SE530649C2 - Purification of e.g. drinking water or effluent, by passing liquid through jet injector and adding chemicals before supplying to flocculator and flotation unit - Google Patents

Abstract

Liquid is passed through a jet injector (41) where chemicals are added and then supplied to a flocculator (10) to remove heavy particles and to a flotation unit (13) to remove light particles. A method for purifying liquids such as drinking water, wastewater, sewage or industrial effluent comprises separating the particles which are heavier and lighter than the liquid and supplying them to reservoirs, adding solid and/or liquid flocculating agents to the liquid and passing the liquid through a flotation installation. The liquid is initially passed through a jet injector in order to generate turbulence and where chemicals are added, then it is supplied to a flocculator where the heavy particles are separated and removed to a collection vessel and then it is supplied to a flotation unit where the light particles are separated and removed to a collection vessel. Independent claims are also included for the following:Flotation unit, comprising a liquid inlet pipe at the lower end, a vessel with an open top end and relatively narrow outlet tube at its bottom end, a scraper for removing flocked material from the top end of the vessel, a funnel located inside a vertical pipe having an open bottom end in liquid communication with the vessel and an outlet pipe connected to the bottom end of the funnel for removing purified liquid from the unit; and #Process apparatus for carrying out this method.

Description

The carrier liquid is separated at the lower end of the container, while the particles which are lighter than the carrier liquid are scraped off at the top of the container.

In order to achieve good purification effects when purifying liquids, one is dependent on using an auxiliary coagulant in the form of a polymer and an optimal rapid mixing and occlusion.

It is well known that when a suitable polymer is introduced together with a coagulant, both the mixing and occlusion conditions change, and not least the sedimentation rates and thereby dimensioning surface loads.

The present invention is a further development of the solution according to the above-mentioned Norwegian patent specification No. 156,975 and comprises a method for cleaning liquids and an totation unit intended for this, in accordance with the appended claims.

An object of the invention is to achieve an improved control of the separation process and an optimized process with improved efficiency in purification of the liquid to be purified.

Another aim of the invention is to improve the purification effect achieved with the solution according to the above-mentioned Norwegian patent specification.

Another object of the invention is to ensure an optimal mixing of chemicals in the liquid stream upstream of the occultator, so that the occultator functions optimally.

A further object of the invention is to ensure an optimum effect in the occultator by adjusting the supply of chemicals to the liquid upstream of the occultator and the rotational speed of the stirrer depending on the amount and volume of the liquid entering the occultator.

A further object of the invention is to improve the totation process both with respect to the properties of the dispersing liquid being added and the flotation process inside the flotation unit.

The purification process according to the invention comprises the use of a surface coagulant which is added to the liquid in a dosing unit, followed by a dynamic ulator occulator placed in front of an flotation unit. The dosing unit or rapid mixing unit is arranged at the dosing point. Experience shows that it is important to distribute the coagulant evenly in the water masses so that the time it takes for the chemicals to reach all the particles in the liquid stream is as short as possible and preferably within a second. In order to optimize the mixing of the coagulant, it may be advantageous to introduce the coagulant into a turbulent stream and with an inlet direction which is substantially parallel to the main stream direction of the liquid stream.

Flotation requires significantly less fl ocher than sedimentation. In addition, an auxiliary coagulant, in the form of a polymer, will build up the flocks faster and give greater ox strength so that the ox does not break as easily and allows for better reformation if some ox breaks. Therefore, a shorter residence time can also be used in the ul occulator.

Dynamic occlusion is an efficient occlusion method and requires significantly lower flocculation times than conventional paddle agitators. By dynamic fl occlusion is meant an fl occulator where the energy drive (G-value) changes dynamically in relation to variation in the incoming water volume.

Flocculation in tubes in 3 steps has been previously described, with the following divisions: 10 15 20 25 30 530! E49 4 A. Rapid mixing of coagulant into the raw water where the coagulant is introduced perpendicular to the direction of flow with: 1000 - 5000 / second 0.1 - 1.0 second G-value: Residence rate: B. Aggregation (tlockulcring) leading to microarrays: 200 - SOU / second 15 - 30 seconds G ~ care: Residence time: C. Aggregation (fl occlusion) leading to inacrotlocks: a. Without auxiliary coagulant: G-value: 20 - SO / second Residence time: 300 - 1000 seconds b. With auxiliary coagulant: G -value: 50 ~ 120 / second Residence time: 20 - 200 seconds This direnition set has been set up in relation to particle separation in a circular sedimentation tank system with tangential inlet arrangement.

Experience from this can also be used when dimensioning the flocculation unit for an flotation system.

The flotation unit according to the invention is based on flotation which requires slightly smaller fl yokes. The G-values can either be slightly higher or the residence times slightly lower.

When auxiliary coagulant is used, the G-values can be increased approx. 2.5 times while the residence time can be reduced to approx. 1/15 on the lower limit to 1/5 on the upper limit. Reduced residence time or occlusion time when using an auxiliary coagulant means that the occlusion volume can be significantly reduced.

For verification of flocculation calculations, a calculation model is used based on: 10 l5 20 25 530 649 5 “Camp number” (dimensionless) = G-value (per sec) * t (residence time in seconds) This number is important because the product should be within a certain area. If the G-values are too low, the flocks build up more slowly and a longer fl occlusion time is needed to complete. On the other hand, if the agitation intensity (G-value) is higher, it is possible to cope with a shorter time and the Camp number becomes almost constant. The risk is that the locks become so large that they are crushed at too high G-values.

In a dynamic flocculator, the "Camp number" becomes relatively constant but not complete.

In a plant for separating liquids, the variation in the amount of water will normally be significant and this will require that the occlusion conditions are constantly adapted to the variation in order for the occlusion to be optimal at all times. In an flotation unit according to the invention, the variation in the amount of water will normally be significant and require constant flocculation conditions regardless of the amount of water loaded. This is solved in an advantageous manner according to the invention with a dynamic stirrer. In order to achieve the best results and the greatest possible flexibility, a combined vertical dynamic occulator with a mechanical stirrer as an occlusion step has thus been developed.

In terms of process, this is placed before the enotation unit according to the invention. When the raw water is led to the totation unit, a main coagulant is added to a dosing unit.

This system is “in line” and is based on “jet injection” of the coagulant into the flow tube and where the precipitation chemicals are dosed along the flow direction in a turbulent area to ensure optimal mixing in the tube within a maximum of 0.5 ~ 1.0 sec. It also means that the coagulant must be fed continuously. The diaphragm pump for feeding the coagulant used is therefore of a type which has a leveling system. l0 20 25 30 53Û 549 6 After mixing coagulant and wastewater, the water is passed further into a dynamic flocculator. The feed tube to the dynamic occulator will contribute a certain tube occlusion while the particles are very small.

In terms of calculation, important characteristics of the liquid stream to be separated are first clarified. This applies in particular to temperature, variation in the amount of water and particle content or suspended substances in the liquid. These data are used as a basis for calculating the dynamic ulcuctor with regard to the necessary residence time, volume and necessary G-values, which in turn provide the necessary area and shape that must be established on the paddle stirrers and the required rotational speed range. After dimensioning a dynamic ulator occulator, this will be physically a constant, but where the speed of the paddle stirrers varies according to incoming water. This is done by registering incoming water inlet and a prepared setpoint curve for speed for the PLC automation (PLS: Programmable logic control) for the system so that each water inlet corresponds to a setpoint for the intruder. The signal from the PLC unit is sent to a frequency converter which in turn controls the speed of the motor on the agitator.

The solution of the present invention will be described in more detail below with reference to the figures, in which: Figure 1 shows a flow chart of essential, but not all, parts of a purification process according to the present invention; Figure 2 shows a vertical section through a dynamic occulator according to the invention; Figure 3 shows a horizontal section through the dynamic ul occulator shown in Figure 2; Figure 4 shows a vertical section through a flotation unit according to the invention, and Figure 5 shows a horizontal section through the flotation unit.

Figure 1 shows parts of a process for purifying liquids, such as drinking water, wastewater and inera. Liquid is first introduced through an inlet pipe 11 and a jet injector 41 to a dynamic occulator 10. The function and construction of the dynamic occulator 10 will be described below in connection with Figures 2 and 3. The liquid as shell is cleaned, the jet injector 41 is led in, where a turbulent flow is formed in the liquid at the outlet of the jet injector. Chemicals from a chemical reservoir 15 are led through a supply line 16 to the jet injector 41, while the chemicals are introduced into the liquid stream in the area where the turbulent liquid stream is formed, i.e. in the area of the jet injector 41 outlet. The chemicals are added to achieve flocculation of impurities in the liquid. The addition of chemicals by jet injection ensures that all chemicals come into contact with all particles to be localized within 0.5 - 1.0 second. For environmental reasons, the chemical reservoir 15 is located in a disaster basin 15A which has a larger volume than the reservoir 15.

After the liquid has been treated in the dynamic occulator 10 and special particles and colloids have been flocculated, the liquid is led via a pipe 12 to a flotation unit 13 for further treatment and purification. In connection with the totation unit 13, a polymer is supplied to the liquid which is delivered from a tank 18 for crude polymer and which is mixed ready with water in a mixing unit 19. Furthermore, dispersion water is added proportionally with incoming water stream directly below the flotation tank, so close to the inlet to the ilotation unit as possible. Here, the pressure in the dispersing water is released, which causes the release of a number of microscopic bubbles that will tend to surface up to the surface of the totation unit. On the way up to the surface, these bubbles will attach to the yokes that have already been built up and carried to the surface as sludge. The fraction of waste products lighter than the carrier liquid is scraped out at the upper end of the ationsotation unit 13 and passed through a sludge outlet 13A to a sludge reservoir 53. The fraction of the waste products heavier than the carrier liquid is removed through a pipe 17 at ned the lower end of the otation unit 13 to a sludge reservoir (not shown). The purified liquid is then led to a holding tank 14 which, among other things, serves to divert and return water back to the process through a pipeline 42, such as dispersion water. Figure 1 also shows the tank for dispersion water 43. In the dispersing water tank 43, the water is pressurized by means of a pressurized gas source 44, while water is supplied through the pipeline 42 and spread in droplet form into the pressurized tank 43. In order to have control over how much dispersing water is required for at any time in the tank 43 a scale 45 is used connected to the legs of the tank 43. Said scale 45 controls the amount of return water supplied to the tank 43.

The process according to the invention is controlled by a PLC unit 46 where characteristics of the liquid to be separated have been entered as a basis for introduction. Such characteristics may be tea temperature, variation in the amount of liquid and particle content or suspended substances in the liquid. This data is used as a basis for calculating the dynamic lockulator 10 with regard to the necessary residence time of the liquid in the ul occulator 10, volume and necessary G-values which in turn provide the necessary area and shape to be established on the paddle stirrer of the oculator 10 saint the required rotation span. 1 The PLC unit 46 is loaded with a pre-prepared setpoint curve V21. The input data to the PLC unit 46 is the incoming amount of water. The PLC unit 46 compares the measured amount of liquid received with said setpoint curve and on this basis the rotational speed of the paddle stirrers in the fl occulator 10, the volume of chemicals newly supplied from the chemical reservoir 15 and the amount of polyins to be supplied to the ul inoculated liquid are controlled. to the flotation unit 13. The PLC unit 46 also controls the amount of dispersion water supplied to the liquid stream for the flotation unit 13, as well as the rotational speed of the surface shimmer of the flotation unit 13.

Only those parts of the process which are relevant in connection with the dynamic occulator 10 and the flotation unit 13 are shown in Figure 1. It is obvious to a person skilled in the art that such a process also contains valves and pipes, etc., which are partly drawn on figure 1.

Figure 2 shows a vertical section through a dynamic occulator 10 according to the invention, while Figure 3 shows a horizontal section through the dynamic 10 shown in Figure 2. placed paddle 21 in the form of a vertical shaft 22 and a plurality of horizontal paddle blades 23A-G. In order to achieve an efficient and rapid mixing, the paddle 21 has here been given a special and advantageous shape, namely so that a number of pairs of paddle blades 23A, 23B ,. . ., 23G is at least three and typically up to six or seven pairs of paddle blades.

More specifically, it can be seen from Figure 2 that the length of the paddle blades decreases stepwise from the upper blade 23A to the lower paddle blade 23G which sits on the shaft 22. It is also seen, especially from Figure 3, that all the paddle blades lie in one and the same plane.

The paddle 21 is driven by an electric motor 24 located on top of the dynamic flock elevator. The liquid is supplied to the dynamic occulator 10 through a tube 26 (cf. 16 fig. 1) via a jet injector 41 at the upper part of the flocculator 10 and leaves the dynamic occulator through a tube 25 (cf. 12 fig. 1) arranged at the lower end of the occulator. .

These two tubes (inlet / outlet 25 and 26) are advantageously approximately tangentially oriented relative to the dynamic flocculator. The flocculator 10 is further equipped with a plurality of vertical baffles 47, arranged inside the accumulator 10.

Dimensioning of the dynamic flocculator is done by setting the dwell time to between 20 and 200 seconds. At Qdinï, the upper limit is set to 200 seconds. Since the particle separation here is based on flotation, an additional security has been added.

The G-value applied to the water will be a function of the rotational speed and can be calculated. To obtain correct energy data, the torque can be eaten in full scale. G-value input data can be changed by the rotational speed of the stirrer can be controlled steplessly with frequency converters and in addition both the stator and paddle / rotor configuration can be changed in the stirring device.

Figure 4 shows in principle and in vertical section the construction of an embodiment of an ationsotation unit 13 according to the invention with internal decantation. 10 15 20 25 30 530 549 10 On the inlet line 12 to the totation unit 13, a precipitation chemical (auxiliary coagulant) is dosed from a tank 18, with its own frequency-controlled dosing pump 19.

The coagulant can advantageously be a suitable polymer and it is important that the polymer dosing takes place evenly and quickly in order for the effect to be satisfactory. In this connection, it is an advantageous solution that the polymer supply pipe 40 opens into the inlet pipe 12 at a bend in it just before it enters vertically upwards through the bottom of the flotation vessel 13. Thus a form of jet injection ("jet injection") is achieved. jection ”) at this point. Dispersion water should be added as close to the inlet of the 13otation unit 13 as possible. Dosage amount for polymer is controlled according to the amount of water in to flotation. The amount of water is registered in a separate electromagnetic water intake grid mounted on the line to the flotation plant.

After the dosing point, dispersion water is added to the inlet water. This is controlled automatically with its own control valve and water meter on the pressure line from the dispersion plant (not shown).

The dispersion plant 43-45 pressurizes and air-saturates a proportion of the outlet water from the totation and returns this to the inlet. In the dispersion, the water is moistened with about 100 l of air per m3 of dispersion in a pressure cooker area between 4-6 bar. This is done by atomizing liquid over pressurized air in its own tank at the dispersion plant 43-45.

When the dispersion through a tube 40 is added to the inlet line 12, the pressure is released and microscopic air bubbles are released. These are mixed with flocculated sludge, with the result that particle aggregates with extreme buoyancy are led into the flotation unit 13.

The passage of the process water through the totation unit 13 can be divided into 5 zones, as schematically illustrated in figure 4.

Zone 1: Inlet zone. The wastewater is automatically led into the bottom of the unit 13 where polymer and dispersion water 40 are added just before the inlet. The amount of water 10 15 20 25 30 530 E43 ll it is continuously registered by the electromagnetic water meter for the occultator 10.

Zone 2: Distribution zone. Wastewater, polymer and dispersion water are mixed well and distributed hydraulically evenly circularly in the totation unit 13 immediately after the inlet 12. The distribution plate 48 ensures that finished fl inoculated liquid is distributed centrally evenly over the entire flotation area and that excess sludge does not settle as sediment in the inlet 12.

Zone 3: Acceleration zone. The wastewater is led upwards where the surface is reduced between the outer wall of the flotation unit 13 and the inner conical wall portion of the container 30.

The velocity of water and particles increases considerably.

Zone 4: Separation zone. The water spray enters the separation zone where the surface area is maximized and the speed is reduced rapidly. Particles etc. have a given velocity vertical to the surface and are to be separated from the liquid phase. Floated sludge is scraped off the surface and into a sludge 53 cka 53. The purified water flows calmly l80 ° down into the inner container 30.

Zone 5 Outlet zones. The water is led from the inner container up into the container pipe 36 and then it is turned 180 ° down into the funnel / outlet pipe 37 (with level control) and out 38 through a jacket wall on the unit 13. In the center of this the purified water can be visually checked. Water is taken from the outlet pipe 38 to the dispersion plant and to the dilution water pump 19 for polymer. Purified water is of course passed on to the recipient.

In the light of the prior art, those skilled in the art will realize that the purification process through five zones as mentioned above involves several new and distinctive features which are also connected to the different levels of pipe and wall edges where the water spray is turned mainly 180 °, as illustrated with the arrows in Figure 4.

Claims (6)

10 15 20 25 30 530 'B49 ll PATENT REQUIREMENTS A method for cleaning liquids, such as drinking water, wastewater, sewage, industrial process water and the like, wherein particles which are both heavier and lighter than the carrier liquid are separated from the liquid and led to suitable reservoirs, the liquid to be cleaned in advance additives and / or liquids are preferably added by a jet injector (41) which creates turbulence in the liquid stream to improve the precipitation effect arranged upstream of a flocculator (10), after which the liquid is preferably led into the flocculator (10) where at least substantial parts of the particles is heavier than the carrier liquid is removed from the liquid and discharged to a suitable collection landfill, while the particles which are lighter than the carrier liquid are allowed to flocculate after which the partially purified liquid is passed on to a flotation unit (13) where at least substantial portions of the particles is lighter than the carrier liquid is excreted and led away to a suitable u landfill, which flotation unit (13) is provided with an open funnel-shaped container (30) 180 ° in the inner direction, upwards which faces the vertical flow direction of the liquid stream downwards, characterized in that the liquid stream in the (funnel-shaped) container 180 ° in an upward direction into a downwardly open tubular casing (36), and then again 180 ° in a downward direction through an upwardly open funnel-like unit (37) disposed within the downwardly open tubular casing (36) and out of the flotation unit. Method according to claim 1, characterized in that the liquid is led to the lower part of the otation unit where the upwardly directed vertical into the liquid stream is led towards a distribution plate (48) which turns the liquid stream 90 ° so that the liquid is distributed over the entire cross section in a distribution zone (zone 2), whereby particles converge and form larger flocks and where any heavier particles settle, so as to flow upwards to an acceleration zone (zone 3) where the velocity of the liquid increases, after which the liquid is led 180 ° downwards to a separation zone (zone 4 ) in the inner funnel-shaped container (30) where the surface area of the flotation unit is maximized and the liquid velocity is reduced, so that flotated sludge floats to the surface and is removed by scraping. Flotation unit for flotation of liquids, such as drinking water, wastewater, sewage, process water from industry and the like, where particles which are both heavier and lighter than the carrier liquid are separated from and where an inlet pipe (12) for the liquid is arranged at the totation unit (13 ) lower end and wherein the flotation unit comprises an internal funnel-shaped container (30) which is open and has a surface area substantially corresponding to the surface area of the totation unit (13) at its upper end and which at its lower end is closed and has a substantially smaller surface area provided with a downward open tubular casing (32) having a substantially smaller opening area than the cross-sectional area of the upper duct, and where the flotation unit is provided with a scraper at its upper end, to allow removal of fltate at the end. characterized in that in the inner funnel-shaped container (30) a downwardly open tubular casing (36) is arranged which at its lower end is in liquid communication with the inner funnel-shaped container (30), in which downwardly open tubular casing (36) is arranged a funnel-like unit (37) having an upper opening surface which is slightly smaller than the surface area of the open pipe casing (36), and that the funnel-like unit (37) at its lower end is closed to the downwardly open pipe casing (36), but is fitted with an outlet pipe (38) for draining purified liquid out of the ationsotation unit. upper flotation unit Flotation unit according to claim 3, characterized in that the inlet pipe (12) is directed upwards and preferably centrally at the bottom of the flotation unit (13), and is configured to direct the liquid stream towards a distribution plate (48) which distributes the liquid over the entire cross section of the flotation surface. Flotation unit according to claim 4, characterized in that an inlet line for arranging polymers and / or dispersion water is arranged in connection with the inlet pipe (12) before the inlet in the flotation unit (13). 5312! B49 l '~ l Float unit according to one of Claims 3 to 5, characterized in that the funnel-like unit (37) with the enclosing downwardly open pipe casing (36) is preferably located centrally in the inner container (30), with the lower edge of the pipe casing arranged downwards. in the inner container and with the tube housing extending higher than the upper edge of the inner container, while the funnel-like unit (37) has its upper edge in the form of an overflow at a level higher than the upper edge of the inner funnel-shaped container (30). ).