NL8402634A - METHOD AND APPARATUS FOR REALIZING AEROBIC BIOLOGICAL PROCESSES UNDER IMMERSED CONDITIONS. - Google Patents

Description

NL 32272-Kp / vD - 1 -

Method and device for realizing aerobic biological processes under submerged conditions.

The invention relates to a method and device for realizing aerobic biological processes under submerged conditions. More particularly, the invention relates to the continuous realization of aerobic microbiological processes under submerged conditions - eg biological sewage treatment, performed with activated sludge and circulation and removal of the required microorganisms, as well as a device for performing the said process.

According to the known sewage treatment methods, carried out with the aid of activated sludge, all dissolved organic substances are first decomposed by means of aerobic microorganisms. According to the known methods, the oxygen supply of microorganisms and their distribution in the sewage water is obtained by means of various surface aeration means. The said methods can be used economically for the purification of sewage water with a. · Low contamination level, eg urban sewage. However, the purification of industrial wastewater with a high organic matter content - such as in industrial scale fermentation processes - requires the use of a large amount of microorganisms (activated sludge) with the result that the oxygen supply and stirring requirements have also increased.

When surface aerating agents are used for the purification of highly contaminated sewage water, the specific energy consumption of oxygen supply appears to be considerably higher than with urban sewage water, the large volumes to be treated also increase the treatment costs. As an example of the above, it is noted that although in the purification of only slightly polluted sewage the specific energy consumption of the surface aeration is 0.45-0.55 kWh / kg 02, the same value for highly polluted industrial wastewater is 0.7-0.8 kWh / kg 02 · As the volume of oxygen increases, the cost of aeration increases. Another disadvantage of surface aerators 8402634 '' - 2 - is that they are suitable for the uniform aeration of basins with only a limited water depth (no more than 3-4m) and therefore the structure used for the purification large base area. As other after-5 parts can be mentioned the intensive unpleasant odor, mist and spray formation and the risk of freezing.

In order to overcome the above-mentioned drawback of surface aerators in the purification of highly contaminated industrial waste water, use was made of the so-called "deep aeration system" (Bayer Turmbiologie;

Hoechst Biohoch Reaktor). Due to the considerably greater water depth, a significant space saving can be achieved in these methods and at the same time, the residence time of air bubbles is longer with the result that the amount of dissolved oxygen increases. These processes are carried out in carbon steel tanks, which are cheaper and easier to build than the reinforced concrete structures and at the same time allow the use of modern methods for producing phase surfaces and for stirring the liquid in the tank / Hydrocarbon Proc. 191-195 (1980)? Chem. Ing. Tech. 52, 930-932 * (1980) 7-As a result of the above, the specific energy consumption in deeply aerated tanks is 0.25-0.40 kWh / kg 02 / which is considerably more favorable than with surface aerators, or clean introduced air must be compressed to a pressure which depends on the water depth. Chem. Ing. Tech. 52 330-331 (1980) 7-

The deeply aerated tanks have another characteristic aspect, viz. That the sludge settling space is an indispensable part of the biologically activated sludge device and is built together with the tank and is placed concentrically on the outside upper part thereof in order to save space and use the positional energy of the water already sent upwards. Along the perimeter of the settling space, a number of conical or pyramidal sludge drain "stumps" or a larger compartment with angled curved plates, which promote the slippage of the sludge formed, are provided to ensure uniform sludge discharge . Both embodiments result in the 8402634: / 9 * / - 3 - formation of dead spaces, increased investment costs and make working with such systems cumbersome.

In the sewage treatment, using activated sludge, the water purified by microorganisms from the aeration space yields a mass of microorganisms, the amount of which corresponds to the volume flow and the sludge concentration. The amount of the microorganism mass thus supplied is several times greater than that formed in the biological purification of the circulated waste water, with the result that, in order to maintain the sludge concentration of the aerator, part of the sludge concentration in the sedimentation chamber separated sludge - with the exception of the excess sludge formed - to be recirculated in the aerator. The volume flow of the recycled sludge is added to the volume flow of fresh waste water for which reason it is preferable to recycle the required sludge mass from the settling space with a minimum water flow. For this reason, the concentration of the sludge in the settling space has increased by a factor of 1.5-2.5 with respect to the original value by sedimentation. In practice, a further 0.8-2 fold sludge recirculation - with respect to the fresh waste water introduced - is used, depending on the characteristic properties of the sludge.

According to the known activated sludge processes, large sludge volumes and suitable pumping capacity are used to obtain a possibly thicker sludge.

According to an essential aspect of the method according to the invention, at the end of the aerobic microbial procedure, no more than 1.1 times the flow of liquid to be treated is introduced into the jacket of the circular symmetrical aeration space at the axis of the aeration space in a concentric settling space, which is arranged outside-top with respect to the aeration space and communicates therewith. From this space, the microorganisms separated under free settling (unhindered) are recirculated in the aeration space along the lower circumference, whereby the purified liquid flow is fed at the top of the settling space, while the ant organisms (excess sludge) formed in the aerated space in the aerated space are removed in the meantime by using the liquid flow, which ash from the aerated space and are concentrated separately. According to this method, the sludge concentration of the aeration space can be easily maintained by means of a liquid flow, which is a maximum of 15% of the volume of the liquid to be treated. The sum of the amount of the treated liquid flow, originating from the settling space and the excess sludge discharged, is in each case identical with the liquid flow to be treated and introduced into the system. Thus, a maximum of 1.1 volume of the liquid fed into the settling space is the sum of 10% of the introduced volume and the amount of the excess sludge flow greater than the treated liquid flow, which is located in the upper part of the sedimentation area. The said excess liquid is up to 15% of the introduced liquid flows and flows back into the aeration space through the bottom of the settling space together with the diluted sludge and is always sufficient to maintain the hydraulic balance of the system. As a result, no sludge thickening is required at the bottom of the settling space and at the same time the sludge mass, separated from the treated liquid, can be easily fed into the aeration space using a pump of significantly lower power than the conventional one.

According to the method of the invention, the raw liquid flow to be treated, the required nutrients and auxiliary substances can be introduced into the microbiological process near the jacket of the aerated tank or further along concentric circles. Thereby, the concentration gradient formed during the radial flow can be worked. The concentration gradient can also be modified by dividing the gas streams introduced into the aerated space along concentric circles into groups, whereby the gas supply for each group is controlled separately.

8402634 Êf i% - 5 - can be used in the various aerobic microbiological processes. Air or a gas with an increased oxygen content. Before adding to the system or apparatus, the gas can be heated or cooled in the same manner as the liquids. The positional energy of the gases to be introduced into the aeration space at the bottom of the tank 5 generally through concentric manifolds can be utilized to agitate the contents of the tank using the "air-lift" principle. At the same time, the introduced gas streams are dispersed, if desired, pulsed to obtain suitable contact and oxygen transfer.

Due to the unpleasant odor and infection risks, it is often desirable that the gases used in the aerobic microbiological processes do not go directly into the open air, but are collected and removed, if desired after post-purification. For this reason, a closed aeration space is used in some cases.

Using the concentric oblique cylinders contained in the closed aeration tank and extending below the liquid level, the gases can be introduced in the same direction or opposite direction as the liquid flow moving in the radial direction such that the liquid space exiting gases are introduced using an intermittent machine in the next space section etc. This coupling is particularly advantageous when using gases with an increased oxygen content and in procedures where the oxygen need changes greatly with time.

It often happens in aerobic microbiological procedures that the microorganism mass cannot be easily separated from the liquid. With activated sludge wastewater treatment, this phenomenon becomes the "swelling" of the sludge as a result of various light poisoning and excessive loading. In order to overcome this problem and facilitate separation, various additives - eg coagulants and polyelectrolytes - are used according to the invention.

The advantages of the process according to the invention can be summarized as follows: - the microorganisms carried with the treated liquid 8402634 * * - 6 - can be recycled using a small volume of liquid in the aeration space and evenly distributed along the periphery of the device in a simple manner - the sedimentation of the microorganism mass does not require sludge thickener and, as a result, volume can be saved; the continuously formed microorganism mass (excess sludge) can be concentrated under favorable conditions to a small part of the liquid not more than 1/10 of the introduced liquid; the activated sludge is quickly recycled in the aeration room, avoiding anaerobic processes; the microorganism mass, recirculated from the settling space in the aeration space, can preferably be aerated prior to mixing with the liquid to be treated; 20 "- the aerated space can operate either as a stirred tank reactor or a flow-through reactor or a combination thereof; the concentration gradient of the liquid, which flows radially in the aeration space, can be easily regulated by introduction of liquid and air.

The method according to the invention is particularly suitable for the biologically activated sludge treatment of highly contaminated waste water and for realizing continuous fermentation technologies on an industrial scale.

The vertical section of the device, suitable for carrying out the method according to the invention, is shown in Figures 1 and 2.

FIG. 1 shows a typical embodiment of the device, while FIG. 2 shows a specific embodiment thereof. It is emphasized that the invention comprises a number of embodiments within the scope of the method claims.

84 0 2 6 3 4 «* - 7 -

The device is described with reference to fig.

1. The cylindrical and conical tank 10 is divided by the cylindrical-conical separate air chamber 11 into two halves, which are connected to each other via slot 5, which runs along the circumference. The aerobic microbiological process takes place in space 12 below the air chamber 11. The air or gas with an increased oxygen content is preferably introduced into the tubes 13 and 13a, which are open at both the bottom and top ends. The said tubes are arranged in 10 groups according to the task to be performed. The microorganisms are separated from the treated liquid in space 19 around the air chamber 11. The separated microorganisms are recirculated in the aeration space 12 via the slot 5.

The liquid to be treated is continuously introduced into the aeration space 12 via the pipe 1, the distribution trays and the connecting pipes 9 and / or 9a along one or more concentric circles. At the inlet sides, the liquid to be treated is mixed with the contents of the tank using air or increased oxygen content gas, which is introduced into the stirred contact tubes 13. The liquid to be treated is provided with the aerobic microbiological procedure required amount of oxygen under radial flow. The gas and stirring required for the microbiological procedure takes place via line 2, the amount of which can be controlled by supply valves 2, preferably arranged along concentric circles with each series of tubes. The liquid flow introduced by conduits 9 passes the tank with stirring in a radial direction towards its axis, passing a controlled amount of the liquid with the microorganisms therein to the distribution tray 15 using the air-lift 14 or any other suitable means, after which the liquid enters through the pipes 16 and inlet pipes 17 into the settling space, surrounded by the walls 10 and T1 concentric with the aeration space.

From the settling space, the microorganisms are led under free (unhindered) sedimentation through the slot 5, directly into the aeration space, where, if necessary, the microorganisms 8402634 - 8 - / organisms can be activated, using the series of tubes 13a closest. with the jacket before coming into contact with the raw liquid. The microorganisms (excess sludge) that are continuously formed in the microbiological process are distributed, preferably in volume flow 3, which passes via line 6 into the sludge thickener 20, which works in a known manner. The liquid stream 4 purified in the settling space of the apparatus is removed via the overflow 18. The gases exiting the micro-10 biological process are combined and removed via line 7 and purified if necessary.

According to FIG. 2, the gas space of the device is divided into sections by the concentric cylinder jackets 22, which are arranged in the aeration space 12 and which extend in the liquid. The gases exiting the separate gas spaces are transported to the next contact stirring section in the radial direction inward or outward and thus are conducted with the flow upstream or downstream of the radial liquid flow. Further details of the invention are

a

set in the following non-limiting example.

EXAMPLE

For activated sludge waste water purification, 3 a device was used with a volume of 1720 m and a 1 2 3 4 5 6 7 8 9 10 11 8402634 water depth of 7.5 m, which device is divided by means of 2 3 3 air chamber 11 into a aeration area (1380 m) 4 3 5 and a settling area (340 m). 60 contact mixing tubes are installed in the aeration room. The liquid contents of the aeration space are stirred using the said 6 tubes using the position energy of the gas introduced from 7 below, while the oxygen required for the microbiological 8 procedure is dissolved in the waste water 9 and participates in the purification process . The biologically purified waste water is led into the settling space 11 with the help of air-lift 14 through eighteen inlet pipes, which are evenly arranged along the circumference of the settling space 19.

As waste water to be treated, use is made of 54 m / h raw waste water, originating from various pesticide-producing technologies. The raw waste water is first neutralized, equilibrated in a qualitative manner and provided with feed materials, after which the raw water thus treated is transferred into the aeration space of the device via line 9 along the jacket. The average pollution degree of the wastewater is 5700 g / m COD (chemical oxygen demand), which is removed with an average efficiency of 90%. 3750 m / h air is introduced into the aeration room at a pressure of 1.85 bar, divided into three concentric pipes. The average sludge concentration of the aerated space is 4.5 kg / m, while the yield of excess sludge is 26 kg / h.

54 m / h of sludge-containing water is led from the aerated space by means of air-lift 14 into the settling space, from which 47-48 m / h of sludge-free purified water is discharged via an overflow. The excess sludge formed in the biological process is also removed using air-lift 14 through a water flow of 6-7 m / h, depending on the sludge concentration. Sludging and concentration of the sludge takes place in a small apparatus via known methods. The sludge (approx. 260 kg / h) that precipitates from the purified water leaving the overflow flows along the jacket of the device along with 6-7 m / h water flow and is reintroduced into the aeration chamber via slot 5. This downward flow of liquid is sufficient to maintain the hydraulic balance of the system.

Compared to this example, the material volume of the aeration space and sedimentation device of known processes is as follows: - waste water input into the aeration space: 54 m / h; - water flow, required for recirculating the 3 concentrated sludge up to 9 kg / m from the settling space: 48 3 35 m / h; • - water flow, required to remove the 3 excess sludge: 3-3.5 m / hour; 3 - volume of the sedimentation concentrating space: 400 m.

The comparison shows the following advantages of the method according to the invention: - it is not necessary to thicken the settled activated sludge before recirculation in the aeration space; which means that about 15% of the volume of the settling space can be saved; - the recirculation of the sludge from the settling space is simple and the volume of the liquid flow is only 15% of that of the known processes, the required pump capacity being relatively smaller.

The volume of the apparatus required for the sedimentation and thickening of the excess sludge is small, relative to the amount of excess sludge; at the same time, the separate settling space allows the use of such technologies and additives in the settling of the excess sludge, with a beneficial effect on the thickening process.

• * 4 * * t 8402634

Claims (10)

1. A continuous method for realizing submerged aerobic biological processes in a tank for the aeration of microorganisms, which tank has a vertical axis and a circular cross section, and in a settling space outside the tank along its top circumference, with the characterized in that the raw liquid flow to be treated, the nutrients and auxiliaries are introduced into the tank near the jacket of the aerated tank or at its jacket and distributed along further concentric circles, while contacting the liquid containing microorganisms and is stirred with optionally pulsating air or gas stream with an increased oxygen content distributed at the bottom of the tank: from liquid containing microorganisms no more than 1.1 volume of the liquid stream or streams, passed into the system, is introduced at the axis of the aerated tank, which introduction is carried out along the oratrek of the tank in the * sedimentation area? the microorganisms separated from the liquid under free (unhindered) sedimentation are recirculated in the aerated space at the bottom of the settling space, while the liquid liberated from microorganisms overflows at the top of the settling space, the in the aerated space (excess sludge), continuously formed microorganisms are removed from the system by means of the liquid stream, which is carried away from the axis of the tank, and the microorganisms are separated from the liquid. 2. Method according to claim 1, characterized in that the gas flows introduced into the tank along concentric circles are arranged separately and the gas supply of the separate groups is regulated separately * 3. Process according to claim 1 or 2, characterized in that the liquid and / or gases are heated before their introduction into the process. 4. A method according to any one of the preceding claims 1-3, characterized in that the gases are introduced with the flow in countercurrent or countercurrent with respect to the flow of liquid in the aerated space with respect to 8402634. of the aerated space preferably in various sections, the gases leaving the first liquid space being introduced into the next section, followed by repeating this procedure. 5. A method according to any one of the preceding claims 1-4, characterized in that use is made of an additive for the separation of the microorganisms from the liquid. Device for carrying out the method according to claim 1, which device has a circular cross section and a vertical axis, characterized in that a tank (10) is divided by a concentrically arranged air chamber (11) in two sections, namely the aeration space (12) and the settling space (19), which are connected to each other via a concentrically arranged upper distribution chamber (15) with pipes (16) and which communicate with each other via gravity at the bottom of the air chamber and a liquid discharge stub (6) connects the distribution chamber (15) and a water discharge stub (4) connects the sedimentation space (19) via a collection trough (18). 7. Device according to claim 6, characterized in that an air-lift (14) or an immersed pump or a pump, which is arranged outside the appliance, is connected to the distribution chamber (15) and serves as a discharge of the liquid from the aeration chamber (12). 8. Device according to claim 6 or 7, characterized in that the tubes (9) and (9a) extend to the aeration space (12) and come out of the distribution chamber (8) and are on one or more concentric circles symmetrical to the axis of the device and serve as a supply of the raw liquid stream to be treated. Device according to any one of the preceding claims 6-8, characterized in that, for introducing the liquid from the aeration space by forced flow and with microorganisms therein, a number of supply lines (17) are supplied. are arranged in the settling space of the device, which are preferably evenly distributed along the periphery of the settling space. 10. Device according to any one of the preceding claims 6-9, characterized in that the aeration space of the device is closed at the top end and is provided with a butt (8) for the discharge of the evasive gases. t 8402634