FR2954763A1 - Installation for treating wastewater, comprises a membrane reactor, two sequential biological reactors working in alternating phase of aeration and settling/clarification, and a pretreatment tank in which crude water inlet opens - Google Patents

Abstract

The wastewater treatment installation comprises a membrane reactor (1), two sequential biological reactors (A, B) working in alternating phase of aeration and settling/clarification, and a pretreatment tank (3) in which crude water inlet opens. The biological reactors and the pre-treatment tank are associated with the membrane reactor and a contacting unit. Valves are provided between the different reactors and tank for directing the crude water, after passing through the pre-treatment basin towards one of sequential biological reactors and/or the membrane reactor. The wastewater treatment installation comprises a membrane reactor (1), two sequential biological reactors (A, B) working in alternating phase of aeration and settling/clarification, and a pretreatment tank (3) in which crude water inlet opens. The biological reactors and the pre-treatment tank are associated with the membrane reactor and a contacting unit. Valves are provided between the different reactors and tank for directing the crude water, after passing through the pre-treatment basin towards one of sequential biological reactors and/or the membrane reactor, and allowing a continuous treatment of waste water by the sequential biological reactors and/or the membrane reactor. The pretreatment tank is an anoxic tank. The pretreatment tank and membrane bioreactor are arranged between two sequential biological reactors, and comprise a common wall with each of the two sequential biological reactors. The sequential biological reactors comprise evacuation siphon to work at constant level. A transfer chamber is arranged between a wall of the installation and a wall of the membrane reactor. The transfer chamber is contacted with the biological reactors by the valves. An intermediate chamber is between the membrane bioreactor and the pre-treatment tank through a pipe provided with a valve. The biological reactors are semi-circular, and the pre-treatment tank is between two diametric walls of an overall circular contour.

Description

INSTALLATION FOR TREATING WASTEWATER.

The invention relates to an installation for the treatment of waste water, comprising at least one membrane reactor.

Membrane reactors, in particular those known under the name ULTRAFOR® (see Mémento Technique de l'Eau, 10th Edition, Volume 2, DEGREMONT SUEZ, pages 924 et seq.) Allow a wastewater quality treatment but pose a problem. a number of problems concerning: - getting started; - the unemployment of the membranes; - the seasonal variation of the performance and the adaptation of the performance 15 to the objectives of rejection; - replacement of air diffusers; - washing and handling of membrane cassettes; - compactness, - optimization of construction and operating costs. In particular, before putting the membranes into service, it is imperative to start the biology. This induces time, a delicate preparation and a significant cost.

The object of the invention is, above all, to provide an installation which facilitates the use of a membrane reactor, and which is of great flexibility of operation while allowing a level of treatment of good quality.

It is also an object of the invention to provide a relatively compact installation with as little investment cost as possible and simple maintenance to reduce running costs.

According to the invention, an installation for the treatment of wastewater, comprising at least one membrane reactor, is characterized in that it comprises at least two sequential biological reactors operating by alternation of aeration phase and of decantation / clarification, and at least one pretreatment basin in which the raw water inlet opens, the biological reactors and the pretreatment basin being associated with the

membrane reactor, means of communication and valves being provided between the various reactors and basin for directing the raw water, after its passage in the pre-treatment basin to one of the sequential biological reactors and / or the membrane reactor, and allow continuous treatment of the wastewater by the sequential biological reactors and / or the membrane reactor, or both in series.

Advantageously, the pre-treatment basin is an anoxic basin.

Preferably, the pretreatment pond and the membrane reactor are arranged between the two sequential biological reactors. Advantageously, the pretreatment basin and / or the membrane reactor comprise at least one wall in common with each of the two sequential biological reactors which frame them. Preferably, the sequential biological reactors comprise siphoid evacuations to work at a constant level.

Advantageously, the installation comprises a transfer chamber comprised between a wall of the installation and a wall of the membrane reactor, this transfer chamber being able to communicate with: the biological reactors by valves; - the pretreatment basin by a pipe with a valve; an intermediate chamber between the membrane reactor and the pretreatment basin via a pipe provided with a valve; the membrane reactor with valves located at the level of the liquid level, this membrane reactor being able to communicate with the intermediate chamber by valves situated in the lower part.

The sequential biological reactors may have a rectangular shape, as well as the pretreatment basin. Alternatively, the sequential biological reactors may be substantially semicircular and the pretreatment basin is between two substantially diametrical walls of a circular overall contour.

The invention consists, apart from the arrangements described above, in a certain number of other arrangements which will be more explicitly discussed hereinafter with reference to embodiment examples described with reference to the appended drawings, but which do not are in no way limiting. On these drawings:

Fig. 1 is a schematic plan view of an installation according to the invention. Fig. 2 is a schematic longitudinal vertical section along line II-II of FIG. 3 is a schematic longitudinal vertical section along line III-III of FIG. 1. Fig. 4 is an axial schematic vertical section along the line IV-IV of FIG. 1. Fig. 5 is a schematic vertical detail view of an evacuation and feeding along the line V-V of Fig.1. Fig. 6 is a schematic plan view illustrating the paths of the fluid in the installation when the biological reactor A is in the aeration phase while the reactor B is in the clarification phase. Fig. 7 is a diagram similar to FIG. 6 for a phase during which the biological reactor A is in the settling phase while the biological reactor B is in the emptying phase.

Fig. 8 is a diagram corresponding to a situation reversed with respect to that of FIG. 6. Fig. 9 is an operating diagram with implementation of the single membrane reactor. Fig. 10 is a diagram of a mixed operation.

Fig. 11 is a diagram giving the closed or open states of the various valves of the installation during the different phases of a treatment with the biological reactors alone, and FIG. 12 is a table similar to that of FIG. 11 for the twin operation of the membrane reactor with the biological reactors.

Referring to Fig. 1, we can see the schematic diagram of an installation according to the invention, for the treatment of waste water, comprising a membrane reactor 1, the membranes being assembled in the form of cassettes 2 schematized by rectangles.

The installation comprises at least two sequential biological reactors A, B working alternately aeration phase and decantation / clarification phase, and at least one pretreatment pond 3. The pretreatment advantageously corresponds to an anode pre-denitrification phase .

Aeration means, not shown, in particular nozzles at the floor, turbines, aerator pumps or ejectors, are provided

in reactors A, B, for blowing air, or oxygenated gas, when aeration phases are desired

The pretreatment pond 3 as well as the membrane reactor 1 are arranged between the reactors A and B. The different reactors and basin, in the example illustrated in FIG. 1 have a rectangular shape. However, other forms are possible. In particular, the reactors A and B could have a substantially semicircular shape while the whole of the basin 3 and the membrane reactor 1 would form a rectangle extending on either side of a diameter of the circumscribed circumference at both reactors A and B.

The raw water to be treated arrives in the pretreatment basin 3 via a pipe 4 which passes under the floor of the membrane reactor 1, to open in the lower part of the basin 3. The whole of the basin 3 and the membrane reactor 1 is delimited, on each longitudinal side, by a vertical wall common respectively with the reactor A and the reactor B.

Communication means and valves are provided between the different reactors and the basin.

Towards the end of the basin 3 remote from the membrane reactor 1, an opening provided with a valve A1 is provided in the lower part of the wall separating the reactor A from the tank 3. In the reactor A this opening is extended by a pipe horizontal 5 which, substantially half-width of the reactor back to the vertical according to a truncated cone 5a flared upwards to deliver water substantially halfway up the reactor, with a minimum of turbulence. When the valve A1 is closed, the communication is cut off between the tank 3 and the reactor A.

A similar arrangement is provided with a valve B1 between the basin 3 and the reactor B.

In the upper part of the reactors A and B, as illustrated in FIG. 2, perforated pipes 6, parallel to the longitudinal sides of the reactors, are provided at a level below the level L of liquid treatment. The pipes 6 are connected by a vertical branch 7 to a collector duct 815

transverse, horizontal, the position of which determines the constant level L of the reactors A and B. The transverse collector 8 is connected in its middle part to a discharge pipe 9 of the treated water. A valve A2 is disposed on the manifold 8 between the evacuation 9 and the outlets of the reactor A. A valve B2 is arranged in the same way between the evacuation 9 and the outlets of the reactor B.

At the end of the reactors A and B remote from the valves A1, BI is provided a transverse vertical wall 10a, 10b which stops (Fig.2) away from the bottom G to leave a lower passage 11 to a chamber 12a, 12b delimited by the wall 10a, 10b and the end wall 13 of the installation. A frustoconical chute 14 of vertical axis, whose large base is turned upwards, communicates by its small base with a transverse horizontal pipe 15. The large upper base of the trough 14, also called tulip, is located below the L level of liquid. The conduit 15 opens by an opening in a transfer chamber 16 between the vertical wall 13 of the end of the installation and a parallel wall 17 of the end of the membrane reactor 1. An orifice provided with a valve A3 is provided under the conduit 15 for communicating the chamber 12a and the reactor A with the chamber 16.The valve A3 is said to be "closed" when the orifice located under the pipe 15 is closed, and is called "open" when this orifice is open as shown in Fig.5. When the valve A3 is closed, the pipe 15 remains open towards the chamber 16. A similar provision is provided for the reactor B with a chamber 12b, a chute 14, a pipe 15, an orifice and a valve B3.

There is still communication between the reactors A or B and the chamber 16. The vertical chute 14 allows the clarification supply behind the vertical siphoid wall 10a, 10b. The lower orifice is provided because the flow rates through the valves can go up to 600% of the nominal flow rate, when the corresponding reactor is in aeration (nominal flow + 500% recirculation), while the flow that passes through the trough 14 in clarification will be only 100% of the input flow. One could have only communication through the chute 14, but it would require a larger pipe diameter.

The membrane reactor 1 consists of several compartments separated by parallel vertical longitudinal walls 18 extending from the vertical transverse wall 17 to another parallel wall 19. Each compartment delimited by the walls 18 comprises at least one cassette 2 of membranes. In each membrane compartment an opening with a valve

UE (FIG. 3) is provided in the wall 17 at a height such that the level L of liquid passes through the opening. A US valve (Fig. 3) is installed on another opening provided in the lower part of the wall 19, in each membrane compartment. The water filtered by the membranes is discharged through a pipe 20 connected by various connections to the outlets of the filtered water for each membrane cassette.

A transverse vertical wall 21 defines the end of the basin 3 away from the valves A1, BI. The transverse chamber E between the walls 19 and 21 has a transverse wall 22 of lesser height than the liquid level L. This wall 22 defines a wedging weir for an intermediate chamber 22a between the wall 22 and the wall 19. the space between the walls 21 and 22 are provided by submerged recirculation pumps 23 which discharge through pipes 24, crossing the wall 21, the mixed liquor from the chamber E to the basin 3. A partialization of the discharge can be ensured by providing a transverse wall T near the valves A1, BI, between them and the wall 21, which leaves a passage in the lower part; one or more pipes 24 are then extended to open on the side of the partition T opposite the reactor 1, and it is possible to recirculate a fraction of the liquid without passing through the basin 3.

The horizontal bottom wall lb of the membrane reactor is located at a distance above the bottom floor G of the installation, and extends from the wall 17 to the wall 21. The walls 19, 22 extend vertically only to the bottom lb, while the walls 17, 21 extend to the bottom G

A pipe 25 (FIG 3) is provided in the longitudinal direction, in the lower part, to pass under the membrane reactor and establish communication between the basin 3 and the chamber 16. This pipe 25 is provided with a valve AD to its outlet in the basin 3. Another pipe 26, in the lower part, passing under the membrane reactor 1 is provided to establish a communication between the chamber E and the chamber 16. This pipe 26 can be closed by a RM valve provided, for example, when he arrived in room 16.

That said, the operation of the installation is as follows.

Firstly, SBR (sequential biological reactor) operation alone is considered as illustrated in FIG. 6, 7 and 8.

The scheme of FIG. 6 illustrates a phase during which the reactor A is in aeration, while the reactor B is in clarification. The raw water arrives continuously through line 4 in the anoxic tank 3. The valve A1 is open while the valve B1 is closed as shown in FIG. 11. The water, after having undergone the pretreatment in the pond 3, passes into the reactor A in the aeration phase. Valves A3 and RM are open and valve B3 is closed. A fraction of the water is recycled via the pipe 26 to the chamber 22a while the other fraction enters the reactor B through the pipes 15 and 14 of the clarification feed and pushes, by piston effect, the water treated for its evacuation from reactor B to the outlet 9, the valve B2 being open, while the valve A2 is closed.

The next phase illustrated in FIG. 7 corresponds to decantation in reactor A; for this, the valves A1 and B1 are closed. The EU and US valves of the membrane reactor 1 remain closed to prevent pollution of the membranes.

The raw water which continues to arrive via the pipe 4 in the anoxic basin 3 comes out through the valve AD which is open. The water is directed to the chamber 16 and from there passes into the reactor B, the valve B3 being closed while the valve A3 is closed. The flow of water arriving through the valve AD and the pipe 25 is admitted into the reactor B, in clarification, by the pipes 14 and 15.

The next phase illustrated in FIG. 8 corresponds to a reversal of the phase of FIG. 6. The reactor B is placed in the aeration phase while the reactor A is in the clarification phase. The raw water continues to arrive via line 4 and, after passing through the anoxic basin 3, enters the reactor B because the valve B1 is open while that Al of the reactor A is closed. The water exits the reactor B through the valve B3 to arrive in the transfer chamber 16. A fraction of the flow passes through the pipe 26 because the valve RM is open and the other fraction of the flow passes into the reactor A because the valve A3 is open.

This fraction of the flow of water entering the reactor A ensures the emptying of this reactor by piston effect by pushing the treated water towards the evacuation, the valve A2 being open, while B2 is closed.

The alternation of the cycles with the two sequential reactors A, B makes it possible to continuously treat the raw water that arrives via line 4.

The plant can also work with the membrane reactor 1 alone. In this case, according to the example illustrated in FIG. 9, the raw water arrives via line 4 into the anoxic tank 3 and, after having undergone the pretreatment, passes into the reactors A, B because the valves A1, B1 are open. The water circulates in these reactors and leaves through the valves A3, B3 open to supply water to treat the compartments of the membranes with the EU valves open. The number of membrane compartments to be put into service is chosen in particular according to the flow rate of the effluent to be treated. It is possible to operate reactors A, B with or without aeration (denitrification, stress). It is possible to envisage alternate feeding of each reactor A, B.

The plant may also operate in a twinned or mixed manner with reactors A, B, and the membrane reactor 1. The water may be economically mixed with the discharge, or the treated water may be used for different purposes. In this case, the membranes are not fed in the settling phase, the EU and US valves being closed, to avoid pollution of the membranes.

Fig. 10 illustrates an example of mixed operation in which the water is treated in part by the reactors A, B and for another part by the membrane reactor 1. In this case, according to the example of FIG. 10, the water leaving the anoxic tank 3 passes through the open valve A1 into the reactor A which is in the aeration phase, the valve BI of the reactor B being closed. The water then passes into the chamber 16 through the valve A3 which is open. The RM valve is closed while at least one EU valve is open to supply at least one membrane compartment. The valve B3 is opened so that a fraction of the liquid passes into the reactor B, while another fraction passes into the membrane reactor 1. If Q is the flow of raw water arriving via the pipe 4, the flow With treated water leaving reactor B being designated Qx, the water flow rate treated by the membranes is equal to Q ù Qx.

The flow of mixed liquor recycled by the pumps 23 may be five times greater than the flow treated by the membranes, ie 500% of the flow rate treated.

The tables of Figs. 11 and 12 summarize the states of the different valves according to the different phases of treatment. Fig. 11 corresponds to operation in sequential biological reactor alone while FIG. 12 corresponds to the twin operation of the membrane reactor and the sequential biological reactor. The hatched boxes correspond to a closed state, while the dashed boxes correspond to an open state.

The installation of the invention relies on the integration of membranes in a SBR structure (sequential biological reactor) at constant level. The plant provides the biological treatment in free culture by an autonomous reactor that can be self-sufficient and the SBR biological reactor is separated into two cells A, B alternately acting as aeration tank and clarifier, and anoxia zone 3. It is possible to partialize the recirculation between anoxic zone and aerated zone.

The operation is very flexible and can be either in partial membrane treatment, corresponding to a partial reuse of the water treated by the membranes, either in total membrane clarification, or in conventional free culture.

The operation of the constant level SBR results from the alternation of the phases as explained previously. Nitrogen is perfectly treated in nitrification and denitrification. The installation makes it possible to start biology as a conventional biological reactor before commissioning the membranes, which simplifies operations.

30 The SBR provides a good level of treatment. It is possible to stop all or part of the membranes without significantly altering the level of treatment of the water. It is thus possible to replace the membranes by stopping a membrane compartment without creating a problem.

Due to seasonal variations (eg seaside resorts, winter resorts), it is not always useful to push treatment performance all year or all day. The installation allows to work either in SBR25

alone, either as membranes alone or as a mixture of both according to the techno-economic or environmental objectives.

The air diffusers in the reactor basins can be replaced without stopping the water supply. It suffices to operate reactor by reactor. In this case, the membranes will work in clarification. The installation will operate in partial mode for reactor intervention.

The integration of the membrane reactor in the structure makes it possible to set up a cassette per cell or compartment, and allows the various operations to be carried out, in particular washing, without handling the cassettes.

In addition to the benefits outlined above, integration allows for cost optimization. Compactness reduces link costs, pumping costs. Flexibility helps reduce operating costs.

The many possibilities give the installation undeniable advantages. In case of problems with the membrane reactor, a retreat is possible on the only SBR. 20

Claims (8)

REVENDICATIONS1. Installation for the treatment of wastewater comprising at least one membrane reactor, characterized in that it comprises at least two sequential biological reactors (A, B) operating by alternation of aeration phase and of settling / clarification phase, and at least one pretreatment pond (3) into which the raw water inlet discharges, the biological reactors and the pretreatment pond being associated with the membrane reactor (1), communication means and valves (A1, A3 , B1, B3, AD, RM, US, UE) being provided between the different reactors and basin to direct the raw water, after passing through the pre-treatment basin (3) to one of the sequential biological reactors (A, B) and / or the membrane reactor (1), and allow a continuous treatment of the waste water by the sequential biological reactors and / or the membrane reactor, or by both in series. 2. Installation according to claim 1, characterized in that the pre-treatment basin (3) is an anoxic basin. 3. Installation according to claim 1 or 2, characterized in that the pre-treatment basin (3) and the membrane reactor (1) are arranged between the two sequential biological reactors (A, B). 4. Installation according to claim 3, characterized in that the pre-treatment basin (3) and / or the membrane reactor (1) comprise at least one wall common to each of the two sequential biological reactors (A, B) which frame them . 5. Installation according to any one of the preceding claims, characterized in that the sequential biological reactors comprise siphoidal evacuations (6, 7, 8) for working at a constant level (L). 6. Installation according to any one of the preceding claims, characterized in that it comprises a transfer chamber (16) between a wall (13) of the installation and a wall (17) of the membrane reactor, this transfer chamber (16) capable of communicating with: - biological reactors (A, B) by valves (A3, B3); - the pretreatment basin (3) by a pipe (25) provided with a valve (AD) - an intermediate chamber (E) between the membrane reactor (1) and the pre-treatment basin (3) via a pipe ( 26) provided with a valve (RM); - the membrane reactor (1) by valves (UE) located at the level of the liquid level (L), this membrane reactor (1) can communicate with the intermediate chamber (E) by valves (US) located in lower part. 7. Installation according to any one of the preceding claims, characterized in that the sequential biological reactors (A, B) have a rectangular shape, as well as the pretreatment basin (3). 8. Installation according to any one of claims 1 to 6, characterized in that the sequential biological reactors are substantially semicircular and the pre-treatment basin is between two substantially diametrical walls of a circular overall contour.