DK143397B - METHOD AND BIOLOGICAL FILTER FOR WASTE TREATMENT - Google Patents

Description

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6 a «PRESENTATION WRITING ου 143397 B

DIRECTORATE OF THE PATENT AND TRADEMARKET SYSTEM

(21) Application No. 4924/72 (51) f ^ ci.3 C 02 F 3/06 (22) Filing day 5 · Oct. 1972 (24) Race day 5 · Oct. 1972 (41) Aim. available 27 · May 1973 (44) Submitted 17 · Aug. 1981 (86) International Application No. ~ (86) International Filing Day - (85) Continuation Day "(62) Master Application No. -

(30) Priority 26 Nov. 1971, 202489, US

(71) Applicant ECODYNE CORPORATION, Chicago, US.

(72) Inventor Carl E. Burkhead, US.

(74) Associate Company Chas. Hude.

(54) Process and biological filter for the treatment of wastewater.

The present invention relates to treatment of wastewater containing waste products, and more particularly to the invention a method utilizing aerobic microbial growth of solid-Q substrates for the biological oxidation of waste products and of the species set forth in the preamble of claim 1, as well as a biological filters to perform the procedure.

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A large number of methods and plants are known for treating wastewater containing biodegradable wastewater to obtain clear and harmless wastewater that can be returned to nature. The attention that has been directed towards the deterioration of our ecology in recent years has given priority to the development of better waste treatment systems than those previously known.

Fundamentally, biological wastewater treatment is a process in which, during metabolism, microorganisms process waste products and produce gaseous and soluble molecular end products and, moreover, bacterial cells. The speed and efficiency of the process is supported by increasing the number of bacterial cells or the available growth to perform the metabolism. The concentration and preservation of organisms in the system is achieved by known plants by several physical or biological methods which include flocculation, settling and providing large surface areas for bacterial growth.

Two known methods for treating biodegradable waste products are by an activated sludge system or by the sand filter process. In an activated sludge system, the organisms are brought into contact with the waste material by mixing wastewater with sludge, i.e. a solid concentration of organism fluff to form the liquid mixture and then subject to vigorous stirring while introducing large volumes of atmospheric air. In sand filter systems, the biological organisms are not present or submerged in an aqueous substrate, but are present as bare growth on the surface of suitable ground objects in contact with the atmosphere, and the reaction is produced by the waste material flowing in relatively thin streams in direct contact with the biological sludge. .

From the specification of United States Patent 3,293,174 such a system is known which works by the sand filter method. It comprises a means for carrying a bed of a slowly passable filter substrate, which includes a mass of randomly spaced apart pieces of foamed inactive polymeric material and a means for sprinkling a liquid and a gaseous substance over the bed so that it can slip through this. In the disclosed embodiment, only a single pass through the substrate column has been disclosed and no means have been provided to recycle the wastewater through the substrate column. In order to obtain a sufficiently clarified and purified liquid, it will be necessary to allow the waste water to pass through a number of such purification units.

Combined or hybrid systems are also known in which both activated sludge and sand filter are used. In one example, 19 o o n r * h o O Li / vertically oriented flat asbestos bonding plates are used as touch surfaces for aerobiological cultures. Air is blown under the plates through openings in a bottom grid to supply the required oxygen. A similar system is known from U.S. Pat. No. 3,371,033, according to which a series of coiled or parallel-mounted rows of thread-like material form a plurality of substantially vertical flow paths, and the current along the individual plates is isolated from all the others. streams, thereby preventing a thorough and homogeneous mixture of wastewater. This patent also shows spaced contact zones within the same housing and where water is drawn into a zone located between the two contact zones for recycling to the lower zone. The sedimentation zone is so close to the recirculation flow path that it seems as if sedimented sediment would be recirculated.

It is an object of the present invention to provide a method of treating biodegradable waste products which is more economical than the prior art and which produces a better quality of purified wastewater.

This object is met by the fact that the method mentioned in the preamble is characterized by the characterizing part of claim 1. By means of the homogeneous mixing of the wastewater over and throughout the volume of the mixing zone, and by constantly dividing and collecting the stream by means of the many individual retained substrate elements down through the columns of the mixing zone, a large surface area is obtained, whereby the waste water comes into contact with the all the aerobic microbial growth on the substrate, as well as ensuring a simple sludge extraction and drainage of purified wastewater from the side of the house and an efficient and simple repeated recirculation as well as by providing in the basin under the column of retained substrate a settling zone to absorb and collect solid From the mixing zone, a simple opportunity for the absorption of separated solid is ensured.

The characterizing part of claim 2 ensures that the residual solid is not resuspended by the recirculating liquid. A simple way of removing the precipitated solid is given in the characterizing part of claim 3.

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With the aid of the characterizing part of claim 4, it is ensured that both oxidation and even distribution of the oxidized wastewater only require a very limited volume.

In order to carry out the process according to the above claim, in claim 5, an appropriate biological filter for purifying wastewater is provided, which plant is very simple in design and at the same time is space-saving and thus inexpensive to manufacture and easy to maintain.

By means of the characterizing part of claim 6, it is obtained that a sedimentation basin is formed in the housing in a simple manner, whereby the sedimentation, thanks to the tapered shape of the basin, can essentially take place in a zone outside the flow path of the waste water.

The surface stirrer disclosed in the characterizing portion of claim 7 is a simple and inexpensive means for securing the oxidation and dispersion across the top of the mixing zone.

By designing the outlet as set forth in the characterizing portion of claim 8, it is ensured that the effluent passing through the overflow is clean and stable and of a quality so that it can be fed to a stream or to the ground through a conduit.

In the method and filter of the present invention, the sludge age, i.e. the length of time the solid remains on the substrate before being released is much longer than in a normally activated sludge system. It is possible to approach the theoretical oxidation limit by the method and filter according to the invention. It has also been found that the plant has excellent absorption capacity at sudden loads.

The method and the biological filter according to the invention are explained in more detail below on the basis of the drawing, in which fig. 1 is a schematic sectional view of a reactor system in accordance with the present invention; and FIG. 2 is a plan view of the system of FIG. 1 In FIG. 1 shows a biological filter 10 with an outer housing 12 which is made of metal sheets or similar materials and has a corrosion resistant inner surface. In the embodiment shown, the housing 12 is designed as a cylinder, but other forms can be used in the present invention. An inlet conduit 14 leads into the housing 12 near the upper end of the housing.

Slurry or industrial wastewater containing biodegradable waste products is introduced into filter 10 through inlet 14. The waste products may be in raw form or may have previously been treated, such as by coarse screening, comminution, removal of coarse sand grains and / or precipitation.

The housing has an outlet conduit 16 for discharging effluent after treatment and clearance in the filter 10. A control overflow and a waste water box 18 are - seen in the flow direction - arranged after the outlet 16. The effluent passing through the overflow 18 is clean and stable and with a quality so that it can be passed to a stream or to the ground through a conduit 20.

The housing 12 has a mixing zone with a top 22 slightly below the inlet 14 and a bottom 24 at the bottom of the housing 12. In the illustrated embodiment, the bottom 24 of the mixing zone is a perforated metal base plate in the housing 12. The metal base plate may be formed from a known, rolled metal grate. , a corresponding lattice or material.

Except for a central flow channel 26 discussed below, the entire mixing zone volume between the top 22 and the bottom 24 is occupied by a retained substrate material 28. The retained substrate 28 may consist of many different materials with a large surface area relative to the volume, low resistance to liquid flow, i.e. have a high porosity and a surface susceptible to aerobic microbial growth. Suitable for example. a stacked plastic package consisting of polypropylene "Flexirings". In a laboratory test model of the system according to the invention, "Flexirings" were used with one

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nominal size of approx. 16 mm and with a surface area of approx. 9 m per 0.03 m. In a prototype of the apparatus according to the invention, where the mixing zone had a volume of 1.56 m, 89 mm 2 * 7 "Flexirings" with a surface area of 2.6 m per m 2 were used. 0.05 no effective.

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Those skilled in the art will see that other species of packing substrates such as Raschig and Pali rings and saddle-type gaskets (e.g., Berl) can be used without departing from the scope of this invention. The retained substrate 28 may also be composed of materials other than plastics, provided that these materials are non-toxic to the microbes and are otherwise susceptible to aerobic microbial growth on the surface.

The openings in the perforated bottom 24 of the mixing zone may, of course, not be so large as to allow the individual elements of the substrate 28 to pass, but they should be as large as possible in relation to this limitation.

As mentioned, a flow channel 26 occupies the median region of the mixing zone and extends between its top 22 and bottom 24. The flow channel 26, which may be a cylindrical conduit, forms parts of a recirculation flow path which includes the retained substrate 28 in the mixing zone. As shown, the flow channel 26 is conveniently located along the center axis of the housing 12 *, although the channel may be located in other areas inside or outside the housing 12.

According to the present invention, the retained substrate 28 in the mixing zone is immersed in the effluent flowing into the system through the inlet 14. Biological oxidation of the organic waste products in the effluent is effected by continuous circulation of the effluent through the substrate and by continuous air supply to the effluent in such manner. that a very active aerobic microbial growth on the retained substrate 28 throughout the volume of the mixing zone is promoted. It is an important aspect of this invention that bacterial growth adheres to the retained substrate and that the amount of flocculent or suspended aerobic bacterial cultures is reduced to a minimum. In other words, excessive stirring or turbulence in the mixing zone must be avoided, which may cause bacterial growth to be stripped or broken by the retained substrate 28.

It is also important to achieve effective utilization of the entire volume of the retained substrate 28, and therefore the circulation system must be designed to promote homogeneous mixing and to exclude spaces without circulation or dead pockets in the mixing zone 28.

According to this invention, the suspended solid is suspended in the waste water even by sludge on the retained substrate 28. The solid remains on the substrate until it is released as inactive residual solid, thereby providing a long period of time for the microbes to oxidize and stabilize the organic matter. substances. In the present filter and method, the sludge age, i.e. the length of time the solid remains on the substrate before being released is much longer than in a normally activated sludge system. It is possible to approach the theoretical oxidation limit by the method and plant of the present invention. It has also been found that the filter has an excellent capacity for absorbing sudden loads.

It has been found that the aeration, distribution and circulation functions can be completed in a very efficient and satisfactory manner by means of a mechanical surface aeration means JO installed at the top of the central flow channel 26 ». Such an aerator draws the wastewater upwardly through the flow channel 26 and aerates the raised fluid by means of rotating vane blades which break the wastewater into small particles while simultaneously discharging the wastewater radially outwardly with a generally uniformly shaped pattern over the top 22 of the mixing zone.

The mechanical surface aeration produced by the aerator 30 produces less shear forces and agitation in the volume of the mixing zone than other technical means such as diffuse oxidation.

It will be appreciated that other aeration techniques or other aeration units may be used in place of the aerator 30 without departing from the scope of the present invention, provided that the aforementioned criteria are present. For example, an trachea located centrally in the flow duct 26 and with the opening facing downward at a point somewhere in the duct 26 may be used. In this arrangement, a deflection shield is arranged at the top of the duct 26 * at the site of the vent means 30, thereby deflecting the waste water flow which is displaced upward by the air which is separated from the central pipe.

In the embodiment shown, the rotating vane blades 30 of the aerator 30 are driven by a motor unit 32 which rests on a bridge 35 which is attached to opposite side walls of the housing 12. The motor unit 32 and the rotary vane blades 30 of the aerator 30 are connected by means of a drive shaft 34.

Generally, the rotor portion of the vent means 30 is mounted at the surface of the wastewater and so that the vane blades are partially submerged. To avoid possible collisions with the substrate 28, a coarse holding mesh can be placed at the top of the mixing zone. Furthermore, it is preferred that the substrate 28 has a density that is at least slightly greater than the water density, thereby minimizing the risk of the substrate coming into contact with the blade blades.

In a preferred embodiment of the invention, a settling zone is further provided within the housing 12. This settling zone is disposed at the perforated floor forming the bottom zone of the mixing zone 24. A tapered settling pool 38 closes the bottom of the housing 12. The conical basin 38's sidewalls form an angle of approx. 60 ° with the vertical axis of the cone, ensuring that the separated material flows towards the cone's apex. A sludge drain 40 leads from the downwardly cone tip of the basin 38. A valve 42 is inserted into the tube 40 and is opened periodically to remove the collected sediment. Generally, the precipitate is present as essentially inert residual solid which is precipitated from the mixing zone. The extracted precipitate is not recycled during the process, but is removed in any simple and known manner.

The lower end of the flow channel 26 rests on the perforated bottom of the mixing zone 24. The tip of the basin 38 is positioned far enough below the bottom 24 that the recirculating effluent does not flush the bottom of the basin and return the precipitate to the system. In this connection, the system is operated by maintaining a long retention period on the retained substrate 28. Solids introduced through the inlet 24 are removed together with the soluble contaminants by the microorganisms growing on the retained substrate 28. The solid is periodically released from the retained substrate 28 to be deposited in the settling basin 38. The treated solids - both the non-biodegradable and the microbial - have better deposition properties than the influent solid due to their larger size and density, which is a direct result of the long microbial retention period provided by the retained substrate 28.

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A laboratory study of the method and plant of the present invention was performed using a model 40-100 "VIRTIS" constant temperature fermentation wakes as a reactor unit. The reactor was operated at ambient temperature ranging from 21 ° C to 27 ° C. The capacity of the filter was 10.5 liters without the retained substrate 28, the tube 26, the perforated bottom 24, and other submerged components. The filter capacity for effective liquid retention with the submerged components was 9.0 liters. The inflow was for a special aeration time based on the effective holding capacity of the reactor, i.e. 9.0 liters.

The retained substrate 28 used in the laboratory model was the polypropylene "Flexirings" mentioned above. A total of 1500 units of laboratory size "Flexirings" were used, i.e. nominal size of 15.9 mm. The average weight of the dry substrate was measured at 0.5060 g. The volume occupied by the 1500 units was approx. 900 ml. The substrate described is inactive, does not bend under normal load and can be subjected to a maximum temperature of 127 ° C without any detrimental effect. The 15.9 mm substrate pieces yielded a surface area of 9.2 m. 0.03 No. The substrate referred to is known per se and has previously been used in drainage filter systems.

During the studies, mechanically treated sewage water from a small municipal sedimentation plant was pumped to the model filter unit using a model RRp pump manufactured by Fluid Metering, Inc. To maintain one's pump speed, a known apparatus for maintaining constant pressure height was inserted between the feed tank and the inlet port of the pump. . The wastewater was pumped to the biological filter continuously and at a predetermined rate, thereby providing the desired aeration time. Complete mixing and aeration were provided by magnetically driven flat turbine vanes located in the central flow channel 26.

First, the filter unit was operated with a 12 hour aeration period for 127 days. Studies were performed for 26 consecutive days with 6 hours of aeration. During the retention time of 12 hours, the average chemical oxygen demand (OCX) for the effluent effluent was found to be 202 mg / ml. and the COD of solution in the inflow was found to be 111 mg per liter. liter. The average total COD in the effluent effluent was found to be 10 mg. liter. The total COD and soluble COD in the effluent effluent were essentially the same due to the very small amount of suspended solids in the effluent.

During the 6-hour retention period, the average COD of the material supplied was 508 mg / ml. and the average COD of the soluble was 240 mg per liter. liter. The average COD in the effluent was 50 mg per day. liter.

More limited studies were conducted on the biological oxygen demand (BOD). During the analysis period, the average of the total BOD in the feed material was 98 mg per ml. and the BOD of solution averaged 55 mg per liter. liter. With the retention period of 6 hours, the average of BOD in the feed material was 174 mg per day. while the average BOD of the solution was about 88 mg per liter. liter.

With the retention period of 12 hours, the suspended solids in the inlet water varied between 10 and 157 mg per liter with an average of 65 mg per liter. liter. The amount of suspended solids in the effluent was usually between 0 and 5 mg per day. liter with an average of 5 mg per liter. liter. About 80% of all suspended solids were volatile. With the retention period of 6 hours, the average amount of suspended solids in the wastewater supplied was 121 mg / ml. per liter and the amount of suspended solids in the effluent averaged 14 mg per liter. liter.

It was found that with the 12 hour retention period, almost complete nitration occurred with appropriate mixing and presence of sufficiently dissolved oxygen. The pH was measured at regular intervals in the inlet and outlet water and ranged between 7.1 and 7.8. Occasionally, the dissolved oxygen was measured in the mixed fluid in the central flow channel. The amount of dissolved oxygen was between 1.5 and 2.4 mg per ml. liter.

Microscopic examination of biological solid on the retained substrate revealed that the microbes were identical to those found in sludge systems activated in a normal manner. With the retention period of 12 hours, higher forms of animal life in the biological solid existed on the retained substrate than with the 6 hour study.

Claims (5)

11 143397 Throughout the study, the filter produced an exceptionally good quality of waste liquid, expressed as a percentage of removed material, and the effluent concentration of COD, BOD and suspended solids. With the retention period of 12 hours, the filter was able to remove 85% of total COD, 95% BOD and 95% of total suspended solids. With the retention period of 6 hours, the plant removed 85% COD, 86% BOD and 88% suspended solids. Patent claims. A method of treating wastewater containing biodegradable waste products in a reactor unit of the kind including a closed housing containing a single column of a retained substrate composed of a plurality of individual elements stacked freely and randomly on top of each other in the housing and individually has a predetermined large surface area to volume ratio and can thereby absorb aerobic microbial growth, and which cooperatively have a predetermined large porosity to provide a small resistance to flowing fluid, characterized in that it comprises the working steps of wastewater supply. the reactor at the top of the column of retained substrate in sufficient quantity to fully keep the column immersed, which column is limited at the top and bottom and constitutes a mixing zone that the waste water is oxidized at its surface at the top of the column and distributed uniformly and evenly over the surface of it substrate retained in the column by pumping action to circulate the oxides and distributed wastewater along a downward flow path through the mixing zone such that the wastewater stream is divided into a large number of individual streams that repeatedly coalesce and randomly divide during homogeneous mixing throughout the mixing zone and during intimate contact between the wastewater and the substrate, during which the turbulence occurs. controlled and maintained below the level of detachment of aerobic microbial growth from the retained substrate, and with the supply of sufficient oxygen to promote the growth of the substrate, that the wastewater passing through the column flows through an under-column basin to flow upward through a flow channel and is repeatedly recycled through the oxidation, distribution and pumping stages during homogeneous mixing of the entire amount of wastewater throughout the entire volume of the column retained substrate, which recycling includes returning the wastewater from the bottom to the top of the column consisting of the retained substrate, through a flow channel isolated from the column of retained substrate, and extracting wastewater from the reactor, which wastewater is purified by aerobic microbial action on the retained substrate by biodegradation of the waste product, and by providing in the basin a sedimentation zone for picking up sediment placed below the bottom shaped floor beneath the mixing zone and for picking up residual separated solid from the mixing zone. Process according to claim 1, characterized in that the residual solid is collected in a sedimentation zone of the basin and at least mainly located outside the recirculation path to promote the deposition of the residual solid in the sedimentation zone, with the exception that the residual solid is again suspended. Process according to claim 2, characterized in that it includes a working step for periodically extracting the precipitated solid from the settling zone. Method according to claim 1, characterized in that the oxidation step of the process includes surface oxidation of the water at a location in the flow path at the upper part of the mixing zone and further includes a working step for uniformly spreading the oxidized water over the upper part of the mixing zone. A biological filter for treating wastewater containing biodegradable waste products according to one or more of claims 1-4 and including a closed housing with a single column inlet and outlet conduit of a retained substrate composed of a number of individual elements which are freely and randomly stacked on top of each other in the housing and individually having a predetermined large surface area to volume ratio, and cooperatively having a predetermined large porosity with little resistance to flowing water, characterized in that in the housing (12) is a mixing zone consisting of the single column of retained substrate (28) confined at the top and bottom of the column that the inlet (14) is designed to supply water in sufficient quantity to keep the substrate (28) fully submerged, that the outlet (16) is arranged with connection to the mixing zone between its top (22) and bottom (24), which is formed as a perforated floor (24) which forms the upper part of a flow and sediment asa.