JP2008246358A - Method and apparatus for controlling residence time in flocculation tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for controlling residence time in a flocculation tank which can adjust a flocculation time period in a flocculation tank to the optimum residence time in the tank while maintaining the amount of raw sludge supplied to the flocculation tank at a constant level against a change in the concentration of supplied raw sludge. <P>SOLUTION: The optimum residence time in the flocculation tank 55 corresponding to the concentration of raw sludge flowing into the tank is obtained from correlation between the optimum residence time in the tank required for flocculation, determined by the properties of raw sludge, and the concentration of raw sludge. The optimum total flow rate flowing into the flocculation tank 55 is determined from correlation between a total flow rate flowing into the tank and a residence time in the tank. The total flow rate flowing into the tank comprising a coagulant, adjustment water, and raw sludge is adjusted to the optimum total flow rate flowing into the tank by operation of increasing or decreasing the flow rate of the adjustment water poured into the flocculation tank 55 to control the residence time in the tank at the optimum residence time in the tank. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for adjusting the residence time in a coagulation tank, and particularly relates to a technique for stabilizing the concentration of sludge in a belt concentrator.

  Conventionally, an example of this type of concentrator is shown in FIG. This is a gravity dewatering belt type concentrator 1, which has an endless belt 4 spanned between a driving sprocket 2 at the end and a driven sprocket 3 at the starting end, and an upper forward path between both sprockets 2, 3. The track and the lower return track are formed.

  A plurality of carrier rollers 5 are arranged on the outward path, a return pulley 6 is arranged on the return path, and cleaning water is sprayed from the back surface to the front surface or from the front surface to the back surface of the endless belt 4. A nozzle 7 is arranged. A shooter 8 for discharging concentrated sludge is disposed at the end of the track.

  Or there exists a thing shown in FIG. 6, for example as a dehydrator. This is a belt press type dehydrator 11 which is provided between a plurality of rolls 12 and provided with a pair of upper and lower belt-like filter cloth belts 13 in an endless manner. A rotary mixer 16 is provided above the belt press type dehydrator 11 to supply the sludge 14 mixed with the flocculant 15.

The belt press type dehydrator 11 is formed with a compression dewatering zone and a shear dewatering zone, and a cake thickness adjusting roll 17 is provided at a position in front of the compression dewatering zone.
The sludge 18 mixed with the flocculant 15 by the rotary mixer 16 is supplied between the filter cloth belts 13, and the soot pressure and the surface pressure by the rolls 12 while the filter cloth belt 13 moves between the plurality of rolls 12. And dehydrated. The detachment liquid 19 separated from the sludge 18 between the filter cloths 13 under the pressure and surface pressure by the roll 12 falls from the filter cloths 13 by its own weight.

A level sensor 20 is disposed as a sludge thickness measuring means at a position in front of the cake thickness adjusting roll 17, and the level sensor 20 measures the sludge thickness on the spreading belt 13. The arithmetic unit 21 controls the operation of the dehydrator and the sludge refining work in the previous process, and the chemical injection amount for sludge refining in the previous process and the stirring strength in the coagulation tank in the previous process. Various operating conditions such as the rotation speed of the stirrer that regulates the amount of feed, the amount of mud supplied to the dehydrator, and the traveling speed of the filter cloth that defines the residence time of the cake in the dewatering section are changed.
JP 2004-24963 A JP-A-9-19607

  By the way, in the above-described concentrators and the like, generally, the sludge is tempered by a coagulation apparatus (the rotary mixer or the like described above) as a pre-process of the concentrating step, and the tempered sludge is concentrated or dehydrated. To supply. In this flocculation apparatus, raw sludge supplied from a sludge supply source is received in a flocculation tank, and a fixed amount of flocculating agent is injected in proportion to the sludge concentration of the original sludge or regardless of the sludge concentration, and stirred with a stirrer. The sludge is tempered.

  When such a floc is formed by adding a flocculant to sludge and the condensed floc is filtered and concentrated to obtain concentrated sludge, the concentration performance varies greatly depending on the formation state of the aggregated floc. In order to form an agglomeration floc, the sludge and the aggregating agent are agitated and mixed as described above, but there is an optimum value for each sludge property in this agitation time, that is, the residence time required in the agglomeration tank. It has been known.

  That is, if the residence time in the tank is too short, the formation of aggregated floc is insufficient and the concentration performance is lowered. On the contrary, if the residence time in the tank is too long, the floc flocs once formed are disassembled and refined, and the concentrating performance is lowered. Therefore, in order to obtain stable concentration performance, it is important to stir and mix the sludge and the flocculant with the optimum residence time in the tank according to the sludge properties.

  However, in the conventional flocculation equipment, even if the supply sludge concentration of the raw sludge changes during operation, the residence time in the tank in the flocculation tank is constant, so if the supply sludge concentration of the raw sludge increases , The residence time in the tank becomes excessive with respect to the optimum residence time in the tank necessary for the coagulation action of the coagulant to work properly, and the aggregated floc formed by the coagulation action of the coagulant is disassembled and refined by stirring. There was a situation where the tendency became stronger and the concentration of sludge in the concentration process deteriorated.

  Conversely, when the supply sludge concentration of the raw sludge becomes low, the dwell time in the tank is insufficient with respect to the optimum dwell time in the tank necessary for the aggregating action of the flocculant to work sufficiently, and the aggregate floc is sufficient. The tendency for the conditioned sludge to flow out of the coagulation tank before the formation of the sludge increased, and there was a situation where the concentration of sludge in the concentration process deteriorated.

  By the way, the flocculation tank has a constant tank capacity, and a surplus exceeding the tank capacity flows over the weir and flows out, so if the amount of raw sludge flowing into the flocculation tank increases, the amount of discharge naturally increases. As a result, the residence time in the tank is reduced. Conversely, if the amount of raw sludge flowing into the flocculation tank decreases, the discharge amount inevitably decreases, and as a result, the residence time in the tank increases.

  For this reason, when the supply sludge concentration of the raw sludge increases, the supply amount of the raw sludge supplied to the coagulation tank is increased to reduce the residence time in the tank, and the supply sludge concentration of the raw sludge is reduced It is possible to adjust the residence time in the tank according to the supply sludge concentration of the raw sludge by decreasing the supply amount of the raw sludge supplied to the coagulation tank and increasing the residence time in the tank.

  However, if the supply amount of raw sludge is increased or decreased, the treatment amount of raw sludge per unit time is increased or decreased, and the stability of operation efficiency is hindered, and the operation required to process the total amount of raw sludge supplied in a given period. Time changes and the stability of the device operating efficiency is hindered.

  The present invention solves the above-mentioned problem, and the coagulation time in the coagulation tank is optimal while maintaining the supply amount of the raw sludge supplied to the coagulation tank constant with respect to the change in the supply sludge concentration of the raw sludge. It is an object of the present invention to provide a method and an apparatus for adjusting the residence time in a coagulation tank that realizes adjustment control to the internal residence time.

  In order to solve the above problems, the method for adjusting the residence time in the flocculation tank of the present invention is to supply raw sludge to the flocculation tank, add a flocculant to the flocculation tank or the raw sludge flowing into the flocculation tank, and In the agglomeration process, the adjustment water is poured into the tank and agitated, and the conditioned sludge containing agglomerated floc is supplied to the concentration process or dehydration process. The optimum residence time in the tank corresponding to the sludge concentration of the raw sludge flowing into the coagulation tank is obtained by correlation with the sludge concentration, and the optimum residence in the tank is obtained by correlation between the total inflow volume in the aggregation tank and the residence time in the tank. The optimal total inflow flow rate in the tank corresponding to the time is obtained, and the total inflow rate in the tank consisting of the coagulant, adjustment water, and raw sludge is changed to the optimal total inflow rate in the tank by adjusting the flow rate of the adjustment water injected into the coagulation tank. Adjust to stay in tank And controlling the optimum tank residence time between.

In addition, as adjustment water, washing waste water in the concentration step or dehydration step, or a filtrate in the concentration step or a desorption liquid in the dehydration step is injected.
The apparatus for adjusting the residence time in the flocculation tank of the present invention comprises a flocculation tank that receives and stirs raw sludge, and a flocculant supply system that adds a flocculant to the flocculation tank or the raw sludge that flows into the coagulation tank. In a flocculation device that supplies tempered sludge containing floc to the concentration process or dewatering process, a sludge concentration measuring means for measuring the sludge concentration of the raw sludge flowing into the flocculation tank, and an adjustment water supply system for pouring adjustment water into the flocculation tank A flow rate control means for increasing or decreasing the flow rate of the adjustment water, a flow rate measuring means for measuring the total flow rate of the inflow in the coagulation tank, and a control means. The optimal residence time in the tank corresponding to the sludge concentration measured by the sludge concentration measuring means is obtained by correlating the optimum residence time in the tank required for coagulation determined by the sludge and the sludge concentration in the raw sludge. The optimal inflow total flow rate in the tank corresponding to the optimal retention time in the tank is obtained by the correlation between the inflow time and the inflow time in the tank, and the total inflow rate in the tank measured by the inflow total amount measuring means matches the optimal total inflow rate in the tank. In addition, the water flow rate of the adjustment water is increased or decreased by the water flow rate operation means to control the residence time in the tank to the optimum residence time in the tank.

  Further, the adjustment water supply system is characterized by injecting the washing waste water in the concentration step or the dehydration step or the filtrate in the concentration step or the desorbed liquid in the dehydration step as the adjustment water.

In the present invention described above, attention is paid to the fact that the properties of the tempered sludge supplied to the concentration process and the dehydration process through the aggregation process have already been determined at the aggregation process.
In other words, raw sludge with a high sludge concentration flowing into the agglomeration process through a sedimentation process performed during water treatment such as biological treatment or anaerobic digestion treatment is originally a sludge with a property of excellent sedimentation. Sludge with excellent properties does not change the properties of the sludge particles themselves depending on the sludge concentration at the time of flocculation, but tends to shorten the optimum residence time in the tank necessary to form sufficient flocculation flocs at the time of flocculation Indicates. Conversely, the raw sludge having a low sludge concentration at the stage of entering the agglomeration process is originally sludge with a property that is inferior in sedimentation, and sludge having such a property inferior in sedimentation is sludge particles depending on the sludge concentration at the time of agglomeration. The properties of itself do not change, and it shows a tendency that the optimum residence time in the tank necessary to form a sufficient aggregate floc during aggregation is increased.

  Since the optimum residence time in the tank is determined by the original sludge properties, the apparent amount of raw sludge containing the flocculant and the adjustment water in the coagulation tank changes by increasing or decreasing the flow rate of the adjustment water to the coagulation tank. Even if changes in the raw sludge concentration are observed as a phenomenon, the optimal residence time in the tank does not change.

  As an example of a method for determining the optimum residence time in the tank, the gravity filtration performance of the coagulated sludge formed by the beaker test, for example, the amount of filtrate per unit time, while changing the stirring time (equivalent to the residence time in the tank) It can be obtained by evaluating. However, it is difficult to obtain the optimal residence time in the tank in real time.

  By the way, as described above, the raw sludge having a high sludge concentration is originally a sludge having a property excellent in settling property, and shows a tendency that the optimum residence time in the tank is shortened. Conversely, the raw sludge having a low sludge concentration is The sludge is originally inferior in sedimentation property and tends to have a longer optimum residence time in the tank, and there is a correlation between the optimum residence time in the tank and the sludge concentration of the raw sludge.

  Therefore, by sampling raw sludges with different sludge concentrations in advance and calculating the optimum residence time in the tank by a beaker test etc. for each sludge concentration, the correlation equation or correlation curve between the optimum residence time and sludge concentration is obtained. In this correlation, the optimum residence time in the tank can be obtained in real time using the sludge concentration of the raw sludge as an index.

  On the other hand, the residence time of the raw sludge in the coagulation tank is determined by the total inflow amount in the tank, which is composed of the supply amount of the coagulant, the flow rate of the adjustment water, and the inflow amount of the raw sludge. The tank capacity of the agglomeration tank is constant, and as the total inflow rate in the tank increases, the overflow rate increases.As a result, the residence time of the raw sludge in the tank decreases, and as the total inflow rate in the tank decreases, the overflow rate decreases. As a result, the residence time of the raw sludge in the tank becomes longer. Since the inflow amount of raw sludge is basically constant, the total inflow rate in the tank increases or decreases as the adjustment water increases or decreases.

  For this reason, by increasing or decreasing the flow rate of the adjustment water to the flocculation tank to increase or decrease the apparent amount of raw sludge in the flocculation tank and adjusting the residence time in the tank, the optimal tank according to the sludge properties in the flocculation tank Internal residence time can be realized.

  In addition, when water for adjustment is used as washing water in the concentration process or dehydration process, or the filtrate in the concentration process or the desorbed liquid in the dehydration process, the adjustment water has properties similar to the raw sludge and the excess flocculant component Can be effectively utilized, so that a high aggregation effect can be obtained.

  In the present invention, the concentration process or the dehydration process can be operated without increasing or decreasing the supply amount of the raw sludge, and the tempering is performed with the optimum residence time in the tank supplied from the coagulation tank to the concentration process or the dehydration process. Sludge increases with the amount of raw sludge supplied with the adjustment water and becomes lower than the sludge concentration of the original sludge, but the solid load is almost the same as when the raw sludge is treated alone without water injection. Therefore, it is not necessary to change the belt running speed in the concentration process or the dehydration process, and the filtration time does not change, so that the original concentration performance in the concentration process or the dehydration process is not deteriorated, but rather a good aggregation floc is formed. Realization improves the concentration performance.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment mode, a concentrator is described, but the present invention can also be applied to a dehydrator.
As shown in FIG. 1, a gravity dewatering belt type concentrator 51 has an endless belt 54 spanned between a drive sprocket 52 at the end and a driven sprocket 53 at the start, and between both sprockets 52 and 53. The upper outgoing track and the lower returning track are formed.

  The agglomeration tank 55 is disposed at the starting end of the forward path, and a plurality of carrier rollers or plate-like support members are disposed in the middle of the forward path. From the back surface of the return path of the endless belt 54 to the return path. A cleaning nozzle 56 that injects cleaning water toward the front surface (possible from the front surface to the back surface) is arranged.

  A filtrate receiving part 57 is disposed below the forward path of the endless belt 54, and the filtrate receiving part 57 communicates with the filtrate storage tank 59 via a filtrate collecting pipe 58. The filtrate storage tank 59 communicates with the washing nozzle 56 via the washing water pipe 60 and the washing water pump 61 and also communicates with the drain pipe 62.

  A cleaning drainage receiving part 63 is disposed below the return path of the endless belt 54, and the cleaning drainage receiving part 63 communicates with the cleaning drainage storage tank 65 via the cleaning drainage collecting pipe 64. The washing drainage storage tank 65 communicates with the aggregation tank 55 via the adjustment water pipe 66.

  The agglomeration tank 55a receives raw sludge, tempers it, and supplies the conditioned sludge containing the agglomerated floc onto the forward path of the endless belt 54, and includes a stirrer (not shown). The agglomeration tank 55a has an open tank structure with an overflow dam, and the overflow rate increases and decreases as the total inflow rate in the tank increases and decreases.

  The raw sludge supply system 68 for quantitatively supplying raw sludge to the coagulation tank 55a has an inverter control pump 68a and a flow meter 68b. The raw sludge supply system 68 determines the coagulant in the raw sludge supplied to the coagulation tank 55a. A coagulant supply system 69 to be supplied is connected, and the coagulant supply system 69 has an inverter control pump 69a and a flow meter 69b.

  The raw sludge supply system 68 and the flocculant supply system 69 may be configured to supply the raw sludge or the flocculant so that the flow rate can be adjusted by adjusting the opening of a valve (not shown). The raw sludge supply system 68 is provided with a sludge concentration meter 70 as sludge concentration measuring means for measuring the sludge concentration of the raw sludge. The coagulant supply system 69 may be connected to the coagulation tank 55.

  An adjustment water pipe 66 forming an adjustment water supply system for injecting adjustment water into the coagulation tank 55a includes an inverter control pump 71a and a flow meter 71b as injection water flow operation means for increasing and decreasing the injection water flow rate of adjustment water to the aggregation tank 55. Provided. It is also possible to adjust the opening of a valve (not shown) instead of the flow rate control by the inverter control pump 71a. The adjustment water pipe 66 may be an external water supply pipe that supplies external water.

  The tank capacity up to the weir height of the coagulation tank 55a is constant, and when the flow rate of the adjustment water is increased while supplying the raw sludge and the coagulant in a fixed quantity, the tank consisting of the raw sludge amount, the adjustment water amount and the coagulant amount The total inflow rate of the inflow increases, the supply amount of the conditioned sludge that flows over from the coagulation tank 55 increases, and the supply amount of the conditioned sludge becomes equal to the total inflow rate in the tank.

  The inflow total amount measuring means for measuring the inflow total flow rate in the flocculation tank 55a is set in the control device 73, and the flow rate of the adjustment water is measured by the flow meter 71b while supplying the raw sludge and the flocculant quantitatively. By adding the measured value of the water injection flow rate, the amount of raw sludge to be supplied quantitatively, and the amount of coagulant, the total inflow rate in the tank is obtained. The inflow total amount measuring means can be realized by providing a water level meter in the coagulation tank 55a.

  The control device 73 obtains the optimum retention time in the tank corresponding to the sludge concentration measured by the sludge concentration meter 70 by correlating the optimum retention time in the tank necessary for agglomeration determined by the properties of the raw sludge and the sludge concentration in the raw sludge. The optimum total inflow rate in the tank corresponding to the optimum residence time is obtained from the correlation between the total inflow rate in the tank and the residence time in the aggregation tank 55a.

  Then, while supplying the raw sludge and the flocculant in a fixed amount, the flow rate of the adjustment water is measured by the flow meter 71b, and the measured value of the injected water flow rate is added to the amount of raw sludge and the amount of flocculant to be supplied in the tank. Obtain the total inflow flow rate, obtain the adjustment water injection flow rate necessary for the total inflow flow rate in the tank to match the optimal inflow total flow rate, and control the inverter control pump 71a to increase or decrease the adjustment water injection flow rate. The tank residence time is controlled to the optimum tank residence time. Here, the supply amount of the flocculant can be increased or decreased depending on the sludge concentration of the raw sludge.

  The optimum residence time in the tank will be described below. The raw sludge having a high sludge concentration at the stage of flowing into the agglomeration tank 55a is originally a sludge having a property excellent in sedimentation, and the sludge having such a property excellent in sedimentation is sludge particles depending on the sludge concentration at the time of aggregation. The properties of the tank itself do not change, and the optimum residence time in the tank, that is, the residence time in the tank that is necessary to form a sufficient flocs flocs during agglomeration and the stirring action is not excessive depends on the sludge properties of the raw sludge. As a result, the optimum residence time of the sludge having the above-described property of excellent sedimentation tends to be shortened.

  On the contrary, the raw sludge having a low sludge concentration at the stage of flowing into the flocculation tank 55a is a sludge having a property that is originally inferior in sedimentation property. The properties of the particles themselves do not change, and the optimum residence time tends to be longer.

  For this reason, in the stage of flowing into the agglomeration tank 55a, the sludge having a property that is originally excellent in sedimentation naturally has a high sludge concentration, while the sludge having a property that is originally inferior in sedimentation naturally has a low sludge concentration. Therefore, it is possible to estimate the properties of sludge from the sludge concentration.

  Therefore, once the correlation between the optimum tank residence time, which is mainly defined by the sludge properties, and the sludge concentration of the raw sludge is determined, the optimum residence time in the tank can be obtained in real time using the sludge concentration of the raw sludge as an index. Can do. The apparent sludge concentration in the coagulation tank changes with water injection, but the properties of the sludge particles themselves do not change, so the optimal residence time in the tank is maintained at a value determined by the raw sludge concentration (properties). Is done.

  For this reason, as an example, the raw sludge having different sludge concentrations is subjected to a beaker test in advance, and the gravity filtration performance of the sample coagulated sludge, for example, the amount of filtrate per unit time, while changing the stirring time (equivalent to the residence time in the tank) It is determined by evaluation, and a correlation formula or correlation curve between the optimal tank residence time and sludge concentration is determined.

  FIG. 4 is a graph showing the correlation between the optimum residence time in the tank and the sludge concentration. As shown in FIG. 4, the test result mentioned above is plotted and the optimal residence time curve (correlation curve) is obtained. In the optimum tank residence time curve, the higher the raw sludge concentration, the shorter the optimum tank residence time, and the lower the raw sludge concentration, the longer the optimum tank residence time.

By the way, the residence time of the raw sludge in the coagulation tank 55 is determined by the total inflow amount in the tank composed of the supply amount of the coagulant, the flow rate of the adjustment water, and the inflow amount of the raw sludge.
Tank retention time = tank capacity / total inflow in the tank Here, the tank capacity up to the weir height of the coagulation tank 55a is constant, and as the total inflow in the tank increases, the overflow increases, and as a result, the raw sludge If the residence time in the tank is shortened and the total inflow rate in the tank is reduced, the overflow rate is reduced, and as a result, the residence time of the raw sludge is increased.

For this reason, at the time of designing the coagulation tank 55a, in the optimal tank residence time curve, the tank residence time at the minimum concentration C _MIN of the raw sludge to be set is obtained as the longest tank residence time T _MAX and the maximum concentration C _MAX is obtained. seeking residence time vessel shortest tank residence time _{T MIN,} the bath of the longest vessel residence time _{T MAX} and the shortest tank residence time _{T MIN} satisfies flocculation tank 55a tank capacity and maximum tank residence time of _{T MAX} The minimum amount of the total inflow in the tank and the maximum amount of the total inflow in the tank of the shortest tank residence time _TMIN are determined.

  When supplying raw sludge in a fixed quantity, the total inflow rate in the tank changes only by adjusting the amount of adjustment water, so the minimum flow rate of adjustment water that matches the minimum total inflow volume in the tank and the total inflow volume in the tank The maximum water injection flow rate corresponding to the maximum amount is determined, and the correlation between the optimum residence time in each sludge concentration of raw sludge and the water injection flow rate of adjustment water is determined. It is also possible to control so that the adjustment water is not supplied by setting the minimum water injection flow rate to zero. When the amount of raw sludge inflow changes, the ratio of the amount of raw sludge to the water flow rate for adjustment water is determined within the total inflow rate in the tank.

Then, determine the optimum tank residence time T _D in the design sludge concentration C _D, determining the design water injection flow design tank inflow total flow and adjust water meeting the optimum tank residence time T _D.
With the above-described configuration, during operation, raw sludge is quantitatively supplied from the raw sludge supply system 68 to the coagulation tank 55a, the sludge concentration of the raw sludge is measured by the sludge concentration meter 70, and a predetermined amount of the flocculant is supplied from the coagulant supply system 69. Is supplied to the raw sludge supply system 68, and a predetermined amount of adjustment water supplied from the adjustment water pipe 66 to the coagulation tank 55a, the raw sludge, and the coagulant are stirred in the coagulation tank 55a and conditioned.

  The control device 73 uses the sludge concentration measured by the sludge concentration meter 70 as an index, the optimum in-tank residence time determined in the optimum in-tank residence time curve, the total inflow amount in the tank corresponding to the optimum in-tank residence time, and the injection water flow rate of adjustment water. Ask for.

If the measured value of the sludge concentration corresponds to the design sludge concentration C _D is providing regulated water to the flocculation tank 55a by water injection flow rate to meet the design water injection flow rate, the optimum tank design time substantially bath residence time of raw sludge controlling the internal dwell time _{T D.} The adjustment water is supplied from the cleaning waste water storage tank 65 through the adjustment water pipe 66 by the inverter control pump 71a.

If the measured value of the sludge concentration is high or when lower than the design sludge concentration C _D is adjusted to the optimum tank residence time determined at the optimal bath residence time curve substantially bath residence time of raw sludge. In order to realize the total inflow amount in the tank corresponding to the optimal in-tank residence time, the rotational speed of the inverter control pump 71a is adjusted to increase or decrease the flow rate of the adjustment water.

  By this operation, the flow rate of the adjustment water to the flocculation tank 55a is increased or decreased to increase or decrease the total flow rate in the tub in the flocculation tank 55a to adjust the residence time in the tub. To achieve the optimal residence time in the tank.

  That is, as shown in FIG. 2, the residence time HRT in the aggregating apparatus in the agglomeration tank 55a does not change even if the raw sludge concentration changes in the prior art, but in this embodiment, the agglomeration occurs as the raw sludge concentration increases. The residence time HRT in the apparatus is shortened, and the residence time HRT in the flocculation apparatus is lengthened as the raw sludge concentration decreases. For this reason, as shown in FIG. 3, the water injection flow rate of adjustment water is increased as the raw sludge concentration increases, and the water injection flow rate of adjustment water is decreased as the raw sludge concentration decreases.

  At this time, even if the apparent raw sludge concentration including the flocculant and the adjustment water in the coagulation tank 55a is changed by increasing / decreasing the flow rate of the adjustment water to the coagulation tank 55a, it is determined by the original sludge properties. The optimal residence time in the tank does not change.

  The conditioned sludge containing the flocculated floc that has been conditioned in the flocculation tank 55a is made to flow over the endless belt 54 on the forward path and is filtered by the endless belt 54 while being transported by the endless belt 54, thereby concentrating the conditioned sludge. The filtrate that has passed through the endless belt 54 flows into the filtrate storage tank 59 through the filtrate receiver 57 and the filtrate collecting pipe 58.

  The filtrate in the filtrate storage tank 59 is supplied to the cleaning nozzle 56 through the cleaning water pipe 60 by the cleaning water pump 61, and sprayed from the back surface to the endless belt 54 of the return path from the back surface to the endless belt 54. Wash away the remaining raw sludge. The cleaning drainage flows into the cleaning drainage storage tank 65 through the cleaning drainage receiving portion 63 and the cleaning drainage collecting pipe 64.

  The washing waste water in the washing waste water storage tank 65 is supplied to the aggregation tank 55a through the adjustment water pipe 66 by the inverter control pump 71a. For this reason, since adjustment water has the property close | similar to raw sludge, and a surplus flocculant component can be used effectively, a higher coagulation effect can be acquired.

  Therefore, in this embodiment, even if the raw sludge concentration changes, the concentration operation can be performed without increasing or decreasing the supply amount of the raw sludge, and the conditioned sludge conditioned by the coagulation tank 55a with the optimal residence time in the tank. Regardless of the flow rate of the adjustment water, the solid load is almost the same as when the raw sludge is treated alone. Therefore, since it is not necessary to change the belt running speed of the endless belt 4 and the filtration time does not change, the original concentration performance of the tempered sludge on the endless belt 4 is not deteriorated. By realizing the above, the aggregation performance is improved.

  As another embodiment of the present invention, when applied to a dehydrator such as a screw press dewaterer or a rotary press dewaterer that is supplied by press-fitting raw sludge, the same effect can be realized even if the valve 72 is provided. .

The schematic diagram which shows the structure of the belt concentrator in embodiment of this invention. The graph which shows the relationship between the raw sludge density | concentration and the HRT in a coagulation apparatus in the same embodiment Graph showing the relationship between raw sludge concentration and water injection flow rate in the same embodiment The graph which shows the relationship between the raw sludge density | concentration and the optimal residence time in the tank in the same embodiment Schematic diagram showing a conventional belt type concentrator Schematic diagram showing a conventional belt press dehydrator

Explanation of symbols

51 Belt type concentrator 52 Drive sprocket 53 Driven sprocket 54 Endless belt 55a, 55b Coagulation tank 56 Washing nozzle 57 Filtrate receiving part 58 Filtrate collecting pipe 59 Filtrate storage tank 60 Washing water pipe 61 Washing water pump 62 Drainage pipe 63 Washing drainage Receiving part 64 Washing drainage collecting pipe 65 Washing drainage storage tank 66 Adjustment water pipe 68 Raw sludge supply system 68a Inverter control pump 68b Flow meter 69 Coagulant supply system 69a Inverter control pump 69b Flow meter 70 Sludge concentration meter 71a Inverter control pump 71b Flow rate 73 control devices

Claims (4)

The raw sludge is supplied to the coagulation tank, the coagulant is added to the coagulation tank or the raw sludge flowing into the coagulation tank, and the adjustment water is poured into the coagulation tank and stirred to concentrate the conditioned sludge containing the coagulation flocs or In the flocculation process to be supplied to the dewatering process, the optimum tank corresponding to the sludge concentration of the raw sludge flowing into the flocculation tank is determined by the correlation between the optimal residence time in the tank required for flocculation determined by the properties of the raw sludge and the sludge concentration of the raw sludge. The internal residence time is obtained, and the correlation between the total flow rate in the tank and the residence time in the coagulation tank is used to obtain the optimal total flow rate in the tank corresponding to the optimal residence time, and water for adjustment is poured into the coagulation tank. Coagulation characterized by adjusting the total flow rate in the tank consisting of flocculant, adjustment water, and raw sludge to the optimal total flow rate in the tank and controlling the residence time in the tank to the optimal residence time When the tank stays in the tank Adjustment method. The method for adjusting the residence time in the coagulation tank according to claim 1, wherein the water for adjustment is injected with washing waste water in the concentration step or dehydration step, or a filtrate in the concentration step or a desorption liquid in the dehydration step. A coagulation tank that receives and stirs the raw sludge, and a coagulant supply system that adds a coagulant to the coagulation tank or the raw sludge that flows into the coagulation tank, and supplies conditioned sludge containing coagulated floc to the concentration or dehydration process In the coagulation device, the sludge concentration measuring means for measuring the sludge concentration of the raw sludge flowing into the coagulation tank, the adjustment water supply system for injecting the adjustment water into the coagulation tank, and the injection flow rate operation for increasing or decreasing the injection flow rate of the adjustment water Means, an inflow total amount measuring means for measuring the total inflow amount in the tank in the coagulation tank, and a control means. The control means has an optimum tank residence time and raw sludge required for coagulation determined by the properties of the raw sludge. The optimum residence time in the tank corresponding to the sludge concentration measured by the sludge concentration measuring means is obtained by correlation with the sludge concentration in the agglomeration tank. The optimal total inflow flow rate in the tank corresponding to the residence time is obtained, and the injection water flow rate control means is used to adjust the injection flow rate of the adjustment water so that the total inflow rate in the tank measured by the total inflow measurement unit matches the optimal total flow rate in the tank. An apparatus for adjusting a residence time in a tank of a coagulation tank, wherein the residence time in the tank is controlled to an optimum residence time by increasing / decreasing operation. 4. The retention time in the coagulation tank according to claim 3, wherein the adjustment water supply system injects the washing waste water in the concentration process or dehydration process, the filtrate in the concentration process or the desorbed liquid in the dehydration process as adjustment water. Adjustment device.

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