JPS5929087A - Water treatment device - Google Patents

Abstract

PURPOSE:To provide a water treatment device which enables economical operation according to the fluctuation in the load of a liquid mixture by disposing a shallow vertical aeration tank and a deep vertical aeration tank in series and constituting the same in such a way that the original water to be treated and the return sludge from a flotation tank can be alternately supplied to both tanks. CONSTITUTION:A liquid mixture composed of the original water to be treated and activated sludge is flowed in series through the 1st vertical aeration tank 1 and the 2nd vertical aeration tank 2 or the liquid mixture is circulated only in the tank 2 in this water treatment device. When the load of the liquid mixture is large, the liquid mixture is flowed in series through the tank 1 and the tank 2. The water to be treated is supplied onto the tank 1 in this case, and the water is treated with the return sludge which is kept supplied to the tank 1 and the tank 2. The concn. of the substrate in the tank 1 is high and the amt. of dissolved oxygen is large while the concn. of the substrate is low in the tank 2; therefore, the high decomposing power for the substrate is obtd. over the entire part of the device in the case of using both tanks. The high treatment effect is thus obtd. with the whole device even if the tank 1 is constituted shallow.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water treatment device, and more particularly to a water treatment device equipped with a vertical aeration tank.

2. Description of the Related Art As a device for biologically treating and purifying sewage and industrial wastewater, a water treatment device using a so-called deep shaft method is known. This device has a vertical aeration tank (deep shaft) with a depth of 50 to 150 m, and this vertical aeration tank has an upward flow path and a downward flow path that communicate at the upper and lower parts of the tank, and This flow path is equipped with an air diffuser,
Biological treatment is performed by circulating a mixed solution (“raw water to be treated + activated sludge”, hereinafter the same shall apply) from the downward flow path to the upward flow path. By the way, the processing capacity of such a vertical aeration tank needs to be set based on the maximum value of pollution load as the product of pollution concentration and water volume. In addition, the pollution load in the mixed liquid, for example in the case of urban sewage, changes significantly seasonally, and in the case of industrial wastewater, it changes significantly economically depending on the presence or absence of operation. Therefore, if the pollution load decreases, the absolute circulation rate of the mixed liquid in the tank can be reduced slightly, but in order to continue the biological treatment, it is necessary to increase the oxygen-containing gas. It is necessary to circulate the mixed liquid at a speed that does not increase in the downward flow path, and for this reason, in equipment with a large processing capacity, it is necessary to circulate a larger amount of the mixed liquid than necessary even though the pollution load is significantly reduced. Therefore, instead of a large-capacity vertical aeration tank, two vertical aeration tanks of smaller capacity were connected in series. A type of device connected to JP-A-55-1398
This device, proposed as No. 98, performs treatment according to the pollution load by appropriately using two vertical aeration tanks, and has the advantage of being able to operate the device economically. ing.

The present invention was proposed as an improvement on such conventional equipment, and aims to take the content of the above-mentioned Japanese Patent Application Laid-Open No. 55-139898 one step further and provide an equipment that provides significant advantages in terms of construction cost and processing efficiency. It is something to do.

For this reason, the present invention consists of a first vertical aeration tank, a second vertical aeration tank, and a flotation tank, and the first vertical aeration tank is shallow and the second vertical aeration tank is shallow.
The vertical aeration tanks are configured deeply, and these aeration tanks are connected in series so that the mixed liquid can overflow from the upper part of the first vertical aeration tank to the second vertical aeration tank, and the floating tank is connected to the floating tank. The inlet of the outflow conduit is located in the middle of the ascending flow path of the second vertical aeration tank, and raw water to be treated and return from the flotation tank are sent to the first vertical aeration tank and the second vertical aeration tank, respectively. A supply system for supplying sludge is provided, and these supply systems include a flow path switching mechanism capable of selectively supplying raw water to be treated and return sludge to the first vertical aeration tank and the second vertical aeration tank. Its basic feature is that it has been attached.

In the range where the polluted substrate concentration of the mixed solution is high, the substrate decomposition rate of activated sludge is high, and in that case, even if the oxygen concentration in the liquid is not high, the oxygen absorption rate of microorganisms can be kept high, so the apparent substrate decomposition is Increased speed and efficient processing. On the other hand, when the substrate concentration of the mixed liquid decreases and it is purified to a state close to that of treated water, the rate of substrate decomposition within the microorganisms decreases, and in order to increase the apparent rate of substrate decomposition, the oxygen concentration in the liquid must be increased. According to the research of the present inventors, it is effective to increase the amount of dissolved oxygen by deepening the tank. It has been found that by using a specific collection/separation mechanism, the load on the construction of the aeration tank can be reasonably reduced while maintaining the same throughput and load fluctuation compatibility as conventional equipment.

In other words, in the inlet aeration tank (first tank) in a system in which two vertical aeration tanks are connected in series, the concentration of polluted substrate is high, so even if the tank is not deepened to increase the dissolved oxygen concentration, the apparent In order to increase the rate of substrate decomposition, this is a shallow aeration tank, and in the outlet aeration tank (second tank), the concentration of pollutant substrate is low, so a large amount of dissolved oxygen is required, so a shallow aeration tank is used. It is a deep aeration tank that can obtain a dissolved oxygen concentration, and in particular, as a mechanism for discharging treated water to the outside of the tank and separating activated sludge, it is possible to collect high-concentration activated sludge and supply it to the aeration tank. By adopting the outflow conduit and flotation tank using the method shown in Japanese Patent Application Laid-Open No. 56-110193, the treatment capacity of the entire device is secured, while the construction of the inlet tank (first tank) is This is designed to reasonably reduce the burden.

Hereinafter, the present invention will be described with reference to the drawings. 1st
The figure shows the basic configuration of the present invention, in which (1) is a first vertical aeration tank, (2) is a second vertical aeration tank, (3) is a flotation tank, and (3) is a flotation tank. 1) and the second tank (2) are arranged in series so that the mixed liquid can overflow from the upper part of the first tank (1) to the second tank (2).

The first vertical aeration tank (1) includes the open head tank (4), a downward flow path (5), and an upward flow path (6). This aeration tank (1) is configured to be shallower than the second tank (2). Downflow path (5) and upflow path (6)
A diffuser (7) (7') is installed in the tank to supply oxygen-containing gas into the liquid. Diffuser (7') for ascending channel (6)
The upper channel acts as an air lift pump.

The second vertical aeration tank (2) is an airtight head tank (
8), a downward flow path (9) and an upward flow path (10). This aeration tank (2) is deeply configured to increase the amount of dissolved oxygen in the liquid, and like the first tank, an aeration device (11) is installed in the middle of the descending channel (9) and the ascending channel (10). (11)
is located. The air diffuser (11) causes its upper flow path to function as an air lift pump.

Further, the flotation tank (3) has a function of floating and separating activated sludge from the treated water and recovering the same.
An outflow conduit (12) is led from the second tank (2), and the inlet of the outflow conduit (17) is connected to the ascending channel (10) of the second tank.
It is located in the middle of. The flotation tank (3) utilizes the fact that the gas dissolved in the liquid in the aeration tank forms fine bubbles and adheres to the sludge, exerting buoyancy on the sludge. The inlet of 13) is located in the middle of the ascending channel (10), and the treated water is allowed to flow out into the flotation tank (3) while still containing a large amount of dissolved gas. Note that this flotation tank (3) generally also has a function for recovering activated sludge that has settled within the tank. 2nd above
The head tank of the vertical aeration tank (2) is of an airtight type in this embodiment. By making the tank airtight, the mixed liquid in the tank is pressurized by the oxygen-containing gas discharged from the diffuser (11) (11'), and its dissolved oxygen concentration is increased. It goes without saying that this head tank can be of an open-top type like the first tank.

Raw water can be supplied to the first tank (1) and the second tank (2), respectively. In the present invention, both tanks are basically used for polymerization with a large pollution load, and the second tank (2) is used when the pollution load is small. Therefore, in the former case, the first tank (2) is used. (1), and in the latter case, the raw water can be supplied to the second tank. In addition, the return sludge collected in the flotation tank (3) is also
and second tanks (1) and (2), respectively. Therefore, the supply system for these raw water and return sludge is equipped with a flow path switching mechanism (not shown) to enable them to be alternatively supplied to either of the two tanks.
is attached.

The depth of the vertical aeration tank in the present invention is determined by the depth of the second
It is preferable that the tank (2) is 100 m or more. Further, the first tank (1) having a small depth can be selected in a range of 50 m or more and less than 100 m. Further, the amount of dissolved gas in the aeration tank is at its maximum at a depth of 60 to 70 m, and therefore the inlet of the outflow conduit (12) is preferably located at this depth. Note that (13) is a compressor for aeration.

Fig. 2 shows a more specific embodiment based on the basic configuration shown in Fig. 1, in which the tip of the inflow conduit (14) for the mixed liquid into the second tank (2) has a U-shape in the middle of the tank. The outlet (141) is located in the ascending channel (10).

More specifically, the outlet (141) is located above the inlet (121) of the outlet conduit (12).

(15) is a mixing tank, and in this mixing tank (15), the first
The overflow mixture (or raw water) from the first tank (1) and the activated sludge from the flotation tank (3) are mixed and fed to the second tank (2) through the inlet conduit (14). Therefore, the overflow mixed liquid from the first tank (1), raw water, and return sludge from the flotation tank (3) can be supplied to the mixing tank (15), respectively. Note that the supply system for raw water and return sludge in this embodiment is also equipped with a flow path switching mechanism (not shown) that can selectively supply them to the first and second tanks. Needless to say.

In addition, the air diffuser (10') on the upward flow path side is connected to the inflow conduit (10').
14) is disposed within the U-shaped upright tip.

According to the water treatment device of the present invention as described above, water treatment is performed while appropriately using the first vertical aeration tank (1) and the second vertical aeration tank (2) in response to load fluctuations. The main modes of use are to flow the mixed liquid in series across the first tank (1) and the second tank (2), and to flow the mixed liquid only in the second tank (2). There is a way to use it in circulation. First, when the load of the mixed liquid is large, the first tank (1)
In this case, the raw water to be treated is supplied only to the first tank (1), and the returned sludge is passed through the first and second tanks. (1) and (2)
When the first and second tanks are used in series in this way, the substrate concentration is high in the first tank (1), and the substrate concentration is low in the second tank (2). Because the amount of dissolved oxygen is high at the expense of low oxygen content, the device as a whole can achieve high substrate decomposition capacity, and therefore the entire device has high processing efficiency despite the shallow structure of the first tank (1). can be obtained.

In addition, when the load of the mixed liquid is small, the first tank (1)
It is possible to stop the supply of raw water to be treated and return sludge to the second tank (2) and carry out treatment while supplying these only to the second tank (2). In this case, the deep aeration tank (2) and the floating Tank (3
), it is possible to perform effective treatment under high dissolved oxygen content and activated sludge concentration.

According to the present invention described above, economical operation is possible according to load fluctuations of the mixed liquid, and the first tank can be made shallow while ensuring sufficient processing capacity.
This has the effect that the construction cost, which largely depends on the depth of the tank, can be improved compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the basic configuration of the present invention. FIG. 2 is an explanatory diagram showing a more integrated embodiment based on the basic configuration of FIG. 1. In the figure, (1) and (2) indicate a vertical aeration tank, (3) a flotation tank, and (12) an outflow conduit.

Claims (1)

[Claims] Consisting of a first vertical suction tank, a second vertical aeration tank, and a flotation tank, the first vertical aeration tank is shallow and the second vertical aeration tank is deep. The upper part of the first vertical aeration tank is connected in series to allow overflow to the second vertical aeration tank, and the inlet of the outflow conduit to the flotation tank is connected to the second vertical aeration tank.
A supply system is provided, which is located in the middle of the upward flow path of the vertical aeration tank, and supplies raw water to be treated and sludge returned from the flotation tank to the first vertical aeration tank and the second vertical aeration tank, respectively. , these supply systems are equipped with flow path switching machines that can selectively supply raw water to be treated and return sludge to the first vertical aeration tank and the second vertical aeration tank. Device.