FI59081C - SAFETY ACTION FOR SYREBERIKNING AV VATTNET I SJOEAR OCH LIKNANDE - Google Patents

Description

Γ7 ^ Γ · | fal (m NOTICE C Q Λ Q Ί JBTa lBJ (11) UTLÄCGNINGSSKRIFT 5 9081 • C / 4 »Patents granted 10 C6 1901

Patent meddelat (51) KY.ik? /Mt.a.3 C 02 P 7/00 // B 01 F 3/04 FINLAND —FINLAND (21) P * t «nulhak.mu.-P» t «nt« niöfcnint 1515/72 (22) HukumUpBIvi - AiMflknlngtdag 30.05-72 ^ ^ (23) Alkupllvt — Giki (h «t * dt | 30.05.72 (41) Tulkit JulklMktl - Bllvlt offmtllg 02.12.72

Patent and Registration Office .... , - - . . ___, (44) N «htl» «racing» is »moonL | foreign * date 0 0 no

Patent- och registerstyrelsan Anukin utligd och utl.tknftun pubiko 27-02.81 (32) (33) (31) Requested «oolkuM-Buglnl prior * · * 01.0έ. 71 28.01.72 Sweden-Sweden (SE) 7002/71, 972/72 (71) Atlas Copco Aktiebolag, Nacka, Sweden-Sweden (SE) (72) Bo Lennart Verner, Stockholm, Lars Börje Staffan Fors,

The present invention relates to a method and an apparatus for restoring lakes by oxidizing their water. The present invention relates to a method and an apparatus for restoring water in lakes and the like. . More specifically, the object of the invention is to solve the problem of air treatment of lake water in lakes with a depth exceeding 8-10 m without disturbing the thermal stratification of the water.

During the summer, water in such lakes is deposited in two layers, the upper warmer layer, the epilimnion, and the lower colder layer, the hypolimnion. The boundary layer between the epilimnion and hypolimnion layers is located at a depth of 8–10 m. The surface layer has good contact with the climate and can therefore receive some oxygen. In this upper layer, planktonic algae evolve organic matter, producing oxygen as a by-product. If the nutritional salt content in the epilimnium is high for natural or man-made reasons, high organic matter evolution will result. Much of this sinks into cold hypolimnia, where bacteria break it down into organic components. However, this process is only possible if there is oxygen in the hypolimnion water.

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If the oxygen content is too low for this organic decomposition to occur, nutrient salts will diffuse into the water, from the bottom sediment of the lake during the summer stop phase. During the next spring cycle, these nutrient salts become distributed throughout the water mass and thus become available for advanced organic production. This constant increase in organic matter production progressively worsens the oxygen balance, and the lake has no chance of interrupting this development without outside help.

One method to help the lake from this situation is to conduct oxygen into the water. Oxygen must be directed to the lower, oxygen-consuming and oxygen-poor layer, the hypolimnion. In this case, it is important that the hypolimnion water does not mix with the oxygen-rich surface water, as this would lead to a complete oxygen deficiency in the lake. With such a method and device (Finnish patent 56 93 ^), groundwater is taken on top of floating units, which units comprise air and water pumps, after which the water-air mixture is introduced into the hypolimnion. The disadvantages of the method and the device are the loss of power due to the re-pumping of significant amounts of water and the risk of the equipment getting stuck in the winter. The pin-flatness of the entire hardware and the fact that the hardware extends toward the bottom of the piping complicates the anchoring and transfer of the hardware.

According to the second method previously proposed for the oxidation of the lake, hypolimnion water is conveyed to the surface by means of a mammoth pump and, after being in contact with the air and absorbing oxygen, is returned to its former depth.

The disadvantage of this known method is that it requires very bulky and difficult-to-handle equipment. For example, the mammoth pump must be at least 10 m high to extend through the epilimnium layer.

Another disadvantage of this method is that water is introduced into the air at normal atmospheric pressure, which means a relatively low solubility of oxygen.

According to the present invention, these problems are solved by air treatment of water at low, in the hypolimnion itself, which means that oxygen is introduced into the water at the pressure prevailing in the hypolimnion. If, for example, oxygen is introduced into water at a depth of 20 m, the oxygen solubility in water is about 3 times higher than on the surface. The method according to the invention also entails the possibility of using equipment which are much smaller than the previously mentioned mammoth pump.

The invention therefore relates to a process for the oxidation of water in lakes and the like which are deep enough to divide the water during the summer season into essentially two thermal layers, an upper, warmer layer (epilimnion), and a lower, colder layer (hypolimnion), whereby oxygen-containing by conducting a mixture of gas and water, a gas cushion is maintained in the bellows chamber in the hypolimnion, in which the water-insoluble gas separates from the water stream and is vented from the chamber to the atmosphere without disturbing the thermal deposition of the environment; the formation is effected by introducing a gas, preferably air, directly into the hypolimnion, maintaining in a manner known per se a continuous mammoth pump effect towards the gas cushion in the chamber.

The invention also relates to an apparatus for applying a method of oxidizing water in lakes or the like deep enough to divide water substantially during the summer season into two thermal layers, an upper, warmer layer (epilimnion), and a lower, colder layer (hypolimnion), whereby oxygen-containing gas and by conducting a mixture of water, a gas cushion is maintained in the bellows chamber in the hypolimnion, in which the water-insoluble gas separates from the water stream and is discharged from the chamber to the atmosphere without disturbing the thermal deposition of the environment; and a gas nozzle disposed in the hypolimnion at the lower end of the channel for introducing oxygen-containing gas into the water, the channel and the gas nozzle forming a mammoth pump acting towards the gas cushion and maintaining a water flow; ä to form a water-air mixture.

However, in connection with flotation (SE publication 360 026) and wastewater treatment (DOS 1 800 315), oxidation of water with air bubbles has been proposed in the past. However, when treating lakes that are thermally deposited, these methods and equipment would result in complete mixing of the entire body of water, which would accelerate the generation of organic matter in the body with even higher oxidation needs and stabilize the water temperature so as to eliminate ecologically needed cold water stocks. consequences for fisheries.

The method and apparatus according to the invention are explained in detail below with reference to the drawings.

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Figure 1 shows the thermal deposition of water in a deep lake during the summer shutdown phase. The temperature in the upper layer (epiiimnion) varies from about 20 ° on the surface to about 4 ° at a depth of 0 m, while in the lower layer (hypolimnion) the temperature is constant 10 m from the level down. Figure 2 schematically shows a water treatment method according to the invention. Figure 3 shows a vertical section of a water air treatment device according to the invention. Fig. 4 shows a horizontal section along the line IV-IV in Fig. 3- The vertical section according to Fig. 3 runs along the line III-III in Fig. 4.

According to the method shown in Figure 2, air is introduced into the hypo-limni via line 10. This line terminates in the lower end of a vertically arranged tube 11 which is open at both ends. The air flowing into the water due to the pipe 10 rises bubbly through the pipe 11 and thus forms a mammoth pump. The upper end of the tube 11 is located in a dome-like chamber 12 for the purpose of collecting rising air bubbles. An air bag 13 is then formed in the upper part of the chamber 12, the size of which is monitored by a throttle valve 14 which senses the pressure. The water oxidizes when it comes into contact partly with the rising bubbles in the tube 11, partly into the air space 13 in the chamber 12.

This new method thus means that the water flows into the pipe 11, rises upwards with the air bubbles, passes through the air space 13 and finally leaves the housing. It is essential for the method that the air bubbles are prevented from leaving the housing together with the outflowing water, because the free-rising air bubbles cause an undesired flow in the water, which in turn would interfere with the thermal deposition.

Referring to Figures 3 and 4, an apparatus for water oxidation according to the invention will be described below. The device comprises a housing 21 with an upper part 22, an intermediate part 23 and a lower part 24. The housing 21 is cylindrical, the upper part 22 and the intermediate part 23 having the shape of cones or truncated cones. The lower part 24 is further provided with a base 26 in which a central circular hole is made, through which a tube 27 directed axially into the housing extends. The lower end of the tube 27 protrudes the distance of the body under the housing base 26 and its upper end is at the height of the intermediate part 23 of the housing 21.

A ring-shaped air nozzle 28 (see Fig. 4) is arranged at the lower end of the tube 27 and is connected to a compressed air source (not shown) via a hose 29.

The tubes 27 are attached to three symmetrically fitted brackets 30a-c in the lower part 24 of the housing 21 and are supported by three similarly symmetrically fitted guides 31a-c on the inside of the housing 21.

The attachment of the tube 27 to the brackets 30a-c allows a certain axial displacement of the tube 27 with respect to the housing 21. This is achieved in that the elongate fastening irons 32a-c are fastened to the tube 27 and provided with a plurality of holes through which the tube 27 can be fastened with a screw connection to the brackets 30a-c. This fit makes it possible to vary the annular gap. between 5,59081 between the upper edge of the tube 27 and the conical inner wall of the housing 21. Thus, the speed of the downward water flow in the housing can be adjusted e.g. the amount of air introduced and the rate of rise of air bubbles in the water so that at least most of the air remains in the housing.

The upper part 22 of the housing 21 has the shape of an air collecting dome and is provided with an air outlet 33 which communicates with the outside air via a line 34 and an adjustable throttle valve 35.

Exhaust ducts 39a-c provided with air collection chambers 36a-c are connected to the outlet openings 25a-c of the lower part 24 of the housing 21.

Each of these consists of a tubular compartment provided with a dome-like extension on its upper side. These air collection chambers 36a-c communicate with the outside air via lines 37a-c provided with flow control valves 38a-c. The outlet lines 39a-c may consist of thin-walled plastic pipes, which are advantageous in that they are cheap, light and easy to handle.

The device according to the invention also comprises stabilizing devices partly float-like 40 and 41 connected to the upper part 22 of the housing 21 and partly radially oriented arms 42a-c, with their housings 21 connected by ropes 43a-c to an anchor cluster 44 resting at the bottom of the lake.

The device shown in Figures 3 and 4 further comprises a safety device in the form of valve doors 45 in the upper part 22 of the housing 21.

These are connected by a rope 4G to a weight 47 resting on the bottom of the lake.

The device according to the invention is more suitably controlled from a boat, barge, raft or the like to which the exhaust valves and the compressed air source are arranged. The control platform should also support a winch that can be used to raise and lower the instrument. Since the control platform is not part of the invention, it is not shown in the drawings or explained in detail.

The instrument described above works as follows:

To oxidize water in a deep lake, the instrument is lowered to the lower temperature layer of the water, the hypolimnium, to a depth of more than 8-10 m. The floats 40 and 41 are dimensioned to support most of the weight of the device except for the anchoring clump 44 and the weight 47 which causes them to hold the device in an upright position. The length of the ropes 43a-c and 46 is then adjusted so that the lower end of the pipe 27 is 2-3 m above the bottom. This distance should not be exceeded, otherwise there is a risk of the bottom mud being sucked into the instrument.

The device begins to operate when compressed air is supplied to the nozzle 28 through a hose 29 from a source of compressed air. The air leaving the nozzle 28 rises as bubbles in the tube 27 and then entrains the surrounding water. In this way, a mammoth pump is generated which sucks water from the lower end of the pipe 27 and delivers it at a certain upward speed to the housing 21 at the upper end of the pipe.

Once the air bubbles have left the tube 27, they continue upwards and accumulate as an air bag at the top 22 of the housing 21. The back pressure from the air bag forces water to turn and flow down the housing 21 on the outside of the tube 27 and further out of the outlets 25a-c. The water then passes through air collection chambers 36a-c, where any remaining air bubbles may rise and accumulate in dome-like expansions. The water is then led to different parts of the lake by drain pipes 39a-c. The water has been in contact with the air as it has passed through the instrument, receiving oxygen.

The oxygen-poor air accumulated in the upper part 22 of the housing 21 is continuously led to the free air through the deaeration 33 and the line 34. In order for line 34 not to act as a mammoth pump either, the flow through it must be restricted. This is achieved by a throttle valve 35 · This is set so that the amount of air in the housing becomes as small as possible and remains essentially constant. This is essential because if the back pressure in line 34 were too low, air would be drawn in with the water and thermal deposition in the lake would be compromised. If the resistance from the other side would be too high, increase the volume of air contained in a housing 21 or could become so large that part of the water cycle would stop and the part without a lifting force would increase the size of the surface of the unit.

As a precaution to prevent the latter, the valve doors 45 in the upper part 22 of the housing 21 are arranged to open as soon as the entire weight of the weight 47 acts on the rope 46. When the doors 45 open, such a large amount of air escapes quickly from the housing.

In the air collection chambers 36a-c, secondary collection of air bubbles takes place, i.e. separation of any air remaining in the water as it passes through the housing 21. Since the rate of rise of small bubbles in water is lower than that of large air bubbles, a very low flow rate through the housing 21 would be required for all bubbles to separate. Such a low flow rate would reduce the working speed of the instrument. This is avoided by arranging secondary deaeration. However, the flow rate through the housing 21 is chosen so that only very small air bubbles are drawn down 7 59081. The air thus collected in the air collection chambers 36a-c is gradually released into the outside air through the deaeration lines 37a-c and the valves 33a-c.

In the embodiment of the invention described above, throttle valves are used to adjust the volumes of air volumes in the housing 21 and in the air collection chambers 36a-c, which valves are intended to be adjusted manually so that the desired air volumes are obtained. These valve functions can, of course, be automated, e.g. by allowing the valves in the exhaust air lines to be affected by the grooves which know the height of the water in the housing 21 or chambers 36a-c.

According to a simplified embodiment of the invention, the device can be shaped without air collection chambers in the exhaust lines. Instead, the water flow rate has been reduced by enlarging the annular gap between the vertical tube and the inner wall of the housing, so that even small air bubbles are not in danger of being drawn with the water flow.

The adjustment of the air volume of the housing 21 can also be automated in such a way that the valve, which is familiar with the weight of the whole device and the weight of the device in the water, acts on the valve in the deaeration line 3 ^. This valve must then be controlled so as to increase the air flow in the line 3 * »when the weight-to-lift ratio falls below a certain value and decreases the air flow when said ratio exceeds another, higher value.

The invention is not limited to the embodiments described above but can be freely modified within the scope of the claims.

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Claims (6)

59081 1. A method of oxidizing water in lakes and the like which is deep enough to divide water substantially during the summer season into two thermal layers, an upper, warmer layer (epilimnion) and a lower, colder layer (hypolimnion), maintaining a mixture of oxygen-containing gas and water in a clock chamber (12, 21) a gas cushion in which a water-insoluble gas separates from the water stream and is led from the chamber to the atmosphere without disturbing the thermal deposition of the environment, while the oxygen-enriched water stream is led from the chamber to the hypolimnion gas, preferably air, directly into the hypolimnion, maintaining in a manner known per se a continuous main pump action towards the gas cushion in the chamber (12, 21). A method according to claim 1, characterized in that the chamber with the gas cushions is kept floating at the depth of the lake and attached to the bottom anchoring (M). Apparatus for applying the method according to claim 1 or 2 for oxidizing water in lakes or the like deep enough to divide the water substantially during the summer season into two thermal layers, an upper, warmer layer (epilimnion) and a lower, colder layer (hypolimnion), wherein a mixture of oxygen-containing gas and water is maintained in a hypolimnion in a clock chamber (21) by maintaining a gas cushion in which water-insoluble gas separates from the water stream and is discharged from the chamber into the atmosphere without and a downwardly open mixing channel (27) in the chamber (21) and a gas nozzle (28) disposed in the hypolimnion to conduct oxygen-containing gas to the water at the lower end of the channel (27), the channel (27) and the gas nozzle (28) forming a mammoth pump acting towards the gas cushion pun both to maintain the flow of water and to form a water-air mixture. Device according to Claim 3, characterized in that the chamber (21) extends conically downwards towards the drainage openings (39a-c). Device according to Claim 3 or 4, characterized in that the gas nozzle (28) is annular and oriented substantially perpendicular to the geometric longitudinal axis of the channel (27). Device according to one of Claims 3 to 5, characterized in that the chamber (21) is connected to the anchoring block (44) at the bottom of the lake by means of ropes (43a-c) or the like and is thus adapted to remain floating at depth in the lake.