Aerobic biological wastewater treatment in a continuous flow reactor

Abstract

The present invention is a method for the purification of substrate-containing wastewater in a continuous flow-through aerobic biological activated sludge reactor B, which optionally, after a pretreatment step VB of the supplied wastewater (1), at least a part of the biological sludge (6) is adjusted in a selector S under anaerobic or anoxic conditions using at least a part of the substrate-containing wastewater (2) to be purified, the adjustment comprising first accumulating sludge particles having a sedimentation rate of at least 2 m / h, and then contacting the substrate-containing wastewater in the selector S with the sludge particles accumulated with a contact time of at least 10 minutes, the selector S being operated or designed such that the sludge residence time in the selector S is longer than the hydraulic residence time of the sludge / water mixture (3) in the selector while the sludge is being contacted with the substrate-containing wastewater, the sludge / water mixture (3) being fed, optionally after an additional anaerobic or anoxic contact step, to an aerobic purification reactor B, subjected to aerobic treatment B, and the treated wastewater (4) after aerobic treatment being separated from the sludge, optionally by sedimentation, flotation treatment, or mechanical separation in a secondary sedimentation tank NB, the selector receiving sludge (6) (at least a part thereof) separated from the aerobically treated wastewater and / or sludge (6') from the aerobic purification reactor B.

Description

Summary of the Invention

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

[0002] To protect the aquatic environment, the biological treatment of wastewater from residential, urban, and industrial activities is an important activity. A number of biological purification technologies are known, and these can be broadly divided into anaerobic technologies and aerobic technologies. Both technologies use microorganisms, and the microorganisms use the pollutants in the wastewater as a substrate, thereby converting the pollutants into less harmful substances. In anaerobic technologies, microorganisms (MO) reproduce without adding a large amount of oxygen to the mixture of MO and wastewater. MO mainly converts pollutants into methane gas and the growth of MO. Examples of such anaerobic technologies are BioBulk, UASB, EGSB, and anaerobic MBR. The advantage of this class of technologies is that methane gas can be utilized. However, the main drawback is that the wastewater treatment performance is quite limited, and subsequent treatment with aerobic technologies is often required for sufficient protection of the aquatic environment. It should be noted that the present invention presented below is not part of this anaerobic class of purification technologies.

[0003] In aerobic technologies, for example, oxygen is supplied to MO by some means by introducing air through a surface aerator, through a bubble aerator, or by other methods. Aerobic MO mainly converts organic carbon-based pollutants into carbon dioxide and the growth of MO.

[0004] Furthermore, in addition to aerobic MOs, there are aerobic technologies in which the process conditions are set in such a way that MOs capable of removing nutrients such as nitrogen and phosphoric acid from wastewater can also propagate. Such process conditions often include so-called anaerobic and anoxic conditions. Under anoxic 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 propagate. Under so-called anaerobic conditions, the concentration of such nitrogen oxide compounds is limited or they are absent altogether. Under such conditions, for example, MOs capable of storing phosphoric acid, such as those of the PAO (phosphate-accumulating organisms) class, can propagate. It should be noted that the term "anaerobic" for these process conditions is widely used and is similar to that in anaerobic purification technologies, but represents a very different class of MOs and should not be confused with that in the above-mentioned anaerobic purification technologies that mainly produce methane. It should also be noted that there are specific MOs that can convert ammonium containing nitrites into nitrogen gas. This class of MOs is often referred to as anammox (anoxic ammonium oxidizer). This class of MOs cannot propagate in the presence of carbon-based pollutants and cannot remove these important pollutants either. Therefore, technologies using anammox MOs do not belong to aerobic wastewater treatment, but often require components of such aerobic purification technologies as a pretreatment for producing nitrites from ammonium or organic nitrogen pollutants.

[0005] The most commonly used aerobic wastewater purification technology, which has been the most widely applied worldwide until recent years, is the so-called continuous (or flow-through) activated sludge system. The so-called Carrousel technology described in European Patent No. EP0474296 is an example of such an embodiment. MO grows in the form of sludge flocs, which circulate together with the wastewater in the Carrousel purification reactor and are thus exposed to both aerobic and anoxic conditions in this way. In order to enable the growth of PAO MO in the circulating activated sludge, there also exists an embodiment of the Carrousel with an upstream anaerobic reactor. After the removal of contaminants from the wastewater by MO in the activated sludge (AS), the AS is separated from the water by sedimentation, flotation treatment, membrane filtration, or other means, and the AS is returned to aerobic, anoxic, and / or anaerobic process conditions. In order to proceed with the separation of the AS properly and quickly, it is important for the AS to have good sedimentation characteristics. This is why so-called sludge selectors are often used in AS systems, and the recycled AS is thoroughly mixed with the untreated wastewater in order to inhibit the growth of so-called filamentous MOs with low sedimentation characteristics. Such sludge selectors are available in a number of embodiments and can be composed of one or more compartments or reactors, can be constantly well mixed, and can operate with or without aeration. Also, the contact time of the non-aerated type sludge selector can be incorporated or extended by a continuous non-aerated contact tank so as to stimulate the growth of PAO. The characteristics of these sludge selectors with or without built-in or continuous non-aerated contact tanks are that the activated sludge and water are thoroughly mixed and the sludge residence time in the sludge selector is the same as the residence time of the sludge / water mixture. In other words, the sludge retention time (SRT) is the same as the hydraulic retention time (HRT). Another characteristic is to control that all the sludge in the sludge selector has the same SRT, and in the case where there is an unexpectedly limited SRT distribution, this distribution corresponds to sludge particles of different sizes. It should be noted that the present invention presented below is not related to this type of sludge selector where HRT = SRT.

[0006] A new class of aerobic activated sludge systems utilizes granular sludge instead of flocculated activated sludge. Scientifically, aerobic granular sludge is defined as sludge having a size of at least 0.212 mm and typically less than 6 mm, such that coagulation does not occur during sedimentation and subsequently, the sludge volume index (a measure of the sedimentation characteristics of the sludge) after 5 minutes of sedimentation is equivalent to that after 30 minutes of sedimentation. The main advantages are that aerobic granular sludge settles much faster (4 - 40 m / h) than flocculated activated sludge (0.5 - 2 m / h), and when the granules are sufficiently large, the above-mentioned anoxic and anaerobic conditions required for nutrient removal occur; even if the granular sludge is aerated and the aerobic MO in the outer layer of the granules decomposes organic carbon-based pollutants, this enables simultaneous denitrification and phosphate fixation in the deeper part of the granules. Thus, compared to activated sludge systems, little or significantly less circulation and propulsion force is required to expose the sludge to various required conditions, resulting in an energy savings of 20 - 50%. However, this requires that the sludge have a granule size of 0.4 mm, preferably greater than 1 mm (preferably less than 6 mm), depending on the applied aeration conditions; otherwise, no or insufficient denitrification capacity is achieved in the deeper part of 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 hydraulic retention time required in the purification reactor and clarifier is shorter as a result of the rapid sedimentation of the sludge, and on the other hand, the amount of MO is much higher as a result of the good sedimentation characteristics of the granular sludge. For comparison, when an activated sludge system often uses an MO concentration of 3 - 5 g / l, this is 8 - 20 g / l for a granular sludge system.

[0007] The first granule sludge technology that has actually been widely applied in the aerobic purification of wastewater is described in International Publication No. WO2004 / 024638. To achieve the transition from activated sludge to granule sludge and to maintain the granules during the purification process, there are several important process-technical conditions. It is important to expose the granule sludge to an "anaerobic" phase (where anaerobic means "without aeration"; strictly speaking, this phase can also be anoxic (in the presence of nitrates)) so that MO can absorb organic carbon-based pollutants. During aerobic treatment, this absorption is important because MO can consume the carbon-based pollutants that have been specifically absorbed, which is an important condition for achieving granule formation. In addition, this carbon is necessary for converting nitrogen oxide compounds to nitrogen gas in the anoxic and anaerobic parts of the granules. Furthermore, it is important to limit the amount of flocculated activated sludge. After absorption in the aforementioned anaerobic phase, some of the carbon pollutants also remain in the wastewater, which will result in the growth of a limited amount of activated sludge flocs. To create these important process conditions, International Publication No. WO2004 / 024638 uses a purification reactor with a discontinuous wastewater feed, which is a continuous batch reactor (SBR) class reactor. In the first phase, the wastewater is fed into the reactor from the bottom so that the undiluted wastewater comes into contact with the granules that can absorb the organic substances. Subsequently, the supply of wastewater is stopped and the supply of an oxygen-containing gas is started. After sufficient aerobic, anoxic, and anaerobic biological conversions have occurred and the wastewater has been purified to the desired water quality, the sludge with the worst settling characteristics is discharged from the reactor together with the formed flocculated sludge. The separation between the flocs, the poorly settling sludge, and the well-settling sludge is achieved by discharging the sludge only after a certain degree of sludge sedimentation has already occurred and by discharging the sludge from the upper part of the reactor. In the specialized literature, this separation is also referred to as a selection pressure.

[0008] Since the first practical implementation of aerobic granular sludge and its operating methods and modes originally described in International Publication No. WO2004 / 024638, this technology has rapidly replaced the application of activated sludge systems due to its numerous advantages. However, the main drawback of this method and mode is that it is carried out in SBR, while most of the existing treatment plants are based on continuous activated sludge. The conversion from a continuous feed reactor to a discontinuous feed reactor is not easy. Due to the numerous advantages of granular sludge and the aforementioned scientific insights into the strict process conditions required for the formation of granular sludge, many attempts have been made to apply granular sludge to continuous flow-through treatment reactors. For example, International Publication No. WO2017 / 025345 describes a process using a separator to separate a part of the activated sludge from the aeration tank of a continuous activated sludge system into two fractions, namely, a fraction that settles faster and a fraction that settles slower, and mixing the fraction that settles faster with the wastewater and the recycled sludge to be treated in an anaerobic tank.

[0009] U.S. Patent Application Publication No. US2020 / 0002201 describes a continuous activated sludge system that processes a portion of the activated sludge recycled from the final clarifier to the start of the continuous purification process in an "incubator" before circulating it to the start of the continuous activated sludge system. The disclosed treatment method includes the application of anoxic and anaerobic conditions, whereby an additional carbon source is also provided by adding chemicals or fermenting a portion of the sludge from primary sedimentation. In addition, at various locations in the process, a separator is used to selectively discharge the sludge that settles at a lower rate. Similar to International Publication No. WO2004024638, this process provides all the conditions to achieve granulation: there is an anaerobic phase and a selection pressure is imposed by the separator. However, the published results of the pilot tests of this process (IWA Innovation conference on sustainable wastewater treatment and resource recovery, Shanghai (November 2019)) show that this method does not result in extensive granulation: only 30% of all the sludge was found to be larger than 0.212 mm, the scientific lower limit for granules, and more than 90% was smaller than 0.25 mm. The granule sludge fraction large enough to enable the aforementioned simultaneous denitrification, which requires a granule size of at least 0.5 - 1 mm, was found to be negligible. As a result, only a very small portion of the potential advantages of granule sludge purification can be achieved in the continuous activated sludge process.

[0010] A similar process is presented in International Publication No. WO2019 / 195918. Here too, the sludge is circulated from the secondary sedimentation to a separate compartment, a separate reactor, or a series of reactors having anoxic conditions, and then the sludge is mixed with the raw wastewater in yet another compartment, a separate reactor, or a series of reactors that are exposed to anaerobic conditions. International Publication No. WO2019 / 195918 also applies a selection pressure by reducing the sedimented sludge discharged to the sludge processing line. The drawbacks of the above-mentioned US Patent Application Publication No. US2020 / 0002201 are also seen to apply here.

[0011] There is a continuing need to further implement and optimize the method described in International Publication No. WO2004 / 024638 within the state of the art, and to achieve extensive granule sludge formation, for example, in the continuous flow through systems described above.

[0012] By experiments, the inventors have found that, in the context of carousel technology, despite the use of the aforementioned sludge selector, and regardless of whether it is built-in or follows an anoxic tank as in the prior art, by mixing sludge with untreated wastewater in an anaerobic tank, regardless of whether the anoxic phase precedes or not, the continuous system as described above cannot achieve on an industrial scale the conversion of most of the sludge to the desired granule size of at least 0.4 - 1.0 mm and its maintenance. However, in this study, the inventors have demonstrated that there is a correlation between the granule size and the degree of distribution of sludge retention time of individual sludge particles with different sedimentation characteristics or sizes, as well as the exposure level to readily biodegradable organic substrate (rbCOD) in an anoxic or anaerobic contact tank or selector. Subsequently, the inventors have used this surprising insight to develop an improved method and device aspect of a continuous feed type flow-through aerobic biological purification reactor based on International Publication Nos. WO2004 / 024638 and WO2017 / 025345, and by utilizing this sludge retention time and rbCOD-exposure distribution, it is possible to convert normal activated sludge into sludge with a high granule formation level, thereby for the first time actually corresponding to the advantages that could only be achieved in the granule sludge technology using SBR before.

[0013] In fact, according to the present inventors, this can be achieved by using the selector under anaerobic or anoxic conditions prior to aerobic purification, which actively provides or controls for sludge having a larger size and / or higher sedimentation degree in the selector to contact the substrate-containing wastewater for a longer time (i.e., longer than sludge having a smaller size and / or lower sedimentation degree). This can be done, for example, in the selector by applying (i) multiple phases with individual or discontinuous changes in the flow rate, (ii) a gradually increasing flow gradient (i.e., a continuously increasing flow rate), or a combination of (i) and (ii). By any of these methods, a distribution of sedimentation degrees is achieved (allowing fractions with lower and higher sedimentation degrees), and at the same time, the contact time and substrate concentration of the large granules in contact with the wastewater increase. This is an improvement over the process in International Publication No. WO2017 / 025345. The function of the selector is to enable a residence time longer than the hydraulic residence time of the conditioned sludge / water mixture in at least a substantial portion of the larger sludge granules, and preferably to expose the larger sludge particles to a higher substrate concentration. For this purpose, mode (i) with individual changes in the flow rate is preferred. This can be achieved more advantageously in (a) a continuous form by providing fluctuations in the flow in the flow direction of the selector at a constant water / sludge flow rate, and / or (b) a semi-batch process in which the fluctuations in the flow rate of the selector are achieved by fluctuations in the water / sludge flow rate. The different modes (i)(a), (i)(b), and (ii) are described in more detail in the detailed description and the drawings.

[0014] The inventors have also found that it is advantageous to first accumulate (i.e., concentrate) sludge particles having a sedimentation rate of at least 2 m / h, preferably at least 2.5 m / h, more preferably at least 3 m / h, preferably in the selector S. However, it has also been found that this accumulation step may also be carried out in a separate tank upstream of the selector. The accumulation of these rapidly sedimenting sludge particles can be achieved by adjusting the feed flow rate of the sludge in an upward flow or upflow configuration such that the rapidly sedimenting sludge is concentrated at the bottom of the tank or selector. After accumulation, the substrate-containing wastewater is contacted with the sludge particles accumulated in the selector for a contact time of at least 10 minutes, and the selector S is operated or designed such that the sludge residence time in the selector S is longer than the hydraulic residence time of the sludge / water mixture in the selector. For convenience, the contact time is between 10 and 120 minutes, preferably between 20 and 90 minutes. Such an initial accumulation step stimulates the growth of rapidly sedimenting sludge in the selector.

[0015] Preferably, the sludge is saturated with the substrate from the substrate-containing wastewater to such an extent that at least 60%, preferably at least 75%, more preferably at least 80% of the biologically degradable substrate (rbCOD) in the wastewater is removed from the wastewater (i.e., adsorbed by the accumulated sludge). The inventors have also found that it is advantageous to limit the contact time between the substrate-containing wastewater and the accumulated sludge such that, preferably, most of the substrate is adsorbed by the sludge when the rbCOD level has reached a steady state.

[0016] In an advantageous wastewater treatment using aerobic granular sludge technology, the present invention relates in particular to a method for the purification of substrate-containing wastewater in a continuous flow-through aerobic biological activated sludge reactor, optionally after a pretreatment step VB of the supplied wastewater 1, at least a part of the biological sludge is adjusted in a selector under anaerobic or anoxic conditions using at least a part of the substrate-containing wastewater to be purified (regardless of whether it is after a conventional pretreatment step of the received wastewater), the adjustment first involves accumulating sludge particles having a sedimentation rate of at least 2 m / h, preferably at least 2.5 m / h, more preferably at least 3 m / h, and bringing the substrate-containing wastewater into contact with the accumulated sludge particles in the selector S for a contact time of at least 10 minutes, the selector S being operated or designed such that the sludge residence time in the selector S is longer than the hydraulic residence time of the sludge / water mixture in the selector while the sludge is in contact with the substrate-containing wastewater, and while the accumulated sludge is in contact with the substrate-containing wastewater, preferably at least 20% by weight of the sludge in the selector has a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector, and preferably larger sludge particles are in contact with the highest substrate concentration, Subsequently, the sludge / water mixture exiting the selector (regardless of whether it is after an accidental additional anaerobic or anoxic step) is fed to an aerobic purification reactor and subjected to (conventional) aerobic purification, The treated (purified) wastewater after aerobic purification is separated from the sludge, Relates to a method.

[0017] By doing so, sludge particles having a larger size and / or a faster sedimentation characteristic have a longer contact time with the more concentrated substrate-containing wastewater than sludge particles having a smaller size or a lower sedimentation characteristic. By using a selector, a conditioned sludge / water mixture (regardless of whether after an accidental additional anaerobic or anoxic process) is fed to an aerobic purification reactor, where at least 20% by weight of the sludge contains granular sludge. Preferably, the proportion of granular sludge is at least 25% by weight, preferably at least 30% by weight, most preferably at least 40% by weight, in particular at least 50% by weight, and preferably at least 20% by weight of this granular sludge (i.e., sludge having a size of at least 0.212 mm), or more preferably at least 25% by weight, preferably at least 30% by weight, most preferably at least 40% by weight, in particular at least 50% by weight of this granular sludge in the aerobic biological purification reactor B will have a particle size of at least 0.4 - 1.0 mm.

[0018] The sludge separated from the aerobically treated wastewater can be returned to the selector (as return sludge 6). This return establishes the continuous nature of the wastewater treatment and ensures that an effective granular sludge size distribution is formed and maintained. Similarly, or in combination with receiving return sludge 6, during accumulation, the selector can also receive sludge 6' from the biological reactor B. In a preferred embodiment, sludge 6' is fed to the selector, while the (return) sludge 6 from the aerobic treatment is fed to reactor B. In other words, in the method described above, the sludge is treated under anaerobic or anoxic conditions in the selector such that the larger sludge particles have more contact with a higher substrate concentration than the smaller sludge particles in the selector, while the larger sludge particles in the biological reactor B have a longer contact time with the substrate-containing wastewater than the smaller sludge particles. In fact, the substrate concentrate varies significantly due to fluctuations in the wastewater composition and uptake by the MO in the selector. Preferably, at least 10% by weight of the largest sludge particles are in contact with the highest substrate concentration in the selector 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% by weight of the smallest sludge particles are in contact.

[0019] The aforementioned improved sedimentation degree distribution in the context of the present invention, as well as the increase in both the contact time between the larger granules and the wastewater and the substrate contact concentration, and its related features, are achieved by using a selector, preferably within 200 days, more preferably within 150 days, after the start of operation of the method. As shown in Figure 11A, without using a selector, these goals are not achieved after the start-up phase.

[0020] In one aspect, the sludge / water mixture in the selector is subjected to individual changes in flow rate and / or flow gradient under anaerobic or anoxic conditions. In a particular aspect, the individual change in flow rate is achieved by individual variations in the flow within the flow direction of the selector and / or individual variations in the flow rate of the supplied wastewater and / or return sludge.

[0021] The term "individual change" in the context of the present invention refers to a (distinguishable) discontinuous change in flow rate.

[0022] In certain embodiments, the selector has a first step of separating, under anaerobic or anoxic conditions, a portion of the sludge into a faster-settling portion and a slower-settling portion, selecting a mixture of the wastewater and the faster-settling portion or the slower-settling portion, and separating this mixture again, in at least a second subsequent step, in the selector into a faster-settling portion and a slower-settling portion. To perform the separation in different steps of the selector, a selection based on the sedimentation degree is preferably applied at any point in an upflow column, and the upflow velocity of the wastewater through different steps of the selector can be adjusted individually and independently as a parameter. By doing so, a discontinuous or individual change in the flow velocity is achieved. This can be achieved, for example, using an upflow column having concentrically arranged compartments that together form the selector. The upflow velocity in each step of the selector is preferably in the range of 1 to 25 m / h. Preferably, the upflow velocity in each step of the selector is lower than that in the previous step, and preferably, in each case, is 25 to 50% of the upflow velocity in the previous step. Preferably, the selector further separates the faster-settling portion or the slower-settling portion obtained from the second step into a faster-settling portion or a slower-settling portion, and then has at least a third step of feeding the sludge-treated wastewater stream and the sludge to a conventional purification reactor and returning the remaining portion to a previous step of the selector. This third step is preferred to avoid the accumulation of sludge where too rapid sedimentation occurs. This multiplicity of sludge separation steps based on the variation of the sedimentation rate / flow rate in the anaerobic selector preferably results in at least 20% of the sludge in the selector having a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector. Also, the goal is achieved that at least 10% by weight of the largest sludge particles are in contact in the selector for at least 20% longer than the average contact time of the sludge and with the highest substrate concentration, and this substrate concentration is at least 50% higher than the substrate concentration with which 15% by weight of the smallest sludge particles are in contact.Such an embodiment is schematically shown in FIG. 2.

[0023] In another embodiment, the selector is a semi-batch process in which sludge is contacted with wastewater in a reactor under anaerobic or anoxic conditions and the feed amount varies.

[0024] In another specific embodiment, the selector performs separation using a gradient (increase or decrease) in flow rate, resulting in continuous separation of downstream sludge based on the degree of sedimentation by the selector such that the sludge residence time in the selector increases with an increase in sedimentation rate. To achieve the goal, the gradient can be adjusted as appropriate. Such an embodiment is schematically shown in FIGS. 3-6. In these cases, a continuous increase in flow rate is provided.

[0025] In each of these embodiments, particles having a sedimentation rate of at least 2 m / h, preferably at least 2.5 m / h, more preferably at least 3 m / h are first accumulated and then contacted with the substrate-containing wastewater. The sludge is contacted with the substrate-containing wastewater in the selector, and in the selector, the sludge residence time during this contact is longer than the hydraulic residence time; preferably, at least 20% by weight of the sludge in the selector has a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector. Preferably, the proportion of granular sludge (sludge having a size of at least 0.212 mm) in the aerobic biological purification reactor B is further at least 25% by weight, preferably at least 30% by weight, most preferably at least 40% by weight, in particular at least 50% by weight; preferably, at least 20% by weight of this granular sludge (i.e., sludge having a size of at least 0.212 mm), or more preferably at least 25% by weight of this granular sludge, preferably at least 30% by weight, most preferably at least 40% by weight, in particular at least 50% by weight has a particle size of at least 0.4 - 1.0 mm. In addition, preferably, the larger sludge particles in the selector have more contact with a higher substrate concentration than the smaller sludge particles. A person skilled in the art can adjust the feed rate and flow rate parameters to achieve these goals.

[0026] In any of these embodiments, deposition due to sludge accumulation in the selector can be prevented by periodically increasing the adjustable time, degree of mixing or flow rate to direct the more rapidly settling sludge also to the downstream aerobic reactor. Further, in any of these embodiments, the proportion of sludge flocs can be further reduced by withdrawing at least a portion of the wasted excess sludge from the position within the selector where the proportion of the sludge particles that settle worst is maximum. Preferably, this mixing occurs at a frequency of not more than twice per hour, more preferably not more than once per hour, even more preferably not more than once per four hours. The duration of this mixing depends on several factors including the hydraulic retention time and is preferably at least 5 minutes, more preferably at least 15 - 30 minutes.

[0027] The present invention enables the maintenance and formation of granular sludge in any type of through-flow purification reactor comprising a purification reactor in which the sludge comprises a mixture of biological sludge and a biofilm carrier and / or a growth body and / or a ballast material. Such carriers / bodies / materials are used for the purpose of improving sludge sedimentation in some types of reactors and utilize natural, organic, inorganic, or blend materials that are targeted to float within the sludge, form a biofilm on the biological sludge, or aggregate therewith. Thus, in the context of the present invention, reactor B may comprise a mixture of biological sludge and a floating biofilm carrier. Description of Processes and Embodiments The following presents various possible working examples and aspects of the present invention, all of which aim to achieve granulation through an improved distribution of sludge retention time as described above. Those skilled in the art will recognize that a significant distribution in sludge retention time is achieved, and that this distribution, in combination with contacting the sludge with untreated wastewater or a contaminated sidestream in such a manner as to expose the largest sludge particles to long-term contact and higher substrate contact concentrations, is common to the methods and aspects described. Also, those skilled in the art will recognize that the methods described do not exclude variations, alternatives, and other aspects that achieve the same effect, and that such aspects and similar methods are part of the same invention. Each of the following aspects also includes the initial accumulation or concentration and subsequent saturation steps as described above.

Brief Description of the Drawings

[0028]

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[0029] Figure 1A shows the basic principle of the improved continuous flow-through biological purification according to the present invention. The wastewater 1, if desired, is first pretreated in the primary sedimentation tank VB and then fed through 2 to the selector S, where it is mixed with the sludge 6. From the selector S, the wastewater / sludge mixture flows into the biological activated sludge treatment reactor B. Thereafter, the sludge from the purified wastewater / sludge mixture 4 is preferably separated from the treated wastewater in the secondary sedimentation tank NB as 5 and at least partially (as 6) returned to the selector. Optionally, the selector receives at least a part of the sludge 6' from the reactor B (Figure 1B), while at least a part of the sludge 6 separated in the sedimentation tank NB is returned to the reactor B. A part of the sludge growing during the purification process is discharged from the process. This excess sludge discharge 7 can occur at different process positions or combinations of positions. The accumulation is realized in the selector in both Figures 1A and 1B, but alternatively, this accumulation step may also be carried out in a separate tank or device preceding the selector S.

[0030] Those skilled in the art will recognize that the pretreatment VB can have various forms, such as, but not limited to, screens, sieves, filters, cyclones, gravity sedimentation tanks, lamella sedimentation tanks, flotation treatment devices, etc. The biological purification reactor B can be any conventional form of a continuous flow-through activated sludge reactor, including, but not limited to, oxidation ditches, plug flow, CSTR, Bardenpho, UCT, etc. Such biological purification reactors usually also have compartments or sub-reactors where aerobic, anoxic, and anaerobic conditions are maintained.

[0031] In the context of the present invention, stream 6 is represented interchangeably with biological sludge, sludge, and return sludge. Sludge stream 6' is specifically the sludge fed from reactor B to selector S; reference is made to FIG. 1B. In FIGS. 2 to 10, stream 6 is to be understood as representing stream 6 and / or 6'. As will be detailed later in FIG. 10, in the method according to the present invention, at least a part of the return sludge may originate from conventional wastewater treatment.

[0032] In this embodiment, the desired accumulation and sludge residence time distribution are achieved by variations in the flow in the flow direction. The selector S is preferably a compartmentalized upflow reactor having concentrically oriented compartments as shown in cross-section in Figure 2A, where the effective volume of compartment Sa is smaller than that of Sb and also smaller than that of Sc. In an alternative form (Figure 2B), the selector is applied to three adjacent connected compartments Sa, Sb, and possibly Sc with adjustable volumes, where the effective volume of compartment Sa is smaller than that of Sb. In either Figure 2A or, similarly, 2B, it is also possible to operate with only compartments Sa and Sb. The sludge 6 or 6' is introduced at the bottom level of compartment Sa, where the sludge is brought into contact with at least a portion of the waste water 2. The remaining portion of the waste water 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 as a result of the sludge residence time determined by the individual sedimentation characteristics of the individual sludge particles. Particles having sedimentation characteristics (sedimentation velocity) much lower than the vertical flow velocity exit compartment a with the upward flow and do not remain in this compartment longer than the residence time of the water in this compartment. However, sludge particles having sedimentation characteristics higher than the liquid velocity remain in this compartment longer than the water, and the sludge particles that sediment most quickly accumulate at the bottom of compartment Sa and flow from there into compartment Sb. An important MO for the formation of granular sludge is that, due to contact with nutrient-rich water and anaerobic or anoxic conditions, it can preferentially take up substrates, and sludge particles with the best sedimentation characteristics thus gain the advantages of biological selection for growth into granular sludge and remaining as granular sludge.

[0033] The sludge particles then enter from compartment Sa to compartment Sb through the overflow or underflow, depending on their sedimentation degree. 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 importantly, the sludge with the best sedimentation characteristics will have a longer contact time and be exposed to a more concentrated wastewater. As a result, particles with a sedimentation rate equivalent to the liquid velocity will remain in the compartment for a length similar to the liquid and contact the less diluted wastewater at the bottom of the compartment for a relatively short period. The faster-settling portion can remain significantly longer at the bottom of compartment Sb together with the best-settling particles from the bottom of compartment a and can take up additional substrate. A similar effect occurs in compartment Sc, which is fed from compartment Sb through the bottom and overflow. Here too, the individual sludge particles that settle more rapidly contact the most concentrated wastewater for the longest time. Naturally, the selector can be extended using additional compartments (Sd, Se...) according to the same principle.

[0034] To prevent the accumulation of sludge particles that settle too rapidly in the last compartment (compartment Sc in Figures 2A and 2B), this compartment is preferably mixed continuously or intermittently with mixer M. This mixing can be achieved not only by using a mechanical stirring device or propulsive force, but also by introducing gas or sizing the rear compartments in such a way that the resulting vertical liquid flow rate is greater than that in compartment a. Despite the fact that this gas may be oxygen or an oxygen-containing gas, the selector is considered an anaerobic or anoxic reactor because the gas in the last compartment only reduces the effective anaerobic contact time of the selector to a certain extent.

[0035] The size of the compartments and the resulting velocity are selected such that the aforementioned targeted sludge accumulation level and sludge residence time distribution occur.

[0036] In the schematic diagram of FIG. 2, in addition to compartment Sa, two further compartments Sb and Sc are also shown. Based on the information provided herein, one of ordinary skill in the art will recognize that at least one further compartment Sb is required to implement the present invention, but that more further compartments (Sb, Sc, Sd, Se...) can also be used to further optimize performance and operational robustness. Increasing the number of further compartments also increases the possibility of further increasing and controlling the sludge residence time distribution. This also applies to the method of compartmentalization and how the required flow pattern and mixing are achieved in this associated compartment. For example, a rectangular tank is preferably designed to have compartment Sa and only one further compartment Sb. Optionally, the overflow from a further compartment is transferred via a conduit to the bottom of a further (preferably adjacent) compartment.

[0037] It should be noted that the inflow of wastewater 2 may also occur at the bottom of the compartment, and the supply of return sludge 6 and / or sludge 6' may occur at the liquid level of the compartment. In this case, the dividing wall between the compartments need not have an opening between the compartments at the bottom. This is shown only for compartment Sa in FIG. 2C. The liquid velocity of wastewater 2 in compartment Sa is selected such that sludge particles 6 flow out into compartment Sb. Sludge particles having a higher settling velocity remain in this compartment Sa longer than particles having a lower settling degree and are then pushed out by the upward flowing wastewater. In this way, the desired contact time distribution and substrate contact concentration are also achieved. As shown in FIG. 2A, several compartments having a wastewater feed at the bottom may be in series with each other.

[0038] Figure 3 shows another preferred variant, where the selector S is designed with an inclined floor v, whereby the liquid velocity increases with the flow. The waste water 2, as well as the (returned) sludge 6 and / or 6' are in close contact with each other on the inlet side, and the waste water is preferably distributed uniformly over the entire bottom or this is optionally achieved by the mixer M. The water / sludge mixture then flows towards the right (in the direction of the inclined floor v), whereby the liquid velocity steadily increases. The sludge particles that settle fastest can concentrate around the bottom at the start of the selector and then move from the inclined floor v to the start of the selector as the flow velocity increases. The sludge particles that do not settle as rapidly will have a shorter residence time in the selector through 3. Thus, the desired sludge residence time distribution is obtained.

[0039] One skilled in the art would recognize that this preferred variation may also be incorporated and used in a circulating or plug - flow activated sludge system, as illustrated in FIGS. 4A, 4B, and 4C. FIGS. 4B and 4C are side views, and FIG. 4A is a top view. FIG. 4B shows how the preferred variation of FIG. 3 can be implemented by providing an ascending elevation or a deflecting baffle in segment a - a' of the circulating activated sludge system. This deflecting baffle increases the flow velocity on the baffle such that sludge particles having a sufficiently high settling velocity (i.e., a settling velocity higher than the flow velocity) either flow upstream of the deflecting baffle or at least flow downstream at a lower velocity, and thus will contact the wastewater entering in front of or at the start of the deflecting baffle for a longer period. Periodically, the mixer or impeller is operated for a certain period of time. Depending on the priority, the (returned) sludge 6 and / or sludge 6' can be supplied immediately before (FIG. 4b) or after (FIG. 6b, described below) the baffle, or at any other location, for example, through an existing returned sludge inlet. In this manner, it is important to obtain a sufficient anaerobic time in segment a - a' for the hydrolysis and adsorption of organic contaminants by the sludge. FIG. 4C illustrates how this is achieved by the slope of the concave bottom of segment a - a' in the flow direction. Naturally, this can be similarly applied in the segments of the plug - flow system.

[0040] Similar to the aforementioned preferred variation, a further distribution of the sludge retention time is preferably achieved by the daily variation in wastewater flow rate, and a mixer or propeller can be operated periodically to prevent the accumulation of the most favorably settling sludge particles in the selector.

[0041] In another preferred variant, the sludge residence time distribution in a circulation or plug flow system is obtained by applying a partial widening of the channel width, resulting in fluctuations in the liquid velocity and sedimentation of the most favorably settling sludge particles to the bottom. See FIG. 5. This is an intermediate form between a discontinuous fluctuation in the flow rate and a continuous flow gradient.

[0042] Regarding the installation of the selector even in an existing situation, in practice, it may be structurally difficult or not cost-effective to apply the aforementioned preferred variants. In that case, the preferred variant shown in FIG. 6 is preferred. The operation is the same as that of FIGS. 4a or 4b, but here, an increase in the liquid velocity is caused by arranging the deflection baffle d before the wastewater and the returned sludge enter. Due to the reduction in the flow velocity immediately after this baffle, larger granules will sediment here to the bottom and come into contact with the feed. Similar to the aforementioned incorporation, in this variant, it is important to obtain a sufficient anaerobic time in segments a - a' for the hydrolysis and adsorption of organic pollutants by the sludge.

[0043] In another preferred variant, as shown in FIG. 7, the wastewater 2 is distributed to the bottom of the selector S, and the (returned) sludge 6 and / or sludge 6' are introduced via a pipe having lateral openings at at least three different heights. Through these openings, the sludge comes into contact with the wastewater. Since the more rapidly settling sludge particles will come into contact with the wastewater at a deeper position within the selector, the desired sludge residence time distribution is obtained.

[0044] In another preferred variant, as schematically represented in FIGS. 8A and 8B, the desired accumulation and sludge residence time distribution in the selector S is obtained by using at least two selector compartments Sa and Sb in which the feed of wastewater 2 as well as sludge 6 and / or sludge 6' occurs alternately with the discharge of the conditioned sludge, the desired sedimentation degree of the accumulated sludge and the sludge residence time distribution in the selector S are obtained by feeding the wastewater 2 to the compartment at the bottom of the compartment, the discharge of the conditioned sludge can be achieved by applying a variation of the flow rate and / or by applying mixing, and / or by withdrawing at least a part of the sludge / wastewater at the bottom level of the compartment (3a), while optionally providing the sludge 6 and / or 6' at the liquid level of the compartment (6b) and / or at a location between the bottom level and the liquid level of the compartment (6a).

[0045] These two selector compartments Sa and Sb, which alternately supply the wastewater and the sludge, can be used in combination with a mixer M. This embodiment is shown in FIG. 8A. The wastewater 2 is introduced at the bottom level of the compartment. The returned sludge 6 and / or sludge 6' is supplied at one or more heights between the bottom level and the liquid level of the compartment. In FIG. 8A, only the option of supplying the sludge at the bottom is depicted, but this option of splitting with respect to 6a and 6b and optionally supplying additional sludge at an intermediate point (FIG. 8B) can also be applied. During accumulation, the selector is provided with sludge 6 and / or 6' at a rate of at least 2 m per hour per square meter of the cross-sectional area of the selector without using a mixer / propeller, with the flow rate 3Feed at a flow rate such that it becomes wastewater. The water / sludge mixture overflows through outlet 3, and sludge particles with a sedimentation degree exceeding 2 m / h accumulate. After this accumulation, the feed of wastewater 2 starts, and during this feed phase, the mixer / propeller is not used. Due to the feed of wastewater, the sludge bed becomes layered based on sedimentation characteristics. The smallest sludge particles move upward with the flow, while the heavier and larger particles move against it and have a longer contact with the substrate-containing wastewater. The adjustment here is caused by the discontinuous variation of the upward flow and / or the flow rate. After the desired anaerobic contact time is achieved, the feed of either wastewater or sludge continues for the desired period, where the mixer M is in operation, and as a result, the sludge / water mixture 3 is fed into the continuous flow-through biological reactor. To maintain the continuous characteristics of wastewater treatment, at least two compartments are operated alternately, thereby ensuring a continuous inflow of wastewater into the selector. Also, similar to the above-described variations, instead of using the mixer M, the transport of larger sludge particles to reactor B can also be achieved by using pumps, Archimedes screws, air lifts, coarse bubbles, etc.

[0046] The foregoing variations can also be configured and operated without using the mixer M. This is shown in FIG. 8B. Similar to the foregoing variations, the sludge 6 and / or the sludge 6' can be fed at any of the bottom level (6a) or the liquid level (6b) of the compartment, or at a location therebetween. Instead of using a mixer, the compartment may be equipped with at least one sludge / wastewater outlet at the bottom level (3a) and the liquid level (3b) of the compartment and alternatively or additionally at a location therebetween. During the foregoing accumulated sludge feed (introducing sludge at height 6a, 6b, or therebetween) and preferably during saturation, the sludge / wastewater is removed from the selector compartment through 3b. After the anaerobic contact time is achieved, the feed of either wastewater or sludge is continued for a desired period, where the sludge / wastewater is removed from the compartment through 3a, such that a mixture 3 containing larger sludge particles is fed to the continuous flow-through biological reactor. In this variation, removing the conditioned sludge / wastewater from the compartment can also be effectively achieved by feeding sludge through 6b to the selector compartment.

[0047] The advantage of the alternately operating mode is that the feed of the substrate-containing wastewater can be easily stopped when the accumulated sludge is preferably saturated to the extent described above. The degree or rate of saturation can be tracked, for example, by monitoring the substrate or rbCOD concentration at the outlet 3 of the reactor or at the top of the sludge / water mixture in the selector; the feed of the wastewater can be stopped when the measurement shows that no significant further adsorption of the biologically degradable substrate (rbCOD) is occurring. Alternatively, this can be achieved by measuring another parameter that changes with conductivity, pH, VFA concentration, BOD concentration, P concentration, dissipation, color, or adsorption of the substrate. Such measurements can also be used in the other foregoing modes to adjust the flow conditions such that the amount of accumulated sludge can adsorb the biologically degradable substrate in the fed wastewater.

[0048] With the embodiments shown in FIGS. 2-8, as detailed above, and all possible variations thereof described above, continuous feeding of sludge to the biological reactor B is possible.

[0049] One skilled in the art will recognize that if continuous feeding of sludge from the selector S to the biological reactor B is not essential for the operation of the biological reactor, the same advantages of the process according to the invention can be achieved using only one intermittently operating selector tank / compartment without providing a flow differentiation (e.g., a deflection baffle). This embodiment is shown in FIG. 9A. In this preferred variation, first, (returned) sludge 6 and / or 6' is fed to the selector S at a flow rate of 2 m per square meter of the cross-sectional area of the selector per hour 3Fill at a flow rate such that the above wastewater is obtained. In this feed, sludge particles that settle sufficiently fast accumulate in the selector, while the others flow out from 3. Thereafter, feed 2 is fed into selector S vertically, during which the sludge particles that settle faster in the accumulated sludge concentrate towards the bottom of the selector and are exposed to the maximum substrate concentration of the wastewater. During the feeding, the substrate from the wastewater is taken up by the sludge. First, the readily biodegradable substrate (e.g., fatty acids) present in the fed wastewater is almost completely absorbed by the larger sludge particles accumulated at the bottom of the selector. As a result, this substrate is no longer available to the smaller sludge particles located at a higher position within the selector. The MO within the larger sludge particles is completely saturated with the substrate, and the substrate becomes available to the MO within the sludge particles at a higher position within the selector only when the sludge particles can no longer absorb the substrate. This is indicated by markings in Figure 9A. The sludge in the marked "zone a" in the figure is in contact with the substrate, while the sludge in "zone b" is not. The height of zone a increases with time. This is schematically shown in Figure 9B. The horizontal axis is the elapsed time from the feed of the wastewater, and the vertical axis indicates the height of the substrate front line (the boundary e between zones a and b). Immediately when this substrate front line reaches the top of the selector, the maximum effective contact time between the sludge and the wastewater is reached (time dt in Figure 9B), and mixer M is started, whereby the sludge is flowed into reactor B, and thereafter the above-described process is repeated.

[0050] For all the mentioned preferred variations, the (return) sludge 6 and / or 6' can also be introduced into the selector intermittently or at different flow rates.

[0051] Of course, all the above-mentioned preferred variations can also be used in the sludge return line in parallel with the purification reactor using only a part of the return sludge. In this case, the proportion of the return sludge treated in selector S is preferably more than 30% by weight, more preferably more than 50% by weight, and most preferably more than 70% by weight.

[0052] All of the aforementioned preferred variants are preferably combined, in the sludge discharge 7, with the separation and discharge of the smallest sludge particles or the sludge particles that settle least well. Mechanical or gravity separators can be used, such separators usually being arranged in the return sludge in the selector S, but they can also be used in parallel with the biological reactor B or between B and the final sedimentation tank NB. Granulation in continuous purification is further stimulated by using such a separator in combination with the optimization of the residence time distribution and the contact time distribution in the selector S.

[0053] Preferably, this sludge discharge of the smallest sludge particles and the sludge particles that settle least well is at least 30% by weight, more preferably at least 40% by weight, even more preferably at least 60% by weight of the total amount of sludge (excess sludge) discharged from the continuous purification process. Preferably, the average size of the smallest sludge particles that are separated and thus discharged is at most 0.4 mm, or even more preferably at most 0.2 mm. By doing so, the proportion of granular sludge increases.

[0054] As described above, this selective discharge (see also FIGS. 1A and 1B) can occur at various locations in the activated sludge system, for example, between the activated sludge reactor B and the secondary sedimentation tank NB, not only in the final sedimentation tank NB, in the return line of the activated sludge system, but also in the anaerobic selector S. All embodiments of the selector S preferably also have means for separating and discharging the smallest sludge particles or the sludge particles that settle worst. In one variant, the means such as discharge are located at the top of the selector S. For example, FIG. 9A shows how selective discharge can occur at the top of the sludge bed in selector c. This upper part of the tank contains in particular the smallest-sized sludge, and by discharging from the upper part of the tank, the smallest particles are separated from the larger sludge particles that are more present towards the bottom of the tank. FIG. 2b shows how the sludge discharge 7 occurs at the top of the compartment Sb where the concentration of the sludge having the smallest dimensions is highest, and FIG. 9A shows how the sludge e having the smallest dimensions is discharged through the sludge discharge 7. List of embodiments A method for the purification of substrate-containing wastewater in a continuous flow-through aerobic biological activated sludge reactor B, which optionally, after a pretreatment step VB of the supplied wastewater 1, at least a part of the biological sludge 6 is adjusted in the selector S under anaerobic or anoxic conditions using at least a part of the substrate-containing wastewater 2 to be purified, The adjustment comprises first accumulating sludge particles having a sedimentation rate of at least 2 m / h, and then bringing the substrate-containing wastewater into contact in the selector S with the sludge particles accumulated with a contact time of at least 10 minutes, and the selector S is operated or designed such that during the contact of the sludge with the substrate-containing wastewater, the sludge residence time in the selector S is longer than the hydraulic residence time of the sludge / water mixture 3 in the selector, The sludge / water mixture 3 is fed, optionally after an additional anaerobic or anoxic contact step, to the aerobic purification reactor B and subjected to aerobic treatment B, The treated wastewater 4 after aerobic treatment is optionally separated from the sludge by sedimentation, flotation treatment, or mechanical separation in the secondary sedimentation tank NB, and the selector receives the sludge 6 (at least a part thereof) separated from the aerobically treated wastewater and / or the sludge 6' from the aerobic purification reactor B. Method. 1. The method according to aspect 1, wherein in the selector, the sludge 6 is subjected to individual changes in flow rate and / or flow gradient together with the wastewater 2 under anaerobic or anoxic conditions. 2. The method according to aspect 2, wherein the individual change in flow rate is achieved by individual fluctuations in the flow of the selector in the flow direction and / or individual fluctuations in the flow rate. 3. The method according to any one of the preceding aspects, wherein the accumulated sludge is saturated with the substrate-containing wastewater in the selector to such an extent that at least 60%, preferably at least 75%, more preferably at least 80% of the biologically readily biodegradable substrate (rbCOD) is adsorbed by the sludge. 4. While the accumulated sludge is in contact with the substrate-containing wastewater, at least 20% by weight of the sludge in the selector S has a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector, and preferably at least 40%, more preferably 50-90% of the sludge in the selector has a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector. The method according to any one of the preceding aspects. 5. While the accumulated sludge is in contact with the substrate-containing wastewater, at least 20%, preferably at least 40%, more preferably 50-90% of the sludge in the selector has a residence time in the selector that is at least 40% longer than the hydraulic residence time of the sludge / water mixture in the selector. The method according to any one of the preceding aspects. 6. The method according to any one of the preceding aspects, wherein the selector adjusts the sludge-wastewater mixture such that at least 20%, more preferably 40-100% of the sludge in the aerobic biological purification reactor B becomes granular sludge having a minimum granule size of 0.212 mm. 7. such that the proportion of granular sludge is at least 25% by weight, preferably at least 30% by weight, most preferably at least 40% by weight, in particular at least 50% by weight; preferably, at least 20% by weight of this granular sludge (i.e., sludge having a size of at least 0.212 mm), or more preferably at least 25% by weight, preferably at least 30% by weight, most preferably at least 40% by weight, in particular at least 50% by weight of this granular sludge in the aerobic biological purification reactor B, has a particle size of at least 0.4 - 1.0 mm, the selector adjusting the sludge - wastewater mixture, the method according to any one of the preceding aspects. 8. at least 10% by weight of the largest sludge particles are in contact with the highest substrate concentration in the selector 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 with which 15% by weight of the smallest sludge particles in the selector are in contact, the method according to any one of the preceding aspects. 9. in addition to, or instead of, the return sludge 6 from the secondary sedimentation tank NB or the sludge 6' from the biological activated sludge reactor B, a sludge fraction received from a mechanical or gravity separator operating to selectively discharge the slowest - settling sludge in the biological purification or in the return sludge to the sludge processing line is fed to the selector S, the method according to any one of the preceding aspects. 10. increasing the concentration of rapidly biodegradable substrates by introducing an external carbon source, by means of a side - stream from a sludge processing line which is part of a treatment plant in which a biological purification reactor is being used, or by pretreating the wastewater wholly or partly using hydrolysis or fermentation, the method according to any one of the preceding aspects. 11. The selector S is an upflow reactor having a set of concentric compartments, with an inner first compartment Sa and at least one or more further compartments (such as Sb, Sc) oriented concentrically around the inner compartment, these further compartments being connected to the preceding compartment at the bottom and top, a supply of (return) sludge 6 and / or sludge 6' being located at the lower part of the first compartment Sa, each subsequent compartment having an inlet at the bottom for introducing the waste water 2 such that the sludge and the waste water come into contact with each other, whereby the selector provides a vertical flow ("upflow") in the compartments, according to any one of the preceding aspects. 12. The selector S is an upflow reactor having three adjacent interconnected compartments Sa, Sb, and optionally Sc with adjustable volumes, the effective volume of compartment Sa being smaller than that of Sb, biological sludge 6 and substrate-containing waste water 2 to be purified flowing continuously from Sa to Sb and from Sb to Sc, these compartments being in fluid connection with the previous compartment at the bottom and top, a supply of (return) sludge 6 and / or sludge 6' being located at the bottom of the first compartment Sa, each subsequent compartment having an inlet at the bottom 2 for introducing the waste water such that the sludge and the waste water come into contact with each other, whereby the selector provides a vertical flow ("upflow") in the compartments, according to any one of aspects 1 to 11. 13. The selector S is an upflow reactor having a plurality of, preferably three, adjacent interconnected compartments Sa, Sb, and optionally Sc, the volume of which is adjusted, the effective volume of compartment Sa being smaller than that of Sb, and sludge 6 and / or sludge 6' and the substrate-containing wastewater 2 to be purified continuously flowing from Sa to Sb and from Sb to Sc, these compartments being connected at the top to the preceding compartment, the inlet of the wastewater 2 being located at the bottom of the compartment, and the inlet of the returned sludge 6 and / or sludge 6' being located at the liquid level, whereby the selector provides a vertical flow ("upflow") in the compartment, according to any one of aspects 1 to 11. 14. The selector S includes at least two compartments Sa and Sb in which the feed of wastewater 2 and (returned) sludge 6 or sludge 6' is alternated with the discharge of conditioned sludge, and the sludge 6 or sludge 6' is provided at a flow rate of at least 2 m of wastewater per square meter of cross-section of the selector per hour, preferably at a location between the liquid level (6b) of the compartment and / or the bottom level (6a) of the compartment and the liquid level, so as to accumulate the desired sludge, the desired sludge residence time distribution in the selector S being obtained by feeding the wastewater 2 to the compartment at the bottom of the compartment, and the discharge of conditioned sludge can be achieved by applying fluctuations in the flow rate and / or by applying mixing, and / or it occurs by withdrawing at least a part of the sludge / wastewater at the bottom level (3a) of the compartment, according to any one of the preceding aspects. 2 per 3 square meter of the selector, and the adjusted sludge discharge can be achieved by applying fluctuations in the flow rate and / or by applying mixing, and / or it occurs by withdrawing at least a part of the sludge / wastewater at the bottom level (3a) of the compartment, according to any one of the preceding aspects. 15. The selector S operates intermittently, according to the method described in aspect 15. 16. The variation in the flow rate in the selector is achieved by varying the feed flow rate of the wastewater, according to any one of the preceding aspects. 17. The method according to any one of the preceding aspects, wherein the variation in the flow rate in the selector is achieved by varying the feed amount of sludge 6 and / or sludge 6'. 18. The method according to any one of the preceding aspects, wherein the selector S is fed with return sludge and / or a part of the excess sludge originating from another purification line. 19. The method according to any one of the preceding aspects, wherein the selector S follows or is incorporated into a granular sludge reactor operating on the basis of the sequential batch principle. 20. The method according to any one of the preceding aspects, wherein the addition of a carrier material accelerates the formation of granular sludge and / or aids in its maintenance, and the carrier material has an average size of 0.05 to 2.5 mm and a relative density or specific gravity equal to or greater than that of the wastewater. 21. The method according to any one of the preceding aspects, wherein the sludge in the reactor B comprises a mixture of biological sludge and a floating biofilm carrier. Detailed description of the invention

[0055] The present invention is a method for the purification of substrate-containing wastewater in a continuous flow-through aerobic biological activated sludge reactor B, which optionally, after a pretreatment step VB of the supplied wastewater 1, at least a part of the biological sludge 6 is adjusted in a selector S under anaerobic or anoxic conditions using at least a part of the substrate-containing wastewater 2 to be purified. The adjustment first involves accumulating sludge particles having a sedimentation rate of at least 2 m / h and bringing the substrate-containing wastewater into contact with the sludge particles accumulated in the selector S for a contact time of at least 10 minutes, and the selector S is operated or designed such that the sludge residence time in the selector S is longer than the hydraulic residence time of the sludge / water mixture 3 in the selector, thereby enabling sludge particles that sediment more greatly or more rapidly to come into contact with the highest substrate concentration. The sludge / water mixture 3 is fed to the aerobic purification reactor B, optionally after an additional anaerobic or anoxic contact step, and subjected to aerobic treatment B. The treated wastewater 4 after aerobic treatment is optionally separated from the sludge by sedimentation, flotation treatment, or mechanical separation in the secondary sedimentation tank NB, and a method is related to a selector receiving sludge 6 (at least a part thereof) separated from the aerobically treated wastewater and / or sludge 6' from the aerobic purification reactor B. The selector is preferably operated or designed to have a residence time in the selector such that at least 20% by weight of the sludge in the selector is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector while the sludge is in contact with the substrate-containing wastewater.

[0056] In particular, the present invention is a method for purifying substrate-containing wastewater in a continuous flow-through aerobic biological purification reactor B, comprising adjusting at least a part of the biological sludge 6 in a selector S under anaerobic or anoxic conditions using at least a part of the substrate-containing wastewater 2 to be treated (regardless of whether it is after the conventional pretreatment step VB of the supplied wastewater). The adjustment first involves accumulating sludge particles having a sedimentation rate of at least 2 m / h and contacting the substrate-containing wastewater with the sludge particles accumulated in the selector S for a contact time of at least 10 minutes. After that contact time, the substrate-containing wastewater is contacted with the remaining sludge particles in the selector S, and the selector S is operated or designed such that the sludge residence time in the selector S is longer than the hydraulic residence time of the sludge / water mixture in the selector, thereby enabling sludge particles that sediment more greatly or at a higher speed to contact the highest substrate concentration. Thereby, preferably while the sludge is in contact with the substrate-containing wastewater, at least 20% of the sludge in the selector comes to have a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector. The sludge / water mixture 3 (regardless of whether it is after any additional anaerobic or anoxic contact time) is fed to the aerobic purification reactor B and subjected to (conventional) aerobic purification. The treated (purified) wastewater 4 after aerobic treatment is separated from the sludge by a sedimentation tank NB, flotation treatment, or mechanical separation. The present invention relates to a method in which a selector receives sludge 6 (at least a part thereof) separated from the aerobic-treated wastewater and / or sludge 6' from the aerobic purification reactor B. A part of the sludge, preferably the sludge particles that settle worst, may be purged as sludge discharge 7. Reference is made here to FIGS. 1A and 1B.

[0057] In the context of the present invention, the terms "purifying wastewater" and "treating wastewater" are used interchangeably. Throughout this specification and the claims, unless otherwise explicitly stated, the term "retention time" is understood to be the average retention time.

[0058] First, the sludge that settles rapidly in the selector S is accumulated, and then the substrate-containing wastewater is brought into contact with the rapidly settling sludge accumulated for a contact time sufficient for the larger particles of the accumulated sludge to absorb the readily biodegradable substrate and become saturated with the concentrated substrate-containing wastewater. After that, the wastewater is brought into contact with the sludge remaining in the selector. Saturation can be measured, for example, by monitoring the change in P release from the sludge, the amount of readily biodegradable organic matter in the selector effluent, or a change in another parameter that changes with the redox profile, conductivity, pH, turbidity, color, or substrate absorption.

[0059] In the above method, the accumulated sludge is separated in the selector under anaerobic or anoxic conditions based on the difference in sedimentation degree, so that the larger sludge particles (characterized by a higher sedimentation degree) obtain a longer contact time with the wastewater, and the larger sludge particles come into contact with a higher substrate concentration in the wastewater than the smaller sludge particles. This can be achieved, for example, in the selector by applying (i) multiple phases with individual or discontinuous changes in the flow rate, (ii) a gradually increasing flow gradient (i.e., a continuously increasing flow rate), or a combination of (i) and (ii).

[0060] In one aspect, the sludge / water mixture in the selector is subjected to individual changes in flow rate and / or flow gradient under anaerobic or anoxic conditions. In certain aspects, the individual change in flow rate is achieved by individual fluctuations in the flow in the flow direction of the selector and / or individual fluctuations in the flow rate of the wastewater and / or return sludge being supplied.

[0061] Advantageously, starting from conventional activated sludge, granular sludge is produced by the method described above, preferably within 200 days after start, more preferably within 100 days after the start of the method. As described above, since granular sludge settles at a considerably higher rate than sludge flocs, it is possible to use a significantly smaller settling tank and / or maintain significantly more sludge in the purification process, resulting in a broader purification of wastewater. In the presented process, granular sludge is obtained in a continuous flow-through wastewater purification process and it is possible to maintain effective separation of sludge and treated water while using a smaller settling volume or a higher upward flow. Further, the volume of the anoxic tank between the anaerobic zone and the aerobic zone, or the anoxic compartment in the aerobic treatment reactor, can be reduced or such an anoxic tank / compartment is not required, and similarly, there is no need to recycle water / sludge from the aerobic zone to the anoxic and anaerobic zones, yet a broad removal of nitrogen compounds from the wastewater is still achieved.

[0062] In one aspect, the anoxic reactor compartment or reactor zone between the anaerobic step (a) and the aerobic step (b) can be eliminated.

[0063] As described above, the present invention is, in particular, a method for continuous flow-through wastewater purification, wherein wastewater 1 is optionally pretreated in a primary settling tank VB, and the pretreated wastewater 2 is subsequently (a) In selector S, contact with biological sludge 6 and / or 6' under anaerobic conditions to obtain a mixture of wastewater and sludge, where the selector S preferably has a sludge residence time that exceeds the hydraulic residence time to such an extent that at least 20% of the sludge accumulated in the selector has a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector, (b) Feed stream 3 having the sludge adjusted in the selector then to aerobic purification reactor B, (c) Optionally (by sedimentation in secondary sedimentation tank NB, flotation treatment, or mechanical separation) separate the sludge from the wastewater to obtain treated wastewater 5, where the selector receives sludge 6 (at least a portion thereof) separated from the aerobically treated wastewater and / or sludge 6' from aerobic purification reactor B. Preferably, the portion having the most poorly settling sludge particles can be purged from the treatment process as stream 7. This sludge purge 7 can occur at different positions within the treatment process or in combinations of positions.

[0064] In step (a) above, first accumulate or concentrate the biological sludge that settles rapidly entering S, then contact the substrate-containing wastewater with the sludge particles accumulated in selector S for a contact time of at least 10 minutes, and then feed stream 3 having the sludge adjusted in the selector to aerobic purification reactor B. "Biological sludge that settles rapidly" is understood to be sludge having a settling rate of at least 2 m / h, preferably at least 2.5 m / h, more preferably at least 3 m / h. The contact time is preferably 10 to 120 minutes, more preferably 20 to 90 minutes.

[0065] By doing so, the selector controls that larger and faster-settling sludge particles come into contact with the substrate-rich wastewater that is more concentrated and longer in contact time than the smaller and slower-settling sludge particles. As a result, the MOs in these larger sludge particles can absorb more substrate for a longer time than the smaller sludge particles that have a shorter residence time and less contact with the high substrate concentration. This provides a competitive advantage for the growth of MOs that stimulate granule growth and the subsequent formation and stable maintenance of granular sludge in the continuous flow-through purification process.

[0066] While the sludge is in contact with the substrate-containing wastewater, it is preferred that at least 40%, more preferably 50 - 90% of the sludge in the selector has a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector.

[0067] When no pretreatment is required, wastewater flows 1 and 2 are identical and interchangeable.

[0068] In one aspect, while the sludge is in contact with the substrate-containing wastewater, it is preferred that at least 40%, more preferably 50 - 90% of the sludge in the selector has a residence time in the selector that is at least 40% longer than the hydraulic residence time of the sludge / water mixture in the selector.

[0069] Preferably, the selector adjusts the sludge - wastewater mixture such that the proportion of granular sludge in the aerobic biological purification reactor B is at least 25% by weight, preferably at least 30% by weight, most preferably at least 40% by weight, especially at least 50% by weight, and at least 20% by weight of this granular sludge (i.e., sludge having a size of at least 0.212 mm), or more preferably at least 25% by weight, preferably at least 30% by weight, most preferably at least 40% by weight, especially at least 50% by weight of this granular sludge in the aerobic biological purification reactor B has a particle size of at least 0.4 - 1.0 mm.

[0070] In a preferred embodiment, the improved granular sludge size distribution and sludge residence time distribution according to the present invention are achieved using a selector S that applies an individual or discontinuous change in flow rate, preferably a selector S having different compartments (such as Sa, Sb, etc.) with their own flow rates, where the flow rate in a subsequent compartment is always 25 to 50% of that in the preceding compartment.

[0071] More preferably, the selector S is an upflow reactor having a set of concentric compartments, having an inner first compartment Sa and at least one or more further compartments (Sb, Sc, etc.) oriented concentrically around it, which are always in fluid connection with the previous compartment at the bottom and top, the supply of (return) sludge 6 and / or sludge 6' being located at the lower part of the first compartment S, and each subsequent compartment having an inlet at the bottom for introducing the wastewater 2 such that the sludge and the wastewater 1 come into contact with each other, whereby the selector provides a vertical flow ("upflow") in the compartments. A person skilled in the art can select the diameters of the different compartments in such a way that a desired difference in flow velocity is achieved between adjacent compartments. In this way, (a1) a first part S1 of the sludge containing sludge that settles at a lower rate is sent through the overflow to the second compartment, while a second part S2 of the sludge containing sludge that settles at a higher rate is collected at the bottom and sent to the second compartment via the connection at the bottom, where preferably the sludge S2 that settles at a higher rate in the second compartment is returned to contact with the wastewater at a lower flow rate, and the process of separating the sludge S3 that settles at a higher rate at the bottom side and at the connection with the third compartment from the sludge S4 that settles at a lower rate and is sent to the third compartment via the overflow is repeated. In this way, the contact time between the sludge that settles at a higher rate and the wastewater is increased, and it is achieved that the largest sludge particles experience the highest substrate concentration and can preferentially adsorb the substrate for the formation of the granules MO. For further explanation, reference is made to Figure 2A.

[0072] In one aspect, the selector S is an upflow reactor having three adjacent interconnected compartments Sa, Sb, and optionally Sc with adjusted volumes, the effective volume of compartment Sa being smaller than that of Sb, and biological sludge 6 and / or sludge 6' and substrate-containing wastewater 2 to be purified continuously flow from Sa to Sb and from Sb to Sc, and these compartments are always in fluid connection with the previous compartment at the bottom and the top, the supply of (return) sludge 6 and / or sludge 6' is located at the lower part of the first compartment, and each subsequent compartment has an inlet to the lower part 2 for introducing wastewater such that the sludge and wastewater 1 come into contact with each other, whereby the selector provides a vertical flow ("upflow") in the compartments. For further explanation, reference is made to FIG. 2B.

[0073] In the method according to the invention, the variation of the flow rate in the selector is achieved by varying the feed amount of the wastewater 2. The inventors have found that by varying the wastewater flow rate 2 during the day, the sludge residence time distribution can be further improved. In particular, during periods of low supply, the most readily sedimentable sludge particles accumulate at the bottom of the different compartments, and thus have the greatest contact with the most concentrated and least diluted wastewater. This makes the distribution of the sludge residence time of the sludge in the selector even more pronounced.

[0074] In the method according to the invention, the variation of the flow velocity in the selector is achieved by varying the flow rate of the sludge 6 and / or sludge 6' fed to the selector.

[0075] In a preferred embodiment, granulation not only results in a distribution of sludge age in the selector, but also increases the concentration of substrates present in the wastewater supplied by introducing a suitable external carbon source, or is further stimulated by promoting the growth of granulation MO by pretreating the wastewater supplied through processes such as hydrolysis, fermentation, etc. In this way, the proportion of readily biodegradable substrates, such as fatty acids, is increased, preferably to at least 15% of the total substrate concentration, or more preferably to at least 25% of the total substrate concentration. In one embodiment, the concentration of the substrate is increased by introducing an external carbon source, by a sidestream from a sludge processing line that is part of a treatment plant where a biological purification reactor is being used, or by pretreating the wastewater wholly or partly by hydrolysis or fermentation.

[0076] There are no restrictions on the wastewater source. The wastewater to be treated by the method according to the invention typically contains organic nutrients (organic substances) and is also referred to as substrate-containing wastewater in the context of the present invention. Typically, the biochemical oxygen demand (BOD) of the influent wastewater is at least 50 mg / l, for example, 100 - 10,000 mg / l. Any type of wastewater, such as sewage or water from industrial production processes, can be treated by the present invention. The method according to the invention can therefore also be referred to as wastewater treatment. The wastewater subjected to the process according to the invention may be pretreated before step (a), such as wastewater that has undergone primary treatment as known in the art, although primary treatment may not necessarily be required to efficiently carry out the current process. Typical wastewater pretreatment techniques include one or more of the following: purification, removal of coarse suspended matter, removal of animal fat, and primary sedimentation.

[0077] In one aspect, the proportion of rapidly biodegradable fatty acids in the wastewater source is less than 10 to 15% by weight of the total substrate / nutrients, and / or the fatty acid concentration in the supplied wastewater varies, such that this proportion is less than 10 to 15% by weight with a probability of at least 20%. The inventors have found that the low fatty acid concentration and its variation complicate continuous wastewater treatment based on the granular sludge technology; however, the use of the selector according to the present invention enables the continuous wastewater purification based on the granular sludge technology to be manageable.

[0078] The selector S according to the present invention is part of the anaerobic zone. In a preferred aspect, the selector S forms the anaerobic zone (only). The conditions in the selector S are referred to as "anaerobic" because no oxygen is added. As described above, it is also possible that the conditions in the selector S are anoxic. Under anoxic conditions, in addition to organic pollutants, nitrogen oxide compounds, such as nitrite and nitrate, are also present, and MOs that convert these into harmless nitrogen gas can propagate. Under anaerobic conditions, the concentration of such nitrogen oxide compounds is limited or not present at all. Under such conditions, MOs that store phosphate can propagate. Within the anaerobic zone, the conditions and residence time of the wastewater are such that the sludge granules can absorb organic nutrients from the influent wastewater. These organic nutrients are typically stored in microorganisms in the form of polymers, such as poly-beta-hydroxybutyric acid (PHB). The typical average residence time of the sludge and water mixture in the anaerobic zone of the process is from 15 minutes to 5 hours, preferably from 30 minutes to 2 hours.

[0079] As mentioned in the introduction section, granular sludge is defined in the prior art as sludge having a size of at least 0.212 mm (and typically smaller than 6 mm), which does not coagulate during sedimentation, and thus the SVI after 5 minutes of sedimentation is equivalent to that after 30 minutes of sedimentation. Flocculent sludge has a smaller size. A small amount of flocculent sludge may be present in the wastewater purification system according to the present invention, but the method aims to reduce the proportion of flocculent sludge. Since the residence time in the selector S is short, the contact with the substrate in the selector is also short, and naturally it does not contact the highest substrate concentration in the selector, the growth of the flocculent sludge is not promoted, and the fraction of the flocculent sludge remains trace. In the current process, the proportion of flocculent sludge having a size of 0.212 mm or less is preferably limited to a maximum of 50% by weight, preferably less than 40% by weight, more preferably less than 30% by weight. The current process functions smoothly with such a limited amount of flocculent sludge. In addition, the amount of flocculent sludge can be further reduced by removing sludge having the property of not settling too rapidly, in particular, through sludge discharge 7 (excess sludge is discharged from the purification system to prevent the accumulation of sludge due to continuous sludge growth), for example, by withdrawing this sludge as far as possible from the inlet in the secondary sedimentation tank, or by drawing this sludge into a location where the proportion of sludge settling at a higher speed in the selector is small, and / or by applying a gravity or mechanical separator to the returned sludge, or in parallel to the aerobic reactor or selector, and purging the minimum sludge thus obtained.

[0080] In the context of the present invention, the terms "faster-settling sludge" and "heavy sludge" are considered synonymous, and the terms "slower-settling sludge" and "light sludge" are likewise synonymous. The settling degree or settling rate is generally determined in the art. An actual measure of the settling degree known in the art is the sludge volume index (SVI). SVI is defined as the volume (ml) occupied by 1 gram of sludge after a specific settling time. A typical value of the ratio of SVI-5 (SVI after 5 minutes of settling) to SVI-30 (SVI after 30 minutes of settling) of the granular sludge of the present invention is less than 3, typically in the range of 1 to 2.5, more typically approximately 1.5, while conventional flocculated sludge has an SVI-5 / SVI-30 ratio greater than 3.

[0081] In view of the presence of microorganisms, the sludge present in the system according to the present invention can also be referred to as "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 the retention of these microorganisms as part of the granular sludge, so they do not necessarily have to be isolated.

[0082] The mixture of wastewater and sludge exiting the selector S is then transferred to the aerobic reactor B, where oxygen molecules are supplied (aerated) using, for example, an aerator known in the art. The average residence time of the mixture of sludge and water in the aerobic reactor B can vary widely, for example, depending on the amount and type of contaminants in the influent wastewater and the degree of purification desired, and is typically from 1 to 30 hours, preferably from 2 to 20 hours. The average residence time of the sludge also varies, for example, depending on the amount and type of contaminants in the influent wastewater and the degree of purification desired, and is typically from 3 to 40 days, preferably from 5 to 20 days. The aeration of the aerobic zone is carried out in an amount such that the concentration of oxygen molecules dissolved in the wastewater in reactor B is preferably at least 0.5 mg / l, more preferably at least 1 mg / l, and at the same time preferably 5 mg / l or less, more preferably 10 mg / l or less. Modifying conventional aerobic reactors and the aerobic conditions herein is not part of the present invention.

[0083] In addition to the aerobic zone or compartment, reactor B may also have zones and compartments in which anoxic conditions occur, where denitrification and further removal of nitrogen compounds from the wastewater are achieved.

[0084] Subsequently, the biologically purified wastewater is preferably separated from the sludge and water mixture from reactor B. This is usually achieved by sedimentation (secondary sedimentation in secondary sedimentation tank NB), but it may also be achieved by mechanical separation, flotation, filtration, or other methods. Such sedimentation and separation steps for separating sludge from treated water are common in conventional wastewater treatment plants. Due to the presence of granular sludge rather than flocculent sludge, the sedimentation tank can be much smaller compared to the conventional tanks required to sediment flocculent sludge (e.g., about one-fourth the area for the same wastewater input), or filtration can be achieved at a higher filtration flux. The water and sludge mixture flowing in from reactor B remains in the sedimentation tank or similar separator for a sufficient time. After the sludge is separated from the water, the biologically treated wastewater is clean enough to be discharged to the environment, but for some uses and / or locations, further treatment, e.g., filtration or removal of metals as an example, may be desirable.

[0085] The water treated according to the invention discharged from the clarifier or similar separator is the main product of the process according to the invention. Compared to the influent wastewater, the purified water has had organic substances (organic nutrients) extracted. The treated water can be discharged to the environment, further purified, or utilized as desired.

[0086] In the method described above, the sludge starts from conventional activated sludge and preferably forms granular sludge within 200 days after start, more preferably within 150 days after start, and is naturally selected to consistently contain the majority of the sludge during the purification process. First, by starting the purification process using sludge that already contains at least a portion of granular sludge, the formation of the majority of granular sludge can be accelerated and assisted. Preferably, the proportion of granular sludge in the sludge added to the system during start is at least 15% by weight, and the sludge concentration is 3 kg / m 3 , preferably 0.6 kg / m 3Exceeds. More preferably, it starts with sludge that is already granular sludge and exceeds 50%.

[0087] Also, the formation and stable maintenance of granular sludge can be accelerated and assisted by continuously or occasionally adding solids or chemicals to the sludge to which sludge particles can adhere, thereby increasing their size or weight. This solid support material preferably has a size of 0.05 - 2.5 mm and a specific gravity equal to or greater than that of the wastewater. This material can be, for example, granular sludge from another reactor, screened activated sludge, classified sand, plastic granules, or other natural or synthetic materials. For example, a solid having a specific gravity of at least 1.05 kg / l is added to the sludge. MO in the sludge adheres to this substance, causing an increase in the density and thus the sedimentation degree of the sludge particles. A similar effect is achieved by introducing liquid chemicals such as iron salts, aluminum salts, calcium salts, etc., such that salts in the sludge / water mixture react to form solids.

[0088] The present invention can also be applied in parallel with conventional processes that do not provide for the formation of granular sludge or enable a wide range of granulation. This is shown in Figure 10. Here, the purification line L1 is conventional purification, and the biological reactor includes one or more compartments or reactors that allow for various combinations of aerobic, anoxic, and anaerobic process conditions. In the drawing, this is shown as B1, B2, and B3, but there may be more or fewer parts. The purification line L2 is the method according to the present invention. By connecting the effluent sludge line from L2 to L1, the purification line according to the present invention also has a synergistic effect on the operation, sludge characteristics, and MO of the conventional purification line. This is achieved by not discharging the sludge from the purification line L2 to sludge processing (7), but rather transferring it, either wholly or partly, to one or more of the components of the biological reactor (line 8). As a result, this effluent sludge has better biomass characteristics with a larger size and additional simultaneous denitrification capacity compared to the normal sludge in the conventional line, and thus will improve the sludge characteristics and the operation of the conventional line. This synergistic effect can be further enhanced by feeding a part of the returned sludge 6 and / or the sludge discharge 7 from the conventional line L1 to L2 via line 9. In this way, a part of the sludge in the conventional line is also subjected to the action of the selector S of line L2. As a result of the above-described connection of the two purification lines, improved action and larger sludge particles can be obtained in line L1 without the need to treat all the wastewater and sludge by the innovative selector S and without the need to replace L1 with the purification according to the present invention. In one aspect, the method according to the present invention includes the step of feeding the waste sludge 7 (as 8) to a conventional treatment, preferably a treatment that does not have means for achieving granular sludge. In another aspect, the method according to the present invention includes the step of supplying surplus sludge or a part of the returned sludge from the conventional purification.

[0089] In another variant, the selector according to the invention follows or is integrated into an aerobic granular sludge (AGS) reactor operating as a sequential batch system (SBR), and the same synergistic effect is obtained by connecting it to a conventional continuous flow-through system as described above. This is shown in FIG. 10. The purification line L3 includes the selector according to the invention as well as the AGS SBR. The sludge discharge (7) from the S-AGS-SBR in L3 is fed via line 10 to the conventional line L1. Similar to the above-described synergistic connection, the sludge discharge (7) or a part of the return sludge from the conventional line can also be fed to the selector S (via line 9).

[0090] Based on the above, the invention also features a mode of feeding a part of the return sludge and / or sludge discharge originating from another purification line to the selector S, or a mode in which the selector S is followed by or integrated with a granular sludge reactor operating according to the sequential batch principle. Therefore, it is preferred that the selector S is in fluid connection with or integrated into a granular sludge reactor operating based on the sequential batch principle.

[0091] In a preferred embodiment, the method operates in parallel with one or more other wastewater purification process lines, and the selector S receives the biological sludge 6 and / or sludge 6', and a part of the biological sludge 9 from these parallel other wastewater purification process lines. Optionally, a part of the biological sludge 6 is induced into these parallel other wastewater purification process lines.

[0092] [Example] The advantages of the present invention have been clearly demonstrated in pilot plant operation. This pilot plant has a series of six hybrid anaerobic compartments (selector S 3 ~S A ~S F ) with a volume of 0.075 to 0.15 m, and a series of six hybrid anoxic / aerobic reactor compartments (reactor B 3 ) each with a volume of 1 mA ~B F ) and 0.32 m 3 included a clarifier. The last reactor compartment B F also included a partially submerged manifold for the periodic discharge of sludge after the sedimentation period, aimed at increasing the retention of better-settling sludge. The fraction of returned sludge could also be discharged as excess sludge. A positive-displacement pump was used for the recirculation of the mixed liquid (from the aerobic zone to the anoxic zone) or the returned sludge (from the clarifier to the anaerobic selector). The returned sludge could be split between the anaerobic selector and the first aerobic / anoxic compartment. The mixed aerobic / anoxic compartment was equipped with fine bubble aeration and coarse bubble aeration that could be controlled independently. The sludge was suspended by mechanical agitation in all the mixed compartments. With this pilot, various configurations of the flow-through granular activated sludge system configuration were tested.

[0093] The inventors first operated this pilot in a configuration representing the current state of the art. This current state of the art was considered to be a multi-stage activated sludge process involving the use of a plug flow anaerobic selector and selective sludge discharge. The configuration was as follows: 1. Wastewater and returned sludge flow into selector tank S A and subsequently flow into selector tanks S B , S C , S D , S E , and S F . The working volume of each tank was 0.075 m 3 . 2. Reactor B A : Anoxic. 3. Reactor B B ~ E : Aerobic, operating at a dissolved oxygen concentration (DO) of 2 mg / l. 4. Reactor B F : Aerobic, equipped with a submerged manifold for selective sludge discharge, with the sludge sedimentation selection criterion set at 3 m / h. 5. Clarifier.

[0094] After the primary clarification stage, municipal wastewater was fed to the pilot configuration. The primary eluate contained on average 425 mg / l of chemical oxygen demand (COD), 8.1 mg / l of phosphorus (P), 6 mg / l of P, 51 mg / l of ammonium (N), and 110 mg / l of total suspended solids (TSS). The influent flow rate varied between 250 and 500 l / h, while the sludge return coefficient from the clarifier to the anaerobic selector was between 0.5 and 1.0. Reactor B E from B A to the anoxic recycle flow was equal to the sum of the influent and return sludge flows. Prior to the start of the experiment, the reactor was seeded with aerobic granular sludge originating from a Nereda® reactor. During the experiment, the sludge sedimentation characteristics and sludge size distribution were monitored. To distinguish between flocculent sludge and granular sludge, a 200 micron sieve was used to classify the sludge samples, and then the dry solid levels of the classified fractions were measured.

[0095] The experiment was repeated with the same configuration and similar flow and wastewater composition, but this time with two selectors S 3 of 0.375 m A each and S BIt was used according to the configuration presented in FIG. 8b. Both selector tanks were operated in a counterparallel cycle. First, sludge with a settling rate of at least 3 m / h was accumulated in the selector by feeding return sludge from the clarifier at a height of 50% of the liquid height of the selector. The feed flow corresponded to a surface loading of approximately 3 m / h, and the sludge / water mixture overflowed from the top water level of the selector (3b in FIG. 8). Subsequently, wastewater was fed to the selector, introduced at the bottom level, and overflowed from the top while flowing upward through the accumulated sludge (3b in FIG. 8). Finally, the conditioned sludge was displaced by discharging the sludge / water mixture at the bottom of the selector (3a in FIG. 8) while feeding sludge to the top of the selector (6b in FIG. 8) before repeating the accumulation cycle. The pilot configuration was again seeded with aerobic granular sludge originating from the Nereda® reactor.

[0096] FIG. 11a plots the development over time of the sludge volume index and sieve fraction in a flow-through pilot-scale configuration after seeding with aerobic granular sludge for (a) a prior art configuration and (b) the configuration according to FIG. 8b. As can be seen in FIG. 11A, the granule levels in the sludge both decreased, and the SVI 30increased within two months from levels typical of granular sludge to levels typical of flocculent sludge. Apparently, granular MO was eliminated by the flocculent growing MO. Also, the total sludge amount was reduced from approximately 6 g / l of TSS to approximately 2.5 g / l of TSS. By using the selector according to the invention, in contrast to the first-described experiment, the amount of granules did not substantially decline during the entire period of the experiment and a granule size of 1 mm was maintained: Figure 11b. Not only did the granules remain a significant majority of the total sludge amount for a period exceeding 400 days, but the total sludge amount also increased from approximately 4 to approximately 6 - 7 g / l of TSS, which was significantly higher than that in the experiments using prior art configurations. Also, after the initial decline caused by equipment problems, the percentage of granules within the total sludge amount remained at a high level of 60 - 80% and was shown to increase after the initial decline. Also, Figure 11B shows that the amount of smaller granules decreased while the amount of larger granules increased. SVI 30 remained within 40 - 70 ml / g, which was consistent with sludge having excellent sedimentation characteristics. In addition, the sludge concentration reached and was maintained at approximately 4 - 5 g / l of TSS.

Claims

1. A method for purifying substrate-containing wastewater in a continuous flow-through aerobic biological activated sludge reactor B, optionally after a pretreatment step VB of the supplied wastewater 1, at least a part of the biological sludge 6 is adjusted in a selector S under anaerobic or anoxic conditions using at least a part of the substrate-containing wastewater 2 to be purified, The adjustment first involves accumulating sludge particles having a sedimentation rate of at least 2 m / h, and then contacting the substrate-containing wastewater with the accumulated sludge particles in the selector S for a contact time of at least 10 minutes. The selector S is operated or designed such that during the contact of the sludge with the substrate-containing wastewater, the sludge retention time in the selector S is longer than the hydraulic retention time of the sludge / water mixture 3 in the selector. The sludge / water mixture 3 is optionally fed to an aerobic purification reactor B after an additional anaerobic or anoxic contact step and subjected to aerobic treatment B. The treated wastewater 4 after aerobic treatment is optionally separated from the sludge by sedimentation, flotation treatment, or mechanical separation in a secondary sedimentation tank NB. The selector receives the sludge 6 (at least a part thereof) separated from the aerobically treated wastewater and / or the sludge 6' from the aerobic purification reactor B. Method.

2. The method according to claim 1, wherein in the selector, the sludge 6 is subjected to individual changes in flow rate and / or flow gradient together with the wastewater 2 under anaerobic or anoxic conditions.

3. The method according to claim 2, wherein the individual change in flow rate is achieved by individual fluctuations in the flow in the flow direction of the selector and / or individual fluctuations in the flow rate.

4. The method according to any one of the preceding claims, wherein the accumulated sludge is saturated with the substrate-containing wastewater in the selector to such an extent that preferably at least 60%, preferably at least 75%, more preferably at least 80% of the biologically readily biodegradable substrate (rbCOD) is adsorbed by the sludge.

5. While the accumulated sludge is being contacted with the substrate-containing wastewater, at least 20% by weight of the sludge in the selector S has a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector, and preferably at least 40%, more preferably 50 to 90% of the sludge in the selector has a residence time in the selector that is at least 20% longer than the hydraulic residence time of the sludge / water mixture in the selector, according to any one of the preceding claims.

6. While the accumulated sludge is being contacted with the substrate-containing wastewater, at least 20%, preferably at least 40%, more preferably 50 to 90% of the sludge in the selector has a residence time in the selector that is at least 40% longer than the hydraulic residence time of the sludge / water mixture in the selector, according to any one of the preceding claims.

7. The selector adjusts the sludge-wastewater mixture such that at least 20%, more preferably 40 to 100% of the sludge in the aerobic biological purification reactor B becomes granular sludge having a minimum granule size of 0.212 mm, according to any one of the preceding claims.

8. The selector adjusts the sludge-wastewater mixture such that the proportion of granular sludge is at least 25% by weight, preferably at least 30% by weight, most preferably at least 40% by weight, especially at least 50% by weight; preferably, at least 20% by weight of this granular sludge (i.e., sludge having a size of at least 0.212 mm), or more preferably at least 25% by weight, preferably at least 30% by weight, most preferably at least 40% by weight, especially at least 50% by weight of this granular sludge in the aerobic biological purification reactor B has a particle size of at least 0.4 to 1.0 mm, according to any one of the preceding claims.

9. The method according to any one of the preceding claims, wherein at least 10% by weight of the largest sludge particles are in contact in the selector with the highest substrate concentration 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 with which 15% by weight of the smallest sludge particles in the selector are in contact.

10. The method according to any one of the preceding claims, wherein a sludge fraction received from a mechanical or gravity separator operating to selectively discharge the slowest-settling sludge in the biological purification or in the return sludge, in addition to or instead of the return sludge 6 from the secondary sedimentation tank NB or the sludge 6' from the biological activated sludge reactor B, is fed to the selector S.

11. The method according to any one of the preceding claims, wherein the concentration of readily biodegradable substrates is increased by introducing an external carbon source, by means of a side stream from the sludge processing line which is part of the treatment plant in which the biological purification reactor is being used, or by pretreating the wastewater wholly or partly using hydrolysis or fermentation.

12. The method according to any one of the preceding claims, wherein the selector S is an upflow reactor having a set of concentric compartments, having an inner first compartment Sa and at least one or more further compartments (Sb, Sc, etc.) oriented concentrically around the inner compartment, these further compartments being connected to the preceding compartment at the bottom and at the top, the supply of (return) sludge 6 and / or sludge 6' being located at the lower part of the first compartment Sa, and each subsequent compartment having an inlet at the bottom for introducing the wastewater 2 such that the sludge and the wastewater come into contact with each other, whereby the selector provides a vertical flow ("upflow") in the compartments.

13. The selector S is an upflow reactor having three adjacent interconnected compartments Sa, Sb, and optionally Sc with adjustable volumes, the effective volume of compartment Sa being smaller than that of Sb, and biological sludge 6 and substrate-containing wastewater 2 to be purified continuously flowing from Sa to Sb and from Sb to Sc, these compartments being in fluid connection with the previous compartment at the bottom and at the top, a supply of (return) sludge 6 and / or sludge 6' being located at the bottom of the first compartment Sa, each subsequent compartment having an inlet to the bottom 2 for admitting wastewater such that the sludge and the wastewater come into contact with each other, whereby the selector provides a vertical flow ("upflow") in the compartments, according to any one of claims 1 to 11.

14. The selector S is an upflow reactor having a plurality of, preferably three, adjacent interconnected compartments Sa, Sb, and optionally Sc with adjustable volumes, the effective volume of compartment Sa being smaller than that of Sb, and sludge 6 and / or sludge 6' and substrate-containing wastewater 2 to be purified continuously flowing from Sa to Sb and from Sb to Sc, these compartments being connected to the preceding compartment at the top, the inlet of the wastewater 2 being located at the bottom of the compartment, and the inlet of the return sludge 6 and / or sludge 6' being located at the liquid level, whereby the selector provides a vertical flow ("upflow") in the compartments, according to any one of claims 1 to 11.

15. The selector S comprises at least two compartments Sa and Sb in which the feeding of wastewater 2 and (return) sludge 6 or sludge 6' alternates with the discharge of the conditioned sludge, and the sludge 6 or sludge 6' is fed to the liquid level (6b) of the compartments and / or at a point between the bottom level (6a) of the compartments and the liquid level, preferably at a rate of 1 m 2 of the cross-sectional area of ​​the selector per hour. ２ At least 2m per ３ 2. The method according to any one of the preceding claims, wherein a desired sludge accumulation is achieved by providing wastewater 2 at a flow rate of 1000 s to the compartment, a desired sludge residence time distribution in the selector S is obtained by feeding the compartment with wastewater 2 at the bottom of the compartment, and discharge of the conditioned sludge can be achieved by applying flow rate variations and / or by applying mixing and / or it occurs by withdrawing at least a part of the sludge / wastewater at the bottom level (3a) of the compartment.

16. The selector S operates intermittently, according to the method of claim 15.

17. The variation of the flow rate in the selector is achieved by varying the feed flow rate of the wastewater, according to any one of the preceding claims.

18. The variation of the flow rate in the selector is achieved by varying the feed amount of the sludge 6 and / or sludge 6', according to any one of the preceding claims.

19. The selector S is also fed with a part of the return sludge and / or excess sludge originating from another purification line, according to any one of the preceding claims.

20. The method according to any one of the preceding claims, wherein the selector S follows or is incorporated into a granular sludge reactor operating on the basis of the sequential batch principle.

21. The method according to any one of the preceding claims, wherein the addition of a carrier material accelerates the formation of granular sludge and / or aids in its maintenance, the 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 that of the wastewater.

22. The method according to any one of the preceding claims, wherein the sludge in reactor B comprises a mixture of biological sludge and floating biofilm carriers.

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