JP4933473B2 - Slurry circulation type coagulation sedimentation treatment apparatus and operation method thereof - Google Patents

Description

  The present invention relates to a slurry circulation type coagulation sedimentation treatment apparatus for producing tap water, industrial water, and the like, and an operation method thereof.

  In the coagulation sedimentation treatment in the water treatment, there is a method of promoting the coagulation reaction by adding an agglomeration auxiliary agent serving as a nucleus of the aggregation reaction in the coagulation sedimentation treatment for the raw water having low turbidity. Solid particles such as sand are used as the coagulant aid. When this treatment method is applied to a slurry circulation type agglomeration treatment apparatus, a method has been proposed in which the addition rate of solid particles such as sand is adjusted in accordance with the position of the slurry interface in the sedimentation basin and / or the turbidity of the treated water. On the other hand, there is a method of increasing the sedimentation speed of flocs by attaching sand having ballast function to flocs already formed by agglomeration reaction, but this method has a different processing mechanism based on a completely different idea from the former.

  In the purification process, river water is coagulated and precipitated to remove turbidity components and organic substances. The turbidity of river water in recent years is lower than that of the Showa 30s and 40s due to the construction of a dam upstream, etc., and it is often 10 degrees or less in fine weather and decreases to around 1 degree. It is not uncommon. When the coagulation sedimentation treatment is performed on the raw water having a low turbidity, the coagulation reaction is difficult to proceed or flocs having poor sedimentation properties are formed, and the turbidity of the treatment water is deteriorated.

  In the water purification treatment, the addition rate of an inorganic flocculant such as PAC (polyaluminum chloride) is generally determined based on jartis. An inorganic flocculant addition rate corresponding to the raw water turbidity may be selected based on past jar test results. When the raw water turbidity is low, if the amount of the inorganic flocculant is too small, the aggregation reaction is difficult to occur. On the other hand, when the addition rate of the inorganic flocculant is increased to a sufficient amount that causes the flocculation reaction, the ratio of the inorganic flocculant to the raw water suspension becomes high, and the flocs swell and become difficult to settle.

  For coagulation sedimentation treatment of raw water with low turbidity, as shown in Patent Document 1 and Patent Document 2, solid particles such as sand are aggregated in the raw water before or simultaneously with the addition of the inorganic flocculant. There is a method of adding as an auxiliary agent to promote the agglutination reaction. The addition of the coagulant aid simulates a state in which the turbidity of the raw water has increased. When a coagulant aid is applied to a coagulation treatment device that uses a cross-flow type sedimentation basin, the raw water turbidity is measured, and the turbidity after adding the coagulant aid is insufficient to achieve a predetermined turbidity suitable for the coagulation reaction. The addition may be continuously performed at an addition rate corresponding to the turbidity.

  The addition of the coagulant aid is effective in the slurry circulation type coagulation sedimentation treatment apparatus. The adjustment rate of the coagulant auxiliary agent can be adjusted based on the raw water turbidity in the same manner as the coagulation sedimentation treatment device using the cross-flow type sedimentation basin. It is possible to rationally reduce the additive rate.

  In the slurry circulation type coagulation sedimentation processing apparatus, the slurry containing the coagulant aid settles in the sedimentation section, and the sedimented slurry is returned to the stirring section. For this reason, sufficient turbidity is present at the time of aggregation and the aggregation reaction proceeds. Therefore, it is not necessary to continuously add the aggregation auxiliary agent, and it may be added intermittently depending on the situation. No equipment such as a pump is required to return the slurry from the settling section to the stirring section. The upper part of the stirring blade has a structure that forms a horizontal jet water flow from the center of the stirring blade toward the periphery of the tank, and the amount of water exceeding the amount of raw water flows from the stirring part to the precipitation part via the water channel by the jet water flow from the stirring blade. The amount of water exceeding the amount of raw water is naturally returned as a slurry containing solid particles from the precipitation section to the stirring section.

  In addition, it has a slurry blanket in the sedimentation section, and it is necessary to adjust the rate of addition of the coagulant aid in consideration of the slurry blanket interface state (interface position and change in interface position) and the sludge operation (slurry discharge amount operation). is there. Furthermore, the difficulty of the sedimentation of the slurry in the sedimentation part can be determined by measuring the slurry SV (Sludge Volume), and the addition rate of the coagulant aid using SV can be adjusted. The slurry blanket is a state in which the slurry settles in the settling portion and is separated from the treated water but is not deposited but is floating. The slurry in the settling portion is in a state of being expanded and expanded by the upward flow, and the boundary surface between the supernatant water of the settling portion and the expanded and expanded slurry is the slurry interface. The position of this slurry interface can be measured with an existing slurry interface meter. SV is a volume ratio occupied by sludge deposited when an arbitrary fixed amount of slurry is allowed to stand for a predetermined time, and can be measured by an SV meter or manually. In the slurry circulation type coagulation sedimentation processing apparatus, the measurement is generally performed at a standing time of 5 to 10 minutes.

  When adding a coagulant aid in a slurry circulation type coagulation sedimentation treatment apparatus, it has been conventionally proposed to adjust the addition rate of the coagulant aid according to the position of the slurry interface in the precipitation part and / or the turbidity of the treated water. However, it has become clear from the following situation that the addition rate of insoluble particulate matter such as sand, which is an agglomeration aid, cannot be appropriately adjusted by this method.

  In the sedimentation section (sedimentation basin) of the slurry circulation type coagulation sedimentation processing equipment, a slurry blanket is formed and stays in a state where the rising flow rate of the treated water and the sedimentation of the floc are balanced. When the slurry concentration in the slurry blanket part becomes dense and the sedimentation speed of the floc is slow, the density of the slurry blanket part becomes rough. There are mainly two factors A and B below that change the slurry interface position when the operating conditions are constant.

A. The ratio of the turbidity to the inorganic flocculant is lowered due to the decrease in raw water turbidity, and the specific gravity of flocs is decreased to make it difficult to settle. In this case, the sedimentation speed decreases with the decrease in the specific gravity of the floc, and the slurry blanket expands to raise the slurry interface.
B. The total amount of slurry present in the sedimentation area increases due to the increase in raw water turbidity. As the raw water turbidity increases, the ratio of turbidity to the inorganic flocculant increases and the floc sedimentation improves, and the slurry blanket shrinks and the slurry interface decreases. However, if the amount of increase in slurry in the apparatus becomes larger than the amount of mud due to an increase in inflowing turbidity, the slurry interface will rise.

Appropriate response to A is to increase the flocs sedimentation by increasing the addition rate of the coagulant aid.
Moreover, the response | compatibility with said B is reducing the addition rate of the insoluble granular material which is a coagulant | flocculant, and increasing the amount of sludge.
The factors A and B cannot be distinguished from each other by the treated water turbidity. Therefore, even if the slurry interface position of the sedimentation portion and the treated water turbidity are combined, appropriate adjustment cannot be performed.

On the other hand, it is possible to adjust the addition rate of the coagulant aid based on the raw water turbidity, similar to the adjustment of the coagulant aid addition rate in the cross-flow type sedimentation basin, but the addition rate becomes excessive. The addition of the coagulant aid is performed to promote the coagulation reaction and form a slurry that easily settles. If a slurry that is easy to settle even if the raw water turbidity is low, the addition of the coagulant aid is added. Is unnecessary. Even if the raw water turbidity is low, it is not necessary to immediately add the coagulant aid unless the slurry interface position of the sedimentation basin is raised and the treated water turbidity is deteriorated.
JP 2006-7086 A Special table 2003-326110 gazette

  The present invention has been made in view of the above points, and in the slurry circulation type coagulation sedimentation treatment apparatus, even when the raw water turbidity is low or the sedimentation property of the flock fluctuates depending on the raw water turbidity, the slurry interface level of the sedimentation part. It is an object to provide a slurry circulation type coagulation sedimentation treatment apparatus capable of efficiently obtaining treated water from raw water with low turbidity and an operating method thereof.

The present invention for solving the above problems, a stirring portion for forming a slurry by stirring raw water and an inorganic coagulant, provided through the stirring拌部and waterways unit, for purifying the slurry is introduced from the water channel precipitation unit to form a treated aqueous layer above the slurry blanket to form a slurry blanket downward in the slurry circulating coagulating sedimentation processing apparatus having a flow path for returning to the stirring section slurry from below the precipitation unit, Solid particle supply means for supplying solid particles to increase the specific gravity of the slurry to the raw water, an SV meter for detecting the SV value of the slurry guided to the settling part, and detecting the position of the slurry interface of the slurry blanket formed in the settling part A slurry interface unit that discharges slurry under the slurry blanket from the bottom of the sedimentation unit or the bottom of the stirring unit, and the SV value detected by the SV meter and the slurry interface meter The position of the slurry interface is stored, the SV value detected by the SV meter is set as the current SV value, and the time change of the SV value is calculated from the current SV value and the stored SV value, and detected by the slurry interface meter. The time change of the position of the slurry interface is calculated from the position of the current slurry interface and the stored position of the slurry interface, and the SV measured value by the SV meter and its time change, Based on the measurement position of the slurry interface by the slurry interface meter and its change over time, it is determined whether to increase or decrease the solid particle addition amount and the slurry discharge amount, respectively, or to maintain the current state, and to supply the solid particle and controlling the slurry discharge means, the addition ratio of the solid particles along with just enough properly adjusted, provided a control means for adjusting such that the position of the slurry interface is maintained at a predetermined position It is characterized in.

As described above, the SV value detected by the SV meter is set as the current SV value, the time change of the SV value is calculated from the current SV value and the stored SV value, and the position of the slurry interface detected by the slurry interface meter is determined at this time. The time change of the position of the slurry interface is calculated from the current position of the slurry interface and the stored position of the slurry interface, and based on the time change of the SV value and the time change of the interface position , the solid particle Determine whether to increase or decrease the amount of slurry added and the amount of slurry discharged, respectively, and control the solid particle supply means and slurry discharge means to control the solid particle supply amount and slurry discharge amount. In addition, the control means for adjusting the addition rate of the solid particles properly without excess and deficiency and adjusting the position of the slurry interface to be maintained at a predetermined position is provided. The addition rate of body particles can be adjusted appropriately without excess and deficiency, and the discharge amount of slurry accumulated in the device can be adjusted appropriately without excess and deficiency, the slurry interface level can be maintained at a predetermined position, and raw water with low turbidity can be maintained. Treated water can be obtained efficiently.

Further, the present invention includes a stirring unit to form a slurry by stirring raw water and an inorganic coagulant, provided through the stirring section and waterways portion, the slurry blanket for purifying slurry introduced from said water channel downward in the method of operating the precipitation unit to form a treated aqueous layer above the slurry blanket, slurry recycling coagulating sedimentation processing apparatus having a flow path for returning to the stirring section slurry from below the precipitation section thereby forming a stirring The SV value of the slurry guided to the sedimentation section through the water channel section is measured with a SV meter at a predetermined time interval, and the position of the slurry interface of the slurry blanket formed in the sedimentation section is measured with a slurry interface meter at a predetermined time interval. , from the measured SV value and location and time interval of the time interval and the measured slurry interface to calculate the time variation of the time change and the position of the slurry surface of the SV value, the SV value and the SV value Based on the time change and the time change of the position of the slurry interface and the position of the slurry interface, it is determined whether to increase or decrease the solid particle addition amount and the slurry discharge amount, respectively, or to maintain the current state. by adjusting the supply amount and the slurry discharge amount that will be discharged by the slurry discharge means of the solid particles that will be supplied by the particle supply means, the addition ratio of the solid particles along with just enough properly adjusted, the position of the slurry interface position It is characterized by adjusting so that it may be maintained.

As described above, based on the SV value and the time change of the SV value, and the time change of the position of the slurry interface and the position of the slurry interface, the addition amount of solid particles and the discharge amount of slurry are increased or decreased, respectively. The amount of solid particles to be added and the amount of slurry discharged are adjusted, so that the addition rate of solid particles such as sand to be added as a coagulant aid can be adjusted appropriately without excess and equipment. The amount of slurry accumulated in the slurry can be adjusted appropriately without excess and deficiency, the slurry interface level of the slurry blanket formed in the settling area can be maintained at a specified position, and treated water can be efficiently obtained from raw water with low turbidity Can do.

Further, the present invention is characterized in that in the operation method of the slurry circulation type coagulation sedimentation treatment apparatus, the solid particles for increasing the specific gravity of the slurry are particles mainly composed of SiO ₂ .

  The present invention is also characterized in that, in the operation method of the slurry circulation type coagulation sedimentation treatment apparatus, the solid particles that increase the specific gravity of the slurry are powdered activated carbon.

The solid particles are granular materials having a specific gravity of 2.0 to 4.0 and insoluble in water. Sand, powdered activated carbon, kaolin and the like are effective, and among these, sand is preferable. Furthermore, silica sand whose main component is SiO ₂ is more preferable.

  In order to solve the above problems, the present invention rationally determines the addition rate of solid particles that increase the specific gravity of the slurry as an agglomeration aid when the raw water turbidity is low or when the floc sedimentation changes depending on the raw water turbidity. It adjusts properly without excess and deficiency, discharges the slurry accumulated in the equipment without excess and deficiency, maintains the slurry interface at the prescribed depth of the sedimentation section, and efficiently treats low turbidity treated water (precipitation water) Can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a slurry circulation type coagulation sedimentation processing apparatus according to the present invention. As shown in FIG. 1, the slurry circulation type coagulation sedimentation treatment apparatus includes a landing well 1 and a slurry circulation type coagulation sedimentation treatment tank 2. The landing well 1 is an intake pond into which raw water taken from a water source such as river water, lake water, or groundwater flows. The slurry circulation type coagulation sedimentation treatment tank 2 is provided with a stirring part (stirring tank) 3 below the center, a sedimentation part (precipitation tank) 5 is arranged at the upper part of the periphery of the stirring part 3, and a water channel part 4 is arranged at the center upper part. is there. A stirring blade 6 is disposed in the stirring unit 3, and the stirring blade 6 is rotated by a stirring motor 7.

A water collecting basin 8 for collecting treated water (precipitated water) is provided at the upper part of the sedimentation section 5 of the slurry circulation type coagulation sedimentation treatment tank 2, and the treated water that has flowed into the water collecting basin 8 passes through the treated water discharge pipe 9 to be predetermined. Water is to be sent to the place. In addition, a slurry discharge pipe 10 is provided below the settling portion 5, and a sludge pump 11 is disposed in the slurry discharge pipe 10. Further, a pH meter 14 for measuring pH and an SV meter 15 for measuring SV value are provided in the water channel portion 4, and a slurry interface meter 16 for detecting a slurry interface is provided in the sedimentation portion 5. In addition, solid particles (here, silica sand mainly composed of SiO ₂ ) serving as an agglomeration aid are supplied into the stirring unit 3 by a solid particle addition pump 12 through a solid particle supply pipe 13. . As the solid particles, sand, powdered activated carbon, kaolin, etc., which are granular materials insoluble in water having a specific gravity of 2.0 to 4.0 as described above, are effective. Among these, sand is preferable. Furthermore, silica sand whose main component is SiO ₂ is more preferable.

The inorganic flocculant-added raw water in which the inorganic flocculant 18 is added to the raw water 17 of the landing well 1 is supplied to the stirring unit 3 of the slurry circulation type coagulation sedimentation treatment tank 2 through the raw water introduction pipe 21 and stirred by the stirring blade 6. The The inorganic flocculant-added raw water is stirred and pressurized by the stirring blade 6 and flows into the water channel portion 4 and flows into the sedimentation portion 5 via the water channel portion 4. In the sedimentation section 5, flocs settle, and the clear supernatant water flows into the catchment basin 8 as treated water (precipitated water) and is sent to a predetermined place through the treated water discharge pipe 9. The addition rate of inorganic flocculant 18 (the amount of inorganic flocculant added per unit raw water amount) is determined based on the turbidity measurement value of raw water 17 measured by turbidimeter 19 or the result of manual jar test, An amount of the inorganic flocculant 18 corresponding to the flow rate of the raw water 17 measured by the flow meter 20 is added. The inorganic flocculant 18 may be supplied to the raw water of the stirring unit 3. In the agglutination reaction, pH is an important reaction factor, and the pH value after the agglomeration reaction is measured with a pH meter 14 installed in the water channel 4 so that the pH value range is appropriate for the agglomeration reaction, but NaOH is not shown. And a pH adjuster such as H ₂ SO ₄ is added to the raw water. In general, the aggregation reaction is carried out in the range of pH 6.5 to 7.5.

  Slurry flows not only from the raw water 17 and the inorganic flocculant 18 but also from the bottom of the sedimentation section 5 into the agitation unit 3, and solid particles that are coagulant aids are fed by the solid particle addition pump 12 through the solid particle supply pipe 13. Being injected. In the stirring unit 3, these are mixed and stirred, so that the agglomeration reaction proceeds quickly, and a slurry having good sedimentation is formed. The formed slurry flows into the sedimentation section 5 via the water channel section 4 and sinks, but some of the slurry expands in a state balanced with the ascending flow rate without being deposited by the upward flow in the sedimentation section 5. A slurry blanket 22 is formed. By passing the treated water through the slurry blanket 22, fine flocs are captured by the slurry blanket 22 and clarification is promoted. On the slurry blanket 22, a layer of treated water which is a clear supernatant water after the solid-liquid separation is completed is formed. The treated water in the treated water layer flows over the upper end of the water collecting basin 8 and is sent through the treated water discharge pipe 9 as treated water (precipitated water). The boundary surface between the slurry blanket 22 and the treated water layer is a slurry interface 23, and the position of the slurry interface 23 is detected by the slurry interface meter 16.

  When it becomes difficult for the slurry to settle in the settling portion 5, the slurry blanket 22 expands and the position of the slurry interface 23 rises so that the sedimentation of the slurry and the rising flow rate can be balanced. When it becomes difficult to settle, the slurry interface 23 rises beyond the upper end of the catchment 8 of the settling part 5, and the slurry overflows into the catchment 8. Therefore, it is necessary to grasp both the position of the slurry interface 23 and the settling property of the slurry and take measures so that the position of the slurry interface 23 does not become too high or the settling property of the slurry does not become too bad.

In order to improve the sedimentation property of the slurry, it is to increase the specific gravity of the slurry. Here, the solid particle addition means composed of the solid particle addition pump 12 and the solid particle supply pipe 13 is used in the stirring unit 3. Solid particles (here, silica sand whose main component is SiO ₂ ) as an agglomerating aid are injected. On the other hand, even if the sedimentation property of the slurry is good, the slurry interface 23 rises as the slurry accumulates in the slurry circulation type coagulation sedimentation treatment tank 2. In this case, the slurry is discharged (sludge) from the bottom of the settling portion 5 by the slurry discharge means including the slurry discharge pipe 10 and the sludge pump 11.

  In order to grasp the sedimentation property of the slurry flowing into the sedimentation part 5 and its change, an SV meter 15 for measuring the SV value is installed in the water channel part 4 to grasp the position of the slurry interface 23 of the sedimentation part 5 and its change. For this purpose, a slurry interface meter 16 for measuring the position of the slurry interface 23 is installed in the sedimentation section 5. As will be described in detail later with reference to FIG. 4, the SV measurement value by the SV meter 15 and the slurry interface measurement position by the slurry interface meter 16 are sent as electrical signals to the control means 32, and each of the SV measurement value and the slurry interface measurement position is shown. The data is stored in a predetermined area of the RAM 32-2, and the CPU 32-1 calculates and calculates temporal changes in the SV value and the interface position, and according to the calculation result, the addition rate and slurry of the solid particles are calculated. Judgment is made on whether to increase, decrease or maintain the current status. Based on this determination, a control signal is sent from the control means 32 to the solid particle addition pump 12 and the sludge pump 11 to change the operation conditions.

  2 and 3 are diagrams showing an example of determination of adjustment of the addition amount of solid particles as a coagulant auxiliary agent and adjustment of slurry discharge amount (drainage amount) performed in the slurry circulation type coagulation sedimentation processing apparatus of the present invention. . 2 is connected to the reference A in FIG. Adjustment of the addition amount of solid particles and adjustment of the slurry discharge amount are performed according to the following procedure.

  First, the current SV value (SV measurement value (%)) measured by the SV meter 15 is compared with the reference value (SV reference value (%)), and whether the current SV value is high or low. To evaluate. The SV value reference value is generally set in accordance with the apparatus in the range of 10 to 30% of SV value after standing for 10 minutes. Second, it evaluates whether the SV measurement is increasing or decreasing. Third, the slurry interface position measured by the slurry interface meter 16 is compared with a reference value to evaluate whether the current position of the slurry interface 23 is high or low. The reference value of the slurry interface 23 is set according to the water depth of the sedimentation part 5 according to the apparatus. Fourth, it is evaluated whether the position of the slurry interface 23 is rising or falling.

There are six states described below by the above four evaluations, and there are first to sixth adjustments for adjusting the addition amount SA of solid particles and adjusting the slurry discharge amount SL according to each state.
First adjustment: Maintaining the current state of the solid particle addition rate SA (→), maintaining the current state of the slurry discharge SL (→)
・ Second adjustment: Maintaining the current rate of solid particle addition SA (→), reducing slurry discharge SL (↓)
・ Third adjustment: increase of solid particle addition rate SA (↑), maintenance of slurry discharge SL (→)
-Fourth adjustment: reduction of solid particle addition rate SA (↓), maintenance of current state of slurry discharge SL (→)
-Fifth adjustment: Reduction of solid particle addition rate SA (↓), increase of slurry discharge SL (↑)
・ Sixth adjustment: Maintain the current state of solid particle addition rate SA (→), increase slurry discharge SL (↑)

  When both the solid particle addition rate and the slurry discharge amount are changed as in the fifth adjustment, it is preferable to prioritize the change of the slurry discharge amount. In particular, in situations where the slurry interface 23 becomes high and the amount of slurry discharged must be increased, the slurry interface 23 is rapidly lowered to prevent the slurry from overflowing into the catchment 8 and the slurry from overflowing into the treated water. Need to do. Although both the slurry discharge and the solid particle addition have the effect of lowering the slurry interface 23, the slurry discharge is more effective. Hereinafter, the adjustment of the addition amount of the solid particles and the adjustment of the slurry discharge amount will be described with reference to FIGS.

  First, in step ST1, the SV value measured by the SV meter 15 is compared with the reference value to evaluate whether the SV value is higher or lower than the reference value. If it is below the standard, the process proceeds to step ST2, and if it exceeds the standard, the process proceeds to step ST9 (see FIG. 3). In step ST2, it is evaluated whether or not there is a change in the SV value. If the SV value is decreased or maintained, the process proceeds to step ST3. If the SV value is increased, the process proceeds to step ST4.

  In step ST3, the interface position (slurry interface 23 position) measured by the slurry interface meter 16 is compared with a reference value. If the interface position is below the reference, the process proceeds to step ST5, and if it exceeds the standard, the process proceeds to step ST6. To do. In step ST5, it is evaluated whether or not there is a change in the interface position (the position of the slurry interface 23 measured by the slurry interface meter 16). If the interface position is lowered or maintained, the solid particle addition rate SA is maintained as it is. (→) to reduce (↓) the slurry discharge amount SL (second adjustment). When the interface position is increased, the solid particle addition rate SA is maintained as it is (→), and the slurry discharge amount SL is maintained as it is (→) (first adjustment). In step ST6, it is evaluated whether or not there is a change in the interface position. If the interface position is lowered or maintained, the solid particle addition rate SA is reduced (↓), and the slurry discharge amount SL is maintained (→). (4th adjustment). When the interface position is increased, the solid particle addition rate SA is reduced (↓), and the slurry discharge amount is increased (↑) (fifth adjustment).

  In step ST4, the interface position is compared with the reference value, and if it is below the reference, the process proceeds to step ST7, and if it exceeds the reference, the process proceeds to step ST8. In step ST7, it is evaluated whether or not there is a change in the interface position. If the interface position is lowered or maintained, the solid particle addition rate SA is maintained (→) and the slurry discharge amount is reduced (↓) (No. 1). 2 adjustment). When the interface position is increased, the solid particle addition rate SA is maintained as it is (→), and the slurry discharge amount SL is maintained (→) (first adjustment). In step ST8, it is evaluated whether there is a change in the interface position. If the position of the slurry interface 23 is lowered or maintained, the solid particle addition rate SA is maintained (→), and the slurry discharge amount SL is maintained. (→) (first adjustment). When the interface position rises, the solid particle addition rate SA is maintained as it is (→), and the slurry discharge amount SL is increased (↑) (sixth adjustment).

  In step ST9, it is evaluated whether or not there is a change in the SV value. If the SV value is decreased or maintained, the process proceeds to step ST10, and if it is increased, the process proceeds to step ST11. In step ST12, the interface position is compared with a reference value. If the interface position is equal to or less than the reference, the process proceeds to step ST12. If the reference position is exceeded, the process proceeds to step ST13. In step ST12, it is evaluated whether there is a change in the interface position. If the interface position is lowered or maintained, the solid particle addition rate SA is maintained (→), and the slurry discharge SL is reduced (↓) ( Second adjustment). When the interface position is increased, the solid particle addition rate SA is maintained as it is (→), and the slurry discharge amount SL is maintained (→) (first adjustment). In step ST13, it is evaluated whether or not there is a change in the position of the slurry interface 23 measured by the slurry interface meter 16. If the measurement position is lowered or maintained, the solid particle addition rate SA is maintained as the current state (→). Then, the current slurry discharge amount SL is maintained (→) (first adjustment). When the position of the slurry interface 23 is rising, the solid particle addition rate SA is maintained (→), and the slurry discharge amount SL is maintained (→) (first adjustment).

  In step ST11, the interface position is compared with a reference value. If the interface position is equal to or less than the reference, the process proceeds to step ST14. If the reference position is exceeded, the process proceeds to step ST15. In step ST14, it is evaluated whether or not there is a change in the interface position. If the measurement position is lowered or maintained, the solid particle addition rate SA is maintained (→), and the slurry discharge SL is reduced (↓) ( Second adjustment). When the interface position is increased, the solid particle addition rate SA is maintained as it is (→), and the slurry discharge amount SL is maintained (→) (first adjustment). In step ST15, it is evaluated whether there is a change in the interface position. If the measurement position is lowered or maintained, the solid particle addition rate SA is increased (↑), and the slurry discharge amount SL is maintained (→). (Third adjustment) is performed. When the interface position is increased, the solid particle addition rate SA is increased (↑), and the slurry discharge amount SL is maintained (→) (third adjustment).

  The adjustment of the solid particle addition rate SA and the adjustment of the slurry discharge amount SL are shown in FIGS. 2 and 3 based on the SV value measured by the SV meter 15 and the position of the slurry interface 23 measured by the slurry interface meter 16. Depending on the evaluation / judgment, the solid particle addition rate SA and the slurry discharge amount SL may be adjusted by operating the solid particle addition pump 12 and the sludge pump 11 manually. However, as shown in FIG. Control means 32 may be provided to perform automatically.

  In FIG. 4, the control means 32 includes a CPU 32-1, RAM 32-2, ROM 32-3, I / O 32-4, and I / O 32-5. SV value measured by SV meter 15, position of slurry interface 23 measured by slurry interface meter 16, raw water flow rate measured by flow meter 20, turbidity of raw water measured by turbidimeter 19, pH meter 14 is input to the control means 32 via the I / O 32-4, and each data is stored in a predetermined area of the RAM 32-2. The CPU 32-1 executes the program stored in the ROM 32-3, and the SV value measured by the SV meter 15 and its change, and the slurry interface position measured by the slurry interface meter 16 and its change are shown in FIG. And the evaluation / judgment as shown in FIG. 3 is performed, and the solid particle addition pump 12 and the sludge pump 11 are operated through the I / O 32-5 to automatically perform the first to sixth adjustments.

Further, the CPU 32-1 uses the program stored in the ROM 32-3 to add the inorganic flocculant 18 based on the raw water turbidity measured by the turbidimeter 19 and the raw water flow measured by the flow meter 20. The amount is calculated, the inorganic flocculant addition mechanism 33 (not shown in FIG. 1) is operated, and the inorganic flocculant 18 is added to the raw water 17. Further, from the pH value of the slurry of the water channel part 4 measured by the pH meter 14, the pH after the aggregation reaction is in a pH range suitable for the aggregation reaction (generally pH 6.5 to 7.5 range) An addition amount of a pH adjusting agent such as NaOH or H ₂ SO ₄ is calculated, and the pH adjusting mechanism 34 (not shown in FIG. 1) is operated to add the pH adjusting agent to the raw water.

  An example of the slurry interface meter 16 for measuring the slurry interface 23 in FIG. 1 is an “Ebara Interface Meter” manufactured by EBARA Environmental Engineering. This slurry interface meter includes an ultrasonic echo method and a transmitted light method. The ultrasonic echo method is a method of detecting the position of the slurry interface 23 by emitting an ultrasonic wave downward from an ultrasonic wave transmission unit fixed in the supernatant water and detecting the echo. In the transmitted light method, the sensor unit is automatically moved up and down to detect the transmitted light, and when the sensor unit is located above the slurry interface 23, the light transmittance is high, and the slurry interface When the position is below 23, the position of the slurry interface 23 is detected by utilizing the fact that the light transmittance is low.

  As an example of the SV meter 15 for measuring the SV value in FIG. 1, “SV analyzer” manufactured by EBARA Environmental Engineering is cited. In this SV meter, the sample slurry is introduced into a transparent sedimentation tube by the suction force of a vacuum pump, and the position of the slurry interface after standing in the sedimentation tube for a predetermined time is detected by the transmittance. The upper part of the settling tube has a high light transmittance because the slurry settles into clear water, and the lower part of the settling tube has a low light transmittance due to the settled sludge.

  Next, the present invention will be specifically described with reference to experimental examples. FIG. 5 is a diagram showing a configuration example of the experimental apparatus, and the portions denoted by the same reference numerals as those in FIG. 1 indicate the same or corresponding portions. This experimental apparatus includes a coagulation tank 35 including a stirring unit 3 and a water channel unit 4 and a precipitation unit 5. The raw water 17 to which the inorganic flocculant 18 is added is introduced into the stirring unit 3, and the stirring blade 6 is rotated by the stirring motor 7 in the stirring unit 3, whereby the raw water 17 and the inorganic flocculant 18 are stirred. The mixed liquid of the stirred raw water 17 and the inorganic flocculant 18 becomes a slurry and flows into the flock formation part 5a of the precipitation part 5 through the water channel part 4 and settles, but some of the slurry rises in the precipitation part 5. The slurry blanket 22 is formed in a state where it is balanced with the rising flow velocity without being deposited by the flow.

  Solid particles are injected into the stirring unit 3 by a solid particle addition pump 12 through a solid particle supply pipe 13. By passing the treated water through the slurry blanket 22, fine flocs are captured by the slurry blanket 22 and clarification is promoted. On the slurry blanket 22, a layer of treated water, which is a clear supernatant water after solid-liquid separation, is formed and flows out as treated water (precipitation water). The interface between the slurry blanket 22 and the treated water layer is a slurry interface 23.

The slurry in the settling unit 5 is returned to the stirring unit 3 by the slurry circulation pump 24, and the stirring unit 3 contains a coagulant aid depending on the SV value of the water channel unit 4 and the position of the slurry interface 23 of the settling unit 5. Some solid particles (here, silica sand whose main component is SiO ₂ ) are injected. Since this experimental apparatus is small, it is difficult to install an SV meter or a slurry interface meter used in an actual slurry circulation type coagulation sedimentation processing apparatus. Therefore, here, the SV value is obtained by collecting 100 mL of the slurry of the water channel section 4 in a transparent graduated cylinder and measuring the amount of sludge after standing for 10 minutes, and the slurry interface is from the bottom of the precipitation section 5 made of transparent vinyl chloride. The height to the interface was visually measured. The specifications and operating conditions of the experimental apparatus are shown in FIG.

  Raw water 17 is artificial raw water obtained by adding kaolin to tap water, and the turbidity was adjusted to 3 degrees. As the inorganic flocculant 18, PAC (polyaluminum chloride) was used. As the solid particles, sand having a particle size of 105 μm or less and 97% by weight is used. The solid particle addition rate adjustment and the slurry discharge amount adjustment are carried out based on FIG. 2 and FIG. 3, the SV reference value is set at 20% after standing for 10 minutes, and the reference value of the position of the slurry interface 23 is set at the bottom of the precipitation part 5 The height was 1.0 m. Here, the addition rate means the ratio of the addition amount to the raw water flow rate, and the addition rate of solid particles and the addition rate of PCA are the same.

As shown in FIG. 6, the specifications of the experimental apparatus are as follows: the volume of the coagulation tank 35 composed of the agitating unit 3 and the water channel unit 4: 5.1 L, the volume of the flock forming unit 5 a: 1.5 L, and the settling unit (sedimentation basin) 5. The volume is 120 mm (diameter φ) × 1500 mm (height H). The raw water 17 is made of artificial raw water obtained by adding kaolin (white ceramic with SiO ₂ and Al ₂ O ₃ as main components) to tap water, and PAC (polyaluminum chloride) is used as the inorganic flocculant. Operating conditions are: raw water flow rate: 509 mL / min, ascending flow rate of sedimentation section 5: 50 mm / min, slurry return flow rate: 509 mL / min, raw water turbidity: 3 degrees, PAC addition rate: 20 mg / L, reference value is SV Value: 20% after standing for 10 minutes, slurry interface position: height from the bottom of the precipitation part 5 was 1.0 m.

  The experimental results are shown in FIG. Here, the change in the SV value and the change in the interface position were compared with the values in the time passage column at the start of the test, 1 hour, 2 hours, 3 hours, 4 hours, and 15 minutes later. It is a change of time. As shown in FIG. 7, “comparison of SV value with reference value”, which is a judgment criterion at the start of the test, is “excess (22%)”, “change in SV value” is “increase”, and “interface position is a reference value” “Comparison with” is “less than (0.9 m)”, “Change in interface position” is “Rise”, and “Sand addition rate (mg / L)” corresponding to this criterion is “None” before and after. “The amount of waste mud (mL) / min” is “4 mL / min” both before and after, and “Precipitation water turbidity (degree)” is “0.8 degrees”.

  “Compare SV value with reference value”, which is a criterion after 1 hour, is “excess (24%)”, “change in SV value” is “increase”, and “comparison of interface position with reference value” is “excess ( 1.3 m) ”and“ change in interface position ”are“ rise ”, and“ sand addition rate (mg / L) ”corresponding to this criterion is“ none ”before progress and“ 7 ”after progress. "And" mud amount (mL) / min "are" 4 "before and after the passage, and" precipitation water turbidity (degree) "is" 0.7 ".

  2 hours later, “Compare SV value with reference value” is “excess (22%)”, “Change in SV value” is “decrease”, “Compare interface position with reference value” is “exceed ( 1.1 m) ”and“ change in interface position ”are“ decrease ”, and“ sand addition rate (mg / L) ”corresponding to this criterion is“ 7 ” "mL) / min" is "4" before and after the passage, and "precipitation water turbidity (degree)" is "0.7".

  3 hours later, “Compare SV value with reference value” is “Exceed (21%)”, “Change in SV value” is “Decrease”, “Compare interface position with reference value” is “Exceed ( 0.8 m) ”and“ change in interface position ”are“ decrease ”, and“ sand addition rate (mg / L) ”corresponding to this criterion is“ 7 ”and“ sludge amount ( “mL) / min” is “3” after the lapse of “4” and “0.8” for the “precipitation water turbidity (degree)”.

  “Comparison of SV value with reference value” as a criterion after 4 hours is “below (19%)”, “Change in SV value” is “decrease”, and “Compare interface position with reference value” is “below ( 0.7 m) ”and“ change in interface position ”are“ rise ”, and“ sand addition rate (mg / L) ”corresponding to this judgment criterion is“ 7 ” “mL) / min” is “3” before and after the passage, and “precipitation water turbidity (degree)” is “0.7”.

[Comparative Example 1]
As a comparative example, the result of controlling the sand addition rate and the slurry drainage amount by the processing flow shown in FIG. 8, that is, controlling the sand addition rate and the slurry drainage amount based only on the SV value and not based on the slurry interface. As shown in FIG. The experimental apparatus and operating conditions are the same as those shown in FIGS. In the processing flow of FIG. 8, first, in step ST21, the SV value is compared with the reference value. If it is below the reference, the process proceeds to step ST22, and if it exceeds the standard, the process proceeds to step ST23. In step ST22, it is evaluated whether or not there is a change in the SV value. If the SV value is decreased or maintained, the solid particle addition rate SA and the slurry discharge amount SL are both reduced (↓). Both the solid particle addition rate SA and the slurry discharge amount SL are maintained as they are (→). In step ST23, it is evaluated whether or not there is a change in the SV value. If the SV value is decreased or maintained, both the solid particle addition rate SA and the slurry discharge amount SL are maintained at the current state (→). The solid particle addition rate SA and the slurry discharge amount SL are both increased (↑).

  In FIG. 9, the change of the SV value (SV measurement value) indicates the time in the time passage column (at the start of the test, 1 hour, 2 hours, 3 hours, 4 hours) and the SV value 15 minutes later. This is a change when compared. As in the above experimental example, the test was started from the condition of no sand added and the amount of sludge 4 (mL / min), and the addition of sand and the amount of mud were handled based on the SV value and the change thereof. At the start, the SV value already exceeded the reference value of 20%, and the change in the SV value was “increase”, so both the sand addition rate and the amount of mud were increased (sand addition rate: “None” → “7 (7 mg / L), amount of discharged mud“ 4 (mL / min) → “5 (mL / min)”). After changing the sand addition rate to “7 → 4 (mg / L)” and the amount of mud from “5 → 4 mL / min” based on the SV value after 1 hour, the SV value gradually increases below the reference value. (After 2 hours, “Increased at (18%)”, After 3 hours, “Below (Increased at (20)%”, After 4 hours, “Increased at (Over) (22%))”

  The water content for precipitation after 4 hours deteriorated to “4.2 (degrees)”. This is because the slurry overflowed due to the rise of the slurry interface 23. After the adjustment of the sand addition rate and the amount of mud after 1 hour, the slurry interface position continues to increase and continues to rise. However, since the slurry interface position cannot be determined from the SV value, Both the rate of addition and the amount of mud cannot be properly controlled.

[Comparative Example 2]
As a comparative example, the result of controlling the sand addition rate and the slurry discharge amount by the processing flow shown in FIG. 10, that is, controlling the sand addition rate and the slurry discharge amount based only on the slurry interface position and not based on the SV value. Is shown in FIG. The experimental apparatus and operating conditions are the same as those shown in FIGS. In the processing flow of FIG. 10, first, in step ST31, the interface position is compared with a reference value. If the interface position is below the reference, the process proceeds to step ST32. In step ST32, it is evaluated whether or not there is a change in the interface position. If the interface position is lowered or maintained, both the solid particle addition rate SA and the slurry discharge amount SL are reduced (↓). Both the solid particle addition rate SA and the slurry discharge amount SL are maintained as they are (→). In step ST33, it is evaluated whether or not there is a change in the interface position. If the interface position is lowered or maintained, both the solid particle addition rate SA and the slurry discharge amount SL are maintained (→). The solid particle addition rate SA and the slurry discharge amount SL are both increased (↑).

  In FIG. 11, the change in the interface position is the time when the time in the time passage column (at the start of the test, 1 hour, 2 hours, 3 hours, 4 hours) and the slurry interface position after 15 minutes are compared. The test was started from the condition of no addition of sand and the amount of sludge discharged 4 (mL / min), and the addition of sand and the amount of sludge was handled based on the slurry interface position and the change. The comparison between the interface position at the start of the test and the reference value is “below (0.9 m)”, the change in the interface position is “increased”, the sand addition rate is “no” before and after, and the amount of mud is “4 (mL / Min)).

  As shown in FIG. 11, the comparison of the interface position after 1 hour with the reference value is “exceeded (1.3 m)”, the change in the interface position is “increased”, and the sand addition rate is “None” → elapsed After that, it increased to “7 (mg / L)”, and the amount of mud was increased from “4 (mL / min)” before lapse to “5 (mL / min)” after lapse. The comparison of the interface position after 2 hours with the reference value is “below (1.0 m)”, the change of the interface position is “decreased”, and the sand addition rate is “7 (mg / L)” before the progress → 4 (mg / L) ”, and the amount of mud was reduced from“ 5 (mL / min) ”before the lapse to“ 4 (mL / min) ”after the lapse. The comparison of the interface position after 3 hours with the reference value is “excess (1.3 m)”, the change of the interface position is “increased”, and the sand addition rate is “4 (mg / L)” before the progress → 7 (mg / L) ”, and the amount of mud was increased from“ 4 (mL / min) ”before the lapse to“ 5 (mL / min) ”after the lapse. After 4 hours, the disappearance of the interface and the sand addition rate decreased from “7 (mg / L)” to “None” before the lapse, and the amount of mud was “5 (mL / min)” before the lapse to “4” after the lapse. (ML / min) ".

  Until 3 hours later, the slurry blanket 22 was present in the settling portion 5 and the slurry interface 23 could be confirmed, but after 4 hours, the slurry blanket 22 and the slurry interface 23 disappeared. This is because, after 3 hours, both the amount of added sand and the amount of mud were increased based on the interface conditions. Since the slurry contained sand excessively and the sedimentation property was improved too much, the slurry blanket 22 contracted and the amount of mud was increased. Therefore, most of the contracted slurry was discharged to the bottom of the sedimentation section 5. Oops. If the settling property of the slurry is good, it is not necessary to increase the rate of sand addition, and the increase in the slurry interface 23 should be dealt with by increasing the amount of mud. However, since the sedimentation property of the slurry cannot be determined from the position of the slurry interface, it can be adjusted based only on the position of the slurry interface, and appropriate control of both the sand addition rate and the amount of mud cannot be performed.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea described in the claims and the specification and drawings. Is possible.

It is a figure which shows schematic structure of the slurry circulation type coagulation sedimentation processing apparatus which concerns on this invention. It is a figure which shows the processing flow of the slurry circulation type coagulation sedimentation processing apparatus which concerns on this invention. It is a figure which shows the processing flow of the slurry circulation type coagulation sedimentation processing apparatus which concerns on this invention. It is a figure which shows the structural example of the control means of the slurry circulation type coagulation sedimentation processing apparatus which concerns on this invention. It is a figure which shows the schematic structural example of an experimental apparatus. It is a figure which shows the specification of an experimental apparatus, an operating condition, and a reference value. It is a figure which shows an experimental result. 10 is a diagram showing a processing flow of Comparative Example 1. FIG. It is a figure which shows the comparative example 1. It is a figure which shows the processing flow of the comparative example 2. FIG. It is a figure which shows the comparative example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Landing well 2 Slurry circulation type coagulation sedimentation processing tank 3 Stirring part 4 Water channel part 5 Precipitation part (sedimentation tank)
6 Stirrer blade 7 Stirrer motor 8 Catchment tank 9 Treated water discharge pipe 10 Slurry discharge pipe 11 Sludge pump 12 Solid particle addition pump 13 Solid particle supply pipe 14 pH meter 15 SV meter 16 Slurry interface meter 17 Raw water 18 Inorganic flocculant 19 Turbidimeter 20 Flow meter 21 Raw water introduction pipe 22 Slurry blanket 23 Slurry interface 24 Slurry circulation pump 32 Control means 33 Inorganic flocculant addition mechanism 34 pH adjustment mechanism 35 Coagulation tank

Claims (4)

A stirring unit that stirs the raw water and the inorganic flocculant to form a slurry, and a slurry blanket that is provided through the stirring unit and the water channel unit and purifies the slurry introduced from the water channel unit is formed below and In a slurry circulation type coagulation sedimentation treatment apparatus provided with a sedimentation part for forming a treated water layer above the slurry blanket and a flow path for returning the slurry to the stirring part from below the sedimentation part,
Solid particle supply means for supplying solid particles for increasing the specific gravity of the slurry to the raw water;
An SV meter for detecting the SV value of the slurry guided to the settling portion;
A slurry interface meter for detecting the position of the slurry interface of the slurry blanket formed in the settling portion;
Slurry discharging means for discharging the slurry below the slurry blanket from the bottom of the settling section or the bottom of the stirring section;
Storing the SV value detected by the SV meter and the position of the slurry interface detected by the slurry interface meter;
Using the SV value detected by the SV meter as the current SV value, the time change of the SV value is calculated from the current SV value and the stored SV value, and the position of the slurry interface detected by the slurry interface meter is The time change of the position of the slurry interface is calculated from the position of the current slurry interface and the stored position of the slurry interface as the position of the slurry interface,
Whether to increase or decrease the amount of solid particles added and the amount of slurry discharged, respectively, based on the SV measured value by the SV meter and its time change, and the measurement position and time change of the slurry interface by the slurry interface meter. It is determined whether the current state is to be maintained, the solid particle supply means and the slurry discharge means are controlled, the addition rate of the solid particles is appropriately adjusted without excess and deficiency, and the position of the slurry interface is maintained at a predetermined position. A slurry circulation type coagulation sedimentation processing apparatus, characterized in that a control means for adjusting so as to be provided is provided. A stirring unit that stirs the raw water and the inorganic flocculant to form a slurry, and a slurry blanket that is provided through the stirring unit and the water channel unit and purifies the slurry introduced from the water channel unit is formed below and In the operating method of the slurry circulation type coagulation sedimentation treatment apparatus provided with a sedimentation part for forming a treated water layer above the slurry blanket and a flow path for returning the slurry to the stirring part from below the sedimentation part,
The SV value of the slurry guided from the stirring unit to the settling unit through the water channel unit is measured with an SV meter at predetermined time intervals, and the position of the slurry interface of the slurry blanket formed in the settling unit is set with the slurry interface meter. Measured at time intervals, and calculated from the measured SV value and time interval and the position and time interval of the measured slurry interface, the time change of the SV value and the time change of the position of the slurry interface,
Based on the SV value and the time change of the SV value, and the time change of the position of the slurry interface and the position of the slurry interface, whether the amount of solid particles added and the amount of slurry discharged are increased or decreased, respectively, are maintained. determining whether the to, by adjusting the supply amount and the slurry discharge amount that will be discharged by the slurry discharge means of the solid particles that will be supplied in a solid particle supply means, appropriately adjusting the addition rate of the solid particles just enough In addition, an operation method of the slurry circulation type coagulation sedimentation treatment apparatus, wherein the position of the slurry interface is adjusted to be maintained at a predetermined position. In the operation method of the slurry circulation type coagulation sedimentation processing device according to claim 2 ,
The solid particles for increasing the specific gravity of the slurry are particles mainly composed of SiO ₂ . In the operation method of the slurry circulation type coagulation sedimentation processing device according to claim 2 ,
The solid particles that increase the specific gravity of the slurry are powdered activated carbon.

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