MXPA97002430A - Aeration reactor with fl control - Google Patents

Abstract

The present invention relates to: In the aeration reactor described in the specification, an aeration receptacle has two aeration cells separated by a dividing curtain and connected in series so as to normally receive waste water in the first aeration cell and then pass the waste water to the second aeration cell which is followed by a clarifier to separate the slime from the waste water treated. A liquid level detector in the reactor responds to sudden currents in the rate of waste water flow through the reactor to redirect the incoming waste water and return the slime from the first aeration cell to the second aeration cell and isolate the first aeration cell to keep the active slime in that cel

Description

AERATION REACTOR WITH FLOW CONTROL BACKGROUND OF THE INVENTION This invention relates to aeration systems-to aerate waste water streams that undergo variable flow regimes. In certain wastewater treatment systems, a stream of wastewater is subjected to biological treatment in an aeration vessel containing active sludge followed by clarification in a clarifier. In many cases, the flow regime of the waste water entering the container is subjected to large variations resulting, for example, from sudden storms that produce a stream of rainwater into the drainage system from which the stream of Waste water is supplied to the aeration vessel. In such cases, the stream of waste water passing through the aeration vessel may carry much or all of the active slime or "biomass" in the aeration vessel and in the clarifier, causing a substantial delay in the restoration of water. biomass to the system to allow normal operation. To counteract this effect, Patent No. 3,549,521 to Stevens describes a two-stage treatment system. You give with an aerator and a clarifier in each stage and you have -valves arranged to connect the two stages either in series or in parallel. While the water flow regime of des-- The incoming wastewater is lower than a predetermined level, all the waste water to be treated passes through both ets_ pas in series, but when the flow rate exceeds a selected level, a portion of the incoming wastewater is divided directly to the second stage and the exit of the first stage is diverted to the exit of the system. At each stage, the silt is returned from the clarifier at the entrance to this stage or is supplied to the digester. This arrangement, however, does not prevent the problem of biomass loss from both treatment stages in the case of prolonged sudden currents. Patent No. 3,403,095 to ChiDperfield et al. Describes a waste water treatment system having a first biological treatment filter that delivers treated wastewater to a primary clarifier from which the effluent passes to a secondary treatment stage and then to a final clarifier during normal operation. When the rain causes a recurrent current that results in a flow regime that exceeds the capacity of the Dri-mario clarifier, a Dorsion of the output of the first biological treatment stage is diverted to the final clarifier, thus eliminating the primary clarifier and the secondary treatment for that portion and the portion passing through the primary clarifier and the secondary treatment stage can be diverted to the final clarifier. This provision also avoids the problem of loss of active silt from both stages during periods - prolonged from excessive slow regimes through the system. Patent No. 3,623,976 to Cessna discloses a waste water treatment system that includes a primary clarifier, a biological filter and a secondary clarifier that are normally connected in series. In order to avoid the loss of solids from the system during high load, a bypass is provided to divert incoming liquids around the primary clarifier and the biological filter then functions as a trickling filter, which inhibits the loss of active solids. This arrangement, however, requires a biological filter construction that can act as a percolating filter under these conditions.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an improved aeration reactor that overcomes the aforementioned disadvantages of the prior art. Another object of the invention is to provide an aeration reactor with flow control that responds to increased fl ow rates to conserve the biomass within the aeration reactor. These and other objects of the invention are achieved by providing an aeration vessel having two aeration cells separated by a divider provided with openings allowing the flow from the first aeration cell to the second - aeration cell and a clarifier that receives the output of the -second aeration cell. In accordance with one aspect of the invention, a flow control method is provided which directs the incoming waste water to the first aeration cell when the rate of waste water flow is less than a value. selecting and directing the waste water-entering the second aeration cell when the rate of waste water flow exceeds a selected level, thus diverting the first aeration cell and keeping the active solids therein during sudden currents in the water regime of incoming waste. In a pre-ferred mode, the silt removed from the clarifier is normally returned to the first aeration cell, but in response to the detection of an increase in the level of liquid in the clarifier, the silt removed from the clarifier is directed to the second cell. of -reaction to facilitate the treatment of waste water -which flows through it without attracting the active sludge in the first aeration cell. In accordance with another aspect of the invention, there is provided an area reactor with flow control in which the waste water inlet is connected to both the first and second aeration cells by lines having valves-which are selectively operable in response to a determination of flow rates to cause waste water to be directed to the first aerator cell at a flow rate slow and to the second aerator cell at a high flow rate. In addition, a silt return line from the clarifier is connected similarly to both the first and second aeration cells by lines having valves that are selectively operated in response to the determination of waste water flow rates. low and high. Preferably, the flow rate is detected by a liquid level detector arranged in the reactor and, in one embodiment, the liquid level detector is in the clarifier. If desired, an additional silt storage pond can be provided to store the excess silt removed from the clarifier.

BRIEF DESCRIPTION OF THE DRAWING Further objects and advantages of the invention will become apparent from reading the following description in conjunction with the accompanying drawing, which is a schematic flow diagram illustrating the diSDOSition of a representative mode of a aeration reactor having fl ow control according to the invention.

DESCRIPTION OF THE PREFERRED MODALITIES In the representative modality of a provision of aereation rector illustrated in the accompanying drawing, the waste water to be treated is received in an admi- - This is done by adding a filter or inlet 10 to a filter screen or filter 12 that removes the relatively large solid objects in a conventional manner and passes through a line 14 to a grit removal station 16 where the sand and gravel are removed. After passing through a flow measurement station 18, the incoming waste water is normally directed through an open valve 20 to a line 22 leading to an inlet 24 to a first aeration cell 26 in an aeration vessel 28 Normally, a valve 30 on a line 32 leading to a second aeration cell 34 in the vessel 28 is closed, thus requiring that all the waste water be supplied to the inlet 24 of the first cell of aeration The waste water within the first aeration cell 26 is aereated, for example, by means of two movable aerating chains 36 and 38 which can be of the type described in the patent No. 4,287,062 of von Nordens Jold, the exposure of which is incorporated the present by reference. As described therein, each of the chains 36 and 38 is floated on the surface of the liquid in the cell and a series of aerators (not shown) suspended from the chains 36 and 38 are disposed near the bottom of the cell for receiving air under pressure from a line 40 connected to a blower 42. As described in patent No. 4, 287,062, the supply of air to the suspended aerators causes lines 36 and 38 to oscillate inside the aeration cell 26, aerating the waste water and stirring towards up the silt that was collected at the bottom of the cell to Complete biological treatment of the waste water that passes through the cell. The second aeration cell 34 is separated from the cell 26 by a curtain divider 44 having window fins that allow the waste water to flow from the cell 26 to the cell 34, but inhibit the flow in the direction -option opposite. Cell 34 is similarly provided with area 46 and 48 that are supplied with air under pressure from line 40 and operate in the manner described with respect to chains 36 and 38 of aeration in the cell. 26. In this form, the aeration cells 26 and 34 are connected in series during the normal operation of the aeration reactor. Following the sequential treatment in cells 26 and 34 of first and second aeration, the waste water passes through an outlet 50 to a clarifier 52 where the solid material in the waste water is separated by sedimenting from the liquid and liquid. The supernatant is then passed over a floating overflow 54 inside the clarifier and then through two adjustable clarifier outlet valves 55 of an effluent line 56 leading to a disinfection channel 58 from which the purified waste water passes to the disinfection channel 58. a 60 line of output. The size of the openings in the outlet valves 55 is controllable, thus allowing control of the rate of waste water flow that can pass through the system. subject without causing the level of liquid in the clarifier to rise and also resulting in the liquid being discharged from the system at the required rate during sudden currents. The silt collected at the bottom of the clarifier 52 is returned to the aeration vessel through a line 62 and in normal operation a valve 64 is kept open to transport the slime to a line 66 leading to the intake line 22 that supplies the input 24 for the first aeration cell 26. Another valve 58, which connects the silt return to the second aeration cell is normally maintained in the closed condition. The excess silt of the clarifier 50 can be made Dasar, if desired, through a line 72 to a storage vessel -72. According to the invention, when the rate of flow of the incoming waste water to be treated exceeds a selected level, the first aeration cell 26 is added and all the incoming waste water is directed towards the second. aeration cell 34 to conserve the biomass in the first aeration cell until the sudden current in the flow regime has ended. In one embodiment, this change is effected by providing a liquid level detector 74 in the clarifier 50 which responds to the detection of a liquid level in the aeration reactor that is greater than a selected value, - indicating a sudden current in the wastewater glucose regime, to provide signals on a line 76 to Rotate the valve 20 and open the valve 30 to direct the incoming waste water through the line 32 to the second aeration head 34 and to close the valve 62 and open the valve 66 It will direct the returned silt of the clarifier towards the second aeration cell 34 instead of the first cell 26. In an alternative embodiment, the floating overflow 54 and the adjustable outlet vials 55 replace the outlet 50 to the clarifier at the end of the aeration zone and the detector 74 of - Liquid level is arranged with the second aeration cell 34. With this arrangement, the clarifier Duede can be separated from the aereation receiver. Further, when the liquid level in the aerating reactor reaches an upper limit, the liquid level detector supplies signals on a line 78 to open the outlet valves 55 and increase the flow rate from the reactor. In this way, the active slime in cell 26 is conserved during the sudden current and all the returned sludge from the clarifier goes directly into cell 34 to facilitate the treatment of the incoming stream of waste water. Preferably, the aeration lines 36 and 38 in the first aeration cease 26 continue to operate while the cell is isolated, thus maintaining the silt in circulation in the cell so that it is ready to reactivate the cell. at the termination of the sudden current. Alternatively, however, the air line 40 could be disconnected from the lines 36 and 38 of aeration when cell 26 is not in operation. As described above, since the clarifier output valves are adjustable, the flow regime that causes an elevation in the level in the clarifier can be controlled to determine the rate of waste water flow to which the level detector 74 will be activated to change the valves 20, 30, 62 and 66. Consequently, the clarifier outlet valves can be adjusted to a desired setting based on the flow rate that will cause a loss of biomass. Instead of using a level detector 74 in the clarifier 50 or in the aeration cell 34 and supplying signals therefrom in the line 76 to control the valves 20, 30, 62 and 66, those valves could be controlled, if desired , from the flow measurement device 18 supplying signals on a line 80 to the valves in the manner described above. Although the invention has been described herein-with reference to specific embodiments, many modifications and variations therein will readily occur to those experienced in the art, for example, the aeration reactor could include three or more aeration cells. normally connected in series and the first one or two of those cells could be isolated during a sudden current condition. Consequently, all these variations and modifications are included within the intended scope of the invention.

Claims (13)

CLAIMS:

1. - A process for treating wastewater in an aeration reactor that normally comprises making water from waste to be treated through a first aeration cell containing active sludge and aerating the water from runoff in the same to treat waste material carried by the waste water, to pass the waste water from the first aeration cell to a second aeration cell, to aerate the waste water in the second aeration cell - to further treat the waste material carried by the wastewater, or, passing the waste water to a clarifier and allowing the solid material carried by the wastewater to sediment in the clarifier and discharge the supernatant liquid from the clarifier to an outlet , stop a change in the rate of waste water flow through the aeration reactor, isolate the first aeration cell in response to n increase in the rate of waste water flow to a level higher than a level selected to retain active solids in the first aeration cell while substantially directing all the waste water to be treated to the second aeration cell until the flow rate returns to a level below the selected level

2. - A method according to claim 1, which includes the steps of detecting a change in the flow regime wastewater by detecting a variation in the level of liquid in the aeration reactor, and controlling valves in an intake line to direct incoming waste water to either the first aeration cell or the second cell of aeration in accordance with the detected level of liquid in the aeration reactor.

3. A method according to claim 2, which includes the step of controlling an output of the clarifier to cause a variation in the level of liquid in the clarifier when the rate of waste water flow reaches a selected value.

4. A method according to claim 2, which includes the step of controlling an output of the second aeration cell to cause a variation in the level of liquid in that aeration cell when the water flow rate of - Waste reaches a selected value.

5. A method according to claim 2, which includes the steps of returning slime from the clarifier through a silt return line to the aeration receptacle and controlling the valves in the silt return line to direct the slime to either the first aeration cell or the second aeration cell in accordance with the level of liquid in the clarifier.

6. A method according to claim 1, which includes the step of detecting the water flow rate of waste by measuring the flow rate of an incoming waste water line leading to the aeration receptacle.

7. An air aeration reactor for aerating water comprising an aeration vessel, at least one divider for dividing the aeration vessel into at least two cells normally connected in series, aeration elements for aerating the water of waste in each of the aeration cells, a clarifier to receive waste water to be returned from the aeration receptacle, an incoming line to supply waste water to the aeration receptacle, and flow control elements to control the wastewater flow from the inlet line to either the first aeration cell or a subsequent aeration cell conforming to the rate of wastewater flow through the aeration vessel.

8. An aeration reactor in accordance with claim 7, which includes valve lines connecting the waste water inlet line to the first aeration cell and to a subsequent aeration cell., respectively, and control elements to control the valves in the lines -with valve in accordance with the flow regime supplied to the aeration receptacle.

9. An aeration reactor in accordance with claim 7, which includes silt return elements for returning silt from the clarifier to the aeration receptacle and Valve elements for controlling the return of the sludge to either the first aeration cell or to a subsequent aeration cell in accordance with the rate of flow of waste water through the aeration receptacle.

10. An aeration reactor in accordance with claim 8, which includes a liquid level detector in the aeration reactor, to detect the liquid level in the same and control the lines with valve to supply waste water. incoming either to the first aeration cell or to a subsequent aeration cell in accordance with the liquid level in the aeration reactor.

11. An aeration reactor according to claim 10, wherein the liquid level detector is disposed in the cleaner.

12. An aeration reactor in accordance with claim 11, wherein the clarifier includes a floating overflow and controllable outlet valves that are adjustable to control the rate of waste water flow which the liquid level in the clarifier it will rise.

13. An aeration reactor according to claim 7, wherein the aeration element includes when less than one movable aerator chain in each of the aerator cells and a plurality of aerators suspended from the chain of aeration. aerator to aerate the waste water while maintaining the circulation of active silt.