Method for controlling a wastewater treatment plant and associated wastewater treatment plant

Abstract

Method for controlling a wastewater treatment plant and associated wastewater treatment plant. The present invention relates to a method for controlling a wastewater treatment plant comprising a primary treatment system and a secondary treatment system; the method comprising the following steps: - measurement (110) in the primary treatment system of at least one first-type parameter characterizing the treated water; - determination (120) of at least one second-type parameter from the measured first-type parameter(s), the second-type parameter(s) characterizing the organic matter content of the treated water; - control (130) of the carbon content in the secondary treatment system as a function of the second-type parameter(s). Figure for the abstract: Figure 4

Description

Title of the invention: Method for controlling a wastewater treatment plant and associated wastewater treatment plant

[0001] The present invention relates to a method for controlling a wastewater treatment plant.

[0002] The present invention also relates to a wastewater treatment plant implementing such a process.

[0003] As is known in itself, wastewater treatment takes place at several levels, the implementation of which is generally governed by the regulations in force.

[0004] Typically, in a first stage of treatment, wastewater is placed in a primary clarifier. Such a clarifier has a tank in which heavy solids settle to the bottom and lighter materials such as colloids and greases rise to the surface. The materials that have accumulated at the bottom of the tank can then be removed and are called primary sludge. The materials on the surface can be removed directly. The clarified water then passes into a second stage of treatment.

[0005] In this second level, materials containing nitrogen and / or carbon and / or phosphorus are eliminated using biological treatment by bacteria.

[0006] Finally, in a third treatment stage, the treated water undergoes further filtration before being discharged into a sensitive ecosystem. This final treatment may include phosphorus removal, filtration, disinfection, and micropollutant removal.

[0007] The best-known biological process for removing nitrogen from wastewater in the second treatment stage includes the implementation of successive nitrification / denitrification steps.

[0008] Indeed, the nitrification step of this process includes the oxidation of ammonia to nitrite and then the oxidation of nitrite to nitrate. This step is carried out by bacteria under aerobic conditions, that is, with access to oxygen. Thus, the implementation of this nitrification step requires sufficient aeration.

[0009] The denitrification step, for its part, includes the reduction of nitrates to nitrite and then the reduction of nitrite to dinitrogen, a gas that can be released, for example, into the atmosphere. This step is also carried out by bacteria but under anoxic conditions, that is to say, without access to oxygen.

[0010] Depending on current regulations, the total permissible nitrogen discharge limit imposes significant limitations on the structure and design of wastewater treatment plants. Lowering this permissible limit results in a longer and more expensive nitrification stage. Furthermore, low nitrogen discharge limits are difficult to achieve using only a biological process. Thus, in most cases, the addition of carbon from an external source is necessary to implement the denitrification stage.

[0011] In the prior art, most methods for controlling wastewater treatment plants focus on controlling aeration during the nitrification stage. Aeration can thus account for up to 25% of the operating costs of such plants. However, this control is not optimal, and often, excess carbon is used to implement the denitrification stage. This then leads to excessive operating costs for current wastewater treatment plants. These costs are primarily due to the suboptimal use of resources.

[0012] The present invention aims to solve this problem and to provide means of controlling a wastewater treatment plant that optimize resource consumption by such a plant, while respecting the permitted discharge limits for nitrogen and phosphorus. The invention thus makes it possible to optimize the operating costs of such a wastewater treatment plant.

[0013] To this end, the invention relates to a method for controlling a wastewater treatment plant comprising a primary treatment system and a secondary treatment system, the primary treatment system comprising a primary clarifier configured to separate primary sludge from treated water, the secondary treatment system comprising a nitrification device and a denitrification device for treated water.

[0014] The process comprises the following steps:

[0015] - measurement in the primary processing system of at least one first parameter type characterizing treated water;

[0016] - determination of at least one second type parameter from the or each first type parameter measured, the second type parameter(s) characterizing the organic matter content of the treated water;

[0017] - control of the carbon content in the secondary treatment system function of the or each parameter of the second type.

[0018] Advantageously, the second type parameter or parameters also characterize the concentration of ammoniacal nitrogen and phosphorus.

[0019] Thanks to these characteristics, the invention makes it possible to observe the parameters of wastewater characterizing the organic matter content and to adapt the content of carbon in the secondary treatment system is adjusted according to these parameters. This adaptation can be done practically in real time, thus optimizing the amount of carbon needed to implement, in particular, the denitrification stage in the wastewater treatment plant.

[0020] Unlike prior art methods, which do not allow observation of these parameters characterizing the organic matter content of wastewater, the invention makes it possible to deduce such parameters practically in real time using other types of parameters that are more easily observable in a wastewater treatment plant. Furthermore, by knowing the organic matter content of the wastewater practically in real time, it is possible to optimally adjust the amount of carbon required to implement the denitrification process.

[0021] In the prior art, such parameters characterizing the organic matter content of wastewater are generally measured under laboratory conditions, which does not allow for the characterization of the organic matter content of the treated water at a given moment and therefore does not allow for the adaptation of the operation of the wastewater treatment plant in real time. These measurements used in the prior art are therefore of very little interest in such a context.

[0022] It should also be noted that direct measurements of parameters characterizing the organic matter content of wastewater, for example in a wastewater pipe, are generally not possible due to the complexity of the sensors required to perform this task (UV sensors, for example). Thus, only laboratory measurements of such parameters are generally available.

[0023] According to some embodiments, the step of determining the parameter or each of the second type is implemented with a repetition frequency of less than 1 hour, advantageously less than 10 min and preferably less than 5 min.

[0024] According to some embodiments, the carbon content control step is implemented with substantially the same repetition frequency as the step determining the parameter or each parameter of the second type.

[0025] Thanks to these characteristics, it is possible to obtain measurements characterizing the organic matter content of the treated water as quickly as possible and therefore to adapt the operation of the wastewater treatment plant practically in real time.

[0026] According to certain embodiments, the parameter or each parameter of the first type is chosen from the group comprising the following elements characterizing treated water:

[0027] - pH;

[0028] - oxygen content;

[0029] - redox potential;

[0030] - turbidity;

[0031] - electrical conductivity;

[0032] - temperature;

[0033] - flow rate.

[0034] The aforementioned elements are easily measurable in real time by simple and inexpensive sensors. Moreover, these sensors can easily be used to characterize wastewater.

[0035] According to certain embodiments, the parameter or each parameter of the second type is chosen from the group comprising the following elements characterizing the organic matter content of the treated water:

[0036] - concentration of suspended matter;

[0037] - biochemical oxygen demand (BOD);

[0038] - chemical oxygen demand (COD).

[0039] Thanks to these characteristics, it is possible to accurately characterize the organic matter content of treated water. These parameters are known per se but can generally only be measured directly under laboratory conditions or using complex sensors. These sensors are generally expensive and difficult to adapt for use in wastewater treatment plants.

[0040] According to some embodiments, the measurement of at least one first type parameter is carried out upstream and / or downstream of the primary clarifier.

[0041] It should be noted that in some cases, all the first-type parameters are measured only upstream, and in some other cases, all of these parameters are measured only downstream of the primary clarifier. In some other cases, at least some of these parameters are measured upstream and at least some other parameters are measured downstream of the primary clarifier.

[0042] This may, for example, depend on the nature of the first type parameter being measured. For example, in some cases it is advantageous to measure the turbidity and temperature of the treated water upstream of the primary clarifier, while the other parameters are measured downstream of it.

[0043] According to some embodiments, the determination of the parameter or each parameter of the second type is carried out using a mathematical model, preferably the mathematical model being determined by a machine learning technique and / or by a statistical technique and / or by a mechanistic technique.

[0044] Thanks to these characteristics, it is possible to establish links between the first-type parameters measurable in wastewater treatment plants and the second-type parameters which are then difficult to measure in such installations. The mathematical model can be determined using one of the aforementioned techniques or a combination thereof. Furthermore, the nature of the mathematical model can be chosen, for example, based on the nature of the measured first-type parameters.

[0045] According to some embodiments, the control of the carbon content in the secondary treatment system is carried out by controlling a redirection of the primary sludge into the secondary treatment system.

[0046] Thanks to these characteristics, it is possible to utilize the carbon naturally contained in the primary sludge. The redirection of this primary sludge into the secondary treatment system can be carried out via a dedicated conduit arranged, for example, between the primary sludge outlet of the primary clarifier and the inlet of the secondary treatment system. Redirection control can, for example, be achieved by means of a valve and a pump controlling the flow rate of the fluid flowing through this conduit.

[0047] Thus, in such a case, the need for a chemical carbon source can be minimized.

[0048] According to some embodiments, the control of the carbon content in the secondary treatment system is carried out by controlling the addition of carbon from an external source into the secondary treatment system, preferably into the denitrification device.

[0049] Thanks to these features, carbon content can be easily controlled by adjusting the addition of carbon from an external source. This requires only minor modifications to existing wastewater treatment plants, as such an addition is generally provided for in the design of these plants.

[0050] Furthermore, it is advantageous to make such an addition directly in the denitrification device because this is the main point of carbon consumption.

[0051] According to some embodiments, the control of the carbon content in the secondary treatment system is carried out by controlling an internal recirculation between the denitrification device and the nitrification device.

[0052] Thanks to these characteristics, it is possible to reuse the biological carbon naturally contained in the internal recirculation flow between the denitrification device and the nitrification device.

[0053] It is therefore possible to minimize the need for carbon input from an external source.

[0054] According to some embodiments, the control of the carbon content in the secondary treatment system is carried out by controlling chemical reagents in the primary clarifier.

[0055] Thanks to these characteristics, it is possible to influence the production of primary sludge in the primary clarifier. Thus, the carbon content in the secondary treatment system can also be controlled.

[0056] It should be noted that all the aforementioned techniques for controlling carbon content in the secondary treatment system can be combined with each other in any technically possible combination.

[0057] It should also be noted that the implementation of these control techniques or a combination of these techniques can be chosen according to the nature of the available measured parameters or according to the values ​​of at least some of these parameters or according to the values ​​of second type parameters.

[0058] The invention also relates to a wastewater treatment plant comprising a primary treatment system and a secondary treatment system, the primary treatment system comprising a primary clarifier configured to separate primary sludge from treated water, the secondary treatment system comprising a nitrification device and a denitrification device for the treated water;

[0059] the processing installation further comprising:

[0060] - a measurement module in the primary processing system of at least one first type parameter characterizing treated water;

[0061] - a first processing module configured to determine at least one parameter of the second type from the one or each parameter of the first type measured, the one or each parameter of the second type characterizing the organic matter content of the treated water;

[0062] - means for controlling the carbon content in the secondary system of treatment based on the second type parameter(s).

[0063] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which: - [Fig.1] [Fig.2] [Fig.3] Figures 1 to 3 are schematic views illustrating a wastewater treatment plant including means for controlling carbon content according to the first, second, and third embodiments respectively; - [Fig.4] [Fig.4] is a flowchart of a control method according to the invention, the method being implemented by the processing installation of one of the preceding figures.

[0064] Fig. 1 illustrates a wastewater treatment plant 10 according to the invention.

[0065] Such an installation 10 is usable for treating wastewater from a wastewater collection system extending across a geographical area predetermined, such as a city, an urban area or a group of municipalities.

[0066] With reference to [Fig.1], the treatment plant 10 comprises a primary treatment system 21 connected to the wastewater collection system, a secondary treatment system 22 connected downstream of the primary treatment system 21, a sludge treatment system 25 connected to the primary 21 and secondary 22 treatment systems, and a control system 28.

[0067] In some examples, the treatment facility 10 may also include a tertiary treatment system (not shown) connected downstream of the secondary treatment system 22.

[0068] The primary treatment system 21 includes a primary clarifier 31 and a measuring module 32.

[0069] The primary clarifier 31 is configured to separate primary sludge from the treated water and inject the clarified water into the secondary treatment system 22. In some cases, the primary clarifier 31 is also configured to separate light materials, such as grease and sand, from the treated water. It can also sometimes be connected to pretreatment systems such as screens, grit chambers, and oil separators.

[0070] In particular, the primary clarifier 31 has a reservoir suitable for storing a predetermined volume of wastewater and includes an inlet 35, a first outlet 36 and a second outlet 37.

[0071] The inlet 35 of the primary clarifier 31 is connected to the wastewater collection system and thus allows this wastewater to be received directly into the primary clarifier 31.

[0072] The first outlet 36 of the primary clarifier 31 allows heavy solids formed by decantation of the treated water in the primary clarifier 31 to be evacuated from the primary clarifier 31.

[0073] This first outlet 36 is, for example, located at the bottom of the tank forming the primary clarifier 31 and is connected to the sludge treatment system 25 by a discharge circuit 38. The solid matter formed by the settling of the treated water in the primary clarifier 31 is called primary sludge. The discharge circuit 38 then allows this primary sludge to be conveyed to the sludge treatment system 25.

[0074] The second outlet 37 of the primary clarifier 31 allows clarified water following decantation by the primary clarifier 31 to be transmitted to the secondary treatment system 22.

[0075] Advantageously, each of the outlets 36, 37 is equipped with a remotely controllable valve, for example by the control system 28. Thus, these outlets can to be opened / closed according to business rules ensuring the proper functioning of the primary clarifier 31 and more generally of the primary treatment system 21.

[0076] The measuring module 32 allows for the direct measurement of at least certain parameters relating to the water treated by the primary treatment system 21.

[0077] In particular, the parameters measured by this measuring module 31 are hereafter referred to as first type parameters.

[0078] Each first-type parameter is chosen from the group comprising the following elements characterizing treated wastewater: pH; - oxygen content; - oxidation-reduction potential (ORP); - turbidity; - electrical conductivity; - temperature ; - Speed.

[0079] To measure these first-type parameters, the measuring module 32 includes one or more sensors known in themselves.

[0080] In the example of [Fig. 1], the measuring module 32 is arranged entirely upstream of the primary clarifier 31.

[0081] This means that all the sensors of this measuring module 32 are arranged upstream of the primary clarifier 31, for example in a conduit connecting the inlet 35 of the primary clarifier 31 and the wastewater collection system.

[0082] According to another embodiment (not illustrated), the measuring module 32 is arranged entirely downstream of the primary clarifier 31.

[0083] Thus, for example, this measuring module 32 can be arranged between the second output 37 of the primary clarifier 31 and the secondary treatment system 22. This means that all the sensors of this measuring module 32 are arranged, for example, in a circuit connecting the second output 37 of the primary clarifier 31 to the secondary treatment system 22.

[0084] According to yet another embodiment (not illustrated), at least some of the sensors of the measuring module 32 are arranged upstream of the primary clarifier 31 and at least some other sensors are arranged downstream of this primary clarifier 31.

[0085] The upstream sensors and the downstream sensors can be chosen according to the nature of the first type parameter measured by these sensors.

[0086] Thus, for example, sensors measuring turbidity or temperature can be arranged upstream of the primary clarifier 31 and sensors measuring other parameters can be arranged downstream of this primary clarifier 31.

[0087] It is also possible that sensors measuring the same first-type parameter are arranged upstream and downstream of the primary clarifier 31.

[0088] In such a case, the measurements retained by such sensors present, for example, an average between the measurements delivered downstream and upstream of the primary clarifier 31.

[0089] The measuring module 32 is also connected to the control system 28 and allows the measurements generated by its sensors to be delivered to this control system 28.

[0090] Advantageously, the measurement frequency by the measurement module 32 is less than one hour, advantageously less than ten minutes and preferably less than or equal to five minutes.

[0091] It is also possible that the measurements relating to at least some of the parameters are taken with different frequencies.

[0092] The secondary treatment system 22 makes it possible to implement a biological treatment process for the treated water in order in particular to remove nitrogen contained in this water.

[0093] To do this, the secondary treatment system 22 includes a phosphorus removal device 41, a denitrification device 42, a nitrification device 43 and a secondary clarifier 44.

[0094] In the example of [Fig. 1], the phosphorus removal device 41 is connected directly to the inlet of the secondary treatment system 22, the denitrification device 42 is connected downstream of the phosphorus removal device 41, and the nitrification device 43 is connected downstream of the denitrification device 42. Furthermore, the secondary clarifier 44 is connected downstream of these devices 41 to 43. These connections are made by means of a main circuit 45. Other types of connection and arrangement of these different devices are also possible, as will be explained in more detail later.

[0095] The phosphorus removal device 41 removes phosphorus from the water received by the secondary treatment system 22 using anaerobic bacteria. In some embodiments, the secondary treatment system 22 does not have a phosphorus removal device 4L

[0096] The nitrification device 43 allows ammonium (NH4+) to be oxidized to nitrate (NO3) under aerobic conditions using aerobic bacteria.

[0097] The nitrification process implemented by this nitrification device 43 takes place in two stages. The first stage consists of the oxidation of ammonium (NH4+) to nitrite (NO2). The second stage consists of the oxidation of nitrite (NO2) to nitrate (NO3). In other words, the nitrification process can be expressed by the following resulting chemical formula:

[0098] NH4+ + 2O2 -> NO3 + 2H+ + H2O

[0099] The nitrification device 43, for example, includes equipment to ensure the necessary oxygen (O2) supply by aeration.

[0100] The denitrification device 42 allows the conversion of nitrates (NO3) into dinitrogen (N2) which then presents a gas which can be released, for example into the atmosphere.

[0101] The reaction carried out by the denitrification device 42 is catalyzed by anaerobic bacteria, that is to say, by bacteria placed in anaerobic, advantageously anoxic, conditions. Denitrification also takes place in two stages.

[0102] The first step consists of reducing nitrates (NO3) to nitrite (NO2) by bacteria and the second step consists of reducing nitrite (NO2) to dinitrogen (N2) also by bacteria.

[0103] In other words, the denitrification process can be expressed by the following resulting chemical formula:

[0104] 2 NO3 + 10 e + 12 H+ -> N2 + 6 H2O

[0105] The need for electrons c is ensured by the addition of carbon as will be explained in more detail later.

[0106] The denitrification device 42, for example, features a non-aerated structure or equipment to ensure the necessary anoxic conditions.

[0107] The circulation of treated water between the denitrification device 42 and the nitrification device 43 is recirculated by an internal recirculation circuit 46. In particular, the internal recirculation circuit 46 extends in the example of [Fig.1] between the part of the main circuit 45 connecting the nitrification device 43 to the secondary clarifier 44, and the part of the main circuit 45 connecting the phosphorus removal device 41 to the denitrification device 42.

[0108] The circulation of treated water in this internal recirculation circuit 46 is controlled by a recirculation valve or pump 47 which allows the flow rate of treated water to be regulated between the internal recirculation circuit 46 and the part of the main circuit 45 connecting the nitrification device 43 to the secondary clarifier 44.

[0109] The control of this valve or this recirculation pump 47 is carried out for example by the control system 28 according to business rules.

[0110] In other embodiments, the denitrification devices 42 and nitrification devices 43 are arranged / connected differently. In particular, in some examples, the nitrification device 43 is located upstream of the denitrification device 42. In other examples, the denitrification devices 42 and nitrification devices 43 are combined within a single device. In these cases, the internal recirculation circuit 46 may not be required.

[0111] The secondary clarifier 44 includes a first inlet 55 connected to the nitrification device 43 (or the denitrification device 42) via the circuit main 45, a first outlet 44 connected to the sludge treatment system 25 and a second outlet 57 connected to the outlet of the secondary treatment system 22.

[0112] Just like the primary clarifier 31, the secondary clarifier 44 has a tank for separating solid matter from treated water.

[0113] Thus, the first outlet 56 of the secondary clarifier 44 is, for example, located at the bottom of the tank forming the secondary clarifier 44 and allows these solid materials to be evacuated from the secondary clarifier 44. These solid materials are called biological sludge.

[0114] The second outlet 57 allows clarified water to be evacuated from the secondary clarifier 44.

[0115] The first outlet 56 of the secondary clarifier 44 is connected to the sludge treatment system 25 by a discharge circuit 58.

[0116] Furthermore, the second outlet 56 of the secondary clarifier 44 is also connected to the inlet of the secondary treatment system 22 by a sludge recirculation circuit 59. The flow rate of the sludge circulating in the circuits 58 and 59 is regulated by a valve or a pump 60. The operation of this valve or pump 60 is, for example, controlled by the control system 28 according to business rules.

[0117] The sludge treatment system 25 allows the sludge from the primary treatment system 21 and the secondary treatment system 22 to be treated.

[0118] In particular, as explained previously, the sludge treatment system 25 allows the recovery of primary sludge from the primary clarifier 31 and biological sludge from the secondary clarifier 44.

[0119] The treatment of these sludges is carried out for example by a suitable treatment device known in itself.

[0120] The control system 28 allows the operation of the treatment plant 10 to be controlled, for example, by controlling the operation of all the valves and / or pumps of this plant. This control is known in itself and will not be described in detail hereafter.

[0121] The control system 28 also allows the carbon content in the secondary treatment system 22 to be controlled.

[0122] To do this, the control system 28 includes a first processing module 81 connected to the measuring module 32 and a second processing module 82 connected to the first processing module 81 and to means for controlling the carbon content which will be described in more detail later.

[0123] In particular, the first processing module 81 allows the first-type parameters measured by the measurement module 32 to be processed in order to determine at least one second-type parameter characterizing the organic matter content of the treated waters. Advantageously, the second type parameter(s) also characterize the concentration of ammonia nitrogen and phosphorus.

[0124] In particular, the parameter or each parameter of the second type is chosen from the group comprising the following elements characterizing the organic matter content of the treated water: - the concentration of suspended solids (ie total suspended solids, or TSS from the English Total Suspended Solids); - the biochemical oxygen demand BOD (or Biological Oxygen Demand); - Chemical Oxygen Demand (COD).

[0125] In some examples, the processing module 81 makes it possible to determine in addition at least some variations of these parameters, such as for example the parameter BOD5 corresponding to the biochemical oxygen demand BOD at 5 days, the concentration of ammonia nitrogen (N-NH4+ and phosphorus (P-PO4)

[0126] To determine for at least one of the second type parameters and possibly their variations, the first processing module 81 is capable of implementing a mathematical model which then links the or each first type parameter to this second type parameter.

[0127] Advantageously, the mathematical model is determined by a machine learning technique and / or by a statistical technique and / or by a mechanistic technique.

[0128] To determine this mathematical model, for example by a machine learning technique, it is possible, for example, to use a first database containing measurements of first-type parameters and a second database containing measurements of second-type parameters.

[0129] A learning phase can thus be implemented using the two databases. This can, for example, be implemented prior to the operation of the processing installation 10.

[0130] The mathematical model determined by a statistical technique can also be determined using two databases as defined above and statistical methods to link these two databases together.

[0131] Finally, the mathematical model determined by a mechanistic technique can, for example, be determined using business formulas known in themselves which relate at least some of the second type parameters to at least some of the first type parameters.

[0132] In all cases, the mathematical model can be parameterized by configuration parameters relating to the processing installation 10.

[0133] These configuration parameters may, for example, correspond to the dimensions of this installation as well as its particular structure.

[0134] In some embodiments, the mathematical model is expressly determined for the processing plant 10.

[0135] For example, this mathematical model can be determined using data relating to the operation of this installation before automatic control of the carbon content in the secondary treatment system 22 is implemented.

[0136] Of course, any other technique enabling the determination and optimization of the mathematical model may be used.

[0137] Furthermore, it is possible to evolve this mathematical model during the operation of the processing installation 10 by using, for example, machine learning techniques.

[0138] The second processing module 82 allows the operation of the carbon content control means to be controlled according to the parameter or each parameter of the second type determined by the first processing module 81. For this purpose, a mathematical model associating for example the parameter or each parameter of the second type determined by the first processing module 81 with the carbon requirements of the secondary processing system 22 can then be determined.

[0139] As in the case of the first processing module 81, such a mathematical model can also be determined using a machine learning technique and / or a statistical technique and / or a mechanistic technique.

[0140] In addition, this mathematical model is also determined according to the nature of the means of controlling the carbon content as they will be described later.

[0141] Each of the processing modules 81, 82, for example, includes at least part of a software component that is implemented by a computer comprising, for example, a processor and memory for this purpose. Alternatively or in addition, at least one of these modules 81, 82 is implemented at least part of a programmable logic circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit).

[0142] According to the first embodiment illustrated in [Fig. 1], the means for controlling the carbon content include a redirection circuit 90 extending between the first outlet 36 of the primary clarifier 31 and the inlet of the secondary treatment system 22. This redirection circuit then allows primary sludge discharged by the primary clarifier 31 to be redirected to the secondary treatment system 22.

[0143] The means for controlling the carbon content further include a first flow regulator 92 allowing the flow of the primary sludge in the redirection circuit 90 to be regulated in relation to the discharge circuit 38 of the primary sludge.

[0144] The first flow regulator 92 has, for example, a valve and / or a pump that can be configured to redirect part of the primary sludge from the first outlet 36 of the primary clarifier 31 or the total flow of this primary sludge within a predetermined time interval.

[0145] The operation of the first flow regulator 92 is controlled by the second processing module 82.

[0146] According to the second embodiment illustrated in [Fig.2], the means for controlling the carbon content include a supply circuit 190, a second flow regulator 194 and a third flow regulator 196.

[0147] In particular, the supply circuit 190 connects an external carbon source 192 to the secondary processing system 22 and in particular, to the denitrification device 42.

[0148] The carbon source 192 includes, for example, methanol or any other product containing chemical or organic carbon that can be used in the denitrification process.

[0149] The second flow regulator 194 allows control of the flow of the product from the external source 192 into the supply circuit 190.

[0150] The third flow regulator 196 controls the flow rate in the internal recirculation circuit 46, allowing the nitrate-containing water to be reinjected into the denitrification unit 42. In some examples, the function of the third flow regulator 196 can be performed by the recirculation valve or pump 47, as described previously. In some embodiments, the carbon content control means do not include a third flow regulator 196.

[0151] Each of the second and third flow regulators 194, 196 has, for example, a valve and / or a pump disposed in the corresponding circuit.

[0152] The operation of these two regulators 194 and 196 is controlled by the second processing module 82 to control the carbon content in the secondary processing system 22.

[0153] According to the third embodiment illustrated in [Fig.3], the means for controlling the carbon content include the elements described in relation to the first two embodiments, i.e. the redirection circuit 90, the first flow regulator 92, the supply circuit 190, the second flow regulator 194 and the third flow regulator 196.

[0154] According to this third embodiment, the means for controlling the carbon content further include an injection circuit 290 for injecting chemical reagents from an external source 292 into the primary clarifier 31.

[0155] The control means further include a fourth flow regulator 298 allowing the flow of chemical reagents in this injection circuit 290 to be regulated.

[0156] The operation of this fourth regulator 298 is also controlled by the second processing module 82.

[0157] The process of controlling the treatment plant 10 will henceforth be described with reference to [Fig.4] representing a flowchart of its steps.

[0158] Advantageously, these steps are implemented regularly with a predetermined repetition frequency. This repetition frequency is, for example, less than one hour, advantageously less than ten minutes, and preferably less than five minutes.

[0159] During a first step 110, the measuring module 32 measures in the primary treatment system 21 at least one first-type parameter characterizing the water treated by this primary treatment system 21.

[0160] In some cases, different first-type parameters can be measured at different recurrences of this first step 110. Thus, at least some first-type parameters can be measured with different frequencies.

[0161] Then, in a second step 120, the first processing module 81 determines at least one second type parameter from the or each first type parameter measured by the measurement module 32.

[0162] In some cases, the second type parameter determined in this step 120 depends on the available first type parameter(s). Thus, at least some second type parameters can be determined with different frequencies depending on the frequency of determination of the corresponding first type parameters.

[0163] As previously stated, the second type parameter or each parameter characterizes the organic matter content of the treated water.

[0164] During a third step 130, the control means driven by the second processing module 82 control the carbon content in the secondary processing system 22 as a function of the or each second type parameter determined during the previous step 120.

[0165] In particular, the implementation of this step 130 depends on the nature of the control means used to control the carbon content in the secondary treatment system 22. Thus, when the control means are implemented according to the first embodiment, during this step, the second treatment module 82 controls the operation of the first flow regulator 92 in the redistribution circuit 90.

[0166] When the control means are implemented according to the second embodiment, the second processing module 82 controls the operation of the second flow regulator 194 to regulate the flow in the supply circuit 190 and / or the third flow regulator 196 to control the flow in the internal recirculation circuit 46.

[0167] When the control means are implemented according to the third embodiment, the second processing module 82 controls the first flow regulator 92, the second flow regulator 194, and the third flow regulator 196 as explained previously. The second processing module 82 further controls the fourth flow regulator 298 to further regulate the flow rate of the chemical reagents in the primary clarifier 31.

Claims

Demands

1. A method for piloting a wastewater treatment plant (10) comprising a primary treatment system (21) and a secondary treatment system (22), the primary treatment system (21) comprising a primary clarifier (31) configured to separate primary sludge from the treated water, the secondary treatment system (22) comprising a nitrification device (43) and a denitrification device (42) of the treated water; the method comprising the following steps: - measuring (110) in the primary treatment system (21) at least one first-type parameter characterizing the treated water; - determining (120) at least one second-type parameter from the measured first-type parameter(s), the second-type parameter(s) characterizing the organic matter content of the treated water;- control (130) of the carbon content in the secondary treatment system (22) as a function of the second type parameter(s).

2. A method according to claim 1, wherein the determination step (120) of the parameter or each parameter of the second type is carried out with a repetition frequency of less than 1 hour, advantageously less than 10 min and preferably less than 5 min.

3. A method according to claim 1 or 2, wherein the carbon content control step (130) is carried out with substantially the same repetition frequency as the determination step (120) of the second type parameter(s).

4. A method according to any one of the preceding claims, wherein the parameter or each of the first type is chosen from the group comprising the following elements characterizing treated waters: - pH; - oxygen content; - oxidation-reduction potential (ORP); - turbidity; - electrical conductivity; - temperature; - flow rate.

5. A method according to any one of the preceding claims, wherein the parameter or each parameter of the second type is chosen from the group comprising the following elements characterizing the organic matter content of the treated water: - concentration of suspended matter; - biochemical oxygen demand (BOD); - chemical oxygen demand (COD).

6. A method according to any one of the preceding claims, wherein the measurement of at least one first-type parameter is carried out upstream and / or downstream of the primary clarifier (31).

7. A method according to any one of the preceding claims, wherein the determination of the parameter or each parameter of the second type is carried out using a mathematical model, preferably the mathematical model being determined by a machine learning technique and / or by a statistical technique and / or by a mechanistic technique.

8. A method according to any one of the preceding claims, wherein the control of the carbon content in the secondary treatment system (22) is achieved by controlling a redirection of the primary sludge in the secondary treatment system (22).

9. A method according to any one of the preceding claims, wherein the control of the carbon content in the secondary treatment system (22) is carried out by controlling the addition of carbon from an external source (192) into the secondary treatment system (22), preferably into the denitrification device (42).

10. A method according to any one of the preceding claims, wherein the control of the carbon content in the secondary treatment system (22) is carried out by controlling an internal recirculation between the denitrification device (42) and the nitrification device (43).

11. A method according to any one of the preceding claims, wherein the control of the carbon content in the secondary treatment system (22) is carried out by the control of chemical reagents in the primary clarifier (31).

12. Wastewater treatment plant (10) comprising a primary treatment system (21) and a secondary treatment system (22), the primary treatment system (21) comprising a primary clarifier (31) configured to separate primary sludge from the treated water, the secondary treatment system (22) comprising a nitrification device (43) and a denitrification device (42) for the treated water; the treatment plant (10) further comprising: - a measurement module (32) in the primary treatment system (21) for at least one first-type parameter characterizing the treated water; - a first treatment module (81) configured to determine at least one second-type parameter from the measured first-type parameter(s), the second-type parameter(s) characterizing the organic matter content of the treated water;- means of controlling the carbon content in the secondary treatment system (22) as a function of the second type parameter(s).

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