Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F7/00—Aeration of stretches of water
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/234—Surface aerating
  • B01F23/2342—Surface aerating with stirrers near to the liquid surface, e.g. partially immersed, for spraying the liquid in the gas or for sucking gas into the liquid, e.g. using stirrers rotating around a horizontal axis or using centrifugal force
  • B01F23/23421—Surface aerating with stirrers near to the liquid surface, e.g. partially immersed, for spraying the liquid in the gas or for sucking gas into the liquid, e.g. using stirrers rotating around a horizontal axis or using centrifugal force the stirrers rotating about a vertical axis
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F25/20—Jet mixers, i.e. mixers using high-speed fluid streams
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

• the present invention relates to a method for increasing oxygen content of hypolimnion and for removing harmful gases in hypolimnion, in which method hypolimnetic water is pumped through a riser tube reaching from hypolimnion up near the surface to an upper basin on the water surface, where the hypolimnetic water is aerated and harmful gases are removed, and from which upper basin the oxygenated water is conducted through a downcomer back to the hypolimnion.
• the present invention also relates to a device for increasing the oxygen content of the hypolimnion and for removing harmful gases in the hypolimnion, which device comprises an upper basin, a riser tube reaching from the hypolimnion up near the water surface, a pumping device for pumping the hypolimnetic water in a riser tube and a downcomer conducted back from the upper basin to the hypolimnion for conducting the oxygenated hypolimnetic water back to the hypolimnion.
• Discharging compressed air to the lower part of the hypolimnion, to the depth of 10 m for example, means 1 bar overpressure, which demands a lot of energy.
• overpressure facilitates solubility of gases, the solution of oxygen into water from air bubbles rising freely is slow, because air bubbles are not broken (to have a good transferring efficiency continuous "disturbing" of the bubble-water interface is needed).
• the specific transferring capability ranges 0,4 - 0,8 kg 0 2 /kWh depending on the size of orifices of diffusers and the depth of use, which, as being somewhat poor, causes big sizes of devices and applying costs.
• the object of the invention is to provide a method, by employing of which the techno-economical disadvantages and problems included in the earlier mentioned original methods may remarkable be decreased.
• the object of the invention is to provide a method, by employing of which increasing of the oxygen content of the hypolimnion of lakes and removing of harmful gases are managed to realize reliably, simply and economically by operating and purchasing costs.
• the object of the invention is to provide a device in accordance with the method, which is well suitable for lake conditions, small in size, efficient and economical by costs.
• Characteristic to the method in accordance with the invention is the fact, that hypolimnetic water is conducted through a riser tube to an accelerating device, where the flow velocity of the hypolimnetic water is increased and that the hypolimnetic water is conducted through a riser tube to a basic guide located at least partly over the surface of the water, by means of which the hypolimnetic water is directed to a distance above the water level and back towards the water surface at suitable speed and at a suitable angle of attack.
• the kinetic energy bound in the total flow velocity of pumped hypolimnetic water may be directed in such shape and roughness of the surface which maintains the motion energy as well as possible towards the upper basin and collided against the surface of water such, that while the motion energy is absorbed the transfer of oxygen to water and the transfer of harmful gases from water to the air is realized more effective per removed amount of water than in today known fall aeration.
• problems caused by wind and rocking conditions (waves) typical to fall aeration are avoided, because the falling height is essentially lower than in fall aeration. Therefore, by employing this kind of a method increasing of oxygen content of hypolimnion and removing of harmful gases succeeds reliably, simply as well as with less costs than earlier.
• the total flow rate of hypolimnetic water is divided in the basic guide with jet guides into partial jets suitable in size by their flow velocity, and it is roughened with surface roughening guides. It has been stated in many researches that the dividing of the total flow rate into small partial jets improves the oxygenation result. Therefore, by dividing the total flow rate in this way as efficiently as possible into partial jets, exact by their shape and surface roughness and efficiently collecting oxygen to the hypolimnetic water, it is possible to improve the oxygenation result attained by the method.
• hypolimnetic water is pumped through the riser tube to the basic guide so, that the collision velocity of the hypolimnetic water to the water surface gains app. 3,5 - 5 m/s. It has been stated in researches that with this kind of velocity it is possible to gain the best possible exchange of gases, that is oxygenation of the hypolimnetic water and removing of harmful gases.
• the hypolimnetic water is guided with a basic guide such, that the angle of attack of water against the water surface is at 60 - 90° angle at the moment of collision.
• the hypolimnetic water is pumped with a propeller pump located in a riser tube.
• a propeller pump is a highly profitable pumping device and the efficiency of a propeller pump is good.
• a propeller pump is well applicable to device applications of the method, because it is symmetric in revolution, and therefore suitable for mounting inside a tube-like or square frame. Due to this, a device based on a propeller pump is possible to create as small, well- balanced and simple by construction.
• the flow velocity is increased with a narrowing part located inside the rise tube.
• the flow velocity of the hypolimnetic water conducted to a basic guide may be increased in order to create suitable collision velocity simply and advantageously.
• the nan-owing part is possible to shape to join the basic guide as evenly as possible such, that the flow velocity accelerates evenly and without loss as far as possible.
• the flow velocity of the hypolimnetic water is decreased with a enlargening part located after the pumping device and increased with jet nozzles accelerating the flow velocity located in the basic guide.
• a enlargening part located after the pumping device and increased with jet nozzles accelerating the flow velocity located in the basic guide.
• Characteristic to the device in accordance with the invention is the fact that the device comprises a basic guide reaching through a riser tube at least partly above the water surface for guiding the hypolimnetic water coming through a riser tube a distance above the water surface and back towards the water surface at suitable speed and at a suitable angle.
• This kind of device is possible to construct compact by construction and size, notably lower by parts located above the water surface than in cases of traditional fall aeration heights, capable for distributing the total flow rate into numerous partial jets improving efficiency and about 2 - 3 times more effective than bubble aeration by specific transferring capability.
• this kind of device is nearly free from breaking influence of wind of water jets, enduring motions of waves and rocking as well as moving under ice while being pushed by an ice float. Therefore, it is decisively techno-economically more advantageous than presently known devices used for increasing oxygen content of the hypolimnion.
• Figure 1 illustrates a principle drawing of a device in accordance with the invention
• Figure 2 illustrates a basic guide included in the device in accordance with figure 1 viewed from side
• Figure 3 illustrates a basic guide included in the device in accordance with figure 1 viewed from above
• Figure 4 illustrates a principle drawing of another device in accordance with the invention.
• the device in accordance with figures 1-3 comprises an upper basin located on the water surface, a riser tube 2 conducted from near the water surface to the hypolimnion 1, a propeller pump 3 mounted inside the riser tube by means of a motor housing acting as the basic float 13, a basic guide 5 and a jet guide 6 and a surface roughening guide 7 located in the basic guide as well as a downcomer 11 conducted from the upper basin 9 to the hypolimnion 1.
• the application in accordance with figures 1-3 comprises, among other things, a flow guide 12, attached to the riser tube 2 under the downcomer, with which flow guide, in case of low hypolimnion, the access of removed water back to the riser tube is prevented, wires 18 and a bottom weight 19, with which the device has been anchored slightly to float freely along with rising and lowening of the surface.
• the device comprises, among other things, devices for current supply and controlling of the pumping device.
• the upper basin 9 is an object, cylindrical in the upper part, the edge construction
• the wall of the upper basin are made of suitable plate like material, which is preferably of material well isolating heat, such as some suitable plastic.
• the edge construction 14 of the upper part of the upper basin is made, in this case, of two layer plastic tube with air between the layers, which is a good heat isolation and which, in wintertime, prevents the heat of warm water (2-4 degrees) from transferring through the wall of the tube outside the basin.
• the depth of the upper basin 9 needs to equal at least the depth where air bubbles reach while diving.
• the depth of the upper basin is about 0,5 - 1 m.
• the diameter of the upper basin corresponds to the horizontal area, what is needed for bubbles to rise on the surface of water.
• the diameter of the upper basin is, in this case, about 2 m.
• the riser tube 2 is a round by cross-section plastic tube with a curved narrowing part 4 in the upper part.
• the length of the riser tube has been chosen such that the tube reaches from the surface of water to the lower part of the hypolimnion just a suitable distance from the bottom of the lake.
• the magnitude of the narrowing of the narrowing part 4 has been defined such that with a defined flow velocity of the hypolimnetic water suitable collision velocity of the hypolimnetic water against the water surface in the upper basin may be attained.
• the downcomer 11 is a plastic tube like the riser tube reaching from the lower part of the upper basin to the upper part of the hypolimnion.
• the downcomer is bigger by diameter than the riser tube placed inside the downcomer such, that there is a space between the inner part of the downcomer and outer part of the riser rube where oxygenated water may flow downwards to the upper part of the hypolimnetic stratum.
• a flow guide 12 At a suitable distance from the lower part of the downcomer there is a flow guide 12, the purpose of which is to secure that oxygenated water coming from the downcomer spreads as evenly as possible to the surrounding hypolimnion and does not flow back to the downcomer even in case of low hypolimnion.
• the flow guide 12 is, in this case, a flange type object attached round the riser tube.
• the pumping device 3 is a low speed (about 150 - 400 rpm) submerged propeller pump, which is driven by an electric motor with reduction gear.
• the motor and gear of the pump have been encased such, that the case of the pump forms a high basic float 13 inside the downcomer 2.
• the basic float 13 has been attached with a wire
• the regulation of the height of the basic guide is partly carried out by changing the size of the basic float 13 but mainly the regulation is carried out by regulating the height and the floating ability of the edge construction 14 of the jet basin functioning as an additional float and by regulating the carrying wires 15.
• the basic guide 5 is a round surface (torus) curved to the direction of the edges of the upper basin, on the lower surface of which the hypolimnetic water coming through the riser tube stays due to the centrifugal force.
• On the inner surface of the basic guide there are several jet guides 6 illustrated in figures 2 and 3, by means of which the hypolimnetic water flow, otherwise shaping round and lowening, is narrowed such, that flow velocity and motion energy hold as well as possible and that the total flow is divided into desired series of partial jets.
• the basic guide 5 comprises also surface roughening guides 7 located after jet guides 6, with which partial jets are roughened in order to increase the forming of air bubbles.
• a metal basic guide 5 has been attached to the upper part of the basic float 13 such that the heat of the motor of the pumping device is transferred to those parts of the basic guide, which are in danger of gathering ice coat in wintertime.
• the device has been anchored slightly with two stay wires 18 and a bottom weight 19 to float freely along with rising and lowening of the surface.
• the floating characteristics of the device are defined to be rather heavy, in order to avoid damages due to moving of ice.
• Stay wires are mounted to rise rather steeply, for example at 60 - 70 degree angle in respect of the horizontal plane. In this case, while an ice float pushes the device sideways, a component of force drawing the device downwards is created such that the device easily finds its way below the ice.
• directing plates are mounted above the propeller which function in a corresponding way as the directing parts of a turbine.
• additional weights are mounted while needed to stay wires in order to create counter moment preventing circling.
• hypolimnetic water 1 with a low oxygen rate is pumped through a riser tube 2 with a propeller pump 3 into the narrowing part 4 of the riser tube, where the water velocity accelerates to 3,5 - 4,5 m/s and further from there to a basic guide 5.
• a suitable hypolimnetic water flow velocity in the basic guide is achieved, which is about 1-4 liters per second.
• the basic guide 5 about 0,1 - 0,3 m above the water surface vertical flow is turned radial, in this case, with a round basic guide back against the surface of the upper basin such that the motion energy and the motion rate hold as well as possible, which is best realized when the flow velocity is kept constant.
• Jet guides 6 and surface roughening guides 7 divide the total water flow rate into several partial jets 8 suitable rough by their surface, which collide at a great angle of attack against the surface of the basin 9.
• Water jets with lots of kinetic energy created in this way take plenty of air bubbles 10 with them, from which oxygen dissolves in injected water and to water near the jet due to strong turbulence.
• possible harmful gases in injected water are removed into atmosphere.
• Dived air bubbles discharge from the surface of water basin into the air and water which has no bubbles but is oxygenated flows under small hydrostatic pressure to the downcomer 11 and the hypolimnetic water returns to the upper part of the hypolimnetic stratum, from where it slowly flows deeper to the depth corresponding to its density.
• the method and the device in accordance with the invention are not limited to the presented application in figures 1-3 but it may be realized in many parts differing from that.
• Various parts of the device may be built differently while needed.
• the depth and the diameter of the upper basin depend on the velocity of the water colliding against the water in the upper basin as well as the thickness of used jets and the diameter depends on the area needed for upcoming bubbles which area depends on earlier mentioned factors.
• the length and the diameter of the riser tube may be varied.
• the cross-section is preferably round but also other shapes are possible.
• the cross-sectional area of the riser tube may also vary.
• the cross- sectional area depends on the needed volume flow rate. Increasing the volume flow rate results in increase in flow velocity in which case also flow resistances increase. Therefore, the flow velocity is kept low before the pumping device, typically about 0,5 - 1,5 m/s.
• the inner surface of the riser tube is as smooth as possible.
• a basic guide attached to a high basic float in accordance with figures 1-3 as well as jet guides and surface roughening guides attached to the basic guide may be varied in order to optimize the oxygenation rate and, on the other hand, to emphasize aesthetic values in many ways.
• a basic guide may be a series of curved pipes, of round or square shape, the total cross-sectional area of which equals the cross- sectional area of the acceleration point of the riser tube. There are no jet guides but suitable surface roughening guides are employed at the end of the tube.
• the basic guide is a series of curved flumes, opening downwards and square by cross-section, into which the rising water is directed and where water is kept by created centrifugal force.
• the basic guide is a plane attached to the basic float, the edges of which plane are curved torus-like downwards for example about 80 degrees.
• the riser tube is, in this case, bigger and the flow velocity correspondingly smaller.
• the riser tube there is only a torus edge rounded outwards, at the point of the outer edge of which the edge of the basic guide starts to turn downwards.
• the difference in height of the torus edge of the riser tube and the basic guide is regulated to be such small that the flow velocity of water, taking into account the accelerating effect of jet guides mounted between them, amounts only at the arc curving downwards the desired 3,5 - 4,5 m/s.
• Suitable surface roughening guides are attached to jet guides and/or basic guides, which surface roughening guides may be, for example, in accordance with the application in figures 1-3.
• the basic guide is a vessel supported above the water surface to the basic float, into which vessel the hypolimnetic water is conducted through a riser tube and in which there are orifices at suitable points, which orifices form jet guides.
• Surface rougheners for water may be formed into orifices, for example, by shaping the edges of the orifices.
• FIG 4 An application in accordance with the invention has been illustrated in figure 4.
• the basic guide 24 has been formed of a plate-like vessel, into which the hypolimnetic water 20 is pumped with a propeller pump 22 in accordance with the application in figures 1-3 through a riser tube 21.
• This application does no comprise a narrowing part after the riser tube 21 and the pumping device 22 but, on the contrary, unlike in the application in figures 1-3 in this application the flow velocity of the hypolimnetic water is slowed down with a enlargening part 23 placed at the point of the narrowing part and the increasing of the flow velocity is not realized until in the jet nozzles 25 of the basic guide 24 (there are 57 jet nozzles in this application), which inject the hypolimnetic water pumped to the basic guide to the upper basin 27. In this way losses occurring due to flow resistances on the area of riser tube and the basic guide are tried to be minimized.
• the application in accordance with figure 4 comprises also a mixing flow tube 26.
• Water flow from the end of the mixing flow tube 26 causes turbulence near the bottom, which mixes and rises the heaviest hypolimnetic water near the bottom to the strata near the riser tube and to the suction flow of the riser tube. Therefore, due to the mixing flow tube 26 also the hypolimnetic water near the bottom and often with the poorest oxygen content appears in the riser tube 21.
• a mixer of the hypolimnetic water near the bottom functioning as does a mixing flow tube 26 may be realized by employing a propeller mixer, which is run by a turbine propeller placed in the riser tube, or with a suction flow guide, which causes suitable mixing turbulence in the hypolimnion.
• the device may be realized in a different way.
• some other types of pumps than a propeller pump run by an electric motor may be used.
• Many high productive pump types are possible.
• thinking about easy-to move and temporary use of a pump the power to the pump may be taken, for example, from a combustion engine placed above the whole device.
• the height of the device may, in some applications, be increased by shaping and lengthening the basic guide.
• flow resistances increase a bit, which needs to be taken into account in the power of the pumping device.
• Tubes and flumes may be made of transparent material and they may be shaped compromising over hydraulics. In case using open flumes the height and the rising speed are taken into account such, that the speed is enough for making the water stay in the flume.
• a basic guide may be formed of solid tubes, the cross-section of which is round or square.
• the rising height may be remarkable big, depending on a pump even 2 - 4 m, but in case the lower end of a tube is brought optimizing also the aeration purpose siphon-like to the normal 0,1 - 0,3 m discharge height, the needed pumping energy does not significantly increase. In these cases, also spot lighting may be used.
• the device may also be built to be high and sprinkling impressively water at desired times of the day, but optimized to aeration purpose at the other times of the day. Changes according to the function may be carried out remote-controlled or automatically.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Organic Chemistry (AREA)
• Aeration Devices For Treatment Of Activated Polluted Sludge (AREA)

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• 2003
  • 2003-01-23 FI FI20030105A patent/FI20030105A0/fi unknown
• 2004
  • 2004-01-22 EP EP20040704248 patent/EP1594808A1/en not_active Withdrawn
  • 2004-01-22 WO PCT/FI2004/000033 patent/WO2004065312A1/en not_active Application Discontinuation

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