EP0437465B1

EP0437465B1 - Method and apparatus for removing sludge and purifying waste water

Info

Publication number: EP0437465B1
Application number: EP89910950A
Authority: EP
Inventors: Bo Larsson; Ingemar Larsson
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-09-27
Filing date: 1989-09-27
Publication date: 1993-03-03
Anticipated expiration: 2009-09-27
Also published as: EP0437465A1; SE8803405D0; NO911152L; DE68905194D1; DK51391D0; NO911152D0; NO309617B1; WO1990003474A1; DK51391A; AU4326689A; DK172496B1

Abstract

A method and a device for a disposal and a purification of sludge and waste water, comprising a mobile unit (1), preferably a tank truck having a sedimentation basin (3) with a ski table box (11) and a reject water space, isolated by means of perforated walls (16), and comprising a rotary screen drum (4), disposed upstreams of said sedimentation basin (3), and a sludge press, connected to said screen drum. Also, a tank for precipitation chemicals is connected to the screen drum. The waste water is purified, particularly as to the biochemically oxygen-consuming material. On its way to the sedimentation basin precipitation chemicals are added in order to precipitate phosphorus and the suspended substance from the waste water. The purified water flows into a ski table box and subsequently flows to the reject water space in order to drive an ejector pump and the water excess is returned to the waste water well.

Description

The present invention relates to a method of removing sludge and purifying waste water according to the preamble of claim 1. Also, the present invention relates to a device designed to remove sludge and purify waste water according to the first device claim.
The modern way of treating sludge and waste water is unsatisfactory for several reasons. Wells for waste water e.g. must be emptied at intervals, which usually is done by a so called sludge exhaustion to a tank truck, which subsequently empties the waste water into a stationary purification plant, Such transport can be most time and energy consuming and existing purification plants often have a limited capacity, and consequently the disposal of irregularly collected waste water can result in problems.
From GB, A, 1 460 031, a method and a device are known in which sludge and waste water are pumped up from a waste water well into a purification device, The purification device includes a screen. The purified water is to be fed to and stored, respectively, in a reject water compartment, from which the same by means of a pump is to be fed under pressure to an ejector nozzle. The nozzle is immersed into said well. The medium is restored, while it is co-ejected with unpurified sludge and waste water present in the well via a conduit to a gravity separator tank and subsequently into a separator vehicle including said screen on its way to the reject water compartment.
Thus, the object of the present invention is to create opportunities for a less time and energy consuming handling of waste water, Another object of the invention is to, in several other respects, develop the state of the art in this field.
These objects are attained according to the present invention by performing a method of the type suggested in the introduction in the way set forth in the characterizing clause of patent claim 1. Said objects are also attained by means of a device, which mainly is constructed in the way set forth in the device claim 3.
Additional characterizing features and advantages of the invention are set forth in the following description, reference being made to the attached drawings, which schematically show preferred embodiments designed to perform the method according to the invention and of the device according to the invention respectively. The drawing show in detail:

Fig. 1 a first embodiment of a mobile device according to the invention in a lateral view;
Fig. 2 a second, preferred embodiment of such a device in a lateral view;
Fig. 3 a third, also preferred embodiment of such a device in a lateral view;
Fig. 4 a view from above of the device according to Fig. 3;
Fig. 5 a perspective view of a drum screen, which is a component of at least some of the above-mentioned devices;
Fig. 6 is a lateral view of a drum filter, which is a component of at least some of the above-mentioned devices; and
Fig. 7 is a lateral view of an ejection nozzle, which is a component of said devices.

In Fig. 1 a device 1 is shown, which e.g. is mobile, particularly a tank truck, on the platform 2 of which a unit 4 for course separation and a unit 3 for fine separation are mounted. The exterior of the latter can be designed as a sedimentation basin, while the former includes a filter 23 and a sludge press 5. A tank 6 can be mounted below unit 4 as well as a distribution equipment, not shown in detail, for precipitation chemicals. The sludge press and the screen are connected to each other through a passage 7 and the screen and unit 3 through a passage 8, while a compressed-water conduit 18 is connected to a well 10, which contains sludge and waste water and a transport conduit 9 connects the well to unit 4. In the sedimentation basin overflow box 11 is positioned, from which one or several conduits 12, through closed or perforated partitions 16, lead to the suitably laterally positioned lower areas of the basin, namely the so called reject water compartments 19, from which one or several conduits 14 via a pump 22 lead to compressed-water conduit 18, while one or several conduits 13 are designed to transport separated impurities back to unit 4. The entire process preferably is remotely controllable by means of a radio control unit 15.
A preferred working cycle is performed in the following way: purified water from compartments 19 is pumped by means of pump 22 via conduits 14 and 18 to an ejector nozzle 17, which is mounted at the free end of the latter conduit and immersed into e.g. a three-compartment septic tank and in which the pressurized water is injected into the inlet by conduit 9, a strong suction effect being obtained, which pulls along the waste water and sludge present in the well, which subsequently are transported to coarse separation unit 4, which can be designed as is shown in Fig. 5 and is described more in detail in the following. In unit 4 the screen suitably is designed as a rotary drum 23. That waste water, from which coarse impurities have been removed in unit 4, i.e. the prepurified waste water, is subsequently transported to unit 3. On its way precipitation chemicals suitably are added in order to precipitate e.g. phosphorus and possibly also nitrogen, in addition to the suspended material, from the waste water. The precipitation of the flocculated material must be done quickly and consequently a turbulence to some extent in the conduit to the fine separation unit is required.
The water subsequently is lead into the central portion of unit 3, in which the flocculated material is allowed to descend to the bottom and in which the water, which in this way has been purified to a greater extent, is allowed to flow over from overflow box 11 in order to be lead, through the lateral walls 16, suitably solely via conduits "12", to the reject water compartments. The purified water is used, as has been mentioned, to drive the ejection device, The excess can be returned to the well. It is e.g. possible to evacuate and purify the entire contents of a well and subequently or continuously bring back the purified water. The word "continuously" means, that the restoration of purified water can be done also before the sludge suction operation is concluded. Coarse impurities accumulated in the drum screen and chemical sludge brought back to the drum screen are concentrated and brought to the sludge press, which suitably is actuated at the same time a the drum screen, and subsequently the sludge press is run intermittently. The compressed waste material can be collected in e.g. plastic bags and the press water can be recycled to the process.
It has already been indicated, that portions of the various figures and embodiments respectively may be exchanged or be combined in an arbitrary manner.
The embodiment shown in Fig. 2 is similar to the preceding one. However, the fine separation is not done via an over flows box but is done by means of a drum screen 20. the drum screen comprises a drum 21 having a pervious, e.g. perforated support surface 24, which is covered by a filter cloth 25. However, the waste water, with all its sludge and all its impurities, firstly flows to drum screen 23, which according to Fig. 5 comprises a perforated drum 31 having an internally fastened feed screw 26. The drum is inclined towards inlet 27 with e.g. 5-30°, preferably about 5°, while outlet 28, at a higher level, is designed to feed out separated coarse impurities, or a so called sludge, which on its way to the outlet is dewatered continuously and subsequently falls out through a collection funnel 29, which is mounted below the outlet, from which it is transported further, e.g. through the gravitation, to sludge press 5, in which an automatic dewatering takes place and a so called susage is built, which subsequently is collected in e.g. plastics bags. The reject water from the sludge press and also the water, which flows through the screen drum, are collected, e.g. in a vessel 30 below the screen drum and are pumped back to unit 3, suitably via a collection tank 54, which is positioned below unit 3, by means of a pump 32, which is mounted in passage 8. Passage 8 can be connected to conduits 33, 34 from dosing devices, not shown, for chemicals of type mentioned, which are fed from tanks 6, as has already been mentioned. A pump 35,36 can be mounted in each one of conduite 33 and 34 respectively and belongs to the dosing device, which is not shown for the rest but is known in principle.
While the drum filter in Fig. 3 is mounted with its longitudinal direction perpendicular to the longitudinal direction of the vehicle or the like, which carries the purification device, in Fig. 2 it is mounted in the longitudinal direction of the vehicle. However, the principal construction can be the same. It is shown if Fig. 3 , that the coarsely purified water, by means of pump 32, is pumped from container 31 to unit 3, which all around is designed as a mainly closed container, in which the coarsely purified water surrounds the drum filter and passes through its cloth and perforations, fine solid or semi-liquid particles being separated. The water, which has been filtered in this way, subsequently flows from the interior of the drum filter via a hollow shaft 37, which is positioned at the end of the filter, and a vertical shaft 38 (see also Fig. 6), up to an outlet 39 and is discharged into a reject water tank 19. The accumulation of particles on the filter cloth reduces the perviousness of the cloth and the water surface level is unit 3, which also can be called a filter chamber, increases. When the maximum level 40 has been reached, a level control is actuated and activates, in a mechanical or preferably in an electronic way, a filter cleaning process, which is done through a suction with a nozzle 41, which is engaging the drum in the form of a ramp along the entirety of the drum, stuck particles being sucked by means of a pump 42 but also surrounding water and even water from the interior of the drum, which is sucked through the cloth, which in this way is rinsed efficiently. This sucked-off mixture can, via a passage 43, be restored to unit 4. Since the drum, which is driven by a motor 44, is rotating during the purification phase, a comprehensive efficient cleaning is accomplished. By means of a special filter cloth, known per se, it is possible, when a filtration is done, after a chemical precipitation, to separate very small particles, e.g. iron and aluminum phosphate, it being possible to obtain as low as 0.2 mg/l total phosphorus and 5 mg/l SS (= suspended substance). The texture of the cloth makes it possible also separate particles having a very low mechanical strength and stability. A filter cloth having the described desirable properties can be bought on the market under the trade name MEKANAFILTER TYP 102.
Furthermore, in Fig. 6 a minimum level 45 is shown; when this level is reached, the purification device can be stopped, while a security outlet 46 can be used, in case outlet 39 is blocked up. It is shown in Fig. 3, that nozzle 41 or pump 42 has an arm 47, which extends downwards to the area below the drum. This arm is an auxiliary nozzle, possibly in the form of a ramp, designed to suck off accumulations of impurities below the drum. This auxiliary nozzle suitably can be connected separately. Nozzle 41 can be fastened and adjusted respectively in various position by means of fasteners 48 and 49 respectively.
By means of the nozzle shown in Fig. 7 the following performances can be attained:
The main advantage of this combined pressure and suction action is that large lifting heights easily can be obtained, that no pump stop-up can occur and that desirable combinations of pressure in nozzle/amount of pressurized water/amount of waste water or sludge/lifting height easily and steplessly can be obtained. Fig 7 shows that nozzle 17 is provided with fasteners for conduits 9 and 18, the former having a larger diameter in order to hold the two types of medium, i.e. pressurized water Q₁ and waste watre-sludge Q₂. Nozzle 17 has a jet 51. This jet is provided with surrounding outer restrictions at a distance, which can be perforated or have meshes. The characterizing features described above and shown in the drawings are only non-limiting embodiments of the invention, which can be modified and supplemented in an arbitrary way within the scope of the following patent claims. Thanks to this ejection principle i. a. a dilution and a more practical treatment of the occuring impurities are achieved.

Claims

A method of removing sludge and purifying waste water, which are pumped up from a waste water well, a three-compartment septic tank or the like (10) and into a tank truck or another mobile or stationary purification device (1), the water, which is fed by pumping, being brought through screens (23) and/or filters or the like (20) in order to purify it, at least a portion of said water, after having passed said screens, filters or the like, by means of a pump (22) via a primary or pressurized water conduit (18), being fed under pressure, e.g. between 5 and 10 bars, into an ejector nozzle (17), which is immersed into said well or the like (10) and is restored, while unpurified sludge and waste water present in the well are co-ejected in order to obtain i.a. a dilution and a more practical treatment of occuring impurities, via a secondary or transport conduit (9) to said screens, filters or the like, namely a coarse separation screen (23), characterized in that a rotary drum is used as a screen for treating coarse impurities, subsequent to which said water is passed through fine separation means (20), on its way to reject water compartments (19), from which the purified is returned to said ejector nozzle (17), that the pre-purified water is passed through a collection tank (31), from which it is pumped to a fine separation unit (3), preferably while adding chemical precipitation agents, particularly in order to precipitate phosphorus and possibly also nitrogen, and that the prepurified water is passed from the exterior into the interior of a drum filter (20, 21, 24, 25) and from there out through an axial outlet (37), via a shaft (38) and an outlet (39) from said shaft to a reject water tank (19), the waste water level in said fine separation unit (3) being measured and connected to a cleaning device (41,42,47,48,49) for the drum filter in order to connect and disconnect said device.
A method according to claim 1, characterized in that the pressure in the ejector nozzle (17), which is generated by the pump (22) is used to steplessly adjust the ratio: amount of pressurized water/amount of waste water and sludge/lifting height.
A device for performing the method according to claim 1, in which sludge and waste water, which are to be purified, separated and removed respectively, are pumped up from a waste water well, a three-compartment septic tank or the like (10) and into a tank truck or another mobile or stationary purification device (1), which includes screens (23) and/or filters or the like (20), which are for a purification of the pump-fed medium, the purified water is provided to be fed to an stored, respectively, in a reject water compartment (19), from which the same by means of a pump (22), via a primary or pressurized water conduit (18), is to be fed under pressure, e.g. between 5 and 10 bars, to an ejector nozzle (17), which is immersed into said well or the like (10), and be restored, while it is co-ejected jointly with unpurified sludge and waste water present in the well in order to obtain i.a. a dilution and a more practical treatment of occuring impurities, via a secondary or transport conduit (9) to said screens, filter or the like, namely a coarse separation screen (23), characterized in that the latter is a rotary drum for the separation of coarse impurities, which drum is followed by fine separation means (20), which are to be passed by said water, from which the coarse impurities have been removed, on its way to said reject water compartment (19), from which the purified water is to be brought back to said ejector nozzle (17), that the pre-purified water is provided to be passed through a collection tank (31), from which it is pumped to fine separation unit (3), preferably while adding chemical precipitation agents, particularly in order to precipitate phosphorus and possibly also nitrogen, and that the prepurified water is provided to be passed from the exterior into the interior of a drum filter (20,21,24,25) being effective as fine separation means and having an axial outlet (37), via a shaft (38) and an outlet (39) from said shaft to a reject water tank (19), the waste water level in said fine separation unit (3) being measured and connected to a cleaning device (41,42,47,48,49) for the drum filter in order to connect and disconnect said device.
A device according to claim 3, characterized in that said coarse separation unit (4) is designed to feed a sludge press (5) with the separated coarse material, which press is provided with packing means for the dewatered compressed coarse material.
A device according to claim 3, characterized in that said fine separation unit (3) is designed as a sedimentation basin, in which an overflow box (11) is disposed, from which one or several conduits (12), through closed or perforated walls (16), leads to preferably laterally disposed reject water compartments (19), from which conduits (14), via said pump (22), lead to said pressurized-water conduit (18), while conduits (13) are designed to feed separated impurities from the lower part of said sedimentation basin back to said coarse separation unit and a renewed coarse separation treatment.
A device according to claim 3, characterized in that a drum filter (20) is mounted in the fine separation unit (3), which filter comprises a drum (21) having a pervious, e.g. perforated support surface (24), covered with a filter cloth, which drum filter is designed to radially from its exterior and to its interior receive pre-purified medium from the coarse separation unit (4) for a fine separation and to discharge the medium, purified in this way, through a hollow shaft (37) to a vertical shaft (38), which via an outlet (39) leads to the reject water compartment (19), and outside the drum filter a cleaning device (41,42) being mounted, mainly comprising nozzles (41) and a pump (42) for suction of impurities from the exterior of the drum filter and transport of the same to the coarse separation unit, which cleaning device preferably also comprises a nozzle ramp and can be connected and disconnected by means of level controls (40,45) in the shaft (38) and/or in the space surrounding the drum filter.
A device according to any of claims 3-6, characterized in that said drum screen (23) in the coarse separation unit (4) comprises a perforated drum (31) having a feed screw (26) fastened in its interior, which drum is inclined downwards towards the outlet of the transport conduit (9), which outlet also is the inlet (27) of the drum screen, with 5-30°, preferably about 15°, while the outlet (28) of the drum, at a higher level, is designed to discharge separated coarse impurities, which are to be continuously dewatered on their way to the outlet (28), the water obtained in this way being designed to flow downwardly into a vessel (30) and be pumped back to the fine separation unit (3), suitably via a collection tank (54) positioned below, by means of a pump (32), mounted in the passage (8) between the two units, to which passage preferably conduits (33,34) and pumps (35,36) are connected in order to feed chemicals from tanks (6) containing said chemicals.