JPS6316097A - Treatment of organic waste water - Google Patents

Abstract

PURPOSE:To efficiently and stably treat organic waste water by separating it into a liquid which permeats a membrane and a liquid which does not permeat therethrough by means of an ultrafiltration membrane and subjecting the liquid which has permeated the membrane to anaerobic treatment. CONSTITUTION:Raw water is fed to a UF membrane filtering stage 2 via an introduction pipe 1, and incorporated SS and high molecular organic substances are separated. The liquid which has permeated through the membrane is fed to a UASB reaction tank 4 via a discharge pipe 3 thereof and organic substances contained in the liquid are subjected to methane fermentation by granules 5 of methane fermentation bacteria. The treated liquid wherein organic substances have been removed is discharged to the outside of the system via a discharge pipe 8 thereof. The liquid which has not permeated and contains. SS and soluble high molecular organic substances separated by the UF membrane is transferred to a dehydration treating stage 10 via a pipe 9 and subjected to a flocculating treatment by a flocculating agent and thereafter concentrated and dehydrated. Thereby an extremely high-load treatment can be performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to upward flow of industrial wastewater such as food processing wastewater, human waste water, and other organic wastewater containing floating and soluble polymeric organic substances. Type anaerobic sludge bed method (UASB method) t-
The present invention relates to a method for efficiently performing anaerobic treatment using the method.

[Technical background of the invention]

UASB@ performs methane fermentation by forming and depositing granules of methane bacteria at the bottom of an anaerobic reaction tank.

Unlike the conventional method of dispersing methane bacteria in the liquid by mixing metal inside the tank, UASB @ allows the raw water to flow upward from the bottom of the tank without mixing inside the tank, thereby creating a dense methane-proofing system at the bottom of the tank. This is to form a granule with a diameter α of 5 to 5 m. The concentration of methane bacteria in the sedimentary layer of such granules is extremely high, making it possible to carry out extremely high-load methane fermentation treatment.
It is limited to low-molecular compounds of a certain degree or less, and cannot decompose high-molecular organic substances. Other anaerobic bacteria floating in the reaction tank are used to reduce the molecular weight of high-molecular organic substances, but the floating bacteria are temporary and flow out of the reaction tank together with the effluent, so the bacterial cell concentration is reduced. The rate of molecular weight reduction in the UA8B reactor is low compared to the rate of methane production.

In this way, the process of lowering the molecular weight becomes rate-limiting for the removal of high-molecular organic substances from wastewater, and the high-load processing function inherent in the UASB method cannot be utilized efficiently. The disadvantage of the primary UASB method is that if the inflow water contains a large amount of SS (suspended solids), the granules will float and flow out along with the SS that adheres to methane gas, HCo, and gas bubbles and becomes scum. Was that.

Granules have an extremely slow growth rate, so once they flow out, it takes a long time in the casing for the amount necessary for treatment to be re-formed, making treatment impossible during that time.

[Purpose of the invention]

An object of the present invention is to provide a method for efficiently and stably performing high-load anaerobic treatment using the UASB method.

[Structure of the invention]

The present invention provides a method for anaerobically treating organic wastewater by the UASB method.
A method for treating organic wastewater, characterized in that the membrane permeate and non-permeate are separated by a membrane) to separate and remove floating and soluble polymeric organic substances, and the membrane permeate is treated anaerobically by the UAEIB method. It is.

Next, the present invention will be explained based on the drawings.

The raw water is supplied to the UP membrane f filtration step 2 through the raw water introduction pipe 1, and the organic SS and high molecular weight organic substances are separated. The membrane permeate is supplied to the UASB reaction tank 4 via the membrane permeate discharge pipe 3, and the organic matter U in the membrane permeate is subjected to methane fermentation by the methane-fermenting bacteria Granule 5 deposited at the bottom of the UASB reaction tank, resulting in methane gas produced. is collected by the methane gas collection section 6 at the upper part of the UA8B reaction tank and discharged to the outside of the tank via the pipe 7. On the other hand, the treated liquid from which organic matter has been removed is discharged at t8.
It is discharged to the outside of the thread. SS separated by UP membrane
The non-permeate liquid containing soluble organic polymers is transferred to a dehydration process 10 through a pipe 9, where it is flocculated by a flocculant, concentrated, and dehydrated. The dehydration method may be any method such as centrifugal dehydration, roll dehydration, pressure dehydration, or vacuum dehydration. It may be directly transferred to the UASB reaction tank 4 via the dehydration separation*12 pipe 11, or it may be mixed with the treated water 8 after aeration and then discharged.

If the non-permeate has a bad odor or appears to be putrid, aeration may be performed before dehydration.

This improves cohesiveness and dehydration, and reduces the intensity of bad odors. The flocculant used in the dehydration treatment step 10 is
Organic polymer flocculant (polymer) may be used, but
When there are many soluble organic polymers, using an inorganic flocculant such as chloride sulfate, ferric chloride, or slaked lime can effectively coagulate and dehydrate the soluble organic substances. The process of the present invention can be made simpler if non-permeable Rat-transfer can be carried out to another wastewater treatment facility different from the raw water 1. Furthermore, if the raw water contains coarse SS that would block the UP membrane flow path, it is preferable to remove the coarse 8S in advance using a screen or the like, and then treat it in the dehydration treatment step 10. When using a UP membrane with a molecular weight cut-off of approximately 15,000, it is possible to obtain permeate t-hours of 40 to 50 t/- at a membrane average pressure of 3 iyf/cw' and a membrane surface flow rate of 2.0 m/sec. .

On the other hand, the capacity of the UA8B reaction tank is BOD 10,000w
To treat y7t of wastewater, a 1.0 day retention period is required at a water temperature of 30C. For example, BOD 10,
In the treatment of wastewater containing low-molecular-weight organic matter of about 0.000 m/m, a 100-m UF membrane and a 100 m" UA8B reaction tank are required. Also, at UASB@, a water temperature of t-2 is required.
It is important to process at a medium temperature of 0°C to 40111:O. As a countermeasure in the winter when the water temperature drops, it is desirable to have heating equipment attached that uses methane gas.

Example 1 Synthetic wastewater was subjected to anaerobic treatment at a water temperature of 53° C. using a cylindrical UASB reaction tank with a fermentation section volume of 2 tons.

Solubility BOD and solubility C0Dor of synthetic wastewater are each 1
2.0001+9/t, 52,000”P/L
70% of C0Dcr is organic matter with a molecular weight of 15,000 or more.

In carrying out the present invention, firstly, a solution containing α3% lactic acid and acetic acid and yeast extract, etc.
2 of the effective volume at the bottom of the UASB reaction tank.
Proliferate and deposit 0% ((L12) granules,
From this point on, the synthetic wastewater contains fibrous sst'' of 1,000
．． Anaerobic treatment was performed at a rate of 2 tons/day using sample raw water prepared by adding 5,000.10,000 capes/day. As a pretreatment, 17F (molecular weight cut off: 15,000f) and sand filtration were used. The results are shown in t-i1.

The results in Table 1 show the amount of gas generated per day after 10 days of flowing synthetic wastewater.

Pre-treatment with sand filtration and no pre-treatment h, ss
It is shown that the amount of gas generated decreased because the granules floated up as the generated gas rose and the amount of deposition decreased. The backwash liquid of sand filtration and the liquid containing SS and soluble polymer substance t-gold captured by UFF filtration are coagulated with Fect3 and an organic polymer flocculant (polymer), and then dehydrated with a filter press. Dehydrated P liquid t-t
7A8B reactor. Although the sand-filtered water applied for pretreatment was clear and free of SS, it adhered to the generated gas on the methane bacteria granules, rose, and flowed out.

On the other hand, granules did not emerge when Uy@rt was applied.

If there is a high-molecular organic substance that cannot be removed by sand filtration even if it is soluble, the methane bacteria granulules will strongly adhere to the generated gas bubbles, and the floating bubbles will be stabilized and will not burst easily. This is confirmed.

〔Effect of the invention〕

ill Since the organic matter in the wastewater that flows into the UASB reaction tank is only those that are compatible with methane fermentation, it is possible to perform extremely high-load processing, and the 0t21UP membrane, which can fully utilize the original functions of the UASB method, is used to remove colloids. By increasing the adhesion of granules and air bubbles and selectively removing stabilizing soluble polymeric organic substances, it is possible to prevent granules from floating or flowing out in the UASB reaction tank. .

[Brief explanation of drawings]

FIG. 1 is a flow diagram for explaining one embodiment of the present invention.

Claims (1)

[Claims] 1. In a method for anaerobically treating organic wastewater by an upflow anaerobic sludge bed method, the organic wastewater is filtered through an ultrafiltration membrane to remove floating and soluble polymeric organic substances in the wastewater. 1. A method for treating organic wastewater, which comprises separating a membrane permeate liquid and a non-permeate liquid, which are separated and removed, and subjecting the membrane permeate liquid to anaerobic treatment by the UASB method.