Method and device for controlling the supply of ambient air to an aeration tank of a wastewater treatment plant

Description

[0001] A method and a device are described which show a controlled supply of ambient air into an aeration tank of a wastewater treatment plant, with the features of patent claims 1 and 14. background

[0002] Wastewater treatment plants use bacteria and microorganisms, among other things, to biologically purify the wastewater under aerobic conditions. To achieve this, the oxygen present in the wastewater is processed by the bacteria and microorganisms, which are referred to as biology. This process is also referred to as respiration.

[0003] In order to maintain the respiration process, oxygen in the form of ambient air is introduced into the wastewater in the aerobic process step and distributed as well as possible.

[0004] In existing measurement systems, the current state of the art primarily analyzes the exhaust air for oxygen content (O2 content in vol.%) and carbon dioxide content (CO2 content in vol.%). Depending on the application, parameters for controlling the air volume to be introduced are determined based on the current oxygen demand, which, however, strongly depends on the current contaminant load in the wastewater to be treated. State of the art

[0005] It has already been proposed to determine the amount of ambient air to be introduced into the wastewater based on the dissolved oxygen content present in the wastewater and measured as such. However, the ongoing possible changes in the composition and quantity of the wastewater continuously flowing into a wastewater treatment plant have not been adequately taken into account.

[0006] For example, DE 30 19 698 A1 discloses a method for maintaining an optimal oxygen concentration in an aeration tank of a wastewater treatment plant. In accordance with the changing biological oxygen demand in the aeration tank of the biological wastewater treatment plant, the specific oxygen content in the water, in the form of the concentration of dissolved oxygen, is determined in the outlet area from the aeration tank and the full addition rate of the aeration device is initiated at approximately two-thirds of the intended O2 content, i.e. the setpoint. The addition rate is continuously throttled as it approaches the setpoint until a minimum rate is reached that maintains the setpoint. If the setpoint drops below the setpoint, the system is adjusted accordingly to the changed and changing situation.

[0007] DE 31 50 902 A1 discloses another process for the biological treatment of wastewater using a two-stage treatment process with the addition of an oxygen-containing gas. In a first stage, the wastewater is passed through a trickling filter or filter and in a second stage through an aeration tank. To achieve high treatment values, a treatment gas containing a higher volume percent of oxygen than air is fed to the first stage via a feed line. The resulting exhaust gas is passed from the first stage to the second stage via a gas flow path, and the amount of treatment gas fed in is such that the exhaust gas withdrawn via an exhaust line after passing through the two stages still contains 15 to 70 volume percent, preferably 25 to 50 volume percent, of oxygen.

[0008] From DE 199 44 389 A1, it is known to supply a first oxygen-containing aeration gas to the wastewater in an aeration tank in the area of ​​a lower aeration zone for aerating wastewater. In order to specify a method for the effective aeration of wastewater in an aeration tank with a small cross-sectional area and great depth, to provide a flexible and inexpensive aeration device therefor, and to propose an aeration tank that allows a sufficiently high oxygen input into the wastewater to be treated even with a small cross-sectional area and great depth, it is proposed with regard to the method that a second oxygen-containing aeration gas is supplied to the wastewater in an upper aeration zone. The aeration device is characterized by a lower aeration unit and at least one upper aeration unit.In the aeration tank, a lower gassing zone with a lower gassing unit is provided and above it an upper gassing zone with an upper gassing unit.

[0009] EP 0 885 639 A1 discloses a method for regulating the supply of oxygen-containing gas to an ascending-flow biofilter. Supply means for water to be filtered are provided in the lower part of the biofilter. A filter bed (generally consisting of at least one layer of granular filter material whose density is lower or higher than the water density, but which may also be formed from a rigid structured packing) is used, which serves as a support for a biomass active in decomposing the carbon- and / or nitrogen-containing impurities in the water to be filtered. Furthermore, means for distributing an oxygen-containing gas (typically air) are provided in at least part of the filter bed. Furthermore, a reserve area is provided above the filter bed, which allows the formation of a water layer above the filter bed.Finally, there are means for draining the filtered water that has passed upwards through the filter, which are located in the upper part of the filter.

[0010] From WO 2001 / 19738 A1 a method for aerating wastewater in an aeration tank is known in which a first oxygen-containing aeration gas is supplied to the wastewater below the wastewater level in the region of a lower aeration zone, and a second oxygen-containing aeration gas is supplied to the wastewater in an upper aeration zone extending above the lower aeration zone.

[0011] EP 0 732 588 A2 discloses a method for determining carbon degradation and nitrification in biological systems, particularly in biological wastewater treatment systems. The oxygen required to degrade pollutants is introduced into the aeration tank, for example, by aeration. The oxygen consumption rate is determined by measuring the excess oxygen in the form of dissolved oxygen using particle pressure sensors. Depending on this oxygen consumption rate, the biological processes of wastewater treatment are controlled by a defined oxygen supply.

[0012] EP 0 585 702 A1 discloses an arrangement for regulating the bioactivity of biological systems, particularly in biological wastewater treatment systems, in which oxygen is supplied to maintain bioactivity. The oxygen consumption rate is determined by partial pressure sensors based on the amount of excess oxygen in the form of dissolved oxygen. Depending on this oxygen consumption rate, the biological processes of wastewater treatment are controlled by a defined oxygen supply.

[0013] US 2004 / 0112829 A1 and KR 2016 0104249 A describe a further method and device for the continuous automated control of biological wastewater treatment processes.

[0014] TaskCompared to the known designs from the state of the art, the task is to regulate the supply of ambient air into the aeration tank based on the gases escaping from the surface of the aeration tank and at the same time to reduce the supply of ambient air necessary for the pollutant load degradation process to a minimum, whereby considerable energy savings can be achieved in the operation of the wastewater treatment plant.

[0015] In addition, an alternative solution to the methods and devices known from the state of the art is to be provided. Solution

[0016] The above-mentioned object is achieved by the method features of patent claim 1 and the device features of patent claim 14.

[0017] The method according to the invention is used to control the supply of ambient air into an aeration tank of a wastewater treatment plant. The method is characterized by the following process steps:lit a) by means of a collecting device arranged on the aeration tank, the gas escaping from the aeration tank at a predefined point on the surface of the aeration tank, isolated from the ambient air, is collected, and this escaping gas quantity is subjected to an analysis, lit b) as part of the analysis, the oxygen content and the carbon dioxide content in the escaping gas collected on the surface of the aeration tank are determined, lit c) the difference between the sum of the oxygen content and the carbon dioxide content between the supplied ambient air and the sum of the oxygen content and the carbon dioxide content of the gas collected on the surface of the aeration tank is determined, lit d) from the difference between the sum of the oxygen content and the carbon dioxide content according to lit c), generated by the biological degradation of the pollutant load and the gas components not actively involved in the biological degradation of the pollutant load by changing the concentration,the amount of total oxygen consumption from the ambient air supplied and the proportionate carbon dioxide produced in the aeration tank is determined, lit e) the amount of ambient air supplied is reduced in pre-settable steps as long as the proportion between the difference referred to in lit c) and the proportionate carbon dioxide content remains unchanged and lit f) if the proportion between the difference referred to in lit c) and the proportionate carbon dioxide content changes, the amount of ambient air supplied is increased again by at least the amount of air reduced in the previous step.

[0018] In an advantageous embodiment of the invention according to claim 2, it is provided that in method step a) the escaping gas quantity is recorded and a typical partial flow thereof is subjected to analysis.

[0019] In an advantageous embodiment of the invention according to claim 3, it is provided that in process step d) the proportion of the different biological degradation processes involved in the oxygen consumption is determined, so that according to the current proportion in comparison to the proportion to be expected based on experience, the process steps e) and f) are regulated by defined substrate supply and / or oxygen setpoint variation in the detected dissolved oxygen and / or by suitable variation of the ambient air supply of the contaminant load degradation.

[0020] In an advantageous embodiment of the invention according to claim 4, it is provided that the quantity and / or the bubble size of the supplied ambient air is / is used as a variation of the ambient air supply.

[0021] In an advantageous embodiment of the invention according to claim 5, it is provided that the pollution load reduction is controlled in a targeted manner and according to the desired process proportions.

[0022] In an advantageous embodiment of the invention according to claim 6, it is provided that in process step b) further gas components are analyzed which, as interfering components in the desired contaminant load degradation, can disrupt the degradation process due to atypical contaminant load introduction and these interfering components are compensated or chemically deactivated or stripped out by introducing chemical or further bacterial components or a significant excess of ambient air through the associated stripping effect.

[0023] In an advantageous embodiment of the invention according to claim 7, it is provided that volatile hydrocarbons, which are typically contained in solvents as so-called aromatics, are detected as further gas components in the exhaust air.

[0024] In an advantageous embodiment of the invention according to claim 8, it is provided that the introduced ambient air is sucked in from the ambient air by means of a compressor arranged on the site of the wastewater treatment plant and is compressed by means of the compressor and fed to the aeration tank via a control slide or a valve.

[0025] In an advantageous embodiment of the invention according to claim 9, it is provided that the ambient air sucked in is fed to the aeration tank as required via the control slide or the valve on the basis of the measured, analyzed gas quantity escaping.

[0026] In an advantageous embodiment of the invention according to claim 10, it is provided that both the total amount of ambient air supplied into the aeration tank and the amount of oxygen consumption in the aeration tank are approximately recorded.

[0027] In an advantageous embodiment of the invention according to claim 11, it is provided that the differentiation of the process components of carbon degradation and other oxygen-consuming biological pollutant load degradation components without gaseous oxide components emerging from the surface of the aeration tank, isolated from the ambient air, such as nitrates as a result of nitrification, in the aeration tank using the formula Δ = A − a + b where A stands for the O 2 content of the supplied ambient air in vol.% with a negligible proportion of CO 2, namely only about 0.035 vol.%, a for the O 2 content of the exhaust air in vol.% and b for the CO 2 content of the exhaust air in vol.% and the carbon degradation in the aeration tank consumes at least about four-fifths of the amount of oxygen supplied for CO 2 production, and additionally requires oxygen (without adequate exhaust gas production) for its own reproduction, the biomass build-up (or its increase), so that the Δ-reference is calculated using the formula Δ = 0 , 25 * b + Δ NH 4 − Abbau , where: Δ C degradation = 0.25*b and consequently: Δ NH4 degradation = Δ - 0.25*b, results, provided that the carbon degradation biology consumes additional oxygen for its reproduction in the full amount of about 25% of its oxygen consumption for CO2 production and no other biological components with oxygen consumption and without gaseous oxide emissions are involved, such as for the PO 4 3-< formation, and the proportions between these two aforementioned essential process components in the (in this case so-called) aerobic nitrification stage are simplified according to the formula CF = C − Abbau / NH 4 − Abbau = 1,25 * b / Δ − 0,25 * b can be represented.

[0028] In an advantageous embodiment of the invention according to claim 12, it is provided that the numerical value of A is assumed to be twenty-one (instead of 20.98 vol%).

[0029] In an advantageous embodiment of the invention according to claim 13, it is provided that the wastewater treatment plant generally has a wastewater inlet with a varying inflow rate, a separation device downstream of the wastewater inlet for the mechanically retainable coarse contaminants contained in the wastewater, a settling tank downstream of the separation device in which substances that are contained undissolved in the wastewater and have a significantly higher density than water settle to the bottom of the settling tank, and substances that are contained undissolved in the wastewater and have a significantly lower density than water accumulate on the surface of the wastewater in the settling tank, the aeration tank, to which wastewater from the settling tank is fed and which contains activated sludge with aggregated bacteria and other microorganisms that biotically oxidatively degrade wastewater constituents, with water mixed with activated sludge draining from the aeration tank at the same rate as wastewater is fed from the settling tank,wherein, in the area of ​​the bottom of at least part of the aeration tank, ambient air taken from the surroundings of the aeration tank is injected into the tank under pressure at least pro rata or continuously in the form of fine bubbles, a secondary clarifier into which the water mixed with activated sludge flows and in which the activated sludge is separated from the treated wastewater by settling, and an outlet through which the treated wastewater from the secondary clarifier leaves the sewage treatment plant.

[0030] The device according to the invention is intended for use in the method for regulating the supply of ambient air to an aeration tank of a wastewater treatment plant. The device consists of at least one control unit, a collecting device for the gases escaping from the aeration tank, which is arranged at a predefined location on the surface of the aeration tank and collects portions of the gas escaping from the aeration tank, isolated from the ambient air, and feeds the collected gas quantity at least partially to a gas analysis unit. Ambient air is also supplied to the gas analysis unit from a receiving position, and the gas analysis unit determines the difference between the sum of the oxygen content and the carbon dioxide content between the supplied ambient air at the receiving position and the gas collected by the collecting device on the surface of the aeration tank and feeds it to the control unit.whereby the control unit controls the compressor, which sucks in ambient air in the vicinity of the intake position, compresses it and supplies it to the aeration tank via the control slide or the valve, whereby the control unit reduces the amount of ambient air supplied in pre-adjustable steps by means of the compressor, as long as the proportion CF between the proportion of the carbon dioxide content and the oxygen consumed by the carbon degradation biology for reproduction of the gas escaping from the aeration tank, shielded from the environment and captured, here assumed to be a maximum of 1.25*b,and the difference Δ from the sum of the oxygen content and the carbon dioxide content between the supplied ambient air and the sum of the oxygen and carbon dioxide components of the gas collected on the surface of the aeration tank by means of the collecting device, less the oxygen consumption proportion determined for the total oxygen consumption of the biological components causing the carbon dioxide content, see the above proportion, assumed here to be a maximum of 1.25*b, remains unchanged, however, the control unit increases the amount of supplied ambient air by means of the compressor in pre-settable steps if the proportion CF between the difference between the sum of the oxygen content and the carbon dioxide content between the supplied ambient air and the gas collected on the surface of the aeration tank by means of the collecting device changes to the detriment of the nitrification component.

[0031] Further advantages, features and design options emerge from the following description of figures of non-limiting embodiments. Short description of the drawing

[0032] The drawing FIG shows schematically the structure of a wastewater treatment plant with the components essential to the invention.

[0033] We refrain from showing and describing components that are not essential to understanding the technical teaching disclosed herein. In the following, the reference numerals will not be repeated for all elements already introduced and illustrated, provided that the elements themselves and their function have already been described or are known to a person skilled in the art.

[0034] The wastewater treatment plant described below may be configured and constructed in a form other than that described below. The following description of a wastewater treatment plant serves to further understand the explanation of the invention, since it is used in a wastewater treatment plant, preferably in an aeration tank.

[0035] The wastewater treatment plant described below has a wastewater inlet 1. The wastewater collected in the sewer system and transported to the wastewater treatment plant during wastewater disposal, also referred to as dirty water, is fed to the wastewater treatment plant via the wastewater inlet 1. An inlet basin 2 is usually located downstream of the wastewater inlet 1, in which the wastewater fed via the wastewater inlet 1 is initially collected. The wastewater inlet 1 and the inlet basin 2 are collectively referred to as the wastewater inlet or dirty water inlet. They often contain a device for measuring the inlet flow and a pumping station for lifting the wastewater.

[0036] A so-called stormwater overflow 15 is arranged at the inlet basin 2. This stormwater overflow 15 serves to prevent the sewage treatment plant from being flooded with wastewater if an excessive amount of wastewater-stormwater mixture is fed in. Particularly in a so-called combined system, in which both stormwater and wastewater are collected in one sewer and fed together to the sewage treatment plant, the sewer network must generally be relieved by a stormwater relief system, a stormwater overflow, and / or a stormwater overflow basin to prevent the sewage treatment plant from becoming overloaded. This can be done either in the sewer network or at the sewage treatment plant. In the design according to FIG 1 This is done via storm overflow 15.

[0037] Another option for supplying wastewater and rainwater to a treatment plant is a separate system. In this case, the wastewater and rainwater are each fed into the treatment plant via separate sewers. If excess rainwater is fed into the treatment plant, it is drained directly away from the treatment plant via a stormwater overflow 15.

[0038] A separation device 3 is connected downstream of the inlet basin 2. The wastewater from the inlet basin 2 is fed via the separation device 3 to a settling basin 4 in a nearly continuous flow, although this flow can vary depending on the amount of wastewater inflow. In the separation device 3, the wastewater is passed through a screen or sieve. Coarse contaminants such as sanitary products, pieces of wood, stones, leaves, and even dead animals are filtered out in the screen or sieve. These coarse particles would clog the wastewater treatment plant's pumps and impair the biological treatment results. The narrower the passage for the wastewater in the screen or sieve, the fewer coarse particles remain in the wastewater. The coarse particles thus removed from the wastewater are then sent for further suitable disposal.

[0039] The settling tank 4 is often combined with the separation device 3. There are also wastewater treatment plants in which the settling tank 4 is combined with the primary clarifier 5.

[0040] Settling tank 4 removes coarse contaminants from the wastewater that settle on the bottom of the settling tank 4, such as sand, small stones, or glass fragments. These substances would lead to operational disruptions in the plant and cause increased wear or blockages in the pipes within the wastewater treatment plant. In a special design, settling tank 4 is designed as a longitudinal grit trap or as an aerated longitudinal grit trap, in which greases and oils are simultaneously separated on the surface. Another special design is a circular grit trap or a deep grit trap.

[0041] The aeration of the grit trap, which is preferably located at the bottom of settling tank 4, creates a vortex flow. The injected and dissolved air reduces the density of the wastewater. Due to both effects, the heavy, predominantly mineral solids settle at the bottom of the settling tank. In the deep grit trap, the wastewater flows from above into settling tank 4 and, due to its depth, achieves a relatively long residence time, causing the heavier sand to settle at the bottom of the settling tank.

[0042] From settling tank 4, the wastewater is directed into primary clarifier 5. The wastewater flows slowly through primary clarifier 5. Undissolved matter (feces, paper, etc.) therefore settles to the bottom of primary clarifier 5 or floats on the surface of primary clarifier 5. Approximately 35 percent of the organic matter is removed in primary clarifier 5. This creates what is known as primary sludge, which is then fed into the pre-thickener. It is thickened together with the excess sludge from the aerobic activated sludge plant. The sludge settles, and the excess water, known as turbidity, is drained off and returned to the treatment plant for further treatment. The thickened sludge is pumped to a digester, for example, for further anaerobic treatment.In an alternative embodiment, the nitrate-containing organic substances of the wastewater are used by the corresponding anaerobically active biology in the activated sludge (without external oxygen supply) as a reducing agent for nitrogen removal by denitrification to nitrogen (N2) in the anaerobic, sometimes even anoxic part or in the anaerobic / anoxic phase of the biological stage.

[0043] In tank 5, a so-called upstream denitrification process may also take place. In this case, this anaerobic tank section also already counts towards the so-called biological pollutant degradation process stage.

[0044] From the primary clarifier / denitrification tank 5, the wastewater flows into the aeration tank 6.

[0045] In aeration tank 6, the wastewater containing activated sludge is aerated (aerobic process stage). By aerating the wastewater containing activated sludge, the wastewater constituents in the wastewater are biotically degraded in this biological process stage. Aerobic bacteria and other microorganisms degrade carbon compounds, mostly to carbon dioxide and partially to biomass. The nitrogen from the organic compounds, mostly embedded as ammonia (NH 3 ) or ammonium (NH 4 +< ions), is oxidized by other bacteria, first with oxygen to nitrite (NO 2 -< ) and finally to nitrate (NO 3 -< ). Aeration tank 6 is usually operated in continuous flow and with a continuous air supply, i.e.Wastewater continuously flows into aeration tank 6. It is operated aerobically (air inflow) in this tank section, and the activated sludge-containing wastewater continuously flows out at the same rate as the inflow. By adding coagulants, the nutrient phosphorus can also be removed through chemical reactions, if necessary through simultaneous precipitation. This also improves the settling properties of the activated sludge in the secondary clarifier.

[0046] The wastewater from the aeration tank 6, mixed with activated sludge, flows into the secondary clarifier 7.

[0047] In the concept of upstream denitrification, a sometimes considerable part of the wastewater-activated sludge mixture is diverted as so-called recirculation (of the order of magnitude of an integer multiple of the inflow, typically up to about 400%) of the biological process stage from the nitrification effluent before the inflow into the secondary clarifier and is fed again to the biological pollutant load degradation process stage, namely to the inlet parallel to the wastewater inflow before or into the anaerobic denitrification stage(s).This generally ensures that the nitrification biology, which is less active than the carbon degradation biology (with the aim of degrading ammonium), degrades the ammonium components supplied with the pollutant load to the required extent after their (aerobically induced) degradation, resulting in nitrate formation (usually in the wastewater-activated sludge mixture after nitrification with a much higher nitrate concentration than in the wastewater fed to the sewage treatment plant) through the deliberate renewed anaerobic denitrification (usually operated as an upstream denitrification due to efficiency) and in turn through the nitrate degradation taking place there (hence denitrification) in accordance with the wastewater regulations, the required degradation quantities of the nitrate which is otherwise usually only present in very low concentrations in the fed wastewater or sewage water and has just been formed by nitrification.

[0048] The secondary clarifier 7 forms a process unit with the aeration tank 6. In the secondary clarifier 7, the activated sludge is separated from the wastewater by settling. A portion of the activated sludge is returned to the aeration tank 6 as so-called return sludge; this occurs, for example, via the excess sludge removal line 16; this activated sludge is therefore also referred to as return sludge. The activated sludge is returned to maintain the concentration of microorganisms in the aeration tank 6 sufficiently high. If the activated sludge settled in the secondary clarifier (from the pollutant load degradation biology) were not (partially) returned, the degradation efficiency of the bacteria and microorganisms would be too low. The excess or proportional increase in biomass, the so-called excess sludge, is discharged from the secondary clarifier 7 to the sludge disposal line 17. This occurs via an excess sludge removal line.

[0049] Line 19 is also provided, through which wastewater mixed with activated sludge, taken between aeration tank 6 and secondary clarifier 7, is conveyed to tank 5 (in any case, directly to the inflow to the upstream denitrification stage). This line is also referred to as the recirculation line.

[0050] The treated wastewater is discharged from the sewage treatment plant via outlet 8.

[0051] The aim of the invention is to determine the amount of oxygen to be introduced into the aeration tank 6 by means of a measuring system and to always supply the optimal amount of oxygen.

[0052] To supply oxygen to the aeration tank 6, an injection device 18 is arranged in the aeration tank 6. In an advantageous embodiment, the injection device 18 is arranged near the bottom of the aeration tank 6. Ambient air is sucked in at a receiving position 14 and introduced into the injection device 18 into the aeration tank 6. It is also advantageous that the injection device 18 occupies almost the entire bottom of the aeration tank 6 and can introduce variably adjustable large or small bubbles with sucked-in ambient air into the aeration tank 6.

[0053] A control unit 12 is provided, which, via a compressor 10, draws in the ambient air at the intake position 14, compresses it, and pressurizes it, i.e., compresses it, and supplies the air to the injection device 18 in a dedicated pipeline following the compressor via a valve 11 or a control slide or another suitable air flow control device in the supply pipeline. The control unit can control both the activity of the compressor and the individual control of the respective air flow control device. A gas analysis unit 13 is also provided. The gas analysis unit 13 cyclically records the oxygen content of the ambient air drawn in at the intake position 14.

[0054] Furthermore, a collecting device 9 is provided, which is arranged on or above the aeration tank 6. This collecting device 9 collects the gas escaping from the surface of the wastewater in the aeration tank 6, shielded from the ambient air, and analyzes, among other things, its oxygen content and its CO2 content. Based on the values ​​determined by the gas analysis unit 13, the control unit 12 controls the amount of air to be introduced into the aeration tank 6 via the compressor 10 and the valve 11.

[0055] The collecting device 9 is designed so that the collected gas is collected on the surface of the wastewater in the aeration tank, shielded from the environment, and is fed to the gas analysis unit 13.

[0056] The activated sludge in the aeration tank 6 is supplied with oxygen by an adapted supply of compressed air in such a way that the biology, ie the bacteria and microorganisms in the activated sludge, can absorb the oxygen from the introduced air in dissolved form and can breathe it in sufficient quantities, i.e. consume it.

[0057] For example, the so-called alpha value is determined for measurement purposes. The alpha value describes the deviation of the absorption behavior of the specific wastewater from pure water in terms of the physically reduced absorption capacity of dissolved oxygen.

[0058] Pure water has an alpha value of 1. This means that the alpha value (apart from alpha values ​​higher than 1 caused by acid components) is calculated using the following formula: 0 ≤ Alpha ≤ 1 . Alpha = 0.5 means that twice as much oxygen must be supplied in gaseous form to dissolve the same amount of oxygen in the current wastewater as in pure water. This value is multiplicatively coupled to the so-called fouling factor F. The fouling factor F is a defined parameter describing the reduction in oxygen input caused by clogging and decomposition phenomena of the aeration technology, i.e., the wear of the aeration elements in use, such as the respective plastic films or fine-pored ceramic bodies arranged in the injection device 18.

[0059] In addition, the oxygen transfer efficiency, referred to in English as Oxygen Transfer Efficiency (OTE) for short, is calculated, referring to the transfer of oxygen from the gas phase to the liquid phase, thus so-called Dissolved Oxygen (DO) for short, and the oxygen uptake rate (OUR) which describes the amount of oxygen currently consumed by the biology.

[0060] However, each of these parameters has an integral character. This means that these parameters describe an overarching property of the wastewater or sewage condition or of the entire biological degradation process with regard to oxygen input into the activated sludge, which is commonly referred to as the wastewater-biology mixture.

[0061] This also applies to the term "sludge age," which describes the biological species relevant to the process control parameter without further differentiation. This is done despite the fact that the biological processes involved are quite different and should be considered separately, but not independently.For example, there are quite different time courses and intensities of the biological process components due to the very different reproduction times, proportional to the respective average bacterial age of the respective biological component, and thus work activities of the respective pollutant load degrading bacteria, which relate to the so-called nitrification. Nitrification can only run successfully if, in parallel, the far more powerful carbon degrading biology, often called heterotrophic bacteria, is "allowed" to be sufficiently active, i.e., is suitably supplied with "food", carbon-containing pollutant load.

[0062] A differentiation of these parameters, which are typical for the overall process, from the current situation in the respective biological, bacterial-based, separate process is not yet possible.

[0063] The so-called carbon degradation biology, the bacteria and microorganisms involved in this process, is active or works to partially degrade the carbon and contaminant load. During this "work," carbon dioxide, CO2, is produced as a result of respiration from the degraded carbon. This carbon is essentially stripped from the activated sludge by the gas bubble movement of the compressed air introduced and is a typical component of the exhaust air. The supplied compressed air, the ambient air drawn in, contains only about 0.04 vol.% CO2. In addition to utilizing the total oxygen consumed by converting it into CO2, the carbon degradation biology also utilizes up to approximately 25% of the above-mentioned O2 consumption, however, without producing CO2, but rather for its own biomass production (reproduction).Finally, this part of the biology is also capable of extracting some of the oxygen required for carbon degradation as a "fuel" for its carbon reduction from parts of the chemically bound oxygen in the contaminant load, thus "respiring" it. However, this occurs primarily under anaerobic conditions, i.e., without the targeted supply of much more easily absorbed dissolved oxygen (aeration, aerobically controlled process phase) during the usually preceding anaerobic denitrification phase.

[0064] In the case of nitrification, the biology converts ammonium (NH 4 +< ions) that flows in with the pollutant load into nitrite (NO 2 -< ions) (specifically by the Nitrisomonas bacteria) by absorbing dissolved oxygen (O 2 as DO). In a further process step, the resulting nitrite is converted into nitrate (NO 3 -< ions) (specifically by the Nitrobacter bacteria). In addition to a significantly lower demand for oxygen for the organism's own biomass buildup (reproduction) than in carbon degradation biology, the required oxygen is normally consumed in this process without significant other gas production (gas release), i.e., it is bound into nitrite and nitrate. For the build-up of biomass of the nitrification biology, i.e. only for reproduction, only up to a maximum of 6% (compared to the O 2 used for pure ammonium degradation) is used, and thus, from a measurement point of view, a negligible amount of the total DO respired by this biological species.The total oxygen content of the originally supplied compressed air (with a fresh air O2 content of 20.94 vol%) is thus reduced in the aerobic range both by carbon degradation ("high-load biology") and by ammonium degradation ("nitrification biology", "low-load biology").

[0065] The oxygen content of the exhaust air leaving the aerobic aeration tank (usually called off-gas) is therefore characteristic of the biological activity overall, apart from phosphorus components, which are ignored here.

[0066] As a rule, no other gas components are produced in the normal aerobic carbon degradation and ammonium degradation process other than a reduction in O2 content and an increase in CO2 content. Based on the known composition of the supplied compressed air (fresh air), a new, quantitative statement can be made about the respective biological degradation process components by measuring its quantity and the concentration in the exhaust air, far beyond the previous statements about the exhaust air components O2 and CO2, provided that the respective proportions of air humidity (RH; in the supplied compressed air and in the exiting exhaust air) do not differ significantly (on average ±5%). This is certainly the case under the most common normal process conditions and RH is therefore irrelevant for this new type of process control.

[0067] The solution is to determine the difference, here called Delta (Δ), of these metrologically "active" gas mixture components in their sum between the supplied air (fresh air) and the exhaust air (analysis result): Assumption:

[0068] The C-degradation biology needs about ¼ of the amount of O 2 that it consumes for CO 2 production, in addition to its own

[0069] Reproduction (biomass build-up, multiplication); the Δ-reference is therefore: Δ = 0 , 25 * b + Δ NH 4 − Abbau , where: Δ C degradation = 0.25*b and consequently: Δ NH4 degradation = Δ - 0.25*b

[0070] This provides a simple way to determine the contribution of biological processes to carbon degradation and nitrification. The O2 consumption of nitrification biology for its own reproduction, which accounts for only about 6% of the total O2 consumption of nitrification, can be neglected for measurement purposes.

[0071] The information about the course of the relevant biological degradation process components and their proportions among each other is extremely helpful both for general process management and in exceptional cases of process disturbances.

[0072] The proportions between these two essential process components in the aerobic nitrification stage (also called "C-factor" or "CF" for short) can be simply represented as follows:

[0073] The assessment of the proportions and their fluctuations is carried out based on individual experience at the respective on-site wastewater treatment plant. Typically, all daily, weekly, and seasonal effects and patterns are sufficiently recorded after one year at the latest.

[0074] This allows for both statistical recording and a correspondingly automated comparison of the currently determined proportion of the process components CF with previous experience, possibly reflected in a corresponding file. Likewise, abnormal fluctuations can be immediately detected based on the comparison results and used for process-related regulatory purposes. The calculation and evaluation of the CF can be performed in a suitable processor unit in the gas analysis unit 13 or in a separate processor unit installed in addition to the gas analysis unit 13, or in the central control unit 12.

[0075] This provides a new, previously virtually unknown, but now technically determined simple parameter for real-time ("online") process control, which is particularly valuable in experiments aimed at increasing energy efficiency and other process optimizations, allowing direct access to process conditions that were previously only discussed in theoretical considerations beyond the immediate daily practical operation of the wastewater treatment plant.

[0076] This means that process optimizations for further energy savings in the most energy-intensive process in conventional municipal wastewater treatment plants, the aerated (aerobic) biological process stage, can now be carried out in real time ("online") with regard to the effects on the process components and thus significantly for the legally required discharge values ​​(e.g. total nitrogen discharge through ammonium and nitrate).

[0077] This is explained below as an example: Generally forwarded: 20 , 94 Vol . − % O 2 + 0 , 04 Vol . − % CO 2 = 20 , 98 Vol . − % ≈ 21 , 0 Vol . − % Example 1 for exhaust air: 16 , 0 Vol . − % O 2 + 3 , 0 Vol . − % CO 2 + Δ = 2 , 0 Vol . − % = 21 , 0 Vol . − % Example 2 for exhaust air: 17 , 0 Vol . − % O 2 + 2 , 0 Vol . − % CO 2 + Δ = 2 , 0 Vol . − % = 21 , 0 Vol . − % Example 3 for exhaust air: 16 , 0 Vol . − % O 2 + 2 , 0 Vol . − % CO 2 + Δ = 3 , 0 Vol . − % = 21 , 0 Vol . − % Total proportion of C degradation at OV R: 1.25*b in concrete example 1: 3.75 in concrete example 2: 2.50 in concrete example 3: 2.50 Total proportion of NH 4 degradation at OV R: Δ - 0.25*b in concrete example 1: 1.25 in concrete example 2: 1.50 in concrete example 3: 2.50

[0078] The proportions between these two essential process components in the aerobic nitrification stage (see above "C-factor" or "CF" for short) are as follows for the typical exhaust air examples given: Example 1): 3 : 1 CF = 3.0 Permissible fluctuation range normal (±0.6) Example 2): 1.7 : 1 CF = 1.7 Permissible fluctuation range normal (±0.3) Example 3): 1 : 1 CF = 1.0 Permissible fluctuation range normal (±0.2)

[0079] The assessment of proportions and their fluctuations is carried out based on individual experience at the respective on-site wastewater treatment plant. Typically, all daily, weekly, and seasonal effects and typical patterns are sufficiently recorded after one year at the latest.

[0080] The following approaches to regulation now arise: Compressed air supply (compressor 10, valve 11, control slide) according to the calculated target air quantity Q target from OUR Q target = f OUR , on - site data Disturbance of the temporary balance between carbon degradation and nitrification Load requires more nitrification, C degradation normal → oxygen supply must be increased → recirculation rate must be increased → alternatively extraordinary increase of the DO target values ​​Load requires nitrification, but too little COD available → possible artificial C supply Inhibition in denitrification; increased C degradation only in the aerobic process phase → DO target increase to support nitrification due to priority given to C degradation, because → load shift correction depending on the total load (see load requires more nitrification, C degradation normal) Logical load reduction in typical low load times: -- Proportional reduction of DO target to increase efficiency, as long as the typical temporary balance between C degradation and nitrification is maintained within tolerance limits (e.g. CF as usual about 20% of the value); -- approximately a reduction of 1.0 mg / l - as before, e.g.recommended and tested with continuous aeration in all nitrification phases because, for example, there is no regulation based on ammonium values ​​- deliberately set at just 0.7 mg / l - as has already been implemented at a southern German wastewater treatment plant despite the possible risk of O2 deficiency, but with preventative monitoring of the ammonium concentration at the denitrification inlet or after the primary clarification, in order to preventively increase the DO target again as required in good time in the event of an unexpected end to the low load phase or a surge in pollutant load, for example to 1 mg / l or higher, depending on the usual process management in such a case.

[0081] A method for differentiating the process components of carbon degradation and nitrification is described, which uses the formula to calculate the difference between the sums of the process-active gas components in the supplied state, usually recirculated air or fish air, and the result of a process-typical exhaust air analysis, usually the sum of O 2 content and CO 2 content, each in vol.%, and this difference is further split with regard to its qualitative process contributions from "oxygen consumption for the development of the carbon degradation biology" and "oxygen consumption for the nitrification process".

[0082] Furthermore, the proportions between these two essential, differentiated process components can be advantageously used for observation, assessment and control or necessary correction in the event of detected atypical deviations from typical situations, either manually or automatically, e.g. by programming in the process control system.

[0083] In addition, a device for determining the essential process components "carbon degradation" and "ammonium degradation" in the usual aerobic nitrification process in conventional sewage treatment plants is described, which 1. the proportion of O 2 and CO 2 (e.g. in vol.%) is determined from process-typical exhaust air that is isolated from the environment and subsequently analyzed in real time; 2. To simplify the determination of the amount of air supplied or the proportional oxygen (for fresh air O 2 = 20.94 vol.%) which is a key factor in the evaluation [on the system side, this is often an argument that prevents the use of exhaust air measuring technology due to the additional effort required for piping and installation of air flow measuring devices], a suitable gas flow measuring device is installed directly at a defined excess exhaust air outlet of the exhaust air collection hood and is electrically integrated into the evaluation of the exhaust air measuring device, so that the volume-proportional shift of the [sum of the process-neutral gases, e.g. = nitrogen and noble gases = 79 vol.% in the supplied compressed air] and the {100 vol.% minus [sum of the process-involved gases in the exhaust air = (O 2 content in vol.% plus CO 2 content in vol.-%)]} by the resulting addition of the process-neutral gas mixture proportion in vol.%, the constant mass of which and thus the currently supplied total gas mixture mass (e.g. compressed fresh air) and consequently also the supplied mass of the process-active gas mixture components (with compressed fresh air O 2 = 20.94 vol.% and CO 2 = 0.04 vol.%) can be determined from this, whereby the constant exhaust air volume flow, which is led as a bypass for exhaust air analysis to the metrological base unit (known pump characteristics), is to be included as an exhaust air partial flow constant; 3. electronically or in another suitable manner the difference, here called "Delta", in short "Δ", determined from: a) the "sum of O 2 and CO 2 in the gas supplied to the nitrification process step on the plant" (usually compressed fresh air, usually components given in vol.%, so that in the case of compressed fresh air: sum [(O 2 content in vol.% = 20.94 vol.-%) plus CO 2 content in vol.% = 0.04 vol.%)] = 20.98 vol.%, which is therefore approximately 21.0 vol.% in metrological terms and b) the "sum of O 2 and CO 2 in the typical exhaust air escaping from the nitrification process - e.g. according to the equation Δ = 21.0 - {a [O 2 content of exhaust air in vol.%] + b [CO 2 content of exhaust air in vol.%]} , which is the sum [(O 2 residual content in the exhaust air in vol.%) plus (CO 2 content in the exhaust air in vol.-%)]; 4. from this Δ value according to the equation . Δ = 0 , 25 * b + Δ NH 4 − Abbau , where: Δ C degradation = 0.25*b and consequently: Δ NH4 degradation = Δ - 0.25*b the two essential pollutant load degradation process components "carbon degradation" and "ammonium degradation" are each determined individually electronically in a suitable processor unit or in another suitable manner, whereby the proportion of carbon degradation-biology consumption for the plant's own biomass build-up and consequently without carbon dioxide production of 25% of the measured value b is subject to an empirical assumption, which may also deviate from this in the respective specific case, in particular downwards; 5. from the proportion between the determined process components "carbon degradation" and "ammonium degradation", a periodically typical value, e.g. called "C-factor" or "CF" for short, is determined electronically in the control unit 12 or in another suitable manner, according to the equation CF = C − Abbau : NH 4 − Abbau = 1,25 * b : Δ − 0,25 * b ; 6. in an individually manually carried out comparison of the CF determined in real time or in an automated electronic comparison of the determined real-time CF with the proportions determined from experience, which are temporarily typical for the situation and / or already saved as a data set, whereby the assessment of the proportions and their fluctuations is carried out on site according to individual experience at the respective wastewater treatment plant; as a rule, after one year at the latest, all daily, weekly and seasonal (seasonal) effects and typical courses are sufficiently recorded; in the case of serious deviations from CF, e.g. deviations of more than 20% from the CF that is typical for the process based on experience, individual manual process correction must be carried out, individually manually or in a suitably programmed processor unit, such as the control unit 12, or.in the process control system, pre-programmed process control or process regulation interventions are carried out.

[0084] By means of a collecting device 9 arranged on the aeration tank 6, the gas escaping from the aeration tank 6 is collected at a predefined, representative point on the surface of the aeration tank 9, isolated from the ambient air, and the escaping gas quantity is subjected to analysis in the gas analysis unit 13. As part of the analysis, the gas analysis unit 13 determines the oxygen content and the carbon dioxide content in vol.% of the escaping gas collected at the surface of the aeration tank 6. The control unit 12 or another suitable processor unit, to which the data from the gas analysis unit 13 is transmitted, determines the difference between the sum of the oxygen content and the carbon dioxide content between the supplied ambient air, also determined by the gas analysis unit 13, and the gas collected at the surface of the aeration tank 6.From the difference between the sum of the oxygen content and the carbon dioxide content generated by the biological degradation of the contaminant load and the gas components not actively involved in the biological degradation of the contaminant load by changing their concentration, the control unit 12 or another suitable processor unit determines the amount of total oxygen consumption and the proportionately generated carbon dioxide in the aeration tank 6. The control unit 12 reduces the amount of ambient air supplied in presettable steps in accordance with this result, as long as the proportion between the aforementioned difference and the proportionate carbon dioxide content remains unchanged and, if the proportion between the aforementioned difference and the proportionate carbon dioxide content changes, it increases the amount of ambient air supplied by at least the amount of air reduced in the previous step.

[0085] The control unit 12 or another suitable processor unit determines the proportion of the different biological degradation processes involved in oxygen consumption on the basis of the data transmitted by the gas analysis unit 13, so that the degradation of the contaminant load can be varied according to the current proportion in comparison to the proportion expected based on experience by defined substrate supply and / or oxygen setpoint variation in the detected dissolved oxygen and / or by suitable variation of the air supply.

[0086] Based on the distribution of injection devices 18 in aeration tank 6 and based on the known tank volume of each of these tank zones, which are separately regulated with regard to the amount of compressed air supplied, including the geodetic height situation of the sewage treatment plant, the value of the escaping exhaust air in quantity and the composition of the collected exhaust air can be recorded in a process-typical manner with sufficient accuracy, but at least precisely proportionally, for the process, by means of the collecting device 9, which is preferably in the form of exhaust air collecting hoods with a structurally known surface area of ​​the exhaust air collecting hood in relation to the entire tank zone in question of the aeration tank 6, including exhaust air quantity determination, positioned freely floating at a recording-typical location on this tank zone.

Claims

1. Method for controlling the supply of ambient air to an activation tank (6) of a waste water purification plant, with the method steps characterized in that - lit a) by means of a collecting device (9) arranged on the activation tank (6), the gas emerging from the activation tank (6) is collected at a predefinable point on the surface of the activation tank (6), sealed off from the ambient air, and this emerging gas volume is subjected to an analysis, - lit b) as part of the analysis the oxygen and carbon dioxide content in the emerging gas collected on the surface of the activation tank (6) is determined, - lit c) the difference between the sum of the oxygen content and the carbon dioxide content of the supplied ambient air and the sum of the oxygen content and the carbon dioxide content of the emerging gas collected on the surface of the activation tank (6) is determined, - lit d) from the difference between the sums of the oxygen content and the carbon dioxide content according to lit c), produced by the biological pollutant load reduction and the gas components not actively involved in the biological pollutant load reduction in changing the concentration, the amount of the total oxygen consumption and the proportion of carbon dioxide produced in the activation tank (6) from the supplied ambient air is determined, - lit e) the amount of ambient air supplied is reduced in pre-settable steps as long as the proportion between the difference mentioned in lit c) and the proportional carbon dioxide content remains unchanged and - lit f) if the proportion between the difference mentioned in lit c) and the proportional carbon dioxide content changes, the amount of ambient air supplied is increased by at least the reduction of the amount of air in the previous step.

2. Method according to patent claim 1, characterized in that the amount of emerging gas in the method step lit a) is recorded and a typical partial stream thereof is subjected to an analysis.

3. Method according to patent claim 1, characterized in that in the method step lit d) the proportion of the various biological degradation processes involved in the oxygen consumption is determined, so that in the process steps lit e) and lit f) according to the present proportion compared to the proportion reasonably expected, the pollutant load reduction is controlled by defined substrate supply and / or oxygen setpoint variation in the recorded dissolved oxygen and / or by suitable variation of the ambient air supply.

4. Method according to patent claim 3, characterized in that the amount and / or the bubble size of the supplied ambient air is used as a variation of the ambient air supply.

5. Method according to patent claim 3 or 4, characterized in that the pollutant load reduction is controlled in a targeted manner and according to the desired proportions of the process components.

6. Method according to one of the preceding patent claims, characterized in that in the method step lit b) further gas components are analyzed which disturb the reaction process as interfering components in the desired pollutant load reduction due to atypical pollutant load and, by introduction of chemical or further bacterial components or the stripping effect caused by a significant excess of ambient air supply, these interfering components are compensated or chemically deactivated or removed by stripping.

7. Method according to patent claim 6, characterized in that as further gas components volatile hydrocarbons, which are typically contained in solvents as so-called aromatics, are detected.

8. Method according to one of the preceding patent claims, characterized in that the ambient air is sucked in out of the ambient air by means of a compressor (10) arranged on the site of the waste water purification plant and compressed by means of the compressor (10) and supplied to the activation tank (6) via a control slide or a valve (11).

9. Method according to patent claim 8, characterized in that the ambient air sucked in near the activation tank (6) is supplied to the activation tank (6) as required via the control slide or the valve (11) on the basis of the via measurement detected, emerging and analyzed amount of gas.

10. Method according to one of the preceding patent claims, characterized in that both the supplied total amount of ambient air introduced into the activation tank (6) and the amount of oxygen consumption in the activation tank (6) in approximation are determined.

11. Method according to one of the preceding patent claims, characterized in that the differentiation of the process components of carbon degradation and further oxygen-consuming biological contaminant degradation components without gaseous release at the surface of the activation tank (6) from the oxide components emerging in the activation tank, closed from the ambient air, such as, for example, nitrification, in the activation tank (6) is carried out on the basis of the formula Δ = A − a + b at which A represents the O2 content of the supplied ambient air in vol.%, a represents the O2 content of the outgoing air in vol.% and b represents the CO2 content of the outgoing air in vol.% and the carbon degradation in the activation tank (6) being known to consume at least about four-fifths of the amount of oxygen supplied to it for CO2 production, and additionally requires for its own reproduction, the biomass build-up (or its multiplication), so that the Δ reference based on the formula Δ = 0 , 25 * b + Δ NH 4 − degradation , whereby: ΔC-degradation = 0,25*b and therefore: ΔNH4-degradation = Δ - 0,25*b, is given, provided that no other biological components with oxygen consumption and without gaseous oxide emissions are involved, such as for PO43- formation, and the proportions between these two aforementioned essential process parts in the (in this case so-called) aerobic nitrification stage being simplifiable according to the formula CF = C − degradation / NH 4 − degradation = 1,25 * b / Δ − 0,25 * b assuming that the carbon removal biology here consumes 25% of the oxygen consumed for carbon dioxide formation, additionally for its own biology build-up without carbon dioxide formation.

12. Method according to patent claim 11, characterized in that twenty-one is assumed as the numerical value for A.

13. Method according to one of the preceding patent claims, characterized in that the waste water purification plant generally comprises - a waste water inlet (1, 2) with a variable inflow volume, - a separation unit (3) for the mechanically retainable coarse contaminants contained in the waste water, which is arranged downstream of the waste water inlet (1, 2), - a sedimentation tank (4) connected downstream of the separation unit (3), in which substances that are contained undissolved in the waste water and have a significantly higher density than water settle to the bottom of the sedimentation tank and substances that are contained undissolved in the waste water and have a significantly lower density than water accumulate at the surface of the waste water in the sedimentation tank (4), - the activation tank (6), to which waste water from the sedimentation tank (4) is supplied and which contains activated sludge with aggregated bacteria and other microorganisms, which biotically oxidatively degrade waste water constituents, and water mixed with activated sludge runs out of the activation tank (6) at the same rate as dirty water is supplied from the sedimentation tank (4), whereby ambient air, which is taken from the vicinity of the activation tank, is blown into the area at the floor of at least part of the activation tank (6) in the form of fine bubbles under pressure, at least intermittently or continuously, - a clarification tank (7) into which the water mixed with activated sludge flows and in which the activated sludge is separated from the treated waste water by settling, and - an outlet (8) by which the treated waste water leaves the treatment plant from the clarification tank (7).

14. Device for the use in a method according to one or more of the preceding patent claims 1 to 13, consisting at least of a control unit (12), a collecting device (9) that is arranged at a predefinable location on the surface of the activation tank (6) and collects parts of the gas emerging from the activation tank (6), sealed off from the ambient air, and supplies the collected amount of gas to a gas analysis unit (13), wherein ambient air is also supplied from a receiving position (14) to the gas analysis unit (13) and the gas analysis unit (13) determines the difference between the sum of the oxygen content and the carbon dioxide content of the supplied ambient air at the receiving position (14) and the gas collected by the collecting device (9) at the surface of the activation tank (6) and supplies it to the control unit (12), whereby the control unit (12) controls the compressor (10), which draws in ambient air in the vicinity of the receiving position (14), compresses it and feeds it to the activation tank (6) via the control slide or the valve (11), whereby the control unit (12) reduces the amount of supplied ambient air in pre-settable steps by means of the compressor (10) as long as the proportion between the carbon dioxide content in the exhaust gas and the difference between the sum of the oxygen content and the carbon dioxide content between the supplied ambient air and that of the gas collected on the surface of the activation tank (6) by means of the collecting device (9) remains unchanged, however, the control unit (12) increases the amount of supplied ambient air by means of the compressor (10) in pre-settable steps, if the proportion between the carbon dioxide content in the exhaust gas and the difference between the sum of the oxygen content and the carbon dioxide content between the supplied ambient air and the gas collected on the surface of the activation tank (6) by means of the collecting device (9) changes.