FR2640724A1 - Improved process and installation for destroying filamentous proliferation. - Google Patents

Abstract

The subject of the present invention is a process for controlling filamentous proliferation capable of occurring in water-purification or fermentation reactors, which consists in carrying out sequential phases of turbulent circulation with or without aeration on the reaction mass to be treated, these circulation phases being implemented as soon as the proliferation rate reaches a predetermined maximum level and for a sufficient period so that this rate reaches a lower threshold value acceptable for pursuing the treatment. The invention comprises a venturi 11 which creates a turbulent state, placed in a recirculation conduit which returns the reaction mass to be treated back to the top of the reactor 2 when the proliferation rate has reached a predetermined maximum level and until the lower threshold value is reached.

Description

IMPROVED METHOD AND INSTALLATION FOR
DESTROYING FILAMENTAL GROWTH
The present invention relates to an improved method and facility for destroying filamentous expansion and in particular such overruns occurring in water treatment reactors or in fermentation apparatus.

 It is known that many facilities for the purification of fermentation water give rise to problems, often due to biological imbalances, which can cause settling accidents, among which the proliferation of sludge is the most frequent. This proliferation is the consequence of the excessive development of filamentous microorganisms in activated sludge.

 The techniques used to date against swelling, based on the destruction of biomass by injection of bactericides, have not proved particularly effective.

 The method and the installation according to the present invention overcomes the disadvantages of the known processes and installations and allows the almost complete control of the expansion.

 The subject of the present invention is in fact a process for controlling the filamentous expansion likely to occur in water purification reactors or fermentation reactors, which consists in carrying out sequential turbulent circulation phases, with or without aeration, on the reaction mass to be treated, these circulation phases being implemented as soon as the expansion rate reaches a predetermined maximum level and for a period sufficient for this rate to reach an acceptable lower threshold value for the continuation of the treatment.

 According to one embodiment of the invention, all of the reaction mass to be treated is subjected to said sequential circulation phases.

 According to another embodiment of the invention, said circulation phases are carried out on a fraction of the reaction mass returned to the reactor after having been decanted.

 The subject of the present invention is an installation for carrying out the method of destroying expansion comprising a venturi that creates a turbulent regime, arranged on a recirculation line bringing the reaction mass to be treated at the top of the reactor when the expansion rate has reached a predetermined maximum level and until it reaches a defined lower threshold value.

 According to one embodiment of the plant according to the invention, the feed line is a line leading at the top of the reactor the reaction mass removed in the reactor vessel.

 According to another embodiment of the installation according to the invention, the supply line is a pipe bringing at the top of the reactor fraction enriched sludge removed in the tank of the secondary clarifier.

 According to one embodiment the venturi in addition to the reaction mass injected into the reactor air, or air enriched in oxygen.

 Other objects and advantages of the following description and figures given for illustrative and not limiting.

 Figures 1 and 2 show two embodiments of the present invention implemented in a non-limiting manner on water purification facilities.

 In the installation of FIG. 1, the water to be purified from the secondary clarifier 1 is sent to the reactor or the pipe 3. The purified water leaves the reactor 2 via the pipe 4 'and the secondary clarifier 1 through the pipe 4 " , these two pipes coming together to form the pipe 4.

 A probe 5 for measuring the development of the filamentous biomass is set to send to a control device 6 a signal Sl corresponding to the level of expansion of the maximum filamentous biomass, which is unacceptable for the effective pursuit of the purification treatment or a corresponding signal S2. at a lower threshold value. Of course, the control device 6 can be replaced by any equivalent means such as, inter alia, a programming clock.

The abundance can be characterized by the biomass decay index (zig) or the Mohlman index (IM>
In fact, when the signal S1 is emitted, the control device 6 causes the operation of the recirculation pump 8 disposed on a recirculation line 9 leaving the reactor vessel 2. On this pipe 9 recycling water to the reactor 2 is also provided a valve 7 t a débimetre 10 and a venturi 11. The venturi creates a turbulent regime breaking the expansion.

 An inlet pipe 12 of an auxiliary air stream for further aeration of the biomass or the reaction mass in the reactor 2 is provided with a valve 13 being disposed on this pipe. It is indeed an aerobic treatment requiring the continuous supply of air.

 The water to be treated arrives in the reactor or sludge aerator 2 through line 14 comprising a valve 15. Valves 16 'and 16 "are placed on each of the lines 4' and 4" respectively. In addition, a pipe 17 connects the reactor vessel 2 to the head of the secondary settler 1. A valve 18 is placed on this pipe. It is understood, although this is not expressly shown in FIG. 1 (and for the sake of simplification) that each of the valves 7, 13, 15, 16 ', 16 ", 18 can be controlled with respect to its opening. or its closure by the control unit 6. te venturi comprises an air suction pipe 21 and a valve 22. It is thus possible to inject into the reactor the air sucked by this pipe, which allows discretion, additional ventilation.

 The operation of the installation is as follows. The water to be treated arrives via line 14 and valve 15 into the sludge reactor or aerator 2 in which the aeration of these waters occurs. In the case of aerobic treatment, additional ventilation is provided by injecting the line 12 and the valve 13 with an oxygenated stream, generally formed of air-or air enriched with oxygen. The treated water removed in the reactor vessel 2 are sent through the pipe 17 and the valve 18 at the head of the secondary clarifier 1 where enrichment of the sludge which is returned by the pipe 3, at least partly in the reactor 2. A purified part of the water contained in the reactor 2 can be withdrawn from this reactor via the pipe 4 "and the valve 16" to join in the pipe 4 with purified water coming from the reactor 2 through the pipe 4 'and the valve 16' .

 When the filamentous expansion reaches a maximum level measured by the probe 5, which is unacceptable for the effective pursuit of the purification treatment (level for which the control device 6 has been programmed), this probe sends the control unit 6 a S1 signal that causes the start of the pump 8 and the recirculation of the water in the reactor 2 so that they are recycled through the pipe 9 and the venturi 11 in the top of the reactor 2. When the level of proliferation reached a lower value defined, in general, after passage of the entire volume of the reactor 9 in the venturi 11, the probe 5 sends a signal S2 which interrupts the operation of the pump 9.

 It is thus possible thanks to the intermittent recycling of at least a portion of the process water contained in the reactor 2 and the passage through the venturi 11 to control the filamentous expansion without the need for annoying interruptions of the water. 'installation.

 When instead of the control unit 6, a programming clock is used, it is obvious that it was necessary beforehand to determine the operating periods for which the maximum level of expansion is reached and the required duration. for this rate to be reduced to an acceptable lower threshold value, and this of course for fixed operating conditions. These times are then displayed and the clock automatically starts or interrupts the turbulent sequential flow period.

 FIG. 2 shows an installation operating according to a variant of the method of the invention.

 In this figure all the reference numbers are similar to those of Figure 1 except that the pipe 3 (of Figure 1) from the secondary clarifier 1 instead of driving the enriched sludge from the decanter at the head of the reactor 1 forms the pipe 9 comprising the pump 8, the flow meter 10 and the venturi 11; (The pipe 9 of Figure 2, unlike the pipe 9 of Figure 1 does not recycle at the top of the reactor 1 water treatment reactor 2 but the sludge in the process of enrichment of the secondary clarifier 1). In addition, a branch line 9 'and two valves 19 and 20 make it possible to short circuit the venturi 11 and to inject the enriched sludge directly into the reactor 2 instead of passing them into the venturi 11.

 In fact, the opening and closing of the valves 19 and 20 as well as the venturi 11 are due to the action of the control device 6 or the programming clock as soon as the maximum or minimum expansion thresholds are reached. .

 Other objects and advantages of the invention will appear on reading the following examples of implementation given in a non-limiting manner.

EXAMPLE 1 Case of the Continuously Vented Reactor
In a reactor having a volume of 350 l, the supply flow rate via line 14 is 29 l / h, treated water containing per liter:
- 0.53 ml of meat extract
- 200 ml of glucose
- 26 mg of urea
- 20 mg of KH2PO4
- 20 mg of R2HPO4
The residence time in reactor 2 is expected to be 12 hours; the circulation periods and their interruption are implemented by means of a programming clock.

 It is found that the abundance, characterized by the Mohlman index (MI) develops rapidly to reach values of 600 to 800 cm3 / g which makes it difficult or impossible to decant in the clarifier of Figure 1.

The periodicity of the operation being T and involving an application period T1, and T2 being the additional ventilation period, the method applied as follows:
. T = 6h including T1 = 20 mn
. T2 = 5 h 40
It is found that it has been possible to obtain an obvious improvement of the settling since a treatment not involving the 20 minutes of recycling and venturi passage leads to an impossibility of settling after an operation of the installation of a few hours.

EXAMPLE 2 Case of a reactor with denitrification
In the case of this example, the process consists of alternate acrobatic and anaerobic phases. This process is applied to the same waters as follows:
. T = 8h including T1 = 20 mn
. T2 = 4 h 40
. T3 3h being understood that the period T3 = T - T2 corresponds to the anaerobic operation of the installation (in which case the valve 13 is closed and the venturi does not work).

 Sequential aeration has been shown to improve water quality through nitrification and denitrification, in addition to improving water settling.

EXE # 1LE 3 Reactor case with denitrification
On the same waters, we operate as follows:
TT = 12 h including T1 = 20 min.

. T2 = 7:40
. T3 4 h being understood that the period T3 = T - T2 corresponds to the anaerobic operation of the installation.

 As in Example 2, there is a nitrification denitrification due to sequential aeration and improved settling. In addition, it is found that maintaining the value of 1M between 200 and 300 ml / g, one obtains higher purification rates than those obtained with healthy non-filamentous sludge.

The Mohlman Index (MI) is determined as follows:
1M = volume (in cm>) occupied by 1g of mud after 30mn of
decanting.

Claims (7)

 1. A method for controlling the filamentous expansion likely to occur in the water purification or fermentation reactors, which consists in performing sequential turbulent circulation phases, with or without aeration, on the reaction mass to be treated, these phases When the rate of expansion reaches a predetermined maximum level and for a period of time sufficient for this rate to reach an acceptable lower threshold value for further processing, the circulation rate is implemented.  2. A process according to claim 1, characterized in that the reaction mass to be treated is subjected to said sequential circulation phases.  3. A process according to any one of claims 1 or 2, characterized in that said circulation phases are performed on a fraction of the reaction mass returned to the reactor after having been decanted.  4.- Installation for carrying out the expansion destruction process according to any one of claims 1 to 3, characterized in that it comprises a venturi (II) creating a turbulent regime, arranged on a recirculation pipe bringing at the top of the reactor (2) the reaction mass to be treated when the expansion rate has reached a predetermined maximum level and until it reaches a defined lower threshold value.  5.- Installation according to claim 4, characterized in that the supply line is a line leading at the top of the reactor (2) the reaction mass removed in the reactor vessel (2).  6.- Installation according to claim 4, characterized in that the supply line is a line leading at the top of the reactor (2) the enriched sludge fraction withdrawn from the secondary settling tank.  7.- Installation according to any one of claims 4 to 6, characterized in that the venturi, in addition to the reaction mass, injects into the reactor air, or oxygen-enriched air.