purifying and fixed to a support means for bacteria, and comprising one or more of the following steps:

- a first preliminary physical treatment of the residue for the removal of coarse and sandy materials and bodies, consisting of a roughing and / or a sieving and / or a centrifugation and / or a sanding and / or a degreasing, among others;

- a second preliminary physical treatment of the residue, consisting of the elimination by sedimentation and / or flocculation and / or coagulation of suspended solids that could not be eliminated in the previous stage; - a physical-chemical treatment of the residue for the elimination by precipitation and decantation of the decantable polluting substances, by means of the addition of flocculants and coagulants adapted for the formation of final sludges; - a biological treatment of the waste effluent from the immediate previous stage in at least one bioreactor ^¬ logical aerobically in which the said inoculated bacteriostats rias and to which air is provided to acquire aerobic conditions;

- a biological treatment of the effluent residue from the previous immediate stage, which is carried out in at least one anoxic biological reactor, intended for the eventual de-nitrification of the nitrogen compounds, one of which is disposed upstream of the first bioló reactor Aerobic ¬ gico;

- a final physical treatment of the effluent from the previous immediate stage in at least one clarification pond for the separation of the biomass contained in a biological sludge from the purified final effluent; Y

- at least one recirculation of part of said biological sludge to at least one of said biological reactors.

The process of the present invention finds its main application in the purification of pig purines and olives apricots.

Background of the invention. - It is currently known to purify municipal wastewater, with or without mixing with wastewater, and wastewater of industrial origin in physical-chemical or biological wastewater treatment stations.

The quality of the water and the procedure to be used for its purification is usually determined based on the initial and final value of certain parameters, such as the Biological Oxygen Demand (BOD), the Chemical Oxygen Demand (COD), the concentration in phosphorus, in nitrogen - in its nitric, ammoniacal and organic forms -, in chlorides, in certain metals, such as copper, iron or chromium, among others. The values of these parameters are usually expressed in mg / 1 or parts per million (ppm). Parameters such as salt content, measured in units of conductivity or μSv / cm, concentration in inhibitory materials, expressed in equitox / m ³ and Ph. As a general rule, physical-chemical treatment plants are suitable for those wastewater whose BOD is below a certain value, which indicates that their biodegradability is low, or what is the same, that their organic matter content is not It is so important as to justify the implementation of a biological purification procedure.

In addition, sewage treatment plants that use a biological purification procedure find their usefulness in those wastewater whose D.B.O. It is relatively high.

Generically and in a known way, in the processes of purification of wastewater or liquid waste, the residual liquid, coming from a process (agricultural, industrial or tertiary), is subjected to a first treatment Preliminary physical residue for the removal of coarse and sandy materials and bodies, consisting of a roughing and / or a sieving and / or a centrifugation and / or a dewatering and / or a degreasing, among others. Next, the effluent from the previous stage is treated in another preliminary physical process, in which the suspended solids that have not been eliminated in the previous stage are eliminated by sedimentation, flocculation and / or coagulation. Subsequently, the residue is subjected to a physical-chemical treatment for the elimination by precipitation and decantation of the decantable polluting substances, by means of the addition of flocculants and coagulants adapted for the formation of final sludges. The so-called physico-chemical procedures usually have their end at this stage, obtaining a purified final effluent and a sludge containing the contaminants initially present in the wastewater, whose destination is generally its evacuation. When the residue, as stated, has a high BOD and / or a content in organic materials miners so high that a physical-chemical treatment is insufficient, it must be treated in later stages, in what constitutes a biological purification procedure. In this, the effluent from the previous stage is treated in at least one aerobic biological reactor in which bacteria are inoculated and to which air is provided to acquire aerobic conditions.

The residual water can also be treated in an anoxic biological reactor, for the possible denitrification of the nitrogen compounds, and in at least one clarification raft, for the separation of the biomass contained in a biological sludge from the purified final effluent.

It is known that the aforementioned biological sludge is partially circulated to at least one of said biological reactors.

From US Patents 2,788,127, US 2,875,151 and US 4,874,518, for example, it is known to have one of the anoxic reactors of a biological purification station upstream of the first aerobic biological reactor, so that the incoming residual flow is treated biologically, after effluent from preliminary and physical-chemical treatments, first in an anoxic way, that is to say with the amount of oxygen necessary to guarantee bacterial metabolism, resulting from the breakdown of nitrates.

The advantages of biological treatments for wastewater treatment are widely recognized. In these procedures the purification is carried out by aerobic and anaerobic processes, in which the fundamental agent is the bacteria. Protozoa, algae and certain types of worms and larvae, assume regulatory functions of the process.

Biological purification procedures have basically three advantages. First, the degrading action is carried out only by a group of bacteria, which has the ability to grow and multiply using pollutants and self-perpetuating indefinitely. Consequently, the use of flocculants, chelants and thickeners is nil or very reduced, so that these types of procedures have a low cost in additives.

Second, energy consumption is low. Indeed, the energy requirements are only caused by the need to keep the spill and the bacterial population in contact (homogenization), maintain a sufficient level of oxygen (aeration) and keep the process monitoring mechanisms in operation, pumping fluids and bacterial retroinoculation.

Finally, it should be noted that the biological purification procedures provide a purified final water more easily integrated into the natural environment than that resulting from physical-chemical procedures, since in reality they do nothing but imitate nature. A discharge of wastewater, in non-excessive concentration, to a channel or to the land is naturally cleared by the bacteria existing in these media. Pollution occurs when the concentration or volume of discharges exceeds the natural purification capacity of the environment. In this case, biological purification technology concentrates, intensifies and optimizes this natural system, adapting it to the concentration of the contaminant.

Given the zero or little addition of chemicals, the microbial biomass produced in the purification process is easily reusable.

Effluent liquid waste from some industrial or livestock processes, such as the raising of pigs or the production of olive oil, are so highly concentrated in polluting and toxic organic materials that they cannot be called with absolute rigor as "wastewater", but They should be treated as "liquid waste", although we refer to them interchangeably as such or as "wastewater". Effluent liquid waste from the raising of pigs, known as purines and those from the pressing of olives, called alpechines, currently constitute two cases of purification not effectively solved and, consequently, two important capital problems which should be given a solution.

It should be understood that in the state of the art, the term "high pollutant load" is used for COD values equal to or greater than 4,000 mg 0 ₂ / l. The largest volume of wastewater that requires purification is produced by urban concentrations, whose typical pollutant concentration, measured in COD, ranges between 200 and 1,500 mg 0 ₂ / l, which is a low or medium pollutant load, per the general. Market dynamics establish that the vast majority of wastewater treatment technologies have been developed to treat this type of wastewater, of basically domestic origin.

A typical yield of 95% reduction in pollutants is sufficient so that these purified urban wastewater can be discharged into a public channel without problems.

More recently, traditional, adapted and improved biological technologies have been applied to industrial discharges, but their field of application is limited to pollutants in concentrations and biodegradability characteristics not far from those of urban discharges and with yields not much higher 95%, and never higher than 98%. No waste liquids with high load conta¬ mination, with values greater than 20,000 mg 0 ₂ / COD you even can exceed 100,000 mg 0 ₂ / l, for which these traditional technologies of biological depura¬ tion , even improved, they are insufficient. These high concentrations make it difficult to achieve the necessary balance of biomass growth / concentration of substrate in the biological reactor, produce a rapid depletion of oxygen in the feeding zone, and, therefore, prevent proper use and distribution of it. In addition, if these high concentrations have toxic products or inhibitors associated with them, bacterial growth stops or even mortality or arrest of bacteria metabolism can occur. All these effects produce deficiencies in the purification process, or they can prevent it. Even if these deficiencies did not occur, with traditional technologies, yields close to 98% can be achieved at best, so that the wastewater "purified" would have values of several thousand COD, totally unacceptable to be discharged into a public channel or hardly reusable for most uses.

Attempts have been made to achieve adequate biological procedures for the treatment of wastewater of high pollutant and / or toxic load, with high ammonium content, nitrogen derivatives and phosphorus compounds.

In this regard, US Patents 4,948,514,

US 4,956,094, US 5,076,927, US 5,252,214 and US 5,344,562 describe procedures for the treatment of wastewater with this type of contaminants, particularly applicable to the removal of phosphates and ammonia.

However, in all the documents cited, the initial contamination parameters of the treated wastewater are much lower than those previously mentioned between 20,000 and 100,000 mg 0 ₂ / l. COD, not being suitable for the treatment of such wastewater, as noted in usual practice. Indeed, a biological purification procedure is generically characterized by three component or functional facets, namely: - bacteria (and other microorganisms) that must degrade the organic matter present in the contaminated water;

- a system that allows contact between the bacteria, the wastewater that must be treated and the oxygen needed by the bacteria for metabolism; Y

- an "engineering", or design, dimensioning and distribution of the unit processes, the biological reactors, aeration systems, agitation, water circulation and biological sludge, which are involved in the procedure and are necessary for adequate operation of it.

Traditional biological treatment systems applied to high-load wastewater, including those described in the cited documents, have important limitations in each of the aforementioned three components.

Indeed, as regards the bacteria used in traditional biological treatment plants, these commonly come from biological sludge from other urban wastewater treatment plants. This type of battery does not adapt to the extreme conditions derived from a feeding with a polluting load 20 to 100 times higher than those of its natural development environment.

For special cases (or even to reactivate conventional sewage treatment plants), freeze-dried bacteria specific to some types of pollutants (hydrocarbons, phenols, etc.) are available on the market. The simple inoculation of bacteria of this type has been irregular in its results and almost always with limited temporal efficacy, if it is not accompanied by other actions such as those explained later in describing the present invention.

As regards the contact system of the bacteria with the environment, it can be said that there are basically two types of commercially used biological treatment systems, namely A) the activated sludge system, in which the bacteria are kept in suspension in the water and they go grouping forming flocs that are subsequently decanted to realign to the biological reactor or evacuate from the system as biological sludge; Y

B) the system of the percolating filters, where in a vertical tank filled with a support (usually of the type of rings called "rashig" or similar), the wastewater to be treated percolates between the filling units where the bacteria are anchored, which absorb oxygen from the air occluded in the interstices between the filling units; sometimes a forced air stream is produced that circulates countercurrently of the liquid through the filling.

Due to the dynamics of the bacteria in suspension in the wastewater, the activated sludge system has great limitations when a large concentration of biomass is needed, which, in turn, is necessary when you want to degrade a wastewater with A high concentration in organic pollution.

Many types of filler-support have been developed that improve the surface / volume ratio and therefore increase the capacity of bacterial mass generation, such as those described in German DE-A-4, 107,406 and in the European patent EP-A-630 859. However, in these supports it is not possible to avoid the formation of preferential paths, both for wastewater and for air, from which the drawback is that it is practically impossible to optimize the necessary contact. bacteria / dual water / air. For this reason, among others, these known supports are not sufficient for the degradation of wastewater with a high pollutant load.

Known solutions with fluid bed and upstream supports, although improving the system in some respects, have also proved insufficient to purify high load wastewater. As regards process engineering, a good design of the unit processes of the procedure and the interrelation between them allows the set of batteries and their support to function as effectively as possible. In order for the system to degrade high organic loads, forced aeration of very high yield is necessary, systems that maintain intimate contact between the bacteria and the residual water mass to be purified and some recirculations necessary to re-duct bacterial sludge or to avoid contact of an excessive contaminating load against the bacterial mass. Finally, it is worth mentioning that the current biological purification technology suffers from the inconvenience of the necessary adaptation time of the bacterial culture to the environment in which the waste to be treated in the biological reactors is located, which results in a transitional period several months, obviously undesirable, during which the sewage station cannot operate at full capacity.

Therefore, it is desirable to have a procedure for purification of wastewater or liquid waste with a high pollutant load or with a high content of toxic products that solves the aforementioned problems and inconveniences, in order to obtain much better results and achieve a degree of purification much better than with any of the other procedures known and applied so far and that, in particular, is effectively adequate for the purification of pig purines and vegetable water.

Explanation of the invention. -

To this end, the present invention provides a biological method for the purification of liquid residues of high pollutant load and / or high toxicity, of novel concept, which is essentially characterized in that it comprises the additional stage of a liquid effluent feedback phase from the outlet of at least one of the aerobic biological reactors as influent inside the aerobic biological reactor itself, to dilute the feed with the stabilized liquid at its outlet, in order to dilute the contaminating component below the maximum concentration admitted by the bacteria.

According to a preferred embodiment, the flow rate of said feedback phase is four to fifteen times greater than the feed rate of the aerobic biological reactor.

According to another feature of the present invention, the adaptation of the bacteria to the liquid residue to be purified is carried out independently and externally to any of the biological reactors used in the process, the bacteria being inoculated to the biological reactors when their Biochemical characteristics are already adapted for the immediate action of biological purification on the liquid waste to be treated.

Thanks to the fact that the adaptation of the bacteria is external and foreign to the biological reactor, the adaptation time of the bacteria to the environment can be achieved, once inoculated, is zero, consequently eliminating the undesirable transitional period. In this way, the treatment plant can operate at full capacity from the moment it is started up.

According to another characteristic of the present invention, said support medium for bacteria is completely submerged in at least one of the biological reactors used in the process, leaving a fraction of the population of bacteria suspended in the fluid. of the reactor, in equilibrium with the rest of the bacterial population anchored in the support medium. It has been found that the support form according to the present invention and the consequent balance between the bacteria anchored therein and those that remain in suspension, gives the bacteria a much greater resistance to toxicity than can be achieved currently with the procedures conventional.

In addition, the conjunction of cited features has been Surprisingly shown to be highly effective in order to eliminate the toxicity of the liquid residue to be treated by the process.

According to another feature of the present invention, for the denitrification of the existing ammoniacal components in very high concentrations in the liquid residue, such as pig slurries, a second stage of liquid effluent feedback is carried out from the exit of the first aerobic biological reactor as an influent inside an anoxic biological reactor, said aerobic reactor being adapted for the conversion of ammoniacal compounds into nitrates, while the anoxic reactor is adapted for denitrification of said nitrates with the obtaining of nitrogen gas. Thanks to this, pig manure, highly contaminating and toxic, can be purified up to concentration values in pollutants much lower than the currently authorized maximum and the final purified water is suitable for being discharged into public channels with a high level of integration into the natural environment, which is not possible with conventional biological purification procedures.

According to another preferred embodiment of the present invention, the effluent liquid of said first aerobic biological reactor is introduced into a biological refining reactor, which operates alternatively under anoxic and aerobic conditions, in which biological sludge from other phases is re-dominated prior to the procedure, to compensate for the lack of organic matter, saving the need to add external organic matter, thanks to the endogenous operation of the refining reactor itself, a clarifier preferably being interposed between said aerobic reactor and said refining reactor.

Thanks to this, the process of the present invention makes it possible to dispense with the organic additives that current procedures require, which is one of the causes of the high operating costs of the treatment plants Current biologicals.

Brief description of the drawings.-

A detailed description of the preferred embodiments of the present invention will be given below, for a better understanding of which is accompanied by drawings, given merely by way of non-limiting example, in which: Fig. 1 is an operation principle scheme of an embodiment according to the process of the present invention; and Fig. 2 is another scheme, similar to that of Fig. 1, but of another embodiment of the process of the invention.

Detailed description of the drawings. - The present invention consists of a biological purification procedure applicable for wastewater of high pollutant load, based on the use of bacteria, specifically adapted to the biological reactors that intervene independently and externally to them, with submerged support for bacteria in said biological reactors and with internal recirculation systems or between anoxic-aerobic sections.

The process according to the invention is applied, with results so far not achieved by any other, for the purification, among other liquid residues, of pig slurries and alpechins, achieving a sufficient purified residual water quality, even for its discharge a continental public channel, such as rivers and lakes, among others. As can be seen in the drawings, the biological method of purification of liquid residues 1 of high pollutant load and / or high toxicity of the present invention comprises, in a known manner, a first preliminary physical treatment 3 of the residue in order to remove materials and thick and sandy bodies. This physical treatment Preliminary 3 may typically consist of roughing, sieving, centrifugation, sanding, degreasing, or a combination of these or other physical treatments.

Then, the wastewater is subjected to a second preliminary physical treatment 4, which consists in the elimination by sedimentation and / or flocculation and / or coagulation of the suspended solids that have not been able to be eliminated in the first preliminary physical treatment 3.

One of the phases of the process is a physical-chemical treatment 5 of the residue, with which to obtain the elimination by precipitation and decantation of the decantable contaminant substances, by means of the addition of flocculants and coagulants adapted for the formation of final sludges 6 In the example of the procedure shown in Fig. 1, this physical-chemical treatment 5 is carried out as a phase immediately after the preliminary treatments 3, 4, while in the exemplary embodiment of Fig. 2 it is carried out carried out as the penultimate phase of the procedure. Some of the phases of the procedure consist of a biological treatment of the effluent residue 7 of the immediate previous stage in an aerobic biological reactor 8, in which the bacteria are inoculated and to which air is provided so that it acquires aerobic conditions, thanks to means known aeration 21.

These bacteria are responsible for the elimination of contamination of the liquid residue, thanks to its metabolic and physical-chemical, aerobic and / or anoxic action. The baths are adapted to the liquid waste to be purified and a part of them are fixed to support means 2, while the other part is suspended in the middle of the biological reactor.

The examples shown in the drawings comprise a single aerobic reaction phase, carried out in one or several aerobic biological reactors 8, arranged in series and provided with aerators 21. Another stage is a biological treatment of the effluent residue from the previous immediate stage 9, which is carried out in at least one anoxic biological reactor 10, intended for the possible denitrification of the nitrogenous compounds, arranged upstream of the first aerobic biological reactor 8 (Fig. 2).

The procedure also consists in a manner known per se of a final physical treatment of the effluent from the previous immediate stage in at least one clarification raft 20 for the separation of the biomass contained in a biological sludge 11 from the purified final effluent 12 .

Finally, a recirculation 13 of part of said biological sludge 11 to at least one of said biological reactors 8, 10 completes the phases of an anoxic / aerobic biological clearance of known type.

A first innovative feature of the process of the present invention is the fact that the adaptation of the bacteria to the liquid residue to be purified is carried out independently and externally to any of the biological reactors 8, 10 used in the process. When the metabolic properties of the bacteria have already been adapted for the immediate action of biological purification on the residual liquid waste to be treated, they are inoculated without more than the biological reactors 8, 10. Thanks to this, the transitional period of acquisition of the The nominal regime of the biological reactors 8, 10, as well as in general that of the global treatment plant, is significantly reduced, if not completely suppressed.

For said external adaptation, the type of culture or family of microbial flora most suitable for the particular waste to be treated is selected and its characteristics are optimized in an external process in which the microorganisms are subjected to a high oxygenation rate and fed with the own liquid residue 7, 9 to be purified by bacteria. Thus, the adaptation of the latter is carried out in a reactor (not shown in the drawings), independent of the reactors 8, 10.

It has been found that the period required to obtain an optimized bacterial culture varies between one and three months. From this moment the production of the specific and optimized crop is constant and is used continuously in the operation of the treatment plant in which the process of the invention is applied. The biochemical characteristics of the crop that are obtained externally are: a high oxygen consumption, implying a high rate of oxidation of organic matter; a high exoproteolytic activity, which results in rapid hydrolysis of the protein material, which is a very important component in most of the spills to which this invention is applied; and a high content of cellular exopolysaccharides, which enhance the rapid absorption and flocculation of both colloidal matter and bacteria in suspension of the system.

Another essential feature of the process of the present invention is the fact that said support medium 2 for bacterial culture is completely immersed in at least one of the biological reactors 8, 10 used in the process, leaving a fraction of the population of bacteria in suspension in the reactor fluid 8, 10, in equilibrium with the remaining fraction anchored in the support medium 2.

According to the invention, different types of solid support 2, preferably of plastic material resistant to the medium of the biological reactors, totally submerged therein can be used. The microorganisms colonize the surface of the submerged support 2, being fixed by means of exopolymers (although structures called "pilli" and certain protein adhesins also intervene). The set of microbial biomass that forms on top of a solid is called "biofilm", "fixed biomass" or "adhered biomass".

The advantages of submerged solid support 2 in the Biological actor 8, 10 derive mainly from the fact that it is possible to produce more biomass, have greater degradation activity and more resistance to toxic products and that the space requirement is lower than in the same reactor without supports. This greater biomass and activity is due to the fact that the microbial biofilm that forms in the liquid-solid interface contains higher bacterial density and the fixed bacteria are more active than those dispersed in the liquid phase. A possible explanation of this surprising fact may answer the following:

On the one hand, the mechanisms of ecto-cellular degradation, substrate uptake, retention of enzymes and substrates and transport of substrates, are more effective because the exopolymer weft that constitutes the biofilm acts in the sense of facilitating the interaction between substrates ¬ cough, ectoenzymes and bacteria.

On the other hand, nutrients, oxygen and bacteria are concentrated and accumulated in the solid interface with preference to the liquid phase. To optimize these properties, the submerged support 2 has a high surface / volume ratio and a type of surface that facilitates the bacteria to be easily anchored.

The submerged support 2 of the present invention and its operating conditions allow to establish a dynamic of renewal of the biofilm bacteria anchored in the support 2 towards the suspension in the liquid (and vice versa), thanks to which the anchored bacteria are they find in balance with the suspended ones, favoring their degrading action notably.

For the purposes of the purification capacity of the bacterial culture, the optimization of the active biofilm layer of the present invention - achieved thanks to the aforementioned renewal dynamics - has been shown to be much more important than the optimization of the surface ratio / volume of media, in view of the system's debugging capacity bacterial, recommended by current procedures, whereby the submerged support 2 of the present invention is much more effective than most known complex and therefore expensive supports, which only tend to optimize the surface / volume ratio.

On the other hand, it has also been proven that the fact of completely submerging the support 2, whose bacterial flora is in equilibrium with the bacteria in suspension, allows the use of simple and cheap materials, such as for example corrugated PVC hose, cut in lengths from one to one and a half times its diameter, and of different diameters, depending on the size of the biological reactor.

This determines a procedure whose block diagram and operating principle is the one shown in Fig. 1. A biological treatment plant carried out in accordance with this procedure is highly effective, as has been proven and more justified. forward, for the purification of residues of alpechines in particular and for the purification of organic matter with high carbohydrate content and / or high toxicity, in general.

Another characteristic and innovative feature of the process of the present invention is that it comprises the additional stage of a feedback phase 15 of the liquid effluent from the outlet 14 of at least one of the aerobic biological reactors 8 as influent inside the own aerobic biological reactor 8, as shown in the drawings. This is intended to dilute the feed 7 of the aerobic reactor 8 with the liquid stabilized at its outlet, thanks to which the contaminating component is diluted below the maximum concentration admitted by the baths, with which they can develop its metabolic action.

Preferably, the flow rate of said feedback phase 15 is four to fifteen times greater than the feed rate 7 of the aerobic biological reactor 8.

For denitrification of ammoniacal components existing in very high concentrations in the liquid residue 2, such as pig slurries, the invention comprises the stage of a second feedback 16 of the liquid effluent from the outlet 14 of the first aerobic biological reactor 8 as influent inside said biological reactor anoxic 10. The said aerobic reactor 8 is thus adapted for the conversion of the ammoniacal compounds into nitrates, while the anoxic reactor 10 is adapted for denitrification of said nitrates with the obtaining of nitrogen gas. When nitrogen nitrogen is reduced in the anoxic reactor 10, the bacteria present in said reactor 10 have all the organic material of the feed 9 to produce the desired denitrification, and therefore the purification, which should be understood which is a significant advantage over known procedures, since it effectively allows the purification of liquid waste with a high content of ammonia contaminants, such as pig purines.

Another innovative and characteristic feature of the invention is the inclusion in the process of a stage consisting in the supply of the outgoing effluent from the first aerobic biological reactor 8 to a refining biological reactor 19.

The reactor 19 also comprises the submerged support 2, in which the bacteria obtained according to the present invention are inoculated.

This biological refining reaction carried out in the reactor 19 can alternatively be carried out under anoxic conditions, to obtain an additional denitrification, or aerobic, for the production of a further degradation of the organic matter or the additional nitrification of the residual ammonium The alternation and duration of aerobic and anoxic sequences is determined based on the desired balance of the output parameters.

Obviously, for the necessary aeration of this aerobic phase, the refining reactor 19 comprises an air insufflation system 21, which can be identical to that of the reactor aerobic 8.

The maintenance of the necessary biomass concentration in the aforementioned refining reactor 19 is carried out by the continuous inoculation of biological active sludge 11 from reactors 8, 10. Thanks to this, the lack of organic matter is compensated, saving the need to add external organic matter, such as methanol or any other easily metabolizable substance, due to the endogenous functioning of the refining reactor 19. This allows considerable savings in nutrients for the bacteria and facilitates the formation of decantable flocs , which should be understood as an important advantage with respect to conventional biological purification procedures. Preferably, between said aerobic reactor 8 and said refining reactor 19 a second clarifier is interposed 22. The forced aeration means 21 of the aerobic 8 and refining reactors 19 allow to keep the biomass not anchored in suspension and circulate the water through of the submerged supports 2, in order to achieve the dynamic renewal between the anchored biomass and the suspended biomass and a good contact of the nutrients of the residual water and the dissolved oxygen with the bacteria.

Next, application examples put into practice with application of the principles of the process of the present invention are described and the surprising results obtained from them are described. Practical examples. - 1. Alpechines

An alpine scrubber station was designed and built, based on the process of the present invention, for a capacity of 4 m ³ / day. The process scheme responds to that shown in Fig. 1.

Alpechines arrive at the station in tank trucks or containers and empty and homogenize in a tank (not shown).

The process consists of roughing 3 and settling 4, followed by a physical-chemical treatment 5 with lime ((OH) ₂ Ca), from which, after neutralization they are fed to an aerobic biological reactor 8. The solids, after passing through a thickener 20, are dried in a filter press (not shown) and are evacuated in containers for use as agricultural fertilizer or landfill. The aerobic biological reactor 8 has the submerged support 2 according to the invention and is aerated by air insufflation means 21, also having a recirculation 15 of at least six times its feed flow 7.

The clarified residual liquid in 20 is evacuated to the drain (submarine emissary in this case). The decanted biological sludge 11 is realigned to the aerobic biological reactor 8. The extreme difficulty of the biological degradation of the alpechines derives from its content in phenols and polyphenols. Therefore, for the phase of specific adaptation of the bacteria according to the invention, commercial freeze-dried bacteria resistant to phenols were started, which were adapted externally to the plant. Given the toxicity of this residue, these bacteria must be re-harvested (in small quantities) periodically to the reactor 8. Table 1 shows the analytical evolution of the main parameters at the entrance and exit of the procedure.

Table 1

It is worth noting the surprising reduction of the toxicity parameters obtained by the application of the method of the present invention applied to the purification of alpechines, achievements not obtained with any of the currently known technologies.

2. Pork manure

A research purification station was designed and built, also based on the process of the present invention, of industrial size, next to a breeding farm of 950 mothers (and the corresponding piglets), with a purification capacity of 25 - 30 m ³ / day of slurry. The process scheme is the one corresponding to Fig. 2.

The slurries from the farm or from the outside by cisterns are collected in a stirred homogenization raft

(not shown) from where the purification plant is pumped.

The process begins with two stages of separation of solids, which are eliminated as organic fertilizer. A first stage consists of a first preliminary physical treatment, specifically a sieve 3. The turbid liquid separates It is mixed with a polyelectrolyte prepared in a tank and fed to a centrifuge 4, where it is subjected to the second preliminary stage of physical separation. The effluent liquid part of the centrifuge 4 is fed to the anoxic biological reactor 10, from where it passes to the aerobic reactor 8, with a recirculation between reactors 8 to 10 four to fifteen times greater than the feed rate of the reactor 10, according to the present invention. Reactors 8, 10 have a submerged support system 2 such as that described in the present invention.

In a pilot plant of 2 m ³ of reaction volume, foreign to the sewage plant itself, the bacterial culture was produced after months of adaptation, which was inoculated into the reactors 8, 10 at the same time of laying in progress of the treatment plant. This bacterial culture was produced in accordance with the principles of the present invention.

Downstream of the aerobic reactor 8, the resulting treated liquid is decanted in clarifier 22, from which biological sludge 11 is recirculated to reactors 8 and 10 in the form of sludge 13 and / or extracted from the system by 6, after dehydration in the centrifuge 4.

According to the invention, in order to improve the parameters of the purified waste water, the effluent from the clarifier 22 is fed to a refining biological reactor 19, which also incorporates the bacterial culture anchored in the submerged support 2 according to the invention with the adapted bacteria as explained. According to the invention, the refining reactor 19 can alternatively operate in aerobic or anoxic mode, depending on the parameter to be eliminated (COD, NH ₄ ⁺ , N0 ₃ ^" ) ^•

Finally, after another settling in a second clarifier (not shown), also provided with recirculation of active sludge, a physical-chemical treatment is carried out in tank 5, where phosphorus derivatives are precipitated, the rest of suspension materials, and a part of the residual organic matter. The precipitated solids are they decant in a third clarifier 20, whose effluent was found to be a purified and transparent liquid that could be poured into the river or reused.

Table 2 shows the typical analytical data of the main parameters and their evolution in the different phases of the process, obtained with the treatment of purmes in the purifier of Example 2, which applied the principles of the present invention.

Table 2

It should be understood, in view of Table 2, that thanks to the method of the present invention applied to purification of slurries, parameters of purified residual water are never achieved until now by any other known method of purification of liquid waste or wastewater of high organic pollutant load.

Describing sufficiently the nature of the invention, as well as the way of putting it into practice, it is noted that everything that does not alter, change or modify its principle fundamental, it may be subject to variations in detail. In this regard, it should be understood that the biological treatment plants in which the method of the present invention is applied as a principle of operation, may comprise additional unit processes other than those explained, provided that the procedure conforms to the scope of protection of the characteristics claimed here.

It should also be understood that the parameters of pollutant concentration of the wastewater to be treated can be any, without being restricted to the indicated values, without thereby leaving the scope of protection of the inventive concept.

The essential and for which patent of invention is requested, for twenty years, is what is summarized in the following claims.

Claims

1.- Biological procedure for the purification of liquid waste (1) of high pollutant load and / or high toxicity, of the type in which the elimination of the contamination of the liquid waste is carried out by metabolic and physical-chemical, aerobic and / or anoxic of bacteria adapted to the liquid residue to be purified and fixed to support means (2) for the bacteria, and comprising one or more of the following stages: - a first preliminary physical treatment (3) of the residue for the removal of coarse and sandy materials and bodies, consisting of roughing and / or sieving and / or centrifugation and / or sanding and / or degreasing, among others; - a second preliminary physical treatment (4) of the residue, consisting of the elimination by sedimentation and / or flocculation and / or coagulation of the suspended solids that could not be eliminated in the previous stage;

- a physical-chemical treatment (5) of the residue for the elimination by precipitation and decantation of the decantable polluting substances, by means of the addition of flocculants and coagulants adapted for the formation of final sludges (6);

- a biological treatment of the effluent residue (7) of the immediate previous stage in at least one aerobic biological reactor (8) in which the said bacteria are inoculated and to which air is provided to acquire aerobic conditions;

- a biological treatment of the effluent residue from the previous immediate stage (9), which is carried out in at least one anoxic biological reactor (10), intended for the eventual denitrification of the nitrogen compounds, one of which water is disposed above the first aerobic biological reactor (8); - a final physical treatment of the stage effluent immediate anterior in at least one clarification raft (20) for the separation of the biomass contained in a biological sludge (11) from the purified final effluent (12); Y

- at least one recirculation (13) of part of said biological sludge to at least one of said biological reactors (8, 10), characterized in that it comprises the additional stage of a feedback phase (15) of the liquid effluent from the outlet (14) of at least one of the aerobic biological reactors (8) as influent inside the aerobic biological reactor (8), to dilute the feed thereto with the stabilized liquid at its outlet and dilute accordingly the contaminating component below the maximum concentration admitted by bacteria.

2. Method according to claim 1, characterized in that the flow rate of said feedback phase (15) is four to fifteen times greater than the feed rate (7) of the aerobic biological reactor (8).

3.- Procedure according to any one of the preceding claims, characterized in that the adaptation of the bacteria to the liquid residue to be purified is carried out independently and externally to any of the biological reactors used in the procedure, the bacteria being inoculated into the Biological reactors when their biochemical characteristics are already adapted for the immediate action of biological purification on the liquid waste to be treated.

4.- Procedure according to any one of the preceding claims, characterized in that said support medium (2) for bacteria is completely submerged in at least one of the biological reactors used in the process, leaving a fraction of the population of bacteria in suspension in the reactor fluid, in equilibrium with the remaining fraction anchored in the support medium.

5.- Procedure according to any of the preceding claims, characterized in that, for undressing trification of the existing ammoniacal components in very high concentrations in the liquid waste (2), such as pig slurry, a second stage of feedback (16) of the liquid effluent is carried out from the outlet (14) of the first aerobic biological reactor (8) as an influent inside said anoxic biological reactor (10), said aerobic reactor being adapted for the conversion of ammoniacal compounds into nitrates, while the anoxic reactor (10) is adapted for denitrification of said nitrates with Obtaining nitrogen gas.

6. Method according to claim 5, characterized in that the effluent liquid of said first aerobic biological reactor (8) is introduced into a biological refining reactor (19), which operates alternatively under anoxic and aerobic conditions, in which Biological sludge (11) coming from other previous phases (8, 10) of the procedure, to compensate for the lack of organic matter, saving the need to add external organic matter, thanks to the endogenous functioning of the refining reactor itself, being preferably a clarifier (22) interposed between said aerobic reactor (8) and said refining reactor (19).