JP4305956B2 - Water quality conservation system - Google Patents

Description

  The present invention relates to a water quality conservation system for maintaining dissolved oxygen concentration and bottom layer water quality in a closed state such as seas (ports), lakes, dams, and dredgings.

Domestic wastewater and industrial wastewater flow into the sea (ports), lakes, rivers, dams, dredging, etc., and these wastewater contains organic matter and nutrient salts. The growth of phytoplankton due to eutrophication itself causes problems such as coagulation failure, filtration failure, and off-flavor in water purification plants, and in the long term, dead bodies and excrement accumulate in the bottom layer and organic sludge. It becomes.
Since microorganisms in water consume dissolved oxygen to decompose them, if the amount of oxygen supplied to the water in the bottom layer is less than the amount consumed, it becomes in an oxygen-poor state.

When bottom water falls into an anoxic state, organic matter in the bottom mud is anaerobically decomposed, and substances harmful to living organisms such as sulfides and methane gas are generated.
In addition, when the bottom mud is deficient in oxygen, nutrient salts and metals such as iron, manganese, arsenic, and phosphorus in the bottom mud are more likely to elute, increasing the concentration of nutrients in the water, causing the occurrence of red sea bream and red tide, It causes environmental deterioration.

  Fig. 3 shows an example of the distribution of water temperature in harbors, lakes, dam lakes, etc. (hereinafter collectively referred to as Lake 1). In summer, the temperature T is high near the water surface, and the temperature suddenly increases as the water depth decreases. The state where the temperature jump layer A which falls is formed is shown typically. A solid line C shows a temperature distribution curve, and the bottom of the water has the lowest temperature.

In such a state, water having a low temperature and a high density forms a water mass, and there is almost no mixing with water having a high water temperature and a low density near the surface layer. This is called density stratification.
Accordingly, water having a high dissolved oxygen concentration near the surface layer is not supplied to the bottom layer, and the poor oxygen state of the bottom layer is not eliminated.

  Such a phenomenon occurs not only due to the difference in water temperature (temperature jump layer A), but also due to the formation of a salt jump layer in which the salt concentration rapidly changes as in a brackish water area.

  FIG. 4 shows an example of a conventional apparatus that supplies oxygen to the water in the bottom layer that has become poorly oxygenated in this manner, and illustrates an apparatus using an aeration apparatus and an apparatus using a water flow generator. In FIG. 4, the oxygen supply technique by the aeration apparatus is shown on the left side of the lake 1 and the oxygen supply technique by the water flow generator is shown on the right side.

  First, an oxygen supply technique using an aeration apparatus will be described. The aeration apparatus shown in the figure is called full-layer aeration, and sends air to the bottom of the water by the air compressor 2 and releases this compressed air from the diffuser plate 3 to the bottom of the water. Increase in dissolved oxygen in the bottom layer and entrained water The aim is to supply dissolved oxygen from the upper layer to the bottom of the water by the destruction of the thermocline due to. Moreover, the circulation of water causes a decrease in the surface water temperature, the phytoplankton being drawn deeper than the lighted layer, and the diffusion of algae, which is effective as a phytoplankton countermeasure.

  However, in such a method, the bottom mud is rolled up by the entrained water, and there is a problem that nutrient salts are supplied from the lower layer to the upper layer, thereby deteriorating the water quality of the entire water area. In addition, in order to prevent the bottom mud from rolling up, there is a device called shallow aeration in which the air release position is set high, but such a device cannot supply oxygen to the water in the bottom layer.

  Next, an oxygen supply technique using a water flow generator will be described. As shown on the right side of FIG. 4, in this oxygen supply technology, the surrounding water is taken as entrained water by sucking the surface water rich in dissolved oxygen by the pump 4 constituting the water flow generator and releasing it to the bottom of the water. It is mixed with the lower layer water to supply dissolved oxygen to the bottom layer.

  However, the surface water has a high temperature and a low density, so it does not mix with the water with a low bottom layer temperature and a high density, and in the same way as described above, the bottom mud rolls up and deteriorates the water quality of the entire water area. There is a disadvantage of letting it.

FIG. 5 shows an oxygen-dissolved water supply method. After the bottom layer water in an oxygen-poor state is pumped up, oxygen is dissolved in the water by the oxygen-dissolving means 5 to increase the dissolved oxygen concentration. It is configured to return to the original bottom layer.
In this way, if it is configured to return the low-temperature water to the original low-temperature water area, it will not be mixed due to the difference in density, and no upward flow will occur due to the high temperature. No bottom mud is rolled up.

However, the apparatus shown in FIG. 5 can efficiently supply oxygen to the water in the bottom layer, but there is no method for objectively evaluating the effect of supplying oxygen, and the oxygen-dissolved water supply apparatus can be operated efficiently. Can not. Conventionally, there is an example where a timer is used to control the operation of the oxygen-dissolved water supply device. However, the operation is only repeated at regular intervals, and the oxygen supply effect (water quality improvement degree) is not detected. Absent.
In addition, since water does not circulate from the upper layer to the lower layer, it cannot be desired to suppress the photosynthesis as a phytoplankton countermeasure.

JP 2003-071494 A

  As described above, in the conventional oxygen supply method with entrained water, the bottom mud is rolled up by the entrained water, and there is a problem that the water quality of the entire water area is deteriorated, and the bottom layer in an oxygen-poor state In the oxygen supply method in which water is pumped up, oxygen is dissolved in the water by oxygen dissolving means, and then returned to the original bottom layer, there is no method for objectively evaluating the effect of supplying oxygen, and oxygen dissolved water supply There is a problem that the apparatus cannot be operated efficiently, and water is not circulated from the upper layer to the lower layer, and an effect cannot be expected as a phytoplankton countermeasure.

  The present invention has been made to solve the above problems, and can detect the effect of supplying oxygen to efficiently control the operation of the oxygen-dissolved water supply device, and as a measure against phytoplankton. The purpose is to provide an effective water quality conservation system.

  In order to achieve such an object, the water quality maintenance system of the present invention has the following configuration.

(1) The water quality preservation system is an aeration system that releases air to a water area of an arbitrary depth in a water quality preservation system for maintaining the water quality of water areas having density stratification with different water temperatures, salinity concentrations or suspended solids concentrations. Water is sucked from the water means below the circulation means and the air discharge part of the aeration circulation means, oxygen is dissolved in the sucked water, and the obtained oxygen-dissolved water is below the air discharge part of the aeration circulation means. And an oxygen-dissolved water supply means for discharging into the water area.

(2) The oxygen-dissolved water supply means includes a suction means for sucking water from a water area at an arbitrary depth below the air discharge portion of the aeration circulation means, an oxygen dissolving means for dissolving oxygen in the sucked water, and (1) The water quality maintenance system according to (1), characterized by comprising discharge means for discharging the obtained oxygen-dissolved water into a deep water area where water is sucked by the suction means.

(3) A first conductivity meter for measuring the conductivity of water in the water area below the air discharge portion of the aeration circulation means is provided, and the oxygen-dissolved water supply is provided according to the output of the first conductivity meter. The water quality maintenance system according to (1) or (2), wherein the operation of the means is controlled.

(4) The water quality maintenance system according to (3), wherein the first conductivity meter measures the conductivity of water sucked by the oxygen-dissolved water supply means.

(5) A second conductivity meter for measuring the conductivity of water in the water area above the air discharge portion of the aeration circulation means is provided, and according to the output of the second conductivity meter, the aeration circulation means The water quality maintenance system according to (3) or (4), wherein the operation is controlled.

(6) The water quality maintenance system according to (5), wherein the second conductivity meter measures the conductivity of water near the surface layer in a water area.

(7) The aeration / circulation means is a multi-stage aeration / circulation means having a plurality of air discharge sections having different water depths, and the position of the air discharge section in the multi-stage aeration / circulation means according to the output of the second conductivity meter. And the presence or absence of air discharge is controlled, The water quality maintenance system as described in (5) or (6) characterized by the above-mentioned.

(8) The water quality maintenance system according to (7), wherein the position of the air discharge unit and / or the presence / absence of air discharge in the multistage aeration / circulation means are controlled in accordance with the output of the first conductivity meter. .

  According to the present invention, in the water quality maintenance system for maintaining the water quality of the water area having the density stratification with different water temperature, salinity concentration or suspended solids concentration, the aeration circulation means for releasing air to the water area of any depth And water from the water area below the air discharge part of the aeration circulation means, oxygen is dissolved in the sucked water, and the obtained oxygen-dissolved water is the water area below the air discharge part of the aeration circulation means The oxygen-dissolved water supply means to be discharged into the water is not accompanied by entrained water when the oxygen is dissolved or the oxygen-dissolved water is discharged into the water. Water that does not deteriorate the water quality of the entire body of water and causes water circulation above the air discharge part of the aeration and circulation means, which is also effective as a phytoplankton countermeasure. It is possible to provide a conservation system.

  In addition, the oxygen supply effect is considered as a change in the conductivity of the water in the bottom layer, and the operation of the oxygen-dissolved water supply means is controlled according to the output of the conductivity meter. The supply effect can be detected, and the operation of the oxygen-dissolved water supply means can be controlled efficiently.

  Furthermore, since the conductivity of water is measured in the vicinity of the surface layer or in the water area above the air discharge part of the aeration circulation means, the operation of the aeration circulation means is controlled. It is possible to detect the rolling up of mud, and effective phytoplankton measures can be taken without causing the rolling up of the bottom mud.

  Hereinafter, an embodiment of a water quality maintenance system according to the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of the water quality maintenance system of the present invention. In the figure, the same components as those in FIGS. 2 to 4 are denoted by the same reference numerals. Reference numeral 6 denotes aeration circulation means, and here, a multi-stage aeration circulation means having a plurality of air discharge portions with different water depths is illustrated. The aeration circulation means 6 is installed so that the air discharge part is located in the water area above the density stratification. Reference numeral 7 denotes oxygen-dissolved water supply means, which includes a pump 4 and oxygen dissolver 5, a bottom water suction part 71, and an oxygen-dissolved water discharge part 72. The suction part 71 and the discharge part 72 are arranged so as to be located in a water area below the air discharge part (density stratification) of the aeration circulation means 6. Reference numeral 8 denotes a first conductivity meter that measures the conductivity of water pumped up through the suction unit 71, and reference numeral 9 denotes a second conductivity meter that measures the conductivity of water near the surface layer. Reference numeral 10 denotes a selective water intake facility for taking water from an arbitrary depth.

  That is, the aeration and circulation means 6 performs aeration operation in the water area above the density stratification to generate water circulation, lowering the surface water temperature, drawing the phytoplankton deeper into the lighted layer, spreading algae, etc. In addition, the oxygen-dissolved water supply means 7 sucks the oxygen-poor water and discharges the oxygen-dissolved water in the water area below the density stratification, and supplies oxygen to the water in the bottom layer. The entire water quality is preserved (improved).

  The output of the first conductivity meter 8 is used to control the operation of the oxygen-dissolved water supply means 7. When the conductivity of the water pumped from the bottom layer falls below a certain value, the operation of the oxygen-dissolved water supply means 7 is performed. Alternatively, the supply of oxygen to the oxygen dissolving means 5 is stopped.

Here, the relationship between the oxygen supply to the water in the bottom layer and the conductivity of the water is as follows.
As described above, when the bottom layer water (bottom mud) becomes deficient in oxygen, nutrient salts such as iron, manganese, arsenic, and phosphorus in the bottom mud and metals are likely to elute, and the conductivity of the bottom layer water increases. On the other hand, when oxygen is supplied to the bottom layer water and the poor oxygen state is improved, elution of these nutrient salts and metals is suppressed, and the conductivity of the bottom layer water is lowered.
An example of the correlation between the concentration of manganese, which is one type of eluted metal, and the conductivity of water is shown in FIG.

  Therefore, there is a certain correlation between the elution of nutrients and metals and the conductivity of the bottom water, and by measuring the conductivity of the bottom water, the degree of suppression of the elution of nutrients and metals in the bottom water, that is, The degree of improvement in water quality (the effect of supplying oxygen) can be known.

  As a result, when the operation control of the oxygen dissolved water supply means 7 is performed using the output of the first conductivity meter 8, the oxygen supply effect is detected and the operation of the oxygen dissolved water supply device is efficiently controlled. be able to. In addition, the conductivity meter can be obtained at a lower cost than a dissolved oxygen meter, and the equipment cost can be reduced.

  Further, the output of the second conductivity meter 9 is used for operation control of the aeration circulation means 6, and when the conductivity of water near the surface layer rises above a certain value, the operation of the aeration circulation means 6 is stopped or the air is discharged. The parts are switched.

  Here, when the electrical conductivity of the water near the surface layer is monitored, the raising of the bottom mud by the aeration circulation means 6 can be detected. That is, when the bottom mud is rolled up due to the circulation of water accompanying the aeration operation, the nutrient salt eluted in the bottom layer is diffused near the surface layer, so that the conductivity of water near the surface layer is increased.

Therefore, if the operation control of the aeration circulation means 6 is performed by using the output of the second conductivity meter 9, it is possible to detect the occurrence of bottom mud and to prevent effective phytoplankton measures without generating the bottom mud. It can be performed.
In the case of the multistage aeration and circulation means shown in the figure, the position of the air discharge part is moved upward as the conductivity increases. Thereby, the depth which water circulates can be made shallow, and the influence by circulation can be reduced.

Further, since the water depth at which the density stratification is formed changes depending on the season, the position of the air discharge unit can be moved up and down in accordance with the water depth, and more efficient operation is possible.
Furthermore, not only the movement of the air discharge unit, but also the operation of the aeration circulation means 6 can be completely stopped and the oxygen supply can be switched to the oxygen dissolved water supply means 7 alone.

In the above description, the case where the aeration circulation means 6 is installed so that the air discharge portion thereof is located in the water area above the density stratification is exemplified, but the installation position of the aeration circulation means 6 is limited to this. Instead, it can be installed in a water area of any depth.
In this case, the installation positions of the suction part 71 and the discharge part 72 in the oxygen-dissolved water supply means 7 are determined so as to be located in the water area below the air discharge part of the aeration circulation means 6.

  In the above description, the case where the first conductivity meter 8 is placed on the water and the conductivity in the water pumped up via the suction part 71 is measured is exemplified. However, the measurement of the first conductivity meter 8 is performed. The position is not limited to this, and the same operation can be performed even if the electrical conductivity in the water in the bottom layer is directly measured.

  Furthermore, although the case where the second conductivity meter 9 is arranged near the surface layer and the conductivity of water near the surface layer is measured is exemplified, the measurement position of the second conductivity meter 9 is not limited to this. If the water area is above the air discharge part of the aeration and circulation means 6, the same operation can be performed even if it is configured to measure the conductivity of water at an arbitrary position.

Further, in the above description, the case where the operation of the aeration circulation means 6 is controlled by the output of the second conductivity meter is exemplified. In addition, the operation of the aeration circulation means 6 is controlled by the output of the first conductivity meter. It can also be configured to control.
In this case, when the output of the first conductivity meter (the conductivity of the water in the bottom layer) rises above a certain value, the operation of the aeration / circulation means 6 is stopped or the air discharge unit is switched.

  In this way, when the operation of the aeration circulation means 6 is controlled by the output of the first conductivity meter, the circulation of water from the deep layer is stopped while a lot of nutrient salts are eluted in the bottom layer water, Diffusion of the eluted substance can be prevented in advance.

The block diagram which shows one Example of the water quality maintenance system of this invention. The block diagram which shows the correlation of manganese concentration and the electrical conductivity of water. Explanatory drawing of the thermocline formed in lakes and marshes. The block diagram which shows an example of the oxygen supply apparatus to the conventional water. The block diagram which shows the other example of the conventional oxygen supply apparatus to water.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lake 2 Air compressor 3 Air diffuser plate 4 Pump 5 Oxygen dissolution means 6 Aeration circulation means 7 Oxygen dissolved water supply means 71 Bottom water suction part 72 Oxygen dissolved water discharge part 8 First conductivity meter 9 Second Conductivity meter 10 Select water intake equipment

Claims (7)

In a water quality maintenance system for maintaining the water quality of a water area having density stratification with different water temperature, salinity concentration or suspended solids concentration in a good state, the water quality maintenance system has an air discharge part that discharges air into water and has an arbitrary water depth in the water area. Aeration circulation means for releasing air to the water area, and water is sucked from the water area below the air discharge part of the aeration circulation means, oxygen is dissolved in the sucked water, and the obtained oxygen-dissolved water is used for the aeration circulation. An oxygen-dissolved water supply means for discharging into a water area below the air discharge part of the means, and a first conductivity meter for measuring the conductivity of water in the water area below the air discharge part of the aeration circulation means, A water quality maintenance system that controls the operation of the oxygen-dissolved water supply means in accordance with the output of the first conductivity meter .   The oxygen-dissolved water supply means includes a suction means for sucking water from a water area at an arbitrary depth below the air discharge part of the aeration circulation means, an oxygen dissolving means for dissolving oxygen in the sucked water, and the obtained oxygen The water quality maintenance system according to claim 1, further comprising discharge means for discharging dissolved water to a water area having a depth of water in which water is sucked by the suction means. The water quality maintenance system according to claim 1 or 2, wherein the first conductivity meter measures the conductivity of water sucked by the oxygen-dissolved water supply means. A second conductivity meter for measuring the conductivity of water in the water area above the air discharge portion of the aeration circulation means is provided, and the operation of the aeration circulation means is controlled according to the output of the second conductivity meter. The water quality maintenance system according to any one of claims 1 to 3, wherein: 5. The water quality maintenance system according to claim 4, wherein the second conductivity meter measures the conductivity of water near a surface layer in a water area. The aeration / circulation means is a multistage aeration / circulation means having a plurality of air discharge sections with different water depths, and the position of the air discharge section and / or air in the multistage aeration / circulation means according to the output of the second conductivity meter. 6. The water quality maintenance system according to claim 4, wherein the presence or absence of discharge is controlled. The water quality maintenance system according to claim 6, wherein the position of the air discharge section and / or the presence / absence of air discharge in the multistage aeration / circulation means are controlled according to the output of the first conductivity meter.

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