WO1999024370A1 - Procede de controle de la biodegradation - Google Patents

Procede de controle de la biodegradation Download PDF

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Publication number
WO1999024370A1
WO1999024370A1 PCT/DK1998/000486 DK9800486W WO9924370A1 WO 1999024370 A1 WO1999024370 A1 WO 1999024370A1 DK 9800486 W DK9800486 W DK 9800486W WO 9924370 A1 WO9924370 A1 WO 9924370A1
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Prior art keywords
biodegradation
nitrification
phase
aqueous medium
measured parameter
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PCT/DK1998/000486
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English (en)
Inventor
Peter NØRGAARD
Mette Risum Mikkelsen
Nicolas Heinen
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Biobalance A/S
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Priority to AU11443/99A priority Critical patent/AU1144399A/en
Publication of WO1999024370A1 publication Critical patent/WO1999024370A1/fr

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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
    • C02F3/006—Regulation methods for biological treatment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/02—Temperature
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/06—Controlling or monitoring parameters in water treatment pH
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/14—NH3-N
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/22—O2
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/36—Biological material, e.g. enzymes or ATP
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/44—Time

Definitions

  • the present invention relates to a method for controlling biodegradation of an aqueous medium containing nitrogen-containing biodegradable material, e.g. waste water, and to a method for determining the concentration of ammonia in an aqueous medium.
  • biodegradable material from e.g. municipal and industrial waste water is often performed by including some sort of biological treatment step in the water purification process. Normally, complex cultures of microorganisms are used to effect the biodegradation, resulting in a conversion of the biodegradable material into environmentally acceptable compounds such as CO 2 and N 2 .
  • the goal is to convert the nitrogen bound in nitrogen-containing components of waste water into gaseous (atmospheric) nitrogen, and this is traditionally done by the steps of nitrification (an oxidation step) and denitrification (a reduction step).
  • nitrification an oxidation step
  • denitrification a reduction step
  • complex nitrogen-containing substances are deaminated by i.a. deaminases produced by the microorganisms (or optionally supplied to the system in question) and the remaining main problem is thus to convert ammonia into gaseous nitrogen.
  • nitrification and denitrification reactions are facilitated by the microorganisms which are responsible for the biodegradation, but as nitrification is facilitated by high oxygen concentrations and denitrification is facilitated by low oxygen concentrations, one of two principles has generally been used:
  • biodegradation process is subjected to intermittent aeration, whereby the two processes are substantially non-simultaneous.
  • intermittent aeration One example of such a process is described in US 5,304,308.
  • WO 96/35644 discloses a process that allows simultaneous nitrification and denitrification in an aqueous medium containing a biodegradable material such as waste water comprising nitrogen-containing components. This is achieved by controlling the living conditions of the microorganisms in such a manner that their metabolic activity is kept within a narrow range allowing simultaneous nitrification and denitrification to take place. In particular, the oxygen concentration is kept within a narrow range below 1 mg/l (below 1 ppm).
  • the problem remains, however, how to "fine-tune" systems of this type, as well as other biodegradation systems, in order to be able to achieve the optimum result in any given system.
  • WO 96/03254 describes an apparatus and a method for real time monitoring of the biological activity of waste water and for controlling the treatment thereof by means of detection of NADH fluorescence of a waste water sample isolated from the bioreactor tank. It is explained in this document that the apparatus can be used in the oxic stage to serve as a NH 3 meter. However, this involves, in addition to a first sample chamber containing the sample being analysed, a separate second sample chamber to which a known amount of NH 3 is added, and a subsequent calculation of the amount of NH 3 in the sample being analysed based on the known amount of NH 3 added to the second sample chamber as well as certain other assumptions. This is thus an indirect and rather complicated approach to the problem of determining the NH 3 concentration and using the results of the determination to control the biodegradation process.
  • measured parameters such as the concentration of NADH in the medium can be used to determine both the end of nitrification and the end of denitrification in a biodegradation process, thereby allowing more precise control of the biodegradation process.
  • the determined values for e.g. NADH concentration can be used to automatically control the oxygen level in the water being treated, thereby improving the efficiency of the waste water treatment process.
  • An object of the present invention is therefore to provide a method for optimising the biological treatment of a nitrogen-containing aqueous medium, e.g. waste water, based on determinations of e.g. the NADH concentration in the medium.
  • Another object of the invention is to provide a simpler method for determining the ammonia concentration of an ammonia-containing aqueous medium.
  • One aspect of the invention thus relates to a method for controlling biodegradation of an aqueous medium containing biodegradable material comprising nitrogen-containing components, the method comprising
  • Another aspect of the invention relates to a method for determining the concentration of ammonia in an aqueous medium subject to biodegradation of nitrogen-containing components in the medium, the method comprising monitoring fluorescence emission values from at least one characteristic biogenic fluorophore in the medium over a period of time, and
  • a measured parameter that "represents" the ammonia concentration of an aqueous medium is a parameter whose value is related to the ammonia concentration of the medium, i.e. the measured parameter varies with varying ammonia concentrations.
  • the measured parameter varies with varying ammonia concentrations.
  • predetermined criteria refers to a predefined set of criteria with which the assessed value, or, more typically, a series of assessed values, is to be compared in the method of the invention or in an individual phase of the method.
  • the predetermined criteria can comprise a predetermined single value or a predetermined range of values for the measured parameter, and/or the predetermined criteria can comprise a set of one or more conditions that, when fulfilled, trigger a response in terms of adjustment of the oxygen concentration of the aqueous medium using predefined set-points.
  • the predetermined criteria may, for example, comprise sets of conditions for measurements of fluorescence emission that, when fulfilled, indicate that a nitrification or denitrification phase has been completed, thereby allowing the oxygen concentration of the medium to be adjusted accordingly so that the desired next phase of the biodegradation process can begin.
  • controlling denotes the act of regulating or deliberately influencing one or more variables of a process on the basis of measurements of one or more of the variables of the process.
  • the latter variable is denoted the measured variable
  • the first-mentioned variable is conventionally denoted the controlled variable.
  • the desired numerical value of the controlled variable is referred to as the set-point.
  • biodegradable material refers to organic and/or inorganic matter which is biologically decomposable, such decomposition taking place by subjecting the organic and/or inorganic matter, especially organic matter, to a transformation process effected by cultures of microorganisms, the transformation process taking place in an aqueous environment, for example waste water, sewage, lake water, sea water, river water and the like.
  • the microorganisms use the biodegradable material as a source of nutrition and/or energy, thus converting the biodegradable material into additional biomass and to end products of metabolism such as nitrates, gaseous nitrogen, sulphates, phosphates, carbon dioxide, etc.
  • nitrogen containing substances and “nitrogen containing components” as used herein refer to ammonia, nitrates, nitrites, proteins, amino acids, purines, pyrimidines, nucleic acids, nucleosides, nucleotides and other organic/inorganic compounds that contain nitrogen.
  • biodegradation refers to the process in which microorganisms metabolize biodegradable material present in an aqueous medium.
  • the aqueous medium is introduced into a tank, a basin or the like normally containing mixed cultures of microorganisms, i.e. activated sludge (biomass), wherein the biodegradable material in the aqueous medium to be treated is degraded by the microorganisms present.
  • the expression "optimise” in the context of optimising biodegradation herein refers to controlling the biodegradation process in such a way that the overall process results in a satisfactory or desired biodegradation of organic matter, in particular nitrogen-containing components, the general aim being to obtain biodegradation that is as effective and efficient as possible under the given circumstances.
  • aqueous medium contains water as the basic predominant constituent, e.g. typically at least about 80% by weight, more typically at least about 90% by weight, of water.
  • the aqueous medium will typically 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, sea water, polluted sea water, or other aqueous systems containing biodegradable material as defined herein.
  • waste water refers to aqueous effluents containing organic and/or inorganic substances which are present or formed in an environment as a consequence of the presence and/or activity of human beings.
  • microorganisms refers to organisms such as autotrophic as well as heterotrophic and aerobic, anaerobic or facultative bacteria, as well as lower eucaryotic organisms such as protozoa, yeasts, fungi, and other organisms usually present in activated sludge in the biological treatment step of a waste water purification plant, for example multicellular organisms such as slipper animalcule (Paramaecium) and parasites, especially bacteria-consuming parasites.
  • multicellular organisms such as slipper animalcule (Paramaecium) and parasites, especially bacteria-consuming parasites.
  • the microbial system used in the biological treatment steps is normally a mixed culture of microorganisms, i.e. comprising a variety of different species.
  • the terms "activated sludge” or “biomass” are conventionally used terms for mixed cultures of microorganisms which are present in the biological treatment step in order to degrade the biodegradable material, i.e. especially decomposable organic and/or inorganic matter.
  • the actual composition of the mixed cultures of microorganisms may vary widely since the composition is highly dependent on the prevailing conditions.
  • the method according to the invention for controlling biodegradation is suitable for use in any biodegradation process that includes biodegradation of nitrogen-containing components in an aqueous medium, including processes in which nitrification and denitrification are performed separately, e.g. with intermittent aeration or compartmentalised nitrification/denitrification, and processes in which nitrification and denitrification are performed simultaneously. Regardless of how the nitrification and denitrification is performed, the present invention will be advantageous for controlling and optimising the process.
  • the biodegradation process may, if desired, alternate between different phases, for example by performing, in sequence, 1) a simultaneous nitrification and denitrification phase using aeration to obtain an oxygen concentration in the range of at the most about 1.0 mg/l, e.g. about 0.1-1.0 mg/l, typically about 0.2-0.8 mg/l, 2) a nitrification phase using aeration to obtain an oxygen concentration in the range of about 0.2-3 mg/l, typically above about 1.0 mg/l, and 3) a denitrification phase without aeration.
  • the relative length of the various phases can be adjusted as needed, and/or individual phases can be eliminated in one or more cycles of the process.
  • This approach can also be used for determining the oxygen set-point for the simultaneous nitrification/denitrification, regardless of whether the simultaneous nitrification/denitrification is ultimately to be used alone or whether it is to be used in a sequence comprising additional, separate nitrification and denitrification phases.
  • the oxygen set-point will be determined as a function of the denitrification time, the nitrification time, the temperature of the medium and general level of fluorescence.
  • the denitrification and nitrification times may be determined by means of NADH fluorescence measurements as described herein, the denitrification time increasing with increasing nitrate concentrations, and the nitrification time increasing with increasing ammonia concentrations.
  • the depletion of nitrate is seen as a rise in fluorescence, which in a preferred embodiment triggers a computer- controlled oxygen set-point to switch to the high oxygen concentration level.
  • Oxygen is thus automatically introduced into the waste water, resulting in oxidation of ammonia to nitrate.
  • the nitrification proceeds at an enhanced rate until ammonia is depleted.
  • the fluorescence attains its minimum value, which triggers a reduction of the computer-controlled oxygen set-point, whereby the oxygen concentration attains its lower level by virtue of the oxygen supply being cut off or at least reduced.
  • At least one phase of the biodegradation takes place as a simultaneous effective nitrification and denitrification, e.g. as disclosed in WO 96/35644, the contents of which is incorporated by reference.
  • simultaneous effective nitrification and denitrification is intended to denote that the aqueous medium is subjected to a biodegradation by the microorganisms which results in the simultaneous production of 1) nitrates from nitrogen-containing substances, in particular ammonia, and 2) gaseous nitrogen from the nitrates.
  • the term "effective" in this context denotes that the final result is an aqueous medium with a total nitrogen concentration after biodegradation of at the most about 20 mg/l, preferably at the most about 15 mg/l, more preferably at the most about 10 mg/l, such as at the most 8 mg/l or at the most 5 mg/l. It will furthermore often be desired that the content nitrogen present as ammonia will be as low as possible, and the final NH 3 -N content in the aqueous medium is therefore preferably no more than about 10 mg/l, more preferably no more than about 5 mg/l, such as no more than about 3 mg/l or no more than about 1 mg/l.
  • the microorganisms are all subjected to substantially the same conditions (i.e. the metabolic level is sought kept at substantially the same level in all parts of the aqueous medium), meaning that there is no intentional physical division of the aqueous medium into e.g. zones of high and low oxygen concentration, respectively.
  • the two reactions of nitrification and denitrification take place not only at the same time, but they also take place in parallel in the same tank, with no division into zones favouring either of the two processes of nitrification or denitrification.
  • the employed low general oxygen level i.e.
  • the oxygen concentration is made to oscillate within a range whose upper and a lower level allow both nitrification and denitrification to proceed simultaneously, although with varying rates for the nitrification and denitrification, respectively.
  • the oxygen concentration thus oscillates around a steady state concentration at which nitrification and denitrification would proceed at an equal rate.
  • accumulated nitrate is denitrified at an enhanced rate until it is depleted.
  • accumulated ammonia is nitrified at an enhanced rate until it is depleted.
  • the method of the invention for controlling biodegradation is aimed at providing a favourable metabolic activity of the microorganisms, i.e. a catabolic state of the microorganisms which results in a high rate of biodegradation (i.e. only small amounts of energy are "wasted" in the anabolic metabolism of the microorganisms).
  • parameters that may be measured in a biodegradation process are fluorescence emission from biogenic fluorophores, CO 2 concentration, oxygen concentration, biomass concentration, oxygen concentration/COD ratio, biodegradable material loading, oxygen concentration, pH, temperature, turbidity, dosage rate of precipita- tion chemicals, dosage rate of additional readily biodegradable carbon-containing material, dosage rate of substances capable of converting not readily biodegradable material into readily biodegradable material, rate of recycling of activated sludge, inlet flow rate, outlet flow rate, stirring rate, oxygen dosage rate, air dosage (aeration) rate, total amount of activated sludge in the system, and other process parameters which are conventional in treatment processes of water, waste water or the like.
  • Such parameters may be measured by methods known to the person skilled in the art.
  • the present invention is in particular based upon measurements of fluorescence emission from at least one characteristic biogenic fluorophore.
  • the measurements of fluorescence are performed using automatic, online measurements, as this renders possible a continuous surveillance of the processes, allowing action to be taken immediately when the relevant predetermined set of criteria is fulfilled, e.g. by means of computer controlled set-point adjustments.
  • on-line automatization system is intended to denote a system comprising online measurement equipment which is connected to effector equipment capable of controlling a process parameter.
  • the effector equipment is fed with the information from the online measurements and controls the process parameter in an automated manner which is dependent on the incoming signal.
  • Examples of such systems are negative feed-back systems, wherein a registration of values of a measured parameter indicating a change in a controlled parameter leads to the automatic regulation of the controlled parameter in a direction opposite that of the observed change.
  • control of controlled parameters is effected by an on-line automatization system, although manual or semi- manual surveillance of measured parameters and subsequent manual or semi-manual adjustment of controlled parameters can of course be performed alternatively or additionally, if desired. It is especially preferred to use on-line fluorescence sensor equipment to measure fluorescence emission.
  • biogenic fluorophore denotes a substance synthesized by living material (living cells), the molecules of such a substance being capable of fluorescing when irradiated with light.
  • Biogenic (biological) fluorophores include proteins, especially tryptophan- and tyrosine-containing proteins, tryptophan- and tyrosine-containing peptides, tryptophan- and tyrosine-containing derivatives of amino acids, co-factors, purines, pyrimidines, nucleosides, nucleotides, nucleic acids, steroids, vitamins and others.
  • NADH nicotinamide adenine dinucleotide
  • 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, estrogens, histamine, vitamin A, phenylalanine, p-aminobenzoic acid, dopamine (3,4-dihydroxyphenylethylamine), serotonin (5-hydroxytryptamine), dopa (3,4- dihydroxyphenylalanine), kynurenine and vitamin B12.
  • fluorescence and fluorescence emission refer to the emission of radiant energy by a molecule or ion in the excited state caused by absorption of radiant energy.
  • Each biochemical or chemical molecule has a characteristic excitation and fluorescence spectrum.
  • the fluorescence spectrum or fluorescence band is split into two or more peaks or maxima, each peak occurring at a specific wavelength.
  • this emission is detected at a wavelength which is within the envelope of the fluorescence band for the fluorophore, preferably at a wavelength corresponding to a peak in the fluorescence spectrum.
  • the fluorophore should be irradiated with light emitted at a wavelength which is within the envelope of the excitation band for the fluorophore, preferably at a wavelength corresponding to a peak in the excitation band.
  • biogenic fluorophore is one which is inherently produced by the living biological material in question, i.e. the mixed culture of microorganisms, in an amount reflecting the biological activity, for example the metabolic activity, of the living material.
  • biogenic fluorophores are present as intracellular substances in the microorganisms.
  • the light is emitted at a wavelength longer than 250 nm, especially 250-780 nm, for example about 340-360 nm, and that fluorescence emission is detected at wavelengths longer than 250 nm, preferably 250-800 nm, especially 280-500 nm, for example about 460 nm.
  • the wavelength should of course be adapted to the particular system, in particular the kind of fluorophores present in the system.
  • important embodiments of the method are embodiments wherein the fluorophore is a nicotinamide adenine dinucleotide such as NADH or NADPH.
  • the excitation light is preferably emitted at a wavelength of about 340 nm, and the fluorescence emission is detected at a wavelength of about 460 nm.
  • the concentration of NADH and NAD + taken together in living cells is about 1 mM, corresponding to approximately 0.63 g/l of cells, meaning that a significant percentage of the dry matter in cells is comprised of NADH and NAD + .
  • the predetermined criteria of the at least one measured parameter for a biodegradation process or a phase thereof it is normal practice according to the invention to employ empirical calibration, i.e. a biodegradation process is monitored with respect to its input and output values of parameters of interest, and at the same time values of the measured parameter are recorded.
  • the chosen predetermined criteria or values for any given set of circumstances e.g. the nature of the apparatus, the composition, temperature and pH of the water being treated, etc.
  • parameters that may be controlled in a biodegradation process are oxygen concentration, biodegradable material loading, pH, temperature, turbidity, dosage rate of precipitation chemicals, dosage rate of additional readily biodegradable carbon-containing material, dosage rate of substances capable of converting not readily biodegradable material into readily biodegradable material, rate of recycling of activated sludge, inlet flow rate, outlet flow rate, stirring rate, oxygen dosage rate, air dosage (aeration) rate, total amount of activated sludge in the system, concentration of activated sludge in the aqueous medium, and other process parameters which are conventional in treatment processes of water, waste water or the like. All of these controlled parameters are well-known in the art as are the means of effecting their direct control.
  • the control of biodegradation according to the present invention is in particular performed by adjusting the oxygen concentration in the aqueous medium.
  • Adjustment of the oxygen concentration is typically performed by adjusting the aeration rate, i.e. the rate at which oxygen, air or another oxygen-containing mixture is introduced into the aqueous medium.
  • this is preferably performed by means of automatic monitoring of the measured parameter, e.g. NADH fluorescence, the obtained values for the measured parameter being used to determine the completion of a nitrification or denitrification phase as explained below.
  • This information regarding the status of a nitrification or denitrification phase is in turn used for regulating the inflow of air or oxygen by means of computer controlled set-points.
  • the determination of the end of a nitrification phase may in general be performed as follows: Following the end of a denitrification phase (which is represented by a peak in NADH fluorescence), the oxygen concentration of the aqueous medium is increased by adding oxygen or air to the medium. At fixed intervals, e.g. every 5 minutes, the fluorescence of the medium is measured.
  • the end of nitrification may be defined based on a comparison of the latest 3 determined values for fluorescence and using the following criteria:
  • F n is the fluorescence measured at time n
  • K is an empirically determined constant. This is explained in more detail in the examples below.
  • the determination of the end of nitrification in this manner is advantageous in that it is simple, inexpensive, accurate and reliable.
  • the result is an accurate identification of the point at which the nitrate content reaches a maximum and the ammonium content reaches a minimum, so that the supply of air or oxygen to the system can be cut off as soon as the aqueous medium no longer contains any ammonia that can be converted to nitrate.
  • One advantageous use of this knowledge is to be able to more accurately administer the addition of air or oxygen, in particular by avoiding unnecessary addition of air or oxygen for a period of time in which the ammonia has already been depleted. This in turn allows the nitrification/denitrification process to be performed more quickly and efficiently.
  • the present invention provides not only improved control of a biodegradation process, but also provides an improved and simplified method for determining the ammonia content of an aqueous medium.
  • the ammonia concentration can be readily determined using information on the elapsed time of a given nitrification phase and the speed of conversion of ammonia to nitrate. This assumes zero order kinetics in the conversion of ammonia to nitrate, which, however, has been found to be the case.
  • ammonia concentration of e.g. waste water in a waste water treatment process allows the ammonia concentration to be adjusted to provide the most efficient operation of the process. In addition, it allows the adjustment of other process parameters that also influence the overall process efficiency, for example the carbon content of the water.
  • the method for controlling biodegradation of waste water may be adapted to provide not only removal of nitrogen, but also removal of phosphorus.
  • a phase for biological removal of phosphorus is provided following the end of a denitrification phase.
  • Methods are known in the art for biological removal of phosphorus by an anaerobic process, typically by adding additional waste water to result in the release of bacterially bound phosphorus. Since such biological phosphorus removal takes place by an anaerobic process, the present invention is advantageous in that it makes it possible to precisely determine when the nitrate in the waste water has been depleted, as it is at this point that the necessary conditions for anaerobic removal of phosphorus are present.
  • the optimum phase duration for a biological phosphorus removal phase may be determined as a function of the denitrification time, the nitrification time, the temperature of the medium and the general level of fluorescence. Further information is provided below in the examples.
  • the present invention relates to an apparatus for controlling biodegradation of an aqueous medium containing biodegradable material comprising nitrogen-containing components, the apparatus comprising
  • a still further aspect of the invention relates to a waste water treatment plant comprising an apparatus as described above.
  • Figure 1 illustrates the level of oxygen, ammonia and fluorescence, respectively, in the waste water treatment plant over a period of 12 hours. It may be seen from Figure 1 that the plant operates with intermittent addition of oxygen to the waste water being treated, each addition of oxygen leading to a decrease in the ammonia concentration due to oxidation of ammonia to nitrate (nitrification). After a fixed period of time the oxygen supply is cut off and accumulated nitrate is reduced in the resulting low-oxygen environment to molecular nitrogen (N 2 ) (denitrification).
  • N 2 molecular nitrogen
  • the fluorescence changes over time in a manner that is the inverse of the changes in the oxygen concentration.
  • the fluorescence increases during the non-aerated denitrification phase from a minimum to a peak level.
  • a sharp drop in the level of fluorescence from a peak level to a lower level occurs. This drop can be separated into 2 phases: in the beginning the fluorescence drops off quickly, after which it falls off more slowly. The latter phase represents a delay of the fluorescence in reaching a minimum level after the initiation of an aerobic phase.
  • the higher the concentration of ammonia present in the medium the longer the time that passes before the minimum level of the fluorescence is reached after initiation of the aerobic phase. Further, the minimum level of fluorescence coincides with the moment when the ammonia is depleted.
  • N-, and N 2 two nitrification phases differing in initial ammonia concentration have been marked as N-, and N 2 , respectively. These phases can be subdivided into 2 distinct periods.
  • the initial periods ni and n 2 are periods with vigorous nitrification, while the subsequent periods and ns 2 effectively represent surplus nitrification time.
  • the distance between the 2 vertical unbroken lines delimiting n-i and n 2 respectively indicates the duration of the periods with vigorous nitrification. This coincides with the presence of ammonia. It is seen that a high initial ammonia concentration requires a long nitrification period (n 2 ), while a low initial ammonia concentration requires a short nitrification period (n ⁇ .
  • the corresponding denitrification phases D ⁇ and D 2 can in a similar way be separated into periods di and d 2 characterized by vigorous denitrification.
  • the subsequent periods dsj and ds 2 effectively represent surplus denitrification time.
  • the distance between the corresponding vertical unbroken lines delimiting d ⁇ and d 2 , respectively, indicates the duration the corresponding denitrification period. It can be seen that a long nitrification period (n 2 ) is followed by a long denitrification period (d 2 ), the subsequent denitrification phase. This is to be expected, as much nitrate has been formed from the high amount of ammonia in the preceding phase. Similarly, a short nitrification period (n ⁇ is seen to be followed by a short denitrification period (d-i). This information may be used as described below to control waste water treatment.
  • the periods ⁇ S T and ns 2 are periods during which the medium was unnecessarily aerated, since there was no ammonia left that could be nitrified. Since the present invention allows rapid identification of the end of a nitrification period, it makes it possible to eliminate such non-productive periods in the biodegradation process, so that the process as a whole can be run much more efficiently. It is estimated that this increased efficiency can provide a reduction in the overall biodegradation time of up to about 40%, which of course also means correspondingly very substantial reductions in operating costs. This will also make it possible to achieve increased capacity for a given waste treatment plant size, or alternatively, to reduce waste treatment plant size for a given waste water load.
  • the concentration of ammonia at the end of the phase preceding a nitrification phase is estimated from the fluorescence measurement. This estimation is carried out in 3 steps: 1. Identification of the event of ammonia depletion
  • Step 1 Identification of the event of ammonia depletion
  • T n The determination of the time when ammonia is depleted (T n ) is for example carried out in the following way:
  • k A is an empirical constant
  • Step 2 Calculation of the time consumed for the depletion of ammonia
  • the duration of the nitrification phase is calculated by subtracting the time of the start of the nitrification phase T 0 from the time when the depletion is identified according to the fluorimetric method desribed in step 1. If the conditions in equation 1 are fulfilled at time T n , then the depletion time is T n-2 . Accordingly:
  • Step 3 Estimation of the initial ammonia concentration from the time consumed for the depletion of ammonia
  • Figure 3 shows the empirical relationship between the ammonia concentration and the time consumed in depleting the ammonia ( ⁇ t NH3 ,coiour)- The figure shows a linear correlation.
  • Figure 4 shows the empirical relationship between the initial ammonia concentration and the time consumption estimated from the local fluorescence minimum ( ⁇ t NH3 , Ruor )- A linear correlation is also depicted in this case.
  • the initial ammonia concentration ([Ammonia] ⁇ n ⁇ tl ai)is estimated using the following equation.
  • r A is the slope of the linear regression line of Figure 4 and c A is the intercept.
  • r A is temperature-dependent and can be corrected using an Arrhenius expression.
  • the concentration of nitrate at the end of the phase preceding a denitrification phase is estimated from the fluorescence measurement in a manner analogous to the method described above for estimating the ammonia concentration. This estimation is carried out in 3 steps: 1. Identification of the event of nitrate depletion
  • Step 1 Identification of the event of nitrate depletion
  • T n The determination of the time when nitrate is depleted (T n ) is for example carried out in the following way: It is assumed that i) the tank is in a D-phase and ii) the fluorescence is recorded at discrete intervals, i.e. every 5 minutes ( Figure 1). At any event of fluorescence recording, the recorded value F n at time T n is compared to the preceding recorded value F n - ⁇ . The depletion of nitrate is recognized if the following criteria is fulfilled:
  • Step 2 Calculation of the time consumed for the depletion of nitrate
  • the duration of the denitrification phase is calculated by subtracting the time of the start of the denitrification phase T 0 from the time when the depletion is identified according to the fluorimetric method described in step 1. If the conditions in equation 1 are fulfilled at time T n , then the depletion time is T n . Accordingly:
  • Step 3 Estimation of the initial nitrate concentration from the time consumed for the depletion of nitrate
  • the initial nitrate concentration ([Nitrate] init , a i) is estimated using the following equation:
  • r N is a rate constant and c N is a constant.
  • r N is temperature-dependent and can be corrected using an Arrhenius expression.
  • the nitrogen removal process is carried out according to the following general scheme using 3 distinct phases.
  • the order of the 3 phases can be changed arbitrarily, and at least one of the phases can be omitted, if desired.
  • the phases are the nitrification phase, the denitrification phase and the simultaneous nitrogen removal phase (see WO 96/35644 for a detailed description of simultaneous nitrogen removal).
  • the nitrification phase and the denitrification phase are analytical phases in which the initial ammonia concentration and nitrate concentration may be estimated by means of the fluorescence measurements. Further information on the phases is listed in Table 2 below.
  • Example 1 N - DN - SIM - N - DN - SIM ...etc.
  • Example 2 N - SIM - DN - SIM - N - SIM - DN etc.
  • Example 3 the simultaneous denitrification is omitted
  • This case represents a common alternating nitrogen removing plant such as the one that produced the results presented in Figure 1
  • This type of plant uses a fixed oxygen set-point in the nitrification phase, and the oxygen set-point of the denitrification phase is zero
  • the duration of the individual phases in the practice of the invention is adjusted according to the concentration of nitrate and ammonia Additionally, the oxygen concentration of the two phases can be adjusted on the basis of the fluorescence measurement in a similar way as described for the SIM-phase below
  • the oxygen set-point in the SIM-phase is calculated from the above-described estimation of the initial concentration of ammonia and nitrate
  • the temperature is used to correct the nitrification and denitrification rates Furthermore, the actual fluorescence is used
  • fi, f 2 , f 3 and f 4 are functions that are fitted to empirical data fiis an increasing function of the initial ammonia concentration f 2 is a decreasing function of the initial nitrate concentration f 3 is a temperature correction expression f is a function of the fluorescence during the SIM-phase (cf WO 96/35644) These functions are optimized in order to make the treatment process cope as well as possible with the actual effluent requirements

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Abstract

On décrit un procédé permettant de contrôler la biodégradation d'un milieu aqueux contenant des matières biodégradables dans lesquelles sont présents des constituants contenant de l'azote, par exemple des eaux usées dans une installation de traitement des eaux usées; le procédé consistant à estimer la valeur d'au moins un paramètre qui représente la concentration en ammoniaque du milieu aqueux, par exemple la fluorescence NADH, à comparer la valeur estimée ou un groupe de valeurs estimées à des critères prédéterminés pour le ou les paramètres mesurés, et à ajuster la concentration en oxygène du milieu aqueux sur la base de la comparaison pour optimiser la biodégradation des constituants contenant de l'azote. Le procédé permet d'effectuer la détermination automatique et précise de la fin des phases de nitrification et de dénitrification, ceci permettant au procédé de biodégradation de se dérouler plus efficacement.
PCT/DK1998/000486 1997-11-10 1998-11-10 Procede de controle de la biodegradation WO1999024370A1 (fr)

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DK127697 1997-11-10

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Cited By (5)

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WO2001055717A1 (fr) * 2000-01-26 2001-08-02 Shw Hölter Wassertechnik Gmbh Procede de surveillance d'un systeme aqueux
FR2871153A1 (fr) * 2004-06-02 2005-12-09 Otv Sa Procede de traitement d'eaux a l'aide d'un reacteur biologique, dans lequel la vitesse d'air injecte dans le reacteur est regulee, et dispositif correspondant
EP1832556A1 (fr) * 2006-03-07 2007-09-12 Aqua Service Schwerin Beratungs- und Betriebsführungsgesellschaft mbH Procédé pour la mise en oeuvre d'une installation biologique pour l'épuration d'eaux usées
CN105906044A (zh) * 2016-06-17 2016-08-31 北京工业大学 厌氧氨氧化耦合反硝化除磷同步内源反硝化处理低碳城市污水的装置和方法
FR3078076A1 (fr) * 2018-02-21 2019-08-23 Centre National De La Recherche Scientifique (Cnrs) Methode d'evaluation de la teneur en matiere organique biodegradable d'un echantillon aqueux et kit pour sa realisation

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JPH0380997A (ja) * 1989-08-25 1991-04-05 Fujitsu Ltd 排水処理方法および装置
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WO1990010083A1 (fr) * 1989-02-28 1990-09-07 Aktieselskabet Faxe Kalkbrud Procede de regulation et/ou de controle de processus biologiques
JPH0380997A (ja) * 1989-08-25 1991-04-05 Fujitsu Ltd 排水処理方法および装置
US5552319A (en) * 1993-07-20 1996-09-03 Biochem Technology, Inc. Apparatus and method for monitoring and controlling biological activity in wastewater and controlling the treatment thereof

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001055717A1 (fr) * 2000-01-26 2001-08-02 Shw Hölter Wassertechnik Gmbh Procede de surveillance d'un systeme aqueux
FR2871153A1 (fr) * 2004-06-02 2005-12-09 Otv Sa Procede de traitement d'eaux a l'aide d'un reacteur biologique, dans lequel la vitesse d'air injecte dans le reacteur est regulee, et dispositif correspondant
WO2006000680A1 (fr) * 2004-06-02 2006-01-05 Otv Sa Procede de traitement d'eaux a l'aide d'un reacteur biologique, dans lequel la vitesse d'air injecte en continu dans le reacteur est regulee, et dispositif correspondant
US7407584B2 (en) 2004-06-02 2008-08-05 Otv Sa S.A. Regulating air velocity continuously injected into biological water treatment reactor
CN1997602B (zh) * 2004-06-02 2011-04-20 威立雅水务解决方案与技术支持联合股份公司 使用其中调节连续注入到反应器中的空气速度的生物反应器的水处理方法和相应的设备
EP1832556A1 (fr) * 2006-03-07 2007-09-12 Aqua Service Schwerin Beratungs- und Betriebsführungsgesellschaft mbH Procédé pour la mise en oeuvre d'une installation biologique pour l'épuration d'eaux usées
CN105906044A (zh) * 2016-06-17 2016-08-31 北京工业大学 厌氧氨氧化耦合反硝化除磷同步内源反硝化处理低碳城市污水的装置和方法
CN105906044B (zh) * 2016-06-17 2018-12-18 北京工业大学 厌氧氨氧化耦合反硝化除磷同步内源反硝化处理低碳城市污水的装置和方法
FR3078076A1 (fr) * 2018-02-21 2019-08-23 Centre National De La Recherche Scientifique (Cnrs) Methode d'evaluation de la teneur en matiere organique biodegradable d'un echantillon aqueux et kit pour sa realisation
WO2019162618A1 (fr) * 2018-02-21 2019-08-29 Centre National De La Recherche Scientifique Methode d'evaluation de la teneur en matiere organique biodegradable d'un echantillon aqueux et kit pour sa realisation

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