Technical Field

[0001] The present invention relates to a biological reactor for wastewater treatment from minor sources of pollution, which utilizes activation process.

Background of the Invention

[0002] Package domestic wastewater treatment plants and small wastewater treatment plants are used for treatment of wastewater contaminated by sewage from sources that cannot be connected to public sewer system.

[0003] Package domestic wastewater treatment plants are increasingly used; they are made of plastic using injection, casting or welding of finished blocks, as these are relatively lightweight, waterproof, recyclable and provide long service life.

[0004] One of the most widely used systems of wastewater treatment in domestic plant segment is activation process, especially low-loaded activation system with activated sludge in upflow and/or with growth culture on bio-carrier.

[0005] Construction of domestic wastewater treatment plant must provide the following primary functions:

- to capture gross, non-degradable impurities, such as plastic, wood, bones, etc.;

- to capture and process gross, degradable impurities, such as food leftovers, toilet paper, etc.;

- to mix and aerate the activation zone where degradation of organic impurities, nitrification or denitrification takes place using activated sludge either in upflow or immobilized on biomass carriers or using combined system;

- to separate activated sludge from clear treated water in separation zone and return the separated activated sludge into treatment process as return sludge;

- to store and stabilize surplus activated sludge produced in the process of waste water treatment until the following disposal of surplus sludge.

[0006] These primary functions can be combined best in a biological reactor with optimum shape and dimensions which provide the aforementioned processes as well as meet utility criteria. Biological reactors, in terms of the present state of technology, are divided into at least three functional zones: mechanical pre-treatment zone, activation zone and separation zone. In this classification, biological reactors may consist of one or three tanks where the respective zones are separated by partition walls (WO92/03386). In such case, it is of high significance that circulation, mixing and settling inside the biological reactor runs in all functional zones of the reactor at conditions that are optimal for the processes occurring therein and that circulatory currents follow the wastewater treatment sequence required by the technology while mixing and circulation must be carried out in an energetically efficient manner.

[0007] Circulation and mixing are the key to capture, crushing and biological treatment of gross, degradable impurities in the mechanical pre-treatment zone. According to the present state of art (US2003/0183572A1, SK283582), the most preferred is mixing by air-lift pump, which drives mixture of air bubbles with activated mixture under a mechanical strainer, where these gross impurities are captured; the hydrodynamic force of the incoming liquid with biologically active mixture of wastewater and activated sludge performs gradual disintegration and biological treatment of worse degradable substances such as fat clusters, paper, etc. Activated mixture, brought into a basket for gross impurities using an air-lift pump, usually leaves through the grate walls of the basket together with incoming wastewater carrying particles ground off the gross impurities directly into the further functional zones of the biological reactor; either the mechanical pre-treatment zone or non-aerated or aerated activation zone. Flow of the mixture out of the basket can be directed by vertical walls, which may lead the activated mixture to the bottom; vertical walls may be clustered in series, directing the flow downwards and upwards. Such internal arrangement of non-aerated activation zone or mechanical pre-treatment zone is effective for better processing of worse degradable organic compounds and higher effectiveness. However, it increases the complexity of the device, makes de-sludging more difficult, device being heavier and more expensive. Mechanical pre-treatment assembly including screen basket, flow regulator, etc. are often permanently fitted with the exception of basket for gross impurities.

[0008] Circulation and mixing are also very important in ensuring that devices is odor-free device, especially in the zone of mechanical pre-treatment where undigested, raw organic substances and residues are and where surplus biological sludge is stored. In the present state of art, the odor-free state is most often achieved by good sealing of the non-aerated zone for mechanical pre-treatment and through treatment of the air (WO2009/082237A1) or by ventilation of the zone to the height above the highest floor of the attached building, which are both relatively expensive measures. [0009] Further, circulation and mixing is important for decreasing of floating substances and froth on the water surface in the domestic wastewater treatment plant. Floating substances and froth do not only represent an unaesthetic factor, but as floating substances and froth are not sufficiently enough drawn into the treatment process, they can result in problems with odor, reproduction of small insects and negatively affect effective treatment by leaking into the separation zone. This issue can be solved by using further air-lift pumps which either pump off the froth and floating substances into basket for the mechanical pre-treatment (SK6782002A3, US3709363, US005785854A ), or by continuous pumping from one zone into another over a partition wall ensuring permanent circulation between the zones of the biological reactor through at least one wall, which will clean the water surface from froth and floating substances. Besides the fact that such solution requires another air-lift pump, partitioning of the internal space of biological reactor by walls can represent complications when emptying and filling of such reactor with water or wastewater.

[0010] It is widely known that maintaining highly oxic conditions in aerated oxic zone with simultaneous maintaining of deeply anoxic environment in the non-aerated, anoxic activation zone and effective circulation between these zones for alternation of oxic and anoxic conditions is very important for improvement of treatment effectiveness from the view of degradation of ammonium nitrogen (nitrification) or total nitrogen (denitrification). The recirculation of activated mixture between anoxic and oxic zone that ensures nitrogen removal through denitrification process is, in the case of domestic and small wastewater treatment plants, mostly provided by hydro-pneumatic air-lift pumps which are less disruptive to activated sludge floes than mechanical pumps while being more economical in terms of both investments and operation. Recirculation by air-lift pump requires regulation of air content, either by manual air valve or by electromagnetic valve, which makes the operation more complicated and the device more expensive. Recirculation of activated mixture between different functional activation zones can also be achieved by horizontal rotational flow which can be induced by mechanical stirring device (US4452700) or by pneumatic method (US3879285); however, it always involves mixing of the whole cross-section of the tank.

[0011] This invention aims to develop device for treatment of waste water from minor sources of pollution with high cleaning effectiveness and parallel biological removal of nitrogen, elimination of odors, reduced sludge production and minimized investment and operational costs for activated sludge recirculation. Nature of the Invention

[0012] This problem is solved and drawbacks of the previous devices are largely eliminated by biological reactor for wastewater treatment from minor sources of pollution by activation process utilizing activated sludge in upflow and/or with growth culture on bio-carrier, where all processes of biological treatment with activation system take place in a single-tank biological reactor with spatially separated functional zones of mechanical pre-treatment, anaerobic sludge zone for decreasing sludge production, anoxic non-aerated zone for denitrification, oxic aerated zone for nitrification and separation zone for separation of activated sludge from clear treated water according to this invention, based on the principle of a device with one tank with useful circular ground plan, containing separation chamber with useful circular ground plan. The space between casing of the separation chamber and the casing of the biological reactor tank is divided into two chambers using two vertical partition walls A and B spanning from the bottom of the biological reactor over the surface of water inside the biological reactor tank, namely mechanical pre-treatment chamber with the anaerobic sludge zone in the lower portion of the mechanical pre-treatment chamber and anoxic non-aerated zone in the upper portion of the mechanical pre- treatment chamber, and aerated chamber. Mechanical pre-treatment chamber and aerated chamber are connected by an opening in the upper portion of both vertical partition walls A and B, where aerating elements are located near the bottom of the aerated chamber in front of the vertical partition walls A and B. Recirculation of activated mixture from the oxic aerated chamber into anoxic non-aerated zone of the mechanical pre-treatment chamber is provided by placement of aeration elements in such manner that a height the water column over the aeration element A is lower than height the water column over the aeration element B and/or air flow into aeration elements is regulated by air flow regulator so that higher amount of air flows into the aeration element A than into the aeration element B, which, due to higher amount of air bubbles flowing up along the partition wall A than the partition wall B, causes lower water density near the partition wall A than partition wall B, resulting in flow from the place of higher density to the place of lower density, which causes rotational, horizontal circulation of water surface layer of activated mixture around the upper, cylindrical portion of the casing of the separation chamber.

[0013] In the preferred embodiment, the lower edge of openings in partition walls A and B is located at most 15 cm below the water surface, which ensures only circulation of the surface, maximum 15 cm high layer of water with dissolved oxygen and activated sludge in oxic state; besides recirculation of activated mixture between mechanical pre-treatment chamber and aerated chamber, this provides odor-free nature of the mechanical pre-treatment chamber and decreased production of the froth on water surface. Horizontal flow carries smelly gases and organic molecules, which are being mixed with the stream, while the odorants are absorbed in regenerated activated sludge, which binds them by adsorption and absorption and performs their aerobic degradation. Below the horizontally flowing activated mixture, anaerobic-anoxic environment is maintained in mechanical pre-treatment chamber, so anaerobic processes can continuously degrade surplus sludge and nitrogen can be partially reduced by biological process.

[0014] In the preferred embodiment, aeration elements A and B are formed by a pipe-type aeration element. At the bottom of the biological reactor, in the aerated chamber there is a pipe- type aeration element with perforation along its whole length, in at least 1° angle with the bottom of the biological reactor, so that the perforated part of the aeration element A is situated higher than the perforated part near the partition wall B.

[0015] in the preferred embodiment, mechanically pre-treated wastewater is mixed with recirculated sludge pumped by air-lift pump from the bottom of separation chamber and the flow of such activated mixture is pipe-directed to the bottom of the mechanical pre-treatment with anaerobic conditions providing degradation of primary settleable organic substances and degrading surplus sludge, from where it flows up through a layer of settled sludge towards the surface, where it meets horizontal flow of recirculated activated sludge, creating anoxic conditions for biological nitrogen degradation (denitrification) below the water surface.

[0016] Preferably, the tank has circularground plan with downward tapering conical shape, which provides beneficial spatial arrangement for settling and concentrating of primary sludge and surplus sludge at the bottom of the mechanical pre-treatment chamber. If a removable, assembled internal construction is fitted into the empty tank, conical-bottom tanks can be inserted one into another thereby saving space during transport of multiple pieces.

[0017] Through solving drawbacks of the present state of art according to this invention, such construction of wastewater treatment biological reactor for minor sources of pollution was developed that provides effective removal of organic pollution from wastewater with parallel biological reduction of nitrogen, odor elimination, reduced sludge production and minimized investment and operational costs of activated sludge recirculation. Overview of Figures in Drawings

[0018] Principle of the invention is further clarified in examples of its implementation, which are described based on the attached drawings that show:

- Figure 1 a, b, c: Biological reactor for wastewater treatment with activated sludge in upflow according to the invention;

- Figure 2 a, b: Biological reactor for wastewater treatment with activated sludge in combined system of upflow and bio-carrier according to the invention;

- Figure 3 a, b: Biological reactor for wastewater treatment with activated sludge in upflow according to the invention.

Examples of Embodiments

Example 1

[0019] Biological reactor for wastewater treatment from minor sources of pollution using activation process with activated sludge in upflow, according to the invention, Fig. 1 a, b, c has a tank I with a casing 2 and a bottom 3 with conical, downward tapering shape. The tank \ has an inflow 9 and an outflow |0. The tank I of the biological reactor contains a centrally located separation chamber 4, which is delimited inside the tank I by a casing 5 and a bottom 6 of the separation chamber 4, where the casing 5 has cylindrical shape in its upper portion and conical shape, tapering downward in the lower portion, with angle between the conical portion of the casing 5 and the bottom 3 of the tank I of the biological reactor being at least 60°. Space between the casing 2 of the biological reactor and the casing 5 of the separation chamber 4 is divided by vertical partition walls A 7 and B 8 into two parts, which, on the inflow side 9, form a mechanical pre-treatment chamber U_ and, on the outflow side 10, form an aerated chamber 12. The mechanical pre-treatment chamber Π_ contains a raking basket 13 with a perforated grate 14. Under the perforated grate, there is a funnel-shaped solid bottom 25 of the raking basket 13, which, after the coarse pre-treatment, directs wastewater into a fixed and watertight connected mouth 24 of a vertical intake piping 15 used for directing activated mixture flow, i.e. the mixture of the incoming wastewater after the coarse pre-treatment and activated sludge pumped by airlift pump 16, towards the bottom of the mechanical pre-treatment chamber JJ_.

[0020] The pipe of the air-lift pump 16 for suctioning of settled sludge from the bottom of the separation chamber 4 is introduced into the intake piping J_5. A suctioning mouth 17 of the airlift pump 16 is located near the bottom of the separation chamber 4. The pipe of the air-lift pump 16 is led axially inside the vertical intake piping 15 of the activated mixture and is ended by a pump opening J_8 under the permeable bottom 14 of the raking basket 13. The intake piping 15 is ended by an opening 28 located above the bottom of the mechanical pre-treatment chamber 1_1 so that the activated mixture can freely outflow.

[0021] The partition walls A 7 and B 8 are fixed to the casing 5 of the separation chamber 4, the casing 2 and the bottom 3 of the biological reactor tank i and they span from the bottom 3 of the biological reactor tank \ to water surface inside the biological reactor, i.e. over the bottom of an discharge piping 29. Both partition walls A 7 and B 8 have window-shaped openings 19, 22 with lower edges 20, 23 of the openings 19, 22 located below the lower end of the discharge piping 29 in 5 cm depth.

[0022] At the bottom of the aerated chamber 12, there is an aeration element 2L The aeration element 21 of the pipe-shaped type is perforated along its whole length to provide fine-bubble aeration. The pipe aeration element 21 is attached to the bottom of the aerated chamber 12 in inclined position so that its part on the side of the partition wall A 7 is positioned higher than on the side of the partition wall B 8^ so that aeration on side of wall A 7 is more intense than on side of partition wall B 8. Over the part of the aeration element 2J_ near the wall A 7, the water column is lower than near the wall B 8; at lower water pressure of the water column near the wall A 7, more air bubbles escape than near the wall B 8; the bubbles in water reduce water density more near the wall A 7 than near the wall B 8, while the water tends to flow from the place of higher density to the place of lower density, therefore the water moves from the aerated chamber 12 through the opening 19 into the mechanical pre-treatment chamber Π _. and then through the opening 22 into the aerated chamber 12, which completes the circulation. It produces circulation of water around the cylindrical portion of the casing 5 of the separation chamber 4, which is limited to the upper layer of water determined by the depth of the lower edges 20, 23 of the openings J_9, 22 and also determines direction of the flow through the openings 22 and 1_9 in the biological reactor.

[0023] The lower, conical portion of the casing 5 of the separation chamber 4 contains an opening 26, through which the activated mixture flows from the aerated chamber 12 to the separation chamber 4. In front of the opening 26, there is a deflector 27 directing the flow of the aerated activated mixture caused by the aeration element 21.

[0024] The air-lift pump 6 creates a circulation circuit starting at the bottom of the sedimentation chamber 4 at the mouth 17 of the air-lift pump lj6 directing the flow upward through the pipe of the air-lift pump 16 through its mouth 18, where wastewater pre-treated by perforated grate 14 is mixed with pumped activated sludge. At the same time, the hydrodynamic force of the pumped liquid crushes gross impurities and activated sludge provides biological digestion of gross impurities. The activated mixture flows out through the funnel-shaped lower part 25 of the raking basket 13 _. through the mouth 24 to the intake piping 15, which directs the flow of the activated mixture downward to the bottom of the mechanical pre-treatment chamber J_l . The activated mixture freely flows out through the outlet 28 of the intake piping 15, then flows upwards through a layer of settled primary sludge and surplus sludge; the hydrodynamic force of the stream produced by the action of the air-lift pump 16 mixes the content of the mechanical pre-treatment chamber H thus providing optimum environment for anaerobic fermentation of organic substances which are coarse and hard to degrade and of surplus sludge in deeply anaerobic-anoxic environment with typical redox potential of -150 to -250 mV. The upflowing current of the activated mixture with low redox potential - 150 to -250 mV meets the recirculated oxic activated mixture with high redox potential +50 to +150 mV, which produces the anoxic activated mixture with redox potential of -50 to +50 mV, positively affecting reduction of nitrates, or biological reduction of nitrogen. The activated mixture then continues through the opening 22 in the partition wall 8 because horizontal, rotational movement of the activated mixture on the surface diverts flow in this direction. The activated mixture flows into aerated chamber 12, where degradation of organic substances and nitrification of ammonia nitrogen take place in aerobic conditions at redox potential of +50 to +150 mV. The activated mixture flows from the aerated chamber 2 through the opening 26 in the lower, conical part of the separation chamber's 4 casing 5 into the separation chamber 4. In the separation chamber 4, the activated sludge is separated from clear treated water by sedimentation. Clear treated water flows up in the cylindrical part of the separation chamber 4 up to the discharge piping 29, activated sludge floes settle to the bottom of the separation chamber 4^ where the suctioning mouth 17 of the air-lift pump 16 is located. The pressurized air used for aeration of the content inside the aerated chamber 2 and for driving the air-lift pump 1_6 is supplied by an air blower 33 via air pipings 30, 3J_, - A main air supply 30 from the blower 33 leads toan air manifold 32, which enables regulation of the amount of air flowing into the air-lift pump 16 and into the aeration element 21 , through the air pipings 3_1, 34 using manual air flow regulators 4J_, 42.

[0025] Degradation processes in the mechanical pre-treatment chamber Π _. produce odor-free gases (carbon dioxide and methane from degradation of organic mass and surplus sludge, nitrogen from denitrification) as well as malodorous gaseous substances including organic compounds of sulfur and nitrogen. These malodorous gases are largely absorbed by the regenerated activated sludge in the top layer of water inside the biological reactor, where the activated mixture recirculates at high oxic conditions of +50 to +150 mV.

Example 2

[0026] Biological reactor for wastewater treatment from minor sources of pollution using activation process with combined system in upflow and bio-carrier, according to the invention, Fig. 2 a, b has the tank I with the casing 2 and the bottom 3 with conical, downward tapering shape. The tank \ has the inflow 9 and the outflow K). The tank 1 of the biological reactor contains centrally located separation chamber 4, which is delimited inside the tank \ by the casing 5 and the bottom 6 of the separation chamber 4, where the casing 5 has cylindrical shape in its upper portion and conical shape, tapering downward in the lower portion, with angle between the conical portion of the casing 5 and the bottom 3 of the tank 1 of the biological reactor being at least 60°. The space between the casing 2 of the biological reactor and the casing 5 of the separation chamber 4 is divided by the vertical partition walls A 7 and B 8 into two parts, which, on the inflow side 9, form mechanical pre-treatment chamber Π_ and, on the outflow side J , form aerated chamber 12. The mechanical pre-treatment chamber JJ_ contains the raking basket 13 with perforated grate 14. Under the perforated grate, there is the funnel- shaped solid bottom 25 of the raking basket 13, which, after coarse pre-treatment, directs wastewater into the fixed and watertight connected mouth 24 of the vertical intake piping j_5 used for directing the flow of the activated mixture, i;e. the mixture of the incoming wastewater after the coarse pre-treatment and the activated sludge pumped by the air-lift pump 16, towards the bottom of the mechanical pre-treatment chamber IT .

[0027] The piping of the air-lift pump 6 used for suctioning the settled sludge from the bottom of the separation chamber 4 is led perpendicularly into the raking basket 13 through the funnel- shaped bottom 25 of the raking basket JL3 so that the mouth J_8 of the air-lift pump 16 is located just below the perforated grate J_4 next to the mouth 24 of the activated mixture intake piping 15.

[0028] At the bottom of the aerated chamber 12, there is the aeration element 2 L The aeration element 21 of the pipe-shaped type is perforated along its whole length to provide the fine- bubble aeration. The pipe aeration element 2J_ is attached to the bottom of the aerated chamber 12 in the inclined position so that its end on the side of the partition wall A 7 is positioned higher than the end on the side of the partition wall B 8 so that aeration on side A 7 is more intense than on side B 8. Over the part of the aeration element 2J _. near the partition wall A 7, the water column is lower than near the partition wall B 8; at lower water pressure near the partition wall A 7, more air bubbles escape than near the partition wall B 8; the bubbles in the water reduce water density more near the partition wall A 7 than near the partition wall B 8 while the water tends to flow from the place of higher density to the place of lower density, therefore the water moves from the aerated chamber J_2 through the opening 19 into the mechanical pre-treatment chamber JJ _. and then through the opening 22 into the aerated chamber 12, which completes the circulation. It produces circulation of water around the cylindrical part of the casing 5 of the separation chamber 4, which is limited to the upper layer of water determined by the depth of the lower edges 20, 23 of the openings 19, 22 and also determines the direction of the flow through the openings 22 and 19 in the biological reactor.

[0029] The aerated chamber 12 holds a bio-carrier 35 which serves as the carrier of the growth microbial cultures of the activation sludge. The bio-carrier 35 is made of plates of 3-dimensional filtration material. The bio-carrier 35 is fitted onto the casing 5 of the separation chamber 4. The role of the bio-carrier 35 is to provide amount of active biomass sufficient to both, the reduction of organic pollution and increasing the effectiveness of the nitrogen reduction by nitrification and denitrification processes.

Example 3

[0030] The biological reactor for wastewater treatment from minor sources of pollution using activation process with the sludge in upflow, according to the invention, Fig. 3 a, b has the tank i with the casing 2 and the bottom 3 with the conical, downward tapering shape. The tank i has the inflow 9 and the outflow 10. The tank i of the biological reactor contains centrally located separation chamber 4, which is delimited inside the tank I by the casing 5 and the bottom 6 of the separation chamber 4, where the casing 5 has the cylindrical shape in its upper portion and conical shape, tapering downward in the lower portion, with angle between the conical portion of the casing 5 and the bottom 3 of the tank i of the biological reactor being at least 60°. The space between the casing 2 of the biological reactor and the casing 5 of the separation chamber 4 is divided by the vertical partition walls A 7 and B 8 into two parts, which, on the inflow side 9, form the mechanical pre-treatment chamber Π_ and, on the outflow side 10, form the aerated chamber 12. The mechanical pre-treatment chamber 1_1 contains the raking basket 13 with the perforated grate 14. Under the perforated grate, there is the funnel-shaped solid bottom 25 of the raking basket ±3, which, after the coarse pre-treatment, directs wastewater into the fixed and watertight connected mouth 24 of the vertical intake piping 15 used for directing activated mixture flow, i.e. the mixture of the incoming wastewater after the coarse pre-treatment and activated sludge pumped by the air-lift pump 16, towards the bottom of the mechanical pre- treatment chamber JJ_.

[0031] The piping of the air-lift pump 16 used for suctioning the settled sludge from the bottom of the separation chamber 4 is led perpendicularly into the raking basket 13 through the funnel- shaped bottom 25 of the raking basket jJ3 so that the mouth J_8 of the air-lift pump 1_6 is located just below the perforated grate 14 next to the mouth 24 of the activated mixture intake piping 1_5.

[0032] At the bottom of the aerated chamber 12, there are aeration elements A 36 and B 37 as shown in Fig. 2a. The aeration elements A 36 and B 37 are of the pipe-shaped or plate-shaped type. The aeration elements A 36 and B 37 are mutually interconnected by a connecting-up air piping 40, attached to the bottom of the aerated chamber 12 so that the aeration element A 36 near the wall A 7 is positioned higher than the aeration element B 37 on the side of the partition wall B 8 in order to achieve more intense aeration on the side of the partition wall A 7 than on the side of the partition wall B 8. Above the aeration element A 36 near the wall A 7, the water column is lower than above the aeration element B 37 near the partition wall B 8; at lower pressure of water column near the wall A 7, larger amount of air in the form of air bubbles escape than near the wall B 8; the bubbles in the water reduce water density more near the partition wall A 7 than near the partition wall B 8, while the water tends to flow from the place of higher density to the place of lower density, therefore the water moves from the aerated chamber 12 through the opening 19 into the mechanical pre-treatment chamber U_ and then through the opening 22 into the aerated chamber 12, which completes the circulation.

[0033] At the bottom of the aerated chamber J_2, there are aeration elements A 36 and B 37 as shown in Fig. 2b. The aeration elements A 36 and B 37 are of the pipe-shaped or plate-shaped type. The aeration elements A 36 and B 37 are attached to the bottom of the aerated chamber 12 at the same height. Each of the aeration elements A 36 and B 37 has its own supply of pressurized air 38, 39, which are connected to the air manifold 32 with the air flow regulators 42, 43. The air flow regulator 43 for the aeration element A 36 is set in the way that the conveyed amount of the air is higher than that of the air flow regulator 42 into the aeration element B 37; near the partition wall A 7, more air bubbles escape than near the partition wall B 8; the bubbles in the water reduce the water density more near the partition wall A 7 than near the partition wall B 8 while the water tends to flow from the place of higher density to the place of lower density, therefore the water moves from the aerated chamber 12 through the opening 19 into the mechanical pre-treatment chamber JJ and then through the opening 22 into the aerated chamber 12, which completes the circulation.

The Industrial Applicability

[0034] The biological reactor according to the present invention can be used for treatment of wastewater from various minor sources, especially family houses and other objects for living, services and recreation.