MXPA97008640A

MXPA97008640A - New method for the control of biodegradac

Info

Publication number: MXPA97008640A
Application number: MXPA/A/1997/008640A
Authority: MX
Inventors: Helmo Kim; Heinen Nicolas
Original assignee: Biobalance A/S; Heinen Nicolas; Helmo Kim
Priority date: 1995-05-11
Filing date: 1997-11-10
Publication date: 1998-10-30

Abstract

The present invention relates to a novel method for controlling biodegradation, said biodegradation being carried out by mixed cultures of microorganisms. The measurements and the adjustment (preferably online) of the process parameters that relate to the metabolic activity of the microorganisms, are carried out in such a way that nitrification and denitrification are carried out simultaneously in the same environment, at the same time that the oxygen concentration is maintained below 1 ppm. The method allows the use of high concentrations of biomass (up to 20 kg / m3) and reduces the energy consumption and the volume of the process, for example of activated sludge processes, thereby saving costs for the purification of water from scrap In general, the process ensures optimal conditions for the microorganisms in the process. A method for the purification of waste water and a waste water purification plant are also described which employ the method for the control of bidegradation. Finally, a method is also described to determine the reference values that allow the control

Description

NEW METHOD FOR THE CONTROL OF BIODEGRADATION FIELD OF THE INVENTION The present invention relates to a method for controlling the biodegradation of aqueous media containing biodegradable material which comprises nitrogen containing components. In addition, the invention relates to methods for purifying such aqueous media. Finally, the invention belongs to a water purification plant, where these methods are used in the purification processes.

BACKGROUND OF THE INVENTION Nowadays, the protection of the environment is of great interest for humanity. Population growth as well as a general demand for superior quality of life, expressed as a healthy and beautiful environment and at the same time a lifestyle based on the use of advanced technology, has accentuated the need for water, especially water pure, throughout the world, but especially in the industrialized parts of the world. REF: 26127 In highly industrialized countries, especially countries with large urban concentrations, it is necessary to treat waste water from domestic and industrial production, to avoid an unacceptable level of contaminated and polluting material in the environment, for example, in deposits for waste water such as lakes, rivers and other waterways, the sea, etc. The contaminated and contaminating material comprises a variety of substances, for example organic and inorganic substances which may or may not be decomposed in nature. Among the contaminating material usually present in waste water effluents, decomposable organic material and heavy metals are of the greatest interest. An increasing amount of the waste water that is produced worldwide is now subject to some type of treatment, such as treatment whether mechanical, chemical or biological in nature, or any combination thereof. In general, it is expected to focus increasingly on wastewater treatment in the future, as the public interest in environmental hazards is becoming increasingly strong today.

The main purpose for purifying, for example municipal and industrial waste water, is to reduce the content of biodegradable material in the waste water, for example, to ensure that the waste water treated does not contain quantities of biodegradable material, for example organic matter. and / or inorganic biodegradable, such that these quantities lead to an unacceptably low level of oxygen in the tank, due to the amount of oxygen required for the aerobic decomposition of the degradable (organic) material. The elimination of biodegradable material is often done by including some type of biological treatment step in the water purification process. Normally, complex cultures of microorganisms are used to effect biodegradation (since microorganisms metabolize the biodegradable material and thereby use it as a source of energy) and the result is a conversion of the biodegradable material into environmentally acceptable compounds such as C02 and N2 . It is especially desired to reduce the amount of organic matter and at the same time reduce the amount of nitrogen-containing components present in the waste water.

Such removal of the nitrogen-containing components from wastewater has proved difficult and resource-consuming. The goal is to convert the nitrogen bound in the nitrogen-containing components of the wastewater into gaseous (atmospheric) nitrogen, and this is traditionally done by the nitrification steps (one oxidation step) and denitrification (one reduction step). Prior to these steps, complex nitrogen-containing substances are deamidated, for example, by the desaasas produced by the microorganisms (or optionally supplied to the system in question) and the remaining major problem is thus to convert the ammonia to nitrogen gas. Numerous attempts have been made to improve the elimination of nitrogen in the purification of waste water. The general scheme is the following: Nitrification: NH + 4 + 02"» NO " Denitrification: NO "3" > N2 - or more specifically, nitrification involves the reaction NH + 4 + 202 - * NO "3 + 2H + + H20 and denitrification involves the reaction NO ~ 3 + Ared •> sN2 + A0 ?, where ArTd and Aox are the reduced and oxidized states, respectively, of a compound which is oxidized in parallel to the reduction of N0"3 to N2. Both reactions are facilitated by microorganisms, which are responsible for biodegradation, but since nitrification is facilitated by high oxygen concentrations and denitrification is facilitated by low oxygen concentrations, all methods known to the present inventors rely on in one of the following two principles: A) The biodegradation process is subject to intermittent aeration, whereby the two processes are substantially non-simultaneous. An example of such processes is described in U.S. Patent No. 5, 304, 308. B) Biodegradation is compartmentalized, in such a way that some compartments have a high concentration of oxygen, while others have a low concentration of oxygen. Examples of such processes are described in European Patent EP-A-218,289 and European Patent EP-B-233, 466. It should be clear that alternative A) is time consuming. The processes of the prior art that use this alternative also consume energy, since the supply of oxygen to the system requires a lot of energy for the operation of the aeration pumps, the agitation means, etc. Alternative B) overcomes the problem of time consumption at the expense of space consumption. The mere fact that there is a spatial distribution of differently aerated zones, must make it clear that much space is needed for the process to occur, and therefore such processes are mainly used in large-scale water purification. In addition, the biodegradable material must be transported from one compartment to another, in order for the process to be successful, and therefore alternative B) normally requires that means of transportation be present in the system. As for alternative A), the energy requirements are high. These two types of processes of the prior art suffer from additional drawbacks. Mixed cultures of microorganisms that are responsible for biodegradation are sensitive to changes in their environment. If the concentration of oxygen is very low, the composition of the biomass will be adapted in a direction that favors the anaerobic processing of the biodegradable material, for example the anaerobic bacteria will be more abundant than in the aerobic environment. The opposite is of course true for situations where the concentration of oxygen is very high. Therefore, in the known processes, the composition of the mixed cultures will never, or almost never will be optimal with respect to the nitrification process or the denitrification process, since it takes a certain time before the crops have been adjusted for one of the processes. In other words, large quantities of bacteria do not take part in the process, which is currently "desired" at a certain point in time, since they are not able to carry out the process properly. In addition, when an operation is used that requires differences for example in aeration (either in time or space), problems arise with respect to the determination of how long the waste water should be processed under each of the two groups of conditions, since the waste water that enters will have to be satisfactorily nitrified in the nitrification phase before the denitrification phase is instituted. In situations where the load of waste water is low, no problems will arise, but at maximum loads, the plant has to be of adequate dimensions, so that the water that enters can be stored for a sufficiently long period of time in both cases. In other words, the purification plants operated according to the methods of the prior art have to be conditioned to scale for the worst possible situation, for example, a maximum load, since all the material in the contaminated water that has been nitrified It has to be guided towards the denitrification phase.

OBJECTIVE OF THE INVENTION In light of the above discussion, an object of the invention is to provide the methods to be used in the biological purification of aqueous media (such as waste water), the resulting purification being such that the amount of biodegradable material is simultaneously decreased with the elimination of the nitrogen-containing components in the water, without the method suffering from the drawbacks of the prior art methods with respect to energy demands, space consumption, etc.

DESCRIPTION OF THE INVENTION It has surprisingly been found by the inventors that it is possible to achieve simultaneous nitrification and denitrification in an aqueous medium containing biodegradable material, which comprises the nitrogen-containing components (such as, for example, waste water) which is subject to biodegradation, without having to divide the volume into zones, which favors nitrification or denitrification, respectively. This result can be achieved by careful control of the living conditions of the microorganisms, (for example, the metabolic activity of the microorganisms) in such a way that their metabolic activity is maintained within a narrow range, which surprisingly allows the simultaneous processes of nitrification and denitrification are carried out by the microorganisms. This narrow range is system specific, and therefore will often have to be predetermined for each system, where such biodegradation is taking place. However, the present inventors have discovered that the processes will be efficient only when the oxygen concentration is maintained below 1 mg / liter (below 1 ppm), even in the best agitated and oxygenated parts of the aqueous medium where the microorganisms they carry out the processes. The realization by the inventors that such a narrow range of metabolic activity of microorganisms exists has made possible the development of novel methods for controlling biodegradation by microorganisms, in order to optimize the efficiency of biodegradation. In addition, novel methods for the simultaneous nitrification and denitrification of aqueous media containing biodegradable material have been developed, and purification plants employing the aforementioned methods have finally been invented. Therefore, a part of the invention relates to a method for controlling the biodegradation of the biodegradable material, which comprises nitrogen-containing components, the biodegradable material being contained in an aqueous medium, and biodegradation by the microorganisms being effected, the The method comprises: evaluating the value of at least one parameter of the metabolic activity (evaluated value) in the aqueous medium, comparing the evaluated value with a predetermined range of values or a predetermined single value of at least one parameter of the metabolic activity , which represents the metabolic activity of the microorganisms which biodegrade the biodegradable material, the values in the range or the unique value are those that indicate that the microorganisms will perform an effective nitrification and denitrification of the biodegradable material contained in the aqueous medium, and after this if the evaluated value falls outside the range or is different from the single value, at least one parameter is adjusted that has an influence on the metabolic activity of the microorganisms, in a direction that tends to move the evaluated values subsequent to the interval or towards the single value, and ensures that the concentration of oxygen in the aqueous medium is maintained below 1 mg / liter, while nitrification and effective simultaneous denitrification take place. The fact that simultaneous nitrification and denitrification can be carried out at oxygen concentrations below 1 mg / liter, it is highly surprising. It has been considered until now as a fact established in the art, that the nitrification carried out by microorganisms requires high oxygen concentrations (usually above 1.5 mg / liter) in order to be effective, see the German standards ATV-A 122, ATV-A 126 and ATV-A 131. When the term "method of the invention" is used herein, it refers to the method for controlling biodegradation, unless otherwise indicated. It is preferred to only compare with a predetermined value, or alternatively, when a range of values is used, to adjust the controlled parameter in the direction of a specific value in the range (e.g., the average value in the range). As used herein, the term "control" denotes the act of deliberately regulating or influencing one or more variables of a process, based on measurements of one or more of the process variables. The last or last variables is / are denoted measured variables, while the first (s) mentioned variable (s) is / are denoted conventionally a) controlled variable (s). The desired numerical value of the controlled variable is referred to as the reference point, while a change in any variable that can cause the controlled variable of the process to change is called the load. As used herein, the term "biodegradable material" refers to the organic and / or inorganic matter which is biologically feasible to decompose, such decomposition taking place by subjecting the organic and / or inorganic matter, especially the organic matter, to a transformation process effected by the crops of microorganisms (for example, mixed cultures), the transformation process taking place in an aqueous environment, for example water, waste water, drainage, lake water, sea water, river water and the like. The microorganisms use the biodegradable material present, as a source of nutrition and / or energy, thereby converting the biodegradable material to additional biomass and to end products of metabolism, such as nitrates, nitrogen gas, sulphates, phosphates, carbon dioxide, etc. The amount / concentration of biodegradable material in an aqueous phase is within the technique of waste water purification, conventionally measured in terms of Biochemical Oxygen Demand (BOD). BOD is a measure of the amount of oxygen required for the aerobic decomposition of organic materials, since the BOD evaluates the oxygen demand of the microorganisms that carry out the decomposition. Alternatively, the amount / concentration of biodegradable material can be expressed as the Chemical Oxygen Demand (COD). COD is also a measure of the amount of oxygen required for the aerobic decomposition of organic materials, but here the oxygen demand is evaluated for a purely chemical oxidative decomposition of the organic material. As described in European Patent EP-B-461166, it is also possible to determine the amount or concentration of biodegradable material by performing fluorescence measurements of the biogenic fluorophores present in the microorganisms that biodegrade the biodegradable material. In all aspects of the present invention where measurements of the amount or concentration of the biodegradable material are made, it is preferred to use the latter method for the determination of the amount or concentration of the biodegradable material, for example, the method described in European Patent EP-B-461166 (and in the corresponding North American Patent No. 5,506,096).

By the terms "nitrogen-containing substances" and "nitrogen-containing components" is meant in the present ammonia, nitrates, nitrites, proteins, amino acids, purines, pyrimidines, nucleic acids, nucleosides, nucleotides and other organic / inorganic compounds containing nitrogen . The term "biodegradation" (or biological treatment) refers in this way to the process of microorganisms that metabolize the biodegradable material present in an aqueous medium. In essence, such biodegradation takes place inside, as well as outside of microorganisms. High molecular weight compounds (such as long hydrocarbon chains) or other compounds that are not easily transported through the membranes of microorganisms, can not easily enter the microorganisms but rather are partially degraded in the extracellular compartment by the secreted enzymes. The resulting material can then enter the cells where it is metabolized into energy and into final products such as C02, N2, etc. In the technique of waste water purification, the aqueous medium is introduced into a tank, pond or the like which normally contains mixed cultures of microorganisms, for example activated sludge (biomass), wherein the biodegradable material in the aqueous medium to be treated, it is degraded by the microorganisms present. Thus, the expression "biodegradation that is effected by microorganisms" reflects the fact that the microorganisms are responsible for the conversion of the biodegradable material into any of the previously described routes. The term "aqueous medium" as used herein, refers to a liquid containing water as the predominant basic constituent, preferably more than 80% by weight, more preferably more than 90% by weight, especially more than 96% by weight, for example more than 97% by weight, still more preferably more than 99% by weight of water, the liquid being able to act as solvent and / or dispersing medium, and thereby be able to comprise soluble and / or insoluble and / or suspended and / or dispersed substances, material and / or or mixed cultures of microorganisms as defined herein. Frequently, the aqueous medium according to the invention will be selected from waste water such as municipal waste water or industrial waste water, purified waste water, surface water, especially surface water for use as tap water, water from wastewater. sea, contaminated seawater, or other aqueous systems containing biodegradable material, as defined herein. As used herein, the term "waste water" is used as a common designation for aqueous effluents containing organic and / or inorganic substances which are present or are formed in an environment as a consequence of the presence and / or activity of human beings, including industrial activity in its broadest sense which, for example, includes domestic and industrial activity, agriculture, forestry and fishing industry, and which one wishes to treat to obtain purified water with the main purpose of maintain and / or improve the environment and / or provide a production of purified water which can be reused as tap water. Typically, waste water is produced constantly or seasonally. The term "effective simultaneous nitrification and denitrification" is intended to denote that the aqueous medium is subject to biodegradation by microorganisms, which results in the simultaneous production of 1) nitrates from nitrogen-containing substances and 2) gaseous nitrogen from nitrates.

The term "effective" in this context, denotes that the final result must be that the aqueous medium has a total concentration of nitrogen after biodegradation of at most 8 mg / liter. According to the invention, the microorganisms are all subject to substantially the same conditions (for example, it is sought that the metabolic level is maintained substantially at the same level in all parts of the aqueous medium) which means that there is no intentional physical division of the medium aqueous, for example in areas of high and low concentration of oxygen, respectively, as is the case in the methods of the prior art. Therefore, when a purification process is controlled according to the invention for example in an aeration tank in a waste water purification system, the two nitrification and denitrification reactions take place not only at the same time, but also They take place in parallel in the tank. In this way, in contrast to the known methods for simultaneous nitrification and denitrification, the tank is not divided into zones, which favors either of the two nitrification or denitrification processes. In other words, it is intended that the living conditions of the microorganisms in the system be maintained substantially identical in the entire volume of the container (or at least in the part of the container where the biodegradation takes place) and with which an attempt is made to maintain a uniform distribution of the metabolic activity of the agglomerates of microorganisms, all on the container. By the term "microorganisms" is meant herein organisms such as autotrophic as well as heterotrophic and aerobic, anaerobic or facultative bacteria, as well as lower eukaryotic organisms such as protozoa, yeasts, fungi and other organisms usually present in the activated sludge in the step of biological treatment of a waste water purification plant, for example multicellular organisms such as Sl ipper animal cul (Paramaecium) and parasites, especially parasites that consume bacteria. In the waste water purification technique, the microbial system used in the biological treatment steps is usually a mixed culture of microorganisms. The term "mixed cultures of microorganisms" as used herein, refers to cultures that comprise a plurality, usually a wide variety, of microorganism species as defined above. The terms "activated sludge" or "biomass" are conventionally used for mixed cultures of microorganisms as defined above, which are present in the biological treatment step in order to degrade the biodegradable material, for example, especially the organic material and / or inorganic feasible to decompose. Such mixed cultures of microorganisms use the nutrition in the waste water to be treated, and with this they convert the organic and inorganic material to biomass and to final metabolism products such as nitrates, nitrogen, sulfates, phosphates, carbon dioxide, etc. This conversion can take place under anaerobic, aerobic or anoxic conditions. The effective composition of the mixed cultures of microorganisms can vary widely, since the composition is highly dependent on the prevailing conditions. The term "metabolic activity" as used herein, refers to the rate or rate of metabolism of microorganisms which are biodegrading into biodegradable material, for example metabolic activity is a quantitative measure of microbial activity. However, the term "metabolic activity" also encompasses a qualitative measure of microbial activity. In summary, there are two ways to use the energy that results from biodegradation, an anabolic and a catabolic. When microorganisms are in an anabolic state (for example, nutrient supplies are not limiting for the growth of microorganisms), these metabolize in order to proliferate, for example, the energy made available to microorganisms is converted into biomass. Alternatively, when the microorganisms are in a catabolic (starvation) state, they metabolize in order to produce for example enzymes in order that they subsequently degrade the biodegradable material, or in other words: in order to survive, substantially all the efforts of the microorganisms are directed to extract the energy of the biodegradable material. It will be understood that the method of the invention for controlling biodegradation is aimed at providing a favorable metabolic activity of the microorganisms, for example a catabolic state of the microorganisms which results in a high rate or rate of biodegradation (only small amounts of energy they are "wasted" in the anabolic metabolism of microorganisms).

However, in order to achieve the second goal of the invention, namely to provide a simultaneous nitrification and denitrification of the biodegradable material, it is necessary to control the parameters in the environment of the microorganisms in such a way that this is possible. It is believed that the method of the invention for controlling biodegradation results in an optimum or near optimum balance between 1) the biodegradation of the nitrogen-free components of the biodegradable material, 2) the nitrification of the nitrogen-containing components of the biodegradable material, biodegradable material and 3) the denitrification of nitrates produced as a result of nitrification. It is further believed that this optimum or near optimum balance is achieved because the living conditions of the different subgroups of microorganisms in the total population of microorganisms are adjusted by the method of the invention, so that each subgroup performs its part of the biodegradation at a speed and efficiency that is reached to optimize with respect to biodegradation, as well as nitrification / denitrification. Since the method of the invention is directed to providing a stable environment for the microorganisms, and thus ensuring a stable level and quality of metabolic activity in the aqueous medium, it is further believed that the composition of the agglomerates of microorganisms becomes relatively stable with respect to the relative numbers of different subgroups of species. The expression "metabolic activity parameter" denotes a measurable parameter to which a value can be assigned, and which can provide information regarding the metabolic activity of the microorganisms. The expression "parameter that influences the metabolic activity of microorganisms" denotes a controllable parameter which, when changed, results in the metabolic activity of the microorganism being changed. A metabolic activity parameter can also be called a "measured variable" or a "measured parameter", while a parameter that influences the metabolic activity of microorganisms, when controlled, can be denoted as a "controlled variable" or "controlled parameter". The parameters measured and the parameters controlled together are designated "process parameters". It will be understood that a measured parameter and a controlled parameter can be the same. This is, for example, the case when the value of a controllable variable is directly measured, as is the case when measuring the concentration of oxygen in the aqueous medium. If the oxygen concentration falls outside a concentration range that has been set to ensure simultaneous effective nitrification and denitrification, the oxygen concentration will be adjusted to be within the concentration range. In other cases, the measured variable and the controlled variable are not the same, for example, in cases where the value of the measured variable provides an indirect indication of the metabolic activity of the microorganisms. As discussed in detail herein, the fluorescence emission of biogenic fluorophores such as NADH and NADPH, is a preferred parameter of metabolic activity that is measured in the methods of the invention. However, in order to regulate the values of this parameter, other parameters in the system can be adjusted, such as oxygen concentration, etc. According to the invention, the measured parameter is preferably selected from the group consisting of the C02 concentration, the emission of fluorescence from biogenic fluorophores, the concentration of oxygen, the concentration of the biomass, the oxygen concentration / COD ratio , the loading of biodegradable material, the concentration of oxygen, the pH, the temperature, the turbidity, the rate of dosing of precipitation chemicals, the rate of dosing of the additional material containing carbon, easily biodegradable; the rate of dosing of substances capable of converting the non-readily biodegradable material to readily biodegradable material, the rate of recycle of activated sludge, the rate of inflow, the rate of outflow, the rate of agitation, the speed of oxygen dosage, the rate of air dosing (aeration), the total amount of activated sludge in the system, and other process parameters that are conventional in water treatment processes, waste water or the like. The evaluation of the value of the measured parameter can be carried out by methods known to the person skilled in the art. Examples of the preferred methods are measurements selected from the group of fluorescence emission measurements from at least one biogenic fluorophore, gas chromatography measurements, infrared measurements, turbidity measurements, nuclear magnetic resonance measurements, chemical measurements of ammonium, phosphates and nitrates, measurements of the redox potential, short-term measurements of the BOD, and chromatographic measurements such as HPLC and FPLC, and combinations thereof. Chromatographic measurements may involve principles such as size exclusion chromatography, affinity chromatography, ion exchange chromatography, etc. When evaluating the value of the measured parameter, it is preferred that this evaluation be carried out with the help of an online measurement, since this makes possible a continuous monitoring of the process and such rapid action can be taken (for example by means of automation) when the measured parameter falls outside the predetermined range or is different from the predetermined value. As used herein, the term "online measurement" denotes measurements that have short response times, which is the numerical value or the electrical signal obtained as a result of the effective measurement, is recorded substantially momentarily with respect to the process. The term "online automation system" is intended to denote a system comprising an on-line measuring equipment which is connected to the effector equipment capable of controlling a process parameter. The effector equipment is fed with the information coming from the online measurements, and controls the process parameter in an automatic way which is dependent on the input signal. Typical of such systems are the negative feedback systems, wherein a register of values of a measured parameter indicating a change of a controlled parameter, leads to automatic regulation of the controlled parameter, in the opposite direction of the observed change. According to the invention, it is preferred that the control of the controlled parameters be carried out by an on-line automation system. However, the monitoring of the measured parameters and the subsequent manual or semi-manual adjustment of the controlled parameters can, of course, be done when the amount of resources allows, especially in view of the fact that humans in some situations will react more appropriately. to changes in certain measured parameters than what a fully automatic system could do. It is preferred to measure the fluorescence emission from at least one characteristic biogenic fluorophore, such that the measurements make possible the simple, fast and reliable recovery of data regarding the metabolic state of the microorganisms.

It is especially preferred to use the in-line fluorescence sensor equipment. As used herein, the term "biogenic fluorophore" denotes a substance synthesized by living material (living cells), molecules of such a substance are capable of fluorescing when irradiated with light. Biogenic (biological) fluorophores include proteins, especially proteins that contain tryptophan and tyrosine, peptides containing tryptophan and tyrosine, amino acid derivatives that contain tryptophan and tyrosine, cofactors, purines, pyrimidines, nucleosides, nucleotides, nucleic acids, steroids, vitamins and others. In this context, NADH (nicotinamide adenine dinucleotide) and NAD (P) H are preferred examples of biogenic fluorophores. Other examples of biological substances capable of fluorescing are tyrosine, tryptophan, ATP (adenosine triphosphate), ADP (adenosine diphosphate), adenine, adenosine, estrogen, histamine, vitamin A, phenylalanine, p-aminobenzoic acid, dopamine (3,4-dihydroxyphenylethylamine), serotonin (5-hydroxytryptamine), dopa (3,4-dihydroxyphenylalanine), kynurenine and vitamin B12. The term "fluorescence" or the term "fluorescence emission" refers to the emission of radiant energy by a molecule or ion in the excited state. The molecule or ion reaches the excited state by absorbing radiant energy. The absorption of (or excitation by) ultraviolet or visible radiation causes an electronic transition (in 10"18 seconds), so that the molecule is excited from the electronic basal state to some vibrational sub-level of the first electronic excited state. of light is usually referred to as excitation.After excitation, the molecule must emit an amount of energy equivalent to that absorbed if it is to return to the electronic basal state.This energy can take various forms, for example light, heat, etc. When that amount of energy is emitted as light having longer wavelengths (lower energy) than the wavelengths of light used for excitation, and the time scale for this light emission is approximately 10" 8 seconds, then such emission is denoted as fluorescence. Each biochemical or chemical molecule (biogenic fluorophore) has a characteristic spectrum of excitation and fluorescence. Usually, the fluorescence spectrum or the fluorescence band is divided into two or more peaks or maxima, each peak occurring at a specific wavelength. To detect the fluorescence emission of a fluorescent molecule, it is necessary to detect this emission at a wavelength that is within the envelope of the fluorescence band for the fluorophore, preferably at a wavelength corresponding to a peak in the spectrum of fluorescence. Also, the fluorophore must be irradiated with light emitted at a wavelength that is inside the envelope of the excitation band for the fluorophore, preferably at a wavelength corresponding to a peak in the excitation band. The term "characteristic" as used in connection with the biogenic fluorophore (s), denotes that the biogenic fluorophore is one that is inherently produced by the living biological material in question, for example the mixed culture of microorganisms, in an amount that reflects the biological activity, for example the metabolic activity, of the living material. Typically, biogenic fluorophores are present as intracellular substances in microorganisms. The excitation peak and the fluorescence peak, respectively, of the important examples of the aforementioned fluorophores, appear in the following Table I: TABLE I Examples of Biologically Important Fluorescent Substances Peak of Excitation Peak Fluorescence (nm (nm) * tyrosine 275 303 3, 4-dihydroxyphenylalanine 345 410 * tryptophan 287 348 kynurenine 370 490 5-hydroxytryptamine (serotonin) 295 330 phenylalanine 260 282 3, 4-dihydroxyphenylethylamine 345 410 (dopamine) histamine 340 480 vitamin A 372 510 flavins 450 535 NADH and NAD (P) H 340 460 p-aminobenzoic acid 294 345 vitamin B12 275 305 estrogen 285 325 ATP, ADP, adenine, adenosine 272 380 * Responsible for the fluorescence of proteins It is preferred that in the practical use of the method of the invention, light is emitted at a wavelength greater than 250 nanometers, especially 250 nm-780 nm, for example about 340 nm, and the fluorescence emission is detected at wavelengths greater than 250 nm, preferably 250 nm-800 nm, especially 280 nm-500 nm, for example approximately 460 nm. The light with which the system is irradiated is suitably light emitted at a wavelength greater than 250 nm, and the fluorescence emission is preferably detected at a wavelength of 280-500 nm. The wavelength must of course be adapted to the particular system, in particular to the type of fluorophores present in the system. According to what is indicated above, the important modalities of the method are embodiments wherein the fluorophore is a nicotinamide adenine dinucleotide such as NADH or NADPH. In this case, the light is preferably emitted at a wavelength of about 340 nm, and said fluorescence emission is detected at a wavelength of about 460 nm. One reason to put much more weight in the measurements of these two fluorophores is that they are very susceptible to changes in the concentration of their oxidized counterparts NAD + and NADP +; even a fractional decrease in NAD * leads to an increase of many times in the concentration of NADH. In addition, the concentration of NADH and NAD + taken together in living cells is approximately 1 mM, corresponding to approximately 0.63 g / liter of cells, which means that a significant percentage of the dry matter in the cells is comprised of NADE and NAD +. By using the fluorescence measurements of NADH / NADPH it is possible to obtain information concerning the potential biological activity (BPA) of microorganisms. One unit of BPA is defined as the fluorescence intensity corresponding to the fluorescent intensity recorded from a solution of distilled water containing 1 ppb of coumarin at room temperature and at atmospheric pressure. When the range of values or the unique value of the parameter measured is previously determined, this is according to the invention, it is normal practice to employ empirical calibration, for example a biodegradation process is periodically verified with respect to its input and output values. the parameters of interest, and at the same time the values of the measured parameter are recorded. The value or default values is / are those that will lead to a satisfactory result. As an example it can be mentioned that a waste water purification process can be checked periodically with respect to its output of total nitrogen and BOD or COD. According to Danish legislation, the total nitrogen content in purified waste water must not exceed 8 mg / liter, and the BOD must not exceed 15 mg / liter. Therefore, when the range of values or the unique value of the measured parameter is previously determined, the values of interest are those that are correlated with such low values of nitrogen and BOD concentrations. In order to optimize the choice of values of the subsequently measured parameter, measurements of other process parameters such as energy requirements, the rate of biodegradation, etc., can also be incorporated in the evaluation. Hence, in the practical use of the method, it is frequently preferred to periodically check the values of the measured parameter (s) of the system during an initial test period and carefully periodically verify the effect of the increase or decrease treatment to reduce the biodegradable material, partly on the system itself and partially on the measured value, establishing in this way the correlation between the effect and the interaction between the controlled parameters, the condition of the system itself and the measured parameter, to identify the predetermined values with the highest precision. The preferred controlled parameters are, according to the invention, selected from the group consisting of the charge of biodegradable material, the concentration of oxygen, the pH, the temperature, the turbidity, the rate of dosing of the precipitation chemicals, the Dosing speed of the additional material containing easily biodegradable carbon, the rate of dosing of the substances capable of converting the non-readily biodegradable material to easily biodegradable material, the speed of recycle of the activated sludge, the speed of the inflow, the speed of the flow rate, agitation speed, oxygen dosing rate, air dosing rate (aeration), the total amount of activated sludge in the system, the concentration of the activated sludge in the aqueous medium, and other parameters of the process that are conventional in the processes of water treatment, waste water or similar. All of these controlled parameters are well known in the art as are the means to effect their direct control. Of these controlled parameters, the concentration of the activated sludge in the aqueous medium is of special interest: An advantage obtained by using the method of the invention is that, for example, an aeration tank that is controlled according to the invention can become more flexible with respect to the loads of biodegradable material that can be biodegraded and the excess sludge content can then be decreased. In addition, the concentration of sludge in the separation of secondary sludge is therefore greater. This is due to the fact that the concentration of the biomass in an aeration tank is normally between 3 and 7 kg / m3, while the biodegradation processes that are controlled according to the present method, can be carried out at concentrations of sludge in the concentration range as high as 10-20 kg / m3 (see Example 2). It is already known in the art that the "biosorption phenomenon" (for example the sorption of organic material by the activated sludge without biodegradation) can explain the removal of significant amounts of waste water, and it is also known that the properties of activated sludge it is an important parameter in this regard. The present findings indicate that the biosorption is increased when the flocs of microorganisms are controlled according to the invention, and that this phenomenon can explain the increased robustness of the systems with high concentration of sludge. Therefore, the floccules or agglomerates of microorganisms can absorb large amounts of biodegradable material entering, in a relatively short period of time and the process controlled in this way becomes less sensitive for example to a high load of waste water. Thus, a preferred embodiment of the method of the invention for the control of bisdegradation, the concentration of activated sludge is adjusted to be at least 3 and at most 20 kg / m 3. It is preferred that the concentration of activated sludge in this range be at least 5 kg / m 3, such as at least 7 kg / m 3, 9 kg / m 3, 11 kg / m 3, 13 kg / m 3, 15 kg / m 3, 17 kg / m3, and at least 19 kg / m3. It is also preferred that the concentration of the biomass in the range of 3 to 20 kg / m3 be adjusted to be at most 18 kg / m3, such as at most 16 kg / m3, 14 kg / m3, 12 kg / m3, 10 kg / m3, 8 kg / m3, and at most 6 kg / m3. Hence, by using the methods of the invention, the metabolic capacity per unit volume is increased, since a higher concentration of microorganisms can be used. In this regard, the control of the quantity and viability of the microorganisms in the system becomes a very important parameter. In this regard, the size of flocs or agglomerates of microorganisms is especially important. Wastewater purification processes, the microorganisms used for biodegradation in aeration tanks tend to form flocs or agglomerates made up of a number of different microorganisms (thus, the flocs are made up of mixed cultures of microorganisms). microorganisms secrete extracellular mucosal substances that form an extracellular matrix, where a number of substances are trapped and are either biodegraded (for example, large biodegradable molecules) or effect biodegradation (enzymes secreted by microorganisms.) Also, they are trapped in this matrix extracellular poisonous and / or inhibitory substances In biological waste water plants, the content of microorganisms (activated sludge) is usually separated from water in a process tank or in a separate clarifier, where sedimentation takes place. the sedimented biomass is then recirculated to the process tank in proportion to the chosen concentration of the active biomass in the process tank. The biomass that is not recirculated to the process tank is sedimented and dehydrated (see Figure 1, which shows a traditional biomass recycling process). During the settling or sedimentation phase, the active bacteria experience difficult life conditions causing the inactivation or death of a large proportion of them. Furthermore, in the sedimentation phase there is practically no biodegradable material or oxygen present, the two fundamental constituents for a reasonable bacterial growth. According to the invention, it is of the highest importance to maintain the ratabolic activity of the microorganisms in the aeration tank at a constant level which ensures effective biodegradation and effective, simultaneous nitrification and denitrification. In addition, it is of great importance to increase the biological activity in the aeration tank by obtaining a greater population of living microorganisms. Therefore, it is desired to avoid subjecting the microorganisms to the tension that is part of a sedimentation process. This can, according to the invention, be achieved by separating the active (viable) biomass from the inactive biomass before the sedimentation process, and only recycling the active part of the biomass. It is known that active microorganisms tend to form flocs or agglomerates of various sizes. However, the present inventors have discovered that the size and / or gravitational density of a floccule is related to its effectiveness as a constituent in a water purification process and, very importantly, this efficiency can be measured by the evaluation BPA of the flocs. Large and / or dense flocs tend to consist of more active microorganisms than smaller flocs. Therefore, a separation process that retains large or dense flocs (with a high BPA) and recycling these while removing the smaller or less dense flocs (with a low BPA) then the excess sludge considerably improves the purification process capacity. However, any system for separating the biofilms can be improved by evaluating BPA of the flocs retained in the separation, and the flocs excluded by it and thus making it possible to optimize such a separation process. According to the invention, it is therefore preferred that such separation (eg, based on the size or density of the flocs) and the recirculation of the activated sludge (biomass) take place before the excess sludge is sent to sedimentation. It has been discovered by the present inventors, that by evaluating the BPA in the aeration tank (before separation) and / or in the sedimentation tank (after separation), it is possible to evaluate the separation of the flocs (for example by their size or density), since a low BPA in the sedimentation phase and a high BPA in the aeration phase is an indication of an effective separation and recirculation of the flocs with high BPA. According to the invention it is therefore especially preferred that the separation be controlled based on such BPA measurements, the optimum separation being one that maximizes the ratio between BPA in the aeration tank and BPA in the settling tank. It is further believed that the processes for the separation of and / or recirculation of sludge that are controlled by evaluation of BPA, are inventive in their own right. The BPA measurement can also be used to control the amount of activated sludge returned, to keep the concentration of activated sludge clearly constant in the aeration tank. With reference to Figures 1 and 2, a separation system forming a part of the present invention is described in the following: The prior art method of biomass recycling (shown in Figure 1) is adjusted at the three points main in order to achieve separation / recycling of the invention: The measuring equipment is installed in the aeration tanks. The measuring equipment is able to indicate the potential activity of microorganisms (BPA) as well as the load situation. The signal is used to periodically check and control the return of the biomass, and with this the concentration of the biomass in the aeration tank. By measuring the BPA in the aeration tank (and optionally in the settling tank) the efficiency of the separation can be controlled, as described above. In addition, a separation unit is introduced between the purification step in the aeration tank and the sedimentation tank; The separation unit can be placed in the aeration tank or in a separate position outside the aeration tank. The separation can be any mechanical, physical or physiological system, such as a filtration system, a centrifugation system, cyclones, a membrane filtration system, a flotation system, etc. A part of the biomass with a high BPA is reverted to the aeration tank, whereby the excess sludge is directed to the sedimentation tank and / or is separated by means of chemical precipitation, membrane filtration, sand filtration or other methods known to the person skilled in the art. In the preferred embodiments, the separation system is adjustable, whereby it becomes possible to separate the flocs of different sizes in the case of changes in the system, thereby altering the size or density of the "optimal flocs".

Finally, a measurement system is introduced to control the biomass separation system to obtain that the fraction of the highest possible BPA is returned to the aeration tank. The measurement system may be based on the BPA measurements as described above, or it may simply be based on the size of the floc after the optimal flock size has been determined, and it is believed that the optimum size / density of the floc , they will not change. By employing such separation of the active biomass from the inactive one before the settling tank, the need for the recirculation of sludge from the settling tank, even to zero recirculation, can be significantly reduced. In addition, the size requirements in the sedimentation step decrease, as less mud is processed in this step. As a result of this, savings in energy and investment are achieved. According to the invention, other specially important controlled parameters are the oxygen concentration, the oxygen dosing rate, and the air dosing rate. As explained above, the method of the invention only proves to be efficient when the concentration of oxygen in the aqueous medium is below 1 mg / liter. In addition, it has been found that oxygen concentrations above 0.1 mg / liter normally ensure that the nitrification process runs satisfactorily. Therefore, according to one aspect of the invention, the oxygen concentration is at least 0.1 mg / liter, preferably at least 0.2 mg / liter. Also according to the invention, the oxygen concentration is preferably at most 0.9, more preferably at more than 0.8, and more preferably at more than 0.7 mg / liter. However, since superior results have been achieved at oxygen concentrations below 0.6 mg / liter, it is especially preferred that the oxygen concentration be adjusted to values below 0.6 mg / liter, such as values below 0.5 or even below 0.4 mg / liter. As will be understood from the foregoing, the essential idea that has made possible the present invention, is the realization that it is possible to control the metabolic activity of microorganisms towards a certain number of values, and therefore achieve that the Biodegradation carried out by microorganisms is effective simultaneously with efficient nitrification / denitrification. Therefore, another part of the present invention is a method for purifying an aqueous medium containing biodegradable material which comprises nitrogen containing components, to substantially reduce the content of biodegradable material in the aqueous medium, the method comprising introducing the aqueous medium in a container wherein the biodegradable material contained in the aqueous medium is subject to biodegradation by microorganisms, and controlling the metabolic activity of said microorganisms in a manner such that biodegradation results in effective nitrification and denitrification, concurrently substantially in all the parts of the container, and that the concentration of oxygen in the aqueous medium is maintained below 1 mg / liter, while effective, simultaneous nitrification and device take place. The term "container" is understood to denote any deposit capable of containing an amount of water that is subject to biodegradation. Typically, the container will be for example an aeration tank in a waste water purification plant.

That "biodegradation results in effective, simultaneous nitrification and denitrification, substantially in all parts of the container" is intended to imply that there is no substantial, intentional subdivision of the container in vertical aerated and less aerated zones. This means that there will only be minor insignificant variations in the average oxygen concentration in the vertical cross sections, randomly chosen from the container, where there is an effective concentration of the flocs. In addition, according to the invention the average oxygen concentration will preferably not exceed 1 mg / liter in such vertical cross sections in any part of the container. By the term "substantially reducing the content of biodegradable material in the aqueous medium" is meant herein that the concentration of biodegradable material is reduced to the most 20% of the initial concentration in the aqueous medium. It is preferred that the concentration of the biodegradable material be reduced to the most 10%, such as at most 5%, 2% or even 1% of the initial concentration. In the most preferred embodiment, the aqueous medium is converted to pure water by the process of the invention.

By the term "pure water" is meant water having a concentration of carbon, nitrogen and / or phosphorus containing components that are at such a low level that virtually no such material is available for biological or microbiological growth in the purified water itself or in the containers for purified water. Any biological or microbiological growth in the containers of pure water is not caused by the admission of pure water into the container. In terms of Biological Oxygen Demand (BOD), Danish legislation has set an upper limit of 15 mg / liter in the final effluent from waste water purification plants, for example for pure water, which can then serve as a practical numerical rule to define the term "pure water" in the present. With respect to the content of suspended solids in the purified water, it is possible to remove substantially all the suspended solids from the waste water by adding one or more additional separation process steps, for example filter or sand filters, to the purification process total. It will be understood that the preferred way to control the metabolic activity of the microorganisms is to employ the methods of the invention for the control of biodegradation, and the invention therefore also refers to a method for purifying an aqueous medium containing biodegradable material on the which comprises nitrogen-containing components, to substantially reduce the content of biodegradable material in the aqueous medium, the method comprises: the introduction of the aqueous medium into a container, wherein the biodegradable material contained in the aqueous medium is subject to biodegradation by the of the microorganisms, and controlling biodegradation according to the methods of the invention for the control of biodegradation. In fact, all preferred embodiments discussed above in relation to the method for controlling biodegradation apply, mutants mutants, to the method of the invention for purifying an aqueous medium. This means that all the modalities described above related to the concentration of the biomass, to the measured parameters, to the controlled parameters, to the means for measuring the parameters, etc., also refer to the method of the invention for purifying aqueous media.

When the methods of the invention are used, the volume of the process, used for the biodegradation of the biodegradable material, can be significantly reduced when compared to the known standard procedures for the purification of biological waste water. As shown in Example 2, a large-scale purification process was performed on a process volume that was only 25% of the process volume normally employed in that purification plant, while maintaining the efficiency of the purification process . It is believed that further reductions can be obtained when the method of the invention is used, as the reduction of 25% in Example 2 was the maximum that could be achieved, simply because no further reductions in volume could be achieved. process in that particular purification plant (since there were no additional aeration tanks to close). The German standards ATV-A 122, 126 and 131 describe well-defined and widely accepted standards for the construction and running of activated sludge processes. In comparison to these standards, methods for purifying an aqueous medium according to the invention have proven to be highly superior in a number of aspects. Therefore, another important aspect of the method of the invention for purifying waste water is one that has an activated sludge process volume of at most 80% that of the purification performed as described in any of the German standards. ATV-A 122, ATV-A 126, or ATV-A 131, the standard method that purifies a similar amount of waste water. In the preferred embodiments the process volume is at most 70%, such as at most 60%, 50%, or 40% of the standard purification process. It is especially preferred that the process volume be at most 30%, more preferably at most 25%, and more preferably 20%. It is expected that the minimum possible volume of the process is at most 10% of that of one of the standard processes, and this is the most preferred embodiment of this aspect of the invention. A further advantage of the methods of the invention is that the energy demand of the purification process is decreased. The smaller volume of the process results in smaller volumes having to be aerated in order to keep the purification process running. It is well known in the art that the aeration of waste water for example in aeration tanks is one of the processes that demand more energy in the purification of waste water. In parallel with the foregoing, the invention also relates to a method of the invention for the purification of waste water, wherein the energy required to purify the aqueous medium is at most 90% of the energy required for a purification performed as it is described in any of the standards ATV-A 122, ATV-A 126, or ATV-A 131, the standard method that purifies a similar amount of waste water. In the preferred embodiments the energy requirement is at most 70%, such as at most 60%, 50%, or 40% of the standard purification process. It is especially preferred that the energy required be at most 30%, more preferably at most 25%, and still more preferably 20%. It is expected that the minimum possible energy required is at least 10% of that of the standard processes, and this is the most preferred embodiment of this aspect of the invention. A number of additional advantages than those described above are achieved by the use of the methods of the invention. First of all, the microorganisms become relatively insensitive to poisonous or inhibitory substances in the incoming water, probably because such substances are immobilized in the extracellular mucosal substances that constitute the "backbone" of the flocs; this process seems to be optimal, when the flocs are separated and recycled as described above, for example, the flocs seem to work optimally in this respect when their size is optimal with respect to biodegradation and nitrification / denitrification. A paradox is that one of the aforementioned "poisonous or inhibitory substances" is atmospheric oxygen (and of course hyperreactive oxygen radicals such as "O and H202). In this way, oxygen tends to assist in the unwanted breaking of the mucosal spine of the flocs, thereby increasing the damage of large-scale sludge formation when the flocs are made physically unstable and diminish in size. In the methods of the prior art it is imperative to apply high oxygen tensions in order to effect nitrification, and therefore the negative effects of oxygen could not be avoided, a disadvantage not suffered in the present invention. Thus, apart from the fact that the method of the invention ensures optimum biodegradation in combination with simultaneous nitrogen removal, the flocs of microorganisms are protected against degradation and thus the formation of sludge is inhibited. This may be one of the reasons why the biomass is not "washed abundantly" although the smaller volume of the process results in higher hydraulic loads. In other words, the biomass shows superior retention in the aeration tank when the tank is operated according to the methods of the invention. Hence, there is also a smaller risk of container contamination that results from the loss of biomass from clarifiers, even in situations where the purification process is subject to large hydraulic loads (after and during rain). abundant, etc.). Also, the costs for the construction of the new waste water purification plants will be decreased, since smaller plants are needed when the methods of the invention are used. Another advantage is that the existing plants will become more flexible, since these may be subject to higher loads, and since the tanks that are normally of dimensions suitable only for nitrification, become capable of performing denitrification as well. All these advantages are added to the conclusion that the costs for the production of one cubic meter of purified water can be significantly reduced, which makes the purification of waste water effective, accessible and economically realistic, for example for third World countries. The methods discussed above of the invention can of course be combined with all conventional methods for the optimization of biodegradation or the purification of waste water as such. The skilled persons will know how to combine the improvements of the present method with the existing methods for the purification of waste water, but a review of the possibilities can be found in the European patent EP-B-461166 (U.S. Patent No. 5,506,096). It will be understood that the results obtained by using the methods of the invention are highly dependent on the precise determination of the range of values or the simple value of at least one parameter of metabolic activity, which indicates that the microorganisms will perform a nitrification and denitrification effective, simultaneous, biodegradable material. Thus, the invention also relates to a method for determining a range of values or a single value of a metabolic activity parameter, which represents the metabolic activity of the microorganisms that biodegrade the biodegradable material in an aqueous medium, the material comprising biodegradable components that contain nitrogen, being the values in the range or the unique value those that indicate that the microorganisms will realize the effective, simultaneous nitrification and denitrification of the biodegradable material contained in the aqueous medium, the method includes: - the evaluation of the values of the parameter of metabolic activity and at the same time the evaluation of the effectiveness of the biodegradation and the efficiency of the elimination of nitrogen (as discussed above in relation to the predetermination of the values), and the selection, as the values in the interval or as the unique value, of the values that are associated with simultaneous effective biodegradation and the elimination of nitrogen at oxygen concentrations below 1 mg / liter.

The term "effective, simultaneous biodegradation and elimination of nitrogen" means a simultaneous reduction of BOD and total nitrogen to values below 15 mg / liter and 8 mg / liter, respectively. Finally, a fourth part of the invention is a water purification plant, wherein at least one purification process comprising a biodegradation step is carried out according to the methods of the invention for purifying aqueous media, or wherein the biodegradation it is controlled according to the method of the invention, to control biodegradation.

EXAMPLES EXAMPLE 1 Small-scale operation performed according to the invention.

The method of the invention was investigated by changing the operation of the purification plant in Nr. Herlev, Denmark, from a standard operation to the method of the invention for purification of waste water. The plant is designed as a simple line with an aeration tank and a clarifier. The standard process originally used in the tank was a nitrification process, where the aeration tank was aerated from the surface, and the aeration was regulated with a rotor. The oxygen levels were constantly between 2 and 4 mg / ml and the concentration of the biomass was 3-4 kg / m3. The plant is of adequate dimensions for 700 personal equivalents (PE). The aeration tank has a volume of 220 m3 and the clarifier has a volume of 85 m3. BioBalance sensors (available from BioBalance A / S,, Vallensboek, Denmark and described in detail in European patent EP-A-641, 431) were installed in the plant. The BioBalance sensors measured the fluorescence emission from NADH and microbial NADPH at 460 nm after light excitation at 340 nm. As described in European Patent EP-B-461166 and U.S. Patent No. 5,506,096, it is possible to periodically check the metabolic activity of microorganisms present in an aqueous system, such as an aeration tank by measuring the fluorescence emission from, for example, NADH in microorganisms, and the results from such measurements can then be used as measured variables in an on-line automation system, where the process variables are controlled in a direction that ensures optimal biodegradation on the part of the microorganisms. For a period of 3 weeks the operation was verified daily (performed by the standard method), for example the parameters of the process, oxygen, COD, BOD, flow, temperature, pH, mud concentrations (concentration of suspended solids), ammonium, nitrate, nitrogen and phosphate, and energy consumption were used recording standard known methods in the technique at different points in the purification process, as was the fluorescence of NADH. It was then decided to operate the plant by continuously adjusting the oxygen concentration towards values that directed the subsequent fluorescence measurements towards the average fluorescence value (250 BPA) which had been recorded during the 3 weeks, and thus the process was modified to the method of the invention to control biodegradation. After the modification, the aeration tank performed simultaneous nitrification and denitrification at an oxygen level that was never outside the range between 0.1 and 0.3 mg / liter. The oxygen level was automatically controlled as a response to oscillations in the fluroescence coming from the NADH in the tank. The concentration of the activated sludge was maintained at a level of 3-4 kg / m3 after the modification. During the experimental period, the concentrations of the compounds of interest at the entrance and exit of the plant were checked periodically by daily sampling and subsequent laboratory analysis (performed by standard methods known in the art). The results of this periodic verification were the following: Input values: Volume: 250 mVday COD: 200 mg / liter Nitrogen: 30 mg / liter Nitrogen output values before the process change: Total N: «20 mg / liter N03: * 20 mg / liter Nitrogen output values after the process change: Total N: «6 to« 8 mg / liter NH.,: «1 mg / liter N0:« 5 to «7 mg / liter The output was also checked periodically by NADH fluorescence measurements, which were made online during the operation. The measurements at the output (the laboratory values and the fluorescence values) were not influenced by the values at the input, a fact that is proof of the flexibility of the method of the invention.

Discussion: By the use of the methods of the invention in this small-scale waste water purification, a process that had been solely for the nitrification of the waste water was now able to perform simultaneous nitrification and denitrification. This fact is evidenced by the reduced nitrogen output (a reduction to 30% -40% of the original nitrogen concentration) after the start of the method of the invention.

EXAMPLE 2 Large scale operation performed according to the invention.

The method of the invention was investigated by changing the operation of the municipal purification plant in Hecklingen, Germany, from a standard operation (as described in ATV-A 131) to the method of the invention for water purification of waste. The plant is designed as two lines in parallel, each with a selector to the front, two aeration tanks and a clarifier. The process originally used in the tank was a biodenifo process (an alternate nitrification and denitrification process described for example in German Patent No. 34,273,107) where nitrogen was removed in the nitriding phase at oxygen levels of 1.5 to 2. mg / liter, followed by a denitrification phase at an oxygen level of approximately 0 mg / liter. The adjustment of the dimensions of the plant was based on ATV-A 131, and was designed for 48,000 personal equivalents (PE); each line was designed for 24,000 PE, and each aeration tank was thus of suitable dimensions for 12,000 PE. BioBalance sensors (available from BioBalance A / S, Vallensboekvej 45, 2605 BrOndby, Denmark) were installed in the plant. The BioBalance sensors measured the emission of fluorescence from NADH and NADPH at 460 nm after excitation with light at 340 nm. As described in European patent EP-B-461166, it is possible to periodically check the metabolic activity of the microorganisms present in an aqueous system such as an aeration tank by measuring the fluorescence emission for example from NADH in the microorganisms, and the results from such measurements can be used as variables measured in an on-line automation system, where the process variables are controlled in a direction that ensures optimal biodegradation by microorganisms. For a period of three months, the daily operation (performed by the standard method) was checked periodically, for example, the parameters of the process, that is, oxygen, COD, BOD, flow, temperature, pH, mud concentrations (concentration of the suspended solids), ammonia, nitrate, nitrogen and phosphate, and energy consumption, were recorded using the standard methods known in the art, at different points in the purification process, as was the fluorescence of NADH. It was then decided to operate the plant by interrupting or shutting down three of the four aeration tanks, which reduces the volume of aeration from the original four tanks of 15,600 m3 in total to a tank of 3,900 m3. The single tank was operated by continuously adjusting the oxygen concentration to values that directed the subsequent fluorescence measurements to the average fluorescence value (BPA) which had been recorded during the three months, and in this way the process was modified to the method of the invention to control biodegradation. After the modification, the aeration tanks were thus using a single phase (with simultaneous nitrification and denitrification) at an oxygen level that was never outside the range of 0.2 to 0.6 mg / liter. The oxygen level was automatically controlled as a response to oscillations in the fluorescence from NADH in the tank. The effective load of the plant was approximately 30,000 PE, which means that the capacity of the aeration tank that was operated according to the invention was 2.5 times greater than the calculated capacity. The concentration of the activated sludge was maintained at a level of 15 kg / m3, a value three times higher than the standard value according to ATV-A 131. During the experimental period, the concentrations of the compounds of interest at the entrance and at the the output from the plant were checked periodically by daily sampling and subsequent laboratory analysis (performed by standard methods known in the art). The results of this periodic verification were the following: Input values: COD: 300 to 1100 mg / liter Nitrogen: 25 to 65 mg / liter Phosphorus: 3 to 8 mg / liter Output values: C OD..a? 25 mg / liter C0D? R = a 15 mg / liter NH3: 0. 05 to 2 mg / liter N03: 0. 05 to 3 mg / liter P: less than 1 mg / liter The output was periodically verified in addition by fluorescence measurements of NADH, which were carried out online during the two months of operation. The output measurements (laboratory values and fluorescence values) were not influenced by the values of the input, a fact that is proof of the flexibility of the method of the invention.

Discussion: By using the method of the invention in this large-scale wastewater purification, the volume of the process was reduced to 25% of the process volume, normally used in the plant, while the efficiency of the purification was maintained at the level normally observed during the large-scale standard operation. Furthermore, even though the operation was performed in this smaller process volume, the output values of the compounds of interest were not sensitive to daily changes in the load. The choice of the average fluorescence value of NADH from the previous records is not necessarily the optimal value. In order to determine the optimal operational value of the fluorescence, the system can be fine-tuned by periodic verification of biodegradation as discussed above when using other fluorescence reference points.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims

1. A method for controlling the biodegradation of biodegradable material comprising nitrogen-containing components, the biodegradable material is contained in an aqueous medium, and biodegradation is effected by microorganisms, the method is characterized in that it comprises: the evaluation of the value (evaluated value) of at least one parameter of metabolic activity (measured parameter) which represents the metabolic activity of the microorganisms which biodegrade the biodegradable material in the aqueous medium, - the comparison of the assessed value with a predetermined range of values or a predetermined single value of at least one measured parameter, the values in the range or the single value are those that indicate that the microorganisms will perform effective, simultaneous nitrification and denitrification of the biodegradable material contained in the aqueous medium, and thereafter if the evaluated value falls outside the range or is different from the single value, or if the oxygen concentration exceeds 1 mg / liter, at least one parameter (controlled parameter) is adjusted which has an influence on the metabolic activity of the microorganisms in a direction that 1) tends to move the subsequent evaluated values towards the interval or towards the single value and 2) ensures that the concentration of oxygen in the aqueous medium is maintained below 1 mg / liter, while effective, simultaneous nitrification and denitrification takes place.

2. A method according to claim 1, characterized in that at least one controlled parameter is adjusted in a direction that tends to move the subsequent evaluated values towards a specific value in the range.

3. A method according to claim 1 or 2, characterized in that the values in the range or in the single value have been predetermined by empirical calibration.

4. A method according to any of the preceding claims, characterized in that the measured parameter is selected from the group consisting of the concentration of oxygen, the concentration of the biomass, the ratio of oxygen concentration / COD, concentration of C02, emission of fluorescence from characteristic biogenic fluorophores, biodegradable material loading, oxygen concentration, pH, temperature, turbidity, rate of dosing of precipitation chemicals, rate of dosing of additional easily biodegradable material containing carbon , the rate of dosage of the substances capable of converting the material not easily biodegradable to easily biodegradable material, the speed of recycle of the activated sludge, the speed of the inflow, the speed of the flow of exit, the speed of agitation, the speed of the oxygen dosage, l at air dosing speed (aeration), the total amount of activated sludge in the system, and the concentration of the activated sludge in aqueous medium.

5. A method according to any one of the preceding claims, characterized in that the evaluation of the measured parameter comprises the measurements selected from the group consisting of the fluorescence emission measurements of at least one characteristic biogenic fluorophore, the gas chromatography measurements, the measurements infrared, turbidity measurements, nuclear magnetic resonance measurements, chemical measurements of ammonia, phosphates and nitrates, redox potential measurements, short-term BOD measurements, and chromatographic measurements such as HPLC and FPLC, and combinations thereof.

6. A method according to claim 4 or 5, characterized in that the biogenic fl.oorophore is selected from the group consisting of proteins containing tryptophan and tyrosine, peptides containing tryptophan and tyrosine, amino acid derivatives containing tryptophan and tyrosine, purines, pyrimidines, nucleosides, nucleotides, nucleic acids, steroids and vitamins.

7. A method according to any of the preceding claims, characterized in that the evaluation of the measured parameter is carried out by online measurement of the measured parameter.

8. A method according to claim 6 or 7, characterized in that the measurement is carried out using the in-line fluorescence sensor equipment.

9. A method according to any of claims 4 to 8, characterized in that the biogenic fluorophores are excited with excitation light of a wavelength preferably greater than 250 nm, and the fluorescence emission is preferably detected at a wavelength of 280-500 nm.

10. A method according to claim 9, characterized in that the excitation light is emitted at a wavelength that is inside the envelope of the excitation band for the fluorophore, and the fluorescence emission is detected at a wavelength that is within the envelope of the fluorescence band for said fluorophore, preferably at a wavelength corresponding to a peak or maximum in the fluorescence spectrum of the fluorophore.

11. A method according to any of claims 4 to 10, characterized in that the fluorophore is a nicotinamide adenine dinucleotide such as NADH or NADPH.

12. A method according to claim 11, characterized in that the excitation light is emitted at a wavelength of approximately 340 nm, and the fluorescence emission is detected at a wavelength of approximately 460 nm.

13. A method according to any of the preceding claims, characterized in that the controlled parameter is selected from the group consisting of the charge of the biodegradable material, the concentration of oxygen, the pH, the temperature, the turbidity, the dosage rate of the products precipitation chemicals, the rate of dosing of the additional material containing carbon, easily biodegradable, the rate of dosing of substances capable of converting the material not easily biodegradable to easily biodegradable material, the speed of recycled activated sludge, the speed of the Inlet flow, outflow speed, agitation speed, oxygen dosing rate, air dosing rate (aeration), the total amount of activated sludge in the system, the concentration of the activated sludge in the aqueous medium, and other process parameters that are conventional in the processes of water treatment, waste water or similar.

14. A method according to claim 13, characterized in that the concentration of the biomass is adjusted to be at least 3 and at most 20 kg / m 3.

15. A method according to claim 14, characterized in that the concentration of the biomass is adjusted to be at least 11 kg / m3.

16. A method according to any of claims 13 to 14, characterized in that at least one parameter that influences the metabolic activity of the microorganisms is the oxygen concentration, the oxygen dosing rate, or the air dosage rate .

17. A method according to claim 16, characterized in that the oxygen concentration is adjusted to be more than 0.9 mg / liter.

18. A method according to claim 16 or 17, characterized in that the oxygen concentration is adjusted to be at least 0.1 mg / liter.

19. A method according to any of the preceding claims, characterized in that the adjustment of at least one parameter that influences the metabolic activity of the microorganism is carried out by an on-line automation system.

20. A method for purifying an aqueous medium containing biodegradable material which comprises nitrogen containing components, to substantially reduce the content of biodegradable material in the aqueous medium, characterized in that the method comprises the introduction of the aqueous medium into a container, wherein the biodegradable material contained in the aqueous medium is subject to biodegradation by microorganisms, and the metabolic activity of said microorganisms is controlled in a manner such that biodegradation as a result effective nitrification and denitrification, simultaneously, substantially in all parts of the vessel by maintaining the concentration of oxygen in the aqueous medium below 1 mg / liter, while having effective nitrification and denitrification at the same time.

21. A method according to claim 20, characterized in that the control of biodegradation is carried out according to the method according to any of claims 1 to 19.

22. A method for purifying an aqueous medium containing biodegradable material which comprises nitrogen-containing components, to substantially reduce the content of biodegradable material in the aqueous medium, characterized in that the method comprises: introducing the aqueous medium into a container wherein the material Biodegradable content in the aqueous medium is subject to biodegradation by microorganisms, and control of biodegradation according to the method according to any of claims 1 to 19.

23. A method according to any of claims 20 to 22, characterized in that the microorganisms are a mixed culture of microorganisms such as activated sludge.

24. A method according to claim 23, characterized in that it has an activated sludge process volume of at most 80% of that of a standard purification process performed as described in any of the standards ATV-A 122, ATV-A 126, or ATV-A 131, the standard method that purifies a similar amount of water.

25. A method according to claim 24, characterized in that the volume of the activated sludge process is at most 70%, such as at most 60%, 50%, or 40%, and preferably at most 30%, more preferably at most 25%, still more preferably 20%, and still more preferably at most 10% of that of the standard process.

26. A method according to any of claims 23 to 25, characterized in that the energy supplied for the purpose of purifying the aqueous medium is at most 90% of the energy required for a purification performed as described in any of the ATV standards. -A 122, ATV-A 126, or ATV-A 131, the standard method that purifies a similar amount of water.

27. A method according to claim 26, characterized in that the energy delivered is at most 70%, such as at most 60%, 50%, or 40%, and preferably at most 30%, most preferably at most 25%, even more preferably 20%, and still more preferably at most 10% of that of the standard process.

28. A method for the determination of a range of values or a unique value of a metabolic activity parameter which represents the metabolic activity of the microorganisms that biodegrade the biodegradable material in an aqueous medium, the biodegradable material comprises the nitrogen-containing components, being the values in the range or of the single value those that indicate that the microorganisms will realize the effective, simultaneous nitrification and denitrification of the biodegradable material contained in the aqueous medium, characterized the method because it comprises: - the evaluation of the values of the parameter of metabolic activity and at the same time evaluating the effectiveness of biodegradation and the effectiveness of nitrogen removal, and the selection, as the values in the range or as the single value, of the values that are associated with simultaneous effective biodegradation and the elimination of nitrogen at concentrations of oxygen below 1 mg / liter.