JPH01207187A - Treatment of waste organic water - Google Patents

Abstract

PURPOSE:To prevent clogging of a membrane occurring in turbid matter in a membrane sepn. treatment by adding an oxidizing agent to a liquid to be treated, then subjecting the liquid to the membrane sepn. treatment, thereby obtaining the anaerobic treated liquid having extremely high transparency. CONSTITUTION:The oxidizing agent such as sodium hypochlorite (NaClO) is properly injected form respective pipings 34, 35 into the treated liquid from a gas-liquid sepn. tank 8 and the circulating liquid from a membrane separator 12. The reduced sulfur in the anaerobic treated liquid is thereby oxidized and the turbidity by the reduced sulfur is eliminated, by which the transparency of the anerobic treated liquid is enhanced. As a result, the clogging of the membrane occurring in the turbid matter in the membrane sepn. treatment of a post stage is prevented, by which the permeating flux is maintained highly and stably and the frequencies of the membrane cleaning are decreased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for treating organic wastewater, and particularly to a treatment method in which organic wastewater is subjected to anaerobic treatment and then the resulting treated liquid is subjected to membrane separation treatment. The present invention relates to a method of preventing a decrease in permeation flux in a membrane separation treatment step and performing efficient treatment.

[Prior Art] As a method for treating organic wastewater such as various industrial wastewater and domestic wastewater, there is a biological treatment method that uses microorganisms. Among biological treatment methods, the anaerobic treatment method efficiently decomposes highly concentrated organic wastewater using anaerobic bacteria, and in particular, it is a method for recovering gas whose main component is methane gas generated by a methane production reaction. is attracting attention as an energy-saving waste liquid treatment method.

By the way, in the method of anaerobic biological treatment of organic wastewater, there is a problem that the reduced sulfur in the anaerobic treatment liquid turns into colloid and the treatment liquid becomes cloudy.

Conventionally, as a method to prevent such cloudiness due to reduced sulfur, methods have been proposed in which the anaerobically treated liquid is subjected to vacuum desulfurization or further aerobic biological filtration as a post-treatment ("Water Pollution Research JVO &.

10, No. 11 (1987) pp. 666-669)
.

On the other hand, recently, the anaerobic treatment liquid has a membrane fraction of 1ilt'A.
A method of removing anaerobic sludge and anaerobic SS remaining in the liquid by burying it in the liquid is being considered.

[Problems to be Solved by the Invention] However, none of the above methods has been able to achieve a sufficiently satisfactory effect, and in particular, in the method of treating the anaerobic treatment liquid with membrane fraction M, the membrane is damaged due to white turbidity. There was a problem in that the permeation flux was significantly reduced due to clogging, requiring frequent cleaning of the membrane.

The present invention effectively prevents white turbidity caused by reduced sulfur in an anaerobic treatment solution for organic wastewater, and also prevents a decrease in permeation flux and deterioration of membrane performance in the membrane separation process in the subsequent process. The purpose of the present invention is to provide a method capable of treating industrial wastewater.

[Means for Solving the Problems] The organic wastewater treatment method of the present invention is a method in which organic wastewater is anaerobically treated and the treated liquid is membrane-separated. The method is characterized in that after adding an oxidizing agent, an acid treatment is performed.

In the present invention, examples of the oxidizing agent added to the anaerobically treated water include sodium hypochlorite (NaCj20).
, ozone (03), chlorine (CI12), etc. can be used, but NaCILO is preferable in terms of handling and effectiveness.

The amount of the oxidizing agent added is appropriately determined depending on the type of oxidizing agent used, the quality of the water to be treated, the membrane material, the membrane separation treatment conditions, and the like. For example, when using NaCj20 as an oxidizing agent, the concentration of NaCj20 in the water to be treated that is subjected to acid content 11 treatment may generally be about 30 to 50 ppm, but if this does not produce a sufficient effect, - Temporarily NaCILO
It is preferable to implant at a concentration of 100 to 11,000 pp.

There is no particular restriction on the method of adding the oxidizing agent, and for example, the following method (1) or (2) may be employed.

■ Continuously or intermittently inject an oxidizing agent into the anaerobic treatment solution.

(2) Continuously or intermittently inject an oxidizing agent into the circulating fluid during acid treatment.

Note that it is extremely effective to use an antifoaming agent in combination to improve the effect of the oxidizing agent. In this case, an antifoaming agent is injected into the anaerobically treated liquid, specifically the methane reactor discharge liquid, the gas is separated, and an oxidizing agent is continuously or intermittently injected into the gas-separated liquid. .

[Function] According to the method of the present invention, by adding an oxidizing agent to the water to be treated that is subjected to acid content 1lIIA, the oxidizing agent oxidizes the reduced sulfur in the anaerobic treatment liquid, causing cloudiness due to the reduced sulfur, and This effectively prevents membrane clogging and reduction in permeation flux.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a system diagram showing an example of a treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention.

Organic waste liquid, e.g. C0Dcr concentration approximately 6500 mg
The waste liquid mainly containing 11 (glucose) of It is stored in the waste liquid adjustment tank 1, and after being sent to the heat exchanger 3 via the pipe 21 by the liquid supply pump 2 and temperature-adjusted, the waste liquid is first passed through the pipe 22. The acid is then fed to the first reaction 4w (acid generation tank) 4,
Processed to produce organic acids.

Next, the liquid is sent to the heat exchanger 6 via the piping 23 by the supply pump 5, and after temperature adjustment, the liquid is sent to the second reaction 4 via the piping 24.
ff (Feeded to methane reaction 4 and 7 for biodegradation treatment (
It! Temper treatment). In the second reaction tank 7, a part of the treatment liquid was circulated through a pipe 25. Note that in the heat exchanger 3.6, the liquid temperature is controlled by heat exchange with steam.

After anaerobic treatment, in order to separate the generated gas and treatment liquid, the gas and liquid components are separated using piping 26! ! 1 tank 8 for gas-liquid separation. During this feeding process, an antifoaming agent is added through the pipe 27. The gas mainly composed of methane separated in the gas-liquid separation tank 8 is treated in the desulfurization tower 9 and then discharged from the pipe 28 to the outside of the thread.

The anaerobic treatment liquid separated by the gas-liquid separation laI tank 8 is sent to the membrane circulation water tank IO through piping 29,30.

The liquid in the membrane circulation water tank 10 is supplied to the piping 3 by the liquid supply pump 11.
1 to the membrane separator 12 where it is subjected to membrane separation treatment,
Suspended substances such as anaerobic bacterial cells and anaerobic sludge are removed. The permeate from the membrane separation process is discharged as treated water to the outside of the system through piping 32, while the circulating liquid is returned to the membrane circulation water tank 10 through piping 33. In addition, in the membrane circulation water tank 10,
The concentrated sludge is periodically discharged from the pipe 36 to the outside of the thread.

In this embodiment, pipes 34 and 3 are connected to the treated liquid from the gas-liquid separation 418 and the circulating liquid from the membrane separation device 12, respectively.
Step 5, an oxidizing agent such as NaCJZO is appropriately injected.

As a result, in the past, 10
Approximately 20 ppm of reduced sulfur remained, which became cloudy and caused clogging of the membrane, but these problems were resolved, and the permeation flux of the membrane separation process was improved and the frequency of membrane cleaning was reduced.

A specific experimental example will be described below.

Experimental Example 1 (Example of the Present Invention) Using the apparatus shown in FIG. 1, organic wastewater was treated according to the method of the present invention.

The COD concentration of the waste liquid, treatment conditions, and capacity of each tank were as follows.

Waste liquid: Waste liquid mainly composed of sugar (glucose)
, 6500mg/Jl) Waste liquid flow rate = 250°C/h Waste liquid passage temperature: 35°C Antifoaming agent (Kuriless 5117) injection amount: 20mg/I NaCj! O injection amount: 3 omg/l (continuous injection) Membrane separation device (3 mm module between membranes) Separation membrane: Flat membrane type UF membrane Membrane area: 1.92 m2 Operating pressure: Inlet/outlet = 2.6/1.3 (kg) /cm
2) Circulating water flow rate: 17m3/h (2m/5ee) Temperature
: 35°C Capacity of each a waste liquid adjustment tank: 2 m3 First reaction tank = 1 m3 Second reaction tank: 4 m3 Gas-liquid separation tank: 200j2 Membrane circulation water tank: 200Il The quality of the obtained treated water is shown in Table 1.

Furthermore, Fig. 2 shows the change over time in the permeation flux of the membrane separator.

Experimental Example 2 (Comparative Example) Wastewater treatment was carried out in the same manner as in Example 1 except that NaCJ20 was not injected.

The results are shown in Table 1 and Figure 2.

Table 1 Experimental Example 3 (Example of the present invention) The circulating water flow rate of the membrane separator was set to 12 m'/h (1.4 m
/sec) Waste liquid treatment was carried out in the same manner as in Experimental Example 1 except that the procedure was as follows. Figure 2 shows the change over time in the permeation flux of the membrane separator.

Experimental example 4.5 (comparative example) The circulating water flow rate of the membrane separator was set to 15 m3/h (1.8 m/5
ee) (Experimental Example 4) or 10m3/h (1,2m/5e
c) Waste liquid treatment was carried out in the same manner as in Experimental Example 2 except that (Experimental Example 5) was carried out.

Figure 2 shows the change over time in the permeation flux of the membrane separator.

From Table 1, it is clear that according to the method of the present invention, an anaerobic treatment liquid with extremely high transparency can be obtained, and the water quality of the membrane separation treatment liquid is also significantly improved.

In addition, from Figure 2, in the conventional method (Experiment Example 2.4.5), the permeation flux rapidly decreases to 0.5 to in/sec after the start of operation due to the cloudiness of reduced sulfur; According to the method of the invention, since cloudiness is eliminated, the permeation flux is approximately 2 m /
It is clear that d a y is stable.

For this reason, in the conventional method, the membrane separation frequency of the membrane separation device was once a day, whereas in the method of the present invention, the frequency of cleaning the membrane is 4 to 4 times a day.
Membrane cleaning frequency can be significantly reduced to once every 5 days.

In Experimental Example 1, NaCuO was intermittently injected, and about 500 ml of NaCuO was added to the circulating water of the membrane separator every 2 to 3 hours.
It was found that similar effects can be obtained even when ppm is injected.

[Effects of the Invention] As detailed above, according to the organic wastewater treatment method of the present invention, cloudiness caused by reduced sulfur in the anaerobic treatment liquid is eliminated,
An anaerobic treatment liquid with extremely high transparency can be obtained. This prevents clogging of the membrane caused by white turbidity during the membrane separation process in the post-process, making it possible to maintain a high and stable permeation flux, reducing the frequency of membrane cleaning, and improving the quality of the treated water. will also be significantly improved.

Therefore, according to the method of the present invention, the treatment efficiency of organic wastewater is improved, and it is possible to obtain a high-quality treated liquid at low cost.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a treatment apparatus suitable for implementing the organic wastewater treatment method of the present invention. FIG. 2 is a graph showing the change over time in the permeation flux of the membrane separation apparatus obtained in Experimental Examples 1 to 5. 1... Waste liquid adjustment tank, 4... First reaction tank, 7...
- Second reaction tank, 8... Gas-liquid separation tank, 10... Membrane type ring tank, 12... Membrane separation device. Agent Patent Attorney Tsuyoshi Shige

Claims (1)

[Claims] (1) A method of anaerobically treating organic wastewater and membrane-separating the treated liquid, which comprises adding an oxidizing agent to the liquid to be treated and then subjecting it to membrane separation. Wastewater treatment methods.