JP2011212566A - Control method of amount of sludge in water sprinkling type water treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To preferably control an amount of sludge carried on the surface of a carrier in a reactor by a simple method, with respect to a water sprinkling type water treatment apparatus using DHS (Down-flow Hanging Sponge).SOLUTION: The water sprinkling type water treatment apparatus having a plurality of reactors standingly charged with the carrier is installed. The water to be treated is supplied to the respective reactors, thereby the water to be treated is subjected to aerobic treatment, and supply of the water to be treated to the reactors is stopped for a fixed period before the amount of the sludge carried on the surface of the carrier in the reactor increases by the aerobic treatment and reaches a saturated region 8, and the supply of the water to be treated to the reactors is restarted after the sludge carried on the surface of the carrier is reduced by self-decomposition by microorganisms, and the supply of the treating water to the reactors is stopped again for a fixed period before the amount of the sludge carried on the surface of the carrier in the reactor increases and reaches the saturated region 8. Such operations are carried out in a rotation system for the all reactors.

Description

  The present invention relates to a method for controlling the amount of sludge in a sprinkling water treatment apparatus. In particular, the present invention relates to a method for controlling the amount of excess sludge generated in a non-aerobic aerobic treatment method in which a carrier carrying aerobic microorganisms is stacked and water to be treated is sprinkled from above.

Conventionally, in order to purify sewage, or to purify wastewater such as industrial wastewater, miscellaneous wastewater, or agricultural wastewater (hereinafter referred to as treated water), the surface (outside the carrier) If the surface and / or the carrier is a porous body, the plastic carrier and sponge carrier capable of supporting aerobic microorganisms are loaded on the stack (including the surface of the pores), and the water to be treated is sprinkled and dropped from above. A watering type water treatment apparatus using an aerobic aerobic treatment method (DHS: Down-flow Hanging Sponge, hereinafter referred to as DHS) is known. (For example, see Patent Document 1 and Patent Document 2).
Here, in DHS, the carrier stacked in the reaction vessel is, for example, a plastic net formed in a bowl shape, a plastic net formed in a cylinder, or a foamed polyurethane sponge in a cylinder, In order to prevent the sponge below from collapsing when stacked, there are those loaded inside the plastic mesh tube mentioned above, and suspension types that suspend the sponge sheet, all of which are on the carrier surface from above. The surface is roughened so that the sludge component contained in the treated water to be dripped is entangled. And aerobic microorganisms that are artificially sprinkled in the reaction tank or brought along with the sludge by the treated water settle on the sludge component tangled on the surface of the carrier, and decompose the sludge component while gaining the sludge component. It is.
This DHS method is superior because the water to be treated is dripped onto the carrier from above, so the contact opportunity between air and sludge components on the surface of the single unit is immersed (treatment in a state where sludge is suspended in water) The oxygen required for aerobic microorganisms can be sufficiently supplied without an aeration device. In addition, as a characteristic matter, there is a matter of growing along with the supply of sludge that feeds aerobic microorganisms on the surface of the carrier, and increasing the amount of trapped sediment as sludge trapped on the surface of the carrier. With respect to the amount of sludge trapped and deposited on the surface of the carrier, for example, Patent Document 3 discloses an apparatus that displaces a suspended carrier itself to the outside of the reaction tank and mechanically scavenges too much accumulated sludge. There is.

When water to be treated (organic wastewater) containing organic substances such as sewage flows into the reaction tank of the watering type water treatment device, sludge containing microorganisms is trapped and deposited on the sponge carrier during the water treatment in the reaction layer. Water treatment is carried out by sludge self-degradation by microorganisms. At this time, the change over time in the amount of sludge retained on the carrier surface held by the carrier in the reaction tank is expressed by the following equation.
Carrier surface retained sludge amount = Sludge increase amount-Sludge self-decomposition amount (I)
This formula is synonymous with the following formula.
Carrier surface retained sludge amount = (sludge trapping amount + microbial growth amount)-sludge self-decomposition amount (II)

The amount of sludge increase and the amount of self-degradation of sludge are expressed by the F / M ratio, which is the ratio of the organic substance (F) serving as a microorganism feed in the treated water flowing into the reaction tank and the amount of microorganisms (M) in the reaction tank. The relationship is as follows.
When F / M ratio is large (increase amount> self-decomposition amount) → Increase in the amount of retained sludge on the carrier surface When F / M ratio is small (increase amount <self-decomposition amount) → Decrease in the amount of sludge retained on the carrier surface

In the sprinkling water treatment apparatus using the DHS, at the initial stage of operation when microorganisms in the reaction tank are still growing, the amount of microorganisms is small relative to the organic matter load of the treated water that flows in, that is, the F / M ratio is large. Therefore, the amount of sludge retained on the surface of the carrier increases with time, but the F / M ratio becomes sufficiently smaller during the steady operation period when microorganisms are acclimatized.
Increase in sludge ≒ Sludge self-decomposition amount. Therefore, it has been considered that the increase in the amount of sludge retained on the carrier surface is negligible in the operation of the apparatus. Therefore, conventionally, a method for controlling the amount of sludge in the reaction tank has not been proposed.

JP 2007-307530 A Japanese Patent No. 3967896 JP 2005-199182 A

  As described above, in the steady state where the treatment is performed satisfactorily with the watering type water treatment apparatus using DHS, the amount of sludge increase and the amount of sludge self-decomposition in the reaction tank are roughly balanced, and thus the reaction The amount of sludge retained on the surface of the carrier in the tank is considered to be stable with little increase or decrease.

  However, in the sprinkling water treatment apparatus, the F / M ratio in the reaction tank may change, or the growth characteristics and self-decomposition characteristics of microorganisms in the carrier surface holding sludge may rarely change. Therefore, there is always a possibility that the amount of sludge retained on the carrier surface will increase from the stable state.

  Therefore, when a situation occurs in which the amount of sludge retained on the surface of the carrier changes from a stable state to an increase, the sludge layer in the reaction tank thickens and the carrier becomes clogged. There may be a problem that it peels off from the carrier and falls off and enters the treated water. In this way, when the sludge peeled off from the carrier is mixed into the treated water, it will cause a problem directly related to the instability of the treated water, so it is necessary to take preventive measures in advance to prevent such a problem from occurring. However, until now, there has been no suitable means for avoiding such problems.

  In order to deal with the problems as described above, in the existing technology such as the activated sludge method that performs water treatment in a state where the sludge is suspended in water, by extracting and removing excess sludge from the reaction tank, Controlling the amount of sludge in the reaction tank is performed.

However, in the case of the watering type water treatment apparatus, it is not easy to draw out only a part of the sludge in the reaction tank. This is because the existing immersion-type technology that performs water treatment in a state where sludge is suspended in water is essentially equipped with a mechanism for solid-liquid separation of suspended sludge using a sedimentation section or weir with a large volume. However, in the water sprinkling water treatment device (DHS), the water to be treated is dropped onto aerobic microorganisms using the sludge adhering to the carrier as a bed. As a basis for the treatment reaction, sludge adheres to the carrier widely loaded in the reaction tank, and even if the attached sludge thickens and the chance of contact between the microorganisms and the water to be treated decreases, This is because sludge cannot be reduced unless it is mechanically scraped off against the expected adhesion. However, when surplus sludge is mechanically scraped off from the carrier, when the operation is resumed after that, sludge whose adhesion to the carrier has become weak due to mechanical treatment will flow out, and the suspended sludge Unnecessary features of the solid-liquid separation part are not available.
Therefore, in the conventional watering type water treatment apparatus, there is virtually no effective sludge amount control method.

  The present invention has been made in view of the above problems, and in a sprinkling water treatment apparatus using DHS, the amount of retained sludge on the carrier surface in the reaction tank is simplified without using a process such as mechanical scraping. It is an object of the present invention to provide a method for controlling the amount of sludge in a sprinkling water treatment apparatus that can be suitably controlled by various techniques.

  The present invention provides a sprinkling water treatment apparatus having a plurality of reaction tanks that are statically loaded with a carrier to which aerobic microorganisms and sludge adhere and are fixed on the surface, and supplies treated water to each of the reaction tanks. Perform aerobic water treatment of the treated water, and stop supplying the treated water to the reaction tank for a certain period of time before the carrier surface retained sludge amount in the reaction tank increases due to the aerobic water treatment and reaches the saturation region. Then, after the carrier surface retained sludge is self-degraded by aerobic microorganisms and reduced in volume, the supply of treated water to the reaction vessel is resumed, and the amount of carrier surface retained sludge in the reaction vessel is increased by the aerobic water treatment. A watering-type water treatment device that repeats the operation of stopping the supply of treated water to the reaction tank for a certain period of time before reaching the saturation region, and performs this operation in a rotating manner for all reaction tanks In the sludge amount control method It is intended.

In the method of controlling the amount of sludge in the watering type water treatment apparatus, supply of water to be treated to the reaction tank before the carrier surface retained sludge amount in the reaction tank is increased by the aerobic water treatment and reaches a saturation region. A method for calculating the certain period of time
dX / dt = Xr + α × Sr−a × X _B
(Each symbol is as follows. X: Amount of sludge retained in reaction tank, t: Time, Xr: Amount of sludge trapped, Sr: Amount of dissolved organic matter decomposed, X _B : Amount of microorganisms in reaction tank (fraction of X) , alpha: growth rate of X associated with soluble organic decomposition (= sludge conversion ratio), a: autolysis rate of X _B (= endogenous respiration rate))
In the formula
Xr: Sludge trapping amount = 0, Sr: Soluble organic matter decomposition amount = 0, obtained by substitution calculation, X: Derived from the relationship between the amount of sludge retained in the reaction tank and the elapsed time t. is there.

  In the sludge amount control method in the sprinkling water treatment apparatus, when the supply of the water to be treated is resumed after the supply of the water to be treated to the reaction tank is stopped for a certain period, the supply of the water to be treated is resumed. It is preferable to return the treated water led out from the reaction tank to the inlet of each reaction tank for a predetermined period.

  In the method of controlling the amount of sludge in the sprinkling water treatment apparatus, air supply means is provided in each reaction tank, air is supplied to the reaction tank that stops the supply of water to be treated by the air supply means, and the carrier surface holding sludge is obtained. It is preferable to promote the action of self-degrading by microorganisms and reducing the weight.

  In the method of controlling the amount of sludge in the sprinkling water treatment apparatus, each reaction tank is provided with heating means, the reaction tank for stopping the supply of water to be treated is heated by the heating means, and the carrier surface retained sludge is self-generated by microorganisms. It is preferable to promote the action of decomposing and reducing the weight.

  According to the method of controlling the amount of sludge in the water treatment apparatus of the present invention, the amount of sludge retained on the surface of the carrier in the reaction tank increases and reaches the saturation region by supplying the water to be treated to the reaction tank and treating with aerobic water. Before the treatment water supply to the reaction tank is stopped for a certain period, the support surface retained sludge is self-decomposed by microorganisms and reduced, and then the supply of treatment water is resumed. The operation of stopping the supply of treated water to the reaction tank again for a certain period of time before the surface retention sludge volume increases and reaches the saturation region is repeated, so the carrier surface sludge volume in the reaction tank is always saturated. Therefore, the sludge layer thickens and the carrier clogs, or the thickened sludge layer peels off from the carrier. Problem of falling off and mixing into treated water It can be an excellent effect of being able to avoid the occurrence in advance.

  In addition, the operation of stopping and restarting the supply of treated water for a certain period is applied to a plurality of reaction tanks in a rotating manner, so that the aerobic water is not stopped without stopping the operation of the watering treatment system. There is an effect that the amount of sludge can be controlled while continuing the treatment.

  In addition, the operation of stopping and restarting the supply of the water to be treated to each reaction tank only needs to be performed by opening and closing the water supply valve.

  In addition, when the supply of the water to be treated is resumed after the supply of the water to be treated to the reaction tank is stopped for a certain period, the treated water led out from the reaction tank along with the resumption of the supply of the water to be treated is supplied for a predetermined period. Therefore, it is possible to prevent the problem that dirty treated water flows out from the reaction tank that resumes the supply after the supply of the water to be treated is stopped.

  Also, air supply means or heating means is provided in each reaction tank, and air is supplied to the reaction tank that stops the supply of water to be treated for a certain period of time, or the reaction tank is heated, or air supply and heating are performed. By carrying out at the same time, it is possible to promote the action of the carrier surface-retained sludge to be self-degraded by microorganisms and to reduce the amount, and therefore, there is an effect that the operation stop period of the reaction tank can be shortened.

It is a graph which shows the result of having investigated the behavior of the carrier surface retention sludge amount using a test plant. It is a graph which shows the behavior of the support surface sludge amount when supply of the to-be-processed water with respect to a reaction tank is stopped. It is a front view which shows an example of the watering type water treatment apparatus which implements this invention. It is a graph which shows an example of the sludge amount control method of this invention. It is a graph which shows the idea which enlarges the reduction | decrease rate of the amount of carrier surface holding sludge. It is the side view of FIG. 3 which showed the apparatus structure for sludge reduction period shortening. It is a front view which shows an example of the watering type water treatment apparatus using general DHS.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  Prior to describing the embodiment of the present invention, the behavior of the amount of sludge retained on the carrier surface in the reaction tank of the sprinkling water treatment apparatus will be described first.

  FIG. 7 shows an example of a sprinkling water treatment apparatus 1 using a general DHS. In FIG. 7, reference numeral 2 denotes one reaction in which a sponge carrier 3 (hereinafter referred to as a carrier) is statically loaded. Water to be treated 5 supplied by a water supply pump 4 is sprinkled on the upper part of the reaction tank 2, and the water 5 to be treated sprinkled from above is formed by sludge microorganisms held on the carrier 3. The aerobic water treatment is performed, so that clean treated water 6 is derived from the lower part of the reaction tank 2.

The time change of the carrier surface retained sludge amount in the reaction tank 2 of the sprinkling water treatment apparatus 1 shown in FIG. 7 can be expressed by the following formula based on the formulas (I) and (II) described above.
dX / dt = (X _inf −X _eff ) + α · (S _inf −S _eff ) −a · X _B
Moreover, this formula is synonymous with the following formula (1).
dX / dt = Xr + α · Sr−a · X _B (1)
Each symbol in the above two formulas has the following meaning.
X: amount of sludge retained on the surface of the carrier in the reaction tank t: time X _inf : amount of sludge in the inflow water X _eff : amount of sludge in the outflow water Xr: amount of sludge trapped S _inf : amount of soluble organic matter in the inflow water S _eff : amount of soluble organic matter in the effluent water sr: soluble organic substances decomposed amount X _B: (the fraction of X _T) reactor microbial load
α: Sludge conversion rate (X growth rate associated with dissolved organic matter decomposition)
a: endogenous respiration rate (self-decomposition rate of the X _B)

In the above formula (1), X _B is a fraction of X. Therefore, when the ratio of X _B in X is b, this formula is expressed as dX / dt = Xr + α · Sr−a · b · X ... (2)
Can be rewritten.
When formula (2) is transformed, dX / dt = a · b {(Xr + α · Sr) / (a · b) −X}
← → {(a · b) / (Xr + α · Sr−a · b · X)} dX = a · bdt
And solving for X: 0 → X, t: 0 → t,
X = {1−exp (−a · b · t)} · (Xr + α · Sr) / (a · b) (3)
Is obtained.

Moreover, each parameter of said Formula (3) at the time of implementing a water treatment test using the test plant of the watering type water treatment apparatus 1 of FIG. Table 1 shows the case where the water to be treated is domestic wastewater (sewage), which is the most common example of organic wastewater.

Using Table 1 and Formula (3), the time change of the carrier surface retained sludge amount was simulated, and the results are shown in FIG. The horizontal axis in FIG. 1 represents the operation period (days), and the vertical axis represents the carrier surface retained sludge amount X (kg-SS / m ³ carrier).

  As shown in Table 1, since the sludge conversion rate α, the endogenous respiration rate a, and the microorganism ratio b in the carrier surface retained sludge have the required ranges, the carrier surface retained sludge amount X is the upper limit shown in FIG. It is a theory that behaves between the range curve 7a and the lower limit range curve 7b. However, when the apparatus is operating satisfactorily, the sludge conversion rate α, the endogenous respiration rate a, and the microorganism ratio b in the carrier surface holding sludge in the reaction tank 2 vary greatly from values close to their average values. Therefore, the carrier surface retained sludge amount does not approach the upper limit range curve 7a or the lower limit range curve 7b, and the carrier surface retained sludge amount in a normal case may change along the average behavior curve 7. Confirmed at test plant.

As shown by the above average behavior curve 7, the amount of sludge on the surface of the carrier per m ³ of the carrier in the sprinkling water treatment apparatus increases rapidly at the beginning of startup and then increases over time to a constant value. It behaves like approaching (increase in the amount of sludge retained on the carrier surface approaches 0).

On the other hand, the reaction tank 2 of the sprinkling water treatment apparatus 1 has a saturation region 8 indicating a range in which sludge is physically held in a saturated state. The saturation region 8 in the case of the reaction tank 2 in FIG. 7 is empirically 25 to 35 kg-SS / m ³ carrier as shown in FIG. 1, and this saturation region 8 is a fixed value and does not change. In FIG. 1, 8 a is a lower limit value of the saturation region 8, and 8 b is an upper limit value of the saturation region 8.

  In biological water treatment equipment, the capacity of the equipment is proportional to the amount of organisms responsible for the treatment. In the sprinkling water treatment apparatus, the larger the amount of sludge containing microorganisms held by the carrier, the more the processing capacity of the apparatus can be secured, and the saturated region 8 indicates the maximum amount of sludge retained on the carrier surface in the watering water treatment apparatus 1. . However, when the amount of retained sludge on the carrier surface exceeds the upper limit 8b, the carrier is clogged due to thickening of the sludge layer, or the sludge layer is detached from the carrier and dropped off, resulting in deterioration of the quality of treated water. There is a possibility of causing. In FIG. 1, in the case of the upper limit range curve 7a in which the increase in the amount of retained sludge on the carrier surface is estimated to be the largest, the upper limit value 8b is reached in about 80 days and in the case of the average behavior curve 7 about the same day. Further, in the case of the lower limit range curve 7b in which the increase in the amount of retained sludge on the carrier surface is estimated to be the smallest, the saturation region 8 is not reached even after 700 days.

  The problem in the above is the case where the amount of sludge retained on the carrier surface exceeds the upper limit 8b of the saturation region 8, and the operating state in which the average behavior curve 7 is within the range of the saturation region 8 as shown in FIG. In this case, the F / M ratio in the reaction tank 2 may change, or the growth characteristics and self-decomposition characteristics of microorganisms may rarely change. Since the amount of retained sludge increases beyond the upper limit 8b of the saturation region 8, it is necessary to establish means that can prevent such a problem.

In Figure 1, the rate at which the support surface holding sludge quantity X _T increases, the formula (1), (2) Sludge increasing factor in (= Xr + α · Sr) and sludge reduction factor _{(= a · X B = a} · b · X) is determined by the balance.

  In the sprinkling water treatment apparatus 1, in order to keep the water treatment quality in a high and more stable state, the carrier surface retained sludge amount should be maintained near the saturation region lower limit value 8a. As a result, the amount of sludge retained on the carrier surface easily exceeds the saturation upper limit value 8b due to sudden fluctuations in the growth characteristics, self-degradation characteristics, or F / M ratio of the microorganisms, while maintaining the processing capacity of the apparatus near the maximum. This is considered to be easier to avoid. For this purpose, it is required that dX / dt ≦ 0 in the equation (1) immediately before the carrier surface retained sludge amount that changes with time as shown in the average sludge behavior curve 7 reaches the saturation range lower limit value 8a. . In order to obtain dX / dt ≦ 0, it is most certain to set the sludge increase factor (= Xr + α · Sr) to 0, that is, to stop the supply of the treated water 5 to the reaction tank 2.

When the supply of the water 5 to be treated to the reaction tank 2 is stopped, that is, when Xr = 0 and Sr = 0 in Table 1, dX / dt = −a · b · X from equation (2)
1 / XdX = -a.bdt
When this is integrated in X: X ′ → X, t: 0 → t, X = X ′ · exp (−a · b · t) (4)
It can be expressed as
FIG. 2 shows the behavior of the carrier surface retained sludge amount simulated using Table 1 and Equation (4).

  As shown in FIG. 2, when supply of the to-be-processed water 5 is stopped, the carrier surface retained sludge amount changes with time so as to decrease between the upper limit range curve 9a and the lower limit range curve 9b. Stopping the supply of the water 5 to be treated is synonymous with stopping the supply of the organic substance (F) serving as a feed for microorganisms in the reaction tank 2, and the sludge self in the reaction tank 2 is minimized and the F / M ratio is minimized. Decrease in the amount of sludge retained on the carrier surface due to decomposition. The amount of sludge retained on the carrier surface in a normal case decreases along an intermediate average behavior curve 9 showing values close to the average values of the sludge conversion rate α, the endogenous respiration rate a, and the microorganism ratio b in the sludge. In FIG. 2, when the amount of sludge immediately before the supply of treated water 5 is stopped is 100%, the amount of retained sludge on the carrier surface becomes 80% after 15 days after the supply of treated water 5 is stopped, and the amount of retained sludge on the surface of the carrier is reduced. It shows that it was reduced by 20%.

  The mode of the method of the present invention based on the above idea will be described below.

  FIG. 3 shows an example of a watering type water treatment apparatus for carrying out the present invention. The watering type water treatment apparatus 100 includes a plurality of reaction vessels 101 in which carriers (see FIG. 7) are statically loaded. Although FIG. 3 shows a case where five reaction vessels 101 are provided, the number of reaction vessels 101 is not limited to that as long as a plurality of reaction vessels 101 are provided. As shown in FIG. 3, the reaction vessel 101 may be one in which the inside of the reaction apparatus main body 102 is divided into a plurality of sections by a partition wall 103, or includes a plurality of reaction vessels configured independently. Also good.

  On the other hand, the water to be treated 5 from the water supply pump 4 is supplied to the distribution tank 104, and the water to be treated 5 supplied to the distribution tank 104 is supplied by the water supply pipes 105 provided with water supply valves VA1 to VA5, respectively. The reaction vessel 101 is supplied. The treated water 6 treated in each reaction tank 101 is taken out to the outside by treated water take-out pipes 106 each having treated water valves VB1 to VB5.

  In addition, one end of a circulating water pipe 107 provided with circulating water valves VC1 to VC5 is connected between each reaction tank 101 and each of the treated water valves VB1 to VB5 in each treated water take-out pipe 106. The other end of the water pipe 107 is gathered into one pipe and connected to the treated water circulation pump 108. By opening and closing the circulating water valves VC1 to VC5, the treated water in any reaction tank 101 is taken out and the circulating water is collected. 109 can be recirculated to the distribution tank 104.

An example of the sludge amount control method of the present invention combining the idea shown in FIG. 1 and the idea shown in FIG. 2 is shown in FIG. 4, and parameters of the sludge control model in the water spray type water treatment apparatus 100 of FIG. It was. The curve of FIG. 4 showing the behavior of the carrier surface retained sludge amount according to Table 2 was based on the average behavior curve 7 of FIG.

  In the initial operation of the water spray type water treatment apparatus 100 of FIG. 3, the feed water pump 4 is driven and the treated water 5 is supplied to the distribution tank 104. At this time, the feed water valves VA1 to VA5 are opened, and the treated water valves VB1 to VB1. VB5 is open and circulating water valves VC1 to VC5 are closed, and the treated water 5 in the distribution tank 104 is distributed and supplied to each reaction tank 101 for aerobic water treatment.

  When the water 5 to be treated is supplied to the reaction tank 101 and aerobic water treatment is performed, sludge is generated in the reaction tank 101, and the amount of sludge retained on the surface of the carrier is changed over time as shown in the average behavior curve 7 shown in FIG. To increase. At this time, before the carrier surface retained sludge amount in the reaction tank 101 reaches the lower limit value 8a of the saturation region 8, the supply of the treated water 5 to the reaction tank 101 is stopped. The reaction tank 101 at the left end in FIG. 3 will be described as an example. When the amount of sludge retained on the carrier surface in the reaction tank 101 at the left end is just before reaching the lower limit value 8a of the saturation region 8, the water supply valve VA1 is closed and the reaction is performed. Supply of the to-be-processed water 5 with respect to the tank 101 is stopped. At this time, since the saturation region 8 of the reaction tank 101 is determined as described above and is known in advance, the control for stopping the supply of the water 5 to be treated can be easily performed. In FIG. 4, since the carrier surface retained sludge amount approaches the lower limit value 8a of the saturated region 8 in 120 days after the start of the aerobic water treatment, the supply of the treated water 5 immediately before the lower limit value 8a of the saturated region 8 Shows the case of stopping.

  Since the supply of the organic matter serving as microorganism feed is stopped in the reaction tank 101 in which the supply of the water to be treated 5 is stopped, the sludge retained in the reaction tank 101 is actively self-decomposed by the microorganisms. The amount of sludge retained on the carrier surface in the reaction tank 101 decreases along the average behavior curve 9 shown in FIG. The broken line shown in FIG. 4 is a virtual curve of the average behavior curve 7 when the supply of the treated water 5 is not stopped.

  After the carrier surface retained sludge amount is reduced by a predetermined amount due to the stop of the supply of the water to be treated 5, the water supply valve VA1 is opened again to resume the supply of the water to be treated 5 to the reaction tank 101 at the left end. When the supply of the treated water 5 to the reaction tank 101 is resumed, the amount of the carrier surface retained sludge in the reaction tank 101 increases again, so that the treated water 5 to the reaction tank 101 again before reaching the saturation region 8. Stop supplying. By repeating this operation as shown in FIG. 4, the carrier surface retained sludge amount is lower than the lower limit value 8a of the saturation region 8 but is always stably operated in a region where the activity of microorganisms immediately before the saturation region 8 is active. Become.

  Thus, by always maintaining the carrier surface retained sludge amount in the reaction tank 101 within the range immediately before the saturation region 8, for example, the F / M ratio in the reaction tank 101 changes, or the growth characteristics of microorganisms. Even if the self-decomposition property changes and the carrier surface retained sludge amount increases, it can be prevented that the carrier surface retained sludge amount remains in the saturation region 8 and increases from the upper limit value 8b. Therefore, the problem that the sludge layer is thickened and the carrier is clogged, or the thickened sludge layer is peeled off from the carrier and dropped out and mixed into the treated water has been generated. Can be prevented.

  In addition, the operation for stopping and restarting the supply of the water 5 to be treated to each reaction tank 101 can be performed by an extremely simple operation because it is only necessary to open and close the water supply valves VA1 to VA5.

As described above, as described above, after the supply of the treated water 5 is stopped for a certain period of time, the operation of resuming the supply of the treated water 5 again is performed in a rotating manner for all the reaction tanks 101. To. That is, the relationship between the operation of stopping operation and the support surface holding sludge shown in FIG. 4 shows the result of testing with only one of the five reaction tanks in FIG. The amount of retained sludge on the surface of the carrier is reduced by operating from the operation time when the amount of retained sludge X has reached. For example, one of the five reaction tanks in FIG. If not, the treated water 5 is supplied to 5 units only for the first operation, but 5 units before the carrier surface retained sludge amount X reaches the lower limit of the saturation region 8 in anticipation of the regeneration time of 1 unit. One of the reaction tanks 101 is cut off, and the supply of water to be treated is stopped to start regeneration. Thereafter, before the carrier surface retained sludge amount X reaches the lower limit of the saturation region 8, the supply of water to be treated is resumed in one regenerated reaction tank 101 after a predetermined regeneration time, and at the same time, The supply of the water to be treated to one reaction tank 101 in the rotation is stopped to start the regeneration. By repeating this rotation operation, the carrier surface retained sludge amount X of the entire four reaction tanks 101 can always be stably operated with the lower limit of the saturation region 8 as the upper limit.
By repeating this operation, the amount of sludge retained on the surface of the carrier is lower than the lower limit value 8a of the saturated region 8, but the activity of microorganisms immediately before the saturated region is thriving, although the operation regeneration cycle shown in FIG. In such a region, the vehicle is always stably operated.

  The period during which the supply of the treated water 5 to the reaction tank 101 is stopped is measured by testing for each kind of treated water, α: sludge conversion rate (sludge growth rate accompanying dissolved organic matter decomposition), a: 2 depending on the relationship between the elapsed time t in FIG. 2 and the amount X of retained sludge on the carrier surface, which varies depending on the endogenous respiration rate (sludge self-decomposition rate), b: the proportion of microorganisms in the carrier surface retained sludge, and the like. Can do.

  Since the target amount of the water 5 to be treated is determined in the sprinkling water treatment apparatus 100, when the supply stop period for the reaction tank 101 is set to be long, the amount of water supplied to the stopped reaction tank 101 is set. Since the to-be-processed water 5 is processed in the other reaction tank 101, the supply amount of the to-be-processed water 5 to the other reaction tank 101 increases, and the amount of carrier surface holding sludge in the other reaction tank 101 increases. Therefore, it is preferable to set the supply stop period short.

  In FIG. 4 in which treated water is sewage (domestic wastewater), about 7 days when the carrier surface retained sludge amount is reduced by about 10% is set as a supply stop period for treated water 5 and a period for performing normal operation again is 20. The behavior of the amount of sludge retained on the carrier surface when set as before and after is shown. In actual operation, Table 2 is created according to the type of wastewater, and each parameter is input to the above formulas (3) and (4) to determine the setting of the supply period and stop period of the treated water. it can.

  On the other hand, in the above control, when the supply of the treated water 5 is resumed after the supply of the treated water 5 is stopped, the sludge retained on the carrier in a state where the moisture is reduced is washed away by the supply of the treated water 5. There is a risk that it will fall under the action of being mixed into the treated water.

  Therefore, for example, when the supply of the treated water 5 is resumed after the supply of the treated water 5 to the leftmost reaction tank 101 is stopped, the treated water valve VB1 is closed, the circulating water valve VC1 is opened, and the treated water circulation pump 108 is opened. , The treated water from the reaction tank 101 is controlled to be returned to the distribution tank 104 as the circulating water 109.

  Thus, even if the carrier surface holding sludge falls when the supply of the water to be treated 5 is restarted, the dirty treated water is not taken out from the reaction tank 101, and the circulating water valve VC1 and the treated water circulating pump 108 are removed. The circulating water 109 is circulated through the distribution tank 104 as circulating water 109, and the circulating water 109 is mixed with the treated water 5 and supplied to each reaction tank 101.

  Here, the recirculation period in which the treated water in the reaction tank 101 that has resumed the supply of the treated water 5 is returned to the distribution tank 104 as the circulating water 109 is determined based on the residence time of the treated water 5 in the reaction tank 101. Can do. The retention time of the treated water 5 in the reaction tank 101 is empirically about 3 to 5 hours on average, and therefore the recirculation period is kept at least twice the retention time, for example, 8 hours or more. That's fine.

  Therefore, there is no problem that dirty treated water flows out of the reaction tank 101 that resumes the supply after the supply of the treated water 5 is stopped.

  Moreover, in the sludge amount control method described above, as shown by the arrow in FIG. 5, if the rate of reduction of the carrier surface retained sludge amount can be increased, the period for stopping the supply of the water 5 to be treated in the sludge amount control can be shortened. Therefore, the actual operation rate of the apparatus can be improved.

  According to the equation (4), the rate of decrease in the amount of sludge retained on the carrier surface is proportional to the endogenous respiration rate a. That is, the sludge reduction rate can be increased by increasing the endogenous respiration rate a. Endogenous respiration is due to an aerobic microbial reaction, and the rate is generally proportional to the temperature and oxygen concentration in the reaction layer.

  FIG. 6 shows an apparatus configuration for shortening the sludge reduction period using this principle. FIG. 6 is a side view of the reaction apparatus main body 102 shown in FIG. 3. In the plurality of reaction tanks 101 configured in the reaction apparatus main body 102, air from the blower 110 is supplied into the reaction tank 101 via the air supply pipe 111. Air supply means 112 is provided to be blown into the lower part. Further, the reaction tank 101 of the reaction apparatus main body 102 is provided with a heating means 114 comprising a heater 113 or a hot water pipe for heating each reaction tank 101. At this time, the heating means 114 can heat each reaction tank 101 independently, such as winding the outer periphery of each reaction tank 101 with a heater 113 or a hot water pipe, or passing a hot water pipe inside each reaction tank 101. Can be implemented in a method. Although FIG. 6 shows the case where the reaction tank 101 is provided with both the air supply means 112 and the heating means 114, only one of them may be provided.

  As described above, the air supply means 112 or the heating means 114 is provided in each reaction tank 101 to supply air to the reaction tank 101 that stops the supply of the water 5 to be treated for a certain period of time or to heat the reaction tank 101. Or by supplying air and heating at the same time promotes the action of the carrier surface holding sludge to be self-decomposed and reduced by microorganisms, thereby shortening the operation stop period of the reaction tank 101.

DESCRIPTION OF SYMBOLS 3 Carrier 5 Water to be treated 6 Treated water 8 Saturated area 100 Sprinkling water treatment device 101 Reaction tank 105 Water supply pipe 106 Treated water take-out pipe 107 Circulating water pipe 108 Treated water circulation pump 109 Circulating water 112 Air supply means 114 Heating means VA1 to VA5 Valves VB1 to VB5 Treated water valve VC1 to VC5 Circulating water valve

Claims (5)

  Provided with a sprinkling water treatment device having a plurality of reaction vessels in which a carrier to which aerobic microorganisms and sludge are fixedly attached is fixed on the surface and supplying the treated water to each of the reaction vessels, Performing aerobic water treatment, and stopping the supply of treated water to the reaction tank for a certain period before the amount of sludge retained on the carrier surface in the reaction tank increases due to the aerobic water treatment and reaches the saturation region, After the retained sludge is self-degraded by aerobic microorganisms and reduced in volume, the supply of treated water to the reaction tank is resumed, and the amount of sludge retained on the surface of the carrier in the reaction tank is increased by the aerobic water treatment and becomes saturated. The amount of sludge in the sprinkling water treatment system is characterized by repeating the operation of stopping the supply of treated water to the reaction tank for a certain period of time before reaching it, and performing this operation in a rotating manner for all reaction tanks Control method. The method for calculating the certain period of time to stop the supply of the water to be treated to the reaction tank before the amount of the carrier surface retained sludge in the reaction tank is increased by the aerobic water treatment and reaches the saturation region,
dX / dt = Xr + α × Sr−a × X _B
(Each symbol is as follows. X: amount of sludge retained on carrier surface in reaction vessel, t: time, Xr: amount of sludge trapped, Sr: amount of dissolved organic matter decomposed, X _B : amount of microorganisms in reaction vessel (image of X min), alpha: growth rate of X associated with soluble organic decomposition (= sludge conversion ratio), a: autolysis rate of X _B (= endogenous respiration rate))
In the formula
Xr: Sludge trapping amount = 0, Sr: Soluble organic matter decomposition amount = 0, obtained by substitution calculation, X: derived from the relationship between the amount of sludge retained on the carrier surface in the reaction tank and the elapsed time t The present invention relates to a method for controlling the amount of sludge in the watering type water treatment apparatus according to claim 1.   When restarting the supply of treated water again after stopping the supply of treated water to the reaction tank for a certain period of time, the treated water derived from the reaction tank along with the restart of the supply of treated water for each predetermined period. 3. The method for controlling the amount of sludge in a watering-type water treatment apparatus according to claim 1 or 2, wherein the sludge amount is returned to the inlet of the reaction tank.   Air supply means is provided in each reaction tank, air is supplied to the reaction tank that stops the supply of water to be treated, and promotes the action of the carrier surface holding sludge to be self-decomposed and reduced by microorganisms. The method of controlling the amount of sludge in the watering type water treatment apparatus according to claim 1 or 2. A heating means is provided in each reaction tank, the reaction tank for stopping the supply of water to be treated is heated by the heating means, and the action of reducing the amount of the carrier surface retained sludge by self-decomposition by microorganisms is promoted. The sludge amount control method in the watering type water treatment apparatus of any one of 1-4.

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