FR2554802A1 - Process and device for biological treatment of sewage - Google Patents

Abstract

Biological treatment of sewage containing heterotrophic or autotrophic microorganisms, consisting in that the sewage is separated by filtration of the microorganisms particularly in a biological reactor 1 with the aid preferably of a granular filtration layer 3 which is cleaned during the infiltration process by a regeneration apparatus 7 equipped with a washing drum 8a with horizontal rods and a conduit 10 through which the sludge is discharged towards the activation tank.

Description

Method and device for biological treatment of wastewater.

  The invention relates to the biological treatment of wastewater with heterotrophic or autotrophic microorganisms. The heterotrophic microorganism process (activated sludge purification process) is especially suitable for the degradation of organic substances contained in water. Autotrophic microorganisms mainly use

  inorganic food substrates such as phosphorus and nitrogen.

  The method of the invention can be used for municipal wastewater, but also for many wastewater from industry and agriculture. The invention further relates to the as complete as possible removal of suspended matter

in wastewater.

  For the activated sludge process operating with heterotrophic microorganisms, depending on the current state of the art,

  knowledge, at least two reactors.

  In the activation basin, the wastewater is mixed with the activated sludge which is returned to it and is simultaneously aerated. In the final settling tank, the separation of sludge and wastewater takes place, for example by sedimentation or flotation. The more or less concentrated active sludge is mostly brought back into the activation basin. The disadvantage of this process comes

  especially the importance of the dimensions of the reactors required.

  To limit the volume of the activation basin, we sought to obtain a higher concentration of sludge. To this end, the proportion of sludge returned has been increased. However, this is only possible within certain limits since this results in an increase in the load of the final settling tank. To obtain a higher load capacity of the final settling tank, we worked with elements added in the sedimentation zone, and in particular with bundles of tubes. But it turned out that the space under the added elements is not enough to obtain the concentration of sludge because this concentration takes place significantly more

  slowly than the first phase of sedimentation.

  Another disadvantage of the currently known technique is the sometimes significant extraction of suspended matter from the

final settling tank.

  The disadvantage of heterotrophic microorganisms is that they cannot synthesize biomass from inorganic nutrients contained in water such as nitrogen and phosphorus. The possibilities of elimination of N and P by means of heterotrophic microorganisms are limited by the contribution of organic carbonaceous compounds. It is therefore necessary to dose carbon compounds

  additional during denitrification, or to precipitate phosphate.

  Autotrophic microorganisms are used for the treatment of wastewater, especially in wastewater tanks. These tanks are only suitable for the treatment of relatively small quantities of wastewater because the residence time is between several

  days and several months depending on the concentration of wastewater.

  The origin of this phenomenon is the very low concentration of microorganisms. To eliminate this drawback, which also appears from the start when heterotrophic microorganisms are used, a settling tank has been placed after a treatment tank, provided for a crossing time of a few hours, artificially aerated and stirred. But this possibility of increasing the concentration is not suitable for autotrophic microorganisms because

  that these do not settle.

  The object of the invention is to increase the concentration of heterotrophic and autotrophic microorganisms to limit the volume of the reactors. The invention further aims to improve significantly

  separation of suspended matter.

  The object of the invention is therefore to develop a method making it possible to obtain a high concentration of microorganisms without thickening by gravity, even in the event of turbulence. The separating device should also be usable simultaneously in

- as a reactor.

  According to a first aspect of the invention, a method for the giological treatment of wastewater, in which the wastewater is brought into contact with suspended microorganisms and the duration of the treatment is substantially shorter than the period of growth of the microorganisms, characterized by the fact that the waste water is separated from the microorganisms by filtration in a biological reactor or in a device mounted subsequently and in that the microorganisms are enriched in the biological reactor. According to a second aspect of the invention, a device for implementing this process is characterized in that in a reaction tank is arranged at least one rotary filtration drum which comprises a porous filtration layer or is covered with a filter cloth or a filter membrane stretched over it, and in that

  the internal enclosure of the filter drum is provided with an outlet.

  Thanks to the use of filtration, a higher solids content is obtained in a reduced space. The filter can also be mounted directly in the reactor. The turbulence which reigns there proves to be advantageous because the deposits which form on the filter are eliminated by washing. In addition, the enrichment in solids is appreciably facilitated because the concentration cycle can be eliminated in the separating device and dilution which would be necessary if it were not otherwise, thanks to the waste water which arrives in the reactor. This gives for the first time the possibility of using in practice autotrophic microorganisms in high concentrations. The filtration process is significantly improved when microorganisms are combined into compact flakes in

the reactor.

  In the preferred embodiment of the invention comprising a grain filter in the bottom of the reactor or in a device arranged subsequently, a particularly effective regeneration process is used. Thanks to the expected difference between the level of the liquid inside and outside the regeneration chamber, an ascending current is obtained inside the vortex formation zone, which means that the sludge which are deposited are driven upwards. The short-circuit current which passes under the enveloping walls of the regeneration chamber is avoided when the washing drum is used by means of the sand wall which is formed. It is also possible to use sealing strips. The vortex movement itself is carried out in the manner described either mechanically, or by oscillations, or even pneumatically. The sludge discharged from the regeneration chamber can be returned to the reactor in the free jet, where a ventilation effect simultaneously occurs. When using deep tanks, the regeneration chamber is also closed upwards. Sludge removal is carried out

  from there, above the liquid level.

  When it comes to highly concentrated suspensions, it is advantageous to obtain a reinforced infiltration effect directly behind the vortex formation device by using

  rinse water in a separate room.

  During filtration, the regeneration device moves above the filter at predetermined time intervals, which makes

  that the entire surface of the filter is cleaned.

  When using a filter drum, large shear forces sufficient to operate for an extended period of time are developed during rotation. It is particularly advantageous that the rotation takes place, during aerating under pressure,

  in the opposite direction to the current circuit establishing in the basin.

  The invention will be better understood on reading the description

  detailed which follows of certain embodiments given only to

  title of illustrative examples; in this description we refer to

  annexed drawings in which: the figures 1A, 1B and 1C represent, respectively in side view, from above and at the end, a first example of a device for purifying waste water with the installation of a filtration layer grainy in the activation and regeneration basin by means of a rotating cylinder; FIGS. 2A and 2B represent, respectively in side and end view, a second example of a device for purifying waste water using an activation basin and a granular filtration layer placed in succession as well as the regeneration by means of a rotary cylinder; FIG. 3 represents a third example of a device for purifying waste water using a granular filtration layer placed in the activation basin and regeneration by means of oscillations; FIG. 4 represents a fourth example of a device for purifying waste water using a granular filtration layer disposed in the activation basin and regeneration by means of air infiltration; FIG. 5 represents a fifth example of a device for purifying waste water using an algae basin containing a granular filtration layer and with regeneration by means of a rotary cylinder; FIG. 6 represents a sixth example of a device for purifying waste water using an algae basin containing a granular filtration layer arranged in succession and with regeneration by means of a rotary cylinder; and Figure 7 shows a seventh example of a wastewater treatment device using filtration drums in the

activation basin.

  Example 1 (Figures 1A, 1B and 1C) In an elongated tank 1 with a depth of 3.50 m and a width of 6 m are arranged on one side the filtration tubes 2 intended for aerating under pressure. On the other side of the basin is arranged a band with a width of 3 m constituted by a filtration layer 3 with a depth of about 3 to 40 cm and whose particle size is between 0.5 ... 1 mm. Below is a support layer 4 comprising a drainage system 5 which opens into the chamber 6 arranged on the side and intended for purified waste water. The activation basin operates with a concentration of active sludge of 7 g / l and a residence time of 2 h. The supply of wastewater (municipal wastewater) takes place over the entire length of the basin. Thanks to the filtration layer, 3.50 m3 / m2.h of treated wastewater is obtained with a BSB5 of less than 10 mg / l. To maintain

  the high infiltration capacity, regeneration is carried out.

  continues by the sand cleaning apparatus 7 operating under water. The sand cleaning apparatus 7 consists of a drum

  rotary washing 8a having a diameter of 40 cm and a length of 1.3 m.

  It preferably consists of elongated horizontal bars.

  The washing drum 8a is fixed to a base frame 13 and is surrounded by side walls 17. The latter form with the closure

  upper and the upper edge of the filter a closed enclosure 9.

  Above is the evacuation chimney 11. The sludge entrained in a vortex is pumped into this chimney through line 10 and returned to the activation basin 1. A part is evacuated in the form of excess sludge. To obtain the updraft, we maintain

  a high water level in the rinse water tank 12.

  Example 2 (Figures 2A and 2B) The mixture of waste water and sludge is sent through line 21 into the filtration device 20. The waste water then infiltrates through. the granular filtration layer 3 and reach the outlet passing through the support layer 4 and through the drainage system 5. The sludge enriches on the surface of the filtration layer 3. To clean the filtration layer 3, the rinsing water tank 12 is filled with previously purified waste water. Next, the filter cleaning device 7 is moved over the surface of the filter. Due to the higher water level in the rinse water tank 12, an ascending current is obtained below the closed enclosure 9 surrounded by enveloping walls 17 which is created in the filtration layer 3, whereby the solids are extracted from the filtration layer 3 in connection with the rotation of the washing drum 8a. These materials are returned to the activation basin by the device

Evacuation 10.

  Example 3 (Figure 3) An elongated basin 31 having a depth of 3.50 m and a width of 6 m comprises on its bottom a filtration layer 33 above a support layer 32 comprising a drainage system 34 The filtration layer 3 has a thickness of 30 cm and a particle size less than 1 mm. An active mud concentration of 10 g / l is maintained in the basin. The duration of stay is 1.5 hours. For a useful pool depth of 3 m, the filtration speed is set at 2 m / h. The filtration layer 33 is regenerated at time intervals of approximately 1 hour. The regeneration apparatus 35 consists of a base frame 36 comprising a running gear 37 which is mounted movably in longitudinal direction on the edge of the basin, by

example on rails 38.

  The vortex movement created in the filtration layer 33 is obtained by vibrating grids 39. The extracted sludge is removed from the closed enclosures 310 by the sludge evacuation device 311 and lifted by the sludge delivery line 312 to a level above that of the liquid. A free jet is sent from the mud outlet 313 to the liquid, which determines an oxygen enrichment. The latter can be further increased by means of a column or injector weir 317. Owing to the increase in the level of the rinsing water, an ascending current is formed in the area of the vortices, preventing pollution at depth. The vibrating grids 39 -1 are excited at a frequency of 100 s 1 by the generator

  315 oscillations and by means of the 315 oscillation transmission.

  Example 4 (FIG. 4) An elongated basin 41 having a depth of 3.50 m and a width of 6 m comprises on its bottom a filtration layer 43 above a support layer 42 comprising a drainage system 44. The filtration layer 43 has a thickness of 30 cm and a particle size less than 1 mm. An active mud concentration of 10 g / l is maintained in the basin. The duration of stay is 1.5 hours. For a useful pool depth of 3 m, the filtration speed is set at 2 m / h. The filtration layer 43 is regenerated at time intervals of approximately 1 hour by means of a system of nozzles 45 which are mounted on a ventilation grid. The ventilation grid 45 is pressed 10 cm into the filtration layer 43. The regeneration device 46 is constituted by a base frame 47 comprising a running gear 48 which is mounted movable in longitudinal direction on the edge of the basin , for example on rails 49. The extracted sludge is withdrawn from the closed enclosures 410 by the sludge evacuation device 411 and raised by the sludge delivery line 412 to a level situated above that of the liquid. A free jet is sent from the mud outlet 413 to the liquid, which determines an oxygen enrichment. The latter can be further increased by means of a column weir or injector 414. Due to the increase in the level of the rinsing water, a current is formed in the vortex area.

  ascending avoiding pollution in depth.

  It is also possible to excite the ventilation grille 45 according to a

  predetermined frequency of for example 100 s-1.

  Example 5 (Figure 5) The figure represents, in a basin 50, a granular filtration layer 51 resting on a support layer 52 comprising a drainage system 53. Above is the space 54 occupied by the fraction of liquid surmounting the filter, which has a height of about cm. In this space 54, a suspension of algae of the Chlorella species is maintained. The biomass concentration is 2.5 g / l. Due to the high biomass content, the residence time can be

  reduced to around 6 hours for cleaning municipal wastewater.

  The cleaning device consists of a base frame 55 which moves by wheels 56 on rails or edges of concrete 57, in the longitudinal direction of the basin. The washing drum 58 is fixed to the base frame 55 and can be lowered according to the necessary regeneration depth (between 3 and 25 cm). From the base frame 55 depend the side walls parallel to the rails which reach the filter sand. The rear limit of the closed working enclosure 59 (considered according to the direction of movement) is

  constituted by a sand wall 510 formed by the device.

  The front seal is mechanically sealed by a sealing strip 511. The mud chute 512 is fixed to the base frame 55 and can be lowered according to the necessary regeneration depth (between 3 and 25 cm). The discharge edge of the mud chute 512 is adjustable in height, which allows the required evacuated quantity to be adjusted. The washing drum 58 rotates at a speed of between 30 and 40 rpm, while the whole apparatus moves forward at a speed of between 0.25 and 0.42 m / min. The extraction of muddy water is between 60 and 100 l / min., Based on a 1 m washing drum. At the rear of the closed working enclosure 59 is a tank 513 open downwards and intended for supplying rinsing water. With regard to this rinsing water, it is possible to use waste water which has been previously purified. Due to the higher water height in the rinsing water tank 513, an updraft is created in the filtration layer 51, in the vicinity of the washing drum 58.

the solids deposited.

Example 6 (fig. 6).

  Simple concrete or earth fill basins can be used as reaction tanks. When their filling height is large, a turning device must be used so that all of the microorganisms are periodically exposed to light. In reaction tank 61 is contained a suspension of algae of the Chlorella species, at a biomass concentration of 2.5 g / l. Due to the high biomass content, municipal wastewater can be treated in around 6 hours. The algae suspension is transferred to the filtration tank 62 where the water is filtered by the granular filtration layer 63. The algae are then compacted according to a dry product of 10 g / l and returned to the reaction tank 61.

Example 7 (fig. 7).

  In a reaction tank 71 of rectangular section, a pressurized aerating device 72 is mounted on a wall

  longitudinal 74. This results in the known rotating current (arrow-73).

  Near the wall 74 is provided a series of filtration drums 75. These are covered with a microfiltration fabric or with a filter membrane 76 stretched over them. The waste water to be discharged passes through the microfiltrating fabric 76 and arrives at the outlet 77. Due to the polarization of the concentration which is thus formed, the filtration speed decreases. -It is therefore necessary to have a sufficiently high shear force on the surface of the filter.

  For this purpose, the filter drums 75 are driven in rotation.

  To enhance this effect, the rotation is performed in the opposite direction

  (arrow 78) of the updraft of the liquid.

Claims (26)

  1. A method of biological treatment of wastewater, said wastewater being brought into contact with suspended microorganisms and the duration of the treatment being substantially shorter than the period of growth of the microorganisms, characterized in that the wastewater is separated from the microorganisms by filtration in a biological reactor (1, 31, 41, 50, 61, 71) or in a device (20) mounted in succession and in that the microorganisms are enriched in the biological reactor.   2. Method according to claim 1, characterized in that the heterotrophic microorganisms are enriched in the biological reactor. 3. Method according to claim 1, characterized in that the   Autotrophic microorganisms are enriched in the biological reactor.   4. Method according to claim 1, characterized in that the microorganisms originating from the subsequent device (20) are returned to   circulation in the biological reactor.   5. Method according to any one of claims 1 to 3,   characterized in that the microorganisms are gathered in flakes macroscopic.   6. Method according to claim 1, characterized in that the waste water is separated from the microorganisms by filtration through a filter cloth (76).   7. Method according to claim 1, characterized in that the waste water is separated from the microorganisms by filtration through a filter membrane.   8. Method according to claim 1, characterized in that the waste water is separated from the microorganisms by filtration through a porous filter layer.   9. Method according to claim 1, characterized in that the waste water is separated from the microorganisms by filtration through   a grainy filter layer (3, 33, 43, 51).   10. Method according to any one of claims 1, 6, 7 and   9, characterized in that a current is created parallel to the surface of the filter.   11. Method according to claim 9, characterized in that the granular filtration layer (3, 33, 43, 51, 63) is subjected to a vortex movement in a layer close to its surface, continuously or at intervals of predetermined times, inside an enclosure (9, 310, 410, 59) closed by side walls, the closed enclosure being moved above the filtration layer while an updraft is maintained in the filtration layer which is subject to vortex movement and mud   being extracted from the closed enclosure.   12. Method according to claim 11, characterized in that the updraft is produced in the granular filtration layer (3, 33, 43, 51, 63) by lowering the level of the liquid inside.   of the closed enclosure (9, 310, 410, 59).   13. Method according to claim 11, characterized in that the ascending current is produced in the granular filtration layer by adjusting a higher level of the liquid in the region close to the vortex movement.   14. Method according to claim 11, characterized in that the sludge coming from the closed enclosure (9, 310, 410, 59) is returned in   all or part of the biological reactor.   15. The method of claim 11, characterized in that the granular filtration layer (3, 51, 63) is subjected to a vortex movement caused by a rotary cylinder (8a, 58) with a horizontal axis. 16. Method according to claim 11, characterized in that the granular filtration layer (33, 43) is subjected to a movement   vortex by mechanical oscillations (39, 45).   17. Method according to claim 16, characterized in that the granular filtration layer (33, 43) is excited either at the natural frequency of the liquid, or at the average natural frequency of the current passage system, or at the natural frequency average of filter grains.   18. Method according to claim 11, characterized in that the granular filtration layer (33, 43) is subjected to a movement   vortex by gas insufflation.   19. Device for implementing the method according to the   Claims 1, 6, 7, 8 and 10, characterized in that in a basin   reaction (74) is arranged a rotary rotation drum (75) which comprises a porous filtration layer or being covered with a filter cloth or a filter membrane (76) stretched over it and in that the internal enclosure of the filter drum is provided with a exit (77).   20. Device according to claim 19, characterized in that the filtration drum (75) has a horizontal axis and is disposed near the wall (74) of the reaction tank (71), against which a device is provided ventilation, and the side of the filtration drum (75) which is turned towards the wall (74) of the basin making a downward movement in the opposite direction (78) from that (73) of the ascending liquid. 21. Device for implementing the method according to   Claims 1 and 9, characterized in that it is provided at the bottom   a reaction tank (1, 31, 41, 50, 62) a granular filtration layer (3, 33, 43, 51, 63) comprising a support layer (4, 32, 42, 52) and a system drainage (5, 34, 44, 53) or a filtering bottom, and in that an enclosure (9, 310, 410, 59) closed by side walls, open downwards and movable in horizontal direction, is arranged on part of the filtration layer (3, 33, 43, 51, 63), the enclosure being provided with a sludge removal device (10, 312, 412), a device for creating vortices (8a , 39, 45) being   arranged inside the closed enclosure.   22. Device according to claim 21, characterized in that a rinsing water tank (12, 513) open downwards is arranged against the closed enclosure.   23. Device according to claims 21 and 22, characterized in   that the enclosure closed by the side walls is also closed upwards and includes a slurry delivery pipe reaching above the level of the liquid in the reaction tank, and a   supply of rinsing water reaching above the liquid level.   24. Device according to claim 21, characterized in that the device for creating vortices consists of a   rotary washing drum (8a) with horizontal axis.   25. Device according to claim 21, characterized in that the device for creating vortices consists of a vibrating grid (39) provided by means of an oscillation transmission with an oscillation generating device (314) arranged above the water level.   26. Device according to claim 21, characterized in that the device for creating vortices consists of several nozzles (45) intended for injecting a gas, which are connected to a gas supply line.