WO2002000558A1 - Procede de traitement des eaux usees par aeration de surface et recirculation des boues classifiees - Google Patents

Procede de traitement des eaux usees par aeration de surface et recirculation des boues classifiees Download PDF

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WO2002000558A1
WO2002000558A1 PCT/MX2001/000041 MX0100041W WO0200558A1 WO 2002000558 A1 WO2002000558 A1 WO 2002000558A1 MX 0100041 W MX0100041 W MX 0100041W WO 0200558 A1 WO0200558 A1 WO 0200558A1
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aeration
tank
sludge
liquid
oxygen
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Simón I. CASTAÑEDA ESCORZA
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/12—Activated sludge processes
    • C02F3/14—Activated sludge processes using surface aeration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/12—Activated sludge processes
    • C02F3/14—Activated sludge processes using surface aeration
    • C02F3/16—Activated sludge processes using surface aeration the aerator having a vertical axis
    • C02F3/165—Activated sludge processes using surface aeration the aerator having a vertical axis using vertical aeration channels
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/005—Black water originating from toilets
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

  • Bubble aeration system consist of the generation of bubbles at the bottom of aeration tanks, where gas bubbles are diffused in the liquid system, in some cases it is necessary that the flow of rising bubbles causes sufficient agitation, to ensure that the gas that has been transferred, diffuses enough throughout the tank, sometimes stirring equipment is installed, to improve the mixing conditions
  • one of the most relevant characteristics of this type of systems is 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 achieved between the volume of gas confined in the bubble and the liquid, which brings as a consequence that in this type of systems high uses of oxygen are obtained, being larger the smaller the diameter of gene bubbles radas;
  • 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 bubble ascent rate, which depends on their diameter, and the depth of the tank; considering that two systems participate, one gas and one liquid, both they have a
  • the transfer can also be analyzed, considering an interphase film in the gas system, in which case it will depend on the flow conditions in the liquid interface and the concentration conditions of the liquid interface; In both cases, both the concentration factor and the renewal factor must accelerate or slow down the speed with which the mass transfer is carried out according to its magnitude.
  • Some of the disadvantages of this type of aeration system refer 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 due to 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 sliding of gaseous particles, precisely in the area of the interface film, and on the other hand the volume confined per unit of generated area 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 are formed by concrete structural tanks, which are filled with a porous material-based packaging, which can 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 it reaches a thickness in which conditions arise, which allow it to be removed periodically by itself; the organisms in the film breathe the oxygen that exists in the holes formed; the drainage system allows the circulation of air up or down, depending on the temperatures of the influent and the porous medium, in order to improve the oxygen provision, 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 high load or low load units respectively, at the top by means of a series of nozzles mounted on sprinkler tubes, which can be fixed or have rectilinear movement or circulate, depending on the configuration of the tank; microorganisms receive food from the liquid that drains over the surface; There are currently materials, which can provide 40 to
  • An advantageous feature of this type of system is its ability to withstand sudden variations in organic load; It is also necessary that, in low load systems, a percentage of nitrification is carried out, which is due to the fact that there are types of nitrifying bacteria that develop adhered to the contact surface, for having enough time and oxygen for its development.
  • the main disadvantage consists of the large spaces, which are required for the construction of the structures; maintenance to restore operation, when flooding phenomena occur, is one of the most common problems that arise; Another effect that constitutes a disadvantage is the generation of conditions conducive to the development of flies.
  • Mechanical aeration system mechanical aeration is characterized by the use of electromechanical equipment, which works directly submerged totally or partially in the liquid, such as agitation by means of a propeller or a turbine, a vane agitator or a brush-type agitator from Kessner, which is usually installed over the course of a canal or ditch.
  • the agitator element fulfill two basic functions that are: agitation, in order to generate a certain interface surface, and secondly to provide agitation, in order to achieve a mixture that provides adequate contact, between the contaminating organic nutrients, the bacteriological organisms that will be responsible for metabolizing the organic matter and dissolved oxygen, which is transferred through the generated interface surface.
  • Another aspect that compensates for, the deficit effects of a large area of 5 interface and long contact times, in these cases, is the application of longer retention times, a concept that involves managing large structures, making this a disadvantage of economic type .
  • the main advantages refer to the excellent conditions of 0 concentration, both in the liquid and gaseous interfaces, which are very favorable, and the renewal factors are excellent in both the liquid and gaseous systems, to the extent that they compensate for the deficits of a large interface area, or a long contact time.
  • Conventional aeration this consists of subjecting the sludge to the aeration process, which can be mechanical or of bubbles, during a certain period of time from 6 to 8 hrs; recirculating, from 20 to 30% of sludge, which is mixed with the influent;
  • the conventional process may be provided with a primary sedimentation stage, and a secondary sedimentation stage. 5
  • Staggered aeration In this system, the influent is distributed in several points of the tank, and the recirculated sludge is introduced at the initial point, where the influent's waters are entered, this implies that the concentration of solids is greater at the beginning and decreases, at as the waters go or moving towards the other stages; With this modification it is possible to reduce the retention time by up to 50%, as long as the residence time of sludge is handled between 3 to 4 days, in this process the basic aeration system is by means of bubbles, although it can also be Mechanic in some cases.
  • Graduated aeration This process has the peculiarity of assuming that the largest BOD is at the beginning of the. tank, and it decreases as it progresses, so that a greater injection of air is made at the beginning, and it decreases as it approaches the effluent outlet, in this process the basic aeration system 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 BOD depletion, therefore the process can be applied with bubble aeration systems and mechanics.
  • Aeration activated here the excess sewage sludge is channeled, mixed with raw sewage, subjected to aeration to condition them and thus maintain a source of active sludge, which allows intensifying or restoring the continuity of biological activity, when it is affected by the introduction of toxic substances, or sudden overloads that inhibit biological activity;
  • the basic aeration process can be mechanical or bubble.
  • Classified aeration method consists in subjecting the sludge within a treatment system, to any compatible aeration process, but with recirculation of previously classified sludge, that is, it will no longer be recirculated discreetly, based on the following:
  • Light sludge these are constituted by fine particles that have the lowest sedimentation rates, which can be of organic matter, partially stabilized matter, or that has been assimilated in the generation of new bacteria, also small flocs formed by bacteria that initiate their development, which due to their size, they settle along with light sludge; All this makes light sludge the most biologically active, a quality that must be considered, to handle them more conveniently within the plant.
  • the objective of classified aeration is to contribute to improve the operation of treatment plants in the following aspects:
  • the inert bacteria which are the ones that mainly make up the largest and heaviest flocs, that is, the most stabilized ones, being these the ones that can be removed without running the risk of eliminating new sludge, and by recirculation, of the light sludge, it is guaranteed that the sludge in the process of development or new sludge, continue its development inside the tank, until they acquire the characteristics that can make them reach the section of heavy sludge.
  • Sludges that are channeled to be removed as excess sludge can be handled with less intense unpleasant odors, since they have been classified and They correspond to the most stabilized, so in case they are applied a final stabilization treatment, this will be with shorter retention times, and by the same degree of stabilization, the concentration or thickened operation is facilitated more, for its post treatment that can be drying in sand beds.
  • Capillary aeration system as such; It consists of a set of ducts that form plates or sheets of ducts, which can be manufactured with environmentally resistant covers, such as high density polyethylene and PVC, this system provides most of the oxygen that the process demands, since a Small part of oxygen is transferred on the surface of the oxidation tank, by the action of a small-scale mechanical aeration system, which is applied for mixing purposes to facilitate the contact of 0 2 , bacteria and contaminating organic matter, in addition to achieve a complementary aeration within the same tank;
  • the set of ducts 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 duct internally, this is achieved through the design of flow deflectors, which are illustrated in the following:
  • Figure 1 plan view of a flow deflector, within the capillary duct.
  • 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 section of a flow deflector.
  • baffles The ducts formed by PVC sheets (No 1), inside which are inserted a series of baffles (No 2), which can be of the same material as the duct, or a soft rubber to allow the introduction of a tool , to uncover if any type of plugging;
  • baffles are attached to the duct sheet, by means of the baffle support (No 3), these baffles provide several features that are described below:
  • This system is one of the most manipulable treatment systems, and also predictable, allow to vary flow conditions in the liquid system, flow conditions in the gas system and biological conditions of the sludge that is recirculated, all these variations can be managed independently to be studied, they can be observed and measured, so that 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 due to 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 at the interface surface, intermolecular forces are in imbalance, so this surface will be more receptive to the OD; Due to their handling characteristics, it is clear that the effects of limitation, as they are confined volumes, as in the case of bubble systems, can be compensated here with the injection of more air, without considerable increases in energy or, of higher dosage of liquid.
  • the capillary aeration system has a novel feature, which refers to the possibility of designing and building an aeration system, which allows taking advantage of both the upper and lower surface of a duct, according to the profile shown in fig. 2, with this, the contact surface of the interface is increased by the use of the entire possible surface, that is, the liquid flows throughout the inner periphery of the pipeline, this can be generated thanks to the surface tension property of the water , which allows it to slide over the upper surface, under certain conditions of slope and roughness, allowing a second internal gaseous flow to pass, such that the oxygen concentration in the gas interface is improved, at levels that favor oxygen transfer, with Low power consumption
  • 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 capillary duct sheets.
  • Fig. 18 shows the behavior of the concentration, in the liquid system within the capillary aerator, first of all, the graphs (No 3), represent the variation of the concentration in the liquid interface films, which have a period of time, which It is a function of the contact time and the surface renewal factor, each cycle of these graphs starts with a corresponding Ctil concentration, to which the liquid sheet has 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 oxygen concentration, in the liquid sheet inside the duct, the initial concentration of this graph is the Cio concentration of oxygen, which is normally maintained as an average in the biological oxidation tank;
  • the Clt (No 15) output concentration is that which is reached in the time of (No 8), in the liquid film inside the duct it can reach the saturation concentration Cls (No 1) in a time tls ( No 9) if you have enough length in the ducts, or the conditions of availability of oxygen and the thickness of the liquid film allow it, but
  • the graph (No 6) shows the time (No. 10), which would take the system to reach 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 tank volume, is what is commonly known as retention time TR, if this time is divided by the time required for saturation of the volume of the tank, this will indicate the number of times to be saturated, completely the volume of the tank , to meet the BOD demand of the tank volume;
  • the graph (No 7) serves as a reference point, since we will always try to provide sufficient oxygen to achieve the metabolism of BOD, contained in the daily volume, in the unit of time (No 12), which is usually one day, this serves 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
  • Fig. 19 represents the behavior of the gaseous system, within a treatment system, where the transfer takes place through a contact surface, so that the mathematical model of the interface films is applicable, which can be deduced from the figure in question;
  • the graph (No 4) represents the behavior of the oxygen concentration, in the atmospheric air inside the capillary duct, where in an analogous way, if it is of sufficient length and the conditions of the liquid system allow it, the oxygen concentration can decrease up to a concentration Cgs (No 2) in the time tgs (No 6), it is also necessary that in the gas flow, within the conduit the concentration Ctg (No 9) can be reached in the contact time TC (No 5), which may be the same as that used in the liquid system;
  • the graph (No 3) represents the behavior of the concentration in the gas interface, which begins in each cycle with the concentration Ctigo, which has the gas flow, within the duct at that precise moment; The gas flow will always start with the concentration of atmospheric air.
  • the factors that determine the flow turbulence, and with it the surface renewal factors are: the thickness of the flow sheet, the slope of the sheets, the number of baffles as well as the interior dimensions of the duct, all this allows manipulate or vary the Reynolds number, which is an indicator of the turbulence conditions being handled; the way in which the energy dissipates, is producing turbulent conditions precisely in the entire liquid film, to achieve high transfer rates, with lower energy consumption, than in the mechanical aeration systems, and with retention times Lower; the energy that is supplied to the fluid begins to be released in the descent of the liquid, developing a flow rate, which is a direct function of the slope and the roughness conditions, equivalent of the diffusers that have three specific functions, induce the formation of the upper fluid sheet, increasing the interface surface, It limits the speed of the flow, improving the contact time and helping to increase the turbulence, favoring the renewal of the interface limit film.
  • transition flow in this type of flow, the liquid film of the interface zone, begins to renew slowly, so that it is very feasible that there is a Reynolds number, which limits the laminar flow in order to establish the transfer that occurs in 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 involved in a given system.
  • Vi Speed with which the interface moves in m / s.
  • this speed depends on the slope of the ducts, the density of baffles per unit length, the thickness of the flow sheet and the kinematic viscosity of the fluid, the indicated speed corresponds to a specific design , driving water at 20 ° C with a slope
  • Vd Daily volume in m / day of sewage.
  • NC Number of ducts.
  • 0.048 and 0.08 are the interior dimensions, intended for the passage of gas flow in a given duct.
  • the kinematic viscosity considered for the liquid is: 0.00000101 m / s
  • the kinematic viscosity considered for air is: 0.0000135 m / s
  • the thickness of the gas interface film is determined based on the flow provided by the required transfer, based on the utilization coefficient of each type of system.
  • the velocity constant K is a function of the diffusion coefficient of oxygen in the liquid, the thickness of the film considered, the varying concentration conditions, and of the surface renewal factor of the FRS system, and of a Kp factor, which represents the number of times, the oxygen diffusion coefficient, referenced at 20 ° C and at sea level, is multiplied by the level of saturation in the interface zone; Considering all these aspects, it is necessary that the rate constant in the oxygen concentration change, in the flow sheet inside the duct is:
  • Kdlc Speed coefficient with which the oxygen concentration change is made, in the liquid system within the ducts.
  • the value of the oxygen coefficient must be referred to the average operating conditions of the process where it is applied, considering the temperature and concentration of suspended solids.
  • Ecl Thickness of the liquid layer inside the capillary duct.
  • FRIG Renewal factor of the interface surface in the gas system, has dimensions s "1 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 gas system, and it can increase up to a value determined by the turbulence conditions induced by some means.
  • Kpl Adjustment factor that allows to adjust the mathematical model, developed for the liquid system, represents the number of times that Kd is multiplied due to the concentration conditions.
  • FRIL Renewal factor of the interface film in the liquid system, which has dimensions s "1 and depends on the flow conditions, that is, its minimum value must be 1 and corresponds to the static conditions or laminar flow At the transition flow, its optimum value will be when the turbulence conditions are provided that provide the highest transfer rate in profitable conditions.
  • Kdgc - Kdg x FRIL x Kpg Ec 20
  • Kpg Adjustment factor that allows to handle the mathematical model developed for the gas system, represents the number of times that Kd is multiplied, due to the oxygen concentration conditions in the gas system.
  • the coefficient 0.84 is based on the consideration, that the conditions that occur in bubble aeration systems are similar in terms of the way in which the transfer is carried out, but with their respective characteristics each, so It is considered that, on equal terms, 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 uses 100% of usable oxygen, in.
  • the system only takes advantage of 16% of the atmospheric oxygen that passes through the system;
  • this coefficient differs when there are changes in the equilibrium conditions, from the stresses on the interface surface, which determine the intensity of the surface tension, due to the forces of Van der Walls, which is very feasible , and in the event that this hypothesis is confirmed, it would be positive as shown by 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 to the favorable concentration factors, to the condition of imbalance of the intermolecular forces, characteristics on a flat surface of a liquid such as water and that determine the surface tension, because as some studies of physics, the spherical surface of a drop or a bubble, they represent a surface whose efforts due to Van der Walls forces are balanced, which implies very rigid surface structures that can constitute a resistance, to a certain transfer being made through it, and of course, it is also very This structure is likely to represent a resistance to the surface renewal process, causing the transfer to be
  • the aeration system is capable of transferring 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, some proposed values have been estimated in the capillary systems, so a practical application should be supported with laboratory tests.
  • nterfase area which in the case of capillary systems, is the internal area of the conduit in operation, which limits the liquid system of the gas system, is determined as follows:
  • ANC Nominal duct width.
  • HNC Nominal duct height
  • ENLF Nominal thickness of the flow sheet, without baffles.
  • LRL Actual length of duct sheet.
  • the interface surface may have changes, such as the height of a bubble aeration tank, or the radius equivalent of the surface area of a mechanical aeration tank, or the length of the capillary ducts, through which changes in the interface surface are presented, to consider the relevant variations for each case, that is, the change is analyzed which manifests the surface within 1 s of this path; 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. deep, the contact time would be 23 s; in the case of ducts with a density of 3 deflectors per m. in length, driving a
  • Another concept involved is that which refers to a correction factor for the interface area, which, in the case of bubbles, depends on the difference in pressure, to which the air is injected and the pressure at which it is released, which corresponds to atmospheric pressure;
  • the analogous factor for capillary aeration systems is to establish a correction to the original area, produced by the structure of the duct walls, depending on the thickness of the liquid fluid sheet, and the variations that will occur, when develop a growth of biological film, on the inner walls of the duct; although it is sought not to promote this film when working the system continuously, and not to allow light infiltration, so that the surface of the ducts will generally be submerged, preventing the bacteria that develop attached to the walls, do not find the conditions conducive to your development; assuming that some biological development could occur, this can be limited by maintenance actions, when a film of 0.004 meters is presented, although it is feasible that these conditions do not occur, it is assumed that in case of certain bacteriological development, this behaves in the same way, as it behaves
  • the retention time is the time that the waters in process are subjected, 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 admitted in the effluent, making a study comparison between bubble aeration systems, a mechanical aeration system and classified capillary aeration systems, and given that the magnitude of the interface area is considered to be reasonably exceeded to the mechanical aeration system in the extended aeration mode, and assuming that the conditions of concentration, and interface surface renewal, are the most suitable for having a high oxygen transfer rate, and with an adequate culture of microorganisms, the estimated retention times will be between 6 and 12 hrs, depending on the objectives and conditions of each case.
  • TR Retention time in s.
  • Catm O 2 concentration in atmospheric air in mg / l.
  • % 0 2 d Percentage of atmospheric oxygen, which biological treatment systems can provide.
  • % 0 spicya Percentage of oxygen available, which is used by the treatment system with the conditions of each system.
  • the instantaneous air flow is determined by:
  • BODI oxygen transfer rate that is, the demand that the waters in process, or, that the system must handle in Kg 0 2 / s, and which is determined by:
  • BOD is the biochemical demand for oxygen in Kg 0 2 / m of sewage
  • the instant transfer rate can also be obtained from the following equations:
  • TTL and TTG in mg / (l x s), Ac in m / m, VI and Vg, in m / s, TR in s and Ecl and Ecg in m.
  • Kg O The amount of oxygen in Kg 0 2 that is required to lower the BOD, of the volume of sewage entered in the TR period, for practical purposes can usually be determined experimentally in a laboratory, not to rely on bibliographic references, for the reason of that the physical chemical and biological characteristics of water change from one place to another, theoretically, the Kg O can be calculated by.
  • TTLO TTL x (ai x VI x TC x TR x Ecl) / 1000 Ec 31
  • VI Speed of liquid flow inside the duct, in m / s.
  • Vg Speed of the gas flow inside the duct, in m / s.
  • Ecl Thickness of the fluid sheet inside the duct in m.
  • Ecg Thickness of the gaseous sheet inside the duct in m.
  • the rate of change of oxygen concentration in the liquid gas system would be determined by:
  • FCIL Concentration factor in the liquid interface, which normally has an initial value of 1 and will vary depending on the conditions of each system.
  • FCIG Initial concentration factor in the gaseous interfaces, this factor is dimensionless and will have an initial value of 1, for most cases, this factor, in capillary aeration systems, usually decreases to longer duct lengths, depending on the conditions of each system.
  • (Catm -Cgs) Equations 41 and 43 represent the mathematical model of the behavior of the liquid system as can be seen in fig. 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; mass transfer 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 surface renewal conditions, 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 interface film segment, which as you can see, each cycle is different in the first place because the initial concentration Ctil is increasing as the liquid sheet moves; the speed with which the transfer is carried out is not constant and finally the reference frame that corresponds to the concentrations of both one system and the other changes with respect to time, so that the constants used in the equation must consider all these adjustments; Cls saturation concentration (No 1) is a transfer limiting factor
  • Equations 42 and 44 represent the mathematical model of the behavior of the gas system as can be seen in fig.
  • the transfer capacity depends on the flows of liquid and gas, which are channeled to the set of ducts, to form the surface of the liquid and gas sheet, with the appropriate thickness, in the
  • the management of the gaseous flow does not have any handling problem, due to the low amount of energy that its management requires, referring to the liquid flow, this requires greater care in the analysis, due since it is the means of transport of dissolved oxygen, which is transferred to the oxidation tank, so that the flow of liquid must be sufficient so that the flow of oxygen is as required, and does not have obstacles due to the concentration of sewage, to operating conditions such as temperature among others;
  • the efficiency of the system will obviously depend, on handling the lowest concentration at the entrance of the ducts, to achieve the greatest difference with the liquid outlet concentration, it will depend on achieving the longest possible contact time, and on the greatest possible turbulence but with the slope that implies the lowest height, so that the energy consumption is the lowest possible.
  • the purpose of the sieve design is to strain the influent's 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 decreases the BOD, by separating a certain amount of organic matter in the form of small suspended solids, which if introduced into the aerators could possibly cause blockages in the capillary systems; on the other hand, if the aeration system has the capacity to provide sufficient oxygen, to process these solids biologically, they can go through a crushing process and return them to the treatment, so as not to cause a large amount of untreated organic solids, which can cause contamination problems, proper management of these could be drying in the sun for subsequent incineration, or bury them in previously sealed pits, then close them and by an anaerobic process cause degradation; in this way, the oxidizing capacity of the treatment plants that could be applied to these solids is used to achieve better effluent quality; the design of the screen, considers that the structure is balanced
  • FIG 9 plan view of the screen.
  • Figure 10 side view of the screen.
  • Figure 11 front view of the screen.
  • Its operation consists of entering the waters, through the inlet pipe (No 3) to a landfill box (No 1), which distributes all the inlet flow, along a landfill plate;
  • the sieve is designed in such a way that the waters fall directly to the aeration tank, the waters that leave the spout, fall to the sieve (No 2), all separated solids skid over the sieve and fall into a wheelbarrow, where periodically they are removed for later handling;
  • the screen box has a purge (No 4), which has the function of maintaining cleaning and unwrapping if 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 invariably be stainless steel.
  • Mechanical stirrer It is an optional element, which in certain circumstances, can provide agitation, to prevent the formation of sediments in the oxidation tank, can reinforce the mixing action, or it can add by agitation, a complementary transfer of oxygen, this element, is illustrated in the following:
  • Figure 12 plan view of the mechanical agitator.
  • Figure 13 front view of the mechanical stirrer.
  • Figure 14 side view of the mechanical stirrer.
  • the agitator has been designed to suction a flow vertically and project it horizontally, to induce mixing or agitation within the capillary aeration tanks, optionally it can provide a complementary aeration within the classified capillary aeration process, for the treatment of sewage , where it is required to direct 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 the propeller (No 2) is housed, formed by blades, which they are solidly screwed to a blade holder, which has a cradle that solidly fixes the arrow, which is moved by the gearmotor (No 3), which can be replaced by a speed variator, to be able to supply a larger 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 propeller blade is:
  • the design attack angle is in the following range:
  • Qag Flow generated to create the required mixing conditions, approximately 60 Ips for each Ips to be treated in case it is required to achieve an additional oxygen transfer, the corresponding analysis should be done.
  • Vtan mean tangential velocity, which for practical purposes is considered the tangential velocity of a point, located 2/3 of the center of the propeller towards the end of it.
  • Vtan RPM / 60 Dme x p ⁇ Ec 48
  • the manometric height developed by the propeller is given by:
  • the acceleration of gravity is: 9.81 m / s.
  • the length of the blade is a function of:
  • DHE outer diameter of the propeller.
  • the power transmission capacity of the arrow is given by:
  • PHE depth at which the propeller is in m.
  • the power demand of the propeller is given by:
  • Ef Volumetric efficiency of the propeller, considering approximately 0.8. Functioning:
  • Assorted capillary aeration tank consists of an aration system, which is illustrated by fig. 8, this works as follows:
  • FIG. 15 shows a flow chart, where a treatment system is schematically represented, based on capillary aeration with recirculation of 2 strata of classified sludge, of a single stage, to remove the carbonaceous matter, which is described below:
  • the influent enters through a sieve of solids (No. 7), reaching the oxidation tank (No. 1), in this tank, where the waters are aerated and agitation is provided to have adequate mixing, in addition to that optionally, a greater amount of energy can also be dosed to generate a complementary aeration; after having received sufficient aeration, the treated liquor passes to the sedimentation tank (No 2), provided with a sludge sorting system, where the aerated liquor is clarified; the clarified water leaves the settler through the outlet pourer (No 5), towards the next stage that will usually be a tank where chlorine is applied, in order to eliminate pathogenic bacteria;
  • the classification of sedimented sludge is in two strata, which are: heavy sludge (No 6), which 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 by a branch in section (No 3) of
  • FIG. 16 shows a flow chart, where a treatment system is schematically represented, based on capillary aeration with recirculation of 2 sludge strata classified, in two stages, to metabolize or the BODC in a first stage, and a nitrification that starts In the first stage and complemented in a second stage, this process is described below:
  • the influent enters through a sieve of solids (No 11), when it comes to the first stage, or by going to the oxidation tank (No 1)
  • the intermediate and light sludge, sedimented in the first stage will be recirculated daily to maintain in the aeration tank of the first stage, very active biological conditions, the clarified water in the first stage of sedimentation , it 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 specifications of the treatment, it is feasible that the BODc is finished down and partially a good proportion of the BOD, the aerated liquor in this tank passes to the final settler (No 4), where the heavy sludge settled in this stage, can be recirculated daily to the first stage, for the reason that they will carry a good proportion of nitrifying bacteria, which are of a slow development and therefore, it is not convenient to eliminate them at this stage, since by recirculating them, it is possible to return all viable nitrifying bacteria, causing the nitrification to start from the First stage
  • a flow chart is shown, where a treatment system is schematically represented, based on capillary aeration with recirculation of 3 strata of classified sludge, of three stages, this process partially eliminates a quantity of the BODC, and a small part of the BOD in the first stage, in the second stage the remaining BODc is eliminated and gradually a greater BODn, in the third stage the elimination of the BODn is complemented;
  • the process is described below:
  • the influent enters through a sieve of solids (No. 17), arriving at the oxidation tank (No. 1), where the same conditions occur as in an aeration tank of a single stage system; After having received sufficient aeration to achieve the removal of a good part of the BOD, reaching a small part of the biochemical demand of the nitrogen organic matter (BOD), the treated liquor passes to the sedimentation tank ( No 4), provided with a classifying system of three types of sludge, where the aerated liquor is clarified in the first stage, the clarified water leaves the settler towards the second aeration stage (No 2), the heavy sludge (No 7) , sedimented in the first stage of sedimentation, together with the heavy sludge of the second stage (No 10), are recirculated or are removed as excess sludges moving towards a final stabilization stage or thickening for subsequent drying; the intermediate sludge (No.
  • the light sludge (No 9), the light sludge of the second stage (No 12) and the heavy sludge of the third stage, are recirculated to the first aeration stage, with the aim of generating a high degree of inoculation of both bacteria heterotrophic as nitrifiers of the first and second stage of nitrification, that is to say 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 sedimentator of the second stage (No 5), where, as already indicated, three types of sludge are obtained;
  • the nitrifying bacteria are retained, which, as already indicated, the heavy sludges that settle in this stage, are recirculated to the first stage, to promote nitrification from the first stage, and thus maintain a long time of residence, of the nitrifying bacteria that are of very very slow development, especially the nitrosomones that metabolize the ammoniacal nitrogen to nitrites; the light sludges are 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 pass 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 contaminants,

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  • Life Sciences & Earth Sciences (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Microbiology (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Aeration Devices For Treatment Of Activated Polluted Sludge (AREA)

Abstract

L'invention concerne un procédé de traitement par aération de surface et recirculation des boues classifiées, destiné au traitement des eaux d'égouts, des eaux municipales ou des eaux résiduelles, dans certains cas. Ce procédé de traitement comprend le dégrillage de l'influent par dégrillage des matériaux solides, pour les eaux brutes uniquement ; le pompage de recirculation des eaux à faible teneur en oxygène dissous du bassin d'oxydation biologique vers l'aérateur de surface ; l'injection d'air, à l'aide d'un ventilateur à ailettes, pour maintenir de fortes concentrations d'oxygène dans l'air, dans l'aérateur ; l'agitation mécanique permettant d'obtenir éventuellement une agitation, un mélange et une aération complémentaires ; l'aération de surface, permettant, lorsque la liqueur mélangée est recirculée et de l'air est injecté, l'obtention d'une interface liquide et gazeuse provoquant le transfert d'oxygène à l'intérieur de l'aérateur formé par des conduits de surface ; la décantation avec classification des boues, ayant pour objectif de ne pas recourir à des boues activées de façon discrète selon des caractéristiques qualitatives, cette étape étant destinée à la classification des boues, par pesage, en boues intermédiaires et légères, les boues légères étant recirculées et les boues lourdes étant recirculées ou retirées lorsqu'il y a excès de boues. Ce procédé de traitement permet de récupérer l'énergie potentielle perdue dans des cours d'eaux usées rapides, avec des dénivellations de 5 à 30 mètres, une économie d'énergie conséquente étant obtenue du fait que l'énergie de repompage et d'agitation diminue.
PCT/MX2001/000041 2000-06-23 2001-06-22 Procede de traitement des eaux usees par aeration de surface et recirculation des boues classifiees Ceased WO2002000558A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001269603A AU2001269603A1 (en) 2000-06-23 2001-06-22 Treatment of contaminated waters by surface aeration and recirculation of classified sludges

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
MXJL00000003A MXJL00000003A (es) 2000-06-23 2000-06-23 Tratamiento de aguas contaminadas, a base de aeracion capilar y recirculacion de lodos clasificados.
MXJL/A/2000/000003 2000-06-23

Publications (1)

Publication Number Publication Date
WO2002000558A1 true WO2002000558A1 (fr) 2002-01-03

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AU (1) AU2001269603A1 (fr)
MX (1) MXJL00000003A (fr)
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118634685A (zh) * 2024-08-09 2024-09-13 江苏育瑞康生物科技有限公司 一种细胞培养液制备装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3133130A (en) * 1959-09-24 1964-05-12 Dorr Oliver Inc Treatment tank for aerobically purifying waste liquids
US4961854A (en) * 1988-06-30 1990-10-09 Envirex Inc. Activated sludge wastewater treatment process
WO1992000249A1 (fr) * 1990-06-23 1992-01-09 Dunlop Limited Dispositif d'amenee de fluide
ES2144864T3 (es) * 1996-06-26 2000-06-16 Gb Odobez S R L Un reactor para la depuracion de aguas residuales contaminadas.

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3133130A (en) * 1959-09-24 1964-05-12 Dorr Oliver Inc Treatment tank for aerobically purifying waste liquids
US4961854A (en) * 1988-06-30 1990-10-09 Envirex Inc. Activated sludge wastewater treatment process
WO1992000249A1 (fr) * 1990-06-23 1992-01-09 Dunlop Limited Dispositif d'amenee de fluide
ES2144864T3 (es) * 1996-06-26 2000-06-16 Gb Odobez S R L Un reactor para la depuracion de aguas residuales contaminadas.

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118634685A (zh) * 2024-08-09 2024-09-13 江苏育瑞康生物科技有限公司 一种细胞培养液制备装置

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MXJL00000003A (es) 2002-08-29
AU2001269603A1 (en) 2002-01-08

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