JPS5915714B2 - Wastewater treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for biologically purifying wastewater, and in particular to a method for supplying oxygen and a method for circulating water in a wastewater treatment apparatus using fixed biofilms.

As conventional biological wastewater treatment methods, the activated sludge method and the sprinkling P bed method are known as representative methods.

However, these methods have the following problems.

(1) Operation and management require a high degree of skill and skill, and especially in the activated sludge method, strict control of returned sludge is required.

(2) The activated sludge method has problems such as the tendency to cause bulking, and the sprinkled F-bed method has problems such as generation of F-bed flies and odor.

(3) Regarding BOD and ammonia, they are 20pp
It is difficult to obtain treated water of less than m.

The immersion-type fixed biofilm method is also known, which solves the problems of the activated sludge method and the sprinkled P bed method described above. The biological treatment of wastewater is carried out by supplying the oxygen necessary for oxidizing BOD or nitrogen components in the wastewater.

A typical example of this device is shown in Figure 1.
A module 2 and an aeration chamber 3 are provided in the main body 1, a raw water injection line 4, a treated water discharge line 5, and an air injection line 6.
The structure is as follows.

Pebbles, plastic plates, plastic tubes, etc. are used as modules for attaching organisms.

Circulation of water within the module is achieved by providing an aeration chamber in the center or side of the module, and by introducing air from the lower part of the aeration chamber to achieve the effect of an air lift pump.

The wastewater is purified by bringing the circulated wastewater into contact with microorganisms attached to the module surface.

However, the conventional immersion type fixed biofilm method had the following drawbacks.

(a) If a module with low resistance to the circulating water flow is used, it tends to cause drifting, and as a result, the dead space of the module becomes a dog, which may deteriorate the processing performance.

(b) If a module with high resistance to circulating water flow is used, it may easily become clogged, making water circulation difficult and reducing treatment efficiency, so it is very important to select a module that is appropriate for the water quality. It's difficult.

(c) When the amount of wastewater to be treated increases, a large amount of oxygen is required to be supplied.

However, if the air flow rate is increased in order to increase the oxygen supply, the water circulation speed will also increase, and as a result, microorganisms attached to the module may be easily peeled off and the processing efficiency may deteriorate.

In this way, it is quite difficult to control the quality and quantity of wastewater, the amount of air blowing, and the amount of circulating water.

Therefore, the present inventors aimed to eliminate the above-mentioned drawbacks of the immersion-type fixed biofilm method, especially the drawback (c). The present invention has been completed by discovering a method for obtaining stable water quality even when there are fluctuations in the ammonia concentration in wastewater and the amount of water by controlling the amount of circulating water.

That is, the present invention provides a method for treating wastewater using a fixed biofilm type wastewater treatment device in which a module filling part and an aeration chamber are separate bodies, in which the amount of air sent to the aeration chamber is adjusted based on the detection of the ammonia concentration and flow rate of raw wastewater. The present invention relates to a wastewater treatment method characterized in that the amount of circulating water is adjusted and the amount of circulating water is controlled to a constant value by a flow rate indicating controller installed in a circulating water line from a module filling section to an aeration chamber.

The present invention will be explained in more detail with reference to FIG.

The immersion type fixed biofilm device is composed of an aeration chamber 1, a main body 2, a module 3, an aeration device 4, and a module support plate 5.

The raw wastewater is injected into the aeration chamber 1 from line P1, and due to the effect of the air lift pump of air supplied from blower B1 through line P5, it flows into the main body 2 of the device through line P2, and the module section 3 is It passes in a downward flow.

At this time, the wastewater is purified by the action of microorganisms attached to the module.

The wastewater that has passed through the module flows into the aeration chamber 1 again via line P3, receives oxygen supply from the aeration device 4, flows into the device body 2, and circulates between the aeration chamber 1 and the device body for a certain period of time. After being purified, the treated water outflow line P
4 leaks out of the system.

The present invention consists of incorporating the following control system into the above-mentioned immersion type fixed biofilm device.

That is, the ammonia concentration in the raw wastewater is detected by the ammonia concentration detector AE, and the numerical value indicated by the concentration indicator AI is input to the calculator CC.

Next, the flow rate detector FBI detects the inflow of raw wastewater,
The numerical value indicated by the flow rate indicator FI is input to the calculator CC.

A calculation unit CC calculates the required amount of air from the relationship between the ammonia concentration and the flow rate, and the signal is sent to the air adjustment valve V-1 to adjust the amount of air.

When the amount of air changes, the water flow rate in the aeration chamber changes, and as a result, the amount of circulating water also changes.

This relationship is expressed as follows.

q2 (V+△V)・S・ε ■ Q−v−8・(1−ε) ■ q: Air volume V: Water flow rate in the aeration chamber S: Aeration chamber area △V: Rising speed of bubbles ε: Void Ratio Q: Circulating water amount To adjust the circulating water amount, use the flow rate detector FE2 in the circulating water line P3.
The system is designed to maintain the amount of circulating water at a certain constant value by controlling valve V-2 using a flow rate indicator controller FIC.

That is, in the present invention, no matter how much the amount of air changes, the amount of circulating water does not change.

The present invention provides the following effects.

(1) Stable water quality can always be obtained despite fluctuations in the ammonia concentration and water volume of raw water.

(2) By automating the operation, the labor required for equipment management is significantly reduced.

(3) Since the amount of circulating water can be controlled, there is no need to worry about microorganisms attached to the module coming off and deteriorating treatment efficiency.

Example Domestic wastewater having a raw water ammonia concentration of 30 to 100 ppm was treated at a water temperature of 10 to 30 DEG C. and a treatment rate of 1 rrL'/hour using a submerged fixed biofilm device having the following structure.

The air flow rate was controlled as follows.

The amount of circulating water was controlled as follows.

Test results - When air volume and circulating water volume were not controlled As can be seen by comparing the test results above, controlling air volume and circulating water volume was extremely effective against fluctuations in the ammonia concentration of raw water. You can see that it's big.

■When controlling

[Brief explanation of drawings]

FIG. 1 shows an overview of the immersion type sessile biological treatment apparatus, and FIG. 2 shows an overview of the method of the present invention.

Claims (1)

[Claims] 1 In a wastewater treatment method using a fixed biofilm wastewater treatment device in which the module filling part and the aeration chamber are separate, the amount of air fed to the aeration chamber is adjusted based on the detection of the ammonia concentration and flow rate of raw wastewater. A wastewater treatment method characterized in that the amount of circulating water is controlled to a constant value by a flow rate indicating controller installed in a circulating water line from a module filling part to an aeration chamber.