WO2003086986A1

WO2003086986A1 - Odour control of wastewater canal system

Info

Publication number: WO2003086986A1
Application number: PCT/HU2003/000016
Authority: WO
Inventors: Andrea JOBBÁGY; Gyula István VARGA; József SIMON; Rudolf ÁNGYÁN; József MÁJER; Béla MOLNÁR; Imre PÁLFI; István RÜCK
Original assignee: Dunántúli Regionális Vizmürt
Priority date: 2002-04-15
Filing date: 2003-02-28
Publication date: 2003-10-23
Also published as: HU225598B1; HU0201227D0; HUP0201227A2; HUP0201227A3; AU2003209513A1; EP1527021A1

Abstract

The subject of the invention is an arrangement to regulate the nitrate-dosage odour control of wastewater canal system, which comprises at least one measuring unit (2) and one nitrate dosing unit (3), and in given cases other auxiliary equipment(s), installed on a wastewater collecting canal system, divided into canal sections (5) by lifting stations (1) and joining to a wastewater treatment plant or wastewater receiving unit, wherein the measuring unit(s), nitrate dosing unit(s) (3) and additional equipment are connected to a control centre (4) by data transferring connection and control signal lines. The arrangement according to the invention is characterised by, that the measuring unit(s) /2/ are controllable measuring instrument(s), preferably automatic electrochemical instrument(s) providing the measurement results in the form of electric output signals to the control centre /4/, and it is (they are) capable of measuring at least hydrogen sulphide quantity; furthermore the nitrate dosing unit(s) /3/ contain a chemical storage tank /31/ equipped with a dosing means /32/ controlled from the control centre /4/; and finally the control centre /4/ consists of data processing- /41 /, arithmetical- /43/, memory- /45/ and operative units /44/, where the data processing unit /41/ is developed is capable of analysing the data according to measuring units /2/ and seasons, the arithmetical unit /43/ is developed is capable of determining the standard nitratequantity to be dosed based on the measurement data, while the memory unit /45/ is capable of storing the actual and archived data and the events, and the operative unit /44/ is capable of coordinating the control processes.

Description

Odour control of wastewater canal system.

The subject of the invention is an arrangement to regulate the nitrate-dosage odour control of wastewater canal system, which comprises at least one measuring unit and one nitrate dosing unit, and in given cases other auxiliary equipment(s), installed on a wastewater collecting canal system, divided into canal sections by lifting stations and joining to a wastewater treatment plant or wastewater receiving unit, wherein the measuring unit(s), nitrate dosing unit(s) and additional equipment are connected to a control centre by data transferring connection and control signal lines.

One of the great problems of wastewater collecting canal systems is, that from time to time, odour generating processes are started in the wastewater. In order to eleminate this problem, it has been well known practice for many years, to multiply nitrate- decomposing bacteria in the wastewater by dosing nitrate-salts, which survive better, and therefore by means of the so-called competitive inhibit function, repress the growth of the odour generating microflora. The problem of nitrate addition is that the nitrate decomposing bacteria proliferate more quickly when the concentration of nitrate is higher and the greater bacteria population consume quicker the added nitrate. The overdosing of nitrate is detrimental on wastewater cleaning procedures, and causes harmful environment pollution. This difficulty is by-passed by the Hungarian Patent reg. 212371 by setting up an optimum nitrate dosage, which sufficiently represses the growth of the odour generating bacteria, but also limits the number of nitro bacteria and keeps it at an advantegous level, "limited nitrate dosing". The patented solution determines the optimum nitrate quantity, as the nitrate-concentration belonging to 50% multiplication speed, where 100%_^ multiplication speed is the maximum multiplication speed value, that is the saturation value". The latter can be determined from the set of measurements taken on the wastewater to be treated, values, The multiplication speed values are determined by experiments on the basis of a series of samples with increasing nitrate- concentration, and out of these the speed value belonging to half of the maximum denitrifying-bacterium multiplication speed at which excess nitrate is produced, is selected. From empirical function the sought nitrate-concentration value ("half saturation nitrate value") belonging to the above-mentioned half speed can be estimated. The solution actually overcomes earlier difficulties, and can be realised in workshop environment.. In spite of this, it is not sufficiently marketable. When useing the patent procedure, is not enough to install the suitable nitrate dosage unit or units on the wastewater collecting and draining canal system, in short: on the canal system, and hand over the application know-how. The handing over personnel should run in the workshop, and the users should learn specific professional knowledge for the efficient operation. Another problem is, that the "half-saturation" nitrate value is wastewater specific. The relationship and the optimum nitrate dosage for the wastewater of different nature or type shall be determined by new experiments. The patented solution also extends to the control of the process by measuring the generated H₂S gas, but for the more complex canal system including several lifting stations, fast rewiev of the H₂S meassurement results, and their consequences, as well as fast determination of the correct intervention is elaborate.

The aim of this invention is to build-out the technological arrangement, which allows the automation of the technological procedure as much as possible, providing monitoring of the process and, when necessary human intervention.

It is also the aim of this invention to provide, that this automation could be realised with minimum investment cost, when possible only with minimum conversion of the existing objects of the canal system.

A further aim of this invention is, that all the professional experience and data, which was accumulated since the deodorization process using half-saturation nitrate- concentration was introduced, could be also possible to utilize by less experienced users in this field.

The base of the invention is the recognition, that charcteristics of the limited nitrate dosage deodorization process allow building up such a learning and self-developing subsystem, which can adjust the automatic system to the modified to the wastewater characteristics in case of minor changes of the wastewater type occurring in practical life, without the need to repeatedly determine the reationship between nitrate- concentration and bacterium multiplication speed by experiment.

During the practical application of the technology for several years, we came to the surprising recognition, that general experience in nitrate-dosage can also be sufficiently used for the new wastewater system, since when using the determined initial dosage parameters, during start-up the system will step by step set in to the new parameters according to the characteristics of the system, if the data describing the system state are regularly fed back into the regulating mechanism controlling the system. j

Another recognition founding the invention is, that taking into account the characteristics of the fermentation and chemical processes taking place in the wastewater, the set targets can be sufficiently achieved, if, instead of the basic measurement data of the parameters used for evaluations in the process control, and for the decisions based on these, we work with discrete values determined according to conventions, marking partial ranges (value intervals) covered by the basic data. This allows the utilization of modern mathematical and automation methods to achieve the set target.

Based on the above recognitions, the current invention solution to achieve our targets is an arrangement to regulate the nitrate-dosage odour control of wastewater canal system, which comprises at least one measuring unit and one nitrate dosing unit, and in given cases other auxiliary equipment(s), installed on a wastewater collecting canal system, divided into canal sections by lifting stations and joining to a wastewater treatment plant or wastewater receiving unit, wherein the measuring unit(s), nitrate dosing unit(s) and additional equipment are connected to a control centre by data transferring connection and control signal lines.

This arrangement can be characterised by, that the the measuring unit(s) are controllable measuring instrument(s), preferably automatic electrochemical instrument(s) providing the measurement results in the form of electric output signals to the control centre, and it is (they are) capable of measuring at least hydrogen sulphide quantity; furthermore the nitrate dosing unit(s) contain a chemical storage tank equipped with a dosing means controlled from the control centre; and finally the control centre consists of data processing-, arithmetical-, memory-, and operative units, where the data processing unit is developed is capable of analysing the data according to measuring units and seasons, the arithmetical unit is developed is capable of determining the standard nitrate-quantity to be dosed based on the measurement data, while the memory unit is capable of storing the actual and archived data and the events, and the operative unit is capable of coordinating the control processes.

The invented arrangement can be advantageously characterised by that, each of the lifting stations contains one or more pumps, which can be started or shut down by the internal automatic system of the station.

The invented arrangement can also be advantageously characterised by that, the measuring units are capable of measuring the hydrogen sulphide concentration appearing in the air-space near the surface of the wastewater. The invented arrangement can be even advantageously characterised by that, the data processing unit is capable to differentiat the incoming measured data according to the data type and the measuring units, and to store them in data groups 2-10, preferably 4-6, formed according to defined seasons, and within these working days and holidays as well. In addition, the invented arrangement can also be advantageously characterised by that, the arithmetical unit is capable of determining the average, dispersion, most probable value of the formed data group; and, as the function of these to calculate the actual nitrate dosage. In addition, the invented arrangement can be advantageously characterised by that, the memory unit is divided to the lifting station memory storing the parameters of the lifting stations, an event memory storing the nature and data of events, the nitrate dosage memory storing the relevant nitrate dosages according to the formed data groups, as well as the state-memory storing the states of the lifting stations and the nitrate dosing units. Furtherly, the invented arrangement can be advantageously characterised by, that the arithmetic unit is built in such way, that the relevant nitrate dosage values stored in the nitrate dosage memory can be updated by new nitrate dosage values, preferably annually and by time proportional weighing or overwriting. An advantageous embodyment of the invented arrangement can be characherised by that, it is equipped with user displays to continuously inform the users, and the operational unit is built so, that the data in the state-memory can be displayed on the user displays.

Another further advantageous embodyment of the invented arrangement can be characherised by that, it is equipped with nitrate-concentration meter measuring the nitrate-concentration of the wastewater to be treated at one or more locations. An even further advantageous execution of the invented arrangement can be characherised by that, it is equipped with additional control and feedback equipment, like the liquid level meter, located in the lifting station and/or the thermometer, and in certain cases the level meter indicating the nitrate solution quantity in the tank.

We will demonstrate the invention in detail, through execution examples, using the enclosed Figures, but not limiting neither the applicability of the invention nor the demanded protection to the examples shown here. Figures

Figure 1. Simplified draft of an arrangement, according to the invention.

Figure 2. The useful structural block diagram of the lifting station according to the invention.

Figure 3. Simplified organisation chart of the measuring unit according to the invention.

Figure 4. Schematic diagram of the nitrate dosing unit according to the invention

Figure 5. Simplified drawing of the control and information-flow connections of the arrangement.

The canal system consists of gravitation and/or pumped canal sections 5 leading to the wastewater treatment plant 6, separated from each their by the lifting station 1. The wastewater collecting network is designed and sized based on the wastewater quantities calculated from the water consumption and the production data of the industrial and private users connected to it. Each of the lifting station 1 is a wastewater collecting shaft, in which one or more pump 12 are located. The lifting station 1 pumps 12 shall be established in the network at such locations, where the level difference is not sufficient for the transport of wastewater by the gravitation, or the speed would be too low due to the risk of sedimentation (1. Figure). Since the production of wastewater is not continuous and it does not arrive to the individual canal sections 5 of the wastewater collecting network and to the lifting station 1 continuously, the lifting station 1 do not have to be operated continuously, only according to the quantity of wastewater to be transported, based on their lifting capacity. The shaft of the lifting station lis expediently equipped with the liquid level meter 13 which starts one or more pump 12 at a preliminary determined liquid level. The pump 12 of the lifting station lare equipped by separate start switches 15 each, which starts or shuts down the pump 12 on the effect of the received start or stop signal (2. Figure). In our example the level signal transmitter 14 of the liquid level meter 13 starts, and later stops the pumps 12. The operation indicator 16 connected to the start switch 15 sends the signal to the control centre 4, which records the operation time of the pump 12 of each of the lifting station 1. Based on other consideration, such an arrangement can also be formed, in which the output signal of the liquid level meter 13 is received in the control centre 4, and the pump 12 are started and shut down from here. In order to prevent multiplication of the microorganisms causing the canal odour, nitrate dosing units 3 are installed at determined locations of the canal system, advantegeously into the shaft of the lifting station 1 or for the canal section 5 taking into account the direction of the flow, in the part after the lifting station 1 The essential part of the nitrate dosing unit 3 is the tank 31 to contain the nitrate-solution to be dosed, and the dosing means 32 equipped with dosage-adjusting device 33. The dosage- adjusting device 33 is an automatic unit, which feeds the determined nitrate-solution quantity at determined time intervals from the tank 31 to the canal system. The dosage- adjusting device 33 is equipped with the signal receiver 34, which receives the control signals coming from control centre 4. With these control signals the dosing time intervals and nitrate-solution quantity per dosage values programmed in the dosage-adjusting device 33 can be changed. In our current example the dosing means 32 is a solution- spraying mechanism, which ejects the determined solution-quantity at determined intervals. The solution-quantity ejected at one time is determined by the duration of the ejection. The dosage-adjusting device 33 in this case controls the frequency of ejecting, and the duration of the single ejection. Of course, any other individually known dosing method may be applied. The nitrate dosing unit 3 can be advantageously equipped with a level meter 35 checking the level of the nitrate-solution in the tank 31 and a level data transmitter 36 transferring the measured value to the control centre 4 (4. Figure). In case of the decrease of the nitrate-solution, the signal of the level data transmitter 36 warns to refill the solution. The nitrate-dosage is appropriate first of all, when the generation of the odour is prevented. The typical indicator is the generation of hydrogen sulphide gas, therefore the most efficient way of checking is measuring the hydrogen sulphide gas. At suitable locations of the canal system, expediently in the shaft of the lifting stations 1, or in the last third of the individual canal sections 5, according to the flow direction, measuring units 2 are located. The measuring unit 2 is located near to the surface of the wastewater, but always in such the way, that the wastewater cannot directly contact and contaminate it. The. parts of the unit are the sampler 21, the sensor 22 and the digitiser 23 (3. Figure). The latter converts the analog signal acquired by physical or physico- chemical measuring method and transfers to the control centre 4 by means of the signal transmitter 24. Measuring the hydrogen sulphide can be executed by any individually known automatic instrument, based on a suitable measuring method. In our example, we indicated the 3 nitrate dosage unit and measuring unit 2 at nearly each canal section 5. In the practice it is not necessary to dose and check in each canal section 5. It can be always decided after checking the actual conditions, how frequently the said units shall be installed. In order to avoid nitrate overdosing, it may be necessary to measure the nitrogen concentration in wastewater at certain points of the canal system, but at least in the last canal section 5, before joining the 6 wastewater treatment plant. In our example an nitrate concentration meter 62 is measuring the nitrate-compounds before the wastewater treatment plant 6. The control centre 4 comprises a data processing unit 41, and a arithmetical unit 43. These units are based on the memory unit 45 also being part of the control centre 4, and the operative unit 44 coordinates the connections between the units and the parts installed on the canal system. The query station 444 of the operative unit 44 can address any lifting station 1, measuring unit 2 or nitrate dosing unit 3 of the canal system, and can call the status and measurement data, including the operation indicator 16, signal transmitter 24, the level data transmitter 36 as well as the state indicator 37. After the coordination unit 445 activated the data processing unit 41, the measurement data are transferred to the data processing unit 41. The control system operates the intervention feedback devices, namely the lifting station 1 and the nitrate dosing units 3, through the lifting station controler 442 and the dosing controler 441. If the lifting stations 1 work in autonome mode accroding to the applied arrangement, then the lifting station controler 442 is not needed. The automatic system informs the human personnel working in the system through the display controler 443 and the user displays 7, monitors the status of the system, the errors occurred and the necessary tasks. The memory unit 45 is divided to several separate memory sections. In addition to the constant data characteristic of the actual canal system and its canal sections 5, the professional experience gained through many years, recorded in managable data format, providing regular refreshing with new experience, shall also be stored, with fast access ensured. In addition, for the purpose of eventual future reconstruction, the errors and events occuring during operation shall also be logged and archived. For the continuous operation, knowing the last setting and the status of the equipment, as well as temporary storage of fast changing data used for the current jobs are necessary. Consequently, the components of the 45 memory are the lifting station memory 451, with the separate capacity data of each lifting station 1 (the pumps 12 built-in) and the canal section 5 length data; the nitrate dosage memory 454, with the nitrate dosage units to be fed valid for various combinations of conditions, as initial data; the event memory 452 as electronic log; and the state-memory 453 with the operation or standby status data of the pump 12 and the parameter setting data of the nitrate dosing units 3. The data processing unit 41 is a unit working essentially under the control of the operative unit 44, which, checking the received input data, divides them into the relevant groups. The data processing unit 41 adresses and manages the parts of the 45 memory, and loads the pertaining data into the appropriate locations. The arithmetical unit 43, also under the control of the operative unit 44, executes the necessary mathematical operations with the input data. It calls the necessary data from the 45 memory, determines the frequency distribution and the most frequent value for each data group, the dispersion value, and also handles the evaluating arithmetical apparatus necessary for decisions. In our example this is advantageously the individually known "FUZZY LOGIC" method [The fuzzy logic method can be known from many web pages, like e.g. the www.fuzzylogical.com ; the http://ask.yahoo.corn/ask/20011101.html; "An Introduction to Fuzzy Logic": www.generation5.org/fuzzyintro.shtml, etc.] After the arithmetical operations the data processing unit 41 stores the results into the appropriate locations of the 45 memory (5. Figure).

In the invented arrangement the control is done as shown below, at the same time describing the operation of the individual structural part. At the beginning of the operation, the nitrate concentration values according to the half-saturation, which should be continously provided for each category to prevent forming of odour generating microflora, as a summary of the experience gained in earlier technologic applications for seasonal categories, within these for working days and holidays, are recorded in the 454 nitrate-dosage memory in data format. To maintain the nitrate-concentration, a different nitrate-quantity is necessary according to the quantity (volume-flow) of incoming wastewater. Dividing the year e.g. to six seasons based on practical experience, we assign one nitrate-quantity value to be dosed to each cubic meter of wastewater. The beginning and closing date of the seasons is also stored in the 45 memory. The internal clock of the control centre 4 also records the calendar days, and detects when the season boundary is exceeded. Based on this, the actual value of nitrate-quantity to be dosed is changed, and the pointer will always point to the nitrate-quantity belonging to the actual season. At the beginning of the operation, the tank 31s are filled up with the same solution, with known nitrate-content.(6. Figure). The spraying pulse frequency and the duration of the individual nitrate-spraying pulses of the dosing means 32 is set by the dosage controler 441, using the dosage-adjusting device 33, in such a way that the nitrate-quantity dosed in a unit time, taking into account the wastewater quantity transported by the lifting stations, should maintain the half-saturation nitrate-concentration in the wastewater, prescribed in the nitrate dosage memory 454. It can be easily understood, that by feeding a volume calculated from a known nitrate-solution concentration, into a known volume wastewater, we set a targeted wastewater-nitrate concentration, in this case the half-saturation nitrate- concentration. The quantity of wastewater is known from the product of the operation time and the capacity of the pumps 12, the quantity of added nitrate-solution, knowing the solution quantity discharged from the dosing means 32 in operation in a unit time sec, is defined by setting the duration of discharge pulse length and the discharge frequency pulse number. Based on practical experience, suitable results are achieved during operation, if the nitrate dosing units 3, operate continuously with an appropriately set pulse length and pulse number, and when odour generation occurs, or to the opposite, nitrate overdosing is detected, the control centre 4 changes the nitrate dosing parameters pulse length, pulse number in the dosage-adjusting device 33, using the the dosage controler 441. In case of another expedient arrangement, where the lifting station 1 are under direct control of the the 4 control centre, the dosing of nitrate can be adjusted to the quantity of the actual transferred wastewater. Starting the lifting station linvolves setting of the nitrate-content of the transferred wastewater, i.e. starting the nitrate dosing unit 3 in the canal section 5 belonging to the lifting station 1. As soon as the query station 444 interrogates one by one the liquid level values through the level signal transmitters 14 from the liquid level meter 13 of each lifting station 1 from these values the wastewater quantity to be lifted can be determined. The incoming speed of , the wastewater can be determined from this and from the time elapsed since the lifting, and it can be decided, whether for the given lifting station lone or more pumps should be started. The 45 lifting station lmemory contains the capacity of each lifting station lin liter/minutes, based on which the arithmetical unit 43 defines to the operative unit 44, the lifting station 1, which should receive a start signal on the start signal receiving pins of their start switches 15 from the lifting station controler 442, and the how long after the start signal the stop signal should be sent. In those lifting station 1, where several pump 12 are in operation, the above refer to the pumps 12. In this arrangement, not only the wastewater quantity, but also the incoming and transport speed are known. Therefore based on the known data not only the nitrate-solution quantity necessary to the wastewater quantity is determined, but also the time of dosing it. This is made possible by the fact, that although the nitrate-solution concentration is already given, nevertheless the dosing pulse length and pulse number can be controlled in the dosage- adjusting device 33 either independent of each other, or together. In the latter arrangement, the lifting station controler 442 is needed, and the dosing controler 441 will set the nitrate dosing parameters for each wastewater quantity. Whenever the lifting station controler 442 and the dosing controler 441 start a lifting station lor a nitrate dosing unit 3, its status signal in the state-memory 453 is changed. This way the state- memory 453 exactly records, that from those belonging to the lifting station lused in the arrangement, which pump 12 and nitrate dosing unit 3 is currently in operation, and which one is shut down. In the state-memory 453 the operating of the pump 12 should also be recorded when the lifting stations 1 run in autonomous mode, and there is no lifting station controler 442 in the arrangement. In this case, the state-memory 453 will contain the actual dosage setting parameters instead of the operating status of the nitrate dosing units 3. The necessary nitrate quantity will be determined according to the contexture outlined above. The operative unit 44 calls the nitrate-dosage data according to the season, belonging to unit wastewater volume [m³] from the nitrate dosage memory 454. The wastewater volume-flow is known from the data of the operation indicator 16 of the lifting station 1 or from the quantity transported under the control of the control centre 4. This defines the total nitrate-quantity to be dosed. From the concentration of the nitrate-solution prepared in the tank 31 of the nitrate dosing unit 3, the chemical volume to be dosed can be calculated, and from the dosing speed of the dosing means 32 we obtain the necessary operation time of the dosage-adjusting device 33. All these tasks are executed by the arithmetical unit 43 under the coordination of the operative unit 44, based on the appropriate parts of the 45 memory. The data necessary for the control are sent to the dosing controler 441, from where in case of one expedient arrangement the control data will pass to the dosage-adjusting device 33, or in another arrangement, in case of direct control, the start and then stop commands are sent to the signal receiver 34. In real life, the decrease of the mtrate-content cannot be exactly predicted.. This is the essential experience, which justifies the introduction of an automatic control system instead of manual control. In fact the nitrate-dosage, the operation of the nitrate dosing units 3 cannot be connected sheerly to the operation of the lifting station 1.It is not normally necessary, that the wastewater flowing from one canal section 5 to another canal section 5 should be filled up with nitrate again, because it may have detrimental effects, and may lead to nitrate overdosing and can overturn the balance of the biologic system in the wastewater to be treated. The cause of this behaviour is, that different types and quantities of wastewater may arrive to the different canal sections 5 of the canal system at different times. The effect of the hard to follow wastewater entries can be followed through the measuring units 2 installed into the arrangement. The hydrogen sulphide measurement data are used in two ways. On one hand, the correct setting of the nitrate dosing is checked by evaluation at each hour, while on the other hand, the measurement data of the last 24-hour form a reference base for the next 24 hour interval. The query station 444 from time to time interrogates the hydrogen sulphide data measured by the measuring units 2 through the signal transmitters 24. The interrogation is done at each minute. The hydrogen sulphide values measured in a 24 hour interval assign a range of values, which is accepted as 100 %, and interpreted divided into linearly equal ranges. The something like 1400 measurement data give a density function with 1 % resolution, from which the average and the most probable values as well as the dispersion are obtained. The speed of the chemical and biological processes as well as of the flow parameters of the the canal system together give a realistic reaction time, which is necessary, for the effect of an intervention to be detectable. Using the analog measurement data received in the next 24 hours, substituting them into the relevant discrete ranges of the said range of values, the new relevant value is obtained. Based on this, it can be decided if it is below or above the intervention threshold, and if it is above, whether the value of exceeding the range justifies using the basic dosage value according to the season in the nitrate dosage memory 454, or its increased or eventually decreased value. This, as described above justifies, that the operation of the lifting station ldoes not necessarily mean the operation of the nitrate dosing unit 3 in the same canal section 5. This is only justified, when the measuring unit 2 in the same canal section 5 detects hydrogen sulphide generation. The efficiency of the operation of the control centre 4 depends significantly on how frequently the measuring units 2 and the nitrate dosing units 3 are installed throughout the canal system, since the changes, to which the system needs to respond, can be detected more precisely, and nearer to the location they occur., The more precisely the nitrate dosing unit 3 through which the response is effected is selected, the better targeted and more efficient the response can be. The installation and maintainance of the measuring units 2 and the nitrate dosing units 3 are both costy, therefore their unnecessary multiplication makes the system unduly expensive. The event memory 452 records, to which measuring unit 2 the data causing the intervention belonged, and which nitrate dosing unit 3 was selected by the automatic control system, as most appropriate. One of advantages of the invented arrangement among others is, that it shows during the operation of the designed arrangement, which equipment proved useless, at which location is the control inaccurate, and where are points, where new equipment should be fitted. The described equipment, according to demands and possibilities can be completed with temperature meter at one or more locations, with nitrate concentration meter 62 and with flow-rate meter. These devices extend the input information of the control system and may refine the control. A further advantage of the control system built according to the invented arrangement, that by means of its self-learning system, it gradually adapts to the characteristics to a concrete wastewater collecting canal system. The data collected with the query station 444 not only serve the actual decision and intervention, but also the long-term analysis of the characteristics of the wastewater-collecting system, and the development of the balanced control strategy preventing and eliminating of extreme situations. The data processing unit 41 sorts the data to as many data populations, as defined by the control system. Thus the arithmetical unit 43 processes the data separately for each measuring unit 2, within that for the season intervals, as well as for workdays and holidays. The number of the measurements provides statistically sufficient data for statistic processing and to provide relevant results. According to the operational experience gained through the years, it is not necessary to process the data strictly according to the rules of mathematical statistics. The results, obtained using the FUZZY LOGIC method are sufficient for the precise control and for maintaining the optimum nitrate level. According to this, the response steps of the automatic control like e.g. changing the nitrate dosing depend on the combined evaluation of the measured and/or checked parameters (hydrogen sulphide generation, temperature, excess nitrate, ...). The determined response step is bound to a predetermined combination of the said parameters as a necessary condition. The FUZZY LOGIC takes the parameters into account by means of so-called truth functions. Based on decades of experience in nitrate-dosage odour control, the truth function of the hydrogen sulphide generation can be edited, where we define a low, medium and high hydrogen sulphide range of values, and assign a truth contents to them between 0 and 100 %. Those values lower than the predetermined hydrogen sulphide value, are assigned 100% LOW truth content, while those values higher than another predetermined value are assigned 100% HIGH truth contents. In the range between the two predetermined hydrogen sulphide values, the truth contents of LOW decreases from 100% to 0%, while that of the HIGH incresases for 0% to 100%. A different LOW or HIGH truth contents belongs to each point of this section, while the sum of the two values is always 100. By substituting the standard hydrogen sulphide value referring for one hour or 24 hours obtained from the measurements results into the truth function, we receive the truth contents of the HIGH evaluation. Comparing this with the values obtained on the base of the truth functions of other considered factors, the assigned nitrate dosage value can be read from the nitrate dosage memory 454. If the operation of the automatic system based on this is not sufficient, the boundary values of the sections in the truth functions can be changed. The system of changing the conditions and its mechanism can be expediently part of the abobe mentioned self-learning mechanism. The principle of corrections is obviously the real correlation between the measured and the target parameters (hydrogen sulphide generation, nitrate dosing), which is produced from the real-time measured data during operation by the arithmetical unit 43, either continuously or when necessary. According to the above, the arithmetical unit 43 assigns a nitrate dosage to each combination of place and season in such a way, that based on the combinations of values obtained from truth functions it increases or decreases the initial nitrate dosage data obtained from the nitrate dosage memory 454 according to predetermined discrete steps. The initial data stored in the nitrate dosage memory 454 assigned to dosing locations and seasons can be modified every year, depending on the amount of deviation of nitrate dosage values determined by the new data collected through the annual operation. When developing the control system, it has to be decided, whether the new data shall substitute the old ones, or create new initial data according to some proportion of weighing. According to the experience gained so far, it is recommended to eliminate excessive fluctuations, and therefore it is practical to compensate the fluctuations taking into account the data of the preceding five years. This way e.g. the modifying and the old values can form the new initial nitrate dosage data in the proportion of 1: 4. , Summarising the information on the operation, the control has a double operation. The control system evaluates the ad hoc measurement data immediately at each hour, and when necessary it responds with prompt feedback and answer. This way, in the arrangement the control system promptly compensates the local extremities e.g. in he case of unexpected jerky admission of wastewater or anomaly effects extending to the complete network. An automatic following and adaptation is provided by the 24 hours evaluation and correction steps. At the same time, collecting the data for a complete season interval, and analysing the situations based on this, the control system at determined intervals practically annually also makes the normal, regular control more precise, iterating an operation, where the occurence of extremities becomes more and more infrequent.

It is a great advantage of the invention, that it makes possible the installation and introduction of limited nitrate dosage odour suppression, because it provides coordinated handling of the complete wastewater-collecting network. The successful running in does not depend on professional traning of the personnel taking over the technology. The self-learning system working on the iteration principle also logs the data and events, so they can be utilised and used at other installations and applications.

The solution according to the invention can be easily, and successfully installed into the wastewater collecting canal systems.

Claims

C l a i m s

1.) An arrangement to regulate the nitrate-dosage odour control of wastewater canal system, which comprises at least one measuring unit and one nitrate dosing unit, and in given cases other auxiliary equipment(s), installed on a wastewater collecting canal system, divided into canal sections by lifting stations and joining to a wastewater treatment plant or wastewater receiving unit, wherein the measuring unit(s), nitrate dosing unit(s) and additional equipment are connected to a control centre by data transferring connection and control signal lines, characterised by that, the measuring unit(s) 111 are controllable measuring instrument(s), preferably automatic electrochemical instrument(s) providing the measurement results in the form of electric output signals to the control centre 141, and it is (they are) capable of measuring at least hydrogen sulphide quantity; furthermore the nitrate dosing unit(s) 131 contain a chemical storage tank /31/ equipped with a dosing means /32/ controlled from the control centre 141; and finally the control centre 141 consists of data processing- /41/, arithmetical- /43/, memory- /45/ and operative units /44/, where the data processing unit /41/ is developed is capable of analysing the data according to measuring units 121 and seasons, the arithmetical unit /43/ is developed is capable of determining the standard nitrate- quantity to be dosed based on the measurement data, while the memory unit /45/ is capable of storing the actual and archived data and the events, and the operative unit /44/ is capable of coordinating the control processes.

2. ) The arrangement according to claim 1. characterised by, that each lifting station III, contains one or more pump(s) /12/ which can be started or stopped by the internal automatic system of the lifting station III.

3.) The arrangement according to claims 1. or 2. characterised by, that the measuring units 121 are capable of measuring the hydrogen sulphide concentration appearing in the air-space near the surface of the wastewater.

4.) The arrangement according to any of the claims 1.- 3. characterised by, that the data processing unit /41/ is capable to differentiat the incoming measured data according to the data type and the measuring units 121, and to store them in data groups 2-10, preferably 4- 6, formed according to defined seasons, and within these working days and holidays as well.

5.) The arrangement according to any of the claims 1. to 4. characterised by, that the arithmetical unit /43/ is capable of determining the average, dispersion, most probable value of the formed data group; and, as the function of these to calculate the actual nitrate dosage.

6.) The arrangement according to any of the claims 1.- 5. characterised by, that the memory unit /45/ is divided to the lifting station memory /451/ storing the parameters of the lifting stations 111, an event memory /452/ storing the nature and data of events, the nitrate dosage memory /454/ storing the relevant nitrate dosages according to the formed data groups, as well as the state-memory /453/ storing the states of the lifting stations ill and the nitrate dosing units.

7.) The arrangement according to any of the claims 1.- 6. characterised by, that the arithmetic unit /43/ is built in such way, that the relevant nitrate dosage values stored in the nitrate dosage memory /454/ can be updated by new nitrate dosage values, preferably annually and by time proportional weighing or overwriting.

8.) The arrangement according to any of the claims 1.- 7. characterised by, that it is equipped with user displays 111 to continuously inform the users, and the operational unit/44/ is built so, that the data in the state-memory /453/ can be displayed on the user displays 171.

9.) The arrangement according to any of the claims 1.- 8. characterised by, that it is equipped with nitrate-concentration meter /62/ measuring the nitrate-concentration of the wastewater to be treated at one or more locations.

10.) The arrangement according to any of the claims 1.- 9. characterised by, that it is equipped with additional control and feedback equipment, like the liquid level meter

1131, located in the lifting station 111, and or thermometer, and in certain cases the level meter /35/ indicating the nitrate solution quantity in the tank /31/.