MXJL00000003A - Treatment of polluted waters, using capillary aeration and. - Google Patents

Abstract

RECIRCULATION OF CLASSIFIED MUDS The present invention discloses a treatment of capillary aeration with recirculation of classified muds, formed by the following stages: influent ingress; done by means of a solids sieve where only raw waters are percolated in the first stage; Recirculation pumping, of the liquor mixed inside the tank of biologic oxidation, to all the capillary conduits for generating the liquid interfaces surface; air injection, by means of a fan with blades, generating a gaseous flow through the conduits formed by the liquid inside the conduit, where the gaseous interfaces surface is generated; agitation, provided by means of a mechanic agitator to have a mixing through a flow directed toward the entrance influent in order to propitiate its diffusion it. When the recirculation, the liquid mixing and the air injection start, all the conditions are generated to perform oxygen transference by means of the capillary aeration with recirculation of classified muds. Outlet, the effluent directs the treated waters in the tank, to the stage where the muds are settled and classified, recirculating to the aeration tank a proportion to maintain an appropriate inoculation and concentration of organisms, achieving parallely a higher stabilization of heavy muds, before their removal.

Description

TREATMENT OF CONTAMINATED WATER BASED ON CAPILLARY AERATION AND RECIRCULATION OF CLASSIFIED SLUDGE.

Technical field: Biological treatment of activated sludge for municipal sewage or industrial wastewater: Background: At present, several methods of aeration are known in the treatment systems of sewage, municipal or industrial residual waters in some cases, so we will describe in a very general way the characteristics of the systems that have been handled, to establish the difference with respect to what has been called as classified laminar aeration.

System of aeration by bubbles, these consist of the generation of bubbles in the bottom of the aeration tanks, sometimes called oxygenation tanks, where gas bubbles are diffused in the liquid system, in some cases the flow of the rising bubbles causes sufficient agitation, to ensure that the gas that has been transferred, is sufficiently diffused throughout the liquid volume of the tank and in some occasions stirring equipment is installed, to improve mixing conditions, one of the characteristics Most relevant of this type of system is the one that refers to the large amount of interface area that is generated and that is the surface through which the gas transfer is made, another notable feature is the contact time that is achieves between the volume of gas confined in the bubble and the liquid, which brings as a consequence that in this type of systems high utilization of the oxygen, being larger the smaller the diameter of the bubbles generated. The magnitude of the interface area is a function of the average diameter of the bubbles and the amount of air supplied; the contact time is a function of the speed of rise of the bubble, which depends on the diameter of the bubbles, and the depth of the tank; considering that two systems participate, one gaseous and the other liquid, both have a boundary film that divides them, called gaseous interface surface and liquid interface surface, respectively, around the liquid system, talking about a liquid interface film that has to be the gas transfer is a function of the flow conditions existing in the gaseous system, that is, a flow between laminar and transition will have an interface renewal factor close to unity, so the transfer in these cases will be function only of the gas diffusion coefficient in the liquid and the thickness of the liquid interface film considered, the renewal factor will increase as the turbulence of the gaseous fluid increases, the gas transfer to the liquid system also depends on the conditions of concentration of the gaseous system that provides the O.

The transfer can also be analyzed considering a film of interfaces in the gaseous system in which case it will depend on the flow conditions in the liquid interfaces and the concentration conditions of the liquid interfaces; In both cases, both the concentration factor and the renewal factor have to accelerate or slow down the speed with which the mass transfer is carried out according to its magnitude.

Tensoative materials and high concentrations of pollutants tend to decrease the speed of oxygen transfer, since the rigidity of the spherical structure of the bubble, especially in the finer bubbles, demands more dissipation of energy for renovation. of the liquid interface surface, specifically this is because the surface tension of the liquid increases and generates a greater resistance to deformation of the spherical film of liquid interfaces, when this surface is in equilibrium, as it would be in this case bubbles.

Some of the disadvantages of this type of aeration system relate to the impossibility of providing effective agitation in the gaseous system, and although agitation can be applied to the liquid system, the results may not be profitable for its implementation since the characteristics of the gas confined in the bubble, the only thing that would be done is to transport it from one place to another, without presenting a high degree of slippage of gaseous particles precisely in the area of the film interfaces, and on the other hand the volume confined per unit area generated is relatively small, causing the effects of a long contact time to be neutralized; bubble diffuser systems have a relatively high maintenance cost, regardless of the cost of the energy needed to compress the air and make it reach the diffusers.

Contact aeration systems; These are formed by concrete structural tanks, which are filled with a porous material-based packaging, which may be of mineral origin such as stones, pieces of glass or prefabricated plastic material, these provide an extensive surface where microorganisms adhere forming a biological film, which remains fixed to the surface until reaching a thickness in which there are conditions that allow it to remove itself periodically; the organisms of the film breathe the oxygen that exists in the formed holes; the drainage system allows air circulation up or down, depending on the temperatures of the influent and the porous medium, in order to improve the oxygen supply especially for the film that is in the lower parts; the most usual depth is 2 meters; in these systems, the liquid is spread continuously or intermittently for units of high load or low load respectively, in the upper part by means of a series of nozzles mounted on sprinkler tubes, which can be fixed or have rectilinear movement or circular, depending on the configuration of the tank; the microorganisms receive the food of the liquid that drains on the surface; currently 2 3 there are materials that can provide 40 to 100 m / m of surface area, to cover a wide range of needs, by the form of application and layout of the area takes advantage of approximately 40 to 85% of the surface, which is wet at intervals of approximately every 5 min. in the case of low load installations or continuously for high load installations; the units of low load, usually handle a 3 2 hydraulic load of 1.5 to 6 m / m x total day, and an organic load of 0.08 to 1.5 3 kg / m of useful tank volume; the high load units can handle 3 2 a hydraulic load of 7 to 25 m / m x day and an organic load of 1.6 to 15 3 kg / m of useful tank volume; Contact aeration systems, also called drip filters, can eliminate 80 to 85% for low load and 50 to 79% for high load.

In reference exclusively to the process of aeration by contact, it has to start from the moment in which the nozzles of the sprinklers generate the set of drops that form a rain, either intermittent or continuous as the case may be, at this stage the time The contact area and the interface area are very small, so their effects are insignificant; When the drops arrive and make contact with the filtering medium, the liquid spreads and runs on the walls of the filter in such a way that the thickness of the liquid film becomes smaller and smaller until it reaches a time when, due to the properties of the superficial tension and the viscous conditions of the liquid, this moves to a lower speed and by the effects of the gravity the liquid will be filtering or draining by the small interstices of the film, giving opportunity for the case of the application intermittent, that the film absorbs liquid and the liquid when drained by the effects of gravity, helps the unoccupied spaces, fill with air, which, when a new film of liquid and organic matter polluting with a high degree of humidity, it perches in the spaces dislodged by the liquid of the previous film trapping gas microbubbles; It is important to mention that when a continuous feeding is being handled, the process behaves like the activated sludge process, that is, the biological activity in the film, its intensity decreases and a large part of the biological activity is generated by the bacteria that they are suspended in the liquid; another feature of these systems, is that they have an immense contact surface, and usually good contact times and a relatively short retention time, the configuration of the system, demands a large volume for the generation of the interface surface, This is due to the space occupied by the solid material of the filter and the empty spaces that constitute one of the characteristics of this type of units.

An advantageous feature of this type of system is its ability to withstand sudden variations in organic load; It is also necessary that, in the low load systems, a percentage of the nitrification is carried out, which is due to the fact that there are types of nitrifying bacteria that develop attached to the contact surface, because they have sufficient time and oxygen. For their develpment.

The main disadvantage consists of the large spaces that are required for the construction of the structures; the maintenance to restore the operation, when waterlogging phenomena occur is one of the most common problems that occur; Another effect that constitutes a disadvantage consists in the generation of favorable conditions for the development of flies.

There are a number of devices introduced to this type of aeration systems, in order to adapt them to a greater number of treatment needs, such as the recirculation of sludge from the primary settler, from the secondary settler, from the same effluent from the aeration tank , in different percentages; there are also one- and two-stage systems, with the first stage of high rate and the second of low rate usually being.

Mechanical aeration system; Mechanical aeration is characterized by the use of electromechanical equipment that works directly submerged totally or partially in the liquid, such as agitation by means of a propeller or turbine, a paddle stirrer or a Kessner brush agitator, which is usually installed over the course of a channel or ditch.

In all these systems it is sought that the agitator element fulfills two basic functions that are: that of agitation with the purpose of generating a certain surface of interfaces and secondly that of providing an agitation with the purpose of achieving a mixture that provide adequate contact between organic contaminating nutrients, bacteriological organisms that will be responsible for metabolizing organic matter and dissolved oxygen, which is transferred through the interface surface generated.

The disadvantages of this type of system is that the interface area and the contact time of the systems are small in comparison with other systems that handle large interface surfaces or longer contact times.

Another aspect that makes it possible to compensate for the deficit effects of a large area of interfaces and long contact times, in these cases is the application of longer retention times, a concept that involves managing large structures, thus becoming an economic disadvantage.

The main advantages refer to the excellent concentration conditions, both in the liquid and gaseous interface, which are very favorable, in addition the renewal factors are excellent both in the liquid and gaseous systems, to the extent that they manage to compensate the deficits of a large contact area or a long contact time.

There are some patented aeration processes, which are based on any of the three previous systems, but introduce some modifications to the processes as below, can be summarized in the following terms: Conventional aeration; this consists of submitting the sludge to the aeration process, which can be mechanical or bubble, during a certain period of time from 6 to 8 hrs; recirculating, from 20 to 30%, which are mixed with the influent; the conventional process may be provided with a primary sedimentation stage and a secondary sedimentation stage.

Staged Aeration; In this system, the influent is distributed in several points of the tank and the recirculated sludge is introduced in the initial point where the influent water is entered, this implies that the concentration of solids is higher at the beginning and decreases as the waters are advancing towards the other stages; with this modification it is possible to reduce the retention time by up to 50%, as long as the sludge residence time is managed between 3 to 4 days, in this process the basic system of aeration is by means of bubbles, although it can also be mechanical in some cases.

Graduated aeration; this process has the peculiarity that it assumes that the highest BOD is at the beginning of the tank and decreases as it advances, so that a greater injection of air is made at the beginning and decreases as it approaches the effluent outlet, In this process the basic system of aeration is by means of bubbles.

Extended Aeration; also known as prolonged aeration, this process is characterized by the application of longer retention times, to achieve high levels of abatement of the BOD, consequently the process can be applied with aeration systems by bubbles and mechanics.

Activated Aeration; Waste sludge is channeled here in excess and mixed with raw black water and subjected to aeration to condition it and maintain a source of active sludge that allows intensifying or restoring the continuity of biological activity when it is affected by the introduction of sludge. toxic substances or sudden overloads that inhibit the process; The basic aeration process can be mechanical or bubble.

Description The classified aeration method consists of subjecting the sludge within a system of activated sludge to any compatible aeration process, but with the recirculation of previously classified sludges based on the following: Using a sludge classifier, three possible types of sludge are available, which are: Heavy sludge; this is in relation to one of its physical characteristics as its high sedimentation rate, these correspond to sludges that have a high degree of treatment, that have been chemically reduced by oxidation to simpler substances and that can be considered biologically stable; depending on the objectives pursued with the treatments, most of the processes are designed for reasons of profitability, to achieve the stabilization of one part of the BOD and mineralize another part, depending on the efficiency of the same, a small percentage it remains in the effluent, so in these cases, the stabilized BOD is constituted by the residual or excess sludge, this matter unnecessarily increases the viscosity of the sludge, since its permanence inside the tank, instead of encouraging the biological process , inhibits it by occupying a space, which would be more convenient to be occupied by active bacteria or organic matter; due to its characteristics, it will facilitate its subsequent treatment, which may be its spreading, final stabilization or drying.

Intermediate sludges; formed by developing flocs, which due to their physical, chemical and biological characteristics, have an intermediate sedimentation rate; the content of stabilized matter is regular, as well as, the content of particles and bacteria of small sizes is regular; all this gives a certain characteristic to sludge, which makes them very versatile to make adjustments in the concentration of sludge inside the plant, without falling into extreme concentrations, these sludges allow any management, which obviously, do not represent any risk, but they do not contribute effects of considerable importance, such as when they are returned, the inoculation effect may be sufficient to maintain biological activity or, for example, their removal if necessary, unpleasant odors must be less intense than would be caused by unsorted sludges and much less the light mud that contains a higher concentration of organic matter, fresh and active organisms.

Light sludges; These are made up of fine particles that have the lowest sedimentation rates, which may be organic matter, partially stabilized matter, or that has been assimilated in the generation of new bacteria, also small flocs formed by bacteria that start their development, which because of their size they settle together with the light mud; all this converts light sludge into the most biologically active, a quality that must be considered to handle them more conveniently within the plant.

As in many processes already known, different proportions of sludge are handled, although this is very relative, since the main objective pursued with the recirculation, is to maintain an adequate concentration of bacteriological sludge, depending on the organic load that it is being fed to the plant, so, maintaining this concentration will depend on the operator's ability and how to carry out the recirculation or removal of excess sludge, based on this relativity, and In order to give more certainty to sludge management operations, the proportions that serve as a design basis for the classified aeration treatment processes, assume that of the total sludge that is sedimented, the heavy ones correspond to those that they are collected on 33.33% of the length of the settler; For most applications there will be 2 sections of 33.33% c / u that are considered light; when there is a specific application then the intermediate section will be considered for the intermediate sludge.

With a well-designed sludge operation regime, it will be possible to generate any concentration that is effective for the system.

The objective of the classified aeration is to contribute to improve the operation of the treatment plants in the following aspects: It can help to maintain the active muds with better levels of effectiveness, since they can always remove more stabilized muds and recirculate the biologically more active muds. . It allows to have a more adequate control in the age of the active sludge, due to the fact that the inert bacteria that are the ones that make up the biggest and heaviest floccules, that is to say, the most stabilized ones, these being the ones that can be removed without running the risk of removing new sludge, and through the recirculation, of the light mud, it is guaranteed that sludge under development or new sludge, continue its development inside the tank, until they acquire the characteristics that can make them reach the section of heavy mud.

The sludge that is channeled to be removed as surplus sludge, can be handled with less intense unpleasant odors, since they have been classified and correspond to the most stabilized ones, so that in case a final stabilization treatment is applied, this it will be with shorter retention times, and for the same degree of stabilization, the concentration or coating operation is easier, for its subsequent treatment, which can be drying in sand beds.

Regardless of the known aeration systems, to which the sludge classification method can be implemented, the development of the capillary aeration system is presented below as described below.

Capillary aeration system as such; consists of a set of ducts in the form of plates or sheets, which can be manufactured with environmentally resistant covers, such as high density polyethylene and PVC, this system provides most of the oxygen required by the process, since a part small amount of oxygen is transferred to the surface of the oxidation tank, by the action of a mechanical aeration system on a small scale, which is applied for mixing purposes to facilitate the contact of 02, bacteria and contaminating organic matter, besides achieving a complementary aeration in the same tank; The set of conduits was conceived in such a way that practically 100% of the available surface can be used, which is achieved by generating a liquid sheet over the entire perimeter of the conduit internally, this is achieved through the design of flow deflectors, which are illustrated in the following: Figure 1, plan view of a flow deflector, inside the capillary conduit. Figure 2, view of a section of a side section of a flow deflector. Figure 3, side view of a flow deflector. Figure 4, view of a front cut of a flow deflector.

The ducts formed by sheets of PVC (No 1) inside which are inserted a series of deflectors (No 2), which can be the same material of the conduit, or a soft rubber to allow the introduction of a tool for uncover in case of some type of tamponade; These baffles are attached to the duct sheet by means of the baffle support (No 3), these deflectors provide several characteristics that are described below: This system is one of the most manipulable treatment systems, and also predictable, varying flow conditions in the liquid system, flow conditions in the gaseous system and biological conditions of the sludge being recirculated, all these variations can be managed in a independent to be studied, can be observed and measured, so they make the system among other applications suitable for the implementation of prototypes for scientific and university research. During the operation of the system, at the time of exposure, and by the diffusional characteristics, an amount of oxygen is absorbed by the liquid system to be transported to the oxidation tank in the form of microbubbles or dissolved oxygen OD, an action that is facilitated because on the interfaces surface, the intermolecular forces are in imbalance, so this surface will be more receptive to the DO. Due to its handling characteristics, it is evident that the effects of limitation due to being confined volumes, as in the case of bubble systems, we can compensate here with the injection of more air, without considerable increases in energy or, of a greater dosage of liquid.

As a larger interface surface is being handled in turbulent conditions such as in mechanical aeration systems, and as physical, chemical and biological conditions are improved, it is logical that there will be a greater oxidation or mineralization of contaminating organic matter, which is added to the atmosphere in the form of carbon dioxide, or is transformed into water, which is added to the liquid system, the latter occurs mainly in the nitrification of nitrogenous matter; the assimilation of a part of contaminants that result in the generation of new cells, will always be able to develop under better conditions since the stable matter is constantly removed and the sludge that forms the inoculation system is returned in better conditions and On the other hand, it can be expected that the absorption of organic matter that generates stabilized sludge will decrease to a certain degree, which should imply a greater reduction by oxidation or mineralization, this being a desirable condition in most plants; it is important to keep in mind that the changes are probably barely perceptible to the naked eye or that they are minimal compared to a properly designed and operated process, this is due to the fact that any process that operates correctly, in case of overcoming it, will only be in a few hundredths of efficiency, other indications will be a lower consumption of energy and the use of smaller facilities, to be able to handle shorter retention times.

The capillary aeration system has a novel feature, which refers to the possibility of designing and building an aeration system, which makes it possible to take advantage of both the upper and lower surface of a duct, according to the profile shown in figure 2, with this, the surface of contact of the interface is increased by the use of the entire possible surface, that is, the liquid flows throughout the interior periphery of the duct, this can be generated thanks to the property of the surface tension of the water that allows it to sliding on the upper surface, under certain conditions of slope and roughness, allowing a second internal gaseous flow to pass, such that it allows to improve the oxygen concentration in the gas interface at levels that favor the transfer of oxygen, with a low energy consumption.

The way in which conduit plates are placed with respect to each other, is illustrated in the following figures: Figure 5, plan view of a sheet of capillary ducts. Figure 6, side view of a block of capillary duct sheets. Figure 7, front view of a block of sheets of capillary ducts.

The form that refers to the arrangement of the set of pipelines, which is in the form of plates as illustrated in figures 5, 6 and 7, in such a way that in an extremely simple way, we can generate the amount of interface surface, by the fact that we can stack "N" number of duct plates; the space required to generate any surface requirement, within reasonable ranges is extremely small but above all, efficient; Another important detail consists in the fact that the plates of the aerator are mounted on a concrete structure which allows that in the oxidation tank, the necessary agitation can be supplied for mixing and to achieve a complementary transfer of oxygen, to satisfy high oxygen demands.

Applied kinetic theory: The theory that has been taken as a basis assumes a theoretical model, which has two reference surfaces for the study of oxygen transfer, very similar to the concept of two films of interfaces, a soda and a liquid, raised by W.K. Lewis and W.C. Whitman in (Principie of Absortion, Ind. Eng. Chem.), According to Gordon Maskew Fair, John Charles Geyer and Daniel Alexander Okun, in his book Water Purification, Treatment and Removal of Wastewater; In the capillary aeration system, some concepts are handled, such as a factor of concentration conditions in the FCIL and FCIG interfaces, which can have a liquid or gaseous system respectively to increase or decrease the transfer rate of a certain amount of mass in depending on the degree of saturation or deficiency reached by the system, to illustrate this concept, we have that in a mechanical aeration system, we have the best conditions both to receive in the case of the liquid system or to yield in the case of the gaseous system , for the reason that, the liquid system during the operation, is subject to intense agitation, which allows liquid films with low oxygen concentrations to be exposed one after another, a number of times that is determined by the renewal factor of liquid interface, and by the own conditions of the liquid system, the films that are exposed, can co Consider that they start with a Cilo concentration, which is the average concentration maintained in the tank; however, said interface will increase its concentration as much as the conditions of the degree of saturation in the gas system allow, which is equal to the concentration of 02 of the atmospheric air, as well as the number of films of the gas interface participating in said transfer; and in an analogous way it happens in the gaseous system.

Figure 18 shows the behavior of the concentration in the liquid system inside the capillary aerator, first, the graph (No 3), represents the variation of the concentration in the liquid interface film, which has a period of time that it is a function of the contact time and the surface renewal factor, each cycle of these graphs start with a concentration Ctilo that corresponds to the one that has the liquid sheet inside the duct at that precise moment, reaching the concentration that allows the exposure of a new movie The graph (No 4) represents the behavior of the concentration of oxygen in the liquid sheet inside the duct, the initial concentration of this graph is the concentration Cio of oxygen that is normally maintained as an average in the biological oxidation tank; the exit concentration Clf (No 15) can reach the saturation concentration Cls (No 1) in a time tls (No 9) if there is enough length in the ducts, or the conditions of availability of oxygen and The thickness of the liquid film allows it, but in general the length of the ducts must be the one that allows to reach the Clt concentration (No 15) in time Te (No 8), this is usually handled for reasons of profitability in the level of use of atmospheric oxygen; the graph (No 5) shows the time (No 10) that it would take the system to reach the saturation concentration within the volume of the tank under conditions of biological equilibrium; the graph (No 6) shows the time (No 11) that is necessary to satisfy the biochemical oxygen demand of a volume equal to that of the oxidation tank, the time to achieve the BOD satisfaction of the volume of the tank is that which is commonly it is known as retention time TR, if said time is divided by the time required for the saturation of the volume of the tank, this will indicate the number of times that the volume of the tank must be completely saturated, in order to satisfy the demand of the BOD of the tank volume; the graph (No 7) serves as a point of reference, since we will always try to reach the saturation of the daily volume in the unit of time (No 12), which is usually a day, this helps us to modulate our system at the time of design; the axis of the ordinates (No 10) represents the concentration of dissolved oxygen in mg / l and the axis of the coordinates represents the time in seconds on a logarithmic scale.

Figure 19 represents the behavior of the gaseous system within a treatment system, where the transfer occurs through a contact surface, so that the mathematical model of the interfaces films is applicable, which can be deduced from the figure in question; the graph (No 4) represents the behavior of the concentration of oxygen in the atmospheric air inside the capillary, where in an analogous way, if you have enough length and the conditions of the liquid system allow it, the concentration of oxygen can drop to a concentration Cgs (No 2) at time tgs (No 6), it also has to be in the gaseous flow, within the duct the concentration Ctg (No 9) can be reached at the TC contact time (No 5), which it must be the same that is handled in the liquid system; Figure 3 represents the behavior of the concentration in the gas interface, which starts in each cycle with the concentration Ctigo that has the gaseous flow inside the duct at that precise moment; The gaseous flow will always start with the atmospheric air concentration.

The factors that determine the turbulence of flow and with it the factors of surface renewal are: the thickness of the flow sheet, the slope of the sheets, the number of baffles as well as the internal dimensions of the duct, all this allows to manipulate or vary the Reynolds number, which is an indicator of the turbulence conditions that are being handled; the way in which energy is dissipated is producing turbulent conditions just in the entire liquid film to achieve high transfer rates, with energy consumption similar to that of mechanical aeration systems but with lower retention times; the energy that is supplied to the fluid begins to release in the descent of the liquid, developing a flow velocity, which is a direct function of the slope and roughness conditions, equivalent to the diffusers that have three specific functions, induce the formation of the upper fluid sheet, increasing the interfaces surface, limits the speed of the flow, improving the contact time and help to increase the turbulence, favoring the renewal of the limit film of interfaces.

There are other factors that influence the generation and renewal of the surface, such as the lateral scission that is inside the duct, the effect of this runoff contributes to the improvement of the renewal factor inside the duct, the effect of this runoff must be important, and its precise determination, it is feasible that it can be determined in a prototype, considering that its effects are positive, and because it has no greater references, its effect is considered negligible; On the other hand, the calculation of the interface surface is made as a function of the inner perimeter of the duct formed by the peripheral inner sheet of the fluid, the size of the inner duct must consider enough space to allow the gaseous flow, even with presence of the bacteriological film, although it is important to mention that the system has foreseen to prevent the formation of the biological film, when the light influence on the surface of the ducts is prevented, and the intermittency conditions in the application of the liquid on the surface, so the conditions conducive to the development of a possible biological film are minimal.

Regarding the renewal given by the condition of the turbulence, that is, a laminar flow will have a factor of unitary interfacial renewal and as the speed increases, the generated turbulence will cause the renovation of the interface film to be renewed with a greater intensity. In the case of capillary aerators, these effects are associated with the slope of the aerator, that is, when the slope is close to zero, the velocity of the flow is very low and consequently, the flow tends to be laminar and the F.R.I. tends to unity; As we increase the slope, speed increases, a greater turbulence is generated, which helps the interface film to be renewed with a greater intensity, being able to manage for outstanding profitability issues between 0.1 and 0.2, the large slopes significantly reduce the contact time of the liquid interface and demand more energy.

There is another stage of the type of flow that develops in a fluid in motion, called transition flow, in this type of flow, the liquid film of the interface area, begins to renew slowly, so that it is very likely that there is a Reynolds number, which limits the laminar flow in order to establish the transfer that takes place under laminar flow conditions, so that later, a reference can be made with other speed conditions, for which, the Reynolds number and the transfer, can give an idea of the theoretical number of films that intervene in a certain sy.

Around the Reynolds number, and taking as a reference the behavior of the different stages through which a flow passes, we must, as long as a laminar flow prevails, under certain conditions of the thickness and the linear dimension that is involved, the boundary layer in contact with the gas remains in the area of the interface, and so a certain time may elapse while the flow conditions do not change, this implies that if a certain oxygen transfer takes place, this would occur very similarly as said phenomenon occurs. a static volume, with the difference that, here the volume is displaced, and although there is a displacement between particles of the film adhered to the surface on which the liquid film slides, for the mass transfer analyzes that arise In the theory of the two films of interfaces in capillary flows, they define a fairly well defined stage, which, should be characterized, by that the gas transfer per unit of exposed liquid surface directly depends on the diffusion coefficient of the gas in the liquid Kd. If the Reynolds Number is determined, for different speed conditions whose gas transfer does not change, a value of the Reynolds number can be determined, for which the transfer begins to increase with the increases in speed, which must indicate the conditions that limit a constant transfer rate, with respect to this number, and that determine the start of a transfer that changes with respect to a FRS factor, which is very likely to have a logarithmic relationship with the number of Reynolds.

The criterion for determining the Reynolds number according to analogous parameters may not be able to be determined with precision given the complexity of the different treatment sys, but they may give a clear idea of their effects on the surface renewal factor, considering it as next it is proposed: No. R = Ei xVi / (v) Ec 1 Where: Ei = Film thickness of interfaces in m.

Vi = Speed with which the interfaces are moved in m / s.

For the capillary aeration sy, there is a reference speed with which the flow sheet moves, for a particular case it is: Vil = 0.83 m / s It must be taken into account that this speed depends on the slope of the ducts, the density of the deflectors per unit length, the thickness of the flow sheet and the kinematic viscosity of the fluid, the indicated speed corresponds to a design specific, handling water at 20 ° C with a -4 3 slope of 0.125, with a flow through conduit of 1.25 x 10 m / s with 3 deflectors per m. of length of conduit, which can be from 1.25 to 2 meters; the recommended nominal interface area is 0.1818 m./mgxl of BOD, with which the length of the ducts can be determined for various conditions, as discussed below; this factor results from considering that it is feasible to achieve the same transfer as in a mechanical aeration sy, applying a factor of 2.5 on an average of applied surface, although this factor is conservative, for a more defined application, it could be corrected based on observations to a prototype.

The velocity of the gaseous flow within the conduit can be determined in the following way: Vig = Qge x Vd / 86400 x NC x 0.048x 0.08 Ec 2 Where: Qge = Air flow in m / m of sewage.

Vd = Daily volume in m / day of sewage.

NC = Number of conduits. 0. 048 and 0.01 are the estimated internal dimensions for the passage of the gas flow through the conduit. 2 v = Kinematic viscosity of the fluid that forms the interfaces in m / s. 2 The kinematic viscosity considered for the liquid is: 0.00000101 m / s The kinematic viscosity considered for the gas is: 0.0000135 m / s Eil = Qs / ai Ec 3 Where: Qs = Flow or flow of black water in m / s, for each milligram of BOD and per 3 liter of the flow of the influent, to transfer 0.0066 Kg / m, considering the initial and saturation concentrations 2 and 8.6 mg / l, respectively : Qs = 0.0001515 m3 / s. ai = Area of interfaces that intervenes in m / s. = No. of sheets x A. R.L x L = BOD x Qi x 0.1818 The determination of the thickness of the gaseous interface film is made based on the flow that provides transfer required based on the coefficient of use that is available in each type of system.

Eig = Qgi / ai Ec 4 Starting from the handling of the concentrations in terms of the dissolved oxygen deficiencies, as well as the covered deficiency, we have that the behavior can be analyzed by means of a first order equation such as: dD / dt = -KD Ec 5 Ordering terms: dD / D Kdt Ec 6 Integrating you have: / dD / D = / -Kdt Ec 7 Ln Dt-LnDo + C1 = -K (t-to) + C2 Ec 8 By the rules of logarithms can be written as: Ln (Dt / Do) Kt + C3 Ec 9 From the graphic behavior, the following can be inferred: Dt = Cs-Ct Ec 10 Do = Cs - Co Ec 11 Eliminating the natural logarithm of equation 9 and considering that the constant part can be divided into a sum of constants, without altering equality, and replacing equations 10 and 11 in 8, we have: -Kt Cs-Ct = (Cs-Co) e + C0 + C0 Ec 12 Clearing Ct you have: -Kt Ct = (Cs-Co) - (Cs-Co) e + Co Ec 13 -Kt Ct = Co + (Cs - Co) (1 - e) Ec14 As the constant of speed Kt, you must consider factors that accelerate or decelerate the transfer within the conduit, that is, that constant is a function of the diffusion coefficient of the oxygen in the liquid, the thickness of the film considered, the varying conditions of the concentration, and the surface renewal factor of the complementary system, hypothetically pose equations 15 and 16 as they are written below: Kdilc = - ((Kpl x Kd x FRIG / Eil) - (FCIG x Kd / Eil x (1 - e))) E 15 Where: Kdilc = Coefficient of velocity with which the gas transfer is made to the liquid system inside the ducts.

FCIG = Initial concentration factor at the gaseous interfaces, this factor is dimensionless and will have an initial value of 1, for most of the cases, this factor can decrease with respect to D according to the conditions of each system. -09 2 Kd = Oxygen diffusion coefficient in black water = 1.8 x 10 cm / s.

FRIG = Renewal factor of the interface surface in the gaseous system, it is dimensionless and the initial value that this factor can have is 1 due to the behavior of the films or sheets in a laminar flow in the gaseous system, and can increase up to a value determined by the conditions of turbulence induced by some means.

Kpl = Adjustment factor that allows adjusting the mathematical model developed for the liquid system.

P = Use of oxygen in decimals.

In an analogous way we have: Kdigc = - ((Kpg x Kd x FRIL / Eig) - (FCIL x Kd / Eig x (1 - e))) Ec 16 Where: Kpg = Adjustment factor that allows to handle the mathematical model developed for the gaseous system.

FCIL = Concentration factor in the liquid interface, which normally has an initial value of 0.825 and will vary depending on the conditions of each system.

FRIL = Renewal factor of the interface film in the liquid system, which is dimensionless and depends on the flow conditions, that is, its minimum value must be 1 and corresponds to static or laminar flow to flow conditions. transition, its optimal value will be when the conditions of turbulence that provide the highest transfer rate in profitable conditions.

Equation 15 represents the mathematical model of the behavior of the liquid system that as can be seen in Figure 18, where; the axis of the ordinates (No 14) represents the concentration of oxygen in mg / l of the liquid system, the axis (No 13) represents the time in seconds on a logarithmic scale; the transfer of mass, is the sum of millions of transfer events in each cycle formed by the division of each second, in a number of cycles determined by the conditions of surface renewal, these events are represented by the graphs (No 3) which are derived from the graph (No 4), and represents the transfer of oxygen that is transferred in each segment of interface film, which as you can see, each cycle is different in the first place because the initial concentration Ctilo is increasing as the liquid sheet moves; the speed with which the transfer is made is not constant and finally the frame of reference that corresponds to the concentrations of both systems is changing with respect to time, so that the constants used in the equation must consider all these adjustments; the saturation concentration Cls (No 1) is a limiting factor of the transfer; the initial Cío concentration inside the ducts (No 2) as the flow of the liquid sheet moves, until it reaches the Ctlc concentration in the contact time (No 8) determined by the length of the ducts and by the flow velocity , therefore, if it were of sufficient length it would reach saturation in a time Tls (No 9); the graph (No 5) shows the time (No 10) that the system would take, to saturate the volume of the tank under biologically stable conditions; the graph (No 6) shows the time TR (No 11) that the system would take to satisfy the BOD of the volume of the tank and finally the graph (No 7) shows the reference time and corresponds to a day, this marks the time (No 12) in which the system must satisfy the BOD of the daily volume.

For the application of equation 15 in the liquid interface, represented by the graph (No 3) of figure 18 it is important to note that the coefficient of proportionality is the renewal factor of the interface surface considered for the liquid system, it is say: Kdlc = Kdil / FRIL Ec 17 Equation 16 represents the mathematical model of the behavior of the gaseous system which, as can be seen in figure 19, is a graph analogous to that of figure 21, but in this case instead of the mass entering, it leaves the system; firstly, the gaseous flow enters the ducts with the concentration of atmospheric oxygen Catm (No 1), on the other hand there is a critical concentration Cgs (No 2) of oxygen reached by the graph (No 4) and it is the concentration to where most of the aerobic biological systems are able to survive as long as the other necessary conditions of their ecosystem exist in the required form, in this case; the length of the conduits that implies the time tgs (No 6), the graph (No 4) also shows the time TC (No 5) that the system takes in stable biological conditions in descending until the concentration Ctg (No 9), the graphic (No 3) represents the transfer in an interface movie; the axis of the ordinates (No 8) represents the concentration of oxygen in mg / l and the axis of the coordinates (No 7) represents the time in seconds, on a logarithmic scale.

For the application of equation 16 in the gaseous interfaces, represented by graph 3 of figure 19, it is important to note that the coefficient of proportionality is the renewal factor of the interface surface considered for the gaseous system, ie: Kdgc = Kdig / FRIG Ec 18 The instantaneous flow of air is determined by: Qgi = Qge x Vd / 86400 Ec 19 For the corresponding calculations, it is necessary to manage the oxygen available in the gaseous system, such as the volume of gas that the biological treatment system is able to extract from the gas system as a concentration in the gas system analogous to the concentration of gas saturation in the gas system. the liquid, which we represent as: Cgs = 0.84 Catm. = 229.32 mg / l Ec 20 The coefficient 0.84 is based on the consideration that the conditions that occur in the systems of aeration by bubbles, are similar in terms of the way in which the transfer is carried out, but with their respective characteristics each, therefore it is considered in equal conditions, there must be the same use, which is considered 16% of atmospheric oxygen, that is, in terms of this percentage, it is said that if a system takes advantage of 100% of usable oxygen, in real terms, the system is only taking advantage of 16% of the atmospheric oxygen that passes through the system; Now, it is possible that this coefficient differs when there are changes in the equilibrium conditions of the surface interface stresses, which determine the intensity of the surface tension, due to the Van der Walls forces, which is very feasible, and in the case that said hypothesis was confirmed, it would be positive as shown by the mechanical aeration treatment systems, in these the interface surface is very small, but its reception capacity is very large, which may be due, in addition from the favorable factors of concentration, to the condition of imbalance of the intermolecular forces characteristic in a flat surface of a liquid such as water and that determine the surface tension, because as some physics studies suggest, the spherical surface of a drop or a bubble, represent a surface whose efforts due to the forces of Van der Walls are balanced which implies structuring very rigid surface that can constitute a resistance to a certain transfer through it, and of course, it is also very likely that this structure represents a resistance to the process of surface renewal, causing the transfer to be hampered by the limitations that saturation concentrations represent.

However, of the mass of gas available, the aeration system is able to transfer a percentage of this gas, as mentioned by Motarjemi and Jameson according to Michael A. Wintler in his book Biological treatment of wastewater, on the use of oxygen in a bubble system, in such a way that under certain considerations, in the capillary systems some proposed values have been estimated, so that a practical application should be supported with laboratory tests.

The calculation of the interface area, which for the case of capillary systems, is the internal area of the operating duct that limits the liquid system of the gaseous system, is determined as follows: ai = NC x (ANC + HNC - ENLF) x 2 x LRL Ec 21 Where: ANC = Nominal width of the duct.

HNC = Nominal height of the duct.

ENLF = Nominal thickness of the flow sheet.

LRL = Actual length of the duct sheet.

It is important to define the direction in which the interface surfaces can have changes, such as the height of a bubble aeration tank, or the equivalent radius of the surface area of a mechanical aeration tank or the length of the laminar conduits to through which are presented changes in the interface surface, to consider the relevant variations for each case, that is, the change that the surface manifests in 1 s of this path is analyzed; so we would have a series of bubbles of 1 mm in diameter, will travel a length of 0.13 meters. that is, at a speed of 0.13 m / s, which would correspond to a specific time of 1 s. in such a way that if the tank is 3 meters. of depth, the contact time would be 23 s; for the case of pipes with a density of 3 deflectors per 3 m. in length, handling a flow of 0.000125 m / s per pipe, where the speed developed by the flow is 0.83 m / s, with a slope of 0.125 and for a particular design, we would have: TC = 1 s.

Te = 1 s / m.

This implies that the theoretical analysis is based on the changes experienced by each element of the 1 m interface area for one second.

Another concept that intervenes is that which refers to a correction factor for the interface area, which, in the case of bubbles, depends on the difference in pressure at which the air is injected and the pressure at which it is released. and that corresponds to the atmospheric pressure; The analogous factor for capillary aeration systems consists in establishing a correction to the original area produced by the structure of the walls of the duct, depending on the thickness of the liquid fluid sheet and the variations that will occur when growth of the fluid is developed. biological film, on the internal walls of the duct; although it is sought not to promote this film to work the system continuously, and not allow light infiltration, so the surface of the ducts will usually be submerged, preventing bacteria that develop adhered to the walls, do not find the conditions propitious for its development; Assuming that some biological development could occur, this may be limited by maintenance actions, when a reduction of 0.92 is presented, although it is feasible that these conditions do not arise, it is assumed that in case of certain bacteriological development, This behaves in the same way as it behaves in trickling filters or fixed culture systems, that is, the film as part of its development cycle, starts, grows and reaches a thickness that promotes the cells that are attached to the wall, die propitiating the detachment of the film, and in the last case, the design of the aerator can allow with the use of a suitable tool to uncover the conduits in a simple way, therefore in a conservative way it can be established that : FCS = 0.92 The retention time is the time that the waters in process are submitted to reach a certain degree of treatment, depending on the process that is applied, as well as the BOD levels of the influent and the BOD required in the effluent, making a comparative study between bubble aeration systems, a mechanical aeration system and classified capillary aeration systems, and given that it is considered that the magnitude of the inertial area is reasonably overcome by the mechanical aeration system in the extended aeration mode, and assuming that the conditions of concentration and renewal of interface surface, are the most adequate to have a high rate of oxygen transfer, and with an adequate culture of microorganisms, the estimated retention times will be between 8 and 16 hrs, depending on the objectives and conditions of each case.

TR = Retention time in s.

Having defined most of the parameters that somehow intervene in the determination of oxygen transfer, we can define in the terms of the theory of the films of interfaces, the rate at which such transfer occurs as follows: It may be practical to establish an instant biochemical demand, BOD, that is, the demand that the waters in process or the system must handle in Kg 02 / s, and which is determined by: DBOi = BOD x Qli Ec 22 TTL = DBOi / (ai x Eil x D x FCS x TR x Te) Ec 23 Where the BOD is the biochemical oxygen demand in Kg 02 / m of sewage, for practical purposes it can usually be determined experimentally in a laboratory, and never be based on bibliographic references, for the reason that the physical, chemical and biological characteristics of the water, they change from one place to another.

D = Distance in which changes occur in the unit of time considered to determine the mass transferred in m / s.

BOD = Qge x Catm x% 0. d x% 0? a / (1000 x 10000) Ec 24 Where: Catm = Concentration of O in atmospheric air in mg / l. % 02 d = Percentage of atmospheric oxygen that biological treatment systems can have. % 02 a = Percentage of available oxygen that is used by the treatment system with the conditions of each system.

In analogous form we would have that the transfer seen from the gas system, would be determined by: TTG = DBOi / (EigxaixDxFCSxTRxTe) Ec 25 Starting from the fact that the transfer occurs through a succession of interface films, an equation can be proposed that allows us to determine the transfer that the system experiences per unit of time in s and by 2 unit of area, in m, so can pose the following hypothesis: TTL = (Ctil - Cito) x FRIL / (Te x 1000) Ec 26 O well: TTL = (Ctfl - Cío) / (Te x 1000) Ec27 Where: Ctfl = Concentration of the liquid that leaves the duct.

And analogously: TTG = (Ctig - Cgto) x FRIG / (Tex 1000) Ec28 O well: TTG = (Ctfg - Catm) / (Te x1000) Ec 29 Where: Ctfg = The concentration of oxygen in the air leaving the duct.

According to the theory that has been proposed for the transfer of oxygen through two interface films, we have to: Ctii = (TTL x Te x 1000 / FRIL) + Cito Ec 30 In an analogous way we have: Ctig = (TTG x TC x 1000 / FRIG) + Cgto Ec 31 Substituting 17 and 18 in equation 14, we have: -Kdil xte / FRIL Ctil = Cito + (Cs - Cito) x (1 - e) Ec 32 In an analogous way we have: -Kdig x te / FRIG Ctig = Cgto + (Cgs - Cgto) x (1 - e) Ec 33 The constants with which the oxygen transfer is given, Kdl and Kdg, can be cleared from equations 32 and 33 or they can be calculated from equations 15 and 16 as already established.

The oxygen transferred in Kg OJ m of sewage is determined by: TTLO = TTL x ai x Eil x D x FCS x TR x Te / Qli Ec 34 And analogously, for the gaseous system, the transfer in Kg 3 OJ m is given by: TTLG = TTG x ai x Eig x D x FCS x TR x Te / Qgi Ec 35 As can be seen in the capillary system, the transfer capacity depends on the liquid and gas flows that can be channeled to the set of conduits, to form the most extensive surface of the fluid sheet, with the appropriate thickness, in the form more economical and practical, immediately it can be observed that the management of the gaseous flow does not have any problem of handling, due to the low amount of energy that requires its management, referring to the liquid flow, this requires more care in the analysis, due to which is the means of transportation of dissolved oxygen, which is transferred to the oxidation tank, so that the liquid flow must be sufficient for the oxygen flow to be as required, and not be hindered by the concentration of sewage, operating conditions such as temperature among others; the effectiveness of the system will obviously depend on managing the greatest possible difference between the concentration of inlet and outlet of the liquid in the ducts, it will depend on achieving the maximum possible contact time, with the greatest possible turbulence but with the slope that implies the lowest height , so that the energy consumption is the lowest possible.

Functioning: Capillary capillary aeration tank consists of a system of aration, which is illustrated by figure 8, it works as follows: The waters of the influent, together with the classified sludge that is recirculated and that can come from any stage whatsoever, of primary or secondary treatment, according to the objective, enter through an inlet pipe (No 5) and normally in the first stage, they pass to a screen (No 11), which separates all the solids from the fresh water that could clog the aerator's duct system; the black waters already screened or cast, enter the oxidation tank (No 10) from where the mixed liquor is recirculated by means of a pumping equipment (No 8) to the distributor tank No (No 4) to be distributed in the form of a shower through the perforated plate (No 2); to all the sheets of ducts, which form blocks of plates or sheets of ducts (No 1), which are placed on a concrete ramp, which is built with the required slope, and is supported by support columns (No 9). ); when the system is in operation, fan fans (No 3) induce an air flow, which is forced to circulate through all the ducts, to always maintain high concentrations of oxygen in the gas interfaces; a moderate agitation and optionally an aeration can be applied by means of a stirrer, formed by a gearmotor (No. 7) and a deflection elbow (No. 6) which houses the helix inside, this elbow serves to conveniently direct the flow currents inside the tank; the treated water flows to the settler through the outlet pipe, located at the lowest point of the floor of the tank, in order to be removing all the flocs that form, with good settling characteristics, the bottom has a slope of 15% in order that with little agitation, heavy sludge can be induced towards the outlet pipe, which must have a record of purging heavy sediments, such as fine sand that could indudr and accumulate as sediment, this is for the purpose of avoiding silting inside the tank and outlet pipe.

Screen of solids; The purpose of the sieve design is to strain the effluent's raw sewage so that it passes directly from the sieve to the oxidation tank, without the need for a discharge pipe at the outlet of the flow already cast, this element significantly reduces the BOD, separating a certain amount of organic matter in the form of small suspended solids, that of introducing itself to the aerators that could possibly cause blockages in the capillary systems; On the other hand, if the aeration system has the capacity to provide enough oxygen to biologically process these solids, they can be crushed and re-incorporated into the treatment, so as not to cause a large amount of untreated organic solids that can cause problems. of contamination, an adequate handling of these could be the drying in the sun for its later incineration, or else to bury them in previously sealed pits, later to close them and by an anaerobic process to cause their degradation; in this way, the oxidant capacity of the treatment plants corresponding to these solids is exploited in achieving better effluent quality; The design of the screen considers that the structure is balanced in order to facilitate its assembly, its construction can be made of carbon steel, with an adequate coating; The screening specifications that normally satisfy the requirements are: Maximum diameter of the passage of solids 0.00095 mts. Flow capacity, according to requirement. Nominal slope of the sieve: 1,428 The screen is also an important element in the process, then illustrated in the following figures: Figure 9, plan view of the screen. Figure 10, side view of the screen. Figure 11, front view of the screen.

The operation of this consists in entering the water through the inlet pipe (No 3) towards a pouring box (No 1), which distributes all the inflow along a pouring plate; the sieve is designed in such a way that the waters fall directly towards the aeration tank, the waters that leave the spillway, fall to the sieve (No 2), all the separated solids skid over the sieve and fall to a wheelbarrow where they are periodically removed for later handling; the box of the screen, has a purge (No 4), which has the function of giving maintenance of cleaning and desazolve in case of being required; The construction materials normally used are: The entire structure can be made of carbon steel, and optionally stainless steel, the element that forms the sieve, as it is constituted by very thin elements, it is necessary that it is invariably made of stainless steel.

Mechanical agitator; Another important element is the agitator, illustrated in the figures: Figure 12; Plan view of the mechanical agitator. Figure 13; Front view of the mechanical agitator. Figure 14; side view of the mechanical agitator.

This agitator has been designed to suck a flow vertically and project it horizontally to induce a mixture inside the capillary aeration tanks and optionally it can provide a complementary aeration within the process of capillary aeration classified, for the treatment of sewage, where it requires directing the flow conveniently, the agitator consists of a deflector elbow (No 1) that is submerged in the waters under treatment, in the lower part of the elbow is the propeller (No 2), formed by blades, which are solidly screwed. to a blade holder, which carries a cradle to solidly fix the arrow, which is moved by the gearmotor (No. 3), which can be replaced by a speed variator, to be able to supply more energy at certain times; the elbow is supported by a structural steel pedestal (No 4), which hangs from a structural base (No 5); The design of the propeller is based on the following formulation: The width of the blade of the propeller is: a = Qag / (L x Vtan x Cos ang x Tan ang x 4) Ec 36 Where: The design angle of attack is in the following range: ang = (30 ° to 36 °) Qag = Flow generated to create the required mixing conditions, approximately 60 Ips for each Ips to be treated in case an additional oxygen transfer is required, the corresponding analysis must be done.

Vtan = mean tangential velocity, which for practical purposes is considered the tangential velocity of a point located 2/3 from the center of the propeller towards the end of this.

Vtan = RPM / 60 Dme x pi Ec 37 Number of blades = 4.

The manometric height developed by the helix is given by: HMT = Vtan "x Tan ang / (2 x 9.81) Ec 38 Where: The acceleration of gravity is: 9.81 m / s * The length of the blade is a function of: 0.5 x 0.9 x DHE Ec 39 Where 0.9 is a factor that depends on the size of the blade holder mamelón. DHE = outer diameter of the propeller. The power transmission capacity of the arrow is given by: 2 2 1/2 P = NDf3? ((S2 (2 x F / pi x Df)) Ec 40 Where: F = axial thrust = P / m x PHE + weight of the propeller + Ke x HMT. Ec 41 P / m = Weight of the arrow in Kg per m. of length. PHE = depth to which the helix is located in m. Axial thrust constant of the propeller.

Ke = 234.25 x DHE Ec 42 Mean diameter of the helix in m.

Dme = 2 x DHE / 3 Ec 43 The power demand of the propeller is given by: BHP = Qag x HMT x Pe / 76 x Ef Ec 44 Pe = Specific weight of the water in process Ef = Volumetric efficiency of the propeller, considering approximately 0.8.

Typical applications of a treatment based on capillary aeration, with recirculation of classified sludge; Below are three types of treatment processes, which are feasible to develop, but here the only thing that should be clear is that the "way to manipulate" the different extracts, which will have to be analyzed for each particular case, is illustrated. taking into consideration the type of organic load, which can be low, medium and high; the constitution of the nature of the organic load, as carbon organic matter and nitrogen organic matter, as well as the possibilities of each type of process to provide oxygen and the concentration of organisms required.

Figure 15 shows a flow diagram where schematically represents a treatment system based on capillary aeration with recirculation of 2 strata of sludge classified, single-stage, to remove the carbonaceous matter, which is described below: The influent makes its entry through a screen of solids (No 7) arriving at the oxidation tank (No 1), in this tank is where the waters are aerated and they are provided with agitation to have an adequate mixing, besides optionally you can also dose a greater amount of energy to generate complementary aeration; after receiving sufficient aeration, the treated liquor passes to the sedimentation tank (No 2), provided with a sludge classifier system, where the aerated liquor is clarified; the clarified water leaves the settler through the outlet pourer (No. 5) to the next stage, which will usually be a tank where chlorine is applied, in order to eliminate pathogenic bacteria; in this case, the classification of sedimented sludge is in two layers, which are: the heavy sludge (No 6), are those that will be removed from the system, when there is an excess of sludge in the aeration tank, so that these do not acquire anaerobic conditions, they can be recirculated through a bypass in the section (No 3) of the heavy mud pipe; the intermediate and light mud will form the second layer (No 4), which will be recirculated on a daily basis; With this operation, whenever excessive sludge is produced, the most stabilized sludge will always be removed and a more intense inoculation will be exercised by recirculating the most active sludge, which will improve the biological activity of the plant.

Figure 16 shows a flow diagram where schematically represents a treatment system based on capillary aeration with recirculation of 2 strata of sludge classified, in two stages, to perform the BODc in a first stage and a nitrification that starts in the first stage and is complemented in a second stage, this process is described below: The influent makes its entry through a screen of solids (No 11) when it comes to the first stage, or passing to the oxidation tank (No 1) directly when it comes to the subsequent stages, where the same conditions exist than in an aeration tank of a single-stage system; After having received enough aeration to achieve the removal of a good part of the BOD, a small part of the nitrogen organic matter is nitrified, in other words, a small part of the biochemical demand of the nitrogen organic matter is subtracted ( BOD), the treated liquor, goes to the sedimentation tank (No 2), provided with a sludge classifier system, where the liquor aerated in the first stage is clarified, the clarified water leaves the sedimentator towards the second stage of aeration, the Heavy sludge (No 5), sedimented in the first stage of sedimentation, will be recirculated or removed as required by the system, the intermediate and light sludges, sedimented in the first stage, will be recirculated daily to keep in the aeration tank of the first stage , very active biological conditions, the water clarified in the first stage of sedimentation, passes to the biological oxidation tank of the second stage (No 3), normally provided with the same aeration systems, in this tank, depending on the objectives and the treatment specifications, it is feasible that the DBOc is finished and partially a good proportion of the BOD, the liquor aerated in this tank passes to the sedimentation final (No 4), where the heavy sludge settled at this stage, can be recirculated to the first stage on a daily basis, for the reason that they will carry a good proportion of nitrifying bacteria, which are of slow development and therefore, not It is convenient to eliminate them in this stage, since when recirculating them, it is possible to return all the viable nitrifying bacteria propitiating that the nitrification starts from the first stage, the intermediate and light sludges are recirculated in this process to the tank (No 3) so as not to lose the nitrifying sludge that develops mainly in this tank; the clarified waters in the second stage, largely nitrified, leave the settler of the second stage, to pass to a chlorination tank where it is disinfected by the application of chlorine, in order to eliminate pathogenic bacteria; With the classification of the sludge, the biological control of the treatment plant is facilitated by having the possibility of making more objective adjustments, since the most stabilized sludge can always be removed and the most active sludge recirculated according to the stage of concerned, which will improve the biological activity of the plant.

Figure 17 shows a flow chart where a treatment system based on capillary aeration with recirculation of 3 strata of classified sludge, of three stages, is represented schematically, this process partially eliminates a quantity of the BODc and a small part of it. the BOD in the first stage, in the second stage the remaining BOD is eliminated and gradually a higher BOD, in the third stage the elimination of BOD is complemented, the process is described below: The influent makes its entry through a screen of solids (No. 17) arriving at the oxidation tank (No. 1), where the same conditions are given as in an aeration tank of a single-stage system; after having received enough aeration to achieve the removal of a good part of the BOD, reaching to nitrify a small part of the biochemical demand of the nitrogen organic matter (BOD), the liquor treated, goes to the sedimentation tank (No 4), provided with a classifier system of three types of sludge, where the liquor aerated in the first stage is clarified, the clarified water leaves the sedimentator towards the second stage of aeration ( No 2), the heavy sludge (No 7), sedimented in the first stage of sedimentation, together with the heavy iodine of the second stage (No 10), are recirculated or disposed of as excess sludge passing to a stabilization stage end or thickness for subsequent drying; the intermediate sludges (No 8) of the first and second stages (No. 11) are recirculated to the aeration tank (No. 2) of the second stage in order to maintain a balanced biological activity in the second stage of aeration, at this stage a significant proportion of the BOD can be removed and gradually greater removal of the BOD, in situations where the organic load is mixed and relatively high; the light nodes (No 9), the light sludge from the second stage (No 12) and the heavy sludge from the third stage, are recirculated to the first stage of aeration, with the aim of generating a high degree of inoculation of both bacteria heterotrophic, carbonaceous matter, as well as nitrifying bacteria of the first and second stage of nitrification, ie nitrosomonas and nitrobacter in this way, there is a gradual nitrification from the first stage; the liquor treated in the tank of the second stage, passes to the settler of the second stage (No. 5), where as already indicated, three types of sludge are obtained; the clarified water in this sedimentation tank goes to the biological oxidation tank (No 3), of the third stage, where the nitrification process is predominantly carried out, in such a way that the treated liquor passes to the sedimentation tank (No 6) where by means of of the sedimentation, the nitrifying bacteria are retained, which as already indicated, the heavy sludge that sediments in this stage, is recirculated to the first stage, to propitiate the nitrification from the first stage, and in this way to maintain a long time of residence of nitrifying bacteria that are very slow to develop, especially nitrosomonas that metabolize ammoniacal nitrogen to nitrites; the light sludge is recirculated to the tank of the third stage, to always maintain the most intense nitrification in stage three; finally the clarified waters of this stage can be passed to a chlorination tank where chlorine disinfection is carried out, with disinfectant purposes to eliminate pathogenic bacteria; it is possible to make different combinations in the channeling of sludge depending on the degree of contamination of the influent, the proportion of carbonaceous and nitrogen pollutants, the capacity of the process and the desired quality in the effluent, for example; The organic carbon contained in the heavy sludge can be mixed with a proportion of the fresh water to provide the organic carbon necessary for the denitrification of the waters from a nitrification stage.

Claims (2)

Claims Having sufficiently described my invention, I consider as a novelty and therefore claim as my exclusive property, what is contained in the following clauses:

1. - The treatment of contaminated water based on capillary aeration and recirculation of classified sludge, which consists of the following stages: a) Screening of solids; consistent to filter the raw waters in the first stage, by means of a structure for screening, which is designed to be able to pour the screened waters directly to the biological oxidation tank, without the need of a flanged end in the discharge. b) Recirculation pumping; by means of axial flow pumps, which pump large volumes at a low level of mixed liquor into the biological oxidation tank, to a distributor tank, to distribute the flow in the form of a shower through a plate in the form of a sieve, to all the capillary conduits, so that in this way a liquid interfaces surface is generated, inside the blocks of duct sheets. c) Air injection; by means of fan blades, which handle large volumes at low pressure, whose cover is conditioned to generate the gaseous flow, through the ducts formed the liquid inside the duct, which slides in the form of film or sheet, adhered to the inner wall, where the surface of gaseous interfaces is generated. d) Agitation; by means of a mechanical stirrer, stirring is provided to have a suitable mixing, besides that optionally it is also possible to dose a greater amount of energy to generate a complementary aeration, this agitator by means of a deflecting elbow, takes a flow of liquid in vertical position and projects it horizontally, to direct the flow to the point of entry of the influent and promote the diffusion of this. e) When the recirculation of the mixed liquor and the injection of air are being based, the conditions are generated so that an oxygen transfer is being effected by means of capillary aeration with recirculation of classified sludge. f) Exit of the effluent from the tank, this is located in the lowest part of the bottom of the tank, with the purpose of not accumulating sediment in the bottom, this outlet conducts the treated water in this tank, to the next stage of sedimentation, where the sludge is sedimented and classified, recirculating to the aeration tank a proportion to maintain an appropriate concentration of organisms, and achieving a greater stabilization of the heavy sludge, before its removal. In order to: a) Have a simpler, easier and safer control over the residence time of the activated sludge. b) Maintain a greater proportion of active bacteria within the process and consequently, decrease the proportion of inert bacteria. c) To have a more effective inoculation system, by recirculating the most biologically active sludge. d) Achieve a greater degree of stabilization of the heavy sludge, by recirculating them and removing them when they constitute an excess of sludge in the tank, which facilitates the stages of their subsequent treatment. e) Achieve better levels of overall efficiency in the treatment.

2. -Air capillary tank, as a whole, which consists of the following components: a) A structure supported by columns, which serves to mount on ramps the blocks of duct sheets, the same structure serves to mount on this, the recirculation pumps, the mechanical agitators and the fans; On one part of the structure of the wall, a screen is mounted, when it comes to the first stage of aeration, the bottom of the tank has a slope of 15%, to ensure that with a gentle agitation, the sediments are induced towards the outlet, the outlet pipe can carry in the most strategic point a record for heavy sediment purge. b) The mechanical agitator, which has the function of promoting adequate mixing and preventing the formation of sediments, conveniently directing the flow of the liquid, being able through it to supply enough energy to generate a complementary transfer of oxygen, in order to have greater oxygen transfer, which can be handled optionally in the critical hours of higher organic load , generating a possible energy saving and having a system that can provide an additional transfer when this is required at certain hours, this is feasible by means of a drive via a variable speed drive instead of the gearmotor; this agitator, in terms of the specification of the materials, it is feasible its construction in carbon steel, stainless steel arrow, propeller and bronze bearing, or total manufacture in stainless steel, to meet different needs in terms of chemical quality of water. c) The fan fan, which provides the air flow necessary to generate the gaseous flow within the capillary ducts; and whose configuration of the roof is adequate to the structural needs of the capillary aeration system; the construction of the hopper or cover of said fan must be stainless steel, for the reason that it is exposed to splashing of the water in process, which can usually have corrosive characteristics, the thickness of the sheet, is not required that is thick, because the structure, although it will handle large volumes of air, will work at very low pressures; the propeller can be aluminum and the recommended engine can be a TCCVE frame. d) The solid screening screen, which is designed to be able to pour the screened water directly into the biological oxidation tank, without the need for an additional discharge tube, that is, the structure at the bottom, is open for the purpose of allow the drainage of the 100% cast water in such a way that its operation is simpler, on the other hand the structure is balanced, with the purpose that its placement can be done in the easiest way on any point of the wall of the tank.