MX2010013707A - Device for the biological purification of a high rate of wastewater and process for purifying the same. - Google Patents

Abstract

The present invention refers to a device and process for the biological treatment of domestic effluents which may be used in discharge points since it is a high rate process, where the activated sludge is maintained as a bio-film adhered to supports and not as suspended flocs.

Description

DEVICE FOR THE BIOLOGICAL PURIFICATION TO HIGH WASTEWATER RATE AND PURIFICATION PROCESS OF THEM.

Field of the invention.

The present invention relates to devices or apparatuses designed for the processes of biological treatment of domestic effluents at high rate through contact between the multispecies microbial population, "activated sludge" immobilized on inert supports and in a space with controlled mixing; that is, to the reactors containing solid supports with adhered bio-film and immersed forming a fluid bed. As well as the wastewater purification process for which the device was designed.

Background.

The traditional treatment of activated sludge consists of three operations and one or two unit processes. The first unitary operation is a physical separation of the flow of waste water and by density difference of inert liquids, a flotation, such as mineral fats, as well as inert solids, a sedimentation. This operation carried out in a container called "desarenador", is followed by the biological oxidation process of organic matter, called "chemical oxygen demand or COD", carried out in a bio-reactor with air in suspension, called "aerator" "and carried out by a population of a microbial consortium called" activated sludge ", whose proliferation is proportional to the reduction of COD. This microbial growth must be separated from the flow of the water already treated, by means of the unit operation of flocculation of the sludge, in a third container, called a settler. The sludge is removed by the bottom of the settler and a part recirculated to the aerator, while the flow of the treated water and no sludge in suspension is transferred to the third filtration operation through a layer of inert and porous material. It is optional that the water be oxidized chemically, usually with chlorine, in a last unitary process. Since the hydraulic retention time of the water in the aerator is of the order of 10 hours and the residence time in the settler is even greater, the dimensions of the aerator and the settler are very large.

This disadvantage has been solved by means of the procedure of fixing activated sludge in an inert and fixed surface, as is the case of the runoff filters, or in an inert and moving surface, the process called biological discs. The first economic process, but inefficient and little controlled and the second one has disadvantages of the energy costs associated with the continuous movement of the rotating discs, as well as the associated mechanical maintenance requirements, Rusten B. et al., 2006; Aquacultural Engineering 34: 322-331.

The process of the Bio-film Reactor in Moving Bed ("Moving Bed Biofilm Reactor or MBBR", EP 0 575 414 B2, 1991) has been developed and patented. Its basic principle is to fix the sludge on the surface of supports of a material inert, whose density is slightly lower than that of water and with a uniform shape and dimensions, which has a large surface area with respect to its mass, these bodies float within the residual water inside the vessel that is mechanically agitated and aerated by blowers. With the fixed sludge they are constricted inside the reactor by a sieve at the exit of the reactor.The ratio of support volume is close to half the volume of the MBBR.

The reactor is a cylinder served by a feed and a side grid that discharges the fluid preventing the exit of the solid supports. The reactor is supplied with oxygen by injecting compressed air by means of a disperser or a battery of them into the bottom of the container, as well as by a mechanical stirrer to mix, cause turbulence and therefore improve the transfer of oxygen to the liquid of reaction.

In the patent EP 1 340 720 A1, 2001, the inventors have also protected the supports that are called "Kaldnes carriers" in terms of their shape of cylindrical sections with the interior space crossed by solid bars in the form of a grid or a network of small holes. It is also protected that the material is a polymer specially designed to have a real polymer density of 0.98 g / cm3.

On the other hand the patent US 5,593,893 A (1997) protects support materials constructed with a mixture of poly-olefin type polymers, for example; polyethylene and polypropylene, mixed in a proportion of 50 to 95% with cellulosic material of vegetable origin, corn fibers, oat husk, in a proportion of 5 to 50%, by weight. The patent states that the product is kneaded and extruded. The document does not mention the density of the composite film nor its dimensions.

Another background is the patent EP 0 667 319 (1995) which mentions support particles for the growth of microorganisms made with a polymeric material whose density is "less than 1, preferably less than 0.3g / cm.sup.3 In the same way, in the patent JO 1 1000166 (1999) relating to polymeric particles, composed of hydrophobic material such as polyethylene, polypropylene, polyvinyl chloride, polystyrene or polyethylene terephthalate or an epoxy resin, with a specific gravity of 0.95-1.05.

Brief Description of the Drawings.

Figure 1 shows the components of the bio-reactor device as a whole, where: (1) carcass of domestic wastewater; (2) valve; (3) bio-reactor feeder; (4) bio-reactor water outlet pipe; (5) bio-reactor; (6) ejector; (7) concentric cylinder; (8) solid spheres of composite materials; (9) continuous pump centrifuge; (10) suction leg equipped with a pichancha; (11) recirculation flow control valve; (12) Venturi valve; (13) pipe.

Brief description of the invention.

The present invention relates to a device and process of biological treatment of domestic effluents that can be used at the point of discharge as it is a high rate process and which keeps the "activated sludge" as a bio-film adhered to supports and not as flocs in suspension, as well as the device that allows the best performance of said process. The device consists of a cylindrical container of variable volume whose dimensions retain a height ratio equal to twice its diameter. Inside it is positioned a concentric cylindrical whose lower edge does not reach the bottom but allows the passage to the fluid and solid supports that float in the fluid, and whose diameter is such that it allows the passage to at least two of the mentioned supports. Its upper edge remains submerged in the fluid.

A commercial piping circuit, for example of polyvinyl chloride (PVC) served by a commercial pump of continuous use and discharge of at least 10 L / min, sucks at one end of the circuit and through a pichancha the water to be treated and leads it through a Venturi valve in whose throat is a pipe open to the atmosphere. The recirculation flow is such that the Venturi valve tube sucks the air at a convenient rate for oxygen transfer. The gas / liquid emulsion formed in the discharge of the Venturi valve is led through the final part of the pipe to an ejector placed at the bottom of the concentric cylinder and in a central position.

The discharge of the gas / liquid emulsion causes an upward current in this area of the reactor, elevator zone, to the upper space between the upper edge of the inner cylinder and the surface of the liquid column. In that space the bubbles escape into the atmosphere and the liquid only, denser than the emulsion, circulates downward in the space between the inner cylinder and the reactor wall, downpipe area. This internal recirculation promotes good mixing and efficient oxygen transfer.

The reactor is also served by gravity from a collector collector of a wastewater feed stream used domestically, at a regulated rate to keep the water in treatment for three or four hours of hydraulic retention. The reactor at the height of the liquid that corresponds to the volume of design operation has a discharge equipped with a mesh that prevents the exit of the solid supports that are immersed in the water under treatment.

In the treatment water there are solid supports composed of commercial materials of such size that the weight-size ratio results in a density for the composite solid similar to that of water. These solid supports are colonized by a microbial consortium known as: "activated sludge"; able to biologically oxidize organic substances that are technically known as "Biological Oxygen Demand". The microbial consortium is propagated by the consumption of organic material, and grows attached to the solid support predominantly, and not as flocs in suspension, as is the case of the traditional treatment of active sludge.

The colonization of the solid supports achieves that the concentration of active cellular material in the reactor is greater than in the traditional "active sludge" process and prevents it from leaving with the treated effluent, avoiding the need for the separation operation by sedimentation through of a valve and the corresponding equipment. The mixing and transfer of oxygen through recirculation through a Venturi valve simplifies the operation of the process Detailed description of the invention.

With reference to figure 1, which shows the device object of the present invention and whose components and operation are described below: The number (1) illustrates the waste water tank, where it is stored. Its discharge is regulated by a valve (2) before feeding (3) the bio-reactor (5) inside which a concentric cylinder (7) is firmly positioned. A recirculation circuit starts with a suction leg (10) equipped with a pichancha on its end. The suction of the water to be treated is driven by a continuous centrifugal pump (9) that discharges through a recirculation flow control valve (11) and through a Venturi valve (12) that sucks air and emulsifies it with the water, whose emulsion is conducted through the pipe (13) to the base of the inner cylinder and sprinkled by the ejector (6) in an upward direction.

Within the fluid, solid spheres of composite materials (8) are immersed in such art that their density is similar to that of water and they are previously colonized by a bio-film of the microbial consortium known as "activated sludge". Once the wastewater has been treated, it is dislodged through the pipe (4) placed at the upper end of the bio-reactor.

The purpose of the device is to carry out the biological process for the treatment of wastewater, said device consists of the following components: of a cylindrical container, of inert and impermeable material, whose height is at least twice its diameter and is occupied in 80% for residual water in treatment. A concentric inner cylinder is fixedly positioned so that its bottom edge is 4 + 1 cm. from the bottom of the reactor and whose diameter is approximately 9 + 1 cm. smaller than the internal diameter of the cylindrical container and its upper edge is below the surface of the liquid.

The reactor is served by a recirculation circuit, made of flexible and light material, for example, of polymer material of the polyvinyl chloride (PVC) type and the like, with a pump that sucks the water to be treated and conducts it through a Venturi valve, whose throat is connected to a pipeline open to the atmosphere and in turn sucks air. The resulting emulsion is conducted via the circuit to an ejector positioned at the bottom and in a central position. In the suction of this circuit of recirculation a pichancha is placed that avoids the suction of any solid.

Another component of the device consists of spherical solids of 1.8 + 0.4 cm. of approximately diameter, of composite material to have a density similar to or lower than that of water and that has been previously colonized by the microbial consortium of "activated sludge" and that are immersed in the bioreactor in the water try.

Also a subject of the present invention is a biological water treatment process, which consists of the following stages: First stage: Domestic waste water is collected in a regulation and mixing station, from which by gravity and through a duct equipped with a flow control valve that discharges it at an appropriate expense to achieve a hydraulic retention time in the following stage from 2 to 6 h, preferably from 3 to 4 h.

Second stage: The water is received in a bio-reactor vessel for ascent by air and with continuous recirculation of the water to be treated, in which the water oxygenated by an emulsion of air bubbles in the water is mixed by the recirculation of the water to achieve a homogeneous concentration in the bioreactor, as well as to achieve a homogeneous suspension of solid spheres of support for the growth of a multispecies population known as "activated sludge" and it is possible to contact the organic material and oxygen with the attached microbial population to solid supports. In this stage, the biological oxidation of most of the organic material content of the wastewater is performed, measured as the concentration of the "Chemical Oxygen Demand" (COD). The reduction of 90% of the COD of a typical domestic wastewater is achieved between 2 to 6 hours of hydraulic retention time in the reactor, preferably 3 to 4 hours of hydraulic retention time.

As part of this stage the recirculation of a portion of the water to be treated is carried out in a circuit that sucks the water from the reactor by means of a pump and makes it flow through a valve that achieves by this same the aspiration of ambient air and its dispersion in the water in the recirculation circuit, forming an air / water emulsion, which is conducted to the bottom of the bioreactor and injected in an upward direction, achieving the mixing of the air bubbles in the water to be treated, as well as a directed flow in separate sections of the bioreactor, as will be described in the section of the device, achieving ascending flows, elevator zone and descenders, area of the downpipe. This circuit has a device in the suction that prevents the entry of solid supports to the recirculation circuit.

Third Stage: After a period of 2 to 6 h, preferably 3 to 4 h, the water drains from the bio-reactor, with a reduction of 90% of its original COD load and can be discharged to the metropolitan drainage network

Claims (13)

1. A device for the biological purification at a high rate of wastewater, characterized in that it comprises a carcase (1) of domestic wastewater, where it is stored; a discharge valve (2); supply pipe (3); a bioreactor (5), comprising a concentric cylinder (7); a recirculation circuit (10); a continuous centrifugal pump (9); a recirculation flow control valve (11); a Venturi valve (12); pipe (13); an ejector (6); a plurality of solid spheres of composite materials (8); and wastewater discharge pipe (4).

2. The device of claim 1, characterized in that the cylindrical container is of inert and impermeable material, and whose height is at least twice its diameter and is occupied by 80% by residual water in treatment.

3. The device of claim 1, characterized in that the concentric inner cylinder is fixedly positioned in such a way that its lower edge is 4 + 1 cm. from the bottom of the reactor and whose diameter is approximately 9 + 1 cm. smaller than the internal diameter of the cylindrical container and its upper edge is below the surface of the liquid.

4. The device of claim 1, characterized in that the reactor is served by a recirculation circuit, made of flexible and light polymeric material, which comprises a pump that sucks the water to be treated and conducts it through a Venturi valve, whose throat is connected to a pipe open to the atmosphere and in turn sucks air.

5. The device of claim 4, characterized in that the resulting air / liquid emulsion is conducted through the circuit to an ejector placed at the bottom of the outer cylindrical container and the suction of the liquid in said recirculation circuit is effected by a device that prevents suction of any solid.

6. The device of claim 1, characterized in that the plurality of solid spheres is 1.8 + 0.4 cm. of approximately diameter, and are made of composite material whose density is similar or less than that of water

7. The device of claim 6, characterized in that said plurality of solid spheres has been previously colonized by the microbial consortium of "activated sludge" and that are immersed in the bioreactor within the water to be treated.

8. A process for the biological treatment of wastewater of high rate, characterized because it consists of three stages: a) First stage: capture the domestic waste water a regulation and mixing station; b) Second Stage: receiving and treating the water in the bio-reactor vessel according to claim 1. c) Third Stage: evacuate the bioreactor after a lapse of 2 to 6 hours, preferably 3 to 4 hours.

9. The process according to claim 8, characterized in that said station maintains a discharge at an appropriate expense to achieve a hydraulic retention time in the next stage from 2 to 6 h, preferably from 3 to 4 h.

10. The process according to claim 8, characterized in that the water is oxygenated by an emulsion of air bubbles in the water, and is mixed by the recirculation of water.

11. The process according to claim 8, characterized in that the COD of the domestic waste water is reduced to approximately 90% of its initial value, within a period of between 2 to 6 h of hydraulic retention time in the reactor, preferably from 3 to 4 hours. h of hydraulic retention time.

12. The process according to claim 8, characterized in that in the second stage the recirculation of a portion of the water to be treated is carried out in a circuit that sucks the water from the reactor by means of a pump and makes it flow through a valve that sucks air environment and dispersed in the water in the recirculation circuit, forming an air / water emulsion, which is conducted to the bottom of the bioreactor and injected in an upward direction.

13. The process according to claim 12, characterized in that the recirculation circuit has a device in the suction that prevents the entry of solid supports to said circuit.