Aerobic biological wastewater treatment in a continuous-flow reactor.

Abstract

The present invention relates to a method for purifying substrate-containing wastewater in a continuous flow-through aerobic biological activated sludge reactor B. In this method, after a pretreatment step VB of the supplied wastewater 1, at least a portion of the biological sludge 6 is conditioned in a classifier S under anaerobic or anoxic conditions with at least a portion of the substrate-containing wastewater 2 to be purified, so that at least 20 wt% of the sludge in the classifier S has a residence time in the classifier that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the classifier. After an additional anaerobic or anoxic contact step, the conditioned sludge / water mixture 3 is then fed to an aerobic purification reactor B and subjected to aerobic treatment B, where the aerobically treated wastewater 4 is separated from the sludge by settling NB, flotation or mechanical separation, and the sludge separated from the aerobically treated wastewater is returned to the classifier as return sludge 6.

Description

[Technical Field]

[0001] This invention relates to the field of aerobic biological wastewater purification in a continuous flow-through reactor using aerobic granular sludge. [Background technology]

[0002] To protect aquatic environments, biological treatment of wastewater from residential, urban, and industrial activities is a crucial activity. Numerous biological purification technologies are known, broadly categorized into anaerobic and aerobic technologies. Both technologies utilize microorganisms, which convert wastewater pollutants into less harmful substances by using them as a substrate. In anaerobic technologies, microorganisms (MOs) proliferate in a mixture of wastewater and microorganisms with minimal oxygen addition. MOs primarily convert pollutants into methane gas and further MO growth. Examples of such anaerobic technologies include BioBulk, UASB, EGSB, and anaerobic MBR. An advantage of this type of technology is the availability of methane gas. However, a major drawback is that wastewater treatment performance is quite limited, often requiring subsequent aerobic treatment to adequately protect the aquatic environment. It should be noted that the present invention described below is not part of this anaerobic type of purification technology.

[0003] In aerobic technology, oxygen is supplied to the MO by various methods, for example, by introducing air through surface aeration devices, bubble aeration devices, or other means. Aerobic MOs primarily convert organic carbon pollutants into carbon dioxide and MOs.

[0004] Furthermore, in addition to aerobic MOs, there are aerobic technologies in which process conditions are set in a way that allows MOs capable of removing nutrients such as nitrogen and phosphates from wastewater to proliferate. Such process conditions often include so-called anaerobic and oxygen-free conditions. Under oxygen-free conditions, in addition to organic pollutants, nitrogen oxide compounds such as nitrites and nitrates are also present, and MOs that convert these into harmless nitrogen gas can proliferate. Under so-called anaerobic conditions, the concentration of such nitrogen oxide compounds is limited or absent altogether. Under such conditions, MOs capable of accumulating phosphates, such as PAOs (phosphate-accumulating organisms), can proliferate. It should be noted that the term "anaerobic" in relation to these process conditions is commonly used and is similar to the term used in anaerobic remediation technologies, but it represents a very different type of MO and should not be confused with the MOs in the aforementioned anaerobic remediation technologies that mainly produce methane. It should also be noted that there are certain MOs that can convert ammonium containing nitrites into nitrogen gas. This type of MO is often called anamox (oxygen-free ammonium oxidizer). This type of MO cannot thrive in the presence of carbon pollutants, nor can it remove these important pollutants. Therefore, techniques using anammox MO do not belong to aerobic wastewater treatment, and such aerobic purification elements are often required as a pretreatment for generating nitrites from ammonium or organic nitrogen pollutants.

[0005] The most commonly used and, until recently, most widely applied aerobic wastewater treatment technology worldwide is the so-called continuous (or flow-through) activated sludge system. The so-called carousel technology described in European Patent No. 0474296 is an example of such an embodiment. MO (Molybdenum Oxide) is grown in the form of sludge flocs, which circulate with the wastewater in a carousel treatment reactor, thus being exposed to both aerobic and anaerobic conditions. There are also carousel embodiments with an upstream anaerobic reactor to allow for the growth of PAO MO in the circulating activated sludge. After contaminants have been removed from the wastewater by MO in the activated sludge (AS), the AS is separated from the water by sedimentation, flotation, thin-film filtration, or other means, and the AS is returned to aerobic, anaerobic, and / or anaerobic process conditions. For proper and rapid separation of the AS, it is important that the AS has good settling properties. Therefore, so-called sludge separators are often used in AS systems, where recycled AS is thoroughly mixed with untreated wastewater to suppress the growth of so-called filamentous MO, which has poor settling characteristics. Such sludge separators can be used in many embodiments and may have one or more compartments or reactors, are always well mixed, and can operate with or without aeration. In addition, to promote the growth of PAO, the contact time of the non-aerated sludge separator can be extended by a built-in or continuous non-aerated contact tank. A feature of these sludge separators, with or without a built-in or continuous non-aerated contact tank, is that the activated sludge and water are thoroughly mixed, and the residence time of the sludge in the sludge separator is the same as the residence time of the sludge / water mixture. In other words, the sludge residence time (SRT) is the same as the hydraulic residence time (HRT). Another feature is the control that all sludge in the sludge separator has the same SRT, and if the distribution of SRT is unexpectedly limited, this distribution corresponds to sludge particles of different sizes. Note that the present invention described below is not relevant to this type of sludge separator where HRT=SRT.

[0006] A new type of aerobic activated sludge system utilizes granular sludge instead of coagulant activated sludge. Scientifically, aerobic granular sludge is defined as sludge with a size of at least 0.212 mm and typically less than 6 mm, so that coagulation does not occur during sedimentation, and the sludge volume index (a measure of sludge sedimentation characteristics) after 5 minutes of sedimentation corresponds to the index after 30 minutes of sedimentation. The main advantage is that aerobic granular sludge settles much faster (4-40 m / h) than cottony activated sludge (0.5-2 m / h), and if the granules are large enough, the aforementioned necessary anaerobic and anoxic conditions for nutrient removal are created. This allows for simultaneous denitrification and coagulation of phosphates at deeper levels of the granules, even when the granular sludge is aerated and the aerobic MO in the outer layer of the granules decomposes organic carbon pollutants. Therefore, compared to activated sludge systems, circulation and propulsion are required with little to no force to expose the sludge to various requirements, resulting in 20-50% energy savings. However, this requires that the sludge have a granule size of 0.4 mm, preferably greater than 1 mm (and preferably less than 6 mm), depending on the applied aeration conditions; otherwise, denitrification capacity will not be achieved at all or only insufficiently at deeper levels within the granules. In addition, the construction cost of a granular sludge treatment plant is significantly lower than that of an activated sludge system. On the one hand, the rapid settling of the sludge reduces the required hydraulic residence time in the purification reactor and clarifier, while on the other hand, the good settling characteristics of granular sludge result in a much higher amount of MO. For comparison, while activated sludge systems often use MO concentrations of 3-5 g / l, this is 8-20 g / l for granular sludge systems.

[0007] The first granular sludge technology widely applied in practice for aerobic wastewater purification is described in International Publication No. 2004 / 024638. Several important process-technical conditions exist to achieve the transition from activated sludge to granular sludge and to maintain the granules during the purification process. Since the granular sludge is exposed to an "anaerobic" stage (where anaerobic means "not aerated," and strictly speaking, this stage can also be oxygen-free (in the presence of nitrates)), it is essential that the MO can absorb organic carbon pollutants. During aerobic treatment, this absorption is important so that the MO can consume the absorbed carbon pollutants, which is a crucial condition for achieving granule formation. In addition, this carbon is necessary to convert nitrogen oxide compounds into nitrogen gas in the oxygen-free and anaerobic portions of the granules. Furthermore, it is important to limit the amount of cottony activated sludge. After absorption in the aforementioned anaerobic stage, some carbon pollutants remain in the wastewater, resulting in the proliferation of a limited amount of activated sludge flocs. To create these crucial process conditions, International Publication 2004 / 024638 uses a continuous batch reactor (SBR) type of purification reactor with discontinuous wastewater feed. In the first stage, wastewater is fed into the reactor from the bottom, so that undiluted wastewater comes into contact with granules capable of absorbing organic matter. Subsequently, the wastewater supply is stopped and the supply of oxygen-containing gas is started. After aerobic, anaerobic, and anaerobic biological conversions have been sufficiently carried out to purify the wastewater to the desired water quality, the sludge with the worst settling characteristics, along with the formed cottony sludge, is discharged from the reactor. Separation of flocs, worse settling sludge, and better settling sludge is achieved by discharging the sludge only after a certain degree of sludge settling has already occurred, and by discharging the sludge from the top of the reactor. In academic literature, this separation is also called selective pressure.

[0008] Since the first practical implementation of aerobic granular sludge and its operating method and embodiments, first described in International Publication No. 2004 / 024638, this technology has rapidly replaced the application of activated sludge systems due to its many advantages. However, the main drawback of this method and embodiments is that it is performed in SBR, while the majority of existing treatment plants are based on continuous activated sludge. The conversion from continuous feed reactors to discontinuous feed reactors is not straightforward. Driven by the many advantages of granular sludge and the aforementioned scientific insights into the stringent process conditions required for its formation, many attempts have been made to apply granular sludge to continuous flow-through treatment reactors as well. For example, International Publication No. 2017 / 025345 describes a process in which a separator is used to separate a portion of the activated sludge from the aeration tank of a continuous activated sludge system into two parts, namely a fast settling portion and a slow settling portion, and the fast settling portion is mixed with the wastewater and return sludge to be treated in an anaerobic tank.

[0009] U.S. Patent Application Publication No. 2020 / 0002201 describes a continuous activated sludge system in which a portion of the activated sludge recycled from the final clarifier to the start of the continuous purification process is treated in a “culture vessel” before being recycled to the start of the continuous activated sludge system. The disclosed treatment method includes the application of anaerobic and anoxic conditions, thereby also providing an additional carbon source by adding chemicals or by fermenting a portion of the sludge by primary sedimentation. In addition, at various points in the process, separators are used to selectively discharge slow-settling sludge. Similar to International Publication No. 2004024638, this process provides all the conditions necessary to achieve granule formation, namely, an anaerobic stage and selective pressure applied by a separator. However, published results from field trials of this process (IWA Innovation Conference on Sustainable Wastewater Treatment and Resource Recovery, Shanghai (November 2019)) show that this method does not produce widespread granulation, with only about 30% of all sludge being larger than the scientifically low granule limit of 0.212 mm, and over 90% being smaller than 0.25 mm. The granular sludge content large enough to enable the aforementioned simultaneous denitrification requires a granule size of at least 0.5–1 mm, which is negligible. As a result, only a small fraction of the potential benefits of granular sludge purification can be realized in a continuous activated sludge process.

[0010] A similar process is described in International Publication No. 2019 / 195918. Here, the sludge is recirculated from secondary sedimentation to a separate compartment, separate reactor, or series of reactors under anaerobic conditions, and then the sludge is mixed with raw wastewater in yet another compartment, separate reactor, or series of reactors exposed to anaerobic conditions. International Publication No. 2019 / 195918 also applies selective pressure by discharging less settled sludge into the sludge treatment line. The shortcomings of the aforementioned U.S. Patent Application Publication No. 2020 / 0002201 appear to apply here as well.

[0011] Within the scope of current prior art, it is continuously necessary to further implement and optimize the method described in International Publication No. 2004 / 024638, and to achieve, for example, widespread granular sludge formation in the continuous flow-through system described above. [Overview of the project]

[0012] The inventors have experimentally demonstrated that, regardless of the use of the sludge separator described above in relation to carousel technology, and regardless of whether the sludge separator is incorporated into or followed by a non-aerated tank, and regardless of whether an anaerobic stage precedes it, the aforementioned continuous system cannot be used to convert the majority of the sludge and maintain it at a desired granule size of at least 0.4 to 1.0 mm on an industrial scale, as in the prior art, and regardless of whether the sludge separator is incorporated into or followed by a non-aerated tank, and regardless of whether an anaerobic stage precedes it. However, in this study, the inventors have demonstrated that there is a correlation between the granule size of individual sludge particles with different settling characteristics or sizes and the degree of distribution of sludge residence time in an anaerobic or anaerobic contact tank or separator. The inventors subsequently used this remarkable insight to develop improved methods and device embodiments for continuous-feed flow-through aerobic biological purification reactors, based on International Publication Nos. 2004 / 024638 and 2017 / 025345, which expand the sludge residence time distribution, enabling the conversion of conventional activated sludge into sludge with broad granule formation, thereby, for the first time, actually matching the advantages previously only achievable in granule sludge technologies using SBR.

[0013] In practice, the inventors have found that this can be achieved by using a separator under anaerobic or oxygen-free conditions prior to aerobic purification, thereby actively providing or controlling that larger sludge and / or higher settling rates in the separator are in contact with the substrate-containing wastewater for a longer period (i.e., longer than smaller sludge and / or lower settling rates). This can be achieved, for example, by applying to the separator (i) multiple stages in which the flow velocity changes individually or discontinuously, (ii) an increasing flow gradient (i.e., a continuously increasing flow velocity), or a combination of (i) and (ii). Both methods result in a distribution of settling rates (allowing for portions with low and high settling rates), increasing the contact time and substrate concentration of larger granules in contact with the wastewater. This is an improvement on the process described in International Publication No. 2017 / 025345. The function of the separator is to allow a longer residence time for at least a substantial portion of the large sludge granules than the hydraulic residence time of the adjusted sludge / water mixture, and preferably, to expose the large sludge particles to a higher substrate concentration. Thus, an embodiment (i) in which the flow velocity is individually varied is preferred. This can be more advantageously realized in (a) a continuous form by causing a change in the flow direction of the separator at a constant water / sludge flow rate, and / or in a semi-batch step in which the change in the flow velocity of the separator is realized by a change in the water / sludge flow rate. Different embodiments (i)(a), (i)(b), and (ii) will be further described in detail in the detailed description and drawings.

[0014] Within the scope of advantageous wastewater treatment utilizing aerobic granular sludge technology, the present invention relates in particular to a method for purifying substrate-containing wastewater in a continuous flow-through aerobic bioactive sludge reactor, wherein at least a portion of the biological sludge (whether or not after a conventional pretreatment step of the incoming wastewater) is prepared in a separator under anaerobic or anoxic conditions using at least a portion of the substrate-containing wastewater to be purified, wherein at least 20 wt% of the sludge in the separator has a residence time in the separator that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the separator, preferably with larger sludge particles in contact with the highest substrate concentration, and thereafter (whether or not after a final additional anaerobic or anoxic step) the prepared sludge / water mixture is supplied to an aerobic purification reactor, undergoes (conventional) aerobic purification, and the treated (purified) wastewater after aerobic purification is separated from the sludge.

[0015] By doing so, sludge particles with larger size and / or faster settling characteristics have a longer contact time with the substrate-containing wastewater than sludge particles with smaller size or slower settling characteristics. By using a sorter, the adjusted sludge / water mixture is fed into the aerobic remediation reactor (whether or not after the final additional anaerobic or anoxic step), and at least 20 wt% of the sludge is granular sludge. Preferably, the proportion of granular sludge is at least 25 wt%, preferably at least 30 wt%, most preferably at least 40 wt%, and particularly at least 50 wt%, and preferably at least 20 wt% of this granular sludge (i.e., sludge with a size of at least 0.212 mm), or more preferably at least 25 wt%, preferably at least 30 wt%, most preferably at least 40 wt%, and particularly at least 50 wt%, of this granular sludge in aerobic biological remediation reactor B has a particle size of at least 0.4 to 1.0 mm.

[0016] The sludge separated from the aerated treated wastewater can be returned to the separator (as return sludge). This return establishes the continuous nature of the wastewater treatment and ensures that an effective granular sludge size distribution is formed and maintained. In other words, in the above method, the sludge is treated in the separator under anaerobic or anoxic conditions, and the large sludge particles are adapted to have a long contact time with the wastewater. In addition, preferably, the large sludge particles in the separator are also realized to contact more with a higher substrate concentration than the small sludge particles. In practice, the substrate concentration varies greatly due to fluctuations in the wastewater composition and the intake by the MO of the separator. It is preferable that at least 10 wt% of the largest sludge particles contact the highest substrate concentration in the separator for at least 20% longer than the average contact time of the sludge, and the substrate concentration is preferably at least 50% higher than the substrate concentration with which 15 wt% of the smallest sludge particles contact.

[0017] In the context of the present invention, the aforementioned improved sedimentation rate distribution, the increase in both the contact time between the large granules and the wastewater and the substrate contact concentration, and their related characteristics are realized using a separator, preferably within 200 days, more preferably within 150 days after the start of the method development. As shown in FIGS. 11 and 12A, without using a separator, these goals are not achieved after the start stage.

[0018] [[ID=VIII]]In one embodiment, the sludge / water mixture in the separator is subject to individual changes in flow rate and / or flow rate gradient under anaerobic or anoxic conditions. In a particular embodiment, the individual change in flow rate is realized by an individual change in the flow within the range of the flow direction of the separator and / or by an individual change in the flow rate of the supplied wastewater and / or return sludge.

[0019] The term "individual change" in the context of the present invention refers to a distinguishable discontinuous change in flow rate.

[0020] In certain embodiments, the sorter has a first step of separating a portion of the sludge into a fast-settling section and a slow-settling section under anaerobic or oxygen-free conditions, and a mixture of wastewater and the fast-settling section or slow-settling section is selected, which is then separated again into a fast-settling section and a slow-settling section in at least a second step of the sorter. To perform separation in different steps of the sorter, a selection based on the settling rate is preferably applied at any point in the upward flow column, and the upward flow velocity of the wastewater passing through different steps of the sorter can be individually and independently adjusted as a parameter. This enables discontinuous or individual changes in flow velocity. This can be achieved, for example, by an upward flow column having concentrically arranged compartments that together form the sorter. The upward flow velocity at each step of the sorter is preferably 1 to 25 m / h. The upward flow velocity at each step of the sorter is preferably lower than the upward flow velocity of the previous step, and in each case, is preferably 25 to 50% of the upward flow velocity of the previous step. The separator preferably has at least a third step, in which the fast-settling or slow-settling section from the second step is further separated into a fast-settling or slow-settling section, after which the sludge-treated wastewater flow and sludge are supplied to a conventional purification reactor, and the remainder is returned to the step prior to the separator. This third step is preferably to avoid the accumulation of sludge that settles very rapidly. Such versatility in the sludge separation step based on the settling rate / flow rate variation of the anaerobic separator achieves the goal that at least 20% of the sludge in the separator has a residence time in the separator that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the separator. This goal is also achieved in that at least 10 wt% of the largest sludge particles are in contact with the highest substrate concentration in the separator for at least 20% longer than the average contact time of the sludge, and this substrate concentration is at least 50% higher than the substrate concentration to which 15 wt% of the smallest sludge particles are in contact. Such an embodiment is schematically shown in Figure 2.

[0021] In another embodiment, the sorting machine is a semi-batch step in which the sludge comes into contact with the reactor wastewater under anaerobic or oxygen-free conditions, and the feed rate changes.

[0022] In another specific embodiment, the separator separates by creating a gradient (increase or decrease) in the flow velocity, causing continuous separation downstream of the sludge based on the sedimentation rate by the separator, and the sludge residence time of the separator increases with the increase in the sedimentation rate. To achieve the goal, the gradient can be adjusted accordingly. Such embodiments are schematically shown in FIGS. 3-6. In these cases, a continuous increase in flow rate is brought about.

[0023] In each of these embodiments, the goal is that at least 20% of the sludge in the separator has a residence time in the separator that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the separator. Preferably, the proportion of the granular sludge (sludge with a size of at least 0.212 mm) in the aerobic biological purification reactor B is at least 25 wt%, preferably at least 30 wt%, most preferably at least 40 wt%, especially at least 50 wt%, and preferably at least 20 wt% of this granular sludge (that is, sludge with a size of at least 0.212 mm), or more preferably at least 25 wt% of this granular sludge, preferably at least 30 wt%, most preferably at least 40 wt%, especially at least 50 wt% has a particle size of at least 0.4 - 1.0 mm. In addition, preferably, it is also realized that the large sludge particles in the separator contact more with a higher substrate concentration than the small sludge particles. Those skilled in the art can adjust the supply rate and flow rate parameters to achieve these goals.

[0024] In any of these embodiments, sludge accumulation in the sorter can be prevented by periodically increasing the degree of mixing or flow rate over an adjustable period, thereby directing the more rapidly settling sludge to the downstream aerobic reactor. Furthermore, in any of the embodiments, the proportion of sludge flocs can be further reduced by withdrawing at least a portion of the excess sludge from the sorter location where the proportion of worst-case settling sludge particles is highest. Preferably, this mixing is performed at a frequency of no more than twice per hour, more preferably no more than once per hour, and even more preferably no more than once every four hours. The duration of this mixing depends on several factors, including the hydraulic residence time, and is preferably at least 5 minutes, more preferably at least 15 to 30 minutes. [Brief explanation of the drawing]

[0025] [Figure 1] The basic principle of the improved continuous flow-through biological purification according to the present invention is shown. [Figure 2A] This shows the fluid flow in wastewater treatment according to the present invention. [Figure 2B] This shows the fluid flow in wastewater treatment according to the present invention. [Figure 2C] This shows the fluid flow in wastewater treatment according to the present invention. [Figure 3] This shows the fluid flow in a modified wastewater treatment system according to the present invention. [Figure 4A] Figure 3 is a top view showing the modified form incorporated into a circulating or plug-flow activated sludge system. [Figure 4B] Figure 3 is a side view showing the modified form incorporated into a circulating or plug-flow activated sludge system. [Figure 4C] Figure 3 is a side view showing the modified form incorporated into a circulating or plug-flow activated sludge system. [Figure 5] This shows the sludge retention time distribution in a circulation or plug-in flow system. [Figure 6A] This figure shows the positions of a to a' in Figure 6B. [Figure 6B] This shows a configuration in which sludge is supplied immediately after the baffle. [Figure 7] This shows how wastewater is distributed on the bottom of the sorting machine. [Figure 8A] This illustrates a configuration in which wastewater and returned sludge are supplied alternately. [Figure 8B] Another configuration is shown in which wastewater and returned sludge are supplied alternately. [Figure 9A] This diagram uses only one intermittently operating sorting tank / sorting section. [Figure 9B] The height of zone a increases over time. [Figure 10] This shows that at least a portion of the returned sludge originates from conventional wastewater treatment. [Figure 11A] The results of experimental examples using conventional processing are shown. [Figure 11B] The results of Example 1 according to the present invention are shown. [Figure 11C] This shows the results of determining which substrate concentrations sludge particles of different sizes came into contact with and for how long they remained in contact. [Figure 12A] This shows the time-dependent changes in the sludge capacity index and sieve classification of aerobic granular sludge in a flow-through pilot-scale configuration after planting, compared to a conventional configuration. [Figure 12B] Figure 8 shows the time-dependent changes in the sludge volume index and sieve classification in a flow-through pilot-scale configuration after the planting of aerobic granular sludge. [Modes for carrying out the invention]

[0026] The following describes various possible actions and embodiments of the present invention, all of which aim to achieve granulation through the improved distribution of sludge retention times described above. Those skilled in the art will recognize that the methods and embodiments described share the commonality of achieving a significant distribution of sludge retention times and combining this distribution with contacting the sludge with untreated wastewater or contaminated sidestream so that the largest sludge particles are exposed to prolonged contact and high substrate contact concentrations. Furthermore, those skilled in the art will recognize that the methods described do not exclude variations, alternatives, and other embodiments that achieve the same effect, and that such embodiments and similar methods are part of the same invention.

[0027] Figure 1 illustrates the basic principle of the improved continuous flow-through biological purification according to the present invention. Wastewater 1 is optionally pretreated first in a primary sedimentation tank VB and then supplied to a sorter S via 2, where it is mixed with return sludge 6. From the sorter S, the wastewater / sludge mixture flows to a biological activated sludge treatment reactor B, after which sludge from the purified wastewater / sludge mixture 4 is preferably separated from the treated wastewater in a secondary sedimentation tank NB5 and returned to the sorter, at least partially (as 6). A portion of the sludge that grows during the purification process is discharged from the process. This discharge of excess sludge 7 can be carried out at different process locations or in combination of locations.

[0028] Those skilled in the art will understand that pretreatment VB may have various embodiments, but are not limited to, screens, sieves, filters, cyclones, gravity sedimentation tanks, lamellar sedimentation tanks, flotation devices, etc. Biological remediation reactor B may be any conventional embodiment of a continuous flow-through activated sludge reactor, but is not limited to, including oxidation trenches, plugged streams, CSTRs, Bardenphos, UCTs, etc. Such a biological remediation reactor typically also has compartments or sub-reactors where aerobic, anaerobic, and oxygen conditions are maintained.

[0029] In relation to the present invention, flow 6 is synonymous with biological sludge, sludge, and return sludge. As will be described in detail in Figure 10, in the method according to the present invention, at least a portion of the return sludge may be generated from conventional wastewater treatment.

[0030] In this embodiment, the desired distribution of sludge residence time is achieved by a change in flow direction. The separator S is a compartmentalized upward-flow reactor having concentrically oriented compartments, as shown in the cross-section of Figure 2A, where it is preferable that the effective volume of compartment Sa is smaller than the effective volume of Sb and simultaneously smaller than the effective volume of Sc. In an alternative configuration (Figure 2B), the separator is fitted with three adjacent, connected compartments Sa, Sb, and optionally Sc, with regulated volumes, where the effective volume of compartment Sa is smaller than the effective volume of Sb. In both Figures 2A and 2B, it is also possible to operate with only compartments Sa and Sb. (Return) Sludge 6 is introduced at the bottom level of compartment Sa, where it comes into contact with at least a portion of the wastewater 2. The remainder of the wastewater 2 is introduced at the bottom of the other compartments. Due to the vertical flow in compartment a, a significant sludge residence time distribution is intentionally achieved by the sludge residence time of individual sludge particles, determined by their individual settling characteristics. Particles with a settling characteristic (settling velocity) much lower than the vertical flow velocity are carried out of compartment a by the upward flow and do not remain in this compartment longer than the residence time of the water. However, sludge particles with a settling characteristic higher than the liquid velocity remain in this compartment longer than the water, and the fastest settling sludge particles accumulate at the bottom of compartment Sa and flow from there to compartment Sb. MO, which is important for the formation of granular sludge, preferentially incorporates the substrate through contact with nutrient-rich water and under anaerobic or anoxic conditions, and therefore has the best settling characteristics, and the sludge particles can remain as granular sludge, gaining the advantage of biological selection for proliferation into granular sludge.

[0031] Next, the sludge particles enter compartment Sb via the overflow or underflow of compartment Sa, depending on their settling rate. The fluid velocity in chamber Sb is lower than that in compartment Sa. This also gives the sludge a significant sludge residence time distribution, and equally important is that the sludge with the best settling characteristics has a longer contact time and is exposed to more concentrated wastewater. In the end, particles with a settling velocity equivalent to the liquid velocity remain in the compartment for as long as the liquid and are in contact with the less diluted wastewater at the bottom of the compartment for a relatively short time. The high-speed settling section, along with the best settling particles from the bottom of compartment a, remains at the bottom of compartment Sb for a considerably longer time and can take up further substrate. A similar effect occurs in compartment Sc, supplied from compartment Sb via the bottom and overflow. Here again, individual sludge particles that settle more rapidly are in contact with the most concentrated wastewater for the longest time. Of course, following the same principle, the sorter may be extended with further compartments (Sd, Se, ...).

[0032] To prevent the accumulation of sludge particles that settle too rapidly in the final section (section Sc in Figures 2A and 2B), it is preferable that this section be mixed continuously or intermittently by mixer M. This mixing can be achieved by using a mechanical agitator or thrust, by introducing a gas, or by sizing the final section such that the resulting vertical liquid flow rate is greater than that in section a. Although this gas may be oxygen or an oxygen-containing gas, the gas in the final section will at best shorten the effective anaerobic contact time of the separator, so the separator is considered to be an anaerobic or oxygen-free reactor.

[0033] The size of the compartment and the resulting velocity are selected so as to produce the aforementioned target level of sludge residence time distribution.

[0034] In the schematic diagram of Figure 2, in addition to compartment Sa, two further compartments Sb and Sc are also shown. Based on the information presented herein, those skilled in the art will recognize that at least one further compartment Sb is required to carry out the present invention, and that further compartments (Sb, Sc, Sd, Se…) may be used to further optimize performance and operational robustness. As the number of further compartments increases, so does the possibility of further increasing and controlling the sludge residence time distribution. This also applies to the method of compartmentalization, as well as how the required flow patterns and mixing are achieved in the relevant compartments. For example, a rectangular tank is preferably designed to have only compartment Sa and one further compartment Sb. Optionally, overflow from the further compartment is transferred to the lower part of a further (preferably adjacent) compartment via a conduit.

[0035] Furthermore, the inflow of wastewater 2 may be from the bottom of the compartment, and the supply of return sludge 6 may be at the liquid level of the compartment. In this case, the dividing wall between compartments does not need to have an opening between compartments at the bottom. This is shown in Figure 2C for compartment Sa only. The liquid velocity of wastewater 2 in compartment Sa is selected so that the sludge particles of 6 are flushed out into compartment Sb. Sludge particles with a high settling velocity remain in compartment Sa longer than particles with a low settling rate before being swept away by the upward-flowing wastewater. Thus, the desired distribution of contact time and substrate contact concentration is also achieved. As shown in Figure 2A, several compartments with wastewater supply sections at the bottom can be adjacent to one another.

[0036] Figure 3 shows another preferred modification, in which the sorter S is designed with an inclined bed v so that the liquid velocity increases with the flow. The wastewater 2 and (return) sludge 6 are in close contact with each other at the inlet side, and the wastewater is uniformly distributed over the bottom, or optionally, this is preferably achieved by a mixer M. Next, the water / sludge mixture flows to the right (in the direction of the inclined bed v), so that the liquid velocity steadily increases. The fastest settling sludge particles concentrate around the bottom at the start of the sorter, and then, with increasing flow velocity, can move through the inclined bed v to the beginning of the sorter. Sludge particles that do not settle as rapidly have a shorter residence time in the sorter 3. Thus, the desired distribution of sludge residence time is obtained.

[0037] Those skilled in the art will recognize that this preferred modification may be incorporated into a circulating or plug-in activated sludge system, as shown in Figures 4A, 4B, and 4C. Figures 4B and 4C are side views, and Figure 4A is a top view. Figure 4B shows how the preferred modification of Figure 3 can be realized by providing rising ridges or deflection baffles between segments a, a' of the circulating activated sludge system. These deflection baffles increase the flow velocity on the deflection baffles, causing sludge particles with sufficiently high settling velocities (i.e., higher than the flow velocity) to flow upstream of the deflection baffles, or at least downstream at a slower speed, and thus to be in contact with the wastewater before or first entering the deflection baffles for a longer period of time. Periodically, a mixer or impeller is operated for a period of time. Depending on preference, the (return) sludge 6 can be supplied immediately before the baffle (Figure 4B), immediately after the baffle (Figure 6B, described later), or at any other location, for example, through an existing return sludge inlet. In this embodiment, it is important that sufficient anaerobic time for hydrolysis and adsorption of organic pollutants by the sludge is obtained in segments a to a'. Figure 4C shows how the same is achieved in the flow direction by the slope of the recessed bottoms of segments a and a'. Naturally, this is also true for segments of the plug-in flow system.

[0038] Similar to the preferred variant described above, further sludge retention time distributions are supported by changes in the daily wastewater flow rate, and the mixer or propeller can be operated periodically to prevent the accumulation of optimally settled sludge particles in the sorter.

[0039] In another preferred variant, the sludge residence time distribution of a circulating or plug-in flow system is obtained by partially widening the channel width to create a change in liquid velocity and the best settling of sludge particles to the bottom. See Figure 5. This is an intermediate form between discontinuous flow rate changes and continuous flow gradients.

[0040] When installing a sorting machine in an existing environment, applying the preferred modification described above may be constructively difficult or cost-inefficient. In such cases, the preferred modification shown in Figure 6 is supported. The operation is identical to that in Figure 4A or Figure 4B, but here the increase in liquid velocity is achieved by placing deflection baffles d before the wastewater and return sludge enter. The decrease in flow velocity immediately after these baffles causes larger granules to settle to the bottom and come into contact with the feed. As with the previously described configurations, in this modification, it is important that sufficient anaerobic time for hydrolysis and adsorption of organic pollutants by the sludge is obtained in segments a to a'.

[0041] In another preferred variant, as shown in Figure 7, wastewater 2 is distributed over the bottom of the sorter S, and (return) sludge 6 is introduced through a pipe having lateral openings at at least three different heights. Through these openings, the sludge comes into contact with the wastewater. Since the high-speed settling sludge particles come into contact with the wastewater at a deeper level in the sorter, a desired distribution of sludge residence time is obtained.

[0042] In another preferred variant schematically shown in Figures 8A and 8B, a desired distribution of sludge residence time in the separator S is obtained by using at least two separator compartments Sa, Sb in which the supply of wastewater 2 and the supply of (return) sludge 6 are alternately performed by the discharge of adjusted sludge, and the desired distribution of sludge residence time in the separator S is obtained by supplying wastewater 2 to the compartment at the bottom of the compartment, the discharge of adjusted sludge can be achieved by applying changes in flow velocity and / or applying mixing, and / or by withdrawing at least a portion of the sludge / wastewater at the bottom level (3a) of the compartment, and optionally by supplying sludge 6 at the liquid level (6b) of the compartment and / or somewhere between the bottom level (6a) and the liquid level.

[0043] With these two sorting compartments Sa and Sb, and the alternating supply of wastewater and (return) sludge, one or more mixers M can be used. This embodiment is shown in Figure 8A. Wastewater 2 is introduced at the bottom level of the compartment. Return sludge 6 is supplied at one or more heights between the bottom level and the liquid level of the compartment. Although Figure 8A only depicts the option of supplying sludge at the bottom, such an option (Figure 8B) can also be applied, divided with respect to 6a and 6b, and optionally supplying sludge further in the middle. During supply, no mixer / propeller is used, and the water / sludge mixture overflows through outlet 3, causing the sludge bed to become layered based on its settling characteristics. The smallest sludge particles move upward with the flow, while heavier, larger particles move against the flow and are in contact with the substrate-containing wastewater for a longer period. Here, adjustment is made by discontinuous changes in upward flow and / or flow velocity. After the desired anaerobic contact time is achieved, the supply continues for the desired period, but the mixer M is now in operation, supplying the sludge / water mixture 3 to the continuous flow-through bioreactor. To maintain the continuous nature of wastewater treatment, at least two compartments are operated alternately to ensure continuous discharge of the adjusted sludge / wastewater 3. Also, as with the variant described above, instead of using the mixer M, larger sludge particles can be transferred to reactor B by using a pump, alkylmedes screw, bubble pump, coarse bubbles, etc.

[0044] The aforementioned variant may be configured and operated without the mixer M. This is shown in Figure 8B. Similar to the aforementioned variant, sludge 6 can be supplied at the bottom level (6a), the liquid level (6b), or somewhere in between, but instead of using a mixer, the compartment may have a sludge / wastewater outlet at at least the bottom level (3a), the liquid level (3b), or / or additionally somewhere in between. During the aforementioned supply and aerobic separator operation, sludge / wastewater is removed from the separator compartment through 3b. After the anaerobic contact time has been achieved, the supply continues for the desired period, but this time sludge / wastewater is removed from the compartment through 3a, so that a mixture 3 containing large sludge particles is supplied to the continuous flow-through bioreactor. In this variant, it is also possible to effectively remove the adjusted sludge / wastewater from the compartment by supplying sludge to the separator compartment through 6b.

[0045] As detailed above and shown in Figures 2 to 8, and all the possible variations described above, continuous supply of sludge to the biological reactor B becomes possible.

[0046] Those skilled in the art will recognize that if the continuous supply of sludge from the sorter S to the bioreactor B is not essential for the operation of the bioreactor, the same advantages of the process according to the present invention can be achieved using only one intermittently operating sorter tank / sorter compartment, without introducing flow rate distinctions (e.g., deflection baffles). This embodiment is shown in Figure 9A. In this preferred variant, the sorter S is initially filled with (return) sludge 6 for a short time. Subsequently, feed 2 is supplied vertically to the sorter S at a low flow rate. During this supply, larger sludge particles concentrate toward the bottom of the sorter, while smaller sludge particles are flushed out, creating a distribution of sludge residence times. During the supply, substrate from the wastewater is taken up by the sludge. Initially, rapidly degradable substrate (such as fatty acids) present in the supplied wastewater is almost completely absorbed by the larger sludge particles at the bottom of the sorter. As a result, this substrate is no longer available to the smaller sludge particles above the sorter. Only when the MO of the larger sludge particles is completely saturated with the substrate and the sludge particles can no longer absorb the substrate does the MO of the sludge particles become available to use the substrate above the separator. This is indicated by a mark in Figure 9A. In the figure, the sludge in marked "zone a" is in contact with the substrate, while the sludge in "zone b" is not. The height of zone a increases over time, which is schematically shown in Figure 9B. The horizontal axis represents time from the wastewater supply, and the vertical axis represents the height of the substrate front (boundary e between zones a and b). As soon as this substrate front reaches the top of the separator, the maximum effective contact time between the sludge and wastewater is reached (time dt in Figure 9B), and the mixer M is started, causing the sludge to flow into reactor B, after which the above steps are repeated.

[0047] For all of the preferred variants described, the returned sludge can also be introduced into the sorting machine intermittently or at different flow rates.

[0048] Naturally, all of the aforementioned preferred variants can also be used in a sludge return line parallel to the purification reactor, using only a portion of the returned sludge. In this case, the proportion of returned sludge processed by the sorting machine S is preferably more than 30 wt%, more preferably more than 50 wt%, and most preferably more than 70 wt%.

[0049] All of the aforementioned preferred modifications are preferably combined with the separation and discharge of the smallest or worst settling sludge particles in the sludge discharge 7. Mechanical or gravity separators can be used, and such separators are usually located in the return sludge of the sorting machine S, but can also be used in parallel with the bioreactor B, or between B and the final settling tank NB. By using such separators in combination with the optimization of the retention and contact time distribution in the sorting machine S, granulation in the continuous purification is further promoted.

[0050] Preferably, the discharge of these minimum and worst settling sludge particles is at least 30 wt%, more preferably at least 40 wt%, and more preferably at least 60 wt%, of the total amount of sludge (excess sludge) discharged from the continuous purification process. Preferably, the average size of the minimum sludge particles separated and discharged is 0.4 mm or less, or more preferably 0.2 mm or less. Doing so increases the proportion of granular sludge.

[0051] As mentioned above, this selective discharge (see also Figure 1) can be performed at various locations in the activated sludge system, such as between the activated sludge reactor B and the secondary sedimentation tank NB, the final sedimentation tank NB, and the return line of the activated sludge system, but it can also be performed in the anaerobic separator S. It is preferable that all embodiments of the separator S also have means for separating and discharging the smallest or worst-case sedimented sludge particles. In one variant, means such as discharge are located at the top of the separator S. For example, Figure 9A shows how selective discharge can be performed at the top of the sludge bed in separator c. The top of this tank contains particularly small-sized sludge, and the smallest particles are separated from the larger sludge particles moving towards the bottom of the tank by being discharged from the top of the tank. Figure 2B shows sludge discharge 7 being performed at the top of section Sb where the concentration of sludge with the smallest size is highest, and Figure 9A shows sludge with the smallest size e being discharged by sludge discharge 7.

[0052] [Detailed description of the present invention] The present invention relates to a method for purifying substrate-containing wastewater in a continuous flow-through aerobic biological purification reactor, wherein at least a portion of the biological sludge (whether or not after a conventional pretreatment step of the received wastewater) is prepared in a separator under anaerobic or anoxic conditions using at least a portion of the substrate-containing wastewater, wherein at least 20 wt% of the sludge in the separator has a residence time in the separator that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the separator, preferably with larger sludge particles in contact with the highest substrate concentration, and thereafter (whether or not after a final additional anaerobic or anoxic step) the thus prepared sludge / water mixture is supplied to an aerobic purification reactor, undergoes (conventional) aerobic purification, and the treated (purified) wastewater after aerobic purification is separated from the sludge by sedimentation, flotation, or mechanical separation.

[0053] In particular, the present invention relates to a method for purifying substrate-containing wastewater in a continuous flow-through aerobic biological purification reactor B, wherein at least a portion of the biological sludge 6 (whether or not it is after a conventional pretreatment step VB of the supplied wastewater) is prepared in a separator S using at least a portion of the substrate-containing wastewater 2 to be treated under anaerobic or anoxic conditions, and at least 20 wt% of the sludge in the separator has a residence time in the separator that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the separator, and thereafter (whether or not it is after an additional anaerobic or anoxic contact time) the thus prepared sludge / water mixture 3 is supplied to the aerobic purification reactor B, undergoes (conventional) aerobic purification, and the treated (purified) wastewater 4 after aerobic treatment is separated from the sludge by sedimentation tank NB, flotation, or mechanical separation, and the sludge (at least a portion of it) separated from the aerobic treated wastewater is returned to the separator as return sludge 6. Preferably, a portion of the sludge containing the worst settling sludge particles can be removed as sludge discharge 7. See Figure 1 here.

[0054] In relation to the present invention, the terms "purify" and "treat" wastewater are used synonymously.

[0055] In the above method, the sludge is separated in a separator under anaerobic or oxygen-free conditions based on the difference in settling rates, so that larger sludge particles (characterized by a higher settling rate) obtain a longer contact time with the wastewater, and so that larger sludge particles come into contact with a higher substrate concentration in the wastewater than smaller sludge particles. This can be achieved, for example, by applying in the separator (i) multiple stages with individual or discontinuous changes in flow velocity, (ii) an increasing flow gradient (i.e., a continuously increasing flow velocity), or a combination of (i) and (ii).

[0056] In one embodiment, the sludge / water mixture in the sorting machine undergoes individual changes in flow velocity and / or flow gradient under anaerobic or oxygen-free conditions. In a particular embodiment, individual changes in flow velocity are achieved by individual changes in the flow direction of the sorting machine and / or by individual changes in the flow rate of the supplied wastewater and / or returned sludge.

[0057] It is advantageous that, starting from conventional activated sludge, granular sludge is generated by the aforementioned method, preferably within 200 days after the start of the method, more preferably within 100 days after the start. As mentioned above, since granular sludge settles considerably faster than sludge flocs, a significantly smaller settling tank can be used and / or a significantly larger amount of sludge can be maintained in the purification process, thus purifying a wider range of wastewater. In this process, granular sludge is obtained in a continuous flow-through wastewater purification process, and a small settling volume or a high upward flow can be used while maintaining effective separation of sludge and treated water. Furthermore, the volume of the anoxic tank or anoxic section within the aerobic treatment reactor between the anaerobic and aerobic zones can be reduced, or such anoxic tank / section may not be necessary, and there may be no need to recycle water / sludge from the aerobic zone to the anoxic and anaerobic zones, yet a wide range of nitrogen compounds from the wastewater can still be removed.

[0058] In one embodiment, the oxygen-free reactor compartment or reactor zone between the anaerobic step (a) and the aerobic step (b) can be eliminated.

[0059] As described above, the present invention is a method for continuous flow-through wastewater purification, wherein wastewater 1 is optionally pretreated in a primary sedimentation tank VB, and the pretreated wastewater 2 is subsequently... (a) In the sorting machine S, a mixture of wastewater and sludge is obtained by contacting the biological sludge 6 under anaerobic conditions, and the sorting machine S controls and / or ensures that at least 20 wt% of the sludge in the sorting machine has a residence time in the sorting machine that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the sorting machine. (b) Next, the flow 3 containing the sludge adjusted in the sorting machine is supplied to the aerobic purification reactor B. (c) The present invention relates to a method wherein sludge is optionally separated from the wastewater (by settling NB, flotation, or mechanical separation) to obtain treated wastewater 5, and the separated sludge (at least a portion thereof) is recycled back to step (a) as return sludge 6 and returned to the sorting machine S, and a portion of the sludge, preferably the portion containing the worst settling sludge particles, can be cleared from the treatment process as flow 7. This sludge clearing 7 can be carried out at different locations or combinations of locations within the treatment process.

[0060] By doing so, the sorter controls the larger sludge particles, which settle at high speed, to be in contact with the concentrated substrate-rich wastewater for a longer period than the smaller sludge particles, which settle at low speed. As a result, the MO of these larger sludge particles can absorb more substrate for a longer period than the smaller sludge particles, which have shorter residence times and are not in contact with the high substrate concentration as much. This provides a competitive advantage in terms of MO growth, which promotes granule growth, and in the subsequent formation and stable maintenance of granular sludge in the continuous flow-through purification process.

[0061] It is preferable that at least 40%, more preferably 50-90%, of the sludge in the sorting machine has a residence time in the sorting machine that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the sorting machine.

[0062] If pretreatment is not required, wastewater flows 1 and 2 are identical and equivalent.

[0063] In one embodiment, it is preferable that at least 40%, more preferably 50-90%, of the sludge in the sorting machine has a residence time in the sorting machine that is at least 40% longer than the hydraulic residence time of the sludge / water mixture in the sorting machine.

[0064] The sorting machine preferably prepares the sludge-wastewater mixture so that the proportion of granular sludge in the aerobic biological purification reactor B is at least 25 wt%, preferably at least 30 wt%, most preferably at least 40 wt%, and particularly at least 50 wt%, and more preferably at least 20 wt% of this granular sludge (i.e., sludge of at least 0.212 mm in size), or more preferably at least 25 wt%, preferably at least 30 wt%, most preferably at least 40 wt%, and particularly at least 50 wt%, of this granular sludge in the aerobic biological purification reactor B has a particle size of at least 0.4 to 1.0 mm.

[0065] In a preferred embodiment, the improved granular sludge size distribution and sludge residence time distribution according to the present invention are achieved by using a sorting machine S that applies individual or discontinuous changes in flow velocity, preferably a sorting machine S that includes different sections (Sa, Sb, etc.) having their own flow velocities, where the flow velocity of the next section is always 25-50% of the flow velocity of the previous section.

[0066] The sorting machine S is an upward-flow reactor in which compartments are arranged concentrically, and includes an internal first compartment Sa and at least one or more further compartments (Sb, Sc, etc.) oriented concentrically around the first compartment Sa, where these compartments are always fluidly connected to the previous compartment at the bottom and top, and a (return) sludge 6 supply section is located below the first compartment S, and each subsequent compartment has a wastewater 2 inlet at the bottom, so that the sludge and wastewater 1 come into contact with each other, thereby more preferably the sorting machine brings vertical flow ("upward flow") to the compartments. Those skilled in the art can select different diameters of compartments to achieve a desired difference in flow velocity between adjacent compartments. In this way, (a1) the mixture is selected by the settling velocity, and a first portion S1 of the sludge containing slow-settling sludge is carried to a second compartment by overflow, and a second portion S2 of the sludge containing fast-settling sludge is collected at the bottom and carried to the second compartment via a bottom connection, preferably the fast-settling sludge S2 in the second compartment returns at a low flow velocity and comes into contact with the wastewater, and the process of separating the fast-settling sludge S3 at the bottom side and the connection with the third compartment from the slow-settling sludge S4 by overflow to the third compartment is repeated. In this way, the contact time between the fast-settling sludge and the wastewater is increased, and the maximal sludge particles receive the highest substrate concentration and preferentially absorb the substrate for the formation of granule MO. Refer to Figure 2A for further explanation.

[0067] In one embodiment, the sorter S is an upward-flow reactor comprising three adjacent, interconnected compartments Sa, Sb, and optionally Sc, with regulated volumes, where the effective volume of compartment Sa is smaller than the effective volume of Sb, and the biological sludge 6 and substrate-containing wastewater 2 to be purified flow continuously from Sa to Sb and from Sb to Sc, with these compartments always fluidly connected to the previous compartment at the bottom and top, with a (return) sludge 6 supply located below the first compartment, and each subsequent compartment having a wastewater 2 inlet to the bottom, so that the sludge and wastewater 1 are in contact with each other, thereby the sorter brings a vertical flow ("upward flow") into the compartments. Refer to Figure 2B for further explanation.

[0068] In the method according to the present invention, changes in the flow rate in the sorting machine are achieved by changing the supply amount of wastewater 2. The inventors have found that fluctuations in the daily wastewater flow rate 2 can further improve the sludge residence time distribution. In particular, during periods of low supply, the best settlingable sludge particles accumulate around the bottom of different sections, resulting in maximum contact with the most concentrated, least diluted wastewater. This further completes the distribution of sludge residence time in the sorting machine.

[0069] In the method according to the present invention, a change in the flow velocity in the sorting machine is achieved by changing the flow rate of the sludge 6.

[0070] In a preferred embodiment, granulation is further promoted not only by creating a distribution of sludge ages in the sorter, but also by increasing the substrate concentration present in the supplied wastewater by providing a suitable external carbon source or by pre-treating the supplied wastewater through processes such as hydrolysis or fermentation, thereby promoting the growth of MOs that granulate. In this way, the proportion of rapidly biodegradable substrates such as fatty acids is increased, preferably by at least 15%, more preferably by at least 25%, of the total substrate concentration. In one embodiment, the substrate concentration is increased by providing an external carbon source, by side flows from a sludge treatment line which is part of a treatment plant in which the biological purification reactor is in use, or by pre-treating the wastewater whole or partially by hydrolysis or fermentation.

[0071] There are no restrictions on the wastewater source. Wastewater to be treated using the method according to the present invention typically contains organic nutrients (organic substances), also referred to in the context of the present invention as substrate-containing wastewater. Typically, the biochemical oxygen demand (BOD) of the influent wastewater is at least 50 mg / l, for example, 100 to 10,000 mg / l. Any type of wastewater, such as sewage or water from industrial production processes, can be treated according to the present invention. Thus, the method according to the present invention can also be called wastewater treatment. Wastewater to be processed according to the present invention can be pretreated before step (a), as is known in the art for primary treatment, but primary treatment is not always necessary for the current process to run efficiently. Typical wastewater pretreatment techniques include one or more of the following: purification, removal of coarse suspended solids, removal of grease, and primary sedimentation.

[0072] In one embodiment, the proportion of rapidly biodegradable fatty acids in the wastewater source is less than 10-15 wt% of the total amount of substrate / nutrients, and / or there is variation in the fatty acid concentration of the supplied wastewater, so that this proportion is less than 10-15 wt% for at least 20% of the time. The inventors have found that low fatty acid concentrations and their fluctuations complicate continuous wastewater treatment based on granular sludge technology, but the use of the sorting machine according to the present invention makes it easier to manage continuous wastewater purification based on granular sludge technology.

[0073] The sorting machine S according to the present invention is part of the anaerobic zone. In a preferred embodiment, the sorting machine S forms the anaerobic zone (only). The conditions of the sorting machine S are called "anaerobic" because no oxygen is added. As mentioned above, the conditions of the sorting machine S may also be oxygen-free. Under oxygen-free conditions, in addition to organic pollutants, nitrogen oxide compounds such as nitrites and nitrates are also present, and MOs that convert these into harmless nitrogen gas can proliferate. Under anaerobic conditions, the concentration of such nitrogen oxide compounds is limited or absent altogether. Under such conditions, MOs that accumulate phosphates can proliferate. Within the anaerobic zone, the wastewater conditions and residence time are such that the sludge granules can absorb organic nutrients from the incoming wastewater. These organic nutrients are typically accumulated by microorganisms in the form of polymers such as poly-β-hydroxybutyrate (PHB). The typical average residence time of the sludge-water mixture in the anaerobic zone of step 1 is 15 minutes to 5 hours, preferably 30 minutes to 2 hours.

[0074] As mentioned in the introduction, granular sludge is defined in the prior art as sludge that does not coagulate during settling and has a size of at least 0.212 mm (typically less than 6 mm), and therefore the SVI after 5 minutes of settling corresponds to the SVI after 30 minutes of settling. Cottony sludge has a smaller size. A small amount of cottony sludge may be present in the wastewater purification system according to the present invention, but the method aims to reduce the proportion of cottony sludge. Since cottony sludge has a shorter residence time in the sorter S, less contact with the substrate in the sorter, and does not reliably come into contact with the substrate with the highest substrate concentration in the sorter, its growth is not promoted, and the proportion of cottony sludge remains small. With the current process, the proportion of cottony sludge with a size of 0.212 mm or less is preferably limited to a maximum of 50% by weight, preferably less than 40% by weight, and more preferably less than 30% by weight. The current process is carried out smoothly using such a limited amount of cottony sludge, and in addition, the amount of cottony sludge can be further reduced by removing sludge, in particular by sludge discharge 7 (excess sludge discharged from the purification system to prevent sludge accumulation due to continuous sludge growth) which has a less rapid settling characteristic, for example by drawing this sludge as far away as possible from the inlet of the secondary settling tank, or by removing the sludge from this separator at a location where the proportion of fast-settling sludge is small, and / or by applying a gravity separator or mechanical separator to the return sludge, or in parallel with the aerobic reactor or separator, and sweeping away the small amount of sludge obtained thereby.

[0075] In relation to the present invention, the terms "high-speed settling sludge" and "heavy sludge" are considered synonymous, as are the terms "slow-speed settling sludge" and "light sludge." The settling rate or settling velocity is determined in the art. A practical measure of the settling rate known in the art is the sludge volume index (SVI). SVI is defined as the volume (ml) occupied by one gram of sludge after a certain settling time. Typical values ​​for the ratio of SVI after 5 minutes of settling (SVI-5) to SVI after 30 minutes of settling (SVI-30) for granular sludge according to the present invention are less than 3, typically 1 to 2.5, and more typically about 1.5, while the SVI-5 / SVI-30 ratio for conventional cottony sludge is greater than 3.

[0076] Considering the presence of microorganisms, the sludge present in the system according to the present invention can also be called "activated sludge." The microorganisms required for the process according to the present invention can be found in the sludge of conventional wastewater treatment plants. The conditions set by the present invention control that these microorganisms remain as part of the granular sludge, so there is no need to separate them.

[0077] The mixture of wastewater and sludge from the sorting machine S is then transferred to an aerobic reactor B, to which oxygen molecules are supplied (aeration) using, for example, an aeration device known in the art. The average residence time of the sludge and water mixture in aerobic reactor B may vary considerably depending, for example, the amount and type of contamination in the incoming wastewater and the desired degree of purification, and is typically 1 to 30 hours, preferably 2 to 20 hours. The average residence time of the sludge also varies considerably depending, for example, the amount and type of contamination in the incoming wastewater and the desired degree of purification, and is typically 3 to 40 days, preferably 5 to 20 days. Aeration of the aerobic zone is performed at a rate such that the concentration of dissolved molecular oxygen in the wastewater of reactor B is preferably at least 0.5 mg / l, more preferably at least 1 mg / l, preferably 5 mg / l or less, and more preferably 10 mg / l or less. Modifying conventional aerobic reactors and their aerobic conditions is not part of the present invention.

[0078] In addition to the aerobic zone or compartment, reactor B may also have zones and compartments where anaerobic conditions are generated, thereby enabling denitrification and further removal of nitrogen compounds from wastewater.

[0079] Subsequently, it is preferable that the biologically purified wastewater be separated from the sludge and water mixture in reactor B. This is usually achieved by sedimentation (secondary sedimentation NB), but can also be achieved by mechanical separation, flotation, filtration, or other methods. Such a sedimentation and separation step, in which the sludge is separated from the treated water, is common in conventional wastewater treatment plants. The presence of granular sludge instead of coagulant sludge allows the sedimentation tank to be much smaller (e.g., about one-quarter the area for the same wastewater inflow) compared to conventional tanks required for the sedimentation of cottony sludge. The water and sludge mixture inflowing into reactor B remains in the sedimentation tank or a similar separator for a sufficient amount of time. Once the sludge is separated from the water, the biologically treated wastewater is clean enough to be discharged into the environment, although for some applications and / or locations, additional further treatment such as filtration or, for example, metal removal may be desirable.

[0080] The water treated according to the present invention, discharged from a clarifier or similar separator, is the main product of the process according to the present invention. Compared to the inflowing wastewater, the purified water is free from organic matter (organic nutrients). The treated water can be discharged into the environment and, if desired, can be further purified or used.

[0081] In the method described above, granular sludge formation naturally occurs, starting with conventional activated sludge, preferably within 200 days after initiation, more preferably within 150 days after initiation, and the sludge is selected so that it always contains the majority of sludge during the purification process. By initially starting the purification process with sludge that already contains at least a portion of granular sludge, the formation of the majority of granular sludge can be accelerated and supported. The proportion of granular sludge in the sludge added at the start of the system is 3 kg / m³. 3 ~Preferably 0.6 kg / m 3It is preferable that the sludge concentration be at least 15% by weight. It is even more preferable to start with sludge that is already more than 50% granular sludge.

[0082] Furthermore, by continuously or intermittently adding a solid or chemical substance to the sludge to which sludge particles can adhere, the formation and stable maintenance of granular sludge can be accelerated and supported, thereby increasing its size or weight. This solid support material preferably has a size of 0.05 to 2.5 mm and a specific gravity equivalent to or greater than that of wastewater. This material may be, for example, granular sludge from another reactor, sieved activated sludge, sorted sand, plastic particles, or other natural or synthetic materials. For example, a solid with a specific gravity of at least 1.05 kg / l is added to the sludge. The MO of the sludge adheres to this substance, increasing the density of the sludge particles and, consequently, the settling rate. A similar effect can be achieved, for example, by providing a liquid chemical substance such as an iron salt, aluminum salt, or calcium salt, so that the salts in the sludge / water mixture react to form a solid.

[0083] The present invention may be applied in parallel with conventional treatments that do not provide or enable the formation of granular sludge. This is shown in Figure 10. Here, purification line L1 is a conventional purification, and the bioreactor comprises one or more compartments or reactors that enable different combinations of aerobic, anaerobic, and aerobic process conditions. In the figure, this is shown as B1, B2, and B3, but there may be more or fewer parts. Purification line L2 is the method according to the present invention. By connecting the discharge-sludge line from L2 to L1, the purification line according to the present invention also has synergistic effects on the operation, sludge characteristics, and MO of the conventional purification line. This is achieved by transferring the sludge (7) entirely or partially to one or more of the bioreactor components (line 8) rather than discharging the sludge (7) from purification line L2 to the sludge treatment. Ultimately, this discharged sludge has better biomass characteristics, with a larger size and simultaneous denitrification capacity than the ordinary sludge of conventional lines, and therefore improves the sludge characteristics and operation of the conventional line. This synergistic effect can be further enhanced by supplying a portion of the return sludge 6 and / or sludge discharge 7 from conventional line L1 to L2 via line 9. In this way, a portion of the sludge from the conventional line also undergoes the action of the sorter S in line L2. As a result of the aforementioned connection of the two purification lines, improved effects and larger sludge particles can be obtained in line L1 without the need to treat all wastewater and sludge with the innovative sorter S, and without retrofitting L1 to the purification according to the present invention. In one embodiment, the method according to the present invention includes the step of supplying waste sludge 7 (as 8) to a conventional treatment, preferably a treatment that does not have means to produce granular sludge. In another embodiment, the method according to the present invention includes the step of supplying a portion of the surplus sludge or return sludge from the conventional purification.

[0084] In another variant, the same synergistic effect can be achieved by following or incorporating the separator according to the present invention into an aerobic granular sludge (AGS) reactor operating as a sequential batch system (SBR), and connecting the separator to a conventional continuous flow-through system, as described above. This is shown in Figure 10. The purification line L3 comprises the separator and the AGS SBR according to the present invention. Sludge discharge (7) from the S-AGS-SBR of L3 is supplied to the conventional line L1 via line 10. Similar to the synergistic coupling described above, a portion of the sludge discharge (7) or return sludge (6) from the conventional line can also be supplied to the separator S (via line 9).

[0085] Based on the above description, the present invention is also characterized by embodiments in which the sorter S is supplied with return sludge and / or a portion of the sludge discharge from another purification line, or by embodiments in which the sorter S is followed by or incorporated into a granular sludge reactor operating on a sequential batch principle. Therefore, it is preferable that the sorter S is fluidly connected to or incorporated into a granular sludge reactor operating on a sequential batch principle.

[0086] Closely related thereto, the present invention also relates to a device for purifying substrate-containing wastewater, comprising a sorter S including an inlet for substrate-containing wastewater 2, an inlet for biological sludge 6, an outlet for a prepared sludge / water mixture 3, and optionally an outlet for a sludge discharge 7, wherein the outlet 3 is fluidly connected to the inlet of a continuous flow-through aerobic biological purification reactor B, which further comprises an inlet for biological sludge 6, an inlet fluidly connected via the outlet of the sorter S, an outlet for treated wastewater 4, and optionally an outlet for a sludge discharge 7. The outlet 4 may be fluidly connected to the inlet of a clarifier NB, and the inlet 2 may be fluidly connected to the outlet of a pretreatment tank VB, and the device is suitable for performing the method according to the present invention. In particular, the sorter S is designed to operate under anaerobic or oxygen-free conditions and includes means for actively ensuring or controlling that larger size and / or higher settling velocity sludge is in contact with the sorter wastewater and more concentrated substrate-containing wastewater for a longer period of time. This can be done, for example, by providing the sorting machine with (i) a number of stages in which the flow velocity changes individually or discontinuously, (ii) an increasing flow gradient (i.e., a continuously increasing flow velocity), or a combination of (i) and (ii).

[0087] In a preferred embodiment, the method or system operates in parallel with one or more other wastewater treatment process lines, and the sorter S receives portions of the biological sludge 6 and biological sludge 9 from these parallel other wastewater treatment process lines, and optionally, portions of the biological sludge 6 are directed to these parallel other wastewater treatment process lines. [Examples]

[0088] As a tool for designing and optimizing treatment plants using the present invention, the inventors have developed a simulation model for calculating the growth, discharge, and size of sludge particles in a continuous flow-through biological treatment plant, depending on the degree of sludge residence time distribution in the sorting machine / anaerobic tank. The model describes the flow of substrate-containing water through the apparatus, the sedimentation and fluidization of granules and flocs, substrate uptake by biomass, granule growth, and the selection (discharge) of flocs and granules.

[0089] To demonstrate the functionality and effects of the present invention under corresponding process conditions, this model was used to facilitate the formation of granular sludge and the progression of biological sludge concentration in a conventional continuous flow-through treatment, including a conventional sorter / anaerobic tank, aeration tank, secondary sedimentation tank, and sludge return to the sorter / anaerobic tank. Process conditions were selected to be representative of a modern activated sludge system. Starting conditions were ensured using conventional cottony, non-granular sludge with a wastewater substrate concentration of 500 mg / l COD (chemical oxygen demand), a specific sludge growth rate of 0.35 kg / kg COD, and a uniform particle size of 100 μm. Furthermore, a sludge load rate of 0.2 kg COD / kg ODS / day, which is generally applicable to this type of system, was ensured. Here, ODS represents the organic dry matter of the activated sludge in the aerobic reactor, which is a measured amount of MO. This sludge load can also be expressed in terms of biological oxygen demand (BOD), which corresponds to approximately 0.1 kg BOD / kg ODS / day in the case of conventional wastewater composition.

[0090] The results over 200 days are shown in Figure 11B. Here, the floc size is less than 200 μm, "small granules" are classified as having a size of 200-400 μm, and "large granules" are classified as having a size of over 800 μm. The figure shows that after about 50 days, the initial 100 μm sludge particles proliferated into small granules, but no further granulation occurred (there were no "large granules"). Also, the total concentration of organic bioactive biomass (MVLSS on the vertical axis) in the reactor remained at approximately 3.2 g ODS / l). The simulation results corresponded very well to the practical experience gained from starting conventional continuous flow-through granular sludge systems, as well as the experimental results of long-term pilot tests using these types of systems conducted by the inventors.

[0091] Next, using the same model with identical parameters and settings, we simulated what sludge concentration and particle size would be obtained if the sorter / anaerobic tank were designed according to the present invention, allowing the largest sludge particles to be in contact with the substrate for longer and more time. The simulation was based on the embodiment shown in Figure 8, but other embodiments would yield similar results.

[0092] The results are shown in Figure 11A. Here again, after about 50 days, sludge containing small granules was formed, and the system's sludge concentration of about 3.2 g ODS / l was equivalent to the sludge concentration in conventional treatment. However, by combining the distribution of sludge residence time in the sorter / anaerobic tank with the resulting high substrate concentration and substrate contact time of large sludge particles, there was no steady state between sludge growth and discharge as in conventional systems. After about 80 days, the increase in small sludge granules grew into large granules. After about 200 days, most of the sludge had become large granules, and as a result of the significantly improved settling characteristics of these large granules, discharge decreased, and the concentration of active biomass in the purification process increased from 3.2 g ODS / l to about 6 g / l.

[0093] Furthermore, a model was used to determine the substrate concentrations at which sludge particles of different sizes came into contact and for how long. The results are shown in Figure 11C. This figure shows the substrate sludge load (kg COD / kg ODS / day) for sludge granules of different diameters (micrometers). In conventional purification processes, sludge is exposed to the same substrate concentration for the same duration, resulting in a sludge load of 0.2 kg / kg ODS / day. However, in the process according to the present invention, a larger distribution occurs, meaning that larger granules are exposed not only for longer periods but also to higher substrate concentrations. As a result, the sludge load of larger sludge particles was significantly higher than that of average sludge, and even higher than that of the smallest particles. This high sludge load allows the largest sludge particles to proliferate faster than smaller sludge particles, resulting in more widespread granulation.

[0094] It should be noted that similar model calculations may be performed for other process conditions such as higher or lower sludge loads, higher or lower substrate concentrations of the wastewater, or other embodiments of conventional purification methods or the method according to the present invention. Similarly, as in the above examples, the results of these calculations clearly demonstrated the effectiveness and main advantages of the present invention. For example, according to the present invention, it is possible to achieve a wider range of granulation in a continuous flow-through purification system, and thus operate the system using more active biomass. Such a high concentration of biomass enables more wastewater to be treated within the same treatment volume or leads to better purified water quality. In addition, due to the good sedimentation behavior of large granules, the secondary sedimentation tank can be significantly reduced in size, or the same secondary sedimentation tank can purify more wastewater. This reduces the construction costs and operating costs for wastewater purification. In particular, the granule size is such that nitrification and denitrification can be carried out simultaneously during aeration, eliminating the need for various circulation flows and separate anoxic compartments / tanks, not only significantly reducing energy consumption but also further reducing construction costs.

Examples

[0095] The advantages of the present invention were also clearly demonstrated in the pilot plant operation. This pilot plant had a series of 6 combined anaerobic compartments (screens S 3 ~S A ~S F ) with a size of 0.075 to 0.15 m, a series of 6 combined anoxic / aerobic reactor compartments (reactors B 3 ~B A ~B F ) each with a size of 1 m, and a clarifier with a size of 0.32 m 3 . The last reactor compartment B FThe system also included a partially submerged manifold for periodic sludge discharge after the settling period, aiming for long retention of good settling sludge. A small amount of return sludge could also be discharged as excess sludge. A positive displacement pump was used for recirculation of the mixed liquid agent (from the aerobic zone to the anaerobic zone) or the return sludge (from the clarifier to the anaerobic separator). The return sludge could be separated between the anaerobic separator and the first aerobic / anaerobic section. The combined aerobic / anaerobic section had independently controllable microbubble aeration and coarse bubble aeration. The sludge was suspended by mechanical agitation in all combined sections. This pilot was used to test various configurations of the flow-through granule activated sludge system.

[0096] The inventors first operated a pilot in a configuration representing the prior art. This prior art was considered to be a multi-stage activated sludge process using a plug-flow anaerobic separator and selective sludge discharge. The configuration was as follows: 1. Sorting tank S A Inflow of wastewater and returned sludge into the sorting tank S, and the subsequent sorting tank S B S C S D S E S F Passage through. The operating volume of each tank is 0.075 m³. 3 That was the case. 2. Reactor B A :Anaerobic 3. Reactor B B-E The system was operated aerobically with a dissolved oxygen (DO) concentration of 2 mg / l. 4. Reactor B F It features an aerobic, immersed manifold for selective sludge discharge, with a sludge settling selection criterion set at 3 m / h. 5. Clarifier

[0097] After the primary clarification stage, urban wastewater was supplied to the pilot configuration. The primary wastewater contained an average chemical oxygen demand (COD) of 425 mg / l, phosphorus (P) of 8.1 mg / l, phosphorus (P) of 6 mg / l, ammonium (N) of 51 mg / l, and total suspended solids (TSS) of 110 mg / l. The inflow rate varied from 250 to 500 l / h, and the sludge return rate from the clarifier to the anaerobic separator varied from 0.5 to 1.0. Reactor B E From B A The flow rate of the oxygen-free recycling was equal to the combined flow rate of the inflow sludge and return sludge. Before the start of the experiment, aerobic granular sludge produced from the Nereda® reactor was planted in the reactor.

[0098] During the experiment, sludge settling characteristics and sludge size distribution were monitored. To distinguish between coagulated sludge and granulated sludge, sludge samples were classified using a 200-micron sieve, and then the dry solid level of the classified portion was measured.

[0099] The experiment was repeated with the same configuration, similar flow, and wastewater composition, but this time, according to the configuration shown in Figure 8B, each was 0.375 m³. 3 Two sorting machines S A S B The following was used. Both sorting tanks were operated in a retrograde cycle. One column received wastewater, and the other received return sludge from the clarifier. Here again, the pilot configuration was inoculated with aerobic granular sludge produced from the Nereda® reactor.

[0100] Figures 12A and 12B plot the sludge volume index and the time course of sieve classifiers in a flow-through pilot-scale configuration after planting aerobic granular sludge, for (a) the conventional configuration and (b) the configuration shown in Figure 8B. As can be seen from Figure 12A, the level of granules in the sludge decreased in both cases, and SVI 30However, within two months, the amount increased from a level typical of granular sludge to a level typical of cottony sludge. Clearly, granular MO was eliminated by flocculant-enhanced MO. Also, the total amount of sludge decreased from approximately 6 g / l TSS to approximately 2.5 g / l TSS. When using the sorting machine according to the present invention, contrary to the experiment described earlier, the amount of granules did not decrease at all, and a granule size of 1 mm was maintained throughout the entire duration of the experiment (more than six months) (Figure 12B). Also, SVI 30 The concentration remained relatively constant, consistent with sludge exhibiting good settling characteristics. In addition, the maintained sludge concentration was approximately 4-5 g / l TSS, which was significantly higher than in experiments using conventional configurations.

Claims

1. A method for purifying substrate-containing wastewater in a continuous flow-through activated sludge aerobic biological purification reactor (B), At least a portion of the biological sludge (6) is prepared in a sorting machine (S) under anaerobic or oxygen-free conditions using at least a portion of the substrate-containing wastewater (2) to be purified. At least 20 wt% of the sludge in the sorting machine (S) has a residence time in the sorting machine that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the sorting machine. Subsequently, the sludge / water mixture (3) prepared in this manner is supplied to the aerobic biological purification reactor (B) and undergoes aerobic treatment (B). The treated wastewater (4) after aerobic treatment is separated from the sludge by sedimentation (NB), flotation, or mechanical separation. A method wherein the sludge (at least a portion thereof) separated from the aerobic treated wastewater is returned to the sorting machine as return sludge (6).

2. The method according to claim 1, wherein in the sorting machine, the sludge (6) containing the wastewater (2) undergoes individual changes in flow velocity and / or a flow velocity gradient under anaerobic or oxygen-free conditions.

3. The method according to claim 2, wherein individual changes in flow velocity are achieved by individual changes in the flow direction of the sorting machine and / or by individual changes in flow rate.

4. The method according to any one of claims 1 to 3, wherein at least 40% of the sludge in the sorting machine has a residence time in the sorting machine that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the sorting machine.

5. The method according to any one of claims 1 to 4, wherein at least 40% of the sludge in the sorting machine has a residence time in the sorting machine that is at least 40% longer than the hydraulic residence time of the sludge / water mixture in the sorting machine.

6. The method according to any one of claims 1 to 5, wherein the sorter prepares the sludge-wastewater mixture such that at least 20% of the sludge in the prepared sludge / water mixture is granular sludge with a minimum granule size of 0.212 mm.

7. The method according to any one of claims 1 to 6, wherein the sorter prepares the sludge-wastewater mixture such that the proportion of granular sludge in the prepared sludge / water mixture is at least 25 wt%, and at least 20 wt% of the granular sludge (i.e., sludge of at least 0.212 mm in size) in the prepared sludge / water mixture has a particle size of at least 0.4 to 1.0 mm.

8. The method according to any one of claims 1 to 7, wherein, in addition to, or instead of, the return sludge (6) from the secondary sedimentation tank (NB), the sorting machine (S) is supplied with sludge received from a mechanical separator or gravity separator arranged to selectively discharge the slowest settling sludge in the biological purification or the return sludge into the sludge treatment line.

9. The method according to any one of claims 1 to 8, wherein the concentration of a rapidly biodegradable substrate, which is a fatty acid, is increased to at least 15% of the total substrate concentration by providing an external carbon source, by a side flow from a sludge treatment line which is part of a treatment plant in which the biological purification reactor is used, or by pre-treating the wastewater in whole or in part by hydrolysis or fermentation.

10. The method according to any one of claims 1 to 9, wherein the sorting machine (S) includes at least two compartments (Sa, Sb) in which wastewater (2) and (returned) sludge (6) are supplied and adjusted sludge is discharged alternately, and a desired distribution of sludge residence time in the sorting machine (S) is obtained by supplying wastewater (2) to the compartments at the bottom of the compartments, where the discharge of the adjusted sludge can be achieved by applying a change in flow velocity and / or by applying mixing, and / or by withdrawing at least a portion of the sludge / wastewater at the bottom level (3a) of the compartments.

11. The method according to claim 10, wherein sludge (6) is supplied at the liquid level (6b) of the compartment (Sa, Sb) and / or somewhere between the bottom level (6a) of the compartment (Sa, Sb) and the liquid level.

12. The method according to claim 10 or 11, wherein the sorting machine (S) operates intermittently.

13. The method according to any one of claims 1 to 12, wherein the change in flow velocity in the sorting machine is achieved by changing the supply flow rate of the wastewater.

14. The method according to any one of claims 1 to 13, wherein the change in flow velocity in the sorting machine is achieved by changing the amount of sludge (6) supplied.

15. The method according to any one of claims 1 to 14, wherein a portion of the return sludge and / or excess sludge generated from another purification line is also supplied to the sorting machine (S).

16. The method according to any one of claims 1 to 15, wherein the sorting machine (S) is followed by or incorporated into a granular sludge reactor operating on a sequential batch principle.

17. The method according to any one of claims 1 to 16, wherein the formation of granular sludge is accelerated and / or its maintenance is supported by adding a carrier material having an average size of 0.05 to 2.5 mm and a relative density or specific gravity equal to or greater than the relative density or specific gravity of the wastewater.

18. The method according to any one of claims 1 to 17, wherein a pretreatment step (VB) of the supplied wastewater (1) is performed to obtain wastewater (2) to be purified.

19. The method according to any one of claims 1 to 18, wherein the prepared sludge / water mixture (3) is supplied to the aerobic biological purification reactor B after an additional anaerobic contact step or an oxygen-free contact step.

20. A system for purifying substrate-containing wastewater, The system includes a sorting machine (S) which has an inlet for substrate-containing wastewater (2), an inlet for biological sludge (6), and an outlet for a prepared sludge / water mixture (3), The outlet is fluid-connected to the inlet of a continuous flow-through aerobic biologically activated sludge reactor (B), the reactor further having an inlet for biological sludge (6), an inlet fluid-connected via the outlet of the sorting machine (S), an outlet for purified wastewater (4), and an outlet for sludge discharge (7), A system suitable for performing the method according to any one of claims 1 to 19.

21. The system according to claim 20, wherein the sorting machine (S) operates under anaerobic or oxygen-free conditions and comprises means for actively providing or controlling that larger sludge and / or higher settling velocity sludge are in contact with the substrate-containing wastewater for a longer period of time in the sorting machine, which is achieved by providing the sorting machine with means for creating (i) a plurality of stages in which the flow velocity changes individually or discontinuously, (ii) an increasing flow velocity gradient, or a combination of (i) and (ii).

22. The system according to claim 20 or 21, wherein the sorting machine includes the outlet for sludge discharge (7).

23. The system according to any one of claims 20 to 22, wherein the outlet of the purified wastewater (4) is fluidly connected to the inlet of the clarifier (NB).

24. The system according to any one of claims 20 to 23, wherein the inlet of the substrate-containing wastewater (2) is fluidly connected to the outlet of the pretreatment tank (VB).

25. The system operates in parallel with one or more other wastewater treatment process lines. The system according to any one of claims 20 to 24, wherein a sorting machine (S) receives a portion of the biological sludge (6) and biological sludge (9) from the other parallel wastewater treatment process lines.

26. The system according to claim 25, wherein a portion of the biological sludge (6) is directed to the other parallel wastewater treatment process lines.

27. The system according to any one of claims 20 to 26, wherein the sorting machine (S) is fluidly connected to or incorporated into a granular sludge reactor operating on a sequential batch principle.

Images