JPS6365949A - Treatment of oil-containing waste water - Google Patents

Abstract

PURPOSE:To efficiently treat oil-containing waste water by a small-sized apparatus, by including and immobilizing bacteria having oil component decomposing capacity by a gel mixture of a hydrophilic polymer substance and a hydrophobic polymer substance and contacting the bacteria including and immobilizing gel obtained with oil-containing waste water. CONSTITUTION:Bacteria having oil component decomposing capacity is included and immobilized by a gel prepared by mixing a hydrophilic polymer substance and a hydrophobic polymer substance and the resulting bacteria including and immobilizing gel is contacted with oil-containing waste water to decompose the oil component of said waste water. As the bacteria having the oil component decomposing capacity, there is activated sludge collected from the aeration tank of the activated sludge treatment apparatus of the waste water from an oil refining factory and subjected to conditioning culture using heavy oil A. The quantity of the oil component decomposing bacteria included and immobilized by the gel prepared by mixing the hydrophilic and hydrophobic polymer substances is pref. set to 1-100g (dry bacteria wt. basis) per 1l of gel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating oil-containing wastewater using microorganisms having the ability to decompose oil.

[Conventional technology]

Nowadays, environmental pollution issues are being seriously questioned, water quality regulations are becoming increasingly strict, and oil-containing wastewater is also becoming a serious subject.

In general, oil in wastewater can be roughly divided into three types: floating oil that floats on the water surface, dispersed oil that is dispersed as oil droplets in water, and emulsified oil that is emulsified due to the coexistence of surfactants, etc. can do.

Among these, floating oil can be easily removed by scraping or scooping up on the water surface, so separation and disposal of dispersed oil and emulsified oil are the main targets of oil treatment in wastewater.

Conventionally, methods for treating dispersed oils and emulsified oils include flotation separation methods, centrifugation methods, agglomerated floating fraction Im methods, and adsorption methods as physical or chemical treatment methods.

Furthermore, in the treatment of oil-containing wastewater such as petroleum-based wastewater, the activated sludge method is often applied as a biological treatment method.

[Problem that the invention seeks to solve]

The above-mentioned physical and chemical treatment methods all require separation, recovery, and post-treatment of the oil, which has the drawback of requiring a large amount of cost.

However, the above-mentioned biological treatment method has the disadvantage that the rate of decomposition by microorganisms is slow and the equipment becomes large.

The present invention solves the above-mentioned drawbacks of the prior art, and provides a biological oil-containing wastewater treatment method that does not require post-treatment, has a high treatment speed, and can be efficiently treated with a small device. : The purpose is to provide.

[Means for solving problems]

As a result of various studies to eliminate the need for post-treatment, the present inventors focused on a microbial method that ultimately breaks down oil into harmless carbon dioxide and water, and completed a treatment method that can efficiently break down oil. did.

That is, the present invention entrapping and immobilizing microorganisms capable of degrading oil using a gel prepared by mixing a hydrophilic polymeric substance and a hydrophobic polymeric substance, and bringing the microbial entrapping immobilization gel and oil-containing wastewater into contact with each other to produce wastewater. This is a method for treating oil-containing wastewater, which is characterized by decomposing the oil contained therein.

Examples of the microorganisms having oil-decomposing ability (hereinafter referred to as oil-degrading microorganisms) used in the present invention include activated sludge collected from an aeration tank of an activated sludge treatment equipment for oil refinery wastewater and adapted to AM oil or the like. .

Hydrophilic polymeric substances used in the present invention include polyurethane, polyethylene glycol, polyacrylamide, polyvinyl alcohol, sodium alginate, etc., and hydrophobic polymeric substances include polypropylene glycol.

Note that the gel in the present invention may be any gel that can adjust its hydrophilicity and hydrophobicity, such as a photocurable resin or polyurethane.

In the present invention, the mixing ratio of the hydrophilic polymeric substance and the hydrophobic polymeric substance varies depending on the object to be treated, but is generally selected within the range of 1/10 to 10/1 in terms of volume ratio. is preferred.

If there are too many hydrophilic substances, oil uptake will be poor,
On the other hand, if there are too many hydrophobic substances, the amount of microorganisms retained will be reduced and decomposition will be delayed.

In addition, in the present invention, the amount of the above-mentioned oil-degrading microorganisms to be comprehensively immobilized on the gel prepared by mixing all the above-mentioned hydrophilic and hydrophobic polymeric substances is 1 to 100 f (dry microorganism amount) per gel 1. It is preferable. This is because if the amount of microorganisms is too large, the gel will become weak, and if the amount of microorganisms is too small, the reaction rate will be slow.

The gel containing the oil-degrading microorganisms is preferably used at a volume ratio of 10 to 50% of the oil-containing wastewater to be treated. This is because if the amount is smaller than this, the processing speed will be slow, and if the amount is larger than this, the fluidity will be poor and the reaction will be difficult to proceed.

[Effect]

In order to speed up the decomposition rate, the present inventors immobilized oil-degrading microorganisms in a reaction tank using polyacrylamide, polyvinyl alcohol, sodium alginate, etc. to maintain a high concentration of the oil-degrading microorganisms, and as a result, the processing capacity was reduced to a certain extent. improved, but not significantly. The reason for this is that because these gels are hydrophilic, it is difficult for oil to diffuse into the gel, and it is difficult for oil to come into contact with microorganisms within the gel. −, it is thought that it did not happen.

Therefore, in the present invention, immobilization was performed using a mixture of these hydrophilic gels and hydrophobic gels, and as a result, the processing capacity was significantly improved. Hydrophobic gel has lipophilic properties,
This is because by using this in combination with a hydrophilic gel, the oil is easily incorporated into the gel, and the oil comes into efficient contact with oil-degrading microorganisms and is decomposed.

〔Example〕

t Creation of immobilized gel As a hydrophilic gel, a photocurable resin having a polyethylene glycol main chain and photocurable ethylenically unsaturated groups at both ends [KNT-20003 manufactured by Kansai Paint ■] was used, and a hydrophobic gel was used. A photocurable resin having a polypropylene glycol main chain and photocurable ethylenically unsaturated groups at both ends [IITP-2 manufactured by Kansai Paint ■] is used as a thermoplastic gel.
000] was used.

A suspension of activated sludge collected from an aeration tank of an activated sludge treatment equipment for oil refinery wastewater was used as the oil-degrading microorganism to be entrappingly immobilized in the gel as follows. That is, this activated sludge is added to the culture solution having the composition shown in Table 1 by about 5.5%.
The mixture adjusted to a concentration of o o o ppm was placed in a 500 d capacity Sakaro flask for 400 d, and cultured at 30° C. for about 1 week. After confirming that the oil content had been decomposed, the supernatant water was discarded, and shaking culture was performed again using a new culture solution shown in Table 1. This culture was repeated four times and the product was used as oil-degrading activated sludge for testing.

Table-1 The gel was prepared as follows.

Add the above hydrophilic T-2000 to 10 volume fjt part,
After mixing 10 parts by volume of the above hydrophobic ENTP-2000 and α3 parts by volume of a photopolymerization initiator [S agent manufactured by Kansai Paint ■], 4 parts by volume of the above oil-degrading microorganism suspension were added. Pour the mixture into a spacer with a thickness of about 1 inch set on a propylene film, cover the propylene film on top, place a glass plate over the film to make it evenly thick, and expose it to light from above and below for 3 to 5 minutes. Gelation was performed by irradiation. This gelled sheet was cut with a razor into 1-2 m squares and used.

For comparison, gels prepared using hydrophilic resin and hydrophobic resin were also used. That is, the hydrophilic gel was prepared by mixing 10 parts by volume of the above ENT-2000, 0.1 part by volume of the above photopolymerization initiator, and zO part by volume of the above microorganism suspension, and the hydrophobic gel was prepared by mixing the above KN.
The above photopolymerization initiator α was added to 10 parts by volume of TP-,2000.
All 2 volumes.

A mixture of 2 parts by volume of the above microorganism suspension was photocured in the same manner as above and cut into 1 to 2 square pieces.

2 Results α12/L shown in Table 1 in a 500-capacity Sakalo flask
Add 300 ml of culture solution containing oil content (heavy oil A) fr: 1
~2■ Oil-degrading microorganism immobilization gel cut into cubes 1100?
After adding % Shaking culture at 30℃ (1 sor, p, m
) has started.

The results are shown in FIG.

These results show that when 100% hydrophobic gel is used, oil is taken up well, but microorganisms are less active, and when 100% hydrophilic gel is used
In this case, oil uptake is poor, and the method of the present invention, which uses a gel containing equal amounts of hydrophobic and hydrophilic gels, shows that oil uptake is good and microbial activity is active.

〔Effect of the invention〕

The following effects can be achieved by treating oil-containing wastewater, which is problematic due to environmental pollution, through the action of microorganisms entrapped and immobilized in a hydrophilic and hydrophobic polymer gel.

■ The processing speed of oil-containing wastewater becomes faster and the equipment can be made more compact.

■ Since microorganisms that have been entrapped and fixed in a gel are used, the microorganisms do not leak out from the reaction tank, and stable operation is possible even if the residence time is shortened.

■ It can be decomposed into harmless carbon dioxide gas and water, so no post-treatment is required.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the state of oil decomposition when various immobilized gels are used. Sub-Agents 1) Meifuku Agent Ryo Hagiwara − Sub-Agent Atsuo Anzai

Claims (1)

[Claims] A gel prepared by mixing a hydrophilic polymer substance and a hydrophobic polymer substance entraps microorganisms capable of degrading oil, and the microorganism entrapment gel and oil-containing wastewater are brought into contact to decompose the oil in the wastewater. A method for treating oil-containing wastewater.