Classifications

• • 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
  • C02F3/00—Biological treatment of water, waste water, or sewage
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/16—Nitrogen compounds, e.g. ammonia
• • 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
  • C02F2209/38—Gas flow rate
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/02—Aerobic processes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

• the present invention relates to the field of water treatment. More precisely, the invention relates to the treatment of urban or industrial effluents by a process for eliminating nitrogen and carbon pollution by means of a biomass in free culture or fixed on a solid material.
• a conventional water depollution technique uses a biological reactor such as a biofilter or activated sludge. According to this technique, the reactor is ventilated to ensure the treatment of the pollution.
• the prior art is most often based on two distinct treatment phases, one requiring oxygen, nitrification (N), and the other its absence, denitrification (DN).
• the two phases of the process can be carried out either in a single reactor with periods of aeration and then without aeration (sequenced aeration), or in a reactor equipped with two specific compartments (one aerated continuously, the other never) .
• the invention consists in carrying out these two antagonistic reactions (nitrification / denitrification) simultaneously in the same reactor without specific compartmentation dedicated to one or other of the reactions and with permanent aeration.
• the level of this aeration must be properly controlled because the more oxygen available in the reactor is in excess, the more denitrification is inhibited and vice versa.
• the overall efficiency of the depollution process depends directly on the adjustment of the aeration.
• This technique requires the use of a reference Ct which itself depends on the pollution to be treated.
• the difficulty lies in the fact that the pollutant load varies over time and it is therefore necessary to change this reference Ct regularly so that it is always consistent, which excludes the application in the case of strongly effluent. variable.
• Other techniques use linear combinations of the input variables of the system (ammonium, nitrates, etc.) to calculate the airflow control to be applied, as described in particular in the international application published under the number WO 93 / 07089. However, these techniques rely on empirical or semi-empirical modeling. The control functions used are based essentially on the data resulting from the experience of previous operations.
• the regulation of the aerated volume is based on compartmentalisation of the reactor (and not on the regulation of a flow rate or a gas velocity).
• the fundamentally discrete nature (discontinuous variation of the aerated volume) of this type of strategy encourages the authors to always complete their system by a regulation of the dissolved oxygen.
• the majority of publications are based on results from simulation (Activated Sludge Model) or batch tests with synthetic waters. In practice, few pilot-scale or on-site experiments have been conducted. In addition, the experiments conducted concern almost exclusively activated sludge biological reactors.
• the invention particularly aims to overcome the disadvantages and / or shortcomings of the prior art.
• the invention aims to propose a water treatment method using a biological reactor, not compartmentalized, incorporating a biomass aerated by a continuous air injection in which the control of the air injection is optimized over the techniques of the prior art.
• the objective of the invention is to simultaneously carry out the nitrification and denitrification steps as well as the carbon abatement, in the same enclosure and at the same time.
• the invention also aims to provide such a method that is effective in all circumstances, including when the polluting load of the water to be treated has significant variations over time.
• Another object of the invention is to provide such a method which makes it possible to adjust the injected air control as a function of the biomass performances.
• Another objective of the invention is to provide such a method which makes it possible to envisage relatively rapid returns on investment and gains in operation.
• the object of the invention is to propose such a method which makes it possible to avoid the additional operating costs generated by daily pollutant load peaks.
• It is another object of the invention to provide such a method which allows the control of injected air without the need for dissolved oxygen measurements.
• Yet another object of the invention is to provide such a method which is easy to implement.
• a water treatment process including nitrification and denitrification processes within the same enclosure of a biological reactor for reducing the nitrogen pollution, said incoming charge, contained in said water, said reactor incorporating a biomass aerated by oxygenated gas injection, said method including at least one step of regulating the speed of said injected gas, characterized in said gas injection is continuous and in that said nitrification and denitrification processes are essentially simultaneous, said method comprising a continuous measurement of said incoming charge of N-NH 4 (Cv EDD ) contained in said waters, said measured incoming charge being weighted by a time shift to deduce a control of the speed of said gas to be injected as a function of time.
• Cv EDD N-NH 4
• the method according to the invention is based on a direct measurement of the load as an input parameter of a mathematical model for predicting air requirements (or more generally oxygen requirements). In this way, as will become clearer later, a water treatment process is obtained which gives a more efficient and precise control than the prior art processes.
• This control allows a continuous but variable injection of gas corresponding to the needs of the biomass and simultaneously allowing nitrification and denitrification.
• This temporal shift (which can be scalable) by which the measurement of the incoming charge is weighted makes it possible to take into account in particular the offset linked to the transit of the measurement point instead of degradation.
• This shift related to the transit substantially corresponds to the shift between the actual moment when the water enters the reactor and the moment when the ammonium begins to be degraded.
• This shift in the reactor passage time or the average residence time is also taken into account.
• a particularly interesting result of such a method is that it allows to limit over or under aeration during daily pollutant load peaks that generate additional operating costs.
• the present invention thanks to significant performance gains, allows a quick return on investment: from 1 to 2 years.
• the process according to the invention can be applied to biofilters as well as to most water treatment processes, such as in particular activated sludge including membrane bioreactors, fixed culture processes such as biofilters, fluidized beds, and mixed-culture processes.
• the reasoning leading to the establishment of such a trend control law is explained in detail below.
• the objective of the control law is to connect the feedstock of incoming N-NH4 (in kg N-NH4 / m 3 of aerated reactor / J) in the biological reactor to the air flow rate and then to the air velocity.
• incoming charge of N-NH4 being the charge actually applied to the reactor, that is to say the one evaluated from the mixture of the settled water and recirculated water.
• This variable makes it possible to simultaneously take into account variations in flow and concentration.
• it is a sizing parameter for industrial sites.
• the actual charge eliminated is constant for a given air flow over a 24-hour horizon. This assumption is verified by the analysis of several constant air flow buffered water tests.
• the relation obtained does not yet take into account the transient phenomena.
• One of the peculiarities of the invention therefore lies in taking transient phenomena into account in order to obtain the parameters of the preceding relation. Indeed, to connect the removed charge to the air velocity, it is necessary to take into account the passage time in the reactor or the average residence time Tg (average transit time of a fluid particle in a reactor considered).
• the Tg parameter is obtained practically by studying the cross-correlation coefficient connecting the diluted decanted water concentration (decanted water + recirculated water) to the output measurement of the process.
• this method does not take into account the actual moment when the diluted decanted water enters the reactor and where the ammonium begins to be degraded, offset due to the transit of the measurement point instead of degradation. Likewise, it does not take into account the aeration variation that probably does not have an immediate effect and the hydraulics of the system. All of these phenomena induce a dispersion of the values (as shown in Figure 2 in the case of a biofilter) and therefore an uncertainty on the air velocity to be applied up to ⁇ 15% around 7 Nm / h.
• the oxygen requirement for the biological reactor is therefore expressed as the sum of the previous needs. Air requirements arise from these oxygen requirements. Indeed, a relationship links them with the transfer efficiency, whose value decreases with air speed.
• Figure 3 is a graph for comparing empirical 32 and theoretical 31 air demand for a biofilter. This graph shows that the theoretical air requirements thus calculated agree well with the empirical law.
• the term Cv (t + ⁇ t) makes it possible to anticipate a future variation of the setpoint of the output load.
• said phase delay function is of the type:
• n is an adjustment parameter of the diffusion in said reactor or said reactors; V is the apparent volume of said one or more biological reactors; - Q is the feed rate of said water to be treated; - s is the Laplace transform of the variable t.
• This function corresponds to the transfer function in the Laplace space of a series of n perfectly stirred reactors (RPA), n being a positive integer and not zero.
• This phase delay function here takes the mathematical form of a series of perfectly stirred reactors (RPA) whose parameters are flow and volume. The flow rate is slaved to that of filtration of the column because only the apparent volume V is used to adjust the function. More generally, all mathematical expressions using ideal reactor transfer function combinations can be used.
• the phase delay function can therefore be of different types according to other possible embodiments.
• the process comprises at least one step of measuring an outlet charge (CV 5 ) and / or a dissolved ammonium concentration contained in said treated water.
• the present invention provides a continuous correction to the prediction model so as to always be in adequacy with reality.
• a feedback term In fact, one can compensate for errors in the trend model or non-measurable disturbances by adding a feedback term.
• a closed loop with a tendency to take a trend makes it possible to obtain much better results than a "FeedForward" or "FeedBack” regulator alone.
• One of the specificities of feedback is therefore the evaluation of the error. Indeed, it is not only a difference between the measurement of dissolved ammonium output and the setpoint (denoted e (t)), but of a difference between an output charge and a charge of setpoint (noted error (t)).
• the difference between these two parameters is fundamental.
• said measurement of an outlet charge (Cv s ) and / or a dissolved ammonium concentration contained in said treated water is carried out continuously.
• the controller implicitly takes into account the variations of the feed rate for the calculation of the action to be applied.
• the invention also relates to a device for implementing the water treatment method including nitrification and denitrification phase within the same enclosure of a biological reactor as described above, said reactor incorporating an aerated biomass by air injection and means for regulating the speed of said injected air, characterized in that it comprises: means for continuously measuring said incoming charge; means for setting an output load setpoint and / or an output concentration (Cv C0NSIGN ); calculation means intended to act on said regulation means on the basis of a control law in which said measured incoming charge is weighted in particular by a time shift for deriving a control of the speed of said air to be injected as a function of time, said air injection being continuous and said nitrification and denitrification processes being essentially simultaneous.
• a device for implementing the water treatment method including nitrification and denitrification phase within the same enclosure of a biological reactor as described above, said reactor incorporating an aerated biomass by air injection and means for regulating the speed of said injected air,
• the device comprises a feedback loop comprising means for measuring an exit charge (Cv s ) and / or a dissolved ammonium concentration contained in said treated water, and means of comparison. of said output load with said output load setpoint.
• said comparison means are preferably connected to said calculation means, in order to adjust said setpoint taken into account in said control law.
• FIG. 1 is a graph showing the variations of the ammonium concentration at constant load, in buffered water
• FIG. 2 shows two air velocity readings as a function of the eliminated charge calculated for a biofilter
• FIG. 3 is a graph showing a comparison of empirical and theoretical air demands for a biofilter
• FIG. 4 is a schematic view of a pilot unit according to the invention
• FIG. 5 is a schematic representation of a "Feedback / Feedformward" control block according to the invention
• FIG. 6 shows the curves of readings obtained with the method according to the invention, with feed rate and fixed recirculation rates;
• FIG. 7 shows the curves of readings obtained with the method according to the invention, with variable feed rate and fixed recirculation rates; - Figure 8 shows the survey curves obtained with the method according to the invention, variable feed rate and recirculation rate.
• the efficiency of the method according to the invention is demonstrated below by means of tests carried out using a pilot unit as shown in FIG. 4. As it appears, this unit is composed of two Plexiglas columns with a height of 5 m and an inside diameter of 29 cm. The material height (h matt) used for the simultaneous Nitrification / Denitrification (NDN) tests is 2.75 m and the average diameter of the balls which constitute it is 3.34 mm ⁇ 0.19 mm.
• the treated effluent comes from an urban water network; it undergoes a primary settling (lamellar decanter) before being conveyed gravitarily in a buffer tank 42 of 30 liters stirred continuously.
• the influent is then raised via two SEEPEX pumps to fill the two loading columns. These offer a maximum available pressure drop of 2.40 mCe.
• a fraction 43 of the treated water is reused as part of the nitrification / denitrification to feed the pilot. This water is mixed with the feed water in the loading columns.
• two Seepex pumps make it possible to recirculate the desired flow rates.
• the non-recirculated treated water 44 from the two columns is mixed in a common tank of 10 liters from which the samples to be analyzed are taken.
• the driver works like a site with two filtration cells. This homogenizes the processing and is mainly redundant online measures.
• Two air ramps (not shown) located 20 cm from the bottom of each column can inject the process air continuously but variable throughout the reactor, and two other holes located at the bottom of each of them allow injection of air wash. In both cases, the production of air is provided by a compressed air network.
• the load applied during the tests calculated on the totality of the material, is between 0.3 and 0.6 kg N-NH4 / m3 / J for an average of 0.45 kg N-NH4 / m3 / J.
• the corresponding mean feed velocity V 6311 is 1.2 m / h for an average recirculation rate of 125%.
• FIG. 6 thus illustrates that it is possible to eliminate the peak of daily load by anticipating the air requirements. There is no under or over-aeration zone, before and after the load peak, contrary to the state of the art above.
• a water to be treated 51 is directed to a biological reactor 52, the feed rate data Q and incoming load being associated with this water to be treated.
• the nitrification and denitrification processes are carried out within the same chamber of the reactor (the reactor having in this case a single compartment) and that these processes of nitrification and denitrification are essentially simultaneous. Measurements are made concerning this water to be treated using a first regulator 53, called “Feedforward" regulator, which notably performs a continuous measurement of the charge between C VEDD .
• the controller also receives information about the output load setpoint Cv C0NSIGNE .
• Another regulator 54 called “Feedback", makes it possible to collect information, and in particular the output load C vs measured continuously.
• the regulator 54 also receives the information concerning the output load setpoint Cv C0NSIGNE .
• the controller used for the feedback loop can be of the PID (Proportional Proportional Controller) or PFC (Predictive Functional Control) type. These controllers are set to each issue a command.

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• Life Sciences & Earth Sciences (AREA)
• Water Supply & Treatment (AREA)
• Organic Chemistry (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Biodiversity & Conservation Biology (AREA)
• Chemical & Material Sciences (AREA)
• Microbiology (AREA)
• Health & Medical Sciences (AREA)
• Molecular Biology (AREA)
• Purification Treatments By Anaerobic Or Anaerobic And Aerobic Bacteria Or Animals (AREA)
• Activated Sludge Processes (AREA)
• Biological Treatment Of Waste Water (AREA)
• Feedback Control In General (AREA)

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• 2004
  • 2004-06-02 FR FR0405970A patent/FR2871153B1/fr not_active Expired - Fee Related
• 2005
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