JP3067241B2 - Sewage treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewage treatment apparatus, and more particularly to a sewage treatment apparatus for treating sewage using a rotating disk.

[0002]

2. Description of the Related Art Conventionally, activated sludge has been generally used for treating sewage and other organic wastewater.
The rotating disk method has attracted attention and has been put to practical use. The rotating disk method is a type of biological wastewater treatment technology that purifies wastewater by using microorganisms that have adhered and propagated on the surface of the disk.The activated sludge method is not suitable for the biological oxidation of organic pollutants. Although they are based on the same basic principle, they differ fundamentally in the method of ingesting organic matter and the method of absorbing oxygen. In other words, the activated sludge method aims to contact microorganisms and organic substances and supply oxygen by means such as forced aeration with a blower, whereas the rotating disk method achieves this purpose by alternately bringing microorganisms into contact with wastewater to the atmosphere. Play.

[0003] When a disk is mounted so that about 40% of its area is immersed in an oxidation tank, and water is continuously supplied while slowly rotating the disk, various microorganisms adhere and grow on the surface of the disk. As the disks forming the so-called biofilm rotate, the biofilm comes into contact with the wastewater in the oxidation tank, absorbing organic pollutants and carrying the wastewater into the air. These wastewaters form a film and absorb oxygen while falling on the biofilm surface,
The biofilm absorbs oxygen and organic contaminants from the film. The wastewater is purified by the action of such a biofilm, while the absorbed organic pollutants are oxidized and decomposed and stabilized.

[0004] The thickness of a biofilm in a steady state varies depending on conditions, but is usually about 2 to 4 mm. The biofilm develops gradually as the purification of the wastewater proceeds, but the excess microorganisms are periodically stripped off by the shearing forces acting on the biofilm as the disc passes through the wastewater. These exfoliated microorganisms overflow the oxidation tank, are separated by a solid-liquid separator, and are entirely taken out of the system as excess sludge.

As shown in FIG. 4, a general sewage treatment apparatus using the rotating disk method comprises a treatment tank 3 having an initial sedimentation basin 1, a four-axis four-stage rotating disk 2, a final sedimentation basin 4 It is in the form of lining up. 5 and 6 show the structure of the rotating disk device, where 5 is a rotating body having a stirring blade 6, 7 is a main shaft, 8
Is a bearing, 9 is a reduction gear, 10 is an oxidation tank as a processing tank, 11
Is the cover.

That is, as shown in FIGS. 5 and 6, the structure of the rotating disk device includes a rotating body, a driving device, an oxidation tank, a cover, and the like. The rotating body is composed of a main shaft and a disk attached to the main shaft at regular intervals (usually 18 to 30 mm). The drive unit consists of an electric motor, a speed reducer, a transmission chain, a sprocket, etc. The sprocket mounted on the outlet shaft of the speed reducer and the transmission chain drive the transmission sprocket fixed to the main shaft of the rotating body to rotate the disk. . The rotation speed varies depending on the concentration of the inflowing raw water, the purpose of the treatment, and the like.
It is determined in the range of m / min.

The rotating disk method has the following characteristics as compared with the activated sludge method.

(1) The operating power cost is low. (2) Maintenance is easy and does not require advanced operation management technology. (3) A high purification rate can be obtained in a short contact reaction time, and it is strong against load fluctuation. (4) The amount of generated sludge is small. (5) A wide range of treatment of raw water quality from high concentration to low concentration is possible. (6)
Nitrification and denitrification are easy, and dephosphorization is also possible.

The rotating disk method does not require advanced operation control techniques such as the activated sludge method, but the design is an important factor in terms of the success or failure of the treatment. It will be about something. Variable speed rotating disk devices according to the load amount are available, but it cannot be said that rational rotation speed control is performed.

[0010]

The most important design factor of a rotating disk device is a load condition, and the load per unit area of a biofilm becomes the basis of the design. One of the factors is a biochemical element requirement (BOD). ) There is area load. The BOD area load is represented by the amount of BOD applied per disk unit area per day, and its unit is gBOD / m ² · day.

The BOD area load is limited by the oxygen supply capacity of the device. The upper limit varies depending on the type of drainage. For example, in the case of sewage, 40 to 50 gB
OD / m ² · day. When the BOD area load exceeds this upper limit, the tank becomes anaerobic and causes odor. Normal design (BOD removal rate is expected to be 90% or more)
Although the BOD area load varies depending on the substrate, it is generally determined in the range of 5 to 20 gBOD / m ² · day.

The rotational speed of the disk needs to be determined in consideration of the amount of oxygen supplied, the mixing and stirring of the oxidation tank, the amount of microorganisms adhering to the disk and the periodic removal of excess microorganisms, and the economics (power consumption). There is. Increasing the rotation speed increases the oxygen supply,
In addition, mixing and stirring in the tank is advantageous, but the type of the microorganism membrane becomes difficult and the power consumption increases. On the other hand, if the speed is extremely low, it is advantageous in terms of power consumption, but the supply of oxygen and the stirring in the tank are insufficient, and the removal of excess microorganisms is incomplete, resulting in a reduction in processing efficiency.

[0013] In the rotating disk method, the main role of purification is microorganisms attached to the disk. The microorganisms on the disc are drained
It begins to attach thinly in a few days, and then forms a dense brown biofilm in about a week. The thickness of the biofilm is determined by the properties of the incoming wastewater and the load. The higher the concentration and the higher the load, the thicker the biofilm. Therefore, when the apparatus is operated in a multi-stage system, the most biofilm is formed on the first-stage disc in contact with the raw water, and the amount decreases as purification proceeds.

In consideration of the above-mentioned points, it is reasonable that the rotational speed of the disk is high in the first stage, and is slowed down later. When there is a load fluctuation, it is desirable that the rotation speed of the disk is variable according to the load.

However, conventional means for measuring loading conditions include biochemical element demand (BOD), chemical oxygen demand (COD) and microbial activated sludge suspended on a disk (MLSS), activated sludge. Organic suspended matter (MLVSS)
However, it is impossible to control the rotation speed of the disk rationally in accordance with the inflow load fluctuation every moment because of the time and the difficulty of the automatic measurement.

The BOD area load in the rotating disk method is equivalent to the BOD volume load in the standard activated sludge method, and does not express the F / M ratio. Just as the F / M ratio is an important operation control factor in the standard activated sludge process, it can be said that the F / M ratio should be considered in the rotating disk process. The F / M ratio in the rotating disk method can be determined by measuring the quality of the influent water, peeling off the biofilm on the disk, and measuring the dry weight.

In the example of measuring the F / M ratio of the rotating disk method,
The first stage biofilm dry weight is 194 g / m ² , which corresponds to MLVSS 40.000-60.000 mg / l. As described above, since the rotating disk method has a large amount of microorganisms, the F / M ratio is smaller than the standard activated sludge method of about 0.3.
0.01 to 0.05, which is about 1/10. It is considered that the reason why the rotating disk method can obtain a high removal rate by short-time contact and is relatively strong against the fluctuation of the water quality of the raw wastewater is that the F / M ratio is lower than that of the activated sludge method.

The MLSS and MLVSS measured by peeling off the biofilm of the rotating disk and drying or igniting do not accurately represent microorganisms, but also include undegraded organic matter and dead microorganisms in the influent water. Although it is impossible to know the amount of negative microorganisms, it is possible to know the F / M ratio more accurately by using an index having a high correlation with the amount of active microorganisms contributing to purification. Also, by selecting and measuring a water quality index that has a correlation with the F / M ratio and can be easily and automatically measured, the amount of inflow load is known, and the disk rotation speed can be controlled according to the load condition, thereby improving the quality of treated water. And power savings can be expected.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a sewage treatment apparatus by a rotating disk method capable of obtaining good treated water quality with little variation in treated water quality. .

[0020]

According to the present invention, in order to achieve the above object, a part of a rotating disk is immersed in water to be treated which has flowed into an oxidation tank, and the rotating disk is rotated to rotate the disk. In a sewage treatment apparatus for generating a biofilm on the surface of a rotating disk and purifying the water to be treated by the biological film, an oxidation-reduction potentiometer for measuring an oxidation-reduction potential in the oxidation tank, Adenamine-3 per unit area of biofilm formed
A means for measuring the value of phosphoric acid, a flow meter for measuring the amount of inflowing water flowing into the oxidation tank, a measurement value of the oxidation-reduction potential of the oxidation-reduction potentiometer, an adenamine-3-phosphate value per unit area of the biofilm Using an arithmetic expression based on the measured flow rate and the flow rate measurement value, the inflow water CODcr, which is the oxygen consumption of the inflow water by potassium chromium oxide, the inflow BOD, which is the biochemical oxygen demand of the inflow water, and the biochemical oxygen demand. The present invention is characterized in that it is constituted by arithmetic control means for calculating the BOD area load and the peripheral speed of the rotating disk, and controlling the rotating speed of the rotating disk in accordance with the calculated peripheral speed.

[0021]

The present invention belongs to the control of the rotation speed of a disc in the spinning method of organic wastewater, in which an ORP meter is installed in an oxidation tank, the biofilm of the disc is stripped, and the AT per biofilm unit area is reduced.
Measure P and measure inflow and ORP, ATP,
Inflow water CODcr, inflow B from the inflow measurement value using an arithmetic expression
Calculate OD, BOD area load, peripheral speed of rotating disk,
The rotation speed of the rotating disk is adjusted so as to reach the calculated peripheral speed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a sewage treatment apparatus according to an embodiment of the present invention. Reference numeral 12 denotes a rotating disk provided so as to be partially immersed in water to be treated in an oxidation tank 10 which is a treatment tank.
3 is a flow meter for measuring the amount of water flowing into the oxidation tank 10, 14
Is an oxidation-reduction potential (ORP) meter, 15 is adenamine-3-
A phosphoric acid (ATP) meter 16 is an arithmetic and control unit.

In the above sewage treatment apparatus, the ORP meter 14
Measures the oxidation-reduction potential of the liquid in the oxidation tank 10, and the ATP meter 15 peels off the biofilm on the disc 12 and manually or automatically operates the ATP within a certain area of the biofilm by TCA extraction and luciferyl luciferase method. (Adenamine-3
-Phosphoric acid) content is measured. The arithmetic and control unit 16 is ORP
The F / M ratio, which is the ratio of the microorganism (M) to the organic matter (F), the biochemical oxygen demand (BOD), or the chemical oxygen using the arithmetic expression from the measured value and the ATP measured value or the ORP measured value and the flow rate value The required amount (COD) area load and the disk speed are calculated, and a disk speed signal is transmitted to the rotating disk device. The rotation speed of the disk is controlled according to the load condition.

When measuring the ATP content of the biofilm, it is necessary to measure the area of the portion peeled off from the disk 12. Assuming that this area is A (cm ² ) and the measured value of ATP is B (μ mole), the ATP content C per unit area of the biofilm (μmole /
m ² ) is calculated by equation (1).

C (μ mole) = B (μ mole) × 10.000 / A (cm ² ) (1) CODcr · ATP load which is one of the expression methods of the F / M ratio by the standard activated sludge method Has a correlation with the ORP, and the relational expression (2) is obtained from data analysis of continuous laboratory experiments using artificial sewage.

ORP (mV) =-427.52 CODcr
ATP load (g / μmole / day) +182.6
... (2) where the correlation coefficient r = −0.8977 and the number of samples n
= 32. Since both the standard activated sludge method and the rotating disk method are based on the same basic principle in terms of the biological oxidation of organic pollutants, it is considered that the equation (2) holds for the rotating disk method.

The CODcr · ATP load in the rotating disk method can be defined as in equation (3).

CODcr · ATP load (g / μ mole · day =
{Influent CODcr (mg / liter) × 10 ⁻³ × inflow water (liter / day)} / {ATP content per biofilm unit area (μ mole / m ² ) × disc area (m ² )}
... (3) CODcr · ATP calculated from ORP using equation (2)
The inflow CODcr is calculated by substituting the load, the measured value of the ATP content per unit area of the biofilm, the disk area, and the amount of the inflow into the expression (4) obtained by modifying the expression (3).

Inflow water CODcr (mg / liter) = ｛C
ODcr · ATP load (g / μmole · day) × ATP content per biofilm unit area (μ mole / m ² ) × disc area (m ² )
(4) The inflow water CODcr (oxygen consumption by potassium dichromate) has a correlation with the BOD for the same type of wastewater, and the inflow water BOD is calculated by equation (5).

Inflow water BOD (mg / liter) = inflow water CODcr (mg / liter) × k (constant)
(5) The BOD area load of the rotating disk 12 is calculated by the equation (6).

BOD area load = ｛influent BOD (mg /
Liter) × 10 ⁻³ × inflow water volume (liter / day)｝ / rotating disk area (m ² ) ………………………………………………………………………………… (6) When the relationship between the BOD area load and the peripheral speed was investigated from the operation data of a plurality of (14 treatment plants) rotating disk full-scale treatment facilities, the relationship shown in FIG. 2 was obtained, and the equation (7) was used as the correlation regression equation. was gotten.

Peripheral speed = 0.393 × BOD area load (g / m ² · day) +13.7 (7) (r = 0.72)
22, n = 14) The peripheral speed is calculated by substituting the BOD area load into the equation (7). Therefore, by measuring the ORP of the oxidation tank and the ATP content and the flow rate of the biofilm, the BOD area load is calculated, and it is possible to control the peripheral speed according to the load.

In the system, ATP measurement is performed by MLS
Although it is easier than S or MLVSS, it is inevitable that the area of the peeled biofilm must be measured, so that it becomes considerably complicated. However, in the steady state, it is considered that the ATP content of the biofilm does not change suddenly, so the ATP measurement does not need to be performed so frequently, and when calculating the peripheral velocity of the disc from the ORP measurement value, ATP content can be calculated by substituting previous measurements.

Although the reliability is reduced, it is also possible to calculate the peripheral speed of the disk from only the measured value of ORP and the measured value of flow rate. In this case, the ATP measurement mechanism is omitted from the system configuration of FIG.

From the data analysis of the continuous continuous experiment of the standard activated sludge method, the ORP and the CODcr volume load have a relationship as shown in FIG. 3, and the equation (8) was obtained as a correlation equation.

ORP = −174.7 × CODcr volume load + 222.4 (8) (mv) (r = −0.6247, n = 32) CODcr volume load from ORP using equation (8) Is calculated. Further, the inflow CODcr is calculated by substituting the CODcr volume load and the flow rate into the equation (9).

Inflow water CODcr (mg / liter) = CO
Dcr volume load (g / liter · day) × 10 ³ / inflow water volume (liter / day) (9) Further, by using equations (5) and (6), the BOD area load is calculated, and (7) The peripheral speed of the disk is calculated by using the equation. As described above, the peripheral speed of the disk can be rationally controlled based on the ORP, the biofilm ATP content, the inflow water amount, or the ORP and the inflow water amount.

[0039]

As described above, the present invention has the following effects.

It is known that the rotational speed of the rotating disk has a large effect on the processing efficiency. The system recognizes the change of the load condition every moment, and can control the rotation speed to an appropriate value according to the load condition. Therefore, the fluctuation of the treated water quality is small and a good treated water quality can be obtained.

Although the rotation speed and the required power depend on the disk shape, they are proportional to the square of the speed or the 2.5th power, so that power consumption can be suppressed by controlling to an appropriate rotation speed according to the load condition. This has the effect of reducing power consumption.

The rotating disk is purified at a later stage and the load is reduced, and the ORP is also increased accordingly. Therefore, the rotating speed is decreased at the later stage, which matches the actual operating condition.

In the case of the constant flow rate operation, the rise of the ORP
Since it is related to the increase in the OD concentration, even when the measurement of ATP is omitted, the rotational speed of the disk that can be practically used can be controlled only by the measurement of the ORP.

[Brief description of the drawings]

FIG. 1 is a block diagram of a sewage treatment apparatus according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a BOD area load and a peripheral speed of the sewage treatment apparatus according to the embodiment of the present invention.

FIG. 3 shows CODcr of a sewage treatment apparatus according to an embodiment of the present invention.
FIG. 4 is a characteristic diagram showing a relationship between a volume load and an ORP.

FIG. 4 is a configuration diagram of a sewage treatment apparatus using a rotating disk method.

FIG. 5 is a side view of the rotating disk device.

FIG. 6 is a front sectional view of a rotating disk device.

[Explanation of symbols]

10 oxidation tank, 12 rotating disk, 13 flow meter, 14
ORP meter, 15: ATP meter, 16: Operation control device.

Claims (4)

(57) [Claims] 1. A part of a rotating disk is immersed in water to be treated that has flowed into an oxidation tank, and the rotating disk is rotated to form a biofilm on the surface of the rotating disk. In the sewage treatment apparatus for purifying the water to be treated, an oxidation-reduction potentiometer for measuring an oxidation-reduction potential in the oxidation tank, and adenamine-3 per unit area of a biofilm formed on the rotating disk.
A means for measuring the value of phosphoric acid, a flow meter for measuring the amount of inflowing water flowing into the oxidation tank, a measurement value of the oxidation-reduction potential of the oxidation-reduction potentiometer, an adenamine-3-phosphate value per unit area of the biofilm Using an arithmetic expression based on the measured flow rate and the flow rate measurement value, the inflow water CODcr, which is the oxygen consumption of the inflow water by potassium chromium oxide, the inflow BOD, which is the biochemical oxygen demand of the inflow water, and the biochemical oxygen demand. A sewage treatment apparatus comprising: an arithmetic control unit that calculates a BOD area load and a peripheral speed of the rotating disk, and controls a rotating speed of the rotating disk in accordance with the calculated peripheral speed. 2. A part of a rotating disk is immersed in the water to be treated flowing into the oxidation tank, and the rotating disk is rotated to form a biofilm on the surface of the rotating disk. In the sewage treatment apparatus for purifying the water to be treated, an oxidation-reduction potentiometer for measuring an oxidation-reduction potential in the oxidation tank, and adenamine-3 per unit area of a biofilm formed on the rotating disk.
Means for measuring the value of phosphoric acid, a flow meter for measuring the amount of inflowing water flowing into the oxidation tank, a measurement value of the oxidation-reduction potential of the oxidation-reduction potentiometer, an adenamine-3-phosphate content per biofilm area, and Using an arithmetic expression based on the measured flow rate, the inflow CODcr, which is the amount of oxygen consumed by the indium chromium oxide, the inflow BOD, which is the biochemical oxygen demand of the inflow, and the BOD, which is the biochemical oxygen demand. A sewage treatment apparatus comprising an arithmetic control unit for calculating an area load. 3. A part of a rotating disk is immersed in the water to be treated flowing into the oxidation tank, and the rotating disk is rotated to form a biofilm on the surface of the rotating disk. In the sewage treatment apparatus for purifying the water to be treated, an oxidation-reduction potentiometer for measuring an oxidation-reduction potential in the oxidation tank, and adenamine-3 per unit area of a biofilm formed on the rotating disk.
A means for measuring the value of phosphoric acid, a flow meter for measuring the amount of inflow water flowing into the oxidation tank, a measurement value of the oxidation-reduction potential of the oxidation-reduction potentiometer, adenamine-3-phosphate value per unit area of the biofilm Using an arithmetic expression based on the measured flow rate and the flow rate, the inflow CODcr, which is the oxygen consumption of the inflow water by potassium chromium oxide, the inflow BOD, which is the biochemical oxygen demand of the inflow, and the biochemical oxygen demand. A sewage treatment apparatus comprising a calculation control means for calculating a BOD area load and controlling a rotation speed of the rotating disk in accordance with the calculated BOD area load. 4. An oxidation-reduction potentiometer for measuring an oxidation-reduction potential in an oxidation tank, a flowmeter for measuring an amount of inflowing water flowing into the oxidation tank, and a calculation based on a measurement value of the oxidation-reduction potential of the oxidation-reduction potential meter. Using the equations, the influent CODcr, which is the amount of oxygen consumed by the indium chromium potassium oxide, the influent BOD, which is the biochemical oxygen demand of the influent, and the BOD area load, which is the biochemical oxygen demand, are calculated. A sewage treatment apparatus comprising arithmetic and control means for controlling the rotation speed of the rotating disk in accordance with the calculated BOD area load.