WO2008041765A1

WO2008041765A1 - Method of treating organic drainage

Info

Publication number: WO2008041765A1
Application number: PCT/JP2007/069553
Authority: WO
Inventors: Shigehiro Suzuki; Motoharu Noguchi; Koichiro Kando
Original assignee: Ngk Insulators, Ltd.
Priority date: 2006-10-05
Filing date: 2007-10-05
Publication date: 2008-04-10
Also published as: JP2010012362A

Abstract

A method of treating an organic drainage whereby a change in the qualities of water in a tank, which is a biological treatment tank provided with a separation membrane outside the tank, toward the deterioration of the membrane filtration performance can be exactly grasped without resorting to any special measurement instrument and thus the clogging of the membrane surface can be prevented. The dissolved organic carbon concentration (DOC) or soluble chemical oxygen demand (S-COD) of water in the tank is measured. When the measured value increases and exceeds a definite level, a coagulant is added. The DOC can be measured with a TOC meter after removing SS in the water in the tank with a filter paper. The S-COD can be measured with a COD meter after removing SS in the water in the tank with a filter paper. With an increase in the measured dissolved organic carbon concentration or soluble chemical oxygen demand, the coagulant may be added in an increased amount.

Description

Specification

Organic wastewater treatment method

Technical field

The present invention relates to a method for treating organic wastewater by a membrane separation activated sludge method, in which a separation membrane is installed outside a biological treatment tank and the water in the tank is filtered.

Background art

[0002] Activated sludge treatment using biological treatment tanks has become widespread as a method for treating various organic wastewater such as sewage, return water, industrial wastewater, waste leachate, human waste, agricultural wastewater, livestock wastewater, and aquaculture wastewater. ing. Conventionally, the water in the biological treatment tank was separated into activated sludge and supernatant water in a gravity sedimentation basin, and the supernatant water was taken out as treated water. However, since the gravitational sedimentation basin requires a large site area and requires a long time for sedimentation separation, the membrane separation activated sludge method using a separation membrane instead of the gravitational sedimentation basin has recently become widespread.

[0003] In the membrane separation activated sludge method, the separation membrane is installed outside the biological treatment tank and the solid-liquid separation is performed while circulating the water in the tank, and the separation membrane is placed inside the biological treatment tank. It can be broadly divided into a tank-mounted type that immerses and filters the water in the tank directly. In any of these cases, when the quality of the water in the tank deteriorates, the clogging of the membrane proceeds rapidly, and operation may become impossible.

[0004] Therefore, for example, in Patent Document 1, there is a risk of blockage in the case of the membrane separation activated sludge process installed in the tank! Therefore, a method for preventing clogging of the film surface by adding a flocculant is disclosed. This method is suitable for the fall when the temperature gradually falls, and it is difficult to apply this method for other seasons.

V, and the target was limited to the installation type in the tank!

[0005] Note that Patent Document 1 also describes determining the risk of clogging by measuring the filtration amount of water in the tank using a filter paper, or by measuring the sugar concentration. However, measuring the amount of filter paper filtration must be done manually! /, Which increases the burden on workers at sewage treatment plants. On the other hand, the sugar concentration can be measured automatically. However, it is not possible to install it in a sewage treatment plant, etc., because it is a water quality analysis item in ordinary wastewater treatment and the measuring device is expensive. It's not easy. Patent Document 1: JP-A-2006-55766 (Claims 1 and 2)

Disclosure of the invention

Problems to be solved by the invention

[0006] The present invention has solved the above-mentioned conventional problems, and has changed the direction in which the membrane filtration performance is deteriorated due to various factors such as the hydropower, raw water quality, and water temperature of the biological treatment tank in which the separation membrane is installed. It is an object of the present invention to provide an organic wastewater treatment method capable of accurately grasping this water quality change without introducing a special measuring instrument and preventing the membrane surface from being clogged.

Means for solving the problem

[0007] The present invention made to solve the above-mentioned problems is a method for treating organic wastewater by membrane filtration of the in-vessel water of a biological treatment tank with a separation membrane installed outside the tank! It is characterized by measuring the soluble organic carbon concentration or the soluble chemical oxygen demand of internal water, and adding a flocculant when the measured value rises above a predetermined value. Note that there are two methods for measuring the amount of dissolved chemical oxygen (S-COD): a measurement method using potassium permanganate as an oxidizing agent and a measurement method using potassium dichromate. You can use the method V, and you can use a method that conforms to the measurement method for V.

The invention's effect

[0008] According to the present invention, the solubility organic carbon concentration (DOC) or the dissolved chemical oxygen demand (S-COD), which is a water quality analysis item in normal wastewater treatment, is measured and measured. The film surface is prevented from being blocked by adding an aggregating agent when the value rises above a predetermined value. This DOC or S-COD accurately shows the membrane filtration performance of the water in the tank, is easy to measure automatically with existing measuring equipment, and adds a flocculant when the measured value rises above the specified value. Thus, the fine particles that cause the membrane blockage can be aggregated to prevent the membrane surface from being blocked in advance.

Brief Description of Drawings

FIG. 1 is a flowchart showing an embodiment of the present invention.

Explanation of symbols [0010] 1 Anaerobic tank

2 First oxygen-free tank

3 First aerobic tank

4 Second oxygen-free tank

5 Second aerobic tank

6 Separation membrane

7 Circulation path

8 DOC or S—COD measuring instrument

9 Flocculant addition device

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] Embodiments of the present invention will be described below.

Fig. 1 is a diagram showing an example of a treatment facility that performs denitrification and dephosphorization of sewage that is organic wastewater. 1 is an anaerobic tank, 2 is a first anaerobic tank, 3 is a first aerobic tank, and 4 is a The second anaerobic tank, 5 is the second aerobic tank. In the treatment method using such a tank configuration, phosphorus in raw water is excessively taken up by microorganisms and dephosphorization proceeds. In addition, the denitrification effect is further enhanced by arranging the combination of anaerobic tank and aerobic tank in two stages. The first aerobic tank 3 and the second aerobic tank 5 are biological treatment tanks that perform activated sludge treatment.In this embodiment, a separation membrane 6 is installed outside the second aerobic tank 5 in the subsequent stage. The water in the second aerobic tank 5 is circulated to the separation membrane 6 through the circulation path 7, membrane-filtered by the cross flow method, and taken out as treated water.

[0012] The present invention is not limited to the treatment method with the tank configuration shown in Fig. 1. Standard activated sludge method, nitrification solution circulation method, anaerobic aerobic method (AO method), anaerobic anaerobic aerobic method It can be widely applied to ordinary membrane separation activated sludge methods such as (A20 method) and their multistage methods. In addition, raw water is not limited to sewage, and various organic wastewater such as return water, factory wastewater, waste leachate, human waste, agricultural wastewater, livestock wastewater and aquaculture wastewater can be used as raw water.

[0013] As the separation membrane 6, a ceramic or polymer MF membrane or UF membrane having a membrane pore diameter of 0.01 to 5 m can be used. The membrane shape may be any monolithic membrane, tubular membrane, flat membrane, hollow fiber membrane, etc. The pressurization method may be either an external pressure type or an internal pressure type. In this embodiment, a ceramic monolith membrane manufactured by the applicant company having a channel having a round cross section is used. ing. The MLSS in the second aerobic tank 5 circulated through the separation membrane 6 is appropriately in the range of 3000-20000 mg / L. Below this range, the biological treatment capacity becomes insufficient. Not suitable for membrane filtration.

[0014] In this embodiment, the soluble organic carbon concentration (DOC) or the dissolved chemical oxygen demand (S-COD) of the water in the tank of the second aerobic tank 5 which is the final biological treatment tank is Measure with measuring instrument 8. Measurement is preferably performed automatically, but manual measurement is also acceptable. The soluble organic carbon concentration measured in the present invention is a value obtained by removing the organic carbon content in SS from the total organic carbon concentration (TOC). The dissolved chemical oxygen demand is the value excluding the chemical oxygen demand in SS as well as the chemical oxygen demand (COD) power. TOC and COD are water quality analysis items for normal wastewater treatment, and are routinely measured at general sewage treatment plants.

[0015] In this embodiment, after removing SS from the water in the tank using filter paper, DOC is measured using a TOC meter, or S-COD is measured using a COD meter. When the value rises above the predetermined value, the flocculant is added from the flocculant adding device 9. The type of flocculant is not particularly limited. It can be an inorganic flocculant such as PAC (polyaluminum chloride) or ferric chloride, or a polymer flocculant.

[0016] Specifically, when the in-water DOC of the second aerobic tank 5 is usually about 10 to 20 mg / L, the membrane filtration performance did not decrease, but when it exceeded 30 mg / L, the membrane filtration performance The above-mentioned predetermined value is set in the range of 10 mg / L to 30 mg / L, and the flocculant is added when the measured value exceeds this value. It is preferable. Also, the amount of flocculant added can be gradually increased as the measured value increases. The DO C concentration mentioned here varies depending on the raw water to be treated.

[0017] When S-COD (Mn) is used as an index, when the S-COD (Mn) of the water in the second aerobic tank 5 is usually about 10 to 30 mg / L, the membrane filtration performance is low. If the force does not decrease, i.e., exceeds 35 mg / L, the membrane filtration performance deteriorates and the membrane surface of the separation membrane 6 is blocked, so the above specified value is within the range of 10 mg / L to 35 mg / L. Setting power to add flocculant when measured value exceeds this value is preferable. Also, the amount of flocculant added can be gradually increased as the measured value increases. The S-COD (Mn) concentration mentioned here is the raw water to be treated ' It depends on the flow. The concentration is also different when S-COD (Cr) is used as an index.

[0018] It has not been known that DOC and S-COD affect membrane filtration performance. In the present invention, DOC or S-COD is used as an index of membrane filtration performance, and when it rises above a predetermined value, a flocculant is added, so that clogging is easy. Aggregates the fine particles to prevent clogging of the membrane surface.

Example

[0019] Sewage was treated in the experimental apparatus having the tank configuration shown in Fig. 1, and the relationship between the D OC in the tank of the second aerobic tank and the membrane filtration performance by the separation membrane was confirmed. The DOC was measured using a “TOC_5000” type TOC meter manufactured by Shimadzu Corporation after removing SS in the water in the second aerobic tank with filter paper. When DOC was around 10 mg / L, membrane filtration was successful. When the membrane filtration performance of the tank water gradually deteriorates due to various factors such as water strength, water quality, and water temperature, the DOC measurement value of the tank water in the second aerobic tank will exceed 40 mg / L. The membrane permeation flux of the separation membrane was greatly reduced from 3 m / day to 2 m / day. Therefore, when flocculant was added to the second aerobic tank at a rate of 1 to 3 mg / L per inflow, the DOC of the water in the tank decreased to 20 to 30 mg / L, and the membrane permeation flux of the separation membrane was It recovered to 2.8m / day.

[0020] In the experimental apparatus having the tank configuration shown in FIG.

The relationship between COD (Mn) and membrane filtration performance with a separation membrane was confirmed. S-COD (Mn) was measured by removing the SS in the water in the second aerobic tank using filter paper and using a DR / 850 multi-item rapid water quality analyzer manufactured by HACH. . When S—COD (Mn) was around 15 mg / L, membrane filtration was successful. However, when the membrane filtration performance of the tank water gradually deteriorated due to various factors such as raw water quality and water temperature, the S-COD (Mn) measurement value of the tank water in the second aerobic tank was 40 mg / Over L, the membrane permeation flux of the separation membrane decreased significantly from 3 m / day to 2 m / day. Therefore, when flocculant was added to the second aerobic tank at a rate of! ~ 3mg / L, the S-COD (Mn) of the water in the tank decreased to 20-30mg / L, and the separation membrane The membrane permeation flux recovered to 2.8 m / day.

Claims

The scope of the claims

[1] Organic wastewater treatment method in which the water in the biological treatment tank is filtered through a separation membrane installed outside the tank! /, The dissolved organic carbon concentration (DOC) or dissolution of the water in the tank A method for treating organic wastewater, characterized by measuring sex chemical oxygen demand (S-COD) and adding a flocculant when the measured value rises above a predetermined value.

[2] The method for treating organic waste water according to claim 1, wherein the amount of the flocculant added is increased in accordance with an increase in the measured value of the soluble organic carbon concentration or the dissolved chemical oxygen demand. .