APPARATUS AND PROCESS FOR THE TREATMENT OF LIQUID WASTES

Abstract: A process and apparatus for the treatment of waste waters comprising a unit for the biological oxydation of the waste and a unit for the treatment of active sludges.

Description: APPARATUS AND PROCESS FOR THE TREATMENT OF LIQUID WASTES The present invention relates to a process and apparatus for the treatment of waste waters of a type compris ing a unit for the biological oxydation of the wastes con stituted by at least two purification towers connected in series and operating with pure oxygen, and downstream of such unit a pair of sedimentation tanks for the concentra tion of active sludges, which may operate separately or jointly according to input, and including means for injection into such active sludges of flocculants and anti -foaming substances. A plant and process of a similar type has been described and claimed by the same inventor in Pat. App. N0 23750 A/80 filed in Italy on July 20, 1980. The plant and process described in the above mention ed application had eliminated or greatly reduced most of the drawbacks of the traditional plants and processes; namely and mainly the large site area required by such plants, the need to locate them far from inhabited area because of the emission and venting of extremely unpleasant, and sometime toxic, aerosols and odours, their high operations costs, and their limited efficiency. The plant and process described in the above mention ed Patent Application, had already achieved a notable success in reducing the direct and indirect area of the plant site and in reducing the pro-capite operating costs. The subject. matter of the present invention is there fore a process and apparatus which is a new solution with respect to the subject matter of the above mentioned Patent Application filed by the same inventor. In addition to the advantages of the prior solution, it offers novel and additional advantages notably such as, among others, flexibility of the plant which may handle large and small wastes volume, the ability to increase greatly the efficiency of compactation of the active sludges,the ability to operate totally or partially, with pure oxygen thereby further reducing the operating costs. The apparatus according to the present invention comprises a unit for the biological oxydation of the wastes, a unit for the concentration of active sludges and a unit for recycling such sludges to the biological oxydation unit. It is characterized by the fact that, for the concentration of the active sludges, there is at least one sedimentation system, and a feeding station to adequately feed such active sludges with substances which will favour compactation such as fiocculants and anti-foaming agents. The apparatus according to the present invention further comprises equipment with a chocking device to feed air and/or oxygen to the biological oxydation unit as well as an oxygen station which will feed at least the biological oxydation unit and the sedimentation tanks in case of a power failure. As a further notable peculiarity of the apparatus according to the present invention, the biological oxydation unit, embodies, at the location where residual undissolved oxygen and reaction gases are vented, special filters preferably but not necessarily of a bacteriostatic type such as to block any emission of gases or aerosols of whatewer type which may drag pathogenic bacteria or other dangerous agents. The apparatus and process for the treatment of liquid wastes object of the present invention and its characteristics are illustrated in the annexed drawings, which show one possible constructive embodiment but not the only one, wherein: FIGURE 1 is a schematic view of a plant according to the present invention; FIGURE 2 shows in detail a practical placement for the biological oxydation unit and one of the two sedimentation tanks; FIGURE 3 shows a plan of the embodiment illustrated in Figure 2; FIGURE 4 shows in detail a part of the plant object of the present invention; FIGURE 5 shows a cut view of such detail according to section X-X of Figure 4. With particular reference to Fig. 1, the apparatus object of the present invention, comprises a unit for the biological purification or oxygenation which embodies a series of tower-like oxydation chambers. In the form described as an example in the annexed figures, such unit comprises two pairs of towers R1 and R2 connected in series. It is obvious that there could be a different number of pairs of towers always connected in series. Hereunder we will describe in some detail the first pair of towers--R1. The second pair R2 will be substan- tially similar to the first pair. Of the pair R1, and this is valid also for the pair R2, only some fundamental features will be described, inasmuch as the general configuration and disposition of such towers is essentially the same as described in the above mentioned Patent Application by the same inventor, to which reference is made for construction details. The pair of towers R1 comprises a first tower R1A and a second tower R1B. The first R1A is fed at the top, through pipe 6, with liquors and wastes from a storage tank D4, which stores and receives fresh liquid wastes through pipe 6A and recycled sludges through pipe 6B. Storage tank D4 contains at its lower extremity a pair of force pumps P1A, P1B, which will move the wastes to the top of the first tower R1A through pipe 6 and valve 6C. The liquid wastes thus fed to tower R1A will flow down to the bottom of the tower and through pipe 7, which connects the lower extremities of tower R1A and R1B, will flow into tower R1B. The flow of wastes in tower R1B will go upwards (arrows B and A indicate the downward and upward flows in the two towers). When the wastes have reach ed the top of tower R1B, they reenter the first tower R1A, through pipe 8. The energy required to create the flow of wastes as described above between the first and second tower of a pair is supplied by an axial pump P3 located for instance at the top of the first tower. The pump P3 may be located elsewhere, for instance at the connection (pipe 7) between the bottoms of the two towers, or any where else in the circuit. Furthermore pump P3 could be replaced by an injection device (of the Venturi type) using as fluid energy either the liquid through pipe 6 or the oxygen flow used for the biological oxydation. The first tower R1A receives the biological oxydation fluid from a unit P01 which produces air and/or oxygen at the required pressure, shown in Figure 1, framed by a dott ed line. The P01 unit sucks air as shown by arrow W which is fed to a commercial compressor C1. The compressed air from C1 is fed into a commercial apparatus U for the production of oxygen. Such apparatus could use either molecular sieves or air fractionation. As indicated in the annexed schematic Figure 1, P01 may feed tower R1A (and tower R2A) oxygen, or air, or a mixture of both. For that purpose the pipe 2 which connects compressor C1 to apparatus U splits into pipe 2A which connects to apparatus U through valve 2B, and into pipe 2C which connects directly to towers R1A and R1B through valve 2D. From the oxygen producing apparatus U a pipe 2E connects to pipe 2C through valve 2F. Two commercial flowmeters F1 and F2, mounted respectively on pipes 2C and 2E will meter the flow of air and oxygen. Due to the above described arrangement it is possible to feed the towers with air or oxygen only or with a mixture of both. In particular the capacity of the plant may be reduced by addition of air to oxygen to a 20% of the maximum (equivalent to the percentage of oxygen in air) without any variation of the flow-rate of the feeding gas. Obviously, the partialization of the plant can be simply achieved by reducing the flow-rate of the oxygen feeding the towers. In this case, a complete partialization from 0% to 100% of the design capacity is obtainable. This fact is particularly useful to reduce the operating costs when sharp overloading of the plant can occur. For example this is the case of vacationing resorts. The air and/or oxygen eed to the first tower R1A of the first pair and to the first tower R2A of the second pair is conveyed by means of a duct 13, split in two derivations 13A and 13B. each one for one of the two towers. At the end of each derivation, inside of the towers, a drilled duct 14 is foreseen, which introduces air and or oxygen to the interior of the towers in fine bubbles. The arrangement of the pair of towers R2A. R2B is substantially identical to that of the first pair Ri. Also in this case, the first tower R2A receives the wastewater, that is coming from the second tower R1B of the first pair through a duct 10, which conveys that wastewater to the upper part of the tower R2A. The duct 10 is designed in such a way as to convey the liquid, together with the unreacted gas. from the top of the tower R1B, to the tower R2A, below. the impeller of the axial pump P4 (see Fig. 4). The introduction of the mixture in the tower R2A in performed through an apparatus MX1 as a drilled pipe or as a grid or as a notched distributor as shown in the figure, in order to obtain a further subdivision of the fluid arriving from RIB with the one flowing down in R2A. The towers of the second group are connected at the bottom by a duct 7a and at the top by a duct 8a. The flow of the waters is the same and in this case too is indicat ed by the arrows B and A for the two towers. As for the plant object of the above mentioned Patent Application, the downward speed of the water in the first tower R1A of the first group and in the first tower R2A of the second group is calculated so that the gas bubbles of any size will be dragged to the bottom. The manner in which this is achieved has been described in detail in the above mentioned Patent Application to which reference is made. The wastes flow out of tower R2B, which is taller that the others, after addition of small quantities of antifoaming substances and floculants which are mixed to the outgoing flow by means of a static mixer MX2 (Fig. 4). This mixer is composed by a number of drilled diaphragms DF1, DF2, ..., between which are inserted a number of deflecting discs DD1, DD2, ... These discs are held by a number of buffles S1, S2, S3, S4, in Fig. 4, the purpose of which is to give a rotary movements to the fluid thereby completely mixing the chemical agents and increas ing their efficiency. The reaction gases (CO2 and nitrogen mainly) and the undissolved oxygen free themselves at the top of tower R2B where they are collected and conveyed through duct 21 to a bacteriostatic filter for venting. The filter is made of alternating packs of glass wool and active carbon so as to retain all pathogenous bacteria and other nocive substances. Condensed water from the filter. as well as liquids from occasional venting of tower R1B, are conveyed respectively through ducts 30 and 31 to the feeding tank DJ. In case of particular requirements due to special characteristics of the waste to be treated. each pair of towers will have in the second tower a complete system as described above for tower R2B. From the top of the second tower of the second group R2B a duct C2 will convey the mixture of treated waters and active muds to a first decanter DC1 which, in the structural example shown, is of the conical type. Treated water will skin over its top, as shown by arrow Y in Fig. 1, while the muds, which represent the biologically active agent for the oxydation of the wastes wi1l be collected at the bottom. These muds through duct 15 and its valve 15A, are conveyed to a second decan ter DC2 (ar an equivalent known thickening device), and from it, through duct 6B, to feeding tank D4. Mus in excess of the biological oxydation recycling requireents from the first or primary decanter DC1 may also be conveyed through branch 15B of duct 15, to a mud storage tank S2, from which they can be disposed of by any known mean such as incineration, dessication, or used as fertilizer of source of biogas. Furthermore, as shown in Fig. 1, duct 15 in addition to feeding the secondary decanter DC2 through valve 15C, can also convey the active muds to duct 6B, through an interception valve 15D, downstream of the secondary decanter DC2. In this manner the secondary decanter DC2 may either be by-passed or operated together with the primary decanter DC1. This is particularly useful in case of a peaks and valleys operation and whenever additional concentration of the muds is not strictly required. A further peculiarity of the process and apparatus under the present invention lies in the fact that the mixture of treated waters and active muds which exit from tower R2B duct C2, is adequately treated with substances or agents particularly apt to increase the compactness of the muds. This treatment may either be in addition or an alternative to the same treatment provided for by mixer MX2 in the second tower R2B. The antifoaming agents and the floculants are fed respectively through ducts 18 and 19 connected upstream respectively to a feeding tank AS for the antifoaming substances and a tank F for the floculants. Each of these two tanks will in turn be connected with relevant systems for the production of the agents not shown because already known. Ducts 18 and 19 are connected downstream with mixer MX2 inside the second tower R2B and also to duct C2. The antifoaming agents and floculants are injected for the purpose of braking down the tensioactive property of the foam in the wastes which restrains mud agglomeration and of favouring such agglomeration. By means of the two above mentioned feeding systems final compactation of the muds is extremely high. Obviously each of the feeder tanks AS and F are provided with and adequate metering pump on the feeding circuits, indicated by P6 and P7. The apparatus under the present invention, furthermore includes a separate unit for the supply of oxygen particularly to the biological oxydation towers, to the primary and secondary decanters, and to the mud storage tank S2, which may operate as an alternative to the above mentioned unit P01 and will do so in case of a power failure. For that purpose this alternative unit includes a pressurized oxygen tank PK1 which is connected to the above mentioned plant units through duct 20 and its derivations 20A, 20B, 20C, 20D, which will feed the oxygen to the bottom of the towers (20A, 20B), to the primary and secondary decanters DC1 and DC2 (20C) and to the active muds storage tank (20D). Automatic oxygen feed to these sections of the plant in case of power failure is triggered by valve EV inserted on duct 20, which remains closed when power is on and opens when power fails. Such type of valve is not describ ed because the device is known. The novelty and relevant advantages of the apparatus object of the present invention described above should be self evident. A first advantage lies in the extreme compactness of this type of plant which is significantly evidenced by the comparison hereunder based on a treatment unit for from 1000 to 10.000 inhabitants. A traditional plant operating with athmospheric oxydation open tanks, for the plant itself plus the protecti ve area around it, as usually required by law, requires an area of 50.000 v 60.000 square meters. A plant of similar capacity according to the present invention occupies an area of 200 + 300 square meters and does not legally require a protective area around it. The reduction of the plant area for a plant under the present invention is evidenced by Fig. 2 and 3 which show that the four biological oxydation towers are placed at the four corners of a small square and that they support within that area the terminal decanter which in this exam ple is the secondary decanter DC2. A primary decanter DC1, if required, would be supported by the towers above the secondary decanter. Next to this compact unit are underground the wastes tank Dd and adjacent to it the active muds tank S2. This arrangement makes the plant area very small. Furthermore as the oxydation towers are totally filled with water no aeration chamber is required. A further advantage is given by the fact that the plant object of the present invention will not send forth obnoxions odours or noxions aerosols, therefore it can be placed in the vicinity of inhabited areas. This means greatly reduced costs for land, ditch, digging, piping, etc. by comparison with a traditional plant. Obviously, the plant according to the present invention will include all adequate structural solutions required for its safe operation which are not specifically mentioned here being known per-se as for instance the drainage circuits DR indicated in Fig. 1. It is furthermore obvious that changes and/or modifications may be inserted in the specific details of the plant object of this invention without exceeding the patent coverage of the invention. For instance, the oxydation towers which, in the example described herein are individually separated. may form one single body, of whatever section within which dividing walls of adequate heigh would separate for instance, the towers of the first group from the towers of the second group. The wastes will always be conveyed from one to the other through duct 10 which in this case will run outside the single body encasing the towers. The above mentioned walls will run the full height of the single body while additional partitions which will separate the towers of the same group will be shorter to allow the waste waters to flow from one tower to the other of the same group. Finally, this single body constituting a plurality of towers may have any shape and/or section which may be found to be necessary, useful or expedient for the purpose.

Claims: CLAIMS 1. Apparatus for the treatment and purification of waste waters comprising one unit for the biological oxydation of the waters, one unit for the concentration and compacting of active muds and one unit for recycling such muds into the biological oxydation unit, characterized in that for the concentration of the active muds it comprises at least one decanting system for such muds, and further it comprises a unit for feeding into such muds substances which will favour compactation of such muds, and further it comprises partializable units for feeding air and/or oxygen to the biological oxydation unit, and further it comprises an autonomons oxygen feeder connected to at least the biological oxydation unit and the mud decanters through devices which will automatically feed such oxygen in case of power failure. 2. The apparatus of claim 1 characterized by the fact that it comprises a unit for a feeding of the biological oxydation unit which is connected by a by-pass to an oxygen production unit, so that the biological oxydation unit may be fed with air or with oxygen or with a mixture of both. 3. The apparatus of claim 1 characterized by the fact that it comprises a feeding system of the active muds with floculant substances or agents. 4. The apparatus of claim 1 characterized by the fact that it comprises a feeding system of the active muds with antifoaming substances or agents. 5. The apparatus of claims 3 and 4, characterized by the fact that said floculant and/or antifoaming substances or agents are fed into the terminal tower through a static mixer. 6. The apparatus of claims 3 and 4, characterized by the fact that said floculant and/or antifoaming substances or agents are fed into the active muds duct connecting the biological oxydation unit to the muds concentration unit. 7. The apparatus of claim 1, in which the biological oxydation unit if formed by a plurality of towers, characterized by the fact that the tower are totally fill ed with water and that the terminal tower is taller that the others. 8. The apparatus of claim 1, characterized by the fact that the oxygen and reaction gases venting ducts of the biological oxydation unit are provided with filters, particularly of the bacteriostatic type. 9. The apparatus of claim 1, characterized by the fact that the oxygen feeding system in case of power failure comprises a compressed oxygen tank on the feeding duct of which is placed a valve which stays closes when power is on and opens automatically when power fails. 10. The apparatus of claim 1, in which the biological oxydation unit comprises a plurality of towers, characterized by the fact that such towers placed on the periphery of the terminal decanter support such decanter. 11. The apparatus of claim 7, characterized by the fact that the duct which connects the top of the last tower of a group to the first tower of the following group comprises at its terminal end within such first tower a device which will minutely divide and disperse the fluid conveyed by such duct. 12. The apparatus of claim 11, characterized by the fact that such distributor is either a drilled tube or a grid notched device, or similar. 13. The apparatus of the preceding claims, characterized by the fact that the towers comprising the biological oxydation unit are adequately encased in a single structure essentialy composed of one single body containing adequate partitions thus defining the said oxydation towers. 14. The apparatus for treatment of waste waters sub stantially as defined and described in the attached figures.

Inventors: RIGHETTI, GIANMARIA
Applicants: RIGHETTI, GIANMARIA
Application year: 1983
Main classification: C02F3
IPC codes: C02F3