JPH0143597B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for operating an activated sludge aeration tank, and more specifically, the present invention relates to a method for operating an activated sludge aeration tank. The present invention relates to a method for controlling temperature and temperature in parallel.

As is well known, the activated sludge treatment method is a method that uses bacteria to decompose harmful components contained in wastewater and render them harmless.It has been developed primarily as a sewage purification technology, but recently it has also been used in the general chemical industry. We are getting good results.

For example, spray water waste liquid (generally called gas liquid) used for cooling coke oven gas in coke manufacturing plants contains large amounts of cyanide and phenol. is being used.

FIG. 1 is a process explanatory diagram illustrating this gas liquid activated sludge treatment method. Gas liquid A collected in a gas liquid pit 1 is once sent to a gas liquid tank 3 using a pump 2 for storage, and then transferred to a pump 4. It is then sent to the aeration tank 5. Reference numeral 6 denotes a flow rate control valve, and its opening degree is adjusted according to the signal from the flow rate controller 6', so that a set flow rate can be obtained, so that a predetermined amount of gas is always kept in the aeration tank 5. liquid is supplied. Also, aeration tank 5
In order to dilute the gas liquid to a predetermined concentration and to adjust its temperature, a predetermined amount of dilution water such as seawater is supplied by a flow control valve 7 and a flow rate regulator 7'.

Activated sludge, which is a collection of bacteria, is recharged in the aeration tank 5, and by mixing it under aeration with a stirring device 9, harmful components in the gas liquid are biologically decomposed and rendered harmless. Excretes to the rear. In the figure, 5' is a thermometer for detecting the temperature inside the aeration tank 5, and arrow S indicates steam injection for temperature control, which will be described later.

By the way, it has been confirmed that the ability to remove harmful substances in activated sludge treatment is significantly affected by the living environment of the bacteria, especially the temperature and concentration of the treated water. and concentration must be strictly controlled.
The concentration of the substance to be treated in the gas liquid (raw water) is
Since the variation is only within an allowable range and can be considered to be almost constant, the concentration can be controlled by controlling the concentration of the gas liquid, which is the raw water in the treated water. The following concentration refers to the raw water concentration in the treated water. However, in the conventional method as described above, only a flow rate control method is performed in which the flow rate of dilution water is set while monitoring the temperature of the aeration tank 5 with a thermometer 5'. If dilution water with large fluctuations is used, temperature control cannot be performed accurately. Moreover, if temperature is the main focus, concentration control becomes insufficient, and in any case, it is difficult to obtain optimal biological reaction conditions. To deal with this problem, there is a method of controlling the temperature by blowing steam S into the aeration tank 5, but this requires a considerable economic burden on piping and steam generation equipment. Moreover, this method can only be applied in seasons when the temperature of the treated water tends to be low, such as in the winter, and when the temperature of the dilution water and aeration air are high, such as in the summer, the optimum temperature for aeration must be determined as described below. Blow-in steam is actually counterproductive, as it often causes the material to evaporate. Therefore, there is a need for the development of a technique that can accurately control the gas liquid concentration and temperature in treated water without relying on such auxiliary means.

The present inventors have focused on the above-mentioned circumstances and have conducted research to develop a method that can simultaneously control gas liquid concentration and temperature with a relatively simple configuration. We focused on the fact that in normal treatment plants, in addition to general industrial water that is not heated, there is a large amount of industrial water that is used for cooling in various equipment and heated through heat exchange. I got the idea that if both were used together as dilution water, the temperature could be easily controlled.

The present invention was completed as a result of intensive research in order to realize this idea, and its configuration is such that when raw water is diluted with dilution water and supplied to an aeration tank for activated sludge treatment, the dilution water is preheated. The gist lies in controlling the concentration and temperature of the raw water in the treated water by using both high-temperature water and non-preheated water and controlling the ratio of the two used.

The configuration and effects of the present invention will be described below based on drawings showing embodiments, but the drawings are representative examples and do not limit the present invention.

FIG. 2 is a schematic process diagram showing an embodiment of the present invention.
The gas liquid etc. is sent to the gas liquid tank 3 via the gas liquid pit 1 and the pump 2 and stored therein in the same manner as described above. In the figure, 14 is a heat exchange type cooler,
It is provided to cool the gas liquid to a predetermined temperature in advance, and a flow rate control valve 15 is provided in the flow path of the cooling water for heat exchange to detect the gas liquid temperature behind the cooler 14 and control the flow rate. The flow rate of the cooling water is adjusted by the action of the indicator controller 15' for indicating the opening degree of the control valve 15 so that the temperature of the gas liquid is lowered to a predetermined temperature. This heat exchange lowers the temperature of the gas liquid in advance,
This is an auxiliary means to narrow the temperature control range of the gas-liquid dilution step that will be performed later, and is particularly effective when the temperature of the dilution water is high, such as in the summer, but should be omitted in the winter when the dilution water is at a low temperature. You can also do it.

The gas liquid stored in the gas liquid tank 3 is pumped to the pump 4.
The supply pipe is supplied to the aeration tank 5 by a control valve 6 connected to a flow rate control controller 6' and operated.
is provided, and the amount of gas liquid fed to the aeration tank 5 is maintained at a preset amount.

In the present invention, as dilution water for diluting this gas liquid, for example, cold seawater (10 to 32°C) taken directly from the sea is used.
temperature) and heated seawater used for cooling in the factory (30°C).
~45℃ or higher). As the water for dilution, the most economical water may be selected depending on the location conditions, such as seawater, lake water, river water, industrial water, etc. The temperature of each of the seawaters mentioned above fluctuates within the above-mentioned temperature ranges depending on the season, operating conditions, etc., but under no circumstances should cold seawater become hotter than warm seawater. Therefore, by adjusting the usage ratio of cold seawater and warm seawater, the temperature can be freely adjusted while keeping the total seawater flow rate (ie, the dilution rate of the gas liquid) constant. That is, each supply pipe for cold seawater C and warm seawater H is provided with flow rate control valves 10 and 11, respectively.
The opening degrees of these are adjusted in accordance with instructions from the control device 13, as will be described later. The supply pipes are arranged to join downstream of the control valves 10 and 11, and are supplied to the aeration tank 5 after being adjusted to a predetermined temperature and flow rate. It is also possible to supply the gas to the aeration tank 5 after merging it into the pipe and mixing it with the gas liquid.

The control device 13 calculates a mixing ratio of cold seawater C and warm seawater H so that the mixed seawater has a predetermined temperature, and operates each control valve 10 and 11 so that a predetermined amount of mixed seawater is obtained at the mixing ratio. When the temperature inside the aeration tank 5 is higher than the target temperature set in advance on the temperature indicator controller 5'',
The temperature of the mixed seawater is lowered by increasing the opening of the cold seawater flow control valve 10 and decreasing the opening of the warm seawater flow control valve 11, while the temperature in the aeration tank 5 is lower than the set temperature. At this time, the opening degree of the cold seawater flow rate control valve 10 is decreased and the opening degree of the warm seawater flow rate control valve 11 is increased to increase the temperature of the mixed seawater. In this case, a predetermined mixed seawater flow rate is set in the mixed seawater flow rate control valve 12, and the openings of the control valves 10 and 11 are adjusted to satisfy this flow rate, so that the seawater is eventually supplied to the aeration tank 5. Both the temperature and flow rate of the mixed seawater are set to target values.

As a result, the temperature of the treated water and the gas liquid temperature in the aeration tank 5 can always be maintained within the optimum range,
High processing efficiency is guaranteed.

FIG. 3 is a partial process explanatory diagram showing another embodiment of the present invention, which is particularly suitable when the capacity of the aeration tank 5 is extremely large. That is, when a large-capacity aeration tank 5 is used, if the gas liquid and mixed seawater are directly supplied, it will take time for the two to disperse, which may cause temperature and concentration distributions within the aeration tank 5. However, as shown in Fig. 3, a mixing tank 8 is placed in front of the aeration tank 5, a predetermined amount of gas liquid and mixed seawater are introduced into the mixing tank 8, and the temperature and concentration of the treated water are controlled at this stage. By supplying this to the aeration tank 5, the above-mentioned non-uniformity in temperature and concentration can be eliminated. In this case, the temperature and gas liquid concentration in the mixing tank 8 may be controlled in exactly the same manner as in the example shown in FIG.

The present invention is roughly configured as described above, and by using cold water and hot water together as dilution water, the temperature and concentration of treated water can be precisely controlled, and the optimum temperature for biological reactions caused by activated sludge can be achieved. As a result, the processing efficiency can be stabilized at a high level. In addition, there is no need for heating steam blowing equipment, which is an auxiliary temperature control means installed in the aeration tank, and the heat exchange water that is discharged after being used for cooling in various equipment in the factory can be effectively used as hot water. Since this method involves almost no economic burden, it is an extremely practical method.

Next, examples of the present invention will be shown.

Example 1 55 m ³ /hr of gas liquid was diluted with 120 m ³ /hr of mixed seawater to obtain 175 m ³ /hr of treated water, and the temperature in the aeration tank was set to 30 m 3 /hr.
When performing activated sludge treatment while maintaining the temperature at ℃, the temperature and concentration during treatment were controlled according to the method shown in FIG. Figures 4A and 4B are system diagrams showing the temperature balance in this case.

First, in the summer when the outside air temperature is high, the temperature of both warm seawater and cold seawater is relatively high (warm seawater: about 45℃, cold seawater: about 32℃), and the gas liquid (the temperature at the outlet of gas liquid pit 1 is about 70℃). ) is diluted with the above-mentioned mixed seawater of warm seawater and cold seawater, the target temperature in the aeration tank 5 cannot be set to 30°C, so the gas liquid temperature is lowered to 30°C by the cooler 14. Next, set the temperature of the temperature indicating controller 5″ installed in the mixing tank 8 to 31.5°C.
Gas liquid is supplied to the mixing tank 8 at a rate of 55 m ³ /hr, and the control device 13 controls the cold/hot water flow rate control valve 1.
Mixed seawater was supplied at a rate of 120 m ³ /hr while adjusting the opening degrees of 0 and 11. In this case, the temperature of the mixed seawater was 32°C, and the temperature of the water to be treated in the mixing tank 8 showed a stable value of approximately 31.5°C. When this treated water was introduced into the aeration tank 5 and activated sludge treatment was carried out while supplying aeration air at about 29°C, the temperature of the treated water was always stable at 30°C. The temperature balance at this time is as shown in FIG. 4A.

Next, in winter when the outside air temperature is low, warm seawater is about 30°C and cold seawater is about 10°C, both of which are low temperatures, so the gas liquid at about 70°C is left in the mixing tank 8 without being cooled by the cooler 14. The temperature was controlled while supplying In this case, the temperature of the aeration air is low (approximately 5°C) and the temperature of the water to be treated in the aeration tank 5 drops considerably, so the set temperature of the temperature indicator controller 5'' in the mixing tank 8 is set to a considerably high 42°C. By setting this, the temperature of the water to be treated in the aeration tank 5 could be kept constant at 30°C.The temperature balance at this time is as shown in Figure 4B.

Although the above example shows control in summer and winter, when the outside temperature is in the middle of the range, such as in spring or autumn, the necessity of operating the cooler 14 and the temperature indicator controller 5'' are adjusted accordingly. By appropriately setting the set temperature, the temperature of the treated water in the aeration tank 5 can be maintained at 30°C.Also, even when the temperature of the gas liquid fluctuates, the temperature in the aeration tank can be maintained according to the above method. can be easily set as desired.The method of the present invention can be used in any activated sludge method that targets high-temperature raw water.

[Brief explanation of drawings]

Fig. 1 is a process explanatory diagram showing an example of controlling treated water in conventional activated sludge treatment, Fig. 2 is a process explanatory diagram showing an embodiment of the present invention, and Fig. 3 is a process diagram showing another embodiment of the present invention. Part process explanatory diagrams, FIGS. 4A and 4B are system diagrams showing temperature balance in the example. 1... Gas liquid pit, 3... Gas liquid tank, 5... Aeration tank, 6, 7, 10, 11... Flow rate control valve, 5''...
Temperature indicating controller, 8...mixing tank, 9...mixing device.

Claims (1)

[Scope of Claims] 1. When raw water is diluted with dilution water to become treated water and supplied to an aeration tank for activated sludge treatment, preheated high-temperature water and non-preheated water are used together as dilution water,
A method for operating an activated sludge aeration tank characterized by controlling the concentration and temperature of raw water in treated water by controlling the ratio of use of both. 2. A method for operating an activated sludge aeration tank according to claim 1, in which seawater is used as dilution water.