MXPA97007303A

MXPA97007303A - Procedure and installation for the treatment of waters through a purifier and a multicapas filter that works at high speed

Info

Publication number: MXPA97007303A
Application number: MXPA/A/1997/007303A
Authority: MX
Inventors: Le Poder Nicolas; Sibony Jacques
Original assignee: Otv Omnium De Traitements Et De Valorisation
Priority date: 1997-08-22
Filing date: 1997-09-24
Publication date: 2000-01-01

Abstract

The invention relates to a water treatment process whose objective is to reduce its content of suspended materials and, given of parasites, characterized in that it consists in passing said waters through at least one purifier (1) with a higher treatment speed at 20 m / h and then, with an upward flow, by at least one multilayer filter of decreasing granulometry (2) with a treatment speed higher than 10 n / h. Preferably, the purifier used will be a weighted flow purifier, preferably a

Description

Procedure and installation for the water treatment by means of a purifier and a multilayer filter that works at high speed The present invention relates to the field of water treatment. In particular, the invention relates to a physical or physical-chemical process designed to reduce the content of suspended materials or parasites of such waters, as well as the installation corresponding to the process. The invention can be used to treat any type of water containing suspended matter, and when it is desirable to decrease its content, in particular: - the waters already treated by biological route, in order to refine the purification thereof; - waste water intended to be reused after treatment; for example, in industry or agriculture, particularly for irrigation; - waters destined to be discarded at sea; - waste water already treated by biological or other means, in order to control the residual phosphorus content of the waste. As already mentioned before in this document, the process and the installation according to the invention are particularly interesting for the treatment of the suspended matters contained in the waters destined to be reused for irrigation; Within the technological advance, there are many techniques for the treatment of suspended materials. These techniques include: - physical or preferably physical-chemical purification consisting of subjecting the water to a clarification possibly combined with the addition of a coagulant reagent whose objective is to increase the susceptibility to decantation of suspended materials; - filtration in a bed of sand with a thickness generally between 1.5 and 2 m. As for the treatment speed applied in traditional purifiers, it rarely goes from 2 to 2.5 m / h. This treatment rate can be increased to between 10 and 15 m / h if the purifier used is of the laminar type, and up to 20 m / h if the laminar purification is combined with a coagulation-flocculation stage. To obtain a good quality water, the previous inventions recommend using sand beds with a maximum filtration speed of 10 m / h. In this way, these two types of treatment have the drawback of not being able to operate at high speeds, which requires the use of large-scale installations that involve high civil engineering costs. The main objective of the present invention is to propose a water treatment process designed to reduce its content of suspended materials and, if necessary, parasites (particularly the uevecillos of helminths) that allows working with compact works of reduced dimensions in relation to the current facilities, in order to obtain a water of sufficient quality to respond to the demands, for example, of any of the aforementioned reuses. This objective is achieved thanks to the characteristic invention that involves a method of treating waste water in order to reduce its content of suspended matter and, if necessary, of parasites, and which consists in passing said waters through a purifier with a treatment speed higher than 20 m / h and then, with an upward flow, through a multilayer filter of decreasing particle size, with a treatment speed of more than 10 m / h. The invention then proposes to treat the suspended materials and, if necessary, the parasites, by operating a purifier operating at high speed (that is, at a speed higher than the traditional speed recommended by the previous inventions for putting into operation). of such a purifier) and a multilayer filter of decreasing particle size, with the upward filtering direction also operating at high speed. As previously stated, the treatment of suspended matter was already known, either by decanting or by filtration through a sand bed. However, as far as the Applicant knows, it has never been proposed: - to attach such a purifier to a granular filter, specifically to a very particular type of filter; that is, a multilayer filter of decreasing granulometry, with upward current; - nor use these high treatment speeds in this type of device. The Applicant has found that, quite surprisingly, the use of treatment speeds higher than those recommended by current techniques in both the purifier and the granular filter would allow, within the framework of such a combination of technical means: pretty good level of reduction of suspended matter and parasites such as helminth eggs; And - filter saturation speeds clearly lower than those obtained with traditional filtration. Such a result is not obtained with the previous inventions that do not recommend the association of a purifier and a multilayer upstream filter and that involve processing speeds much lower than those proposed by this invention to obtain a good level of purification. Said result also goes against the prejudice according to which the quality of the depuration decreases with the speed of the treatment. According to a preferred variant of the invention, the aforementioned method comprises an intermediate step consisting in sifting said waters between its exit from said purifier and its entrance to said filter. The use of such sieving allows to protect the false bottom of the granular filter; that is, avoid the accumulation of sludge in the space provided in the lower part of the filter, under the granular material, space to which the water coming from the purifier is directed. Said sieving also allows to retain threads and other obstructive elements that may exist in the waters coming from the purifier. This intermediate stage presents the important advantage, when comparing the sieving done with the treatment usually recommended by the current procedures, to be more economical, since it puts into operation less loaded waters, and protects more directly the filters in case of failure of the decantation system. The operation of the process can be considered without the addition of the coagulant agent. In this case, with this device, treatment speeds of up to 30 m / h can be used. However, the purifier used to operate the process according to the invention will preferably be a ballasting flow purifier with the addition of at least one coagulating agent. In this case, the treatment speed used in it may be at least 35 m / h. In the preferred embodiment, the purifier used will be a laminar ballast flow purifier. In this case, the treatment speed used can be at least 60 m / h and can rise up to 200 m / h. These speeds are considerably higher than the speeds recommended by the previous inventions for this type of facility, which, as already mentioned, does not exceed 20 m / h; and the same happens in the case of laminar purifiers. This type of purifier is described in particular in French patents FR 2627704 and FR 2719734 in the name of the Applicant. Its use within the framework of the process according to the invention allows the treatment speeds and consequently the compactness of the structures to be further increased. In general, the flocculation-decantation treatment processes are previously operated with a coagulant reagent injection system in order to rapidly and vigorously disperse the reagent within the waters to be treated. Contrary to what is stipulated in the current technique, the Applicant recommends injecting the coagulant reagent directly into the rapid mixing vessel of the ballasting flow cleaner in an area of low turbulence and away from the main streams, or at least injecting the reagent afterwards. of a strong previous dilution that allows to inject the coagulant in the form of precipitates of iron or aluminum constituted mainly by hydroxides. In fact, it has surprisingly been found that the use of such injection forms makes it possible to significantly limit the elimination of phosphates and even control them without prejudice to the reduction of suspended matters. This adaptation of the procedure is particularly interesting in the case of water intended to be reused for irrigation, thus preserving a sufficient phosphate content. Within this preferred variant, the possibility of controlling the residual phosphorus content depending on the type of application without degrading the reduction of the suspended materials, without being limited by the amount of added reagents and by the rather low residual phosphorus values, is particularly interesting. According to a preferred variant of the method, this comprises a complementary step consisting of injecting at least one flocculation reagent into said waters before said filter. According to another preferred variant of the invention, the processing speed used within the upstream multilayer granular filter fluctuates between 25 and 45 m / h. According to another aspect of the invention, the washing of the filter is preferably carried out by passing purified water countercurrently inside said filter and by diverting the dirty water stream leaving the filter. Such a washing model allows it to be carried out without having to have pumps or a storage of filtered washing water, which allows to reduce the cost and complexity of the procedure. When it is decided to use several filters in parallel, washing with purified water from a filter can be carried out simply by increasing the water input to said filter, to the detriment of one or more filters. Such washing operation can be carried out with a concomitant, continuous or intermittent injection of air into the filtering material, in order to improve its efficiency. Similarly, the systematic injection, or at intervals, of a disinfecting agent, such as chlorine, for the water to be used in the wash can be envisaged. In the same way, according to another variant, the method, according to the invention, is put into operation before a biological treatment plant for waste water. It can also be put into operation after a treatment installation, where it allows to improve the operation and / or operating conditions. The invention also relates to an installation for the operation of the process described above, characterized in that it is constituted by the association of at least one purifier followed by at least one multilayer filter with a decreasing granulometry, with an upward filtering direction. Preferably, the installation comprises at least one screen between said purifier and said filter, with a mesh between 0.5 and 5 mm, preferably between 500 μm and 2 mm. It is preferable and advantageous for said filter to be flow-weighted and, preferably, laminar. According to a variant of the invention, said multilayer filter includes at least one layer of gravel and at least one layer of sand. Preferably, the installation will also include a disinfection device located before said filter. Finally, and also preferably, the installation has means that allow to extract during the filtration cycle, by means of one or more gravity traps, at least a part of the materials retained in the bottom of said filter. The invention, like the various advantages it offers, will be more easily understood thanks to the following description of a non-limiting embodiment referred to in the drawings thereof: Figure 1 represents a schematic view of an installation for putting into operation the process according to the invention; Figure 2 represents a graph illustrating the curves of reduction of suspended matters obtained thanks to the invention and, for comparison purposes, those obtained with a method that does not include a multilayer filter with updraft; Figure 3 represents a graph illustrating the saturation curves of the upstream multilayer filter used within the framework of the process according to the invention and those of a traditional filter; Figure 4 represents a graph illustrating the pressure loss evolution curves within the framework of the method according to the invention and those of a traditional filter; With reference to Figure 1, the installation consists of a weid flow-type purifier 1, a multi-layer filter 2 with upflow and a screen 3 installed between the purifier 1 and the filter 2. The ballast flow cleaner 1 includes two compartments above and Ib and a compartment forming the purifier provided with inclined lamellas Id. There are distribution means 5 of a coagulating agent for distributing said agent in compartment la, and in compartment Ib there are means of distribution 6 of a Flocculation reagent. The multilayer filter 2 has four superimposed layers of gravel 2a and 2b and sand 2c and 2d, which make up filtered materials. The layer 2a is constituted of gravel of 10 to 20 mm in diameter and has a thickness of 0.2 m. The layer 2b is composed of fine gravel of 5 to 10 mm in diameter and has a thickness of 0.5 m. The layer 2c is composed of coarse sand of 2.5 to 5 mm in diameter and has a thickness of 0.3 m. The layer 2d is composed of fine sand of 1.5 to 3 mm in diameter and has a thickness of 0.2 m. This is obviously only one embodiment of the multilayer filter, which may, within other embodiments, present some other structure without departing from the spirit of the invention. The filter also includes means for conducting the water from the laminar flow cleaner 1, installed in its lower part, and means for evacuating the water that has passed through the filter material in the upper part of the filter. The filter also includes means for injecting air 10 and evacuating water by gravity traps 11 and washing water by the lower tray 12. The existing screen between purifier 1 and granular filter 2 has a mesh of 1 mm.

The installation also preferably has injection means 4 of a disinfecting agent installed immediately before the filter. The washing of the filter can be carried out easily with the help of the purified water coming from the purifier 1 and by diverting the dirty water leaving the filter. The effectiveness of the washing is reinforced by distributing a disinfectant compound such as chlorine in the purified water, thanks to injection means 4 and / or by putting into operation an injection of air into the filtration material thanks to medium 10. According to the present invention, the illustrated installation is put into operation with a treatment speed in the purifier of 120 m / h, and a treatment speed in the multilayer filter of 30 m / h. Figure 2 shows the results obtained after 4 days of operation in the reduction of suspended materials. In this figure, the content of substances in suspension in the water before treatment is indicated by the curve above, while the content after the treatment according to the invention is indicated by the curve in which the measurement points appear with shape of triangles. Comparative studies have been carried out with an installation of the type described with reference to figure 1 but integrating a traditional filter with a filtration speed of 10 m / h. The results obtained after 4 days of operation in the reduction of suspended materials are also shown in Figure 2 (curve in which the measurement points appear in the form of triangles). The comparison of these last two curves shows that the water quality obtained is almost identical.

The use of high treatment rates in the multilayer upstream filter according to the invention does not imply deterioration in the quality of the treatment. Figure 3 shows the advantages of the invention compared with a traditional solution from the point of view of the saturation speed of the filter. In fact, not only the saturation is clearly slower (between 5 and 10 times) in the case of the invention (see curve A) than in the traditional monolayer filter (see curve B) but, in addition, such saturation is not accelerated by the increase in filtration speed, contrary to what happens with traditional solutions. Figure 4 shows an example of the evolution of pressure loss in the cycle of a traditional filter (curve C) and for a multilayer up filter (curve D). One can underline the obviously slower evolution of pressure loss in multilayer filtration as well as the efficiency of the gravity traps performed in the cycle. It will be noted that the installation, according to the present invention, has reduced dimensions in comparison with the current installations. The type of works that compose it allow to treat the waters in dry seasons as in the rainy season. In addition, it is possible to decrease the doses of reagents used in the purifier compared to the necessary doses when only one purifier is used. The embodiment of the invention described in this document is not intended to reduce the scope thereof. It can be done and numerous modifications will be made without departing from the spirit of the same. In particular, it will be noted that it is possible to use not only a filter, but a battery of filters operating in parallel.

Claims

CLAIMS 1. Water treatment process whose objective is to reduce its content of suspended matter and, where appropriate, of parasites, characterized in that it consists in passing said water through a purifier (1) with a treatment speed of more than 20 m / h and then, with an upward flow, by at least one multilayer filter of decreasing granulometry (2) with a treatment speed of more than 10 m / h. Method according to claim 1, characterized in that it includes an intermediate stage consisting in the screening of said waters between its exit from said purifier (1) and its entrance to said filter (2). Method according to claim 1 or 2, characterized in that said purifier (1) has the addition of at least one coagulating agent in which the treatment speed used is at least 35 m / h. 4. Method according to claim 3, characterized in that said purifier (1) is a flow purifier weighted by the addition of at least one coagulating agent, and with one. Laminar texture, in. Which, the treatment speed used is at least 80 m / h. 5. Method according to any of claims 1 to 4, characterized in that said waters are intended to be reused for irrigation. Method according to claim 5, characterized in that said coagulating agent is injected into a container of the ballasting flow cleaner in an area of little turbulence thereof. 7. Process according to claim 5 or 6, characterized in that it comprises an intermediate step consisting in making a strong digestion of the coagulating agent before introducing it into said purifier. 8. Procedure according to Claim 4 Q 5, characterized in that it comprises a complementary step which consists of injecting a flocculant reagent into said waters before entering said filter. 9. Method according to any of claims 1 to 8, characterized in that it consists in passing said waters through. said iauLticapaa filter of decreasing granulometry with a treatment speed between 25 and 45 m / h. 10. Process according to any of claims 1 to 9, characterized in that it comprises a step of washing said filter, which consists in passing purified water, possibly added with a disinfecting agent, countercurrent inside said filter and deriving the dirty water flowing out of the filter. 1L .. Procedure of. Agrees can The claim. 10, characterized in that said washing step is carried out and an intermittent or continuous injection of air is put into operation inside the filter material constituting the filter. 12. Process according to any of claims 1 to 11, characterized in that it is put into operation after a biological wastewater treatment plant. Method according to any of claims 1 to 11, characterized in that it is put into operation before a treatment installation that allows to improve the operation and / or the operating conditions.

1 . Installation according to any of claims 1 to 11, characterized in that it is constituted by the association of when you ore a purifier (1) followed by at least one multilayer filter (2) of decreasing granularity ^ with ascending filtering sense. 15. Canarian installation. Claim 14, characterized in that it comprises at least one screen (3) existing between said purifier (1) and said filter (2), with mesh between 0.5 and 5 mm, preferably between 5QQ μm and

2. mm. 16. Installation according to claim 14 or 15, characterized in that it has a ballast flow purifier (1) k 17. Installation according to claim 14 or 15, characterized in that said purifier (1) is a weighted flow purifier. laminate. 18. Installation according to any of claims 14 to 17, characterized in that said multilayer filter (2) comprises at least one layer of gravel (2a) and at least one layer of sand Í2b). 19. Installation according to any of claims 14 to 18, characterized in that it comprises a disinfection device (4) located before said filter (2). 20. Installation according to any of claims 14 to 19, characterized in that it comprises means (11) that allow to extract during the filtration cycle, by means of one or more gravity traps, at least a part of the materials retained in the background of said filter.