JP4516152B1 - Coagulation precipitation treatment method - Google Patents

Abstract

An object of the present invention is to provide a method for coagulating and precipitating water to be treated so that the concentration of particles in a flocking process does not decrease in a sludge / blanket tank.
An inorganic flocculant injecting step, a fine flocking step by operation of a rapid stirring tank, a flocking step in a sludge / blanket tank 5, and a step of precipitating and separating the flocked particles and discharging them to the outside. In the preliminary preliminary experiment, the precipitating method for coagulating and precipitating the treated water 1, wherein the precipitated flocculated particles are returned to the previous stage of the fine flocculation step and injected into the treated water 1. Whether or not the concentration of particles in the flocking process in the sludge / blanket tank 5 is reduced is adjusted and adjusted as a standard. As a convenient standard at the work site, the concentration in the previous stage of the fine flocking process is A method for coagulating and precipitating water to be treated based on the fact that the injection amount can be selected in advance so as to be 7.5 mg / L or more.
[Selection] Figure 1

Description

  The present invention is formed by a micro-floccing process in which an inorganic flocculant is injected into water to be treated such as river water, rain water, factory effluent and the like, and fine suspended particles contained in the water to be treated are agglomerated. A method for coagulating and precipitating water to be treated based on the combination of fine floc particles in a sludge / blanket tank and / or the combination of fine flocs and existing flocs, and the separation of the flocculent particles. About.

The flocculation and precipitation treatment of the water to be treated is employed as a pretreatment for sand filtration. In the flocculation and precipitation method, an inorganic flocculant is injected into the water to be treated, and fine suspended particles contained in the water to be treated. Are aggregated into flocs having a diameter capable of being separated by precipitation, and the flocs are separated by precipitation by the action of gravity.
The coagulation sedimentation apparatus is roughly classified into a conventional system and a high-speed coagulation sedimentation basin system. The latter is further classified into a slurry circulation system and a sludge blanket system, and the present invention selects the latter.
However, in any of the methods, the precipitate is separated through the fine flocking step of the suspended particles and the fine flocking step.

The current coagulation-precipitation treatment method is based on the following general formula shown by Smolkovsky.
dN / dt = −α (4GΦ / π) · N (a)
(N: number of particles (fine flock or flock) per unit volume α: collision efficiency based on influence of inorganic flocculant G: velocity gradient, Φ: average volume of particles (fine flock or flock) in unit volume)
The general solution of the elementary differential equation can be expressed as N = Aexp (−kt) (where A is the number of particles per unit volume (fine flock or flock) at the stage of t = 0, k = α (4GΦ / π)).
Based on the Smolkovsky equation, in the prior art, an operation method that relied heavily on the increase in the injection rate of the inorganic flocculant has been adopted. By setting the value, the numerical value of the collision efficiency α in the equation (a) is increased, the decrease rate of dN / dt when the fine flock is used as a reference, and the flocking is promoted.

  However, when the inorganic flocculant injection rate is increased, the floc volume increases, resulting in coarse and low-density fine flocs flowing into the filtration basin, and the residual flocculant particles in the precipitated water. As a result, the amount of fine flocs once detained increases in the amount that leaks into the filtered water, and further poses a serious technical problem that the frequency of washing the filter basin must be increased. I must.

  Reflecting such a situation, in Patent Document 1, a multi-stage rapid stirring tank is provided, and the lower limit of the stirring strength is set for the first first tank, and stirring is performed for the second tank and below. After setting the upper limit of strength, by dividing and injecting the inorganic flocculant into each rapid stirring tank, it is possible to improve particle separation efficiency and reduce the concentration of remaining inorganic flocculant (See description related to claim 6 of the claims and claim 6 of the specification).

However, in the case of the above configuration provided by Patent Document 1, the above effect is insufficient in that the stirring strength of the second tank or lower is limited more than necessary, and the inorganic flocculant as a whole The level of injection is not adjusted, and the standard for the adjustment is not set, and the evaluation that the above-described purpose can be achieved cannot be avoided.
In view of such a situation, in the invention of Japanese Patent Application No. 2009-504161 (hereinafter abbreviated as “prior application invention”), the amount of the inorganic flocculant is limited as compared with the prior art, and the stirring strength In order to prevent residual flocs and flocs from being densified and miniaturized by increasing the number of flocs, etc., in order to prevent the filtration function of the sand filtration tank from being deteriorated by the above-mentioned miniaturization of flocs, an inclined plate with a narrow pitch in the sedimentation pond And proposed a structure for efficiently separating fine flocs, and patent registration has already been made for the structure (Japanese Patent No. 4316671).

When the amount of the inorganic flocculant injected is limited and the stirring strength of the rapid stirring tank is set to a predetermined level or more as in the invention of the prior application, the fine flocs are inevitably formed. Flocculates by aggregating with each other in the sludge blanket tank, and further adsorbs the fine flocs that subsequently flow in, thereby further promoting the flocking.
However, as described above, when fine-grained, high-density fine flocs are flocculated, the flocculated particles are also dense, and thus quickly settle in the sludge / blanket tank.
In such a case, if the concentration of fine floc flowing into the sludge / blanket tank is below a predetermined amount, the sludge is caused by the fact that it is impossible to replenish the flocked particles that quickly settle as described above.・ The concentration of floc in the blanket tank will gradually decrease.

  Here, the relationship between the residual amount of the inorganic flocculant and the number of fine flocculated particles at the stage where the fine flocculation step is completed will be described based on a specific experiment.

  STR (Suction Time Ratio) at the same temperature as treated water 1 at the stage when the fine flocking process is completed, as an index reflecting the amount of inorganic flocculant injected and indicating the residual amount of flocculant particles in water. Expressed by Ts / Tv, when the same filter paper is sucked in the same amount of distilled water with the same amount of distilled water, the suction time of treated water 1 is Ts and the suction time of distilled water is Tv 5A and 5B, the graphs in FIGS. 5A and 5B end the temporal change of the STR value in the fine flocking process and the fine flocking process corresponding to the change. The correspondence with the change in the number of fine floc particles at the stage is shown.

によって表わされる数値）を、1500ｓｅｃ^−１と設定したうえで、懸濁粒子を含む被処理水に代えて、清澄水中にカオリン（白陶土であって、清澄水の懸濁の程度を実現する疑似懸濁粒子の集合体）を１ｍｇ／Ｌの濃度となるように注入すると共に、無機凝集剤であるポリ塩化アルミニウム（ＰＡＣ）を５ｍｇ／Ｌの濃度となるように注入している。 FIG. 5 (a), the experimental conditions in micro flocculation step for realizing the data, G _R value is rapid stirring intensity in one rapid agitation tank 10 (stirring coefficient is C, the stirring blade (b) The area is A (m ² ), the peripheral speed of the stirring blade is v (m / sec), the kinematic viscosity coefficient is γ (m ² / sec), and the volume (capacity) of the stirring tank is V (m ³ ). if you did this,

Is set to 1500 sec ^−1, and instead of treated water containing suspended particles, kaolin (white porcelain clay in clarified water, which realizes the degree of suspension of clarified water) The aggregate of suspended particles) is injected to a concentration of 1 mg / L, and polyaluminum chloride (PAC) as an inorganic flocculant is injected to a concentration of 5 mg / L.

According to FIGS. 5 (a) and 5 (b), under the experimental conditions as described above, the number of particles (particles / mL) having a particle size of 0.5 to 1 μm decreases as shown in (a). As shown in (b), the number (particles / mL) of particles having a particle size of 30 μm or more increases until the STR value reaches a predetermined value (specifically, 2 or less), but thereafter Is descending as in the case of (a).
These experimental results show that the aggregating ability of the inorganic flocculant decreases with the progress of rapid stirring, the remaining inorganic flocculant particles are destroyed, and the number of particles decreases. The degree of becomes more remarkable as the number of rapid stirring tanks increases.

In the sludge / blanket tank, fine flocked particles are flocked. As described above, the small number of fine flock particles flowing in is that the N on the right side in the equation (a) is small, and thus dN This means that / dt is small, that is, the rate of change from fine flock to flock is small.
That is, when the number of floc particles flowing into the sludge / blanket tank is small as described above, the degree of the flocking process that occurs based on the flow of a predetermined amount of fine flock particles in the sludge / blanket tank Moreover, it must be reduced.
Such a result inevitably impedes the function of separating the precipitate on the premise of flocking in the sludge / blanket tank.

In Patent Document 2, the degree of the flocking step is maintained at a predetermined level by directly returning the flocked particles precipitated in the sludge / blanket tank and discharged to the sludge storage tank to the sludge / blanket tank. A method is disclosed.
However, in the method of Patent Document 2, the flocculent particles returning from the sludge storage tank have not undergone the rapid stirring process, and therefore the aggregating ability based on the residual coagulant is extremely poor. Flocking based on the formation of grains and dense micro flocs cannot be expected.

JP 2007-203133 A JP 2000-176207 A

  It is an object of the present invention to provide a method for coagulating and precipitating water to be treated so that the concentration of particles in the flocking process does not decrease in a sludge blanket tank.

In order to solve the above problems, the basic configuration according to claims 1, 2, and 3 of the present invention is as follows.
(1) An inorganic flocculant injecting step for injecting an inorganic flocculant into the water to be treated; and the water to be treated into which the inorganic flocculant has been injected are mixed and stirred in a rapid stirring tank to make fine particles in the water to be treated. In the fine flocking process in which suspended particles are finely flocked in advance, and in the sludge / blanket tank, the fine flock particles that have flowed in and / or the fine flock particles or flock particles and the existing flock particles are combined. Water to be treated, and a step of precipitating and separating the flocked particles, and discharging the precipitated flocked particles and the remaining particles separated without precipitation to the outside of the sludge / blanket tank, respectively. a coagulating sedimentation processing method, supporting the precipitate separation function based on flocculated in the sludge blanket tank caused a reduction in the aggregation ability of the inorganic coagulant To prevent occurs, the precipitated floc particles, returned to the previous step of the fine flocculation process, in the case that is injected into the water to be treated injected simultaneously or before and after the inorganic flocculant Conditions for executing the inorganic flocculant injection step, that is, the type and amount of the inorganic flocculant, and the number of compartments in which the stirring tank is provided before the flocculation / precipitation treatment of the water to be treated with respect to the amount of the flocculant particles to be returned In the preliminary experiment in which the stirring conditions in the fine flocculation step such as the stirring time and the degree of stirring are set to the same conditions as in the case where the water to be treated is transferred to the coagulation sedimentation treatment step, When the water to be treated is passed through at a predetermined injection amount, it is used to measure the weight per unit volume of particles in the flocking process in the water to be treated in the sludge / blanket tank. It is determined whether or not the concentration to be reduced with the lapse of time. If not, it is adopted as an injection amount to be transferred to the coagulation sedimentation treatment of the water to be treated. By setting the injection amount standard to adopt the injection amount by increasing and adjusting so as to become the above, the concentration of particles in the flocking process in the sludge blanket tank does not decrease over time In the state, the method for coagulating and precipitating water to be treated based on the transition to coagulating and precipitating treatment of the water to be treated,
(2) The conditions for executing the inorganic flocculant injection step, that is, the type and amount of the inorganic flocculant, and the stirring conditions in the fine flocking step such as the number of compartments where the stirring tank is provided, the stirring time, and the degree of stirring In the preliminary experiment set to the same conditions as in the case of shifting to the coagulation-precipitation treatment step, the aluminum content ratio (Al / T) to the total weight of the inorganic coagulant is 0.05 in the previous stage of the fine flocking step. The concentration based on the weight measurement per unit volume of the three components of the solidified solid of the water to be treated, the inorganic flocculant, and the flocculant particles returned from the sludge / blanket tank is 7.5 mg / L or more. A method for coagulating and precipitating water to be treated according to the above (1), characterized in that the amount of flocculant particles to be fed back is set.
(3) Either the precipitated flocked particles are transferred to a concentrator adjacent to the sludge / blanket tank, and then the flocked particles are returned, either (1) or (2) A coagulation-precipitation treatment method of water to be treated as described in
Consists of.

In the present invention according to the basic configurations (1), (2), and (3), the flocs in the sludge / blanket tank are realized in a stable state on the premise of the fine flocs by the rapid stirring tank. As a result, fine floc remaining in the clarified water is finer and denser than in the case of the prior art, so that high-quality clarified water can be obtained.
Furthermore, as will be described later in the examples, particularly high-quality clarified water can be obtained when an upward flow inclined plate or an upward flow inclined pipe is installed in the vicinity of the upper outlet of the sludge / blanket tank.

It is a block diagram which implement | achieves each process in the coagulation precipitation processing method of to-be-processed water. In the sludge blanket tank when the concentration (mg / L) of suspended particles of treated water, injected inorganic flocculant, and returned flocked particles in the previous stage of the fine flocking process is changed (mg / L) It is a graph which shows the change condition of the density | concentration (mg / L) of the particle | grains in a flocking process. Precipitating in the sludge blanket tank when the suspended particles of the water to be treated in the previous stage of the fine flocking process, the injected inorganic flocculant, and the concentration (mg / L) due to the returned flocked particles are changed, And it is a graph which shows the time change of the turbidity (it shows by the number of the flocking particle | grains) of discharged | emitted precipitation water, (a) shows the case where the diameter of the said flocking particle | grain is 0.5-1 micrometer. (B) shows the case where the diameter of the flocked particles is 7.0 μm or more. In an Example, it is a graph explaining the difference of the grade of water purification | cleaning by the presence or absence of an upward flow inclination board, (a) has shown contrast of the turbidity (mg / L) as a whole, ( b) Corresponds to the number of flocculated particles remaining at the stage of purification / separation corresponding to each particle size category, and further to each particle size category when an upward flow inclined plate is used. The removal rate (with the number of particles as a unit) is shown. The situation of the change in the number of fine flock particles during the fine flocking process corresponding to the change in the STR value during the fine flocking process is shown. (A) shows the case where the particle size is 0.5 to 1 μm. (B) has shown the case where a particle size exceeds 30 micrometers.

  As shown in the block diagram of FIG. 1, the basic configuration (1) includes an injection process of the inorganic flocculant 2, a fine flocking process through mixing and stirring by the stirrer 11 in the rapid stirring tank 10, and a sludge / blanket tank The basic steps are a flocculation step and a precipitation separation step through 5.

In the sludge / blanket tank 5, the flocking process proceeds by the combination of fine flocks and / or the combination of fine flock particles or flock particles and existing flock particles.
In association with the flocking step, flocked particles having a predetermined particle size and weight are precipitated, and usually move to the sludge storage tank 9 via the concentrator 4, while the remaining particles separated without precipitation (floccing). The fine floc particles that remain without being broken, floc particles that have been flocked once but have been broken down into fragments, and floc particles that have a small particle size and weight, etc., together with the water to be treated 1 are subjected to the next sand filtration. (However, in most cases, before moving to the sand filtration tank, as shown in FIG. 1 and described in the embodiment, provided near the upper outlet of the sludge blanket tank 5. It goes through the upward flow inclined plate or the upward flow inclined pipe 8).

It is naturally planned that the basic configuration (1) can obtain fine-grained and dense micro flocs by limiting the amount of inorganic flocculant injected and setting the degree of rapid stirring to a predetermined level or higher. is doing.
In such a basic configuration (1), the flocculent particles precipitated in the sludge / blanket tank 5 are returned to the previous stage of the fine flocking step, and the treated water 1 is injected simultaneously with or before and after the injection of the inorganic flocculant. Injecting.

By such feedback and injection, the amount of inorganic flocculant injected as pointed out in the background art section is limited, and the degree of rapid stirring is set to be large so that the fine floc particles become finer and denser. In some cases, the decrease in the concentration of flocculated particles in the sludge blanket tank 5 is compensated.
However, for the injection amount of the flocked particles to be returned, in a preliminary experiment, in the case of a predetermined injection amount to be returned, the weight per unit volume of the particles in the flocking process in the sludge / blanket tank 5 is measured. It is determined whether or not the concentration is reduced. If the concentration does not decrease, it is adopted as an injection amount to be transferred to the coagulation sedimentation treatment of the water 1 to be treated. If the concentration is decreased, the concentration does not decrease. Thus, after setting the reference of the injection amount to adopt the injection amount by increasing and adjusting, the process proceeds to the coagulation precipitation treatment of the water 1 to be treated.

  Needless to say, also in the preliminary experiment, conditions for executing the inorganic flocculant injection step (specifically, conditions regarding the type and amount of the inorganic flocculant) and stirring conditions (providing a stirring tank are provided). The conditions such as the number of compartments, the stirring time, the degree of stirring, etc.) are set to the same conditions as in the case of shifting to the original coagulation precipitation process.

  In the sludge / blanket tank 5 in the previous stage of shifting to the coagulation / precipitation treatment of the water 1 to be treated, it is determined whether or not the concentration of particles in the flocking process is reduced, and when the concentration is reduced, Increasing and adjusting the injection volume based on the feedback can be easily realized by measuring the time course of the concentration.

The step of returning the precipitated flocculated particles can be selected from the preceding, simultaneous and subsequent three steps with respect to the inorganic flocculant injection step.
However, in order to exert the influence of the inorganic flocculant as much as possible, it is preferable to return at the same time as or after the inorganic flocculant injection step.

The residual amount of the inorganic flocculant in the flocked particles that have settled in the sludge / blanket tank 5 and returned to the previous stage of the fine flocking process is considerably low.
When such returned flocculated particles are mixed and stirred in the rapid agitation tank 10 together with the inorganic flocculant, like the suspended particles in the water 1 to be treated, they are finely flocculated again, and sludge It will flow into the blanket tank 5.
Therefore, the return means that, for the fine flock flowing into the sludge / blanket tank 5 after all, the portion where the fine flock particles caused by suspended particles in the water to be treated 1 are not sufficient is complemented. In the above equation (a) when the fine flock is used as a reference, the number of N on the right side is increased, and eventually the degree of decrease of the fine flock in dN / dt is also increased, so that flocking occurs. It is none other than increasing the degree.

  Thus, in the basic configuration (1), the flocked particles settled in the sludge / blanket tank 5 are returned to the previous stage of the fine flocking process, and the injection amount based on the feedback is transferred to the sludge / blanket tank 5. After setting the concentration of the number of particles in the flocculation step to a level that does not decrease, and by shifting to the coagulation sedimentation treatment of the water 1 to be treated, The basic technical idea is to obtain the above effects.

To describe the basic configuration according to claim 2 (2), FIG. 2, the rapid agitation tank 10 in the micro flocculation step and 5 compartment setting, the rapid agitation intensity G _R value and 150 sec ^-1, a fast stirring time 7 minutes, the injection amount of the inorganic flocculant is set to 0.05 with the Al / T ratio, which is the weight ratio of aluminum in the injected inorganic flocculant , and the sludge treatment is performed from the sludge storage tank 9 When the particles are returned and injected simultaneously with the injection of the inorganic flocculant, the concentrations of the three components by the suspended particles of the water 1 to be treated, the inorganic flocculant, and the returned flocked particles in the previous stage of the fine flocking step are respectively set. The time transition of the density | concentration of the flocking particle | grains in the sludge blanket tank 5 at the time of 3.0 (mg / L), 5.0 (mg / L), and 7.5 (mg / L) is shown.

The above-mentioned Al / T ratio of 0.05 corresponds to an extremely low numerical value (lower limit that can be adopted at an actual work site) as the amount of aluminum that can be adopted at a normal work site. Setting the _R value to 150 sec ⁻¹ and setting the rapid stirring time to 7 minutes is attributed to the setting of considerably high stirring conditions.
Under such conditions, when the concentration of the above three components is 3.0 (mg / L) and 5.0 (mg / L), the flocification process in the sludge blanket tank 5 is performed. The concentration of certain particles gradually decreases with the passage of water passage time.
On the other hand, when the concentration at the previous stage of the fine flocking process is 7.5 (mg / L), the concentration of the flocked particles in the sludge / blanket tank 5 is kept substantially constant.

  FIG. 3 shows the same conditions as in the experiment of FIG. 2, and the concentrations of the three components are 3.0 (mg / L), 5.0 (mg / L), and 7.5 (mg / L), respectively. In the sludge / blanket tank 5, the state of change of the number of particles with the passing time of the precipitated water 3 flowing out in a state where the floc particles are purified and separated is shown ( a) shows the case of particles having a diameter of 0.5 to 1 μm, and (b) shows the number of particles when the diameter is 7.0 μm or more.

  As is clear from FIGS. 3 (a) and 3 (b), when the concentration is 3.0 (mg / L) or 5.0 (mg / L), the diameter increases with the passage of water passage time. In contrast, the number of flocculent particles in the range of 1 increases sequentially, whereas when the concentration is 7.5 (mg / L), the flocculent particles flowing out as precipitated water 3 are roughly Is held constant.

  2 and 3 (a) and 3 (b) show that the Al / T ratio is extremely small at 0.05 at the work site of the actual coagulation-precipitation treatment method for the water to be treated 1 as in the above-mentioned conditions. In addition, even if the stirring conditions are quite high as described above, the flocculent particles in the sludge / blanket tank 5 are likely to settle, and the maintenance of the concentration of the particles in the flocking step is extremely severe. When the concentration by the three components is 7.5 (mg / L) or more, it means that the concentration of particles in the flocking process in the sludge / blanket tank 5 can be maintained at most work sites. ing.

  Paying attention to such points, in the basic configuration (2), in the preliminary experiment, the injection based on the feedback of the flocked particles so that the concentration of the three components is 7.5 (mg / L) in advance. As a result, when it is confirmed that the number of particles in the flocculation process in the sludge / blanket tank 5 does not decrease, the process proceeds to the precipitation treatment process of the water 1 to be treated. If the decrease is confirmed even though the concentration of the three components is 7.5 (mg / L) or more, the above-described decrease does not occur with respect to the injection amount based on the feedback. The above transition has been realized (however, in the actual work site, when the concentration of the three components is 7.5 (mg / L) or more, the decrease as described above is achieved). What happens is very exceptional. .

  When the concentration of the three components is not less than a predetermined concentration of 7.5 (mg / L) or more, as shown in FIGS. 3 (a) and 3 (b), the number (concentration) of each particle in the precipitated water 3 The reason for the decrease in flocs is that the amount of fine flocs particles flowing into the sludge / blanket tank 5 increases because the return amount of flocs particles is large, and the degree of flocking is maintained. Therefore, it is considered that the degree of destruction of the flocked particles is small by maintaining the degree of residual fine floc particles and the adhesion of the inorganic flocculant remaining in the fine floc particles (conversely, 3 When the concentration of the component is 3.0 (mg / L) and 5.0 (mg / L), the degree of flocking is insufficient, so the adhesive strength of the inorganic flocculant remaining in the fine flock is sufficient Flocked because it is not maintained The extent of damage to the child also is considered high.).

The basic configuration (2) is characterized by injecting an inorganic flocculant having an aluminum content ratio (Al / T) of 0.05 or less with respect to the total weight of the inorganic flocculant. When the content ratio is set small, fine flocs with extremely high density are usually formed.
In such a case, in the basic configuration (2), it is possible to maintain the function of flocking in the sludge / blanket tank 5 by returning the precipitated floc, so the numerical limitation of the embodiment is extremely useful. Provides a good standard.
  The content of aluminum in the entire water to be treated depends on the concentration of the injected inorganic flocculant, but in the case of the content ratio (Al / T), the concentration is a normal inorganic flocculant injection. By setting to the same level as in the above case, it is possible to realize the formation of fine flocs with a higher density as described above.

The basic configuration (3) according to claim 3 performs the feedback after transferring the precipitated flocked particles to the concentrator 4, but in most of the embodiments, the basic configuration (3 ) Is adopted.
However, it is originally possible to return the flocked particles precipitated directly from the sludge storage tank 9 instead of the concentrator 4.

  In the embodiment according to claim 4, the number of rapid stirring tanks 10 is divided into two or more sections, thereby increasing the chance of rapid stirring and eventually increasing the degree of stirring.

To explain in accordance with a general solution based on the Smolkowski equation, the stirring time in the first rapid stirring tank 10 is t ₁ and the stirring time in the second rapid stirring tank 10 is t _2. In comparison with the general solution N ₁ = Aexp (−kt ₁ ) in the _first rapid stirring tank 10, the number N _{1 + 2 of} particles passing through the second rapid stirring tank 10 is
N _{1 + 2} = Aexp (−kt ₁ −kt ₂ )
After all, N _{1 + 2} is a numerical value smaller than N ₁ , indicating that the degree of aggregation is further progressing.
And in an actual work site, it can contribute to reduction of the suspended particle whose diameter in the to-be-processed water 1 is 0.5-1 micrometer.

The embodiment according to claim 5 will be described. An easy-to-understand definition of STR is as described in claim 5 and the background art section. Strictly speaking, 500 mL of sample water and the same temperature and equivalent amount thereof are used. Of distilled water (totally 45 mm membrane filter paper (average pore size 0.45 μm, ADVANTEC filter paper with a porosity of 38%)) equipped with a suction device (specifically, vacuum container, filter folder, vacuum reach 26. It is defined by the ratio of STR = T _S / T _V when the time of suction by a device (with a suction pump of 7 kPa) is T _S (sec) and T _V (sec), respectively.
However, the embodiment according to claim 5 is not an STR based on the strict definition as described above, but sufficiently adjusts the degree of use of the inorganic flocculant according to the basic configuration with the STR as described in claim 5. (Limited) can be performed.

Then, as in the embodiment of claim 5, when the inorganic flocculant injection rate is adjusted so that the STR at the flocking process inlet is 2.5 or less, the fine flocs are fine and densified. For example, it is possible to grow to a floc of 30 μm or more while reflecting and maintaining the properties.
Such flocs are smaller in diameter than flocs formed by injecting a large amount of an inorganic flocculant as in the prior art, but they have a high sedimentation speed because of their high density. In addition, as will be described later in the embodiment, when an upward flow inclined plate or an upward flow inclined tube 9 is provided, fine floc particles can be efficiently separated. it can.

によって表わされる数値）を、につき、ｓｅｃ^−１の単位を選択し、急速攪拌時間であるＴ_Ｒ値につき、ｓｅｃの単位を選択した場合、双方の積であるＧ_Ｒ・Ｔ_Ｒ値が30000以上であることを特徴としている。 The embodiment of claim 6, micro flocculation step, is divided into two or more compartments, G _R value (stirring coefficient and C as rapidly stirred intensity in each compartment, the area of the stirring blade A (m ² ), The peripheral speed of the stirring blade is v (m / sec), the kinematic viscosity coefficient is γ (m ² / sec), and the volume (capacity) of the stirring tank is V (m ³ ),

Numerical) represented by, per, select a unit of sec ^-1, rapid stirring per time at which T _R values, if you select the unit of sec, G _R · T _R value is both the product is 30,000 It is characterized by being.

Generally, in each compartment of performing rapid stirring, to increase the agitation intensity G _R, yet by increasing the stirring time T _R, can reduce the number of fine suspended particles, the density of fine flocks .
As described above, when the product of both is set to 30000 or more, the high density can be sufficiently ensured, and the numerical value of 30000 provides a very useful standard.

In the embodiment of claim 6, for the normal G _R value, as in the embodiment of claim 7, when a 150 sec ^-1 or more, sets rapidly stirring time T _R values to 180 seconds (3 minutes) or more There are many.

The embodiment is characterized in that an upward flow inclined plate or an upward flow inclined pipe 8 is installed in the vicinity of the upper outlet in the sludge blanket tank 5 as in the invention of claim 8. The installation state is as shown in FIG.

To be described with reference to experiments, per rapid agitation tank 10 of the third section, and 1250Sec ^-1 to G _R values, respectively, after setting T _R values such that 7.3 minutes, the basic configuration (1 ), (2), (3), and by setting the concentration of the above three components to 7.5 (mg / L) in the previous stage of the fine flocking process, as shown in the graph of FIG. -The density | concentration of the flock particle | grains in the flock formation process in the blanket tank 5 was able to be kept constant.

In the vicinity of the outlet on the upper side of the sludge / blanket tank 5, the treated water 1 to be purified / separated is separated depending on whether or not a two-stage upflow inclined plate 8 having a pitch width of 10 mm is provided. When the turbidity and the concentration of the remaining particles were compared, the results as shown in FIGS. 4A and 4B could be obtained.
That is, FIG. 4 (a) shows the comparison result of turbidity (mg / L) in the treated water 1 that has been purified and separated and transferred to the next sand filtration step. The turbidity when present was 0.040 (mg / L), whereas the turbidity when not present was 0.211 (mg / L), and a marked difference was observed.

FIG. 4B shows the contrast of the flocculated particles that have been purified and separated corresponding to the respective particle size classifications, and the removal rate (corresponding to the respective particle size classifications when the upward flow inclined plate 8 is employed). The number of particles is used as a unit.) As the particle size of the flocculated particles cleaned and separated without precipitation is larger, the effect of purification and separation of the upward flow inclined plate 8, that is, the particle size increases. It turns out that the effect of carrying out precipitation removal of the flocculent particle | grains which are carrying out is large.
In any case, the installation of the upward flow inclined plate or the upward flow inclined pipe 8 reduces the turbidity by separating the remaining particles flowing out of the sludge / blanket tank 5, further promoting the precipitation separation, The treated water 1 can be further clarified.

  The present invention can be used in all fields of sewage using an inorganic flocculant and sludge treatment industry.

DESCRIPTION OF SYMBOLS 1 To-be-processed water 2 The 1st injection | pouring position of the inorganic flocculant (1st inorganic flocculant) in the 1st flocculant injection | pouring process 3 Precipitation water 4 Concentrator 5 Sludge blanket tank 6 Sludge blanket layer 7 Clarification zone 8 Upflow Inclined plate or upward flow inclined pipe 9 Sludge storage tank 10 Rapid stirring tank 11 Rapid stirrer 101 First section 102 of rapid stirring tank Second section 103 of rapid stirring tank Third section of rapid stirring tank

Claims (8)

Inorganic flocculant injection step of injecting an inorganic flocculant into the water to be treated, and the treated water into which the inorganic flocculant has been injected are mixed and stirred in a rapid agitation tank, and fine suspended particles in the water to be treated In the sludge / blanket tank and / or in the sludge / blanket tank based on the combination of the fine flock particles that flowed in and / or the combination of the fine flock particles or floc particles with the existing flock particles. Coagulating and precipitating treatment of the water to be treated having a step of precipitating and separating the flocculated particles, and discharging the precipitated flocculated particles and the remaining particles not precipitated to the outside of the sludge / blanket tank, respectively. a method, it hinders sedimentation separation function based on flocculated in the sludge blanket tank caused a reduction in the aggregation ability of the inorganic flocculant raw To prevent Rukoto, the precipitated floc particles, fine flocculation returned to the previous step of step, the inorganic injection and simultaneous aggregating agent or the case that is injected into the water to be treated before and after Conditions for executing the inorganic flocculant injection step of the type and amount of the inorganic flocculant, and the number of compartments where the stirring tank is provided, before the flocculation and precipitation treatment of the water to be treated for the amount of flocculant particles to be returned In a preliminary experiment in which the stirring conditions in the fine flocculation step such as the stirring time and the degree of stirring are set to the same conditions as in the case of shifting to the coagulation and precipitation treatment step of the water to be treated, predetermined in the flocked particles performing the feedback Based on the measurement of the weight per unit volume of particles in the flocculation process in the treated water in the sludge / blanket tank when the treated water is passed through It is determined whether or not the degree decreases with the lapse of time. If not, it is adopted as an injection amount to be transferred to the coagulation precipitation treatment of the water to be treated. By setting the injection amount standard to adopt the injection amount by increasing and adjusting so that the concentration of particles in the flocating process in the sludge blanket tank does not decrease over time In addition, a method for coagulating and precipitating water to be treated based on the transition to coagulating and precipitating treatment of water to be treated. The conditions for executing the inorganic flocculant injection step, which are the type and amount of the inorganic flocculant, and the stirring conditions in the fine flocking step, such as the number of sections in which the stirring tank is provided, the stirring time, and the degree of stirring, In the preliminary experiment set to the same conditions as when the process was shifted to the treatment process, the aluminum content ratio (Al / T) with respect to the total weight of the inorganic flocculant was set to 0.05 or less in the previous stage of the fine flocking process . The solids of the water to be treated, the inorganic flocculant, and the flocked particles returned from the sludge / blanket tank are fed back so that the concentration based on the weight measurement per unit volume of the three components is 7.5 mg / L or more. The method for coagulating and precipitating water to be treated according to claim 1, wherein an injection amount of the flocked particles is set.   The covered flocculated particles are transferred to a concentrator adjacent to the sludge / blanket tank, and then the flocculated particles are returned. A method for coagulating and precipitating treated water.   The fine flocking step is provided with a rapid stirring tank divided into two or more sections in a state of being connected in series so that the water to be treated can be sequentially transferred. The coagulation sedimentation processing method of to-be-processed water of any one of these.   STR (Suction Time Ratio: distilled water with the same temperature and equal amount as the water to be treated, at the same level of suction, as an indicator of the remaining amount of agglomerated agglomerates When the same filter paper is sucked, when the suction time of treated water is Ts and the suction time of distilled water is Tv, the ratio by the index expressed by Ts / Tv) is 2.5 or less. The method for coagulating and precipitating water to be treated according to any one of claims 1, 2, 3, and 4. G _R value is rapid stirring intensity in each compartment of the fine flocculation step (stirring coefficient is C, the area of the stirring blade and A (m ^2), the peripheral speed of the stirring blade v and (m / sec), the dynamic When the viscosity coefficient is γ (m ² / sec) and the volume (capacity) of the stirring tank is V (m ³ ),

For values) represented by, select the unit of sec ^-1, per T _R value is rapid stirring time, if you select the unit of sec, G _R · T _R value is both the product is 30,000 or more The method for coagulating and precipitating water to be treated according to any one of claims 1, 2, 3, 4, and 5. The rapid agitation intensity G _R value and 150 sec ^-1 or more, rapid stirring time T _R value of 180 seconds (3 minutes) setting coagulating sedimentation processing method of the water to be treated according to claim 6, characterized in that above.   The upflow-flow inclined plate or the upflow-flow inclined pipe is installed in the sludge blanket tank near the upper outlet, according to any one of claims 1, 2, 3, 4, 5, 6, and 7. The method for coagulating and precipitating water to be treated according to Item 1.

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